Reliability of temperatures measured at standard monitoring sites as an index of brain temperature during deep hypothermic cardiopulmonary bypass conducted for thoracic aortic reconstruction

Hypothermic Circulatory Arrest in Adult Aortic Arch Surgery: A Review of Hypothermic Circulatory Arrest and its Anesthetic Implications

Diseases affecting the aortic arch often require surgical intervention. Hypothermic circulatory arrest (HCA) enables a safe approach during open aortic arch surgeries. Additionally, HCA provides neuroprotection by reducing cerebral metabolism and oxygen requirements. However, HCA comes with significant risks (eg, neurologic dysfunction, stroke, and coagulopathy), and the cardiac anesthesiologist must completely understand the surgical techniques, possible complications, and management strategies.

Performance of the transoesophageal echocardiography probe as an oesophageal temperature monitor in patients undergoing cardiac surgery with cardiopulmonary bypass: a prospective observational study

OBJECTIVES

Core temperature monitoring is critical during cardiopulmonary bypass (CPB). In this prospective observational study, we investigated the performance of the transoesophageal echocardiography (TOE) probe for core (oesophageal) temperature monitoring during CPB.

METHODS

Thirty adult patients, 18-70 years of either gender, undergoing cardiac surgery with CPB were enrolled. All patients received a reusable nasopharyngeal probe for monitoring core temperatures. In addition, the oesophageal temperatures were monitored with the TOE probe. The arterial outlet temperatures at the membrane oxygenator were also monitored and taken as the reference standard. Monitoring was performed every 5 min until 20 min, and then at 30 min during both the cooling and rewarming periods.

RESULTS

During cooling, the oesophageal and nasopharyngeal temperatures lagged behind the arterial outlet temperatures. However, the intra-class correlation of the oesophageal temperatures with the arterial outlet temperatures was better (range 0.58-0.74) than the correlation of the nasopharyngeal temperatures with the arterial outlet temperatures (range 0.46-0.62). During rewarming, the performance of the TOE probe was significantly superior to the nasopharyngeal probe. After 15 and 20 min of rewarming, there was a difference of ∼1°C between the oesophageal and nasopharyngeal temperatures. At 30 min of rewarming, the oesophageal and the arterial outlet temperatures were similar, while the nasopharyngeal temperatures still lagged by 0.5°C. Bias was significantly less both during cooling and warming between the oesophageal temperatures and arterial outlet temperatures.

CONCLUSIONS

Performance of the TOE probe as an oesophageal temperature probe is superior to the nasopharyngeal probe during CPB.

CLINICAL TRIAL REGISTRATION NUMBER

CTRI no 2020/10/028228; ctri.nic.in.

Investigation of post mortem brain, rectal and forehead temperature relations

It is well known that magnetic resonance (MR) imaging is temperature sensitive, which is highly relevant for post mortem examinations. Therefore, the determination of the exact temperature of the investigated body site, e.g. the brain, is crucial. However, direct temperature measurements are invasive and inconvenient. Thus, in view of post mortem MR imaging of the brain, this study aims at investigating the relation between the brain and the forehead temperature for modelling the brain temperature based on the non-invasive forehead temperature. In addition, the brain temperature will be compared to the rectal temperature. Brain temperature profiles measured in the longitudinal fissure between the brain hemispheres, as well as rectal and forehead temperature profiles of 16 deceased were acquired continuously. Linear mixed, linear, quadratic and cubic models were fitted to the relation between the longitudinal fissure and the forehead and between the longitudinal fissure and the rectal temperature, respectively. Highest adjusted R2 values were found between the longitudinal fissure and the forehead temperature, as well as between the longitudinal fissure and the rectal temperature using a linear mixed model including the sex, environmental temperature and humidity as fixed effects. The results indicate that the forehead, as well as the rectal temperature, can be used to model the brain temperature measured in the longitudinal fissure. Comparable fit results were observed for the longitudinal fissure-forehead temperature relation and for the longitudinal fissure-rectal temperature relation. Combined with the fact that the forehead temperature overcomes the problem of measurement invasiveness, the results suggest using the forehead temperature for modelling the brain temperature in the longitudinal fissure.

Reliability of different body temperature measurement sites during normothermic cardiac surgery

INTRODUCTION

Patients undergoing cardiac surgery can experience significant thermal changes during the perioperative period and, for that reason, it is essential to monitor temperatures with adequate accuracy and precision during cardiopulmonary bypass (CPB). The primary aim of the current study was to measure the discrepancies between temperatures at different body sites during normothermic or mild hypothermic CPB.

METHODS

48 patients undergoing cardiac surgery participated in our study. Simultaneous temperatures were measured at nasopharynx, pulmonary artery, arterial outlet, venous inlet, forehead using a heat flux sensor, and urinary bladder at 5-min intervals throughout surgery. The Bland-Altman plot for repeated measures was used to assess concordance between methods.

RESULTS

The duration of surgery was 360 min (interquartile range (IQR) 300-412), while the median cross-clamp time was 135 min (IQR 101-169). During the CPB time, the average difference between arterial outlet and nasopharyngeal temperature was -0.16°C (95% limits of agreement of ±0.93). The bias between arterial outlet and the venous inflow was 0.16°C and the 95% limits of agreement were -0.63 to 0.95°C. The Bland-Altman analysis showed an average difference between oxigenator arterial outlet and bladder probe of -0.62 (95% limits of agreement of ±1.3). The average difference between arterial outlet and Tcore™ temperatures was 0.08°C (95% limits of agreement of ±1.46). 25 patients (52.08%) presented nasopharyngeal temperatures higher than 37°C in the post-CPB period, but none of them exceeded 38°C.

