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October 16, 2007
3:30 PM - 5:00 PM
Room Room 120
Pharyngeal Cooling Decreased Brain Temperature and Glutamate Concentration during Resuscitation
Yoshimasa Takeda, M.D., Ph.D., Motomu Kobayashi, M.D., Hideki Taninishi, M.D., Toshihiro Sasaki, M.D., Kiyoshi Morita, M.D., Ph.D.
Anesthesiology & Resuscitology, Okayama University Medical School, Okayama, Japan
Introduction: Mild hypothermia is known to ameliorate neurological outcome after resuscitation in humans. If hypothermia can be initiated during resuscitation, glutamate concentration should be lowered and neurological outcome would be improved. The development of a technique that enables brain temperature to be immediately and selectively reduced is needed. Since bilateral common carotid arteries exist at 1 centimeter from the pharynx, cooling the pharyngeal region decreases brain temperature by cooling arterial blood without lowering systemic temperature. The present study was designed to evaluate the effects of pharyngeal cooling on brain temperature, systemic temperature, intracranial pressure and extracellular glutamate concentration during resuscitation in monkeys.

Methods: Japanese monkeys (7.5±2.4 kg) were divided into a control group (n=6) and a pharyngeal cooling group (n=3) and were anesthetised with 1% isoflurane. Cardiac arrest (12 min) was initiated with electrical stimulation. Changes in intracranial pressure and epidural, sub-cortical (3 cm below the cortical surface) and rectal temperatures were monitored during a 30-min resuscitation period. A micro-dialysis probe was inserted into the parietal cortex for the measurement of glutamate concentration. In the pharyngeal cooling group, a pharyngeal cuff was inserted into the pharynx and was perfused with water (5 °C) at the rate of 500 ml/min from the onset of resuscitation for 30 min.[figure1]Results: During cardiac arrest, epidural and sub-cortical temperatures decreased to 33.3±0.7 °C and 35.8±0.5 °C, respectively, in both groups. In the control group, however, epidural and sub-cortical temperatures increased with the initiation of resuscitation and reached 35.1±0.5 °C and 36.5±0.2 °C, respectively, 30 min later. In the pharyngeal cooling group, epidural and sub-cortical temperatures decreased and reached 31.1±1.5 °C and 32.4±1.3 °C, respectively, 30 min later. Rectal temperature was unchanged in both groups. During the resuscitation period, intracranial pressure increased to 30±16 mmHg (control) and 14±6 mmHg (pharyngeal cooling) and took 23±9 min (control) and 6±1 min (pharyngeal cooling) to become less than 10 mmHg. Extracellular glutamate concentration was unchanged during cardiac arrest in both groups and increased after the onset of resuscitation. The maximum concentration of extracellular glutamate was decreased in the pharyngeal cooling group (13 mol/l) compared to that in the control group (39 mol/l). The periods required for recovery of mean arterial blood pressure (>50 mmHg) were the same (4±1 min after onset of resuscitation) in the two groups.

Conclusions: Brain temperatures were decreased by the initiation of pharyngeal cooling without lowering of rectal temperature during the resuscitation period in monkeys. Since intracranial pressure and extracellular concentration of glutamate were lower in the pharyngeal cooling group, pharyngeal cooling could be a useful technique to protect the brain from ischemic injury during the resuscitation period in a clinic.

Anesthesiology 2007; 107: A1859
Figure 1