[Prewarming according to the AWMF S3 guidelines on preventing inadvertant perioperative hypothermia 2014 : Retrospective analysis of 7786 patients]. / Vorwärmung entsprechend der "S3 Leitlinie Vermeidung von unbeabsichtigter perioperativer Hypothermie 2014" : Retrospektive Analyse von 7786 Patienten.

BACKGROUND: Inadvertent perioperative hypothermia, which is defined as a core body temperature of less than 36.0 °C, can have serious consequences in surgery patients. These include cardiac complications, increased blood loss, wound infections and postoperative shivering; therefore, the scientific evidence that inadvertent perioperative hypothermia should be avoided is undisputed and several national guidelines have been published summarizing the scientific evidence and recommending specific procedures. The German AWMF guidelines were the first to emphasize the importance of prewarming for surgery patients to avoid inadvertant perioperative hypothermia; however, in contrast to intraoperative warming, prewarming is so far not sufficiently implemented in clinical practice in many hospitals. Furthermore, a recent study has questioned the effectiveness of prewarming. OBJECTIVE: The aim of this retrospective investigation was to evaluate the hypothermia rates that can be achieved when prewarming in the anesthesia induction room is introduced into the clinical practice and performed in addition to intraoperative warming. MATERIAL AND METHODS: The ethics committee of the Medical Faculty of the Martin Luther University Halle Wittenberg gave approval for data storage and retrospective data analysis from the anesthesia database. According to the existing local standard operating procedure, prewarming with forced air was performed in addition to intraoperative warming in the anesthesia induction room in 3899 patients receiving general anesthesia with a duration of 30 min or longer from January 2015 to December 2016. The results were compared with a control group of 3887 patients from July 2012 to August 2014 who received intraoperative warming but were not subjected to prewarming. Tracheal intubation was carried out in all patients and temperature measurements after the induction of anesthesia were performed using esophageal, urinary catheter or intra-arterial temperature probes. RESULTS: The mean duration of prewarming was 25 min in the treatment group. Patients subjected to prewarming showed an intraoperative hypothermia rate of 15.8% and a postoperative hypothermia rate of 5.1%. Patients without prewarming showed an intraoperative hypothermia rate of 30.4% and a postoperative hypothermia rate of 12.4%. This means a 52% reduction of the intraoperative hypothermia rate and a 41% reduction of the postoperative hypothermia rate for patients who received prewarmimg (p < 0.0001). Multivariate logistic regression revealed that the lack of prewarming was independently associated with intraoperative hypothermia with an odds ratio of 2.5 (95% confidence interval CI 2.250-2.841; p < 0.0001) and postoperative hypothermia with an odds ratio of 2.8 (95% CI 2.316-3.277; p < 0.0001). CONCLUSION: Prewarming, as recommended in the AWMF guidelines, resulted in a significant and clinically relevant reduction in the incidence of inadvertent perioperative hypothermia; therefore, prewarming can still be regarded as an effective method to avoid perioperative hypothermia. Hypothermia rates of 15.8% intraoperatively and 5.1% postoperatively can be achieved in clinical practice, when prewarming is performed in addition to intraoperative warming in the anesthesia induction room directly before the start of surgical procedures.

Temperature Variation After Rewarming from Deep Hypothermic Circulatory Arrest Is Associated with Survival and Neurologic Outcome.

Therapeutic hypothermia is recommended by international guidelines after cardio-circulatory arrest. However, the effects of different temperatures during the first 24 hours after deep hypothermic circulatory arrest (DHCA) for aortic arch surgery on survival and neurologic outcome are undefined. We hypothesize that temperature variation after aortic arch surgery is associated with survival and neurologic outcome. In the period 2010-2014, a total of 210 consecutive patients undergoing aortic arch surgery with DHCA were included. They were retrospectively divided into three groups by median nasopharyngeal temperature within 24 hours after rewarming: hypothermia (<36°C; n = 65), normothermia (36-37°C; n = 110), and hyperthermia (>37°C; n = 35). Multivariate stepwise logistic and linear regressions were performed to determine whether different temperature independently predicted 30-day mortality, stroke incidence, and neurologic outcome assessed by cerebral performance category (CPC) at hospital discharge. Compared with normothermia, hyperthermia was independently associated with a higher risk of 30-day mortality (28.6% vs. 10.9%; odds ratio [OR] 2.8; 95% confidence interval [CI], 1.1-8.6; p = 0.005), stroke incidence (64.3% vs. 9.1%; OR 9.1; 95% CI, 2.7-23.0; p = 0.001), and poor neurologic outcome (CPC 3-5) (68.8% vs. 39.6%; OR 4.8; 95% CI, 1.4-8.7; p = 0.01). No significant differences were demonstrated between hypothermia and normothermia. Postoperative hypothermia is not associated with a better outcome after aortic arch surgery with DHCA. However, postoperative hyperthermia (>37°C) is associated with high stroke incidence, poor neurologic outcome, and increased 30-day mortality. Target temperature management in the first 24 hours after surgery should be evaluated in prospective randomized trials.