CONCLUSIONS

Perfusionists should be cautious when using the nasopharyngeal site as the only surrogate of brain temperature, even in normothermic cardiac surgery because the precision of measurements is not entirely adequate.

Prediction of Intracranial Temperature Through Invasive and Noninvasive Measurements on Patients with Severe Traumatic Brain Injury

The brain's temperature measurements (TB) in patients with severe brain damage are important, in order to offer the optimal treatment. The purpose of this research is the creation of mathematical models for the TB's prediction, based on the temperatures in the bladder (TBL), femoral artery (TFA), ear canal (TΕC), and axilla (TA), without the need for placement of intracranial catheter, contributing significantly to the research of the human thermoregulatory system.The research involved 18 patients (13 men and 5 women), who were hospitalized in the adult intensive care units (ICU) of Larissa's two hospitals, with severe brain injury. An intracranial catheter with a thermistor was used to continuously measure TB and other parameters. The TB's measurements, and simultaneously one or more of TBL, TFA, TEC, and TA, were recorded every 1 h.To create TB predicting models, the data of each measurement was separated into (a) model sample (measurements' 80%) and (b) validation sample (measurements' 20%). Multivariate linear regression analysis demonstrated that it is possible to predict brain's temperature (PrTB), using independent variables (R2 was TBL = 0.73, TFA = 0.80, TEC = 0.27, and TA = 0.17, p < 0.05). Significant linear associations were found, statistically, and no difference in means between TB and PrTB of each prediction model. Also, the 95% limits of agreement and the percent coefficient of variation showed sufficient agreement between the TB and PrTB in each prediction model.In conclusion, brain's temperature prediction models based on TBL, TFA, TEC, and TA were successful. Its determination contributes to the improvement of clinical decision-making.

Insight into the use of tympanic temperature during target temperature management in emergency and critical care: a scoping review

BACKGROUND

Target temperature management (TTM) is suggested to reduce brain damage in the presence of global or local ischemia. Prompt TTM application may help to improve outcomes, but it is often hindered by technical problems, mainly related to the portability of cooling devices and temperature monitoring systems. Tympanic temperature (T_Ty) measurement may represent a practical, non-invasive approach for core temperature monitoring in emergency settings, but its accuracy under different TTM protocols is poorly characterized. The present scoping review aimed to collect the available evidence about T_Ty monitoring in TTM to describe the technique diffusion in various TTM contexts and its accuracy in comparison with other body sites under different cooling protocols and clinical conditions.

METHODS

The scoping review was conducted following the guidelines of the Preferred Reporting Items for Systematic Review and Meta-Analysis extension for scoping reviews (PRISMA-ScR). PubMed, Scopus, and Web of Science electronic databases were systematically searched to identify studies conducted in the last 20 years, where T_Ty was measured in TTM context with specific focus on pre-hospital or in-hospital emergency settings.

RESULTS

The systematic search identified 35 studies, 12 performing T_Ty measurements during TTM in healthy subjects, 17 in patients with acute cardiovascular events, and 6 in patients with acute neurological diseases. The studies showed that T_Ty was able to track temperature changes induced by either local or whole-body cooling approaches in both pre-hospital and in-hospital settings. Direct comparisons to other core temperature measurements from other body sites were available in 22 studies, which showed a faster and larger change of T_Ty upon TTM compared to other core temperature measurements. Direct brain temperature measurements were available only in 3 studies and showed a good correlation between T_Ty and brain temperature, although T_Ty displayed a tendency to overestimate cooling effects compared to brain temperature.

CONCLUSIONS

T_Ty was capable to track temperature changes under a variety of TTM protocols and clinical conditions in both pre-hospital and in-hospital settings. Due to the heterogeneity and paucity of comparative temperature data, future studies are needed to fully elucidate the advantages of T_Ty in emergency settings and its capability to track brain temperature.

Measuring Core Body Temperature Using a Non-invasive, Disposable Double-Sensor During Targeted Temperature Management in Post-cardiac Arrest Patients

Background: Precisely measuring the core body temperature during targeted temperature management after return of spontaneous circulation is mandatory, as deviations from the recommended temperature might result in side effects such as electrolyte imbalances or infections. However, previous methods are invasive and lack easy handling. A disposable, non-invasive temperature sensor using the heat flux approach (Double Sensor), was tested against the standard method: an esophagus thermometer.

Methods: The sensor was placed on the forehead of adult patients (n = 25, M/F, median age 61 years) with return of spontaneous circulation after cardiac arrest undergoing targeted temperature management. The recorded temperatures were compared to the established measurement method of an esophageal thermometer. A paired t-test was performed to examine differences between methods. A Bland-Altman-Plot and the intraclass correlation coefficient were used to assess agreement and reliability. To rule out possible influence on measurements, the patients' medication was recorded as well.

Results: Over the span of 1 year and 3 months, data from 25 patients were recorded. The t-test showed no significant difference between the two measuring methods (t = 1.47, p = 0.14, n = 1,319). Bland-Altman results showed a mean bias of 0.02°C (95% confidence interval 0.00–0.04) and 95% limits of agreement of −1.023°C and 1.066°C. The intraclass correlation coefficient was 0.94. No skin irritation or allergic reaction was observed where the sensor was placed. In six patients the bias differed noticeably from the rest of the participants, but no sex-based or ethnicity-based differences could be identified. Influences on the measurements of the Double Sensor by drugs administered could also be ruled out.

