Venous oxygen saturation

The Effects of Exercise on Cardiogenic Shock with an Intra-Aortic Balloon Pump: A Case Report

This case report describes the exercise program on a hospitalized 54-year-old male patient with cardiogenic shock waiting for a heart transplant assisted by an intra-aortic balloon pump, a temporary mechanical circulatory support device. The temporary mechanical circulatory support device, an intra-aortic balloon pump, was placed in the left subclavian artery, enabling the exercise protocol. Measurements and values from Swan-Ganz catheter, blood sample, brain natriuretic peptide (NT-proBNP), and high-sensitivity C-reactive protein (hs-CRP), as well as the six-minute walk test (6MWT) and venous oxygen saturation (SvO2) were obtained before and after an exercise protocol. The exercise training protocol involved the use of an unloaded bed cycle ergometer once a day, for a maximum of 30 minutes, to the tolerance limit. No adverse events or events related to the dislocation of the intra-aortic balloon pump were observed during the exercise protocol. The exercise program resulted in higher SvO2 levels, with an increased 6MWT with lower Borg dyspnea scores (312 meters vs. 488 meters and five points vs. three points, respectively). After completing the ten-day exercise protocol, the patient underwent a non-complicated heart transplant surgery and a full recovery in the ICU. This study showed that exercise is a feasible option for patients with cardiogenic shock who are using an intra-aortic balloon pump and that it is well-tolerated with no reported adverse events.

A priori free spectral unmixing with periodic absorbance changes: application for auto-calibrated intraoperative functional brain mapping

Spectral unmixing designates techniques that allow to decompose measured spectra into linear or non-linear combination of spectra of all targets (endmembers). This technique was initially developed for satellite applications, but it is now also widely used in biomedical applications. However, several drawbacks limit the use of these techniques with standard optical devices like RGB cameras. The devices need to be calibrated and a a priori on the observed scene is often necessary. We propose a new method for estimating endmembers and their proportion automatically and without calibration of the acquisition device based on near separable non-negative matrix factorization. This method estimates the endmembers on spectra of absorbance changes presenting periodic events. This is very common in in vivo biomedical and medical optical imaging where hemodynamics dominate the absorbance fluctuations. We applied the method for identifying functional brain areas during neurosurgery using four different RGB cameras (an industrial camera, a smartphone and two surgical microscopes). Results obtained with the auto-calibration method were consistent with the intraoperative gold standards. Endmembers estimated with the auto-calibration method were similar to the calibrated endmembers used in the modified Beer-Lambert law. The similarity was particularly strong when both cardiac and respiratory periodic events were considered. This work can allow a widespread use of spectral imaging in the industrial or medical field.

Noninvasive tracking of mixed venous oxygen saturation via near-infrared spectroscopy cerebral oximetry: a retrospective observational study

Although previous studies have shown correlation between regional cerebral oxygen saturation (rScO2) and mixed venous oxygen saturation (SvO2), there is a lack of pragmatic information on the clinical applicability of these findings, such as tracking ability. We retrospectively analyzed continuous intraoperative recordings of rScO2 and SvO2 obtained from a pulmonary artery catheter and either of two near-infrared spectroscopy (NIRS) devices (INVOS 5100C, Medtronic; O3, Masimo) during off-pump cardiopulmonary bypass (OPCAB) surgery in adult patients. The ability of rScO2 to track SvO2 was quantitatively evaluated with 5 min interval changes transformed into relative values. The analysis included 176 h of data acquired from 48 subjects (26 and 22 subjects for INVOS and O3 dataset, respectively). The area under ROC of the left-rScO2 for detecting change of SvO2 ≥ 10% in INVOS and O3 datasets were 0.919 (95% CI 0.903-0.936) and 0.852 (95% CI 0.818-0.885). The concordance rates between the interval changes of left-rScO2 and SvO2 in INVOS and O3 datasets were 90.6% and 91.9% with 10% exclusion zone. rScO2 can serve as a noninvasive tool for detecting changes in SvO2 levels, a critical hemodynamic measurement.

