Effect of incremental doses of sevoflurane on cerebral pressure autoregulation in humans

Abstract

We have examined cerebral pressure autoregulation while awake, and during 0.5 and 1.5 MAC of sevoflurane anaesthesia in 10 patients undergoing non-intracranial neurosurgical procedures. All patients received a standardized anaesthetic comprising premedication with temazepam 20 mg orally, a sleep dose of propofol, fentanyl 1 microgram kg-1 and vecuronium 0.1 mg kg-1. After tracheal intubation, the lungs were ventilated with a mixture of air and oxygen to mild hypocapnia. Routine monitors included ECG, continuous and intermittent non-invasive arterial pressure, pulse oximetry and end-tidal capnography. In addition, blood flow velocity (vmca) was measured by insonating the middle cerebral artery transtemporally using a 2-MHz transcranial Doppler probe. Cerebral pressure autoregulation was tested by increasing mean arterial pressure (MAP) by approximately 20 mm Hg using an infusion of phenylephrine and simultaneously recording vmca. The index of autoregulation (IOR) during each period of the study, calculated as the ratio of percentage change in estimated cerebral vascular resistance (CVRe = MAP/vmca) to percentage change in MAP, was compared using ANOVA. vmca during 0.5 and 1.5 MAC of sevoflurane anaesthesia was significantly lower than that while awake (mean 79 (SD 24), 54 (15) and 51 (12) cm s-1, respectively; P < 0.05). There was no significant change in vmca with the increase in MAP while awake, or during 0.5 or 1.5 MAC of sevoflurane anaesthesia and IOR was similar under the three conditions (0.82 (0.11), 0.83 (0.04) and 1.0 (0.03), respectively). We conclude that cerebral pressure autoregulation remained intact during sevoflurane anaesthesia in humans.

S(+)-ketamine/propofol maintain dynamic cerebrovascular autoregulation in humans

“…In humans sevoflurane concentrations 1.5 MAC did not affect static cerebrovascular autoregulation. [20][21][22] However, studies in rats have shown that higher concentrations of sevoflurane (2.0 MAC) impair static cerebrovascular autoregulation in a fashion similar to other volatile anesthetics. 23 The dynamic component of cerebrovascular autoregulatory response, which appears to be a more sensitive indicator of altered physiology than the static component, was intact with 1.5 MAC sevoflurane, 24 but delayed with 2.0 MAC sevoflurane during the present investigation.…”

Fentanyl is more effective than remifentanil at preventing increases in cerebral blood flow velocity during intubation in children

“…Like all other volatile agents, sevoflurane causes dose-dependent cerebral vasodilatation, 20 however this effect is not as pronounced as it is with isoflurane. 16 Sevoflurane has been shown to effectively preserve cerebral blood pressure autoregulation 21 and cerebrovascular CO 2 reactivity. 22 In addition, induction and maintenance of anesthesia for children with sevoflurane represents common pediatric practice.…”

A comparison of propofol and sevoflurane anaesthesia: effects on aortic blood flow velocity and middle cerebral artery blood flow velocity*

“…However, in the presence of preserved autoregulation changes in MAP values do not result in relative changes in CBFv. It has been shown that autoregulation is preserved during propofol anaesthesia and during sevoflurane anaesthesia up to a concentration of 1.5 MAC [7,21,22,36]. Therefore, the reduction in MAP values during anaesthesia with either anaesthetic agent, cannot explain the observed reduction of CBFv values.…”