Conclusions: This study could demonstrate that measuring the core body temperature with the non-invasive, disposable sensor shows excellent reliability during targeted temperature management after survived cardiac arrest. Nonetheless, clinical research concerning the implementation of the sensor in other fields of application should be supported, as well as verifying our results by a larger patient cohort to possibly improve the limits of agreement.

Incidence of postoperative shivering decreased with the use of acetaminophen: a propensity score matching analysis

OBJECTIVES

The incidence of postoperative shivering is known to be inversely associated with core body temperature. However, previous studies have pointed out that the threshold of shivering could be affected by peripheral temperature or anesthetic agents. These reports pointed specific drugs, though, anesthesia techniques have since advanced considerably. This study aimed to investigate factors associated with postoperative shivering in the context of the current body warming practice.

METHODS

The institutional clinical research ethics committee of Kyushu University approved the study protocol (IRB Clinical Research number 2019-233). This retrospective study involved 340 patients who had undergone radical surgery for gynecological cancer treatment under general anesthesia at our center from December 2012 to June 2019. Logistic regression analysis was performed to estimate the odds ratio (OR) for the incidence of postoperative shivering.

RESULTS

Postoperative shivering developed in 109 out of 340 patients. After multivariate-adjusted logistic regression, the incidences of postoperative shivering decreased significantly with increasing patient age (OR = 0.96; 95%CI: 0.93-0.98; p = 0.0004). Volatile anesthesia technique was less inclined to shiver after surgery than TIVA (OR = 0.55; 95%CI: 0.30-0.99; p = 0.04). Acetaminophen was much less used in the shivering group than in the non-shivering group (OR = 0.49; 95%CI: 0.25-0.94; p = 0.03).

CONCLUSIONS

This study indicated that the development of shivering in patients receiving the anesthetic technique currently used in our hospital was associated with use of acetaminophen or volatile agents, and patient age.

Skin temperature maps as a measure of carotid artery stenosis

In this study, the effect of carotid artery stenosis on the neck skin temperature maps was investigated. With the presence of stenosis, alterations in the carotid artery hemodynamics bring about changes in the heat transfer to the surrounding tissue. This is expected to be captured in the resulting temperature map over the external neck skin surface; possibly it correlates to the presence of stenosis. A total of twenty carotid artery samples, from ten patients with both sides normal (0% stenosis), stenosis (>50%) on one side, and stenosis (>50%) on both sides, were studied. Duplex Ultrasound and infrared (IR) thermography examinations were performed. A computational study, on an ideal 3-dimensional (3D) carotid artery and jugular vein model encapsulated with a solid neck tissue phantom resembling the human neck, was carried out. Incorporating the patient-specific geometrical (depth of artery and stenosis) and flow (peak systolic and end diastolic inlet velocity) boundary conditions, conjugate bio-heat transfer was studied using a finite volume numerical scheme. Simulation results and in-vivo thermal maps show that the average temperature on the external neck skin surface is significantly higher for normal patients (32.82 ± 0.53 °C versus 32.00 ± 0.37 °C, p < 0.001). Furthermore, the thermal region of interests (TROIs) were extracted from the in-vivo thermal images, which both qualitatively and quantitatively distinguish the normal and diseased cases. This study suggests the potential of thermal feature-based screening of patients with carotid artery stenosis.

Selective brain hypothermia: feasibility and safety study of a novel method in five patients

BACKGROUND/OBJECTIVE

Reduction of brain temperature remains the most common method of neuroprotection against ischemic injury employed during cardiac surgery. However, cooling delivered via the cardiopulmonary bypass circuit is brief and cooling the body core along with the brain has been associated with a variety of unwanted effects. This study investigated the feasibility and safety of a novel selective brain cooling approach to induce rapid, brain-targeted hypothermia independent of the cardiopulmonary bypass circuit.

METHODS

This first-in-human feasibility study enrolled five adults undergoing aortic valve replacement with cardiopulmonary bypass support. During surgery, the NeuroSave system circulated chilled saline within the pharynx and upper esophagus. Brain and body core temperature were continuously monitored. Adverse effects, cardiopulmonary function, and device function were noted.

RESULTS

Patient 1 received cooling fluid for an insignificant period, and Patients 2-5 successfully underwent the cooling procedure using the NeuroSave system for 56-89 minutes. Cooling fluid was 12°C for Patients 1-3, 6°C for Patient 4, and 2°C for Patient 5. There were no NeuroSave-related adverse events and no alterations in cardiopulmonary function during NeuroSave use. Brain temperature decreased by 3°C within 15 minutes and remained at least 3.5°C colder than the body core. During a brief episode of hypotension in one patient, the brain cooled an additional 4°C in 2 minutes, briefly reaching 27.4°C.

CONCLUSION

The NeuroSave system can induce rapid brain-targeted hypothermia and simultaneously maintain a favorable body-brain temperature gradient, even during hypotension. Further studies are required to evaluate the function of the system during longer periods of use.

Comparison of the WarmCloud and Bair Hugger Warming Devices for the Prevention of Intraoperative Hypothermia in Patients Undergoing Orthotopic Liver Transplantation: A Randomized Clinical Trial

BACKGROUND

The avoidance of hypothermia is vital during prolonged and open surgery to improve patient outcomes. Hypothermia is particularly common during orthotopic liver transplantation (OLT) and associated with undesirable physiological effects that can adversely impact on perioperative morbidity. The KanMed WarmCloud (Bromma, Sweden) is a revolutionary, closed-loop, warm-air heating mattress developed to maintain normothermia and prevent pressure sores during major surgery. The clinical effectiveness of the WarmCloud device during OLT is unknown. Therefore, we conducted a randomized controlled trial to determine whether the WarmCloud device reduces hypothermia and prevents pressure injuries compared with the Bair Hugger underbody warming device.

