Early Rewarming Research Articles

Abstract 316: Reperfusion With Mild versus Moderate Hypothermia in a Swine Model of Extracorporeal Cardiopulmonary Resuscitation

Background: Targeted temperature management (TTM) at lower temperatures has shown variable neuroprotective benefits in clinical trials of cardiac arrest. We hypothesized that moderate hypothermia at the time of VA-ECMO reperfusion followed by early rewarming would reduce brain injury in a swine model of refractory VF, compared to mild hypothermia. Methods: Fourteen female pigs had electrically induced VF and conventional CPR for 30 minutes. Animals were cannulated to VA-ECMO and randomized to TTM to 34°C for 4 hours (mild hypothermia, n=7) or 24°C for 1 hour followed by early rewarming to 34°C over 3 hours (moderate hypothermia, n=7). Cooling was initiated upon ECMO reperfusion by circulating ice water through the oxygenator. Brain temperature and cerebral and systemic hemodynamics were continuously monitored. After four hours of post-arrest and ECMO care, brain tissue was obtained for examination. Groups were compared using paired t- and Wilcoxon rank sum tests. Results: The mean time to target brain temperature was 5 and 35 minutes in the mild and moderate groups, respectively (Panel, A). CPR hemodynamics were similar. Carotid blood flow (CBF) was higher in moderate hypothermia animals (79.0±1.56 vs 60.7±1.86% pre-arrest baseline, P <0.001) throughout the post-arrest period. There were no differences in ECMO flow, mean arterial pressure, vasopressor/fluid requirement, bleeding, or thromboelastography. No significant difference in histologic damage score was observed between groups (10.5 [7, 11.8] vs 13 [9, 20], with 24°C vs 34°C respectively P =0.25; Panel, B). Immunohistochemistry markers for white matter and neuronal injury also did not significantly diverge. Conclusion: In a swine model of refractory cardiac arrest treated with ECPR, moderate hypothermia initiated upon reperfusion followed by early rewarming did not appear to be neuroprotective. Histological brain injury at 4 hours post-resuscitation was not affected by the degree of hypothermia.

The 'island technique' for aortic arch and FET surgery: an 'evergreen' or a 'rekindled flame'?

The 'island technique' for aortic arch and FET surgery: an 'evergreen' or a 'rekindled flame'?

Total arch replacement using a 4-branched vascular graft without circulatory arrest.

The technical essentials of the procedure include femoral artery cannulation, selective antegrade cerebral perfusion for brain protection, total arch replacement with a 4-branched vascular graft, implantation of the special open stented graft into the descending aorta, moderate hypothermic balloon occluding descending aorta at 25℃. This technique allows arch reconstruction to be debranched first and upper part of the body is perfused via the 4-branched vascular graft, ensuring antegrade true lumen cerebral perfusion rapidly secured, the descending aorta is arrested by balloon occluding and early rewarming and reperfusion after distal anastomosis to minimize organs ischemia.

Predictive value of early EEG for seizures in neonates with hypoxic-ischemic encephalopathy undergoing therapeutic hypothermia.

To assess the prognostic significance of an early normal/mildly abnormal conventional EEG (cEEG) on seizure risk in neonates undergoing therapeutic hypothermia. We reviewed the video-EEG recordings from a large cohort of neonates treated with therapeutic hypothermia for hypoxic-ischemic encephalopathy from 2008 to 2017 in a single tertiary center. Continuous video-EEG was started as soon as possible (median 8.2 h) and continued throughout hypothermia and rewarming. We studied those neonates with a normal/mildly abnormal EEG during the first 24 h of monitoring. A total of 331 neonates were treated with hypothermia and 323 had cEEG recordings available for review; 99 were excluded because of a moderately/severely abnormal cEEG background and/or seizure during the first 24 h of recording, and an additional eight because of early rewarming. The remaining 216 had a normal/mildly abnormal cEEG in the first 24 h. None of these patients subsequently developed seizures. A normal/mildly abnormal cEEG during the first 24 h indicates a very low risk of subsequent seizures. This suggests that cEEG monitoring can be safely discontinued after 24 h if it has remained normal or excessively discontinuous and no seizures are detected, limiting the need for this resource-intensive and expensive tool.

