Heparinless extracorporeal bypass for treatment of hypothermia

A recommended early goal-directed management guideline for the prevention of hypothermia-related transfusion, morbidity, and mortality in severely injured trauma patients

Hypothermia is present in up to two-thirds of patients with severe injury, although it is often disregarded during the initial resuscitation. Studies have revealed that hypothermia is associated with mortality in a large percentage of trauma cases when the patient's temperature is below 32 °C. Risk factors include the severity of injury, wet clothing, low transport unit temperature, use of anesthesia, and prolonged surgery. Fortunately, associated coagulation disorders have been shown to completely resolve with aggressive warming. Selected passive and active warming techniques can be applied in damage control resuscitation. While treatment guidelines exist for acidosis and bleeding, there is no evidence-based approach to managing hypothermia in trauma patients. We synthesized a goal-directed algorithm for warming the severely injured patient that can be directly incorporated into current Advanced Trauma Life Support guidelines. This involves the early use of warming blankets and removal of wet clothing in the prehospital phase followed by aggressive rewarming on arrival at the hospital if the patient's injuries require damage control therapy. Future research in hypothermia management should concentrate on applying this treatment algorithm and should evaluate its influence on patient outcomes. This treatment strategy may help to reduce blood loss and improve morbidity and mortality in this population of patients.

Accidental hypothermia

Accidental hypothermia has produced many cases of intact survival even after prolonged cardiac arrest, but it is also often fatal. In recent years, alterations in resuscitation care that sometimes confused or discouraged resuscitation teams have largely been supplanted by an emphasis on safe, rapid, effective rewarming. Rewarming decisions and even the simple recognition of hypothermia remain challenging. This review seeks to update and demystify some of these challenges.

The Bernese Hypothermia Algorithm: a consensus paper on in-hospital decision-making and treatment of patients in hypothermic cardiac arrest at an alpine level 1 trauma centre

INTRODUCTION

Guidelines for the treatment of patients in severe hypothermia and mainly in hypothermic cardiac arrest recommend the rewarming using the extracorporeal circulation (ECC). However,guidelines for the further in-hospital diagnostic and therapeutic approach of these patients, who often suffer from additional injuries—especially in avalanche casualties, are lacking. Lack of such algorithms may relevantly delay treatment and put patients at further risk. Together with a multidisciplinary team, the Emergency Department at the University Hospital in Bern, a level I trauma centre, created an algorithm for the in-hospital treatment of patients with hypothermic cardiac arrest. This algorithm primarily focuses on the decision-making process for the administration of ECC.

THE BERNESE HYPOTHERMIA ALGORITHM

The major difference between the traditional approach, where all hypothermic patients are primarily admitted to the emergency centre, and our new algorithm is that hypothermic cardiac arrest patients without obvious signs of severe trauma are taken to the operating theatre without delay. Subsequently, the interdisciplinary team decides whether to rewarm the patient using ECC based on a standard clinical trauma assessment, serum potassium levels, core body temperature, sonographic examinations of the abdomen, pleural space, and pericardium, as well as a pelvic X-ray, if needed. During ECC, sonography is repeated and haemodynamic function as well as haemoglobin levels are regularly monitored. Standard radiological investigations according to the local multiple trauma protocol are performed only after ECC. Transfer to the intensive care unit, where mild therapeutic hypothermia is maintained for another 12 h, should not be delayed by additional X-rays for minor injuries.

DISCUSSION

The presented algorithm is intended to facilitate in-hospital decision-making and shorten the door-to-reperfusion time for patients with hypothermic cardiac arrest. It was the result of intensive collaboration between different specialties and highlights the importance of high-quality teamwork for rare cases of severe accidental hypothermia. Information derived from the new International Hypothermia Registry will help to answer open questions and further optimize the algorithm.

[Management of accidental hypothermia]

Patients with hypothermia are frequently encountered in emergency medicine. Particularly trauma patients, but also other predisposed persons, can be expected to suffer from hypothermia at any time of the year. Therapy focuses not only on symptom-oriented intensive care to stabilize and secure vital functions, but also on rewarming. Even in cases of severe hypothermia with circulatory arrest, therapy can produce excellent results. This paper first gives a brief overview of the typical clinical symptoms of hypothermia, before giving a detailed description of the preclinical and in-hospital management of the hypothermia patient. The various rewarming strategies are the subject of special attention and critical evaluation.