METHODS

Patients were randomly allocated to receive either the WarmCloud or Bair Hugger warming device. Both groups also received other routine standardized multimodal thermoregulatory strategies. Temperatures were recorded by nasopharyngeal temperature probe at set time points during surgery. The primary endpoint was nasopharyngeal temperature recorded 5 minutes before reperfusion. Secondary endpoints included changes in temperature over the predefined intraoperative time points, number of patients whose nadir temperature was below 35.5°C and the development of pressure injuries during surgery.

RESULTS

Twenty-six patients were recruited with 13 patients randomized to each group. One patient from the WarmCloud group was excluded because of a protocol violation. Baseline characteristics were similar. The mean (standard deviation) temperature before reperfusion was 36.0°C (0.7) in the WarmCloud group versus 36.3°C (0.6) in the Bairhugger group (P = 0.25). There were no statistical differences between the groups for any of the secondary endpoints.

CONCLUSIONS

When combined with standardized multimodal thermoregulatory strategies, the WarmCloud device does not reduce hypothermia compared with the Bair Hugger device in patients undergoing OLT.

Is Esophageal Temperature Better to Estimate Brain Temperature during Target Temperature Management in a Porcine Model of Cardiopulmonary Resuscitation?

Brain temperature monitoring is important in target temperature management for comatose survivors after cardiac arrest. Since acquisition of brain temperature is invasive and unrealistic in scene of resuscitation, we tried to sought out surrogate sites of temperature measurements that can precisely reflect cerebral temperature. Therefore, we designed this controlled, randomized animal study to investigate whether esophageal temperature can better predict brain temperature in two different hypothermia protocols. The results indicated that esophageal temperature had a stronger correlation with brain temperature in the early phase of hypothermia in both whole and regional body cooling protocols. It means that esophageal temperature was considered as priority method for early monitoring once hypothermia is initiated. This clinical significance of this study is as follows. Since resuscitated patients have unstable hemodynamics, collecting temperature data from esophagus probe is cost-efficient and easier than the catheter in central vein. Moreover, it can prevent the risk of iatrogenic infection comparing with deep vein catheterization, especially in survivors with transient immunoexpressing in hypothermia protocol.

Normothermia in Arthroplasty

BACKGROUND

Since the initial design of surgical theatres, the thermal environment of the operating suite itself has been an area of concern and robust discussion. In the 1950s, correspondence in the British Medical Journal discussed the most suitable design for a surgeon's cap to prevent sweat from dripping onto the surgical field. These deliberations stimulated questions about the effects of sweat-provoking environments on the efficiency of the surgical team, not to mention the effects on the patient. Although these benefits translate to implant-based orthopedic surgery, they remain poorly understood and, at times, ignored.

METHODS

A review and synthesis of the body of literature on the topic of maintenance of normothermia was performed.

RESULTS

Maintenance of normothermia in orthopedic surgery has been proven to have broad implications from bench top to bedside. Normothermia has been shown to impact everything from nitrogen loss and catabolism after hip fracture surgery to infection rates after elective arthroplasty.

CONCLUSION

Given both the physiologic impact this has on patients, as well as a change in the medicolegal environment around this topic, a general understanding of these concepts should be invaluable to all surgeons.

Prevention of hypothermia in patients undergoing orthotopic liver transplantation using the humigard® open surgery humidification system: a prospective randomized pilot and feasibility clinical trial

Background

Perioperative thermal disturbances during orthotopic liver transplantation (OLT) are common. We hypothesized that in patients undergoing OLT the use of a humidified high flow CO₂ warming system maintains higher intraoperative temperatures when compared to standardized multimodal strategies to maintain thermoregulatory homeostasis.

Methods

We performed a randomized pilot study in adult patients undergoing primary OLT. Participants were randomized to receive either open wound humidification with a high flow CO₂ warming system in addition to standard care (Humidification group) or to standard care alone (Control group). The primary end point was nasopharyngeal core temperature measured 5 min immediately prior to reperfusion of the donor liver (Stage 3 − 5 min). Secondary endpoints included intraoperative PaCO₂, minute ventilation and the use of vasoconstrictors.

Results

Eleven patients were randomized to each group. Both groups were similar for age, body mass index, MELD, SOFA and APACHE II scores, baseline temperature, and duration of surgery. Immediately prior to reperfusion (Stage 3 − 5 min) the mean (SD) core temperature was higher in the Humidification Group compared to the Control Group: 36.0 °C (0.13) vs. 35.4 °C (0.22), p = 0.028. Repeated measured ANOVA showed that core temperatures over time during the stages of the transplant were higher in the Humidification Group compared to the Control Group (p < 0.0001). There were no significant differences in the ETCO₂, PaCO₂, minute ventilation, or inotropic support.

Conclusion

The humidified high flow CO₂ warming system was superior to standardized multimodal strategies in maintaining normothermia in patients undergoing OLT. Use of the device was feasible and did not interfere with any aspects of surgery. A larger study is needed to investigate if the improved thermoregulation observed is associated with improved patient outcomes.

Trial registration

ACTRN12616001631493. Retrospectively registered 25 November 2016.

