Rewarming of healthy volunteers after induced mild hypothermia: a healthy volunteer study

Effect of "An Innovative Technology" Active Warming and Passive Warming on Unplanned Hypothermia During Perioperative Period: A Clinical Trial

Patients are at risk for unplanned hypothermia during the perioperative period due to many reasons, including anesthesia, low room temperature, cold intravenous fluid, and blood transfusion. This study was conducted to examine the effect of active and passive warming methods applied in patients during the perioperative period on unplanned hypothermia. This study is a case-control type study. The population of this study is composed of the patients hospitalized in surgical clinic and undergone abdominal region-related operations. Ninety patients were accidentally included in the study. The first group of patients were actively warmed during the perioperative period (carbon fiber resistive system - W-500D + 190 × 50 cm), the second group was passively warmed at least for 20 minutes during preoperative period (with blanket, socks etc.), and the third group was followed up as the control group. It was established that body temperature average of the active warming group has significantly increased during perioperative period (p < 0.001), and this temperature was significantly higher than the other groups until the third hour. It was found that the body temperature average of all groups was equal to 36.2 ± 0.26, 35.4 ± 0.49, and 35.2 ± 0.47, respectively, at the end of operation, and the difference among them was statistically significant (p ≤ 0.001). The active warming method applied with carbon fiber resistive system during the perioperative period is an effective method.

Accidental hypothermia-an update : The content of this review is endorsed by the International Commission for Mountain Emergency Medicine (ICAR MEDCOM)

BACKGROUND

This paper provides an up-to-date review of the management and outcome of accidental hypothermia patients with and without cardiac arrest.

METHODS

The authors reviewed the relevant literature in their specialist field. Summaries were merged, discussed and approved to produce this narrative review.

RESULTS

The hospital use of minimally-invasive rewarming for non-arrested, otherwise healthy, patients with primary hypothermia and stable vital signs has the potential to substantially decrease morbidity and mortality for these patients. Extracorporeal life support (ECLS) has revolutionised the management of hypothermic cardiac arrest, with survival rates approaching 100 % in some cases. Hypothermic patients with risk factors for imminent cardiac arrest (temperature <28 °C, ventricular arrhythmia, systolic blood pressure <90 mmHg), and those who have already arrested, should be transferred directly to an ECLS-centre. Cardiac arrest patients should receive continuous cardiopulmonary resuscitation (CPR) during transfer. If prolonged transport is required or terrain is difficult, mechanical CPR can be helpful. Delayed or intermittent CPR may be appropriate in hypothermic arrest when continuous CPR is impossible. Modern post-resuscitation care should be implemented following hypothermic arrest. Structured protocols should be in place to optimise pre-hospital triage, transport and treatment as well as in-hospital management, including detailed criteria and protocols for the use of ECLS and post-resuscitation care.

CONCLUSIONS

Based on new evidence, additional clinical experience and clearer management guidelines and documentation, the treatment of accidental hypothermia has been refined. ECLS has substantially improved survival and is the treatment of choice in the patient with unstable circulation or cardiac arrest.

Effect evaluation of a heated ambulance mattress-prototype on body temperatures and thermal comfort--an experimental study

Background

Exposure to cold temperatures is, often, a neglected problem in prehospital care. One of the leading influences of the overall sensation of cold discomfort is the cooling of the back. The aim of this study was to evaluate the effect of a heated ambulance mattress-prototype on body temperatures and thermal comfort in an experimental study.

Method

Data were collected during four days in November, 2011 inside and outside of a cold chamber. All participants (n = 23) participated in two trials each. In one trial, they were lying on a stretcher with a supplied heated mattress and in the other trial without a heated mattress. Outcomes were back temperature, finger temperature, core body temperature, Cold Discomfort Scale (CDS), four statements from the state-trait anxiety – inventory (STAI), and short notes of their experiences of the two mattresses. Data were analysed both quantitatively and qualitatively. A repeated measure design was used to evaluate the effect of the two mattresses.

Results

A statistical difference between the regular mattress and the heated mattress was found in the back temperature. In the heated mattress trial, the statement “I am tense” was fewer whereas the statements “I feel comfortable”, “I am relaxed” and “I feel content” were higher in the heated mattress trial. The qualitative analyses of the short notes showed that the heated mattress, when compared to the unheated mattress, was experienced as warm, comfortable, providing security and was easier to relax on.

Conclusions

Heat supply from underneath the body results in increased comfort and may prevent hypothermia which is important for injured and sick patients in ambulance care.

Peri-operative warming devices: performance and clinical application

Since the adverse consequences of accidental peri-operative hypothermia have been recognised, there has been a rapid expansion in the development of new warming equipment designed to prevent it. This is a review of peri-operative warming devices and a critique of the evidence assessing their performance. Forced-air warming is a common and extensively tested warming modality that outperforms passive insulation and water mattresses, and is at least as effective as resistive heating. More recently developed devices include circulating water garments, which have shown promising results due to their ability to cover large surface areas, and negative pressure devices aimed at improving subcutaneous perfusion for warming. We also discuss the challenge of fluid warming, looking particularly at how devices' performance varies according to flow rate. Our ultimate aim is to provide a guide through the bewildering array of devices on the market so that clinicians can make informed and accurate choices for their particular hospital environment.

Equipment to prevent, diagnose, and treat hypothermia: a survey of Norwegian pre-hospital services

Introduction

Hypothermia is associated with increased morbidity and mortality in trauma patients and poses a challenge in pre-hospital treatment. The aim of this study was to identify equipment to prevent, diagnose, and treat hypothermia in Norwegian pre-hospital services.

Method

In the period of April-August 2011, we conducted a survey of 42 respondents representing a total of 543 pre-hospital units, which included all the national ground ambulance services, the fixed wing and helicopter air ambulance service, and the national search and rescue service. The survey explored available insulation materials, active warming devices, and the presence of protocols describing wrapping methods, temperature monitoring, and the use of warm i.v. fluids.

Results

Throughout the services, hospital duvets, cotton blankets and plastic “bubble-wrap” were the most common insulation materials. Active warming devices were to a small degree available in vehicle ambulances (14%) and the fixed wing ambulance service (44%) but were more common in the helicopter services (58-70%). Suitable thermometers for diagnosing hypothermia were lacking in the vehicle ambulance services (12%). Protocols describing how to insulate patients were present for 73% of vehicle ambulances and 70% of Search and Rescue helicopters. The minority of Helicopter Emergency Medical Services (42%) and Fixed Wing (22%) units was reported to have such protocols.

Conclusion

The most common equipment types to treat and prevent hypothermia in Norwegian pre-hospital services are duvets, plastic “bubble wrap”, and cotton blankets. Active external heating devices and suitable thermometers are not available in most vehicle ambulance units.

The effectiveness and cost of passive warming in adult ambulatory surgery patients

Hypothermia is a common problem for surgical patients and can result in many complications. Because few studies compare methods of passive warming, we used an unblinded, prospective, experimental, randomized design to compare the effectiveness of two passive methods of normothermia management in the postanesthesia care unit (PACU). We assigned a total of 578 adult ambulatory surgery patients to either a control group that was given two folded, warmed cotton blankets or a treatment group that was given a warmed, unfolded cotton sheet and cotton blanket. We recorded patients' temperatures on their arrival in the PACU and at 30 minutes after arrival. The treatment group had temperatures that were significantly higher than those of the control group 30 minutes after arrival in the PACU, and the treatment group experienced a greater change in temperature from baseline measurements to those taken at 30 minutes. The treatment group also used fewer warmed blankets, resulting in cost savings for the PACU.