Extracorporeal Life Support for Refractory Cardiac Arrest from Accidental Hypothermia: A 10-Year Experience in Edinburgh.

BACKGROUND: Cardiac arrest caused by accidental hypothermia is a rare phenomenon with a significant mortality rate if untreated. The consensus is that these patients should be rewarmed with extracorporeal life support (ECLS) with the potential for excellent survival and neurologic outcomes. However, given the lack of robust data and clinical trials, the optimal management of such patients remains elusive. OBJECTIVE: In this single-center study, we looked at the outcomes of all adult patients undergoing salvage ECLS for cardiac arrest caused by accidental hypothermia over a 10-year period from June 2006 to June 2016. METHODS: These data were obtained from the Royal Infirmary of Edinburgh cardiothoracic surgery database. The patients' hard copy case notes, TrakCare (InterSystems Corp, Cambridge, MA), picture archiving and communications system (PACS), and WardWatcher databases were used to cross-check the accuracy of the acquired data. RESULTS: Eleven patients met the inclusion criteria. The etiology of hypothermia was exposure to cold air (64%) and cold water immersion (36%). Two (18%) were treated with extracorporeal membrane oxygenation and the rest with cardiopulmonary bypass. The mean age was 51 years (range 32-73), and the mean core body temperature on admission was 20.6°C (range <18-24°C). The overall survival rate to hospital discharge was 72%, with 75% of survivors having no chronic neurologic impairment. CONCLUSION: Our case series shows the remarkable salvageability of patients suffering prolonged cardiac arrest caused by accidental hypothermia, particularly in the absence of asphyxia, trauma, or severe hyperkalemia. ECLS is a safe and effective rewarming treatment and should be used to aggressively manage this patient group.

Rewarming rates in urban patients with hypothermia: prediction of underlying infection.

BACKGROUND: In the urban setting, hypothermia is commonly associated with illness or intoxication, with death often secondary to infection. OBJECTIVES: To evaluate factors that affect the rewarming rate (RWR) and the ability of the RWR and other clinical markers to predict the presence or absence of underlying infection in an adult urban population. METHODS: This was a prospective observational study of hypothermic patient visits to a large emergency department. Serial temperatures were obtained during rewarming to construct rewarming curves. Rewarming modalities selected by emergency physicians were correlated with admission temperatures. Univariate associates of RWR and infection were assessed. RESULTS: The authors identified 96 patient visits. The median temperature was 89.5 degrees F (31.9 degrees C; range, 73.0 degrees F to 95.0 degrees F [22.8 degrees C to 35.0 degrees C]). Thirteen patients had temperatures of < 80.0 degrees F (26.0 degrees C). Seven died within 14 hours of presentation; six, of infection. No patient experienced ventricular fibrillation. Potential candidate predictors of infection from a multivariate analysis were a RWR of < 1.80 degrees F (1.0 degrees C) per hour and a serum albumin of < 2.7 g/dL. Rapid rewarming was associated with the absence of infection and a temperature below 86.0 degrees F (30.0 degrees C). In patients without significant underlying illness, rewarming rates appeared to be independent of the modality of rewarming. CONCLUSIONS: Rewarming rates reflect intrinsic capacity for thermogenesis. Increased RWRs were associated with the absence of infection. The achievement of normothermia did not prevent death in infected patients. Initiation of invasive rewarming in urban patients with hypothermia who have not had hypothermic cardiac arrest may be unwarranted. Management of this population should emphasize support, detection, and treatment of underlying illness.