Accuracy and precision of four common peripheral temperature measurement methods in intensive care patients

INTRODUCTION

An accurate determination of body temperature in critically ill patients is a fundamental requirement for initiating the proper process of diagnosis, and also therapeutic actions; therefore, the aim of the study was to assess the accuracy and precision of four noninvasive peripheral methods of temperature measurement compared to the central nasopharyngeal measurement.

METHODS

In this observational prospective study, 237 patients were recruited from the intensive care unit of Imam Ali Hospital of Kermanshah. The patients' body temperatures were measured by four peripheral methods; oral, axillary, tympanic, and forehead along with a standard central nasopharyngeal measurement. After data collection, the results were analyzed by paired t-test, kappa coefficient, receiver operating characteristic curve, and using Statistical Package for the Social Sciences, version 19, software.

RESULTS

There was a significant meaningful correlation between all the peripheral methods when compared with the central measurement (P<0.001). Kappa coefficients showed good agreement between the temperatures of right and left tympanic membranes and the standard central nasopharyngeal measurement (88%). Paired t-test demonstrated an acceptable precision with forehead (P=0.132), left (P=0.18) and right (P=0.318) tympanic membranes, oral (P=1.00), and axillary (P=1.00) methods. Sensitivity and specificity of both the left and right tympanic membranes were more than for other methods.

CONCLUSION

The tympanic and forehead methods had the highest and lowest accuracy for measuring body temperature, respectively. It is recommended to use the tympanic method (right and left) for assessing a patient's body temperature in the intensive care units because of high accuracy and acceptable precision.

Evaluation of skin temperature over carotid artery for temperature monitoring in comparison to nasopharyngeal temperature in adults under general anesthesia

BACKGROUND

Thermoregulation is markedly affected in patients undergoing surgical procedures under anesthesia. Monitoring of temperature is very important during such conditions. Skin temperature is one of the easy and noninvasive ways of temperature monitoring. Common skin temperature monitoring sites are unreliable and did not correlate to the core temperature measurement.

AIM

To compare and study the correlation of skin temperature over carotid artery in the neck to that of simultaneously measured nasopharyngeal temperature in adult patients undergoing surgical procedures under general anesthesia.

SETTINGS AND DESIGN

Prospective double-blinded study in a Tertiary Care Center.

MATERIALS AND METHODS

Ninety-seven consecutive American Society of Anesthesiologists I-II patients of age 18-40 years posted for elective surgical procedures under general anesthesia were included. Two temperature sites are monitored: The skin temperature over the carotid artery in the neck with a skin temperature probe T (skin-carotid) and the nasopharyngeal temperature T (naso) with another nasopharyngeal probe. The temperature readings are taken at 0, 15, 30, 45, and 60 min after induction of general anesthesia.

STATISTICAL ANALYSIS

Paired t-test, Pearson correlation and Bland-Altman analysis for the rate of agreement.

RESULTS

The skin over the carotid artery in the neck showed statistically significant lower values than simultaneously measured nasopharyngeal temperature. This comparison is done with paired t-test at P< 0.05 significance. Bland-Altman plots showed good agreement between the two sites of temperature measurement.

CONCLUSION

This study has shown that the skin temperature over the carotid artery in the neck was strongly correlated to the nasopharyngeal temperature in adult patients undergoing surgical procedures under general anesthesia.

Novel Zero-Heat-Flux Deep Body Temperature Measurement in Lower Extremity Vascular and Cardiac Surgery

OBJECTIVE

The aim of this study was to compare deep body temperature obtained using a novel noninvasive continuous zero-heat-flux temperature measurement system with core temperatures obtained using conventional methods.

DESIGN

A prospective, observational study.

SETTING

Operating room of a university hospital.

PARTICIPANTS

The study comprised 15 patients undergoing vascular surgery of the lower extremities and 15 patients undergoing cardiac surgery with cardiopulmonary bypass.

INTERVENTIONS

Zero-heat-flux thermometry on the forehead and standard core temperature measurements.

MEASUREMENTS AND MAIN RESULTS

Body temperature was measured using a new thermometry system (SpotOn; 3M, St. Paul, MN) on the forehead and with conventional methods in the esophagus during vascular surgery (n = 15), and in the nasopharynx and pulmonary artery during cardiac surgery (n = 15). The agreement between SpotOn and the conventional methods was assessed using the Bland-Altman random-effects approach for repeated measures. The mean difference between SpotOn and the esophageal temperature during vascular surgery was+0.08°C (95% limit of agreement -0.25 to+0.40°C). During cardiac surgery, during off CPB, the mean difference between SpotOn and the pulmonary arterial temperature was -0.05°C (95% limits of agreement -0.56 to+0.47°C). Throughout cardiac surgery (on and off CPB), the mean difference between SpotOn and the nasopharyngeal temperature was -0.12°C (95% limits of agreement -0.94 to+0.71°C). Poor agreement between the SpotOn and nasopharyngeal temperatures was detected in hypothermia below approximately 32°C.

CONCLUSIONS

According to this preliminary study, the deep body temperature measured using the zero-heat-flux system was in good agreement with standard core temperatures during lower extremity vascular and cardiac surgery. However, agreement was questionable during hypothermia below 32°C.

