Cerebral metabolic rate of oxygen, intracranial tension and blood flow equivalent during isoflurane or sevoflurane anaesthesia in brain surgery

الملخص EN

Patients: This study was done in the Neurosurgical Department of Assiut University Hospital.

Twenty-eight patients of ASA physical status 1-11, aged 18-55 years, subjected to craniotomies for supratentorial brain tumour were included.

They were randomly allocated into two groups to receive either isoflurane (group I) or sevoflurane (group II) anaesthesia.

Method: Cerebral venous monitoring through jugular bulb catheterization to allow assessment of global oxygen delivery adequacy.

A fiberoptic extradural sensor was inserted in extradural space to monitor the ICP.

Anaesthesia was induced by thiopentone/ fentdnyl/pepecurium/isojlurane in group I, and thiopentone/fentanyl/pepecurium /sevoflurane in- group II, Anaesthesia was maintained with 1.5 MAC (1.5%) isoflurane in group I and 1.5 MAC (3%) sevoflurane in group II in Fi02 100%.

The patients were mechanically ventilated in such a rate to maintain PaC02 between 32-35 mmHg.

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Mean arterial blood pressure (MAP), intracranial pressure, arterial and jugular venous blood gases, arterial and jugular venous lactate concentrations were measured and times of recovery parameters were recorded.

Cerebral perfusion pressure (CPP), arterial oxygen content (CaOJ, jugular venous oxygen content (CjvOi), arteriojv.gular venous oxygen content difference (AJVDO^, cerebral oxygen extraction ratio (OER), arteriojugular lactate difference (AJVLD), lactate oxygen index (LOI), cerebral blood flow equivalent (CBF equivalent) were calculated.

Times elapsed till recovery parameters occurred were recorded.

Results: Effects of isoflurane and sevoflurane on the previous variables were compared.

We found that both anaesthetics reduced MAP and ICP after induction and tumour excision but increased them after intubation and skin incision.

Both anaesthetics improved CPP along the operative time to a relatively similar extent.

Progressive increase in Cjv02 and CBF-equivalent were associated with progressive decrease in AJVD02 and OER with increased deepness of anaesthesia in both studied groups.

These effects were more apparent with sevoflurane group than with isoflurane group, which may be due to the reduction in CMR02 relative to CBF in sevoflurane group, more than in isoflurane group.

Lactate oxygen index was nearly within the normal range in the two studied groups, but it progressively decreased to a relatively similar extent along the lime of surgery in the two studied groups.

This may be due to aerobic shift of the brain metabolism.

Recovery parameters occurred earlier in sevoflurane than isoflurane anaesthesia In conclusion, the results of this study postulated that both sevoflurane and isoflurane relatively maintain CBF/CMR02 ratio but isoflurane has greater capability to preserve this coupling.

Sevoflurane confer rapid recovery, which would facilitate early postoperative evaluation in the neurosurgical setting.

So sevoflurane appears to be ideal for neuroanaesthetic practice as conventionally used isoflurane.