Effects of hyperbaric oxygen combined cabin ventilator on critically ill patients with liberation difficulty after tracheostomy

BACKGROUND

Critically ill patients undergoing liberation often encounter various physiological and clinical complexities and challenges. However, whether the combination of hyperbaric oxygen and in-cabin ventilator therapy could offer a comprehensive approach that may simultaneously address respiratory and potentially improve outcomes in this challenging patient population remain unclear.

METHODS

This retrospective study involved 148 patients experiencing difficulty in liberation after tracheotomy. Inclusion criteria comprised ongoing mechanical ventilation need, lung inflammation on computed tomography (CT) scans, and Glasgow Coma Scale (GCS) scores of ≤ 9. Exclusion criteria excluded patients with active bleeding, untreated pneumothorax, cerebrospinal fluid leakage, and a heart rate below 50 beats per minute. Following exclusions, 111 cases were treated with hyperbaric oxygen combined cabin ventilator, of which 72 cases were successfully liberated (SL group) and 28 cases (NSL group) were not successfully liberated. The hyperbaric oxygen chamber group received pressurization to 0.20 MPa (2.0 ATA) for 20 min, followed by 60 min of ventilator oxygen inhalation. Successful liberation was determined by a strict process, including subjective and objective criteria, with a prolonged spontaneous breathing trial. GCS assessments were conducted to evaluate consciousness levels, with scores categorized as normal, mildly impaired, moderately impaired, or severely impaired.

RESULTS

Patients who underwent treatment exhibited improved GCS, blood gas indicators, and cardiac function indexes. The improvement of GCS, partial pressure of oxygen (PaO2), oxygen saturation of blood (SaO2), oxygenation index (OI) in the SL group was significantly higher than that of the NSL group. However, there was no significant difference in the improvement of left ventricular ejection fraction (LVEF), left ventricular end-systolic volume (LVESV), left ventricular end-diastolic volume (LVEDV), and stroke volume (SV) between the SL group and the NSL group after treatment.

CONCLUSIONS

Hyperbaric oxygen combined with in-cabin ventilator therapy effectively enhances respiratory function, cardiopulmonary function, and various indicators of critically ill patients with liberation difficulty after tracheostomy.

Validation of an alternative technique for RQ estimation in anesthetized pigs

BACKGROUND

Respiratory quotient (RQ) is an important variable when assessing metabolic status in intensive care patients. However, analysis of RQ requires cumbersome technical equipment. The aim of the current study was to examine a simplified blood gas-based method of RQ assessment, using Douglas bag measurement of RQ (Douglas-RQ) as reference in a laboratory porcine model under metabolic steady state. In addition, we aimed at establishing reference values for RQ in the same population, thereby generating data to facilitate further research.

METHODS

RQ was measured in 11 mechanically ventilated pigs under metabolic steady state using Douglas-RQ and CO-oximetry blood gas analysis of pulmonary artery and systemic carbon dioxide and oxygen content. The CO-oximetry data were used to calculate RQ (blood gas RQ). Paired recordings with both methods were made once in the morning and once in the afternoon and values obtained were analyzed for potential significant differences.

RESULTS

The average Douglas-RQ, for all data points over the whole day, was 0.97 (95%CI 0.95-0.99). The corresponding blood gas RQ was 0.95 (95%CI 0.87-1.02). There was no statistically significant difference in RQ values obtained using Douglas-RQ or blood gas RQ for all data over the whole day (P = 0.43). Bias was - 0.02 (95% limits of agreement ± 0.3). Douglas-RQ decreased during the day 1.00 (95%CI 0.97-1.03) vs 0.95 (95%CI 0.92-0.98) P < 0.001, whereas the decrease was not significant for blood gas RQ 1.02 (95%CI 0.89-1.16 vs 0.87 (0.80-0.94) P = 0.11.

CONCLUSION

RQ values obtained with blood gas analysis did not differ statistically, compared to gold standard Douglas bag RQ measurement, showing low bias but relatively large limits of agreement, when analyzed for the whole day. This indicates that a simplified blood gas-based method for RQ estimations may be used as an alternative to gold standard expired gas analysis on a group level, even if individual values may differ. In addition, RQ estimated with Douglas bag analysis of exhaled air, was 0.97 in anesthetized non-fasted pigs and decreased during prolonged anesthesia.

Prehospital blood gas analyses in acute patients treated by a ground-based physician-manned emergency unit: a cohort study

BACKGROUND

The prehospital patients treated by ambulances and mobile emergency care units (MECU) are potentially critically ill or injured. Knowing the risks of serious outcomes in these patients is important for guiding their treatment. Some settings allow for prehospital arterial blood gas analyses. This study aimed to assess the outcomes of prehospital patients in relation to their prehospitally measured lactate, pH, and CO2 levels. The primary outcome was 7-day mortality.

METHODS

This register-based cohort study included patients with one or more prehospital blood gas analyses during their prehospital treatment by a physician-manned MECU, from January 2015 to December 2018. The blood samples were analyzed on an ABL90 Flex analyzer. Absolute values with percentages and odds ratios (OR) with 95% confidence intervals (CI) were calculated for the primary and secondary outcomes within prespecified subgroups.

RESULTS

The study included 745 patients, with an overall 7-day mortality rate of 20.0%.

LACTATE LEVEL

The 7-day mortality rates were 11.5% in patients with normal lactate levels (< 2.0 mmol/L), 14.4% with intermediate lactate levels (2.0-3.9 mmol/L), and 33.0% with high lactate levels (≥ 4.0 mmol/L). This corresponded to an OR of 1.30 (95% CI: 0.75-2.24) in the intermediate lactate group (2.0-3.9 mmol/L) and an OR of 3.77 (95% CI: 2.44-5.85) in the high lactate group (≥ 4.0 mmol/L), compared to the reference group with normal lactate.

PH LEVEL

The ORs of 7-day mortality rates were 4.82 (95% CI: 3.00-7.75) in patients with blood pH of < 7.35 and 1.33 (95% CI: 0.65-2.72) in patients with blood pH > 7.45, compared to the reference group with normal pH (7.35-7.45). CO2 LEVEL : The ORs of 7-day mortality rates were 2.54 (95% CI: 1.45-4.46) in patients with blood CO2 of < 4.3 kPa and 2.62 (95% CI: 1.70-4.03) in patients with blood CO2 > 6.0 kPa, compared to the reference group with normal CO2 (4.3-6.0 kPa).

CONCLUSIONS

This study found a strong correlation between increasing 7-day mortality rates and high blood lactate levels, low levels of pH, and abnormal CO2 blood levels, in prehospital patients undergoing prehospital blood analysis.

Agreement of pCO2 in venous to arterial blood gas conversion models in undifferentiated emergency patients

BACKGROUND

Venous blood gas sampling has replaced arterial sampling in many critically ill patients, though interpretation of venous pCO2 still remains a challenge. Lemoël et al., Farkas and Zeserson et al. have proposed models to estimate arterial pCO2 based on venous pCO2. Our objective was to externally validate these models with a new dataset. This was a prospective cross-sectional study of consecutive adult patients with a clinical indication for blood gas analysis in an academic emergency department in Sweden. Agreement of pairs was reported as mean difference with limits of agreement (LoA). Vital signs and lead times were recorded.

RESULTS

Two hundred and fifty blood gas pairs were collected consecutively between October 2021 and April 2022, 243 valid pairs were used in the final analysis [mean age 72.8 years (SD 17.8), 47% females]. Respiratory distress was the most common clinical indication (84% of all cases). The model of Farkas showed the best metrics with a mean difference between estimated and arterial pCO2 of - 0.11 mmHg (95% LoA - 6.86, + 6.63). For Lemoël the difference was 2.57 mmHg (95% LoA - 5.65, + 10.8), Zeserson 2.55 mmHg (95% LoA - 7.43, + 12.53). All three models showed a decrease in precision in patients with ongoing supplemental oxygen therapy.

CONCLUSION

Arterial pCO2 may be accurately estimated in most patients based on venous blood gas samples. Additional consideration is required in patients with hypo- or hypercapnia or oxygen therapy. Thus, conversion of venous pCO2 may be considered as an alternative to arterial blood gas sampling with the model of Farkas being the most accurate.

Respiratory Acid-Base Disorders

Respiratory acid-base disorders are often not thought of as frequently as their metabolic cousins, which occur more frequently in the emergency department. Although most respiratory and acid-base disturbances are driven by lung pathology, central nervous system and other organ systems can and do play a role as well. Although managing the airway and appropriate mechanical ventilation may be necessary, it is akin to placing a band-aid on a large wound. It is crucial for the emergency clinician to discover the etiology of the disturbance as management depends on treating the underlying etiology to prevent worsening acid-base status.

Pilot testing the impact of an aerobic exercise plus rehabilitation training on respiratory function in older adults with COPD

Chronic obstructive pulmonary disease (COPD) is a chronic intractable lung disease. To investigate the therapeutic effect, older adult patients were subjected to aerobic exercise and respiratory rehabilitation (diaphragmatic breathing) for six months. At the end of six-month intervention, forced expiratory volume in one second (FEV1), forced vital capacity (FVC), 6-minute walking distance (6 MWD), and patient activation measure scores increased; St. George's respiratory questionnaire scores and disease impact score decreased; and PaCO₂ and PaO₂ were significantly improved in both groups, particularly in the experimental group. In addition, FEV1, FEV1/FVC, 6 MWD, blood gas levels, quality of life, and self-care ability in the experimental group were significantly improved compared with those in the control group, and the improvements were significantly greater in male, younger, and less diseased patients. Our study demonstrated that aerobic exercise combined with diaphragmatic breathing significantly improves respiratory function and quality of life in older adult patients.