Active internal re-warming using a centrifugal pump and heat exchanger following haemorrhagic shock, surgical trauma and hypothermia in a porcine model

BACKGROUND

The centrifugal vortex blood pump (CVBP) using heparin-bonded circuitry allows re-warming of hypothermic trauma patients without anticoagulation. Study objectives were to confirm efficacy, and to characterise the physiology of CVBP re-warming in a porcine model.

METHODS

Sixteen pigs were randomised to conventional or CVBP re-warming. They were bled to a mean arterial pressure of 30 mmHg and cooled to 29 degrees C. A physiological analysis was recorded during resuscitation to normo-tension and re-warming back to 37 degrees C.

RESULTS

CVBP animals re-warmed significantly faster: 85.0+16.4 min versus 217.4+49.3 min (p<0.0001). Activated clotting time was significantly elevated in both groups at 29 degrees C with a marked trend to normalise faster in CVBP pigs. The peak cardiac index (CI) was significantly lower (1.14+0.68 versus 4.83+1.50 L/(min m2), while the systemic vascular resistance (SVR) was significantly higher (4239.9+1173.0 versus 1472.6+451.2 dyn x S x m2/cm5) with CVBP (p<0.001).

CONCLUSION

CVBP is simple and very effective at re-warming hypothermic animals and may also reverse coagulopathy more quickly. Physiological derangements of elevated SVR and diminished CI require further study to elaborate underlying aetiology, and define optimal re-warming strategies.

Thoracic lavage in accidental hypothermia with cardiac arrest — report of a case and review of the literature

BACKGROUND

Accidental hypothermia resulting in cardiac arrest poses numerous therapeutic challenges. Cardiopulmonary bypass (CPB) should be used if feasible since it optimally provides both central rewarming and circulatory support. However, this modality may not be available or is contraindicated in certain cases. Thoracic lavage (TL) provides satisfactory heat transfer and may be performed by a variety of physicians. This paper presents the physiological rationale, technique, and role for TL in accidental hypothermia with cardiac arrest.

METHODS

A patient with hypothermic cardiac arrest, treated by the author using TL, serves as the basis for this report. A search of the English language literature using PubMed (National Library of Medicine, Bethesda, Maryland) was conducted from 1966 to 2003 and 13 additional patients were identified. Demographic information, lavage method, rewarming rate, complications, and neurological outcome were analysed.

RESULTS

There were numerous causes for hypothermia, with drug and alcohol intoxication being the most common (n = 4; 28.6%). Patient age ranged from 8 to 72 years (median = 36 years). Mean core temperature was 24.5+/-0.60 degrees C. Most patients were without blood pressure or pulse upon presentation to the Emergency Department and the predominant cardiac rhythm was ventricular fibrillation (VF) (n = 9; 64.3%). Thoracic lavage was accomplished by thoracotomy in seven patients and tube thoracotomy in the remaining seven. Median rewarming rate was 2.95 degrees C/h. Median time until sinus rhythm was restored was 120 min. Median length of hospital stay was 2 weeks. Four (28.6%) patients died. Complications were seen in 12 (85.7%) patients. Among survivors, neurological outcome was normal in 8 (80%) while two were left with residual impairments.

CONCLUSIONS

Patients presenting in cardiac arrest from accidental hypothermia may be rewarmed effectively using TL. Among survivors, normal neurological recovery is seen. Thoracic lavage should be strongly considered for these patients if CPB is not available or contraindicated.

Use of a Centrifugal Vortex Blood Pump and Heparin-Bonded Circuit for Extracorporeal Rewarming of Severe Hypothermia in Acutely Injured and Coagulopathic Patients

BACKGROUND

Standard rewarming methods for posttraumatic hypothermia are ineffective or require systemic heparinization. Centrifugal vortex blood pumps (CVBPs), heparin-bonded circuits, and, potentially, percutaneous access techniques, facilitate the institution of an extracorporeal circulation by noncardiac surgeons.

METHODS

Seven severely hypothermic patients requiring emergent operative intervention were rewarmed intraoperatively using the CVBP with heparin-bonded circuitry.

RESULTS

Patients were critically ill (average Injury Severity Score of 43.5 [SD, 13.6] for the traumatized patients). The mean temperature before rewarming was 31.5 degrees C (SD, 1.6 degrees C). The CVBP outflow site was the common femoral vein in all patients, with the inflow into the superficial femoral artery (n = 2), contralateral common femoral vein (n = 2), and internal jugular vein (n = 3). The mean time to rewarm to 37 degrees C was 73.3 (SD, 30.5) minutes. All patients survived the initial operation, although the ultimate survival was 43%.