Targeted temperature management: Current evidence and practices in critical care

Targeted temperature management (TTM) in today's modern era, especially in intensive care units represents a promising multifaceted therapy for a variety of conditions. Though hypothermia is being used since Hippocratic era, the renewed interest of late has been since early 21^st century. There have been multiple advancements in this field and varieties of cooling devices are available at present. TTM requires careful titration of its depth, duration and rewarming as it is associated with side-effects. The purpose of this review is to find out the best evidence-based clinical practice criteria of therapeutic hypothermia in critical care settings. TTM is an unique therapeutic modality for salvaging neurological tissue viability in critically ill patients viz. Post-cardiac arrest, traumatic brain injury (TBI), meningitis, acute liver failure and stroke. TTM is standard of care in post-cardiac arrest situations; there has been a lot of controversy of late regarding temperature ranges to be used for the same. In patients with TBI, it reduces intracranial pressure, but has not shown any favorable neurologic outcome. Hypothermia is generally accepted treatment for hypoxic ischemic encephalopathy in newborns. The current available technology to induce and maintain hypothermia allows for precise temperature control. Future studies should focus on optimizing hypothermic treatment to full benefit of our patients and its application in other clinical scenarios.

Oxide nanomembrane hybrids with enhanced mechano- and thermo-sensitivity for semitransparent epidermal electronics

Oxide nanomembrane hybrids with enhanced mechano- and thermo-sensitivity for semitransparent epidermal electronics are developed. The use of nanomaterials (single wall nanotubes and silver nanoparticles) embedded in the oxide nanomembranes significantly enhances mechanical and thermal sensitivities. These mechanical and thermal sensors are utilized in wheelchair control and hypothermia detection, which are useful for patients with strokes.

Induction of cooling with a passive head and neck cooling device: effects on brain temperature after stroke

BACKGROUND AND PURPOSE

Therapeutic hypothermia improves clinical outcome after cardiac arrest and appears beneficial in other cerebrovascular diseases. We conducted this study to investigate the relationship between surface head/neck cooling and brain temperature.

METHODS

Prospective observational study enrolling consecutive patients with severe ischemic or hemorrhagic stroke undergoing intracranial pressure (ICP) and brain temperature monitoring. Arterial pressure, ICP, cerebral perfusion pressure, heart rate, brain, tympanic, and bladder temperature were continuously registered. Fifty-one applications of the Sovika cooling device were analyzed in 11 individual patients.

RESULTS

Sovika application led to a significant decrease of brain temperature compared with baseline with a maximum of -0.36°C (SD, 0.22) after 49 minutes (SD, 17). During cooling, dynamics of brain temperature differed significantly from bladder (-0.25°C [SD, 0.15] after 48 minutes [SD, 19]) and tympanic temperature (-1.79°C [SD, 1.19] after 37 minutes [SD, 16]). Treatment led to an increase in systolic arterial pressure by >20 mm Hg in 14 applications (n=7 patients) resulting in severe hypertension (>180 mm Hg) in 4 applications (n=3). ICP increased by >10 mm Hg in 7 applications (n=3), led to ICP crisis >20 mm Hg in 6 applications (n=3), and a drop of cerebral perfusion pressure <50 mm Hg in 1 application.

CONCLUSIONS

Although the decrease of brain temperature after Sovika cooling device application was statistically significant, we doubt clinical relevance of this rather limited effect (-0.36°C). Moreover, the transient increases of blood pressure and ICP warrant caution.

Femoro-iliacal artery versus pulmonary artery core temperature measurement during therapeutic hypothermia: an observational study

AIM OF THE STUDY

Therapeutic hypothermia after cardiac arrest improves neurologic outcome. The temperature measured in the pulmonary artery is considered to best reflect core temperature, yet is limited by invasiveness. Recently a femoro-arterial thermodilution catheter (PiCCO-Pulse Contour Cardiac Output) has been introduced in clinical practice as a safe and accurate haemodynamic monitoring system, which is also able to measure blood temperature. The aim of the study was to investigate, if the temperature measured with the PiCCO catheter reflects pulmonary artery temperature better than other sites during therapeutic hypothermia.

METHODS

In this observational study twenty patients after cardiac arrest and successful resuscitation were cooled with various cooling methods to 33 ± 1°C for 24h, followed by rewarming. Temperatures were recorded continuously in the pulmonary artery (Tpa), femoro-iliacal artery (Tpicco), ear canal (Tear), oesophagus (Toeso) and urinary bladder (Tbla). We assessed agreement of methods using the Bland Altman approach including bias and limits of agreement (LA).

RESULTS

All other sites differed significantly from Tpa with the bias varying from 0.4°C (Tbla) to -0.6°C (Tear). Standard deviations varied from 0.1°C (Tpicco, Toeso) to 0.5°C (Tear). For all sites bias was closer to zero with increasing average temperatures. Bias tended to be larger in the cooling phase compared to overall measurements.

CONCLUSIONS

Temperature measurement in the femoro-iliacal artery (Tpicco) reflects the gold standard of pulmonary artery temperature most accurately, especially during the cooling phase. Tpicco is easily accessible and might be used for monitoring core temperature without the need for additional temperature probes.

Postresuscitation care

Caring in the emergency department for the patient with return of spontaneous circulation after cardiac arrest is challenging. A coordinated and systematic approach to post-cardiac arrest care can improve the mortality and the chance of meaningful neurologic recovery. By achieving appropriate targets for oxygenation, ventilation, and hemodynamic parameters, along with initiating therapeutic hypothermia and arranging early percutaneous coronary intervention, the emergency physician can have the most significant impact on patients who have just been revived from death.

Early selective trans-nasal cooling during CPR improves success of resuscitation in a porcine model of prolonged pulseless electrical activity cardiac arrest

AIM OF STUDY

In the present study, we investigated trans-nasal cooling in settings of pulseless electrical activity (PEA). We hypothesized that early trans-nasal cooling during CPR improves outcomes when cardiac arrest is associated with PEA.