Improving the Clinical Interpretation of Transcutaneous Carbon Dioxide and Oxygen Measurements in the Neonatal Intensive Care Unit

INTRODUCTION

Transcutaneous blood gas monitoring allows for continuous non-invasive evaluation of carbon dioxide and oxygen levels. Its use is limited as its accuracy is dependent on several factors. We aimed to identify the most influential factors to increase usability and aid in the interpretation of transcutaneous blood gas monitoring.

METHODS

In this retrospective cohort study, transcutaneous blood gas measurements were paired to arterial blood gas withdrawals in neonates admitted to the neonatal intensive care unit. The effects of patient-related, microcirculatory, macrocirculatory, respiratory, and sensor-related factors on the difference between transcutaneously and arterially measured carbon dioxide and oxygen values (ΔPCO2 and ΔPO2) were evaluated using marginal models.

RESULTS

A total of 1,578 measurement pairs from 204 infants with a median [interquartile range] gestational age of 273/7 [261/7-313/7] weeks were included. ΔPCO2 was significantly associated with the postnatal age, arterial systolic blood pressure, body temperature, arterial partial pressure of oxygen (PaO2), and sensor temperature. ΔPO2 was, with the exception of PaO2, additionally associated with gestational age, birth weight Z-score, heating power, arterial partial pressure of carbon dioxide, and interactions between sepsis and body temperature and sepsis and the fraction of inspired oxygen.

CONCLUSION

The reliability of transcutaneous blood gas measurements is affected by several clinical factors. Caution is recommended when interpreting transcutaneous blood gas values with an increasing postnatal age due to skin maturation, lower arterial systolic blood pressures, and for transcutaneously measured oxygen values in the case of critical illness.

Expiratory high-frequency percussive ventilation: a novel concept for improving gas exchange

Background

Although high-frequency percussive ventilation (HFPV) improves gas exchange, concerns remain about tissue overdistension caused by the oscillations and consequent lung damage. We compared a modified percussive ventilation modality created by superimposing high-frequency oscillations to the conventional ventilation waveform during expiration only (eHFPV) with conventional mechanical ventilation (CMV) and standard HFPV.

Methods

Hypoxia and hypercapnia were induced by decreasing the frequency of CMV in New Zealand White rabbits (n = 10). Following steady-state CMV periods, percussive modalities with oscillations randomly introduced to the entire breathing cycle (HFPV) or to the expiratory phase alone (eHFPV) with varying amplitudes (2 or 4 cmH₂O) and frequencies were used (5 or 10 Hz). The arterial partial pressures of oxygen (PaO₂) and carbon dioxide (PaCO₂) were determined. Volumetric capnography was used to evaluate the ventilation dead space fraction, phase 2 slope, and minute elimination of CO₂. Respiratory mechanics were characterized by forced oscillations.

Results

The use of eHFPV with 5 Hz superimposed oscillation frequency and an amplitude of 4 cmH₂O enhanced gas exchange similar to those observed after HFPV. These improvements in PaO₂ (47.3 ± 5.5 vs. 58.6 ± 7.2 mmHg) and PaCO₂ (54.7 ± 2.3 vs. 50.1 ± 2.9 mmHg) were associated with lower ventilation dead space and capnogram phase 2 slope, as well as enhanced minute CO₂ elimination without altering respiratory mechanics.

Conclusions

These findings demonstrated improved gas exchange using eHFPV as a novel mechanical ventilation modality that combines the benefits of conventional and small-amplitude high-frequency oscillatory ventilation, owing to improved longitudinal gas transport rather than increased lung surface area available for gas exchange.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12931-022-02215-2.

Acid base and blood gas analysis in term neonates immediately after birth with uncomplicated neonatal transition

BACKGROUND

Acid base and blood gas measurements provide essential information, especially in critically ill neonates. After birth, rapidly changing physiology and difficulty to obtain blood samples represent unique challenges.

OBJECTIVES

The aim of the present study was to establish normal values of capillary acid base and blood gas analysis immediately after birth in term neonates after uncomplicated neonatal transition.

METHOD

This is a post-hoc-analysis of ancillary outcome parameter of a prospective observational study in term neonates immediately after caesarean section. Neonates were included after immediate neonatal transition without need of medical support and a capillary blood sample was taken by a heel-stick within 15-20 minutes after birth.

RESULT

One hundred thirty-two term neonates were included with mean (SD) gestational age of 38.7 ± 0.7 weeks. The blood was drawn mean (SD) 16 ± 1.7 minutes after birth. The mean (SD) values of the analyses were: pH 7.30 ± 0.04, pCO₂ 52.6 ± 6.4, base excess - 0.9 ± 1.7 and bicarbonate 24.8 ± 1.6.

CONCLUSION

This is the first study describing acid base and blood gas analyses in term neonates immediately after birth with uncomplicated neonatal transition.

Discontinuous gas exchange in Madagascan hissing cockroaches is not a consequence of hysteresis around a fixed PCO2 threshold

It has been hypothesised that insects display discontinuous gas-exchange cycles (DGCs) due to hysteresis in their ventilatory control, where CO2-sensitive respiratory chemoreceptors respond to changes in hemolymph PCO2 only after some delay. If correct, DGCs would be a manifestation of an unstable feedback loop between chemoreceptors and ventilation causing PCO2 to oscillate around some fixed threshold value: PCO2 above this ventilatory threshold would stimulate excessive hyperventilation, driving PCO2 below the threshold and causing a subsequent apnoea. This hypothesis was tested by implanting micro-optodes into the hemocoel of Madagascar hissing cockroaches and measuring hemolymph PO2 and PCO2 simultaneously during continuous and discontinuous gas exchange. The mean hemolymph PCO2 of 1.9 kPa measured during continuous gas exchange was assumed to represent the threshold level stimulating ventilation, and this was compared with PCO2 levels recorded during DGCs elicited by decapitation. Cockroaches were also exposed to hypoxic (PO2 10 kPa) and hypercapnic (PCO2 2 kPa) gas mixtures to manipulate hemolymph PO2 and PCO2. Decapitated cockroaches maintained DGCs even when their hemolymph PCO2 was forced above or below the putative ∼2 kPa ventilation threshold, demonstrating that the characteristic oscillation between apnoea and gas exchange is not driven by a lag between changing hemolymph PCO2 and a PCO2 chemoreceptor with a fixed ventilatory threshold. However, it was observed that the gas exchange periods within the DGC were altered to enhance O2 uptake and CO2 release during hypoxia and hypercapnia exposure. This indicates that while respiratory chemoreceptors do modulate ventilatory activity in response to hemolymph gas levels, their role in initiating or terminating the gas exchange periods within the DGC remains unclear.

Evaluation of homeothermy, acid-base and electrolytic balance of black goats and ewes in an equatorial semi-arid environment

The aim of this study was to investigate the influence of environmental conditions and species on thermoregulatory responses, acid-base and electrolyte balance of black goats and ewes in an equatorial semi-arid environment. Ten Canindé goats and seven Morada Nova ewes with black coat color, all multiparous, aged between 2 and 3 years, non-lactating, non-pregnant, and body weight (B_W) of 22.84 ± 4.17 kg for goats and 22.60 ± 3.18 kg for ewes were used in this study. Air temperature (A_T) and relative humidity (R_H) were measured. Respiratory rate (R_R), Rectal temperature (R_T), sweating rate (S_R), hydrogen potential (pH), partial pressure of carbon dioxide (PCO₂), venous oxygen pressure (PO₂), bicarbonate (HCO₃), base excess (BE), total carbon dioxide concentration (TCO₂), venous oxygen saturation (SO₂), sodium (Na⁺) and potassium (K⁺) were recorded. Animal species (caprine and ovine) and environmental conditions (Thermoneutral condition, T_C and Heat condition, H_C) were considered as fixed effects. Univariate and multivariate analysis techniques were used. Differences were observed between the two environmental conditions. Significant changes in all thermoregulatory responses for goats and ewes were observed according to the environmental condition effect. The general means of the species showed that only S_R was high in ewes (P < 0.05), following a reverse change when compared to goat S_R. For the environmental condition effect, only the blood pH of goats did not change under H_C (P < 0.05), while the B_E and TCO₂ did not change for ewes. The general means of PCO₂, HCO₃, BE, TCO₂ and SO₂ were higher in ewes compared to goats. For electrolytic balance, Na ⁺ demonstrated elevations in H_C. Brazilian black goats and ewes raised in an equatorial semi-arid environment tend to have particular homeothermy, acid-base and electrolytic balance which mostly depend on the environmental conditions they are raised. The results support the changes in physiological mechanisms between black goats and ewes; however, both are locally adapted.