The ∆Pv-aCO2/∆Ca-vO2 ratio as a predictor of mortality in patients with severe acute respiratory distress syndrome related to COVID-19

OBJECTIVE

To evaluate the central venous-to-arterial carbon dioxide difference combined with arterial-to-venous oxygen content difference (∆Pv-aCO2/∆Ca-vO2 ratio) as a predictor of mortality in patients with COVID-19-related severe acute respiratory distress syndrome (ARDS).

METHODS

Patients admitted to the intensive care unit with severe ARDS secondary to SARS-CoV-2, and invasive mechanical ventilation were included in this single-center and retrospective cohort study performed between April 18, 2020, and January 18, 2022. The tissue perfusion indexes (lactate, central venous oxygen saturation [ScvO2], and venous-to-arterial carbon dioxide pressure difference [∆Pv-aCO2]), anaerobic metabolism index (∆Pv-aCO2/∆Ca-vO2 ratio), and severity index (Simplified Acute Physiology Score II [SAPSII]) were evaluated to determine its association with the mortality through Cox regression analysis, Kaplan-Meier curve and receiver operating characteristic (ROC) curve.

RESULTS

One hundred fifteen patients were included in the study and classified into two groups, the survivor group (n = 54) and the non-survivor group (n = 61). The lactate, ScvO2, ∆Pv-aCO2, and ∆Pv-aCO2/∆Ca-vO2 ratio medians were 1.6 mEq/L, 75%, 5 mmHg, and 1.56 mmHg/mL, respectively. The ∆Pv-aCO2/∆Ca-vO2 ratio (Hazard Ratio (HR) = 1.17, 95% confidence interval (CI) = 1.06-1.29, p = 0.001) was identified as a mortality biomarker for patients with COVID-19-related severe ARDS. The area under the curve for ∆Pv-aCO2/∆Ca-vO2 ratio was 0.691 (95% CI 0.598-0.774, p = 0.0001). The best cut-off point for ∆Pv-aCO2/∆Ca-vO2 ratio was >2.14 mmHg/mL, with a sensitivity of 49.18%, specificity of 85.19%, a positive likelihood of 3.32, and a negative likelihood of 0.6. The Kaplan-Meier curve showed that survival rates were significantly worse in patients with values greater than this cut-off point.

CONCLUSIONS

The ∆Pv-aCO2/∆Ca-vO2 ratio could be used as a predictor of mortality in patients with severe ARDS secondary to SARS-CoV-2.

Oxygen saturation in intraosseous sternal blood measured by CO-oximetry and evaluated non-invasively during hypovolaemia and hypoxia - a porcine experimental study

PURPOSE

This study intended to determine, and non-invasively evaluate, sternal intraosseous oxygen saturation (SsO₂) and study its variation during provoked hypoxia or hypovolaemia. Furthermore, the relation between SsO₂ and arterial (SaO₂) or mixed venous oxygen saturation (SvO₂) was investigated.

METHODS

Sixteen anaesthetised male pigs underwent exsanguination to a mean arterial pressure of 50 mmHg. After resuscitation and stabilisation, hypoxia was induced with hypoxic gas mixtures (air/N₂). Repeated blood samples from sternal intraosseous cannulation were compared to arterial and pulmonary artery blood samples. Reflection spectrophotometry measurements by a non-invasive sternal probe were performed continuously.

RESULTS

At baseline SaO₂ was 97.0% (IQR 0.2), SsO₂ 73.2% (IQR 19.6) and SvO₂ 52.3% (IQR 12.4). During hypovolaemia, SsO₂ and SvO₂ decreased to 58.9% (IQR 16.9) and 38.1% (IQR 12.5), respectively, p < 0.05 for both, whereas SaO₂ remained unaltered (p = 0.44). During hypoxia all saturations decreased; SaO₂ 71.5% (IQR 5.2), SsO₂ 39.0% (IQR 6.9) and SvO₂ 22.6% (IQR 11.4) (p < 0.01), respectively. For hypovolaemia, the sternal probe red/infrared absorption ratio (SQV) increased significantly from baseline (indicating a reduction in oxygen saturation) + 5.1% (IQR 7.4), p < 0.001 and for hypoxia + 19.9% (IQR 14.8), p = 0.001, respectively.

