Effect of Propofol on Cerebral Circulation and Autoregulation in the Baboon

Abstract

The purpose of this study was to investigate the effect of propofol on cerebral blood flow, cerebral metabolism, and cerebrovascular autoregulatory capability. Seven anesthetized baboons were given propofol at three different infusion rates. An infusion of 3 mg.kg-1.h-1 caused minimal changes, but infusion rates of 6 and 12 mg.kg-1.h-1 decreased cerebral blood flow by 28% and 39%, respectively. The changes in cerebral metabolic rate of oxygen were not statistically significant. However, with the two higher infusion rates, there was a trend toward decrease, by 5% and 22%, respectively, for the cerebral metabolic rate of oxygen, and by 18% and 36% for the cerebral metabolic rate of glucose. A 25-30 mm Hg increase in arterial blood pressure had no influence on cerebral blood flow. Replacement of nitrous oxide by nitrogen had no significant influence on cerebral blood flow or metabolism. It is concluded that propofol causes a dose-dependent decrease in cerebral blood flow. However, the study does not prove that this decrease in cerebral blood flow is accompanied by the same degree of decrease in cerebral metabolism. Further studies are clearly needed to clarify propofol's influence on the coupling between cerebral metabolism and blood flow. The physiologic responsiveness of the cerebral circulation to alterations in arterial pressure is well preserved. Propofol appears to prevent the metabolic stimulation and increased cerebral blood flow that has been associated with the administration of nitrous oxide.

Effect of propofol on hepatic blood flow and oxygen balance in rabbits

“…The dose-dependent effect of propofol on organ oxygen balance has been reported previously. For instance, in anesthetized baboons, 20 it was found that different propofol infusion rates had different effects on cerebral oxygenation.…”

Cerebral Oxygen Saturation Measured by Near-infrared Spectroscopy and Jugular Venous Bulb Oxygen Saturation during Arthroscopic Shoulder Surgery in Beach Chair Position under Sevoflurane-Nitrous Oxide or Propofol-Remifentanil Anesthesia

“…11 In contrast, propofol reduces CBF greater than CMRO 2 , resulting in a decrease of the CBF/CMRO 2 ratio. [12][13][14] Indeed, cerebral oxygen balance is better maintained by sevoflurane-based than by propofol-based anesthesia when patients are positioned supine. [15][16][17][18] In this context, it is also possible that the margin of safety against an impaired cerebral oxygenation would be greater with sevofluranebased than with propofol-based anesthesia in BCP.…”

Anesthetic Choice of Halothane Versus Propofol

“…Others have found no differences in focal ischemic outcome with halothane and propofol anesthesia. 2 Numerous mechanisms for the neuroprotective effect of propofol have been postulated, including decrement in CBF in conjunction with decreased cerebral metabolic rate for oxygen 19,20,31 and reduced cerebral electric activity. 4,32 The mechanism of reduced CBF with propofol remains unclear; however, a vascular origin is not likely because propofol causes vasodilation in isolated vessels.…”

“…14 -17 Nonvolatile agents such as propofol (2,6-di-isopropyl phenol) have also been shown to prevent neuronal injury in animal models of transient global 3 and focal cerebral ischemia. 18 Propofol reduces CBF and cerebral metabolic rate 19,20 ; however, its neuroprotective properties may be linked to activation of ␥-aminobutyric acid (GABA) A receptors 3 or through inhibition of synaptic glutamate 21 and catecholamine release. 4 While there is considerable evidence for ischemic neuroprotection by such anesthetic agents, there is little information concerning the possibility that anesthetic agents affect outcome from middle cerebral artery occlusion (MCAO), which is induced after cessation of the anesthetic agent.…”