The cerebral arterio‐venous oxygen content differences (AVDo₂) during halothane and neurolept anaesthesia in patients subjected to craniotomy

Abstract

In 20 patients subjected to craniotomy for supratentorial cerebral tumours, the haemodynamic changes during halothane and neurolept anaesthesia were evaluated by measuring mean arterial blood pressure (MABP) and cerebral arterio-venous oxygen content differences (AVDO2) repeatedly during the operation. Ten patients were given 0.5% halothane anaesthesia and ten patients neurolept anaesthesia. MABP, AVDO2 and PaCO2 were measured after induction of anaesthesia, before and after incision, after opening and closure of the dura, at the time of extubation and 1 h later. Concerning MABP and PaCO2, no significant difference between the two groups was found. In both groups an increase in MABP was observed after incision (P less than 0.01 in the neurolept group and P less than 0.05 in the halothane group) and in the neurolept group after extubation (P less than 0.01). In both groups a decrease in AVDO2 was observed after incision (P less than 0.01) and after extubation (P less than 0.01 in the neurolept group and P less than 0.05 in the halothane group). During the operation AVDO2 values were significantly higher in the neurolept group (P less than 0.05). The results indicate that even a moderate increase in MABP after incision during neuroanaesthesia affects AVDO2 values, suggesting an increase in cerebral blood flow. The study suggests that autoregulation of cerebral blood flow might be better preserved during neurolept anaesthesia. A state of hyperperfusion of the brain after extubation was unveiled in both groups.

The effects of midazolam on cerebral blood flow and oxygen consumption Interaction with nitrous oxide in patients undergoing craniotomy for supratentorial cerebral tumours

“…21 Several studies in patients with cerebral tumours indicate global or regional loss of cerebral autoreg~lation.~,~ Moreover, studies during neurolept anaesthesia and halothane anaesthesia in patients with supratentorial tumours subjected to craniotomy indicate abolished cerebral autoregulation. 22 Work in dogs2 concluded that midazolam produced a dose-related decrease in CBF and CMRO,, but not to the same degree as other intravenous and volatile anesthetics. Another study in the same animal' indicated that small doses (0.2 mg/kg) of midazolam did not decrease CMRO,, but did decrease CBF.…”

According to which factors in severe traumatic brain injury craniectomy could be beneficial

“…[ 1 2 11 30 37 39 43 ] However, the role of DC recommended in patients with severe TBI and refractory IH still remains controversial, mainly due its efficacy and complications such as infections (3–7%), communicating hydrocephalus (20.7%), subdural hygroma (26%), herniation (27.6%), and postoperative seizures (14%). [ 2 14 15 19 24 47 56 ] There is also a hypothesis by Cooper et al . that an increase in cerebral blood flow after removing the bone flap cause obstruction in the decompressed brain exacerbating the existing acute brain edema.…”

Decompressive craniectomy in head injury

“…Subdural hygroma is the most common complication (26%) 23,41 , most often which respond to puncture only 23 7. Paradoxical herniation after lumber puncture in a case of DC 43 8. Hypotension in children during emergent craniotomy for trauma 44 9.…”