Effect Of Prolonged Hypothermia Research Articles

Effect of Prolonged Therapeutic Hypothermia on Intracranial Pressure, Organ Function, and Hospital Outcomes Among Patients with Aneurysmal Subarachnoid Hemorrhage

Global cerebral edema (GCE) with subsequent refractory intracranial hypertension complicates some cases of aneurysmal subarachnoid hemorrhage (aSAH), and typically is associated with poorer outcome. Treatment options for refractory intracranial pressure (ICP) cases are limited to decompressive hemicraniectomy (DHC) and targeted temperature management (TTM) with induced hypothermia (32-34°C). No outcomes comparison between patients treated with either or both forms of refractory ICP therapy exists, and data on the effect of prolonged hypothermia on ICP and organ function among patients with aSAH are limited. This is a retrospective study of aSAH patients who underwent DHC and/or prolonged hypothermia (greater than 48h) for refractory ICP (i.e., ICP >20mmHg after osmotherapy) in the intensive care unit of a single, tertiary-care academic center. Nineteen individuals with aSAH underwent TTM with or without DHC; sixteen patients underwent DHC alone. The patients in TTM group were younger (median age 44years) than the DHC without TTM population (median age 60years). TTM was started on median day 2 with a median duration of 7days. There were no significant group differences in survival to discharge (59% vs. 69%) or in the mean modified Rankin score on follow-up (3.6 vs. 3.7), despite the TTM group having longer hospital length of stay (24 vs. 19days, p=0.03), longer duration of mechanical ventilation (20 vs. 9days, p=0.04), a higher cumulative fluid balance (12.8 vs. 5.1L, p=0.01), and higher APACHEII scores. The median maximal ICP decreased from 23.5 to 21mmHg within 24h of hypothermia initiation. There were no significant differences in other markers of end-organ function (respiratory, hematologic, renal, liver, and cardiac), infection rate, or adverse events between groups. Use of prolonged TTM among aSAH patients with GCE and refractory ICP elevations is associated with a longer duration of mechanical ventilation but is not different in terms of neurological outcomes measured by modified Rankin score or organ function outcomes compared to patients who received DHC alone.

Cerebrovascular autoregulation after rewarming from hypothermia in a neonatal swine model of asphyxic brain injury

After hypoxic brain injury, maintaining blood pressure within the limits of cerebral blood flow autoregulation is critical to preventing secondary brain injury. Little is known about the effects of prolonged hypothermia or rewarming on autoregulation after cardiac arrest. We hypothesized that rewarming would shift the lower limit of autoregulation (LLA), that this shift would be detected by indices derived from near-infrared spectroscopy (NIRS), and that rewarming would impair autoregulation during hypertension. Anesthetized neonatal swine underwent sham surgery or hypoxic-asphyxic cardiac arrest, followed by 2 h of normothermia and 20 h of hypothermia, with or without rewarming. Piglets were further divided into cohorts for cortical laser-Doppler flow (LDF) measurements during induced hypotension or hypertension. We also tested whether indices derived from NIRS could identify the LDF-derived LLA. The LLA did not differ significantly among groups with sham surgery and hypothermia (29 ± 8 mmHg), sham surgery and rewarming (34 ± 7 mmHg), arrest and hypothermia (29 ± 10 mmHg), and arrest and rewarming (38 ± 11 mmHg). The LLA was not affected by arrest (P = 0.60), temperature (P = 0.08), or interaction between arrest and temperature (P = 0.73). The NIRS-derived indices detected the LLA accurately, with the area under the receiver-operator characteristic curves of 0.81-0.96 among groups. In groups subjected to arrest and hypothermia, with or without rewarming, the slope of LDF relative to cerebral perfusion pressure during hypertension was not significantly different from zero (P > 0.10). In conclusion, rewarming did not shift the LLA during hypotension or affect autoregulation during hypertension after asphyxic cardiac arrest. The NIRS-derived autoregulation indices identified the LLA accurately.

The management of temperature during hypothermic cardiopulmonary bypass: II — Effect of prolonged hypothermia

In animals mild hypothermia (32-35 degrees C) reduces ischaemic brain injury, but this has not been investigated in humans. During hypothermic cardiopulmonary bypass (CPB) patients are made hypothermic (usually to 30-32 degrees C) but are then rewarmed at a time when they are still at risk of ischaemic brain injury. We investigated the feasibility and safety of maintaining mild hypothermia throughout the CPB period. Thirty adult cardiac surgical patients were randomized to either rewarming to 36-37 degrees C or to maintaining temperature at 34 degrees C without rewarming. On arrival in the recovery room, patients in the hypothermic group had a mean bladder temperature of 33.8 +/- 0.45 degrees C compared with 35.4 +/- 0.58 degrees C (mean +/- SD, P < 0.05) in the rewarmed patients. There were no differences between groups in intra- or postoperative blood loss or blood use, inotrope use, dysrhythmias, or myocardial infarction. The hypothermic group received more muscle relaxant for the treatment of shivering postoperatively. Our results suggest that mild hypothermia following CPB did not increase morbidity although larger studies are needed for confirmation.

The Effect of Prolonged Hypothermia on Cardiac Function in a Young Patient with Accidental Hypothermia

A 20-year-old man had accidental, prolonged, and severe hypothermia. Serial radionuclide ventriculography disclosed reduced myocardial contractility during hypothermia that resolved after warming. The effects of hypothermia on cardiac function are discussed.

43. Effects of prolonged hypothermia on skin grafts in rats: Kimiyoshi Tsuji and William W. Shingleton (Department of Surgery, Duke University, Durham, North Carolina)

43. Effects of prolonged hypothermia on skin grafts in rats: Kimiyoshi Tsuji and William W. Shingleton (Department of Surgery, Duke University, Durham, North Carolina)

41. Effect of Prolonged Hypothermia on Acutely Increased Intracranial Pressure

41. Effect of Prolonged Hypothermia on Acutely Increased Intracranial Pressure

43. Effect of Prolonged Hypothermia in Experimental Head Injuries Especially Histological Changes

43. Effect of Prolonged Hypothermia in Experimental Head Injuries Especially Histological Changes