Atrioventricular block in accidental hypothermia--a case report

Hypothermia and cardiac electrophysiology: a systematic review of clinical and experimental data

Moderate therapeutic hypothermia procedures are used in post-cardiac arrest care, while in surgical procedures, lower core temperatures are often utilized to provide cerebral protection. Involuntary reduction of core body temperature takes place in accidental hypothermia and ventricular arrhythmias are recognized as a principal cause for a high mortality rate in these patients. We assessed both clinical and experimental literature through a systematic literature search in the PubMed database, to review the effect of hypothermia on cardiac electrophysiology. From included studies, there is common experimental and clinical evidence that progressive cooling will induce changes in cardiac electrophysiology. The QT interval is prolonged and appears more sensitive to decreases in temperature than the QRS interval. Severe hypothermia is associated with more pronounced changes, some of which are proarrhythmic. This is supported clinically where severe accidental hypothermia is commonly associated with ventricular fibrillation or asystole. J-waves in human electrocardiogram recordings are regularly but not always observed in hypothermia. Its relation to ventricular repolarization and arrhythmias is not obvious. Little clinical data exist on efficacy of anti-arrhythmic drugs in hypothermia, while experimental data show the potential of some agents, such as the class III antiarrhythmic bretylium. It is apparent that QT-prolonging drugs should be avoided.

Medical ethics and the interrogation of Guantanamo 063

The controversy over abusive interrogations of prisoners during the war against terrorism spotlights the need for clear ethics norms requiring physicians and other clinicians to prevent the mistreatment of prisoners. Although policies and general descriptions pertaining to clinical oversight of interrogations in United States' war on terror prisons have come to light, there are few public records detailing the clinical oversight of an interrogation. A complaint by the Federal Bureau of Investigation (FBI) led to an Army investigation of an interrogation at the United States prison at Guantanamo Bay. The declassified Army investigation and the corresponding interrogation log show clinical supervision, monitoring and treatment during an interrogation that employed dogs, prolonged sleep deprivation, humiliation, restraint, hypothermia and compulsory intravenous infusions. The interrogation and the involvement of a psychologist, physician and medics violate international and medical norms for the treatment of prisoners.

Effect of hypothermia on baroreflex control of heart rate and renal sympathetic nerve activity in anaesthetized rats

The present study investigated the effect of acute hypothermia on baroreflex control of heart rate (HR) and renal sympathetic nerve activity (RSNA) by generating baroreflex logistic function curves, using bolus doses of phenylephrine and sodium nitroprusside, in anaesthetized male Wistar rats at a core temperature (T(b)) of 37 degrees C, during acute severe hypothermia at T(b)= 25 degrees C and on rewarming to 37 degrees C. Comparisons were made between rats without (euthermic, n= 6) and with (acclimated, n= 7) prior exposure to lower ambient temperatures and shorter photoperiod, simulating adaptation to winter conditions. In both groups of rats, acute hypothermia to T(b)= 25 degrees C shifted the baroreflex-RSNA curve slightly leftwards and downwards with decreases in the setpoint pressure and maximal gain, whereas it markedly impaired the baroreflex-HR curve characterized by decreases in response range by approximately 90% (P < 0.001), minimum response by approximately 10% (P < 0.05) and maximum gain by approximately 95% (P < 0.001), from that at T(b)= 37 degrees C. All parameters were restored to precooling levels on rewarming. Electrical stimulation of cardiac vagal efferents induced a voltage-related bradycardia, the magnitude of which was partially reduced during acute hypothermia, and there was a significant prolongation of the electrocardiogram intervals indicating a delay in cardiac conduction. Mild suppression of baroreflex control of RSNA could contribute to hypothermic hypotension and may primarily reflect an effect of T(b) on central drive. The marked attenuation of the baroreflex control of HR during hypothermia was likely to be due to an impairment of both the central and peripheral components of the reflex arc. Baroreflex control of RSNA and HR was similar between both groups of rats, which implied that the control was non-adaptive on chronic cold exposure.

Electrocardiographic changes in hypothermia

With the clinical use of cold cardioplegia, or total body hypothermia, it is crucial that critical care physicians and nurses be aware of the electrocardiographic changes related to hypothermia. Similar changes also occur with accidental exposure to cold. We report and discuss a patient who presented with typical electrocardiographic changes upon accidental exposure to cold.

Prolonged resuscitation in acute deep hypothermia

A case report is described with successful outcome of prolonged cardiopulmonary resuscitation in a 30-year-old man suffering from acute deep hypothermia. His lowest temperature recorded was 23 degrees C. Continuous external cardiac massage was required for a total of 4.5 h whilst rewarming was instituted. The patient eventually left hospital with no permanent sequelae. A review of hypothermia follows, emphasising some important management principals and pitfalls.