CONCLUSION

Sternal blood has an oxygen saturation suggesting a mixture of venous and arterial blood. Changes in SsO₂ relate well with changes in SvO₂ during hypovolaemia or hypoxia. Further studies on the feasibility of using non-invasive measurement of changes in SsO₂ to estimate changes in SvO₂ are warranted.

Blood gas analysis as a surrogate for microhemodynamic monitoring in sepsis

BACKGROUND

Emergency patients with sepsis or septic shock are at high risk of death. Despite increasing attention to microhemodynamics, the clinical use of advanced microcirculatory assessment is limited due to its shortcomings. Since blood gas analysis is a widely used technique reflecting global oxygen supply and consumption, it may serve as a surrogate for microcirculation monitoring in septic treatment.

METHODS

We performed a search using PubMed, Web of Science, and Google scholar. The studies and reviews that were most relevant to septic microcirculatory dysfunctions and blood gas parameters were identified and included.

RESULTS

Based on the pathophysiology of oxygen metabolism, the included articles provided a general overview of employing blood gas analysis and its derived set of indicators for microhemodynamic monitoring in septic care. Notwithstanding flaws, several parameters are linked to changes in the microcirculation. A comprehensive interpretation of blood gas parameters can be used in order to achieve hemodynamic optimization in septic patients.

CONCLUSION

Blood gas analysis in combination with clinical performance is a reliable alternative for microcirculatory assessments. A deep understanding of oxygen metabolism in septic settings may help emergency physicians to better use blood gas analysis in the evaluation and treatment of sepsis and septic shock.

Cerebral Venous Oxygen Saturation in Hypoperfusion Regions May Become a New Imaging Indicator to Predict the Clinical Outcome of Stroke

To automatically and quantitatively evaluate the venous oxygen saturation (SvO2) in cerebral ischemic tissues and explore its value in predicting prognosis. A retrospective study was conducted on 48 AIS patients hospitalized in our hospital from 2015−2018. Based on quantitative susceptibility mapping and perfusion-weighted imaging, this paper measured the cerebral SvO2 in hypoperfusion tissues and its change after intraarterial rt-PA treatment. The cerebral SvO2 in different hypoperfusion regions between the favorable and unfavorable clinical outcome groups was analyzed using an independent t-test. Relationships between cerebral SvO2 and clinical scores were determined using the Pearson correlation coefficient. The receiver operating characteristic process was conducted to evaluate the accuracy of cerebral SvO2 in predicting unfavorable clinical outcomes. Cerebral SvO2 in hypoperfusion (Tmax > 4 and 6 s) was significantly different between the two groups at follow-up (p < 0.05). Cerebral SvO2 and its changes before and after treatment were negatively correlated with clinical scores. The positive predictive value, negative predictive value, accuracy, and area under the curve of the cerebral SvO2 were higher than those predicted by the ischemic core. Therefore, the cerebral SvO2 of hypoperfusion regions was a stronger imaging predictor of unfavorable clinical outcomes after stroke.

Assessment of Clinical Profile and Treatment Outcome in Vaccinated and Unvaccinated SARS-CoV-2 Infected Patients

Vaccines against severe acute respiratory syndrome-corona virus-2 (SARS-CoV-2) infection, which causes coronavirus disease–19 (COVID-19) in humans, have been developed and are being tested for safety and efficacy. We conducted the cross-sectional prospective cohort study on 820 patients who were positive for SARS-CoV-2 and were admitted to Princess Krishnajammanni trauma care centre (PKTCC), Mysore, which was converted to a designated COVID hospital between April 2021 to July 2021. After obtaining the informed consent, RT-PCR report, vaccination certificate and patient history, patients were classified according to their vaccination status. Results from the study showed decreases in serum ferritin levels, clinical symptoms, improvement in oxygen saturation, early recovery in patients having diabetes and hypertension, and a substantial reduction in the overall duration of hospital stay in vaccinated patients compared to unvaccinated patients. Further, fully vaccinated patients showed better outcomes compared to single dose vaccinated and nonvaccinated patients. Taken together, our findings reaffirm the vaccine’s effectiveness in reducing case fatality and promoting faster recovery compared to nonvaccinated patients. Efforts to increase the number of immunized subjects in the community help to achieve herd immunity and offer protection against the severity of COVID-19 and associated complications while minimizing the public health and economic burden.