Mitochondrial Impairment as a Key Factor for the Lack of Attachment after Cold Storage of Hepatocyte Suspensions

Isolated primary hepatocytes, which are widely used for pharmacological and clinical purposes, usually undergo certain periods of cold storage in suspension during processing. While adherent hepatocytes were shown previously to suffer iron-dependent cell death during cold (4 °C) storage and early rewarming, we previously found little iron-dependent hepatocyte death in suspension but severely decreased attachment ability unless iron chelators were added. Here, we focus on the role of mitochondrial impairment in this nonattachment of hepatocyte suspensions. Rat hepatocyte suspensions were stored in a chloride-poor, glycine-containing cold storage solution with and without iron chelators at 4 °C. After 1 wk of cold storage in the basic cold storage solution, cell viability in suspension was unchanged, while cell attachment was decreased by >80%. In the stored cells, a loss of mitochondrial membrane potential (MMP), a decrease in adenosine triphosphate (ATP) content (2 ± 2 nmol/106 cells after cold storage, 5 ± 3 nmol/106 cells after rewarming vs. control 29 ± 6 nmol/106 cells), and a decrease in oxygen consumption (101 ± 59 pmol sec−1 per 106 cells after rewarming vs. control 232 ± 83 pmol sec−1 per 106 cells) were observed. Addition of iron chelators to the cold storage solution increased cell attachment to 53% ± 20% and protected against loss of MMP, and cells were able to partially regenerate ATP during rewarming (15 ± 10 nmol/106 cells). Increased attachment could also be achieved by addition of the inhibitor combination of mitochondrial permeability transition, trifluoperazine + fructose. Attached hepatocytes displayed normal MMP and mitochondrial morphology. Additional experiments with freshly isolated hepatocytes confirmed that impaired energy production—as elicited by an inhibitor of the respiratory chain, antimycin A—can decrease cell attachment without decreasing viability. Taken together, these results suggest that mitochondrial impairment with subsequent energy deficiency is a key factor for the lack of attachment of cold-stored hepatocyte suspensions.

Bone Scan in Evaluation of Bone Viability in Severe Frostbite of the Hand.

A 39-year-old male presented to the emergency department (ED) with frostbite to the fingers of both hands. In the ED, he received warm baths, acetylsalicylic acid, clopidogrel, and heparin. A three-phase bone scintigraphy with technetium-99m-methylene diphosphonate revealed absent radiotracer uptake in distal phalanges of both hands. The patient received acetylsalicylic acid, clopidogrel and wound care for the next 5 days and made an excellent recovery with satisfactory wound healing in both hands. Early rapid rewarming and reperfusion can improve the prognosis significantly and therefore bone scan done within first 1–2 days may give spurious results.

Hypothermia and Rewarming Activate a Macroglial Unfolded Protein Response Independent of Hypoxic-Ischemic Brain Injury in Neonatal Piglets

Therapeutic hypothermia provides incomplete neuroprotection after hypoxia-ischemia (HI)-induced brain injury in neonates. We previously showed that cortical neuron and white matter apoptosis are promoted by hypothermia and early rewarming in a piglet model of HI. The unfolded protein response (UPR) may be one of the potential mediators of this cell death. Here, neonatal piglets underwent HI or sham surgery followed by 29 h of normothermia, 2 h of normothermia + 27 h of hypothermia or 18 h of hypothermia + rewarming. Piglets recovered for 29 h. Immunohistochemistry for endoplasmic reticulum to nucleus signaling-1 protein (ERN1), a marker of UPR activation, was used to determine the ratios of ERN1+ macroglia and neurons in the motor subcortical white matter and cerebral cortex. The ERN1+ macroglia were immunophenotyped as oligodendrocytes and astrocytes by immunofluorescent colabeling. Temperature (p = 0.046) and HI (p < 0.001) independently affected the ratio of ERN1+ macroglia. In sham piglets, sustained hypothermia (p = 0.011) and rewarming (p = 0.004) increased the ERN1+ macroglia ratio above that in normothermia. HI prior to hypothermia diminished the UPR. Ratios of ERN1+ macroglia correlated with white matter apoptotic profile counts in shams (r = 0.472; p = 0.026), thereby associating UPR activation with white matter apoptosis during hypothermia and rewarming. Accordingly, macroglial cell counts decreased in shams that received sustained hypothermia (p = 0.009) or rewarming (p = 0.007) compared to those in normothermic shams. HI prior to hypothermia neutralized the macroglial cell loss. Neither HI nor temperature affected ERN1+ neuron ratios. In summary, delayed hypothermia and rewarming activate the macroglial UPR, which is associated with white matter apoptosis. HI may decrease the macroglial endoplasmic reticulum stress response after hypothermia and rewarming.