Heart rate variability and electrocardiogram waveform as predictors of morbidity during hypothermia and rewarming in rats.

This study examined electrocardiogram (ECG) waveform, heart rate (HR), mean blood pressure (BP), and HR variability as potential autonomic signatures of hypothermia and rewarming. Adult male Sprague-Dawley rats had telemetry transmitters surgically implanted, and 2 weeks were allowed for recovery prior to induction of hypothermia. Rats were lightly anesthetized (sodium pentobarbital, 35 mg/kg i.p.) and placed in a coil of copper tubing through which temperature-controlled water was circulated. Animals were cooled to a core temperature (Tc) of 20 degrees C, maintained there for 30 min, and then rewarmed. Data (Tc, BP, HR from ECG, and 10-s strips of ECG waveforms) were collected every 5 min throughout hypothermia and rewarming. Both HR and BP declined after initial increases with the drop in HR starting at a higher Tc than the drop in BP (29.6 +/- 2.4 degrees C vs. 27.1 +/- 3.3 degrees C, p < 0.05). Animals that were not successfully rewarmed exhibited a significant (p < 0.05) increase in the normalized standard deviation of interbeat intervals (IBI) throughout cooling compared with animals that were successfully rewarmed. The T wave of the ECG increased in amplitude and area with decreasing Tc. T-wave amplitude and IBI variability show potential as predictors of survival in hypothermic victims.

Adequate cerebral perfusion pressure during rewarming to prevent ischemic deterioration after therapeutic hypothermia.

Ischemic deterioration during rewarming is one of the most notable clinical complications after successful therapeutic cerebral hypothermia, but the mechanism is not completely understood. Hypothermia may cause vasoconstriction and relative ischemia, especially with insufficient cerebral perfusion pressure (CPP). Various parameters were evaluated to determine the critical CPP threshold to avoid ischemia during rewarming. Cat experimental head injury was induced by inflating an epidural rubber balloon, and intracranial pressure was maintained at 30 mmHg. During rewarming after cerebral hypothermia, CPP was maintained at >120 mmHg (n = 16), 90 mmHg (n = 11), 60 mmHg (n = 11), and 40 mmHg (n=4) by controlling the blood pressure. Cerebral blood flow, cerebral metabolic rate for oxygen, arteriovenous difference of oxygen (AVDO2), cerebral venous oxygen saturation (ScvO2), and extracellular glutamate concentrations were monitored by glutamate oxidase electrode. After rewarming, the cerebral metabolic parameters were almost restored to the pre-injury level in animals with CPP of more than 90mmHg. However, in the animals with CPP= 60 mmHg, all parameters significantly deteriorated and indicated misery perfusion; ScvO2 was low (29.5+/-1.1%), AVDO2 was significantly high (9.9+/-0.8 ml 100 g(-1) min(-1)) (one-way analysis of variance, p<0.05), and electron microscopic features showed subcellular ischemic change. Extracellular glutamate significantly increased during the rewarming period only in the CPP= 40 mmHg group. CPP less than 60 mmHg during rewarming causes secondary ischemic insult, which might indicate continuation of cerebral vasoconstriction in hypothermia. CPP higher than 90 mmHg is required to avoid the potential risk of relative ischemia after hypothermia.

Changing the institutional practice of prolonged mechanical ventilation after coronary artery bypass graft surgery to early extubation.

Since 1997 some of our cardiac anaesthetists have, whenever possible, extubated the patients early after cardiac surgery to improve their level of comfort, to allow an early return of the cardiopulmonary physiological function, and to help reduce health care costs. After a few months of implementing this practice, an audit was carried out to evaluate the success of early extubation after coronary artery bypass graft (CABG) surgery. Over a 6-month period starting from May 1997, the perioperative data of 110 consecutive patients with good or moderate left ventricular function scheduled for elective CABG were prospectively collected and analysed. The anaesthetic regime was according to the preference of the anaesthetists. Initially consent was obtained from the surgeons when the extubation criteria were fulfilled, but subsequently as the practice became more accepted by the surgeons, extubation was initiated by the anaesthetists. Within 4 hours of admission into the intensive care unit (ICU), 50 (45.5%) of the 110 patients satisfied the early extubation criteria and were extubated. The extubation criteria are described in the article. For the remaining patients, the median duration of mechanical ventilation was 14.3 hours. The profiles of the two groups of patients and the possible reasons for not extubating early are discussed. Forty-five per cent of the patients with moderate to good ventricular function were extubated safely within 4 hours of admission into the ICU after CABG surgery. With gradual acceptance of the practice and a change in mindset amongst all the care givers, more patients can benefit from this practice. This article highlights the challenges associated with changing institutional practices with respect to the postoperative care of cardiac patients.