CONCLUSION

Noncardiac surgeons can effectively use an extracorporeal rewarming strategy incorporating a heparin-bonded CVBP to rapidly rewarm hypothermic coagulopathic patients undergoing surgery.

Rapid active internal core cooling for induction of moderate hypothermia in head injury by use of an extracorporeal heat exchanger

OBJECTIVE

Moderate hypothermia (32 degrees C) may limit postischemic neuronal damage and is increasingly used clinically in head injury and stroke. For the use of hypothermia as a neuroprotective agent in the prevention of ischemic damage, it is necessary to induce it as soon as possible after the insult and to keep it at the lowest safe level. Active core cooling using an extracorporeal heat exchanger may circumvent the rather slow induction speed and temperature drifts experienced with surface cooling techniques.

METHODS

In eight patients with severe head injuries (Glasgow Coma Scale score, 4-5), a venovenous extracorporeal circulation was established via a percutaneously introduced double-lumen cannula in the femoral vein. A heat exchanger was connected via a pressure-controlled roller pump. In addition to standard parameters, brain white matter temperature was continuously recorded as the target temperature. Cooling was initiated as early as possible with an extracorporeal temperature of 30 degrees C and maintained at a 32 degrees C brain temperature for 48 hours, and then gradual rewarming for 24 hours.

RESULTS

Cooling was able to be initiated within 6 hours and 48 minutes +/- 3 hours and 47 minutes (mean +/- standard deviation) after trauma. A brain temperature of 32 degrees C was reached within 1 hour and 53 minutes +/- 1 hour and 21 minutes after induction of cooling with a cooling speed of 3.5 degrees C per hour. Brain temperature was able to be controlled within 0.1 degrees C intervals, which was especially helpful in gradual rewarming. No cardiac abnormalities or statistically significant changes in coagulation parameters occurred. Mean platelet count decreased to 89,614+/-42,090 on Day 3 after treatment. No clinical bleeding complications or problems resulting from extracorporeal circulation occurred. Moderate hypothermia was a helpful tool for managing increased intracranial pressure; however, five patients of this series died either of their intracranial abnormalities (n = 4) or of a delayed septic shock after pneumonia (n = 1) at various points in time during therapy. The three survivors experienced either an excellent or a good recovery.

CONCLUSION

The results of this investigation suggest that the use of an extracorporeal heat exchanger to achieve active core cooling is suitable for fast and accurately controllable induction, maintenance, and reversal of moderate hypothermia in emergency situations with reliable control of temperature. In this small series of highly selected patients with severe head injuries, we did not note a beneficial effect of hypothermic therapy on outcome.

Hypothermia

Significant hypothermia is an increasing clinical problem that requires a rapid response with properly trained personnel and techniques. Although the clinical presentation may be such that the victim appears dead, aggressive management may allow successful resuscitation in many instances. Initial management should include CPR if the victim is not breathing or is pulseless. Further core heat loss should be prevented by removing wet garments, insulating the victim, and ventilating with warm humidified air/oxygen to help stabilize core temperature. Core temperature and cardiac rhythm should be monitored in the prehospital setting, if possible, and CPR should be continued during transport. In-hospital management should consist of rapid core rewarming in the severely hypothermic victim with heated humidified oxygen, centrally administered warm IV fluids (43 C), and peritoneal dialysis until extracorporeal rewarming can be accomplished. Postresuscitation complications should be monitored; they include pneumonia, pulmonary edema, cardiac arrhythmias, myoglobinuria, disseminated intravascular thrombosis, and seizures. The decision to terminate resuscitative efforts must be individualized by the physician in charge.

Internal cardiac massage and mediastinal irrigation in hypothermic cardiac arrest

Two unconscious patients with unknown past medical histories were found to be severely hypothermic, with core temperatures of 80.2 degrees F and 86.7 degrees F, respectively. During the course of active internal rewarming, both patients sustained a cardiac arrest. Emergency thoracotomies were immediately done, and internal cardiac massage with warmed mediastinal irrigation was performed. Spontaneous cardiac activity developed in both patients. Within 24 hours after resuscitation, both patients were responsive and following commands.

New horizons in management of hypothermia and frostbite injury

Diagnosing hypothermia requires a high index of suspicion. Restoring lost heat with careful attention to hemodynamics usually results in complete recovery. Frostbite is best treated by physicians who are cognizant of the pathophysiology of cold injury. Although alternative methods of intervention are being tested, rapid rewarming and anti-inflammatory agents are integral to treatment protocols.