METHODS

Ventricular fibrillation (VF) was electrically induced in 16 domestic male pigs weighing 40±3 kg. After 14 min of untreated VF, PEA was induced following delivery of one or more electrical shocks. One min after onset of PEA, CPR was started, including chest compression and ventilation. Each animal received 5 min of CPR prior to defibrillation attempt. CPR and resuscitation efforts were discontinued at 15 min unless return to spontaneous circulation was achieved. In 8 animals, selective trans-nasal cooling was begun coincident with start of CPR and 8 randomized controls were identically treated except for trans-nasal cooling. Mean aortic pressure was continuously measured together with aortic and right atrial pressure and nasal, body and right jugular vein temperatures. Coronary perfusion pressure (CPP) was computed from measured data.

RESULTS

Six of eight animals were resuscitated after early trans-nasal cooling, while only one untreated control was resuscitated (p=0.012). Nasal, body and jugular vein temperatures decreased after cooling. At PC (precordial compression) 5 min, the cooled group recorded a higher CPP (25±5 mmHg) than the non-cooled group (15±4 mmHg, p=0.001).

CONCLUSION

When selective trans-nasal cooling was initiated during CPR in the animal model of prolonged cardiac arrest with PEA, CPP was higher and the likelihood of return of spontaneous circulation was improved.

[Type A dissection. Principles of anesthesiological management]

Acute type A dissection is among the most dangerous of vascular diseases and is associated with a high lethality. Surgery for type A dissection is a complex procedure which is accompanied by relevant blood losses and severe deterioration of the coagulation system. Either due to the dissection or the surgical procedure, perfusion of affected organs can be diminished or completely disrupted with the risk of irreversible organ damage especially in the brain. Perioperative anesthesiological management for type A dissection is demanding and involves maintaining hemodynamic stability, surveillance of cerebral oxygenation and transesophageal echocardiographical diagnostic support for the decision-making of the most appropriate surgical approach. Furthermore, reestablishment of sufficient hemostasis can be challenging and requires thorough understanding of the relevant aspects affecting normal hemostasis during surgical repair of aortic dissection. In this article relevant pathophysiological aspects and basic principles of anesthesiological management of type A dissection are described.

A comparison between head cooling begun during cardiopulmonary resuscitation and surface cooling after resuscitation in a pig model of cardiac arrest

OBJECTIVE

Employing transnasal head-cooling in a pig model of prolonged ventricular fibrillation, we compared the effects of 4 hrs of head-cooling started during cardiopulmonary resuscitation with those of 8 hrs of surface-cooling started at 2 hrs after resuscitation on 96-hr survival and neurologic outcomes.

DESIGN

Prospective controlled animal study.

SETTING

University-affiliated research laboratory.

SUBJECTS

Domestic pigs.

INTERVENTIONS

Twenty-four male pigs were subjected to 10 min of untreated ventricular fibrillation followed by 5 min of cardiopulmonary resuscitation. In the head-cooling group, hypothermia was started with cardiopulmonary resuscitation and continued for 4 hrs after resuscitation. In the surface-cooling group, systemic hypothermia with a cooling blanket was started, in accord with current clinical practices, at 2 hrs after resuscitation and continued for 8 hrs. Methods in the control animal studies were identical except for temperature interventions.

MEASUREMENTS AND MAIN RESULTS

All animals were resuscitated except for one animal in each of the surface-cooling and control groups. After 5 min of cardiopulmonary resuscitation, jugular vein temperature was significantly decreased in the head-cooled animals. However, there were no differences in pulmonary artery temperatures among the three groups at that time. Nevertheless, both head-cooled and surface-cooled animals had an improved 96-hr survival after resuscitation. Significantly better neurologic outcomes were observed in early head-cooled animals in the first 3 days after resuscitation.

CONCLUSION

Early head-cooling during cardiopulmonary resuscitation continuing for 4 hrs after resuscitation produced favorable survival and neurologic outcomes in comparison with delayed surface-cooling of 8 hrs duration.

Survival and neurological outcomes after nasopharyngeal cooling or peripheral vein cold saline infusion initiated during cardiopulmonary resuscitation in a porcine model of prolonged cardiac arrest

OBJECTIVE

We have previously demonstrated that nasopharyngeal cooling initiated during cardiopulmonary resuscitation improves the success of resuscitation. In this study, we compared the effects of nasopharyngeal cooling with cold saline infusion initiated during cardiopulmonary resuscitation on resuscitation outcome in a porcine model of prolonged cardiac arrest. We hypothesized that nasopharyngeal cooling initiated during cardiopulmonary resuscitation would yield better resuscitation outcome when compared with cold saline infusion.

DESIGN

Randomized, prospective animal study.

SETTING

University-affiliated research laboratory.

SUBJECTS

Yorkshire-X domestic pigs (Sus scrofa).

INTERVENTIONS

Ventricular fibrillation was induced in 14 pigs weighing 38 +/- 2 kg. After 15 mins of untreated ventricular fibrillation, cardiopulmonary resuscitation was performed for 5 mins before defibrillation. Coincident with the start of cardiopulmonary resuscitation, animals were randomly assigned to receive nasopharyngeal cooling with the aid of the RhinoChill Device (BeneChill, San Diego, CA) or cold saline infusion with 30 mL/kg 4 degrees C saline. One hour after restoration of spontaneous circulation, surface cooling was begun with the aid of a water blanket in both groups and maintained for 4 hrs.