Clinical Analysis of Frostbite

Purpose: Frostbite can affect still soldiers. Initial clinical manifestations are similar for superficial and deep frostbite, so early treatment is identical. It is under-estimated by physicians. We try to identify the challenges of managing these complex tissue injuries. Methods: A retrospective analysis of 84 patients hospitalized at AFCH from 2009 to 2015 was conducted. We investigated differences of epidemiological characteristics, identification of soft tissue injury, treatment and complications between superficial (SF: 43; 51.2%) and deep (DF: 41; 48.8%) frostbite. Results: The major (94.0%) developed frostbite in dry circumstances (89.3%). Wet circumstances (66.7%) were more susceptible to DF rather than dry (46.7%). The 38 (45.2%) arrived to specialist within 7days. Most prone sites were feet, followed by hands. Toes had more deep injuries. DF presented more increased levels of ALT, CPK, CKMB, CRP. The bone scan of W+S+ was 48.3%, 87.1% and W+S- was 20.7%, 12.9%, respectively. The treatment resulted in improved or normalized perfusion scan with matching clinical improvement. It was a good tool to assess treatment response. Eighteen normal and 8 stenotic type of PCR resulted in normal with matching clinical improvement. One continuous obstructive waveform led to minor amputation. Twelve underwent both PCR and MRA. Among 6 normal PCR, 5 showed normal and one stenosis in MRA. All 5 stenosis and one obstruction showed the same findings in MRA. It was a good tool to evaluate vascular compromise. They were treated with rapid rewarming (11.6%, 22.0%), hydrotherapy (16.3%, 29.3%), respectively. Six (14.6%) underwent STSG, 2 (4.9%) had digital amputation in DF. Berasil, Ibuprofen, Trental were commonly administered. PGE1 was administered selectively for 6.8, 10.8 days, respectively. Raynaud’s syndrome (16.3%), CRPS (4.7%), LOM (14.6%) and toe deformity (4.9%) were specific sequelae. Conclusion: We should recommend intensive foot care education, early rewarming and evacuation to specialized units. The bone scanning and PCR should allow for a more aggressive and active approach to the management of tissue viability. [ J Trauma Inj 2015; 28: 158-169 ]

Sun's procedure for complex aortic arch repair: total arch replacement using a tetrafurcate graft with stented elephant trunk implantation.

The Sun's procedure is a surgical technique proposed by Dr. Li-Zhong Sun in 2002 that integrates total aortic arch replacement using a tetrafurcated graft with implantation of a specially designed frozen elephant trunk (Cronus(®)) in the descending aorta. It is used as a treatment option for extensive aortic dissections or aneurysms involving the ascending aorta, aortic arch and the descending aorta. The technical essentials of Sun's procedure include implantation of the special open stented graft into the descending aorta, total arch replacement with a 4-branched vascular graft, right axillary artery cannulation, selective antegrade cerebral perfusion for brain protection, moderate hypothermic circulatory arrest at 25 °C, a special anastomotic sequence for aortic reconstruction (i.e., proximal descending aorta → left carotid artery → ascending aorta → left subclavian artery → innominate artery), and early rewarming and reperfusion after distal anastomosis to minimize cerebral and cardiac ischemia. The core advantage of Sun's procedure lies in the use of a unique stented graft, which has superior technical simplicity, flexibility, inherent mechanical durability and an extra centimeter of attached regular vascular graft at both ends. Since its introduction in 2003, the Sun's procedure has produced satisfactory early and long-term results in over 8,000 patients in China and more than 200 patients in South American countries. In a series of 1,092 patients, the authors have achieved an in-hospital mortality rate of 6.27% (7.98% in emergent or urgent vs. 3.98% in elective cases). Given the accumulating clinical experience and the consequent, continual evolution of surgical indications, the Sun's procedure is becoming increasingly applied/used worldwide as an innovative and imaginative enhancement of surgical options for the dissected (or aneurysmal) ascending aorta, aortic arch and proximal descending aorta, and may become the next standard treatment for type A aortic dissections requiring repair of the aortic arch.

