Induction of therapeutic hypothermia after cardiac arrest in prehospital patients using ice-cold Ringer’s solution: a pilot study

Therapeutic hypothermia

Therapeutic hypothermia has been used for millennia, but in recent years was not in much clinical use due to an apparent high risk of complications. More recently, the benefits of induced therapeutic hypothermia have been rediscovered, mainly with the improvement in neurological outcome in out-of-hospital cardiac arrest victims. In addition, therapeutic hypothermia has been suggested to improve outcome in other neurological conditions such as traumatic brain injury, neonatal asphyxia, cerebrovascular accidents and intracranial hypertension. This article reviews the history of the discovery of therapeutic hypothermia, as well as the current therapeutic applications and ways to deliver this treatment. Cooling techniques and recovery processes, as well as potential complications are also reviewed. Clinicians caring for a wide variety of critically ill patients should be familiar with the use of therapeutic hypothermia.

Indications and limitations of induced hypothermic therapy for out-of-hospital cardiopulmonary arrest

PURPOSE

To identify candidates indicated to undergo induced hypothermic therapy (IHT) among comatose survivors of out-of-hospital cardiopulmonary arrest (CPA) based on a retrospective review of medical charts.

METHODS

Between 1995 and 2004, 49 patients who recovered from CPA and treated by IHT were analyzed. The subjects were divided into 2 groups. The first group (GR, n = 16) consisted of patients with a recovery of consciousness and the second group (VD, n = 33) consisted of patients who either remained unconscious or who died.

RESULTS

Using a multiple logistic regression analysis, out-of-hospital return of spontaneous circulation was the only factor independently associated with the outcome (odds ratio, 0.03; 95% confidence interval, 0.00-0.23; P = .001).

CONCLUSION

IHT may be beneficial for CPA patients with out-of-hospital return of spontaneous circulation. Because of the small sample size, further large human studies are warranted.

Induction of hypothermia in patients with various types of neurologic injury with use of large volumes of ice-cold intravenous fluid

OBJECTIVE

Mounting evidence suggests that mild to moderate hypothermia can mitigate neurologic and myocardial injury. The speed of induction appears to be a key factor in determining its efficacy. However, even when the fastest currently available cooling techniques are used, reaching target temperatures takes at least 2 hrs and usually longer. We hypothesized that infusion of refrigerated fluids could be a safe accessory method to increase cooling speed.

DESIGN

Prospective intervention study.

SETTING

University teaching hospital.

PATIENTS

One hundred thirty-four patients with various types of neurologic injury (postanoxic encephalopathy, subarachnoid hemorrhage, or traumatic brain injury).

MEASUREMENTS AND MAIN RESULTS

Hypothermia was induced in 134 patients with various types of neurologic injury, by means ice-water cooling blankets and infusion of refrigerated (4 degrees C) saline (110 patients) or saline and colloids (24 patients). An average volume of 2340 +/- 890 mL of refrigerated fluids was infused in 50 mins. Core temperatures decreased from 36.9 +/- 1.9 degrees C to 34.6 +/- 1.5 degrees C at t = 30 mins and to 32.9 +/- 0.9 degrees C at t = 60 mins (target temperature: 32 degrees C-33 degrees C). Monitoring of blood pressure, heart rhythm, central venous pressure, blood gasses, electrolyte and glucose levels, and platelet and white blood cell count revealed no additional adverse effects. Mean arterial pressure increased by 15 mm Hg, with larger increases in blood pressure occurring in hemodynamically unstable patients. No patient developed pulmonary edema.

CONCLUSIONS

Induction of hypothermia by means of cold-fluid infusion combined with ice-water cooling blankets is safe, efficacious, and quick. Because the speed of cooling is important to increase its protective effects, we recommend that cold-fluid infusion be used in all patients treated with induced hypothermia. This should be combined with another method to safely and accurately maintain hypothermia once target temperatures have been reached.