The benefits of active rewarming after cardiac operations: a randomized prospective trial.

We conducted a prospective, randomized trial of three methods of rewarming patients after hypothermic cardiopulmonary bypass. Patients underwent either coronary artery bypass grafting or first-time valve replacement and were cooled to 32 degrees C during bypass. No significant differences existed among the groups as regards operative or preoperative parameters including hemodynamics and blood use. The patients actively warmed with a convective (Bair Hugger system, 3 hours) or a conductive blanket (electric overblanket, 4 hours) reached normothermia more quickly than those warmed with the space blanket (7 hours). This was reflected in significantly earlier extubation in the former two groups: Bair Hugger system 10.8 +/- 0.6 hours, electric blanket 11.3 +/- 1.0 hours, and space blanket 14.8 +/- 0.8 hours. Patients warmed with the space blanket required a higher dosage of morphine over the first 12 hours than those warmed with the electric blanket (10.4 vs 6.5 mg; p = 0.004), which may account for some of the differences between these two groups. No differences could be demonstrated between the two active blankets. On economic grounds we therefore recommend the reusable electric blanket for routine use.

Irrigación pleural continua en hipotermia

La hipotermia es una condición clínica de presentación frecuente en los servicios de urgencias, pero que usualmente no es documentada ni tratada. Se presenta el caso de un paciente de 72 años en quien se documentó hipotermia en el servicio de urgencias.

Hypothermic potassium cardioplegia impairs myocyte recovery of contractility and inotropy.

Acute postoperative left ventricular dysfunction after hypothermic, crystalloid potassium cardioplegia occasionally occurs. This project examined myocyte contractility and inotropic responsiveness after hypothermic arrest with and without potassium cardioplegia. Isolated swine left ventricular myocytes were placed in a thermostatically controlled chamber (37 degrees C) that contained a standard cell medium, pulse stimulated at 1 Hz, and steady-state contractions were measured by computer-assisted video microscopy with and without isoproterenol (25 nmol/L). After baseline measurements were taken the myocytes were randomly assigned to the following treatments: (1) control group with infusion of 37 degrees C crystalloid solution and maintained at 37 degrees C for 3 hours (n = 23), (2) hypothermia group with infusion of 4 degrees C crystalloid without potassium and stored at 4 degrees C for 3 hours (n = 22), (3) hypothermic cardioplegia group with infusion of a crystalloid cardioplegia (oxygenated, buffered 4 degrees C Ringer's solution with 24 mEq/L K+) and then stored at 4 degrees C for 3 hours (n = 35). After treatment the myocytes were then rewarmed to 37 degrees C by infusion of medium, and contractile measurements were repeated. In the control group, the percent and velocity of shortening were identical to those in baseline measurements: 6.4% +/- 0.4% and 53 +/- 5 microns/sec, respectively, and these values remained unchanged in the hypothermia group: 6.5% +/- 0.4% and 51 +/- 3 microns/sec, respectively. However, in the hypothermic cardioplegia group, the percent and velocity of shortening were significantly lower with rewarming: 4.8% +/- 0.4% and 35 +/- 3 microns/sec, respectively, p < 0.05). Isoproterenol caused increased percent and velocity of shortening in both the control and hypothermia groups: 10.0% +/- 0.6% and 9.5% +/- 0.9% and 81.6 +/- 8 microns/sec and 71.4 +/- 8 microns/sec, respectively. This response was significantly blunted in the cardioplegia group (8.9% +/- 0.8% and 56.9 +/- 7 microns/sec, p < 0.05). With an isolated myocyte system that is independent of extracellular and perfusion effects, hyperkalemic cardioplegic solution resulted in depressed myocyte contractile performance after rewarming. Potassium cardioplegia also caused a blunted inotropic responsiveness on rewarming. A potential contributory factor for the depressed left ventricular function after the use of potassium cardioplegia is a direct depression in myocyte contractility.