Elevated Triglycerides Levels in Two Infants With Hypoxic‐ischemic Encephalopathy Undergoing Therapeutic Hypothermia and Receiving Parenteral Nutrition

Therapeutic hypothermia has been widely applied to improve the survival/neurodevelopmental outcomes among infants with moderate-to-severe hypoxic ischemic encephalopathy (HIE). Due to their critical condition and concerns over feeding tolerance, it is not uncommon to withhold enteral feeds and provide parenteral nutrition (PN) during hypothermia and early rewarming. Here we report 2 infants with HIE undergoing therapeutic hypothermia, and receiving PN, who exhibited early elevated triglyceride levels. Hypertriglyceridemia can be associated with neurologic complications, ranging from altered mental status, or irritability to seizures. Given the possible altered lipid metabolism under hypothermic conditions, we advocate close monitoring of lipid tolerance and conducting further prospective trials to elucidate lipid metabolism in these infants.

Abstract 53: Abnormal Continuous Electroencephalography Recordings Are Not Predictive of Survival Outcomes Following Cardiac Arrest

Background: Cerebral anoxia following cardiac arrest can lead to poor neurological outcomes. Post-arrest therapeutic hypothermia (TH) has been shown to be neuroprotective in this setting. Early prognostication of survival outcomes is important for patient care and resource management. The use of continuous electroencephalography (cEEG) may be an important tool for prognostication of survival outcomes after cardiac arrest. Objectives: To determine if abnormal cEEG recordings are associated with survival outcomes following cardiac arrest. Methods: Retrospective study of all patients who suffered an in- or out-of-hospital cardiac arrest and were entered into the post-arrest management protocol (PAMP) at a single academic institution between May 2011 and May 2012. As part of the PAMP, cEEGs are recorded during TH, during the rewarming phase, and at normothermia. All cEEG reports were assessed for routinely described abnormal patterns: severe suppression, burst suppression, status epilepticus, intermittent epileptiform discharges (IED), generalized periodic epileptiform discharges (GPED), either α,β, or [[Unable to Display Character: ▵]] coma, or diffuse intermixed slowing. Descriptive statistics were analyzed. Results: Ninety-one patients were admitted to the ICU after cardiac arrest and 42 patients had PAMP and TH initiated. Of these, 36 (86%) received a neurologic consultation and 27(64%) had a cEEG placed. 24/27 (89%) survived to 24 hours and 7/27 (26%) survived to hospital discharge. Of the 7 survivors to discharge, 1 had severe suppression, 3 demonstrated α,β, or [[Unable to Display Character: ▵]] coma, and 3 demonstrated diffuse intermixed slowing during MTH. During early rewarming and normothermia, 3 had diffuse intermixed slowing, 2 demonstrated either α,β, or [[Unable to Display Character: ▵]] coma, and 1 demonstrated IEDs. Conclusion: Abnormal cEEG during MTH and early rewarming is not predictive of survival outcomes following cardiac arrest in this small, retrospective study. This study is limited by the small number of enrolled patients who have completed the protocol to date.