Clinical Validation of a Novel Quality Management System for Blood Gas, Electrolytes, Metabolites, and CO-Oximetry

BACKGROUND

Quality management of point-of-care (POC) blood gas testing focuses on verifying instrument accuracy and precision, in addition to performing daily quality control (QC) checks every 8 h and with each patient test (unless internal calibration is verified every 30 min). At the POC, a risk-based approach is suitable to address both systemic and transient sample-specific errors that may negatively impact patient care.

METHODS

We evaluated the performance of the GEM® Premier™ 5000 with next generation Intelligent Quality Management 2 (iQM®2) (Instrumentation Laboratory, Bedford, MA), from the analysis of approximately 84,000 patient samples across 4 sites. Continuous iQM2 was compared to intermittent liquid QC, either manual or automated, at 2 sites. Analysis of error flags for patient samples and statistical characteristics of QC processes, including method sigma and average detection time (ADT) for an error, were examined.

RESULTS

ADT was approximately 2 min with iQM2 and varied from hours to days with intermittent QC. iQM2 Process Control Solutions (PCS) precision was similar or better (>6 sigma for all analytes) than manual (sigma 3.0 for pO2) or automated internal QC (sigma 1.3 for tHb and sigma 3.3 for pO2). In addition, iQM2 detected errors in ∼1.4% of samples, providing an additional safeguard against reporting erroneous results.

CONCLUSIONS

The findings in this study demonstrate excellent performance of the GEM Premier 5000 with iQM2 including >6 sigma precision for all analytes and faster error detection times. These benefits address risk in different phases of testing that are not easily detected by intermittent performance of liquid QC (manual or automated).

10% Lidocaine spray as a local anesthetic in blood gas sampling: A randomized, double-blind, placebo-controlled study

AIM

Radial artery blood gas sampling is a very common procedure undertaken in the emergency department to evaluate respiratory and metabolic parameters. This intervention causes both anxiety and pain for the patient. Therefore, the current study aimed to examine the analgesic efficacy of lidocaine spray compared to a placebo during radial artery blood gas sampling.

METHODS

This study was conducted in the emergency department of a tertiary hospital with a randomized, double-blind, placebo-controlled design. A total of 144 patients were randomly divided into two groups: One group (n = 72) received 10% lidocaine spray and the other (n = 72) was the placebo group. The analgesic efficacy of the 10% lidocaine spray was compared with the placebo group using the Visual Analog Scale (VAS).

RESULTS

In the evaluation of the analgesic efficacy of the 10% lidocaine spray, the VAS score was 1.5 [interquartile range (IQR): 2.0] for the lidocaine group and 5 (IQR: 2.0) for the placebo group. The role of lidocaine spray in reducing pain was statistically significant compared to the placebo (p = 0.000).

CONCLUSION

In blood gas sampling, 10% lidocaine spray has analgesic efficacy. Therefore, we recommend the use of lidocaine spray while performing arterial blood gas sampling in emergency departments.

HEMATOLOGIC AND BIOCHEMICAL VALUES OF THE JUVENILE EASTERN GRAY SQUIRREL (SCIURUS CAROLINENSIS)

Venous blood samples were collected from 64 apparently healthy juvenile Eastern gray squirrels (Sciurus carolinensis) after sedation with midazolam at the Wildlife Center of Texas located in Houston, Texas, during 2012. Blood gas (pH, PCO2, PO2, base excess, bicarbonate, oxygen saturation), electrolyte (sodium, potassium), biochemical (total CO2, ionized calcium, glucose), and hematologic parameters (hematocrit, hemoglobin, complete blood count) were determined using the i-STAT point-of-care analyzer. Sex did not affect any analyte. All squirrels recovered uneventfully and were successfully rehabilitated and released. Most values were as expected based on comparison to other young rodent species. These analyte data for healthy juvenile Eastern gray squirrels may be useful in assessment of Eastern gray squirrel population health and management and treatment of individual squirrels presented in need of medical care.

Ammonia excretion and blood gas variation in naked carp (Gymnocypris przewalskii) exposed to acute hypoxia and high alkalinity

Naked carp (Gymnocypris przewalskii), endemic to the saline-alkaline Lake Qinghai, have the capacity to tolerate combined hypoxia and high alkalinity. This study evaluated the effect of the interaction between carbonate alkalinity and hypoxia on ammonia excretion and blood gas variation in naked carp. Naked carp were subjected to normoxic, hypoxic and reoxygenation phases at two different carbonate alkalinity levels (CA0 = 0 mmol/L; CA32 = 32 mmol/L) for 4 days. The ammonia excretion rate (J_Amm) of the CA0 group rapidly decreased under hypoxia and recovered under normoxia for four consecutive days. The J_Amm under CA32 also decreased under hypoxia and recovered to its previous level in the first 2 days. However, the J_Amm under CA32 was lower than that under CA0. The blood pO₂, sO₂ of CA0 and CA32 group was significantly reduced under hypoxia, after which both groups recovered. Blood pCO₂ of the CA32 group was lower than CA0 throughout the experiment. There were no changes in haematocrit of the naked carp exposed to carbonate alkalinity and hypoxia. The alkaline water increased the pH of the blood and contributed to increased haemoglobin O₂ affinity. Overall, the present findings reveal that naked carp is a tolerant species that can maintain main ionic homeostasis under severe alkalinity and hypoxia. The high alkaline water is beneficial for naked carp to adapt to hypoxic environment.

Effects of different plasma expanders on rats subjected to severe acute normovolemic hemodilution

BACKGROUND

Plasma expanders are widely used for acute normovolemic hemodilution (ANH). However, existing studies have not focused on large-volume infusion with colloidal plasma expanders, and there is a lack of studies that compare the effects of different plasma expanders.

METHODS

The viscosity, hydrodynamic radius (R_h) and colloid osmotic pressure (COP) of plasma expanders were determined by a cone-plate viscometer, Zetasizer and cut-off membrane, respectively. Sixty male rats were randomized into five groups with Gelofusine (Gel), Hydroxyethyl Starch 200/0.5 (HES200), Hydroxyethyl Starch 130/0.4 (HES130), Hydroxyethyl Starch 40 (HES40), and Dextran40 (Dex40), with 12 rats used in each group to build the ANH model. ANH was performed by the withdrawal of blood and simultaneous infusion of plasma expanders. Acid-base, lactate, blood gas and physiological parameters were detected.

RESULTS

Gel had a lower intrinsic viscosity than HES200 and HES130 (P < 0.01), but at a low shear rate in a mixture of colloids, red cells and plasma, Gel had a higher viscosity (P < 0.05 or P < 0.01, respectively). For hydroxyethyl starch plasma expanders, the COP at a certain concentration decreases from 11.1 mmHg to 6.1 mmHg with the increase of R_h from 10.7 nm to 20.2 nm. A severe ANH model, with the hematocrit of 40% of the baseline level, was established and accompanied by disturbances in acid-base, lactate and blood gas parameters. At the end of ANH and 60 min afterward, the Dex40 group showed a worse outcome in maintaining the acid-base balance and systemic oxygenation compared to the other groups. The systolic blood pressure (SBP), diastolic blood pressure (DBP), and mean arterial pressure (MAP) decreased significantly in all groups at the end of ANH. The DBP and MAP in the Dex40 group further decreased 60 min after the end of ANH. During the process of ANH, the Dex40 group showed a drop and recovery in SBP, DBP and MAP. The DBP and MAP in the HES200 group were significantly higher than those in the other groups at some time points (P < 0.05 or P < 0.01).

CONCLUSION

Gel had a low intrinsic viscosity but may increase the whole blood viscosity at low shear rates. R_h and COP showed a strong correlation among hydroxyethyl starch plasma expanders. Dex40 showed a worse outcome in maintaining the acid-base balance and systemic oxygenation compared to the other plasma expanders. During the process of ANH, Dex40 displayed a V-shaped recovery pattern for blood pressure, and HES200 had the advantage in sustaining the DBP and MAP at some time points.

Takuo Aoyagi-a Tribute to the Brain Behind Pulse Oximetry

A tribute is being paid to the Dr. Takuo Aoyagi who invented pulse oximetry to measure the oxygen saturation in the blood in 1974. The importance of pulse oximetry is felt more in this coronavirus pandemic. Takuo Aoyagi expired at Tokyo on 18 April 2020.

THE EFFECT OF ANESTHETIC TIME AND CONCENTRATION ON BLOOD GASES, ACID-BASE STATUS, AND ELECTROLYTES IN KOI (CYPRINUS CARPIO) ANESTHETIZED WITH BUFFERED TRICAINE METHANESULFONATE (MS-222)

Anesthesia is commonly employed in aquatic medicine to facilitate physical exams, diagnostics, and surgical interventions. Tricaine methanesulfonate (MS-222) is the most commonly used anesthetic for fish and is currently the only anesthetic approved by the US Food and Drug Administration Center for Veterinary Medicine for food-producing fish. Despite the frequency of anesthetic procedures in fish, anesthetic monitoring remains rudimentary in many facilities. This study evaluated the impact on blood gases, acid-base balance, and electrolytes in koi (Cyprinus carpio) anesthetized at concentrations of 100 mg/L and 150 mg/L MS-222. Blood samples from 25 fish per treatment were collected at 5 and 20 min of anesthetic immersion. Forty-nine of 50 fish recovered uneventfully from anesthesia; one fish did not recover and was euthanatized. Results showed significant increases in partial pressure of carbon dioxide (pCO₂) (P = 0.006) and hyperglycemia (P = <0.0001) with increasing anesthetic concentration and time under anesthesia and a significant decrease in partial pressure of oxygen (pO₂) with increased anesthetic time (P = 0.021). There were several electrolyte changes observed with both increasing anesthetic time and concentration. All electrolytes except potassium remained within published reference ranges for koi, while potassium showed a significant decrease in concentration associated with anesthetic time and concentration. The results of this study indicate that MS-222 at 100 mg/L and 150 mg/L represent safe anesthetic concentrations for koi undergoing minimally invasive diagnostics; however, koi anesthetized with MS-222 at a concentration of 150 mg/L experienced more significant changes in blood gases, acid-base balance, and electrolyte concentrations.