Development of Low-Cost and Portable Pulse Oximeter Device with Improved Accuracy and Accessibility

Purpose

Methods

Results

Conclusion

[Hemodynamic Monitoring in the ICU: the More Invasive, the Better?]

Less invasive or even completely non-invasive haemodynamic monitoring technologies have evolved during the last decades. However, the invasive devices such as the pulmonary artery catheter and transpulmonary thermodilution technologies are still the clinical gold standard in terms of advanced haemodynamic monitoring, especially in the treatment of critically ill patients. The current data situation regarding the early use of continuous haemodynamic monitoring in this patient population, specifically flow-based variables such as stroke volume to prevent occult hypoperfusion, is overwhelming. However, the effective implementation of these technologies in daily clinical routine is remarkably low. Given the fact that perioperative morbidity and mortality are higher than anticipated, anaesthesiologists and intensivists are in charge to deal with this problem. The recent advances in minimally invasive and non-invasive haemodynamic monitoring technologies may facilitate a more widespread use in the operating theatre and in critical care patients. This review evaluates the significance of invasive, minimally- and non-invasive monitoring devices and their specific haemodynamic variables in this particular field of perioperative medicine.

Resuscitation of the Critically Ill Older Adult

In 30 years, adults 65 and older will represent 20% of the US population, with increased medical comorbidities leading to higher rates of critical illness and mortality. Despite significant acute illness, presenting symptoms and vital sign abnormalities may be subtle. Resuscitative guidelines are a helpful starting point but appropriate diagnostics, bedside ultrasound, and frequent reassessments are needed to avoid procrustean care that may worsen outcomes. Baseline functional status is as important as underlying comorbid conditions when prognosticating, and the patient's personal wishes should be sought early and throughout care with clear communication regarding prospects for immediate survival and overall recovery.

Pulse oximetry curves in healthy children living at moderate altitude: a cross-sectional study from the Ecuadorian Andes

Background

In populations above 3,000 meters above sea level (m.a.s.l.) normal values of oxygen saturation (SpO2) above 90% have been reported. Few studies have been conducted in cities of moderate altitude (between 2,500 and 3,000 m a.s.l). We set out to describe the range of SpO2 values measured with a pulse oximeter in healthy children between 1 month and 12 years of age living in an Ecuadorian Andean city.

Methods

A cross-sectional study was carried out in Quito, Ecuador, located at 2,810 m a.s.l. SpO2 measurement in healthy children of ages ranging from 1 month to 12 years of age residents in the city were recorded by pulse oximetry. Age and gender were recorded, and median and 2.5th and 5th percentile were drawn. Non parametric tests were used to compare differences in SpO2 values by age and gender.

Results

1,378 healthy children were included for the study, 719 (52.2%) males. The median SpO2 for the entire population was 94.5%. No differences were observed between SpO2 median values by age and gender. The 2.5th percentile for global SpO2 measurements was 90%, in children under 5 years of age was 91% and it was 90% in children older than 7.

Conclusions

Our results provide SpO2 values for healthy children from 1 to 12 years old residents in Quito, a city of moderate altitude. The SpO2 percentile curve could contribute as a healthy range for the clinical evaluation of children residing at this altitude.

Peripartum findings and blood gas analysis in newborn foals born after spontaneous or induced parturition