MEASUREMENTS AND MAIN RESULTS

Jugular vein temperature significantly decreased in animals subjected to nasopharyngeal cooling in comparison with those receiving cold saline infusion (p < .01). Core temperature, however, decreased only in animals receiving cold saline infusion (p < .01). Coronary perfusion pressure was significantly higher in the animals treated with nasopharyngeal cooling (p = .02). All seven animals treated with nasopharyngeal cooling were successfully resuscitated in contrast to only two animals resuscitated in the cold saline infusion group (p = .02).

CONCLUSION

In this model, nasopharyngeal cooling initiated during cardiopulmonary resuscitation improved the success of resuscitation compared to cooling with cold saline infusion.

Prehospital therapeutic hypothermia for comatose survivors of cardiac arrest: a randomized controlled trial

BACKGROUND

Intravenous infusion of ice-cold fluid is considered a feasible method to induce mild therapeutic hypothermia in cardiac arrest survivors. However, only one randomized controlled trial evaluating this treatment exists. Furthermore, the implementation rate of prehospital cooling is low. The aim of this study was to evaluate the efficacy and safety of this method in comparison with conventional therapy with spontaneous cooling often observed in prehospital patients.

METHODS

A randomized controlled trial was conducted in a physician-staffed helicopter emergency medical service. After successful initial resuscitation, patients were randomized to receive either +4 degrees C Ringer's solution with a target temperature of 33 degrees C or conventional fluid therapy. As an endpoint, nasopharyngeal temperature was recorded at the time of hospital admission.

RESULTS

Out of 44 screened patients, 19 were analysed in the treatment group and 18 in the control group. The two groups were comparable in terms of baseline characteristics. The core temperature was markedly lower in the hypothermia group at the time of hospital admission (34.1+/-0.9 degrees C vs. 35.2+/-0.8 degrees C, P<0.001) after a comparable duration of transportation. Otherwise, there were no significant differences between the groups regarding safety or secondary outcome measures such as neurological outcome and mortality.

CONCLUSION

Spontaneous cooling alone is insufficient to induce therapeutic hypothermia before hospital admission. Infusion of ice-cold fluid after return of spontaneous circulation was found to be well tolerated and effective. This method of cooling should be considered as an important first link in the 'cold chain' of prehospital comatose cardiac arrest survivors.

Perioperative hypothermia: use and therapeutic implications

Perioperative cerebral ischemic insults are common in some surgical procedures. The notion that induced hypothermia can be employed to improve outcome in surgical patients has persisted for six decades. Its principal application has been in the context of cardiothoracic and neurosurgery. Mild (32-35 degrees C) and moderate (26-31 degrees C) hypothermia have been utilized for numerous procedures involving the heart, but intensive research has found little or no benefit to outcome. This may, in part, be attributable to confounding effects associated with rewarming and lack of understanding of the mechanisms of injury. Evidence of efficacy of mild hypothermia is absent for cerebral aneurysm clipping and carotid endarterectomy. Deep hypothermia (18-25 degrees C) during circulatory arrest has been practiced in the repair of congenital heart disease, adult thoracic aortas, and giant intracranial aneurysms. There is little doubt of the protective efficacy of deep hypothermia, but continued efforts to refine its application may serve to enhance its utility. Recent evidence that mild hypothermia is efficacious in out-of-hospital cardiac arrest has implications for patients incurring anoxic or global ischemic brain insults during anesthesia and surgery, or perioperatively. Advances in preclinical models of ischemic/anoxic injury and cardiopulmonary bypass that allow definition of optimal cooling strategies and study of cellular and subcellular events during perioperative ischemia can add to our understanding of mechanisms of hypothermia efficacy and provide a rationale basis for its implementation in humans.

Therapeutic hypothermia and controlled normothermia in the intensive care unit: practical considerations, side effects, and cooling methods

BACKGROUND

Hypothermia is being used with increasing frequency to prevent or mitigate various types of neurologic injury. In addition, symptomatic fever control is becoming an increasingly accepted goal of therapy in patients with neurocritical illness. However, effectively controlling fever and inducing hypothermia poses special challenges to the intensive care unit team and others involved in the care of critically ill patients.

OBJECTIVE

To discuss practical aspects and pitfalls of therapeutic temperature management in critically ill patients, and to review the currently available cooling methods.

DESIGN

Review article.

INTERVENTIONS

None.

MAIN RESULTS

Cooling can be divided into three distinct phases: induction, maintenance, and rewarming. Each has its own risks and management problems. A number of cooling devices that have reached the market in recent years enable reliable maintenance and slow and controlled rewarming. In the induction phase, rapid cooling rates can be achieved by combining cold fluid infusion (1500-3000 mL 4 degrees C saline or Ringer's lactate) with an invasive or surface cooling device. Rapid induction decreases the risks and consequences of short-term side effects, such as shivering and metabolic disorders. Cardiovascular effects include bradycardia and a rise in blood pressure. Hypothermia's effect on myocardial contractility is variable (depending on heart rate and filling pressure); in most patients myocardial contractility will increase, although mild diastolic dysfunction can develop in some patients. A risk of clinically significant arrhythmias occurs only if core temperature decreases below 30 degrees C. The most important long-term side effects of hypothermia are infections (usually of the respiratory tract or wounds) and bedsores.

CONCLUSIONS

Temperature management and hypothermia induction are gaining importance in critical care medicine. Intensive care unit physicians, critical care nurses, and others (emergency physicians, neurologists, and cardiologists) should be familiar with the physiologic effects, current indications, techniques, complications and practical issues of temperature management, and induced hypothermia. In experienced hands the technique is safe and highly effective.