Evaluation of time courses of agreement between minutely obtained transcutaneous blood gas data and the gold standard arterial data from spontaneously breathing Asian adults, and various subgroup analyses

BACKGROUND

Usual clinical practice for arterial blood gas analysis (BGA) in conscious patients involves a one-time arterial puncture to be performed after a resting period of 20-30 min. The aim of this study was to evaluate the use of transcutaneous BGA for estimating this gold standard arterial BGA.

METHODS

Spontaneously breathing Asian adults (healthy volunteers and respiratory patients) were enrolled (n = 295). Transcutaneous PO₂ (PtcO₂) and PCO₂ (PtcCO₂) were monitored using a transcutaneous monitor (TCM4, Radiometer Medical AsP, Denmark) with sensors placed on the chest, forearm, earlobe or forehead. Transcutaneous BGA at 1-min intervals was compared with arterial BGA at 30 min. Reasonable steps to find severe hypercapnia with PaCO₂ > 50 mmHg were evaluated.

RESULTS

Sensors on the chest and forearm were equally preferred and used because of small biases (n = 272). The average PCO₂ bias was close to 0 mmHg at 4 min, and was almost constant (4-5 mmHg) with PtcCO₂ being higher than PaCO₂ at ≥8 min. The limit of agreement for PCO₂ narrowed over time: ± 13.6 mmHg at 4 min, ± 7.5 mmHg at 12-13 min, and ± 6.3 mmHg at 30 min. The limit of agreement for PO₂ also narrowed over time (± 23.1 mmHg at 30 min). Subgroup analyses showed that the PaCO₂ and PaO₂ levels, gender, and younger age significantly affected the biases. All hypercapnia subjects with PaCO₂ > 50 mmHg (n = 13) showed PtcCO₂ ≥ 50 mmHg for until 12 min.

CONCLUSIONS

Although PtcCO₂ is useful, it cannot completely replace PaCO₂ because PCO₂ occasionally showed large bias. On the other hand, the prediction of PaO₂ using PtcO₂ was unrealistic in Asian adults. PtcCO₂ ≥ 50 mmHg for until 12 min can be used as a screening tool for severe hypercapnia with PaCO₂ > 50 mmHg.

Are locally adapted goats able to recover homeothermy, acid-base and electrolyte equilibrium in a semi-arid region?

The objective of this study was to evaluate the thermoregulatory responses, acid-basic and electrolytic equilibrium of locally adapted goats under natural heat conditions in a semi-arid region. Ten (10) Canindé goats aged between 2 and 3 years, non-lactating, non-pregnant and having a body weight (B_W) of 22.90 ± 2.70 kg were used in this study. Air temperature (A_T) and relative humidity (R_H) were measured, and the radiant heat load (RHL) was subsequently calculated. Rectal temperature (R_T), respiratory rate (R_R), sweating rate (S_R) and heat shock (S) were recorded at 1-h intervals for 24 continuous hours. Hydrogen potential (pH), partial pressure of carbon dioxide (PCO₂), partial pressure of oxygen (PO₂), bicarbonate (HCO₃), base excess (BE), total carbon dioxide concentration (TCO₂), oxygen saturation (SO₂), sodium (Na⁺) and potassium (K⁺) were recorded at three moments during the day (5 a.m.; 1 p.m.; 6 p.m.). There were also significant differences between the means of hours of the day for A_T and R_H. R_R was the thermoregulatory response which most closely followed RHL, with important elevations in the periods between 10 a.m. to noon. It was observed that the goats activated their SR mechanism before R_R, more precisely between the hours of 9 a.m. and 1 p.m. The acid-base and electrolytic equilibrium for the goats which showed great association with the first components contributed the most to the total variation of the data. The most important variables in the adaptive profile of these animals in order of importance were: SO₂, PO₂, R_R, R_T, S_R, HCO₃, BE, TCO₂ and pH. An association between all variables grouped in each period was observed, where the thermoregulatory responses in the periods of 5 a.m. and 6 p.m. were closer than when compared to 1 p.m., showing a physiological return to the initial state. Therefore, the variation in thermoregulatory responses, acid-base and electrolytic equilibrium indicated that the goats have the ability to recover after a challenging environmental condition.

TRANSCUTANEOUS OXYGEN MONITORING IN LOUISIANA PINE SNAKES (PITUOPHIS RUTHVENI)

Hypoxic physiological states may occur during anesthetic events of snakes but accurate monitoring of oxygenation is challenging. Oxygenation levels of nine Louisiana pine snakes (Pituophis ruthveni) were assessed using transcutaneous regional oxygen saturation (rSO₂) at the level of the liver (rSO₂^Liver) and at the halfway point of the body (rSO₂^Half ). Reflectance pulse oximetry measured SpO₂, with a sensor overlying the heart. Values were compared with the venous partial pressure of oxygen (PvO₂). Measurements were taken during four phases, simulating an anesthetic event: phase 1, breathing room air; phase 2, while supplied with supplemental oxygen via face mask; phase 3, during ketamine and dexmedetomidine sedation; and phase 4, after receiving atipamezole. There were no significant changes in any oxygenation parameters between concurrent phases, but respiratory rate significantly decreased (P = 0.02) between phases 1 and 2. Strong positive associations were found between both rSO₂^Liver and rSO₂^Half when compared with PvO₂ irrespective of phase (r = 0.72, r = 0.63 respectively), but not with SpO₂ (r = 0.3). Strength of correlation varied with each phase but was uniformly strongest for rSO₂^Liver. The measurement of rSO₂ appears superior compared with traditional pulse oximetry for assessing oxygenation levels of snakes.

Lung function and blood gas abnormalities in patients with acromegaly

OBJECTIVE

Respiratory disorders are common complications of acromegaly patients. We conducted a large-scale survey in the patients with acromegaly and demonstrated the characteristics of their lung function and blood gas.

METHODS

A prospective cohort study was conducted with 115 patients with active acromegaly and 56 patients with nonfunctioning pituitary adenomas. All patients underwent clinical, biological, radiological, lung functional and blood gas assessments.

RESULTS

Acromegaly patients had a higher lung volume than those with nonfunctioning adenomas (forced vital capacity value (FVC) and FVC% predicted: p < 0.001). The small airway was less obstructive in acromegaly patients (higher FEV1% predicted, PEF% predicted, MEF75% predicted, MEF50% predicted, MEF25% predicted: p ≤ 0.001 for all analyses, FEV1/FVC: p = 0.151). The average partial pressure of carbon dioxide in acromegaly patients was higher (p < 0.001), but there was no significant difference in the average partial pressure of oxygen or oxygen saturation between the two groups (p > 0.05). In acromegaly patients, the average age of patients with small airway obstruction was higher than that of patients with normal lung function (p < 0.05), but no significant difference in GH or IGF-1 levels between the two groups were found (p > 0.05).

CONCLUSION

The acromegaly patients in this cohort had increased lung volume. However, there was no evidence demonstrating hypoxemia in acromegaly patients. The small airway was less obstructive in acromegaly patents. Small airway obstruction was observed in elderly patients with acromegaly.

Connecting two worlds: positive correlation between physicochemical approach with blood gases and pH in pediatric ICU setting

Objective

Physicochemical approach such as strong ion difference provides a novel concept in understanding and managing acid–base disturbance in patients. However, its application in pediatrics is limited. This study aimed to evaluate a correlation between the physicochemical approach and blood gas pH for acid–base determination in critically ill pediatric patients.

Results

A total of 130 pediatric patients were included, corresponding to 1338 paired measures for analyses. Of these, the metabolic subgroup (743 paired measures) was defined. Among physicochemical parameters, the effective strong ion difference showed the best correlation with the blood gas pH in the whole cohort (R = 0.398; p < 0.001) and the metabolic subgroup (R = 0.685; p < 0.001). Other physicochemical parameters (i.e., the simplified and the apparent strong ion difference, the strong ion gap, and the sodium chloride gap) and the traditional measures (standard base excess, lactate, chloride and bicarbonate) also showed varying degrees of correlation. This study revealed the positive correlation between physicochemical parameters and the blood gas pH, serving as a connecting dot for further investigations using physicochemical approach to evaluate acid–base disturbance in pediatric population.

Multilevel qualification of a large set of blood gas analyzers: Which performance goals?