Induction of parturition in horses is still not well accepted due to the potential peripartum complications for mares and newborn foals. We assessed differences after spontaneous and induced parturition with low doses of oxytocin (OX) in 1) incidence of peripartum complications in mares; 2) viability, behavioral, physical, and venous blood gas analyses in foals. In this study 61 mares were included; 45/61 were enrolled in the spontaneous foaling group (SF) and 16/61 in the induced foaling group (IF). In the IF group, when the calcium in mammary secretion reached concentrations of ≥250 ppm, mares received a single injection of 2.5 IU of oxytocin IV once a day until foaling. Mares' breed, age, parity, gestational and stage II length, and peripartum complications were recorded. Foal maturity, vital (Apgar score), behavioral and physical parameters were assessed at birth, and the foal clinical condition was monitored for one week. A jugular venous blood sample was collected at birth for blood gas analysis, acid-base status, and lactate assessment. The median gestational length was within the reference interval in all the mares included and did not differ between the two groups. No statistical differences in the II stage length nor in incidence of peripartum complications were observed between the two groups. All the foals were born alive and showed no signs of prematurity/dysmaturity. No statistical differences were found in foal viability between the two groups. Time to stand and nurse from the mare, and body temperature were significantly higher in the IF compared to the SF group. Venous blood pH, SO₂% and BE were lower, while pCO₂ and lactate were higher in the IF than in the SF group. All the foals in both groups remained clinically healthy during the observation period. In conclusion, at term induction of parturition with a low dose of oxytocin does not have adverse effects on peripartum in mares. Our findings suggest that at term induced foals suffer slightly greater, but not clinically significant, hypoxia, hypercapnia and acidosis than spontaneously delivered foals.

Correlation of Venous Oxygen Saturations from Noninvasive Hematocrit Monitoring Using Blood Gas Measured Oximetry in Chronic Pediatric Hemodialysis Patients

INTRODUCTION

Noninvasive hematocrit monitoring (NIVHM) during pediatric hemodialysis (pedHD) provides data in real time regarding changes in hematocrit and blood volume and also provides venous oxygen saturations. The latter has been proposed to indicate changes in tissue oxygen consumption. It is not known how well NIVHM oxygen saturations (O2sat) approximate blood gas measured oximetry saturation (mO2sat) in the course of pedHD. We aimed to assess the validity and reliability of NIVHM O2sat compared to mO2sat.

METHODS

This is a prospective study in 15 patients <21 years old with >90 days on hemodialysis (HD) without congenital heart disease. HD access was fistula (AVF) in 4 patients and tunneled catheters in the remainder. Pulse oximetry (spO2) was continuously monitored; mO2sat was measured via oximetry in a blood gas analyzer and NIVHM O2sat values collected at the start, middle, and end of HD treatment.

RESULTS

A total of 45 dyad measurements were obtained. NIVHM O2sat correlated well with mO2sat (R = 0.89, p < 0.0001); the same was seen at pre, mid, and post HD time points (R = 0.86-0.95, p < 0.001). NIVHM O2sat was lower than mO2sat; with catheter as access, the difference was 9.3 ± 8.6 (CI: 12.3-6.22, p < 0.0001) and with AVF was 2.1 ± 0.78 (CI: 2.6-1.7, p < 0.0001). Bland-Altman analysis demonstrated the difference but did not show any systematic bias. Continuous monitor of spO2 showed no hypoxia.

DISCUSSION/CONCLUSION

Intradialytic NIVHM O2sat correlates well with mO2sat but yield lower values. Future studies can include NIVHM O2sat changes as a surrogate for central venous O2 saturation changes and potentially yield useful information regarding tissue oxygen consumption in pedHD patients.

Contemporary hemodynamic monitoring, fluid responsiveness, volume optimization, and endpoints of resuscitation: an AAST critical care committee clinical consensus

This article, on hemodynamic monitoring, fluid responsiveness, volume assessment, and endpoints of resuscitation, is part of a compendium of guidelines provided by the AAST (American Association for the Surgery of Trauma) critical care committee. The intention of these guidelines is to inform practitioners with practical clinical guidance. To do this effectively and contemporarily, expert consensus via the critical care committee was obtained. Strict guideline methodology such a GRADE (Grading of Recommendations Assessment, Development and Evaluation) was purposefully NOT used so as not to limit the possible clinical guidance. The critical care committee foresees this methodology as practically valuable to the bedside clinician.

Efficacy of minimal invasive cardiac output and ScVO2 monitoring during controlled hypotension for double-jaw surgery

Background

Controlled hypotension (CH) provides a better surgical environment and reduces operative time. However, there are some risks related to organ hypoperfusion. The EV1000/FloTrac system can provide continuous cardiac output monitoring without the insertion of pulmonary arterial catheter. The present study investigated the efficacy of this device in double jaw surgery under CH.