Case Report of Valproate-Induced Hypothermia in a Patient With Schizoaffective Disorder

Case Report of Valproate-Induced Hypothermia in a Patient With Schizoaffective Disorder

Jugular Venous Oxygenation During Hypothermic Cardiopulmonary Bypass in Patients at Risk for Abnormal Cerebral Autoregulation: Influence of α-Stat Versus pH-Stat Blood Gas Management

In a prospective, randomized study of cardiac surgical patients at risk for impaired cerebral blood flow autoregulation, we compared alpha-stat and pH-stat blood gas management. The 40 patients enrolled had age >70 yr, diabetes, prior stroke, or uncontrolled hypertension. During hypothermia and early rewarming, jugular oxygen tensions were significantly lower in alpha-stat patients (n = 12) than pH-stat patients (n = 19; P < 0.05). During rewarming, jugular venous desaturation (i.e., SjvO(2) <50%) occurred in 6 of 12 alpha-stat patients, but no pH-stat patients (P = 0.0006). Patients at risk for poor cerebral autoregulation have higher oxygen tensions and saturations if pH-stat blood gas management is used during cardiopulmonary bypass.

Little evidence for a major role of Ca 2+ in cold-induced injury of liver cells

We have previously shown that cold-induced injury to hepatocytes and liver endothelial cells occurs predominantly via an iron-dependent pathway. However, other groups have reported evidences suggesting that Ca 2+ ions could be involved in the process of cold-induced injury of liver cells. We here assessed the relative importance and potential interaction of both pathways in cultured primary hepatocytes and cultured liver endothelial cells. The sequence cold incubation/rewarming of hepatocytes and endothelial cells led to an increase in the cytosolic calcium concentration during the early rewarming phase, but the increased cytosolic calcium concentration did not correlate with cell injury. A partial protection from cold-induced cell injury was achieved by the intracellular calcium chelators Quin-2 and BAPTA. However, additional experiments showed that the ability of these chelators to bind iron was probably responsible for a major part of this protection. Incubation in calcium-free media led to an increased cell injury and a physiological calcium concentration (2.5 mM) was protective. In addition, targeting suggested downstream pathways of calcium-dependent cold-induced injury, i.e. by the addition of Ruthenium Red, an inhibitor of mitochondrial Ca 2+ uniporter, or by inhibiting Bax translocation to the mitochondria, did not provide protection from cold-induced injury in both cell types. Taken together, our data suggest that calcium increases but does not play a major role in cold-induced cell injury to hepatocytes and liver endothelial cells.

In Vitro Validation of the Affinity NT Oxygenator Arterial Outlet Temperatures

During cardiopulmonary bypass, the rates of cooling and rewarming and the maximum temperatures attained are implicated in patient morbidity. Thus, accurate oxygenator arterial outlet temperature measurements are needed. The purpose of this study was to determine the accuracy of the arterial outlet temperature probe on the “Affinity NT” membrane oxygenator in measuring perfusate temperatures. An in vitro circuit was used. Crystalloid solution was recirculated through an Affinity NT membrane oxygenator and, to simulate the patient, a second oxygenator. Water was recirculated through the heat exchanger of the second oxygenator via a reservoir. A myocardial temperature probe was inserted in-line 4 cm distal to the Affinity NT oxygenator arterial outlet temperature probe and was considered to measure the actual temperature of the perfusate. Temperatures were simultaneously recorded from the in-line probe, arterial outlet probe, and reservoir every second. Twenty-seven trials were run using random combinations of three Affinity NT oxygenators and three in-line probes. Each trial entailed cooling an initially normothermic reservoir to 28°C and then rewarming it to normothermia again. The arterial outlet temperature probe on the Affinity NT membrane oxygenator underestimated the perfusate temperatures during early rewarming (bias of 0.72°C; precision of ±1.15°C) and late rewarming (bias of 0.52°C; precision of ±0.97°C). An overestimation of the perfusate temperatures occurred during early cooling (bias of −0.57°C; precision of ±1.37°C). Only during the late cooling phase was the arterial outlet temperature probe accurate (bias of −0.02°C; precision of ±0.3°C). The perfusionist should be aware of the temperature probe monitoring characteristics of the oxygenator to safely perfuse the patient.