BACKGROUND

Blood gas analyzers are frequently installed as point of care devices and thus allow rapid decision making. Few data are available regarding analytical performance of large sets of BGA. We aimed at evaluating 22 ABL 90 Flex Plus analyzers intended to be deployed. The evaluation was performed at the device level and at the entire set level to characterize the quality of measurements but also to ensure consistency across the devices deployed in the hospital.

METHODS

Imprecision and total error were assessed for pH, pCO2, pO2, sodium, potassium, ionized calcium, glucose, lactate and oximetry parameters. Imprecision at the hospital level including between device variability was also evaluated. One of the two analyzers used in the central laboratory was correlated with a GEM Premier 4000 and a Cobas b221 analyzers. Thereafter, we tested sequentially the 20 instruments intended to be deployed in care service in comparison with the reference device.

RESULTS

Heterogeneity of analytical performance across the different analyzers was low, allowing to consider the whole set as a unique analyzer. The total error was in line with performance goals. Analytical performance of the analyzers was found suitable for use in clinical practice.

CONCLUSIONS

Our study is an example of the qualification of a set of point and underscores 1)The need for a unified qualification scheme when multiple analyzers are deployed simultaneously 2) analytical performance goals compatible with clinical use and the state of the art for all parameters.

Impact of point-of-care creatinine monitoring on early detection of acute kidney injury in critical illness

PURPOSE

To assess the utility and accuracy of creatinine measurement using point-of-care (POC) blood gas analysis compared to standard laboratory assay and to assess the effectiveness of frequent creatinine monitoring using POC blood gas analysis with respect to early detection of acute kidney injury (AKI).

METHODS

We performed a single center retrospective observational study in 398 patients admitted to the intensive care unit. We investigated the clinical concordance of creatinine values measured by POC blood gas analysis (Cr-BG) compared to those measured by laboratory assay (Cr-lab). We compared the time to reach AKI diagnosis according to the KDIGO criteria using Cr-BG (KD-BG) to the standard criteria using Cr-lab (KD-lab).

RESULTS

Cr-BG correlated well with Cr-lab for day 1 (n = 375, R² = 0.98, p < 0.001) and during the whole study period (n = 1258, R² = 0.99, p < 0.001). The KD-BG measurement allowed the identification of 6.3% more patients (60.6%) as AKI than the KD-lab measurement. Approximately one-third of the patients were staged as AKI using the KD-BG measurement more than 6 h earlier than that using the KD-lab measurement.

CONCLUSIONS

The KDIGO criteria using POC blood gas analysis were clinically useful. Frequent creatinine monitoring using POC analysis can allow an earlier detection of AKI.

Delayed cord clamping does not affect umbilical cord blood gas analysis

BACKGROUND

Although delayed umbilical cord clamping has been shown to have significant benefits for both term and preterm infants, currently, data on its impact on blood gas analysis have been scant and conflicting.

METHODS

In a retrospective review, we compared the demographic characteristics and blood gas parameters of 114 delayed cord clamping (DCC-births between 45 and 90 s in length; 109 being for 60 s) versus 407 early cord clamping births (ECC-immediately after delivery) collected over a 1-year period. Intrapartum care and timing of cord clamping for individual cases were performed at the discretion of obstetricians. The differences were assessed for statistical and clinical significance.

RESULTS

The DCC group was found to have significantly higher mean Apgar scores at both 1 and 5 min (p < 0.05), as well as lower percentages of nulliparous births, cesarean-section deliveries, epidural anesthesia usage, and major pregnancy-related complications. No significant differences in maternal age, gestational age, neonate birthweight, sex, or in the presence of meconium at birth were observed. A higher umbilical artery pO₂ in the DCC group [21 (9) vs. 19 (10) mmHg, p < 0.05] was the only statistically significant difference found out of all the blood gas parameters analyzed.

CONCLUSIONS

In this study, infants selected for the DCC procedure were found to be overall lower risk than those delivered as per the standard ECC procedure. No clinically significant difference in any blood gas parameter was observed, and therefore, no adjustment to clinical reference intervals is needed for DCC blood gas samples taken after a 1-min delay period.

Venous blood gas in free-living eastern box turtles (Terrapene carolina carolina) and effects of physiologic, demographic and environmental factors

Sustainable wildlife populations depend on healthy individuals, and the approach to determine wellness of individuals is multifaceted. Blood gas analysis serves as a useful adjunctive diagnostic test for health assessment, but it is uncommonly applied to terrestrial reptiles. This study established reference intervals for venous blood gas panels in free-living eastern box turtles (Terrapene carolina carolina, N = 102) from Illinois and Tennessee, and modeled the effects of environmental and physiologic parameters on each blood gas analyte. Blood gas panels included pH, partial pressure of oxygen (pO₂), partial pressure of carbon dioxide (pCO₂), total carbon dioxide (TCO₂), bicarbonate (HCO₃^-), base excess (BE) and lactate. Candidate sets of general linear models were constructed for each blood gas analyte and ranked using an information-theoretic approach (AIC). Season, packed cell volume (PCV) and activity level were the most important predictors for all blood gas analytes (P < 0.05). Elevations in PCV were associated with increases in pCO₂ and lactate, and decreases in pH, pO₂, HCO₃^-, TCO₂ and BE. Turtles with quiet activity levels had lower pH and pO₂ and higher pCO₂ than bright individuals. pH, HCO₃^-, TCO₂ and BE were lowest in the summer, while pCO₂ and lactate were highest. Overall, blood pH was most acidic in quiet turtles with elevated PCVs during summer. Trends in the respiratory and metabolic components of the blood gas panel tended to be synergistic rather than antagonistic, demonstrating that either (1) mixed acid-base disturbances are common or (2) chelonian blood pH can reach extreme values prior to activation of compensatory mechanisms. This study shows that box turtle blood gas analytes depend on several physiologic and environmental parameters and the results serve as a baseline for future evaluation.

Utility of venous blood gases in severe sepsis and septic shock

Acid-base status is frequently assessed in severe sepsis and septic shock. Venous blood gas sampling is proposed as a less-invasive modality but lacks evidence within this population. The objective of this study was to evaluate the correlation and agreement between arterial blood gas (ABG), peripheral venous blood gas (pVBG), and central venous blood gas (cVBG) in severe sepsis and septic shock. We conducted a prospective, observational cohort study in subjects admitted to the medical intensive care unit. Simultaneous blood gas samples, including ABG, pVBG, and cVBG, were analyzed for correlation and agreement. Severity of illness scores revealed a mean (±SD) Sequential Organ Failure Assessment score of 7.9 ± 3.3, Simplified Acute Physiology II score of 49.3 ± 16.5, and a mortality rate of 11.9% in the intensive care unit and 16.4% in the hospital. We found a strong intraclass correlation (>0.85) for pH, partial pressure of carbon dioxide (pCO₂), bicarbonate, and base excess for ABG/pVBG, ABG/cVBG, and pVBG/cVBG comparisons. Agreement by the Bland-Altman method was found for pH (bias ± SD, 0.03 ± 0.04, 0.03 ± 0.02, and 0.00 ± 0.03) but not for pCO₂, partial pressure of oxygen, bicarbonate, base excess, and oxyhemoglobin saturation. In conclusion, adequate correlation and agreement between ABG/pVBG, ABG/cVBG, and pVBG/cVBG comparisons was found only for pH. The current level of evidence does not support the use of venous blood gas sampling in this setting.

Development and characterization of a point-of care rate-based transcutaneous respiratory status monitor

Blood gas measurements provide vital clinical information in critical care. The current "gold standard" for blood gas measurements involves obtaining blood samples, which can be painful and can lead to bleeding, thrombus formation, or infection. Mass transfer equilibrium-based transcutaneous blood gas monitors have been used since the 1970s, but they require heating the skin to ≥42 °C to speed up the transcutaneous gas diffusion. Thus, these devices have a potential risk for skin burns. Here we report a new generation of noninvasive device for respiratory status assessment. Instead of waiting for mass transfer equilibrium, the blood gas levels are monitored by measuring the transcutaneous diffusion rate, which is proportional to blood gas concentration. The startup time of this device is almost independent of skin temperature, so the measurement can be made at any body temperature. The test results show that this device can track the blood gas levels quickly even at normal body temperature.

Relocation of blood gas laboratory to the emergency department helps decrease lactic acid values

IMPORTANCE

Emergency Physicians often rely on Lactic Acid (LA) values to make important clinical decisions. Accuracy of LA values improve when blood gas analysis is performed in the emergency department (ED) as opposed to a satellite laboratory (SL).

OBJECTIVE

To investigate an association between blood gas laboratory location and accuracy of ED lactic acid samples.

METHODS

The study team evaluated lactic acid values from venous and arterial blood gas samples drawn between June 1, 2015 and September 30, 2016. The study was exempt from institutional review board approval. Samples were separated into two groups: those which were drawn prior to and after relocation of the blood gas laboratory to the ED. The data, including patient demographic characteristics, acute illness severity indices, and blood gas results were compared within and between each group using t-test for continuous variables and chi-square test for categorical variables. The primary outcome was the mean lactate value measured in the SL group in 2015 compared to the ED group in 2016. Potassium and creatinine values were measured between the two groups as secondary outcomes.

