[Infusion or repetitive bolus injection? A clinical study of midazolam/fentanyl and diazepam/fentanyl combination anesthesia in neurosurgical operations].

The objectives of this study were to compare two narcotic/benzodiazepine combinations given either as continuous infusion or intermittent bolus injections in neurosurgical patients. 24 patients scheduled for elective craniotomy were investigated. They were assigned randomly to four different groups for treatment. Groups 1 and 2 received a combination of midazolam and fentanyl, groups 3 and 4 a combination of diazepam and fentanyl. Anaesthesia was maintained either by continuous infusion (groups 1 and 3) or intermittent bolus injections (groups 2 and 4). At six key intervals cardiovascular variables were compared. Furthermore, total drug dosage requirements were measured and compared. Except for measurement 3 (skin incision), cardiovascular dynamics were not markedly different between bolus and infusion groups. Haemodynamic response to skin incision was less in both bolus groups. Furthermore, the bolus technique revealed a non-significant reduction in total drug dosage requirements in the bolus groups. Our data indicate that for neurosurgical anaesthesia conventional bolus injection of intravenous anaesthetics is superior to continuous infusion with respect to intraoperative haemodynamics. The typically reduced level of pain with short peaks only, characteristic for neurosurgical operations, is one of the factors contributing to these surprising results. Furthermore, the simple method of infusion chosen influences the results decisively. Certain advantages might be achieved by the use of sophisticated pharmacokinetic infusion models. Total drug dosage requirements were reduced in the bolus groups mainly because of the typical anaesthetic requirements of craniotomy, disposing it for bolus technique.