Methods

We retrospectively reviewed the medical records of patients who underwent double jaw surgery between 2010 and 2015. Patients were administered conventional general anesthesia with desflurane; CH was performed with remifentanil infusion and monitored with an invasive radial arterial pressure monitor or the EV1000/FloTrac system. We allocated the patients into two groups, namely an A-line group and an EV1000 group, according to the monitoring methods used, and the study variables were compared.

Results

Eighty-five patients were reviewed. The A-line group reported a higher number of failed CH (P = 0.005). A significant correlation was found between preoperative hemoglobin and intraoperative packed red blood cell transfusion (r = 0.525; P < 0.001). In the EV1000 group, the mean arterial pressure (MAP) was significantly lower 2 h after CH (P = 0.014), and the cardiac index significantly decreased 1 h after CH (P = 0.001) and 2 h after CH (P = 0.007). Moreover, venous oxygen saturation (ScVO₂) decreased significantly at both 1 h (P = 0.002) and 2 h after CH (P = 0.029); however, these values were within normal limits.

Conclusion

The EV1000 group reported a lower failure rate of CH than the A-line group. However, EV1000/FloTrac monitoring did not present with any specific advantage over the conventional arterial line monitoring when CH was performed with the same protocol and same mean blood pressure. Preoperative anemia treatment will be helpful to decrease intraoperative transfusion. Furthermore, ScVO₂ monitoring did not present with sufficient benefits over the risk and cost.

Central venous oxygen saturation is not predictive of early complications in cancer patients presenting to the emergency department

Central venous oxygen saturation (ScvO₂) is easily observable in oncology patients with long-term central venous catheters (CVC), and has been studied as a prognostic factor in patients with sepsis. We sought to investigate the association between ScvO₂ and early complications in cancer patients presenting to the ED. We prospectively enrolled adult cancer patients with pre-existing CVC who presented to the ED. ScvO₂ was measured on their CVC. The outcome was admission to the intensive care unit (ICU) or mortality by day 7. ScvO₂ was first studied as a continuous variable (%) with a ROC analysis and as a categorical variable (cut-off at < 70%) with a multivariate analysis. A total of 210 cancer patients were enrolled. At baseline, ScvO₂ showed no significant difference between patients who were admitted to the ICU or died before day 7, and patients who did not (67%; IQR 62-68% vs. 71%; IQR 65-78% respectively, P = 0.3). The ROC analysis showed the absence of discrimination accuracy for ScvO₂ to predict the outcome (AUC = 0.56). By multivariate analysis, ScvO₂ < 70% was not associated with the outcome (OR 1.67; 95% CI 0.64-4.36). Variables that were associated with ICU admission or death by day 7 included a shock-index (heart rate/systolic blood pressure) > 1 and a performance status > 2 (OR 4.76; 95% CI 1.81-12.52 and OR 6.23, 95% CI 2.40-16.17, respectively). This study does not support the use of ScvO₂ to risk stratify cancer patients presenting to the ED.

Reduced deep regional cerebral venous oxygen saturation in hemodialysis patients using quantitative susceptibility mapping

Cerebral venous oxygen saturation (SvO₂) is an important indicator of brain function. There was debate about lower cerebral oxygen metabolism in hemodialysis patients and there were no reports about the changes of deep regional cerebral SvO₂ in hemodialysis patients. In this study, we aim to explore the deep regional cerebral SvO₂ from straight sinus using quantitative susceptibility mapping (QSM) and the correlation with clinical risk factors and neuropsychiatric testing_. 52 hemodialysis patients and 54 age-and gender-matched healthy controls were enrolled. QSM reconstructed from original phase data of 3.0 T susceptibility-weighted imaging was used to measure the susceptibility of straight sinus. The susceptibility was used to calculate the deep regional cerebral SvO₂ and compare with healthy individuals. Correlation analysis was performed to investigate the correlation between deep regional cerebral SvO₂, clinical risk factors and neuropsychiatric testing. The deep regional cerebral SvO₂ of hemodialysis patients (72.5 ± 3.7%) was significantly lower than healthy controls (76.0 ± 2.1%) (P < 0.001). There was no significant difference in the measured volume of interests of straight sinus between hemodialysis patients (250.92 ± 46.65) and healthy controls (249.68 ± 49.68) (P = 0.859). There were no significant correlations between the measured susceptibility and volume of interests in hemodialysis patients (P = 0.204) and healthy controls (P = 0.562), respectively. Hematocrit (r = 0.480, P < 0.001, FDR corrected), hemoglobin (r = 0.440, P < 0.001, FDR corrected), red blood cell (r = 0.446, P = 0.003, FDR corrected), dialysis duration (r = 0.505, P = 0.002, FDR corrected) and parathyroid hormone (r = -0.451, P = 0.007, FDR corrected) were risk factors for decreased deep regional cerebral SvO₂ in patients. The Mini-Mental State Examination (MMSE) scores of hemodialysis patients were significantly lower than healthy controls (P < 0.001). However, the deep regional cerebral SvO₂ did not correlate with MMSE scores (P = 0.630). In summary, the decreased deep regional cerebral SvO₂ occurred in hemodialysis patients and dialysis duration, parathyroid hormone, hematocrit, hemoglobin and red blood cell may be clinical risk factors.