RESULTS

Of the 21,595 consecutive samples drawn, 10,363 samples were from the SL group and 11,232 from the ED group. The SL group included 5458 (52.7%) women; mean (SD) age was 61.8 (21.0). The ED group contained 5860 (52.2%) women; mean (SD) age was 61.7 (20.5). Mean Emergency Severity Index (ESI) were the same in each group at 2.31 and rates of Systemic Inflammatory Response Syndrome (SIRS) were also equivalent in each group at 22.2%. Significant differences were found between LA values in the SL group (mean 2.21mmol/L) and in the ED group (mean 1.99mmol/L) with a p value of <0.0001. There was a small statistical significance between the difference in potassium values in the SL group (mean 3.98meq/L) compared to the ED Group (mean 3.96meq/L) with a p value of 0.022. No significant difference was found between the creatinine values.

CONCLUSIONS AND RELEVANCE

These results suggest that mean lactate values decreased when measured in an ED blood gas laboratory and may provide more accurate LA results than blood gas samples analyzed at an SL blood gas laboratory within the same institution. Hospitals may consider moving blood gas laboratories to the ED to improve accuracy of one of the most important early blood markers used in the definition of sepsis and in the identification of the critically ill.

Association between oxygenation and ventilation indices with the time on invasive mechanical ventilation in infants

BACKGROUND

Invasive mechanical ventilation (IMV) is a common practice in pediatric intensive care unit (PICU). However, the role of oxygenation (OI) and ventilation (VI) indices regarding the time on IMV has not been fully understood.

BASIC PROCEDURES

The study was conducted with infants up to 24 months of age, hospitalized in PICU for two consecutive years. The values of ventilatory parameters, OI, VI, and blood gas of infants, collected in the first seven days in IMV, were associated with the time on IMV. IMV was classified into: short (≤seven days) and long time (>seven days). The comparison was made from the first to the seventh day. Alpha=0.05.

MAIN FINDINGS

Of 142 infants [mean age=7.51±6.33 months], 59 (41.5%) remained on IMV for a short time and 83 (58.5%) for a long time. Differences in PaO2 values were found on the second day, and PaO2/FiO2 ratio on the second, third and fourth days, with higher values in the short-term IMV. For FiO2 from the second to the fifth day; Pinsp from the first to the seventh day; PEEP from the second to the sixth day; mechanical respiratory frequency from the second to the seventh day, PaCO2 on the second day; Paw from the first to the seventh day, OI from the second to the sixth day, and VI from the first to the seventh day, the values were higher in the long-term IMV.

CONCLUSIONS

The OI and VI can be considered as potential predictors of long-term IMV, along with other markers obtained during the IMV.

Method validation of a set of 12 GEM® Premier™ 4000 blood gas analyzers for point-of-care testing in a university teaching hospital

Background

Blood gas analyzers are o0.ften integrated into point-of-care testing provisions. International standards (ISO 22870 and 15189) as adapted to French COFRAC regulations make accreditation of point-ofta-care testintag obligatory. We installed and assessed 12 GEM PREMIER 4000 analyzers for pH, pCO₂, pO₂, Na⁺, K⁺, Cl^-, Ca²⁺, lactate, hemoglobin and oxyhemoglobin (O₂Hb) at Clermont-Ferrand Hospital. These instruments were distributed across 11 care sites in the hospital.

Methods

Precision was studied at two control levels for each parameter. Comparisons between GEM analyzers were performed (on 30 samples) for pH, pCO₂, pO₂, Na⁺, K⁺, Cl^-, Ca²⁺, lactate, hemoglobin and O₂Hb; and between GEM analyzers and the central laboratory for Na⁺, K⁺, Cl^-, Ca²⁺ and hemoglobin (on 30–50 samples). Uncertainty in measurement (UM) was evaluated with an approach using reproducibility and accuracy data.

Results

The coefficients of variation (CVs) were in line with recommendations, except for the repeatability CV for pO₂. All CVs were below 4%. All comparisons complied with recommendations. Uncertainties of measurement were also validated.

Conclusion

Our results met standard requirements and the 12 analyzers were assessed as suitable for point-of-care testing in services of academic medical centers, as exemplified at Clermont-Ferrand hospital.

•

Complete method validation of 12 analyzers for POCT in a multisite hospital.

•

First published values of uncertainty in measurement very useful for pO2 and O₂Hb.

•

Comparison between GEM4000 and central lab analyzers for Na⁺, Cl^-, K⁺, lactate, Hb.

Long-term Treatment with Methylene Blue in a Dog with Hereditary Methemoglobinemia Caused by Cytochrome b5 Reductase Deficiency

A juvenile male mixed breed dog was presented for lethargy, exercise intolerance, and aggression when touched on the head. Cyanosis, tachycardia, and tachypnea were observed and persisted during oxygen supplementation. Arterial blood gas analysis by co‐oximetry identified an increased methemoglobin concentration (27%; normal, <2%) with normal arterial oxygen tension. The methemoglobinemia and associated clinical signs resolved after administration of methylene blue (1 mg/kg) IV, and the dog was discharged. The affected dog's whole‐genome sequence contained 2 potentially causal heterozygous CYB5R3 missense mutations suggesting that cytochrome b5 reductase deficiency was responsible for the methemoglobinemia. This hypothesis was confirmed by enzyme analysis that identified cytochrome b5 reductase activity in the affected dog's erythrocytes to only approximately 6% of that in a control sample. Clinical signs recurred 11 days after discharge but normalized and the methemoglobin concentration decreased with methylene blue administration PO (1.5 mg/kg, initially daily and then every other day).

Validation of capillary blood analysis and capillary testing mode on the epoc Point of Care system

Background

Laboratory test in transport is a critical component of patient care, and capillary blood is a preferred sample type particularly in children. This study evaluated the performance of capillary blood testing on the epoc Point of Care Blood Analysis System (Alere Inc).

Methods

Ten fresh venous blood samples was tested on the epoc system under the capillary mode. Correlation with GEM 4000 (Instrumentation Laboratory) was examined for Na+, K+, Cl-, Ca2+, glucose, lactate, hematocrit, hemoglobin, pO2, pCO2, and pH, and correlation with serum tested on Vitros 5600 (Ortho Clinical Diagnostics) was examined for creatinine. Eight paired capillary and venous blood was tested on epoc and ABL800 (Radiometer) for the correlation of Na+, K+, Cl-, Ca2+, glucose, lactate, hematocrit, hemoglobin, pCO2, and pH. Capillary blood from 23 apparently healthy volunteers was tested on the epoc system to assess the concordance to reference ranges used locally.

Results

Deming regression correlation coefficients for all the comparisons were above 0.65 except for ionized Ca2+. Accordance of greater than 85% to the local reference ranges were found in all assays with the exception of pO2 and Cl-.

Conclusion

Data from this study indicates that capillary blood tests on the epoc system provide comparable results to reference method for these assays, Na+, K+, glucose, lactate, hematocrit, hemoglobin, pCO2, and pH. Further validation in critically ill patients is needed to implement the epoc system in patient transport.

Impact of the study

This study demonstrated that capillary blood tests on the epoc Point of Care Blood Analysis System give comparable results to other chemistry analyzers for major blood gas and critical tests. The results are informative to institutions where pre-hospital and inter-hospital laboratory testing on capillary blood is a critical component of patient point of care testing.

Estimation of the severity of breathlessness in the emergency department: a dyspnea score

Background

Dyspnea is a frequent complaint in emergency departments (ED). It has a significant amount of subjective and affective components, therefore the dyspnea scores, based on the patients’ rating, can be ambiguous. Our purpose was to develop and validate a simple scoring system to evaluate the severity of dyspnea in emergency care, based on objectively measured parameters.

Methods

We performed a double center, prospective, observational study including 350 patients who were admitted in EDs with dyspnea. We evaluated the patients’ subjective feeling about dyspnea and applied our Dyspnea Severity Score (DSS), rating the dyspnea in 7 Dimensions from 0 to 3 points. The DSS was validated using the deterioration of pH, base-excess and lactate levels in the blood gas samples (Objective Classification Scale (OCS) 9 points and 13 points groups).

Results

All of the Dimensions correlated closely with the OCS values and with the subjective feeling of the dyspnea. Using multiple linear regression analysis we were able to decrease the numbers of Dimensions from seven to four without causing a significant change in the determination coefficient in any OCS groups. This reduced DSS values (exercise tolerance, cooperation, cyanosis, SpO2 value) showed high sensitivity and specificity to predict the values of OCS groups (the ranges: AUC 0.77–0.99, sensitivity 65–100%, specificity 64–99%). There was a close correlation between the subjective dyspnea scores and the OCS point values (p < 0.001), though the scatter was very large.

Conclusions

A new DSS was validated which score is suitable to compare the severity of dyspnea among different patients and different illnesses. The simplified version of the score (its value ≥7 points without correction factors) can be useful at the triage or in pre-hospital care.

