The Relation between Tourniquet Hypertension and Bispectral Index in Patients Undergoing a Total Knee Arthroplasty / 대한마취과학회지

BACKGROUND: Tourniquet hypertension (TH) may develop from an autonomic reflex consequent to the sensitization of the central nervous system (CNS) due to ischemia of the affected limb and noxious surgical stimulation. TH could be preventable when anesthetic depth is sufficient enough to block plastic changes of the CNS during an operation. This study was aimed to evaluate the efficacy of the bispectral index (BIS) to predict development of TH by assessing correlations between BIS changes and hemodynamic changes during the skin incision. METHODS: Sixty patients who had undergone a total knee arthroplasty with a pneumatic tourniquet during isoflurane anesthesia were selected, and the samples were randomly divided into two groups: BIS 30 (30 - 39) and BIS 40 (40 - 49). Several variables such as BIS, mean arterial pressure (MAP), heart rate (HR) and end tidal concentraion of isoflurane were monitored during the operation. TH was defined as more than a 30% increase in MAP compared with the baseline values during the skin incision. The correlation between BIS changes and MAP and HR changes, and the incidence of TH between BIS groups were compared. RESULTS: The MAP and HR were meaningfully increased in both the BIS 30 and the BIS 40 groups (P < 0.05), but no significant correlations were found between the BIS changes and the MAP and HR changes during the skin incision. The incidence of intraoperative hypertension was not different between the BIS groups. The BIS of the patients who had TH was not different from those who did not have TH. CONCLUSIONS: BIS may not reflect the changes of the CNS and autonomic nervous system induced by noxious surgical stimulation during an operation, and BIS changes during a skin incision cannot be a predictor of TH.

The Effect of Brain Hypothermia on Brain Edema Formation after Transient Ischemia / 대한구급학회지

BACKGOUND: When ischemia reduces blood supply, hypothermia remains the sine qua non for reducing demand. An alternative to whole body deep hypothermia is an isolated cerebral hypothermia via perfusion of cooled blood through one internal carotid artery. The goal of this study was to evaluate the effect of isolated cold hemisphere perfusion during the cerebral ischemia on the formation of brain edema. METHODS: The studies were designed to perfuse a saline solution into both carotid arteries with a different temperature (left 15degreesC, right 38degreesC) in the same animal. Cerebral ischemia was produced by a combination of the both carotid artery saline perfusion and systemic hypotension to a mean arterial blood pressure of 40 mmHg for 10 minutes. Ninety minutes after reperfusion, brain water contents were measured using the kerosene/bromobenzene density gradient and compared with warm saline perfusion and normal control group. RESULTS: Brain water content of cold saline perfusion hemisphere measured at 90 minutes after ischemia showed decreased water content compared to warm saline perfusion hemisphere (p<0.05). CONCLUSIONS: Cerebral cold saline perfusion during the ischemia decreased the formation of brain edema. These results showed hypothemia is one of the most effective ways to protect brain from the ischemia.