Effects of pH Management During Deep Hypothermic Bypass on Cerebral Microcirculation: Alpha-Stat Versus pH-Stat

There is controversy regarding the optimal pH strategy during deep hypothermic bypass in children. We directly visualized the effects of the pH-stat and alpha-stat strategy on cerebral microcirculation (including leukocyte/endothelial cell interactions) in a piglet model using intravital fluorescence microscopy. Two groups of 5 piglets (mean weight 9.6+/-1.3 kg) with a cranial window over parietal cerebral cortex underwent 10-minute normothermic bypass, 40-minute cooling on cardiopulmonary bypass ([CPB] Hct 30%, 100 mL/kg/min), 60-minute circulatory arrest at 15 degrees C, and 40-minute rewarming with alpha-stat (group alpha) or pH-stat (group pH). Plasma was labeled with fluorescein-ITC-dextran for assessment of microvascular diameter. Circulating leukocytes were labeled and observed in postcapillary venules for adhesion before and up to 120 minutes after CPB. Cerebral tissue oxygenation was evaluated by quantification of NADH autofluorescence, which increases during ischemia. At the end of normothermic bypass diameter of cerebrocortical microvessels increased to 116+/-9% (alpha) versus 119+/-10% (pH) of pre-CPB baseline values. During cooling microvascular diameter decreased in group alpha and significantly increased in group pH (89+/-11% (alpha) versus 132+/-13% (pH) at the end of cooling; P<0.001). During the first 10 minutes of rewarming, the cerebral microvascular diameter was significantly larger when the pH stat strategy was used. Tissue oxygenation at the end of cooling was significantly greater in the pH-stat group (P=0.008). On reperfusion, the pH-stat strategy resulted in significantly more rapid return of tissue oxygenation toward baseline although at the end of rewarming the metabolic recovery was complete in both groups. The whole body lactate during early rewarming was significantly less with the pH stat strategy. There was no significant difference between the groups regarding the number of adherent leukocytes throughout the time course of the experiment. pH-stat management increases tissue oxygenation during deep hypothermic bypass and after circulatory arrest. Leukocyte/endothelial cell interactions during hypothermic bypass are mild with both alpha-stat and pH-stat.

Effect of Cold Treatment on Enzymic and Nonenzymic Antioxidant Activities in Leaves of Chilling-Tolerant and Chilling-Sensitive Cucumber(Cucumis sativus L.) Cultivars.

Low activity of oxygen radical generation in leaves during and after chilling is implicated in the high chilling tolerance of cucumber (Cucumis sativus L.) cultivars (Shen et al., 1999). In this study, the activity or content of enzymic and nonenzymic antioxidants in leaves were compared between chilling-tolerant 'Jinchun No.3' and chilling-sensitive 'Suyo', during a 24-hr chilling period at 3°C in the dark and subsequent 24 hr at 28/22°C (day/night) under a 12 hr-photoperiod (rewarming). During chilling, activities of catalase (CAT) decreased, while those of superoxide dismutase (SOD), guaiacol peroxidase (POX) and ascorbate peroxidase (APX) were equal to those in control leaves exposed to 15°C in the dark for 24 hr in both cultivars. Ascorbic acid (AsA), dehydroascorbic acid (DHA), and reduced glutathione (GSH) increased during chilling in 'Jinchun No.3' but not in 'Suyo'. During rewarming, however, most antioxidant enzymes increased in their activities in chilled leaves. SOD activity increased more greatly in 'Jinchun No.3' than it did in 'Suyo'. APX activity also increased greatly in 'Jinchun No.3' but it did not increase in 'Suyo'. The increases in CAT and POX activities were similar in the two cultivars. AsA, GSH, and oxidized glutathione (GSSG) also increased during rewarming in 'Jinchun No.3' leaves, whereas in 'Suyo' leaves, DHA increased during early rewarming, but GSH and GSSG did so only toward the end of the rewarming period. The results are discussed in relation to the difference in chilling tolerance between the two cucumber cultivars.