Arterial versus venous lactate: a measure of sepsis in children

This study assessed the agreement between arterial and venous blood lactate and pH levels in children with sepsis. This retrospective, three-year study involved 60 PICU patients, with data collected from electronic or paper patient records. The inclusion criteria comprised of children (≤17 years old) with sepsis and those who had a venous blood gas taken first with an arterial blood gas taken after within one hour. The lactate and pH values measured through each method were analysed. There is close agreement between venous and arterial lactate up to 2 mmol/L. As this value increases, this agreement becomes poor. The limits of agreement (LOA) are too large (±1.90 mmol/L) to allow venous and arterial lactate to be used interchangeably. The mean difference and LOA between both methods would be much smaller if derived using lactate values under 2.0 mmol/L. There is close agreement between arterial and venous pH (MD = -0.056, LOA ± 0.121). However, due to extreme variations in pH readings during sepsis, pH alone is an inadequate marker.

CONCLUSION

A venous lactate ≤2 mmol/L can be used as a surrogate for arterial lactate during early management of sepsis in children. However, if the value exceeds 2 mmol/L, an arterial sample must confirm the venous result. What is known: • In children with septic shock, a blood gas is an important test to show the presence of acidosis and high lactic acid. Hyperlactataemia on admission is an early predictor of outcome and is associated with a greater mortality risk. • An arterial sample is the standard for lactate measurement, however getting a sample may be challenging in the emergency department or a general paediatric ward. Venous samples are quicker and easier to obtain. Adult studies generally advise caution in replacing venous lactate values for the arterial standard, whilst paediatric studies are limited in this area. What is new: • This is the first study assessing the agreement between arterial and peripheral venous lactate in children with sepsis, with a significant sample of patients. • This study shows that a venous sample with a lactate of ≤ 2 mmol/L can be used as a surrogate measurement for arterial lactate during early management of sepsis in children. However, if the venous lactate is above 2 mmol/L, an arterial sample must be taken to confirm the result.

Respiratory Acid-Base Disorders in the Critical Care Unit

The incidence of respiratory acid-base abnormalities in the critical care unit (CCU) is unknown, although respiratory alkalosis is suspected to be common in this population. Abnormal carbon dioxide tension can have many physiologic effects, and changes in Pco₂ may have a significant impact on outcome. Monitoring Pco₂ in CCU patients is an important aspect of critical patient assessment, and identification of respiratory acid-base abnormalities can be valuable as a diagnostic tool. Treatment of respiratory acid-base disorders is largely focused on resolution of the primary disease, although mechanical ventilation may be indicated in cases with severe respiratory acidosis.

Lactate point-of-care testing for acidosis: Cross-comparison of two devices with routine laboratory results

Objectives

Lactate is a major parameter in medical decision making. During labor, it is an indicator for fetal acidosis and immediate intervention. In the Emergency Department (ED), rapid analysis of lactate/blood gas is crucial for optimal patient care. Our objectives were to cross-compare-for the first time-two point-of-care testing (POCT) lactate devices with routine laboratory results using novel tight precision targets and evaluate different lactate cut-off concentrations to predict metabolic acidosis.

Design and methods

Blood samples from the delivery room (n=66) and from the ED (n=85) were analyzed on two POCT devices, the StatStrip-Lactate (Nova Biomedical) and the iSTAT-1 (CG4+ cassettes, Abbott), and compared to the routine laboratory analyzer (ABL-735, Radiometer). Lactate concentrations were cross-compared between these analyzers.

Results

The StatStrip correlated well with the ABL-735 (R=0.9737) and with the iSTAT-1 (R=0.9774) for lactate in umbilical cord blood. Lactate concentrations in ED samples measured on the iSTAT-1 and ABL-735 showed a correlation coefficient of R=0.9953. Analytical imprecision was excellent for lactate and pH, while for pO₂ and pCO₂ the coefficient of variation was relatively high using the iSTAT-1.

Conclusion

Both POCT devices showed adequate analytical performance to measure lactate. The StatStrip can indicate metabolic acidosis in 1 μl blood and will be implemented at the delivery room.

EVALUATION OF CARDIORESPIRATORY, BLOOD GAS, AND LACTATE VALUES DURING EXTENDED IMMOBILIZATION OF WHITE RHINOCEROS (CERATOTHERIUM SIMUM)

Ten white rhinoceros (Ceratotherium simum) were immobilized for a total of 13 procedures in holding facilities in Kruger National Park using etorphine, azaperone, and hyaluronidase to assess the effect of extended immobilization on serial cardiorespiratory, blood gas, and lactate values. Butorphanol was administered intravenously following initial blood collection and physiologic assessment (t=0). Respiratory and cardiovascular parameters, body temperature, and arterial blood gases were monitored at 10-min intervals for a total of 100 min. Initial parameters at the time of recumbency revealed severe hypoxemia, hypercapnia, tachycardia, an increased alveolar-arterial (A-a) gradient, and mildly elevated lactate levels. At 10 min and 20 min, there were significant (P<0.05) changes in the following physiologic parameters: heart rate decreased [96 and 80 beats/min, respectively, vs. 120 beats/min], arterial partial pressure of oxygen (PaO2) increased [48 and 45 mm Hg, respectively vs. 30 mm Hg], arterial hemoglobin oxygen saturation increased [79% and 74%, respectively, vs. 47%], A-a gradient decreased [29.13 and 30.00 mm Hg, respectively, vs. 49.19 mm Hg], and respiratory rate decreased [5 and 5 breaths/min vs. 7 breaths/min]. Blood lactate levels also decreased from 2.54 mM/L to 1.50 and 0.89 mM/L, respectively. Despite initial improvements in blood oxygen levels at t=10 and 20 min, the rhinoceros remained severely hypoxemic for the remainder of the procedure (median PaO2=50.5 mm Hg, 95% confidence interval, 43.8-58.1). Median values for respiratory rate (5 breaths/min) and arterial partial pressure of carbon dioxide (PaCO2; 68.5 mm Hg) did not change significantly for the remaining 80 min. Median lactate, base excess, bicarbonate, and pH values improved between 20 and 100 min despite the persistent hypercapnia, indicating that the animals adequately compensated for respiratory and lactic acidosis. White rhinoceros were immobilized for 100 min with no negative effects, a desirable outcome if procedures require extended chemical immobilization without oxygen supplementation.

Physiological responses to hypothermia

Therapeutic hypothermia is the only treatment currently recommended for moderate or severe encephalopathy of hypoxic‒ischaemic origin in term neonates. Though the effects of hypothermia on human physiology have been explored for many decades, much of the data comes from animal or adult studies; the latter originally after accidental hypothermia, followed by application of controlled hypothermia after cardiac arrest or trauma, or during cardiopulmonary bypass. Though this work is informative, the effects of hypothermia on neonatal physiology after perinatal asphyxia must be considered in the context of a prolonged hypoxic insult that has already induced a number of significant physiological sequelae. This article reviews the effects of therapeutic hypothermia on respiratory, cardiovascular, and metabolic parameters, including glycaemic control and feeding requirements. The potential pitfalls of blood‒gas analysis and overtreatment of physiological changes in cardiovascular parameters are also discussed. Finally, the effects of hypothermia on drug metabolism are covered, focusing on how the pharmacokinetics, pharmacodynamics, and dosing requirements of drugs frequently used in neonatal intensive care may change during therapeutic hypothermia.

Demonstration of compatibility of multiple arterial blood gas syringes with current multi-parameter analyzers

OBJECTIVE

Since there is a lack of current evidence to support the compatibility of the most commonly used arterial blood gas syringes with the latest multi-parameter analyzers, the objective of this study was to assess the agreement of analyte values between three heparinized arterial blood gas syringes using three different analyzers.

METHODS

Venous blood from 25 healthy volunteers was drawn into the study syringes (BD Drihep A-Line, PICO50, and Portex Line Draw Plus) by four clinician volunteers in a random order (441 total) and immediately (<15 minutes) analyzed (ABL800 FLEX, RAPIDPoint 500, i-STAT System) in a randomized order. The Bland-Altman method was used to assess agreement of analyte values between the syringes for each analyzer. The results by analyte and analyzer were compared across syringes using one-way ANOVA, and Tukey's approach was used to identify statistically significant differences between pairs of syringes.

RESULTS

Comparison of the syringes' mean differences and standard deviations showed close agreement for all three analyzers. There were no statistically significant differences between syringes in 14 of the analytes for any of the analyzers (p > 0.05). For RAPIDPoint and i-STAT, the Ca(2+) value was significantly less for A-Line than for the other syringes. The value for Na(+) was significantly greater for the PICO50 than the A-Line and Line Draw syringes with the i-STAT. Both results were within two standard deviations of the mean of the other two syringes and are not considered clinically significant; however, comparisons were not made between the values from the different analyzers.

CONCLUSIONS

Dry-balanced lithium heparin ABG syringes used for blood draws should provide reliable results, regardless of syringe type, provided that the clinicians use proper pre-analytical techniques.

