Cerebral Circulation and Metabolism during Enflurane Anesthesia in Man

The effects of enflurane anesthesia on cerebral blood flow (CBF) and cerebral metabolic rate for oxgen (CMRo2) were studied in patients. The patients were divided into two groups according to the deph of anesthesia, I.e.,group I, 2% inspried enflurane, and group II, 3.5% inspired enfulurane. Cerebral perfusion pressure (CCP) was maintained above 60 mmHg with phenylephrine. In group I, patients were studied before surgery, while in group II, the measurements were performed before and surgery. In groupe I (enflurane concentration in the arterial blood, 15mg/dl),mean CBF and CMRo2 were 53 and 2.8 ml/100g/min,respectively. These values were not significantly different from CBF (46ml/100g/min) and CMRo2 (3.1 ml/100g/min) in the awake patients. The electroencephalogram (EEG) showed pregominant activities between 12 and 15 Hz with amplitude of 50 to 100чV with nterior dominance. In group II before surgery (enflurance concentration, 27 mg/dl), mean CBF (61 ml/100g/min) and CMRo2 (2.6 ml/100g/min) were significantly diferent from the awake values, while the EEG showed frequent spikes and suppression. In group II during surgery (enflurance concentration 27 mg/dl), mean CBF (67 ml/100g/min) and CMRo2 (2.6 ml/100g/min) were not defferent from the values before surgery despite significant EEG changes (decreased spiking increased suppression) The results indicate that enflurane is a cerebral vasodilator and causes an increse in CBF and a decrese in CMRo2 in man at an anesthetic level characterized by frequent spikes and suppression on the EEG. Nochanges in CBF and CMRo2 despite EEG changes with surgical stimulation suggest redistribution of flow coupled with metabolism.

Anesthetics

enflurane

Brain

blood flow

oxygen consumption

glicose consumpution