Dose effect of sevoflurane and isoflurane anesthetics on cortical blood flow during controlled hypotension in the pig

Abstract

Background: The ability of the brain to preserve adequate cerebral blood flow (CBF) during alterations in systemic perfusion pressure is of fundamental importance. At increasing concentrations, isoflurane and sevoflurane have been known to alter CBF, which may be disadvantageous for patients with increased intracranial pressure. The aim was to examine the effects of isoflurane and sevoflurane at increasing minimum alveolar concentrations (MAC) on CBF, during controlled hypotension. Methods: We studied eight pigs during variations in perfusion pressure induced by caval block (100, 60, 50, and 40 mmHg) under normocapnia. CBF was measured locally in a defined area (4  5 measurement points covering 1 cm 2 ) of the motor cortex using laser Doppler perfusion imaging. Physiological variables, assessed by analysis of arterial O 2 and CO 2 , hemoglobin and hematocrit, were controlled. CBF was measured during propofol (10 mg  kg -1  h -1 ) and fentanyl (0.002 mg  kg -1  h -1 ) anesthesia, and then during anesthesia with either isoflurane or sevoflurane (given in random order) at increasing MAC (0.3-1.2). After a washout period, the measurements were repeated with the other gas.Results: CBF was significantly higher in the cortex during normotensive (control) settings, MAP $100 mmHg, compared with during hypotension (MAP 40-60 mmHg). Neither different anesthetic nor MAC or local measurement sites were found to influence CBF at any perfusion pressure. Conclusion: In this experimental model, the effect of hypotension on CBF was not altered by the anesthetics used [isoflurane, sevoflurane (MAC 0.3-1.2) or propofol (10 mg  kg -1  h -1 )]. In this aspect (cortical tissue perspective), these volatile agents appear as suitable as propofol for neurosurgical anesthesia for patients at risk.

Dose-dependent effect of isoflurane on regional cerebral blood flow in anesthetized macaque monkeys

“…Previous human and animal studies indicate that the induction of isoflurane results in cerebral vasodilatation and has evident effects on cerebral blood flow (CBF), cerebral blood volume (CBV), permeability, neurovascular coupling, neuron functionality [1, 5, 7, 8, 12, 13, 16]. Increased CBF and reduced rate of cerebral oxygen consumption (CMRO2) have been observed in the animal and human studies [1, 12].…”

Low perfusion pressure during CPB may induce cerebral metabolic and ultrastructural changes

“…In a recent paper, cortical perfusion was assessed in pigs with isoflurane anesthesia and induced hypotension by caval block. No effect on cerebral perfusion by isoflurane 0.3 -1.2 MAC was seen (Kimme et al, 2007).…”

Effects of Sevoflurane and Propofol on the Optic Nerve Sheath Diameter in Patients Undergoing Laparoscopic Gynecological Surgery: A Randomized Controlled Clinical Studies 

“…Third, in our study, sevo urane was maintained at 1-1.5 minimal alveolar concentration (MAC) while we do not record values of end-tide concentrations of sevo urane (Etsevo). Animal studies suggest that cerebral blood ow may not be changed when Etsevo is 0.3-1.5MAC [39]. Artru et al nd ICP is not changed when sevo urane is 0.5MAC 1.0MAC or 1.5MAC in neurosurgery patients [40].We guess that small changes in Etsevo during 0.5-1.5MAC may not have signi cant effects on cerebral blood ow .Fourth, Whiteley et al suggest that ONSD is positively correlated with MAP [25].In our study ,there are no signi cant differences between Group S and Group P at different time points and that is why we ignore the effect of blood pressure on ONSD.…”