The National EMS Research strategic plan

One of the eight major recommendations put forth by the National EMS Research Agenda Implementation Project in 2002 was the development of an emergency medical services (EMS) research strategic plan. Using a modified Delphi technique along with a consensus conference approach, a strategic plan for EMS research was created. The plan includes recommendations for concentrating efforts by EMS researchers, policy makers, and funding resources with the ultimate goal of improving clinical outcomes. Clinical issues targeted for additional research efforts include evaluation and treatment of patients with asthma, acute cardiac ischemia, circulatory shock, major injury, pain, acute stroke, and traumatic brain injury. The plan calls for developing, evaluating, and validating improved measurement tools and techniques. Additional research to improve the education of EMS personnel as well as system design and operation is also suggested. Implementation of the EMS research strategic plan will improve both the delivery of services and the care of individuals who access the emergency medical system.

Akzidentelle urbane Unterkühlung

In emergency medicine accidental hypothermia (<35 degrees C) is a common epiphenomenon of many medical conditions. In contrast, severe hypothermia (<28 degrees C) occurs very seldom and presents a difficult medical situation. Here we present a female patient with severe urban hypothermia (core temperature of 20.7 degrees C) and circulatory arrest. An overview of the emergency treatment, rewarming strategy with extracorporeal circulation and the clinical course will be given. The survival of the patient and the favorable neurological outcome will be discussed considering the current literature. Due to the paucity of treatment guidelines or clear prognostic criteria of withholding or withdrawing treatment in severe hypothermia, the decision of prolonged resuscitation and rewarming strategy is solely dependent on the individual judgement and medical experience of the physician. The positive clinical outcome which can be gleaned from case reports or single retrospective studies should encourage the emergency physician to selectively rewarm a severe hypothermic patient with extracorporeal circulation under prolonged CPR.

Induction of mild hypothermia with infusion of cold (4°C) fluid during ongoing experimental CPR

INTRODUCTION

Therapeutic hypothermia after resuscitation has been shown to improve the outcome regarding neurological state and to reduce mortality. The earlier hypothermia therapy is induced probably the better. We studied the induction of hypothermia with a large volume of intravenous ice-cold fluid after cardiac arrest during ongoing cardiopulmonary resuscitation (CPR).

METHODS

Twenty anaesthetised piglets were subjected to 8 min of ventricular fibrillation, followed by CPR. They were randomized into two groups. The hypothermic group was given an infusion of 4 degrees C acetated Ringer's solution 30 ml/kg at an infusion rate of 1.33 ml/kg/min, starting after 1 min of CPR. The control group received the same infusion at room temperature. All pigs received a bolus dose of vasopressin after 3 min of CPR. After 9 min, defibrillatory shocks were applied to achieve restoration of spontaneous circulation (ROSC). Core temperature and haemodynamic variables were measured at baseline and repeatedly until 180 min after ROSC. Cortical cerebral blood flow was measured, using Laser-Doppler flowmetry.

RESULTS

All pigs had ROSC, except one animal in the hypothermic group. Only one animal in the hypothermic group died during the observation period. The calculated mean temperature reduction was 1.6+/-0.35 degrees C (S.D.) in the hypothermic group and 1.1+/-0.37 degrees C in the control group (p=0.009). There was no difference in cortical cerebral blood flow and haemodynamic variables.

CONCLUSION

Inducing hypothermia with a cold infusion seems to be an effective method that can be started even during ongoing CPR. This method might warrant consideration for induction of early therapeutic hypothermia in cardiac arrest victims.

[Therapeutic hypothermia after cardiac arrest]

The use of therapeutic hypothermia following different hypoxic-ischaemic insults has played an important role in various concepts of non-specific protection of cells for a long time. Although the use of deep therapeutic hypothermia after cardiac arrest in the last century did not lead to an improved outcome, recent data have demonstrated very positive effects of mild therapeutic hypothermia. The data from the European multicenter trial as well as those from Australia have clearly demonstrated a decrease in mortality and a better neurological outcome for patients being cooled to 32-34 degrees C for 12 or 24 h. In 2003, this led to the implementation of mild therapeutic hypothermia (32-34 degrees C) into the International Liaison Committee on Resuscitation (ILCOR) recommendations and guidelines for the treatment of unconscious patients after prehospital cardiac arrest. This article gives an overview on existing concepts and future perspectives of therapeutic mild hypothermia.