External rewarming and age in mildly hypothermic patients after cardiac surgery

To compare the effects of two external rewarming methods on body core temperature and the rate of rewarming between two age groups (less than 65 years, 65 years or more) of adult, mildly hypothermic patients who have undergone cardiac surgery, during the immediate postoperative period. Stratified, randomized clinical trial. Five-bed cardiac surgical intensive care unit in a large teaching-research institution. Thirty-two white patients who had undergone cardiac surgery and who had mildly hypothermic body core temperatures (33 degrees to 35 degrees C) immediately after the surgery. Body core temperature was measured with a pulmonary artery catheter thermistor at the time of external rewarming method application and at 60, 90, and 150 minutes afterward. Rate of rewarming was measured as body core temperature change in degrees Celsius per hour (at 36.6 degrees C, minus body core temperature when external rewarming method was applied, divided by total rewarming time). Temperatures were recorded six times at intervals of 15 minutes; then every 30 minutes until a value of 36.6 degrees C was obtained, at which time the blanket was removed; then hourly for 8 hours. Either a fluid-filled circulating blanket (active-conductive external rewarming) or a reflective blanket (passive-reflective external rewarming) was applied immediately after core temperature was measured on admission to the cardiac surgical intensive care unit after surgery. External rewarming methods affected body core temperature differently at different times, and there were significant differences in body core temperature across the time periods (p < 0.05). Both active and passive external rewarming methods showed a sigmoidal rewarming pattern without a downward temperature drift. The fluid-filled circulating blanket produced a quicker and steeper body core temperature change in the early rewarming phase; the reflective blanket resulted in a more gradual temperature rise. Age did not significantly affect body core temperature, nor did age or external rewarming method significantly influence the rate of rewarming, although total rewarming time was longer for those of more advanced age. Seven subjects with passive rewarming method experienced body core temperature overshoot during the 8-hour period after blanket removal. In this study, conduction and reflection of radiant heat were equally effective in producing an acceptable rate of rewarming but contributed to different internal patterns in core rewarming. The average total rewarming time with the active external rewarming method was 1 hour shorter than with the passive external rewarming method.

The Radial Forearm Flap Donor Site

Controversy exists in the literature regarding reconstruction of the radial artery after elevation of the radial forearm flap. The literature suggests that reconstructing the radial artery with a vein graft is an important aspect in the use of this flap. In our experience, this has never been performed with no sequela. We examined 13 consecutive patients who underwent radial forearm flaps for head and neck reconstruction over a 28-month period. The patients were examined and questioned about the function of their upper extremities in hope of evaluating the postoperative vascular status in each. Median follow-up was 6 months, with a range of 1 month to 24 months. No patient had preexisting trauma or congenital abnormality of either arm, so that the nondonor arm could be considered as a control for each patient. Evaluation consisted of history and physical examination. The following parameters in each patient were carefully accumulated: grip strength, cutaneous blood flow measured by using a laser Doppler flowmeter, transcutaneous oxygen levels, digital/brachial blood pressure ratios, cutaneous temperature from thumb/index and thumb/small pinch, and rapid rewarming at 1-minute and 5-minute intervals after cold immersion for 2 minutes. The radial forearm flap was elevated in each patient in the nondominant extremity. Grip strengths ranged from 19 to 77 kg, with a median of 30 kg. Early rewarming of the thumb/index was also an average of 1.5 degrees less than the temperature in the control arm and was statistically significant to (p = .01).(ABSTRACT TRUNCATED AT 250 WORDS)

Characterization of a sodium pump-induced hyperpolarization in isolated human atrium

Specimens of right atrial appendage from 106 patients were incubated in cold Tyrode solution, and transmembrane resting potentials (Em) were recorded during rewarming at selected temperatures. Rewarming caused a transient hyperpolarization to develop. The hyperpolarization had a temperature threshold between 17 and 22 degrees C and was inhibited by acetylstrophanthidin. Acetylcholine (ACh) induced a depolarization during early rewarming in 7, 10, 20, and 40 mM K+, indicating that Em hyperpolarized to a potential negative to the equilibrium potential for K+. ACh had no effect after some decline of Em, and hyperpolarization was induced by ACh when Em had reached steady state. The relationship between [K+] in the bulk phase of the superfusate [( K]b) and the "reversal potentials" for the ACh effect was log linear and had a slope of 61.7 mV per tenfold change in [K]b. The relationship between [K]b and hyperpolarization was studied in the presence of 0.5 mM Ba2+. The apparent [K]b resulting in half-maximal pump-induced hyperpolarization was 1.3 mM. The data indicate that human atrium can pump Na+ electrogenically and that the characteristics of the Na+ pump-induced hyperpolarization resemble those described for cardiac tissue from several other mammalian species.