Development enhances hypometabolism in northern elephant seal pups (Mirounga angustirostris)

Investigation into the development of oxygen storage capacity in air-breathing marine predators has been performed, but little is known about the development of regulatory factors that influence oxygen utilization. Strategies for efficiently using oxygen stores should enable marine predators to optimize time spent foraging underwater.We describe the developmental patterns of oxygen use during voluntary breath-holds in northern elephant seals (Mirounga angustirostris) at 2 and 7 weeks post-weaning. We measured 1) changes in oxygen consumption (VO₂), and 2) changes in venous pH, partial pressure of oxygen (pO₂), haemoglobin saturation (sO₂), oxygen content (O₂ct), partial pressure of carbon dioxide (pCO₂), haematocrit (Hct) and total haemoglobin (tHb). To examine the effect of the dive response on the development of oxygen utilization, voluntary breath-hold experiments were conducted in and out of water.Suppression of VO₂ during voluntary breath-holds increased significantly between 2 and 7 weeks post-weaning, reaching a maximum suppression of 53% below resting metabolic rate and 56% below Kleiber's standard metabolic rate. From 2 to 7 weeks post-weaning, breath-hold VO₂ was reduced by 52%. Between the two age classes, this equates to a mean breath-hold VO₂ reduction of 16% from resting VO₂. Breath-hold VO₂ also declined with increasing breath-hold duration, but there was no direct effect of voluntary submergence on reducing VO₂.Age did not influence rates of venous pO₂ depletion during breath-holds. However, voluntary submergence did result in slower pO₂ depletion rates when compared to voluntary terrestrial apnoeas. The differences in whole body VO₂ during breath-holds (measured at recovery) and venous pO₂ (reflective of tissue O₂-use measured during breath-holds), likely reflects metabolic suppression in hypoxic, vasoconstricted tissues.Consistent pCO₂ values at the end of all voluntary breath-holds (59.0 ± 0.7 mmHg) suggests the physiological cue for stimulating respiration in northern elephant seal pups is the accumulation of CO₂.Oxygen storage capacity and metabolic suppression directly limit diving capabilities and may influence foraging success in low-weaning weight seals forced to depart to sea prior to achieving full developmental diving capacity.

Development and evaluation of three mortality prediction indices for cold-stunned Kemp's ridley sea turtles (Lepidochelys kempii)

Kemp's ridley sea turtle is an endangered species found in the Gulf of Mexico and along the east coast of the USA. Cold-stunned Kemp's ridley turtles are often found stranded on beaches of Massachusetts and New York in November and December each year. When found alive, turtles are transported to rehabilitation centres for evaluation and treatment. Blood gas and chemistry analytes of major clinical relevance in sea turtles were selected to develop mortality prediction indices (MPI)s. Testing the diagnostic performance of various combinations of blood gas and chemistry analytes by receiver operating characteristics (ROC) analysis resulted in the development of three mortality prediction indices. The sensitivity and specificity of the best performing MPI (based on three blood analytes: pH, pO2, and potassium) was 88 and 80%, respectively. Using ROC analysis, the area under the curve = 0.896 (95% confidence interval = 0.83-0.94). The use of validated MPIs based on four blood analytes (pH, pCO2, pO2, and potassium) could be useful for better diagnosis, treatment, and prognosis of cold-stunned sea turtles when admitted to rehabilitation facilities.

Evolution of gas exchange abnormalities in patients with liver cirrhosis candidate for liver transplantation

BACKGROUND

Hypoxemia is common in patients with cirrhosis but the natural history of this syndrome is unknown. This study was conducted to evaluate the natural history of arterial oxygenation in patient with end stage liver cirrhosis.

METHODS

Sixty eight patients with liver cirrhosis were followed up for 6-12 months. Arterial blood gas (ABG) and pulse oximetry were obtained on day of presentation and follow up.

RESULTS

There were no significant changes in the oxygen saturation by pulse oximetry (SpO2), partial pressure of oxygen (PaO2) and alveolar arterial oxygen gradient (A-a O2) after 6-12 months. Mean arterial oxygen saturation (SaO2) in 46 patients was 95.42±1.92, and after follow up changed to 95.45±2.96. Thirty eight patients had SaO2 > 94% (mean 96.12±1.08 after 6-12 months changed to 95.66±2.58) ; 8 patients had SaO2 = 94 (mean 92.08±1.44 after 6-12 months changed to 94.46±4.47).

CONCLUSION

There were no significant changes in the SpO2, PaO2 and A-a O2 after 6-12 months.

Correlation of arterial blood gas measurements with venous blood gas values in mechanically ventilated patients

BACKGROUND

Arterial blood gas (ABG) analysis is useful in evaluation of the clinical condition of critically ill patients; however, arterial puncture or insertion of an arterial catheter may cause many complications. The aim of this study was to determine whether venous blood gas (VBG) values can be used as an alternative to arterial blood gas measurements in patients under mechanical ventilation.

MATERIALS AND METHODS

This study was carried out on patients admitted to the Intensive Care Unit of Kashan Beheshti Hospital. Blood for VBG analysis was obtained from the cubital vein, while for ABG analysis blood was taken simultaneously from the radial artery. ABG and VBG samples were obtained simultaneously, and indexes of pH, PCO2, HCO3, base excess (BE), PO2 and O2 saturation level were analyzed.

RESULTS

A total of 102 pair of simultaneous venous and arterial blood samples were obtained from 102 patients (mean age 58.4±21.5 years). Seventy (69%) were males. The mean difference between arterial and venous values was 0.04 for pH, 5.6 mm/Hg for PCO2, -0.32 mmol/l for HCO3, -1.03 mmol/l for BE, 53.6 mm/Hg for PO2, and 23.5% for O2 saturation. The Pearson correlation coefficients between arterial and venous values for pH, PCO2, HCO3, BE, PO2 and O2 saturation were 0.874, 0.835, 0.768, 0.810, 0.287, and 0.310, respectively. Linear regression equations for the estimation of pH, PCO2, HCO3, BE, PO2 and O2 saturation were as follows: arterial pH=1.927+0.745×venous pH [r=0.801, p<0.001]; PCO2=6.470+0.706×venous PCO2 [r=0.835, p<0.001]; arterial HCO3=7.455+0.681×venous HCO3 [r=0.768, p<0.001]; arterial BE=-0.952+0.736×venous BE [r=0.810, p<0.001]; arterial PO2=70.374+0.620×venous PO2 [r=0.287, p=0.003]; arterial venous saturation= 89.753+0.082×venous O2 saturation [r=0.317, p=0.001].

CONCLUSION

Venous blood gases, especially pH, Base excess, and PCO2 levels have relatively good correlation with ABG values. Because this correlation is not close, VBG cannot substitute ABG in mechanically ventilated patients.

The use of capnometry to predict arterial partial pressure of CO(2) in non-intubated breathless patients in the emergency department

Background

Capnometry measures carbon dioxide in expired air and provides the clinician with a noninvasive measure of the systemic metabolism, circulation and ventilation. This study was carried out on patients with acute breathlessness to define the utility and role of capnometry in the emergency department.

Aim

The objectives of the study were:

To determine the correlation between end tidal CO₂ and PaCO₂ in non-intubated acutely breathless patients.

To determine factors that influence the end tidal carbon dioxide (ETCO₂).

To determine the correlation between ETCO₂ with PaCO₂ in patients presenting with pulmonary disorders.

Methods

One hundred fifty acutely breathless patients arriving at the emergency department and fulfilling the inclusion and exclusion criteria were chosen during a 6-month study period. The patients gave written or verbal consent, and were triaged and treated according to their presenting complaints. Demographic data were collected, and the ETCO₂ data were recorded. Arterial blood gas was taken in all patients. The data were compiled and analyzed using various descriptive studies from the Statistics Program for Social Studies (SPSS) version 12. Correlation between ETCO₂ and PaCO₂ was analyzed using the Pearson correlation coefficient. Other variables also were analyzed to determine the correlation using simple linear regression. The agreement and difference between ETCO₂ and PaCO₂ were analyzed using paired sample t-tests.

Results

There is a strong correlation between ETCO₂ and PaCO₂ using the Pearson correlation coefficient: 0.716 and p value of 0.00 (p < 0.05). However, the paired t-test showed a mean difference between the two parameters of 4.303 with a p value < 0.05 (95% CI 2.818, 5.878). There was also a good correlation between ETCO₂ and acidosis state with a Pearson correlation coefficient of 0.374 and p value 0.02 (p < 0.05). A strong correlation was also observed between ETCO₂ and a hypocapnic state, with a Pearson correlation coefficient of 0.738 (p < 0.05). Weak correlation was observed between alkalosis and ETCO₂, with a Pearson correlation coefficient of 0.171 (p < 0.05). A strong negative correlation was present between ETCO₂ and hypercapnic patients presenting with pulmonary disorders, with a Pearson correlation coefficient of -0.738 (p < 0.05) and of -0.336 (p < 0.05), respectively.

Conclusion

This study shows that ETCO₂ can be used to predict the PaCO₂ level when the difference between the PaCO₂ and ETCO₂ is between 2 to 6 mmHg, especially in cases of pure acidosis and hypocapnia. Using ETCO₂ to predict PaCO₂ should be done with caution, especially in cases that involve pulmonary disorders and acid-base imbalance.

Electrochemical Sensors for Clinic Analysis

Demanded by modern medical diagnosis, advances in microfabrication technology have led to the development of fast, sensitive and selective electrochemical sensors for clinic analysis. This review addresses the principles behind electrochemical sensor design and fabrication, and introduces recent progress in the application of electrochemical sensors to analysis of clinical chemicals such as blood gases, electrolytes, metabolites, DNA and antibodies, including basic and applied research. Miniaturized commercial electrochemical biosensors will form the basis of inexpensive and easy to use devices for acquiring chemical information to bring sophisticated analytical capabilities to the non-specialist and general public alike in the future.