Hemodynamics and tissue oxygenation effects after increased in positive end-expiratory pressure in coronary artery bypass surgery

Background

Cardiac surgery is widely used in the treatment of cardiovascular diseases. However, several complications can be observed during the postoperative period. Positive end expiratory pressure (PEEP) improves gas exchange, but it might be related to decreased cardiac output and possible impairment of tissue oxygenation. The aim of this study was to investigate the hemodynamic effects and oxygen saturation of central venous blood (ScvO₂) after increasing PEEP in hypoxemic patients after coronary artery bypass (CAB) surgery.

Methods

Seventy post-cardiac surgery patients (CAB), 61 ± 7 years, without ventricular dysfunction (left ventricular ejection fraction 57 ± 2%), with hypoxemia (PaO₂/FiO₂ ratio <200) were enrolled. Heart rate, mean arterial pressure, arterial and venous blood samples were measured at intensive care unit and PEEP was increased to 12 cmH₂O for 30 min.

Results

As expected, PEEP12 improved arterial oxygenation and PaO₂/FiO₂ ratio (p < 0.0001). Reduction in ScvO₂ was observed between PEEP5 (63 ± 2%) and PEEP12 (57 ± 1%; p = 0.01) with higher values of blood lactate in PEEP12 (p < 0.01). No hemodynamic effects (heart rate, mean arterial pressure, SpO₂; p > 0.05) were related.

Conclusion

Increased PEEP after cardiac surgery decreased ScvO₂ and increased blood lactate, even with higher O₂ delivery. PEEP did not interfere in hemodynamics status in CAB patients, suggesting that peripheral parameters must be controlled and measured during procedures involving increased PEEP in post-cardiac surgery patients in the intensive care unit.

Predictive value of ScvO2 monitoring for pericardial tamponade after cardiac surgery

BACKGROUND

We examined the predictive value of central venous oxygen saturation (ScvO2) changes regarding the occurrence of pericardial tamponade following cardiac surgery.

METHODS

We retrospectively identified 66 consecutive patients in whom ScvO2 and arterial lactate levels were analyzed during an 8‑h time interval preceding pericardiotomy due to pericardial tamponade (PT), and at equivalent time points in 30 control patients (C) who had an uncomplicated course.

RESULTS

The median age of the patients was 74 years (interquartile range, 63-78). Three percent of procedures were re-operations. There were no differences between the baseline values of PT and C patients. Pericardiotomy was performed on average 1 day (0-3.5) after cardiac surgery. PT patients displayed a significant decline (p < 0.001) to lower ScvO2 levels (p < 0.001) and a significant increase (p = 0.005) to higher arterial lactate levels (p = 0.019) during the 8 h preceding pericardiotomy, whereas C patients did not (p = 0.440 and p = 0.279, respectively). PT was associated with a longer hospital stay (p = 0.04) and a higher in-hospital mortality (p = 0.008). An ScvO2 decline below 60% (p = 0.018), a delta ScvO2 decline greater than 5% (p = 0.001), and a delta lactate increase greater than 0.18 mmol/l (p = 0.002) during the 8 h preceding pericardiotomy were independently associated with PT. None of these parameters predicted in-hospital mortality.

CONCLUSION

Deteriorations in ScvO2 might serve as an early marker of PT following cardiac surgery.