Cerebral blood flow, cerebral metabolic rate of oxygen and relative CO2 reactivity during neurolept anaesthesia in patients subjected to craniotomy for supratentorial cerebral tumours

In 10 patients subjected to craniotomy for supratentorial cerebral tumours in neurolept anaesthesia, cerebral blood flow (CBF) and cerebral metabolic rate of oxygen (CMRO2) were measured twice peroperatively by a modification of the Kety & Schmidt technique, using 133Xe. The relative CO2 reactivity was assessed indirectly as the % change of the arteriovenous oxygen difference (AVDO2) per mm change in PaCO2. The patients were premedicated with diazepam 10-15 mg perorally. For induction, thiopentone 4-6 mg/kg, droperidol 0.2 mg/kg and fentanyl 5 micrograms/kg were used, and for maintenance N2O 67% and fentanyl 4 micrograms/kg/h. During the first flow measurement the median and range of CBF was 30 ml/100 g/min (range 17-45), of AVDO2 8.0 vol % (range 4.1-9.5), and of CMRO2 2.28 ml O2/100 g/min (range 1.57-2.84). During the second CBF study, AVDO2 increased to 9.3 vol % (range 3.4-11) (P less than 0.05), and CMRO2 increased to 2.51 ml O2/100 g/min (range 1.88-3.00) P less than 0.05, while CBF was unchanged. The CO2 reactivity was present in all studies, median 1.8%/mmHg (range 0.5-15.1). The correlation coefficients between jugular venous oxygen tension/saturation, respectively, and CBF were high at tensions/saturations exceeding 4.0 kPa and 55%, indicating that hyperperfusion is easily unveiled by venous samples from the jugular vein during this anaesthesia.     

Perioperative management of face-to-face craniopagus twins separation

Craniopagus conjoining represents a complex and challenging issue for neurosurgeons as well as for anesthesiologists. A rare face-to-face case of conjoined twins underwent surgical separation and presented peculiar differences compared with those already reported in the literature. Even in cases lacking large cerebrovascular sinus connections, the impending risk of large blood loss and hemorrhagic shock in the infant requires a high level of surveillance and the institution of invasive monitoring.     

No-glucose strategy influences posterior cranial fossa tumors' postoperative course: introducing the Glycemic Stress Index

In a selected patient population, we evaluated the glycemic response to different infusional policies in the management of posterior cranial fossa tumor (PFT) removal. We analyzed the perioperative course, prospectically collected, of 137 children undergoing 150 surgical procedures. Patients were divided in two groups according to different intraoperative fluids (group A, 2.5% glucose; group B, crystalloids). In group B glycemia remained below 125 mg dl⁻¹, while group A showed persistently supranormal glycemic plasma values, reaching statistical significance at the end of surgery (P < 0.018). As no perioperative mortality occurred and no differences were found between groups regarding PICU respiratory or infectious complications, PICU length of stay (LOS) was assumed as the main outcome indicator. LOS was not influenced by group A or B inclusion, while a new indicator, namely the Glycemic Stress Index (GSI), representing both glycemic intraoperative change and procedure length, showed significantly different results in the study groups (P = 0.004). Our clinical experience suggests that both intraoperative glucose-free solutions are safe, and GSI can be a useful tool to identify prolonged PICU stay patients.     

神经外科麻醉时麻醉药物的选择

大多数情况下,麻醉药物的选择对神经外科手术的过程和患者的转归并无决定性影响。深入理解CNS的生理学、神经生理学和麻醉药物对大脑的影响,掌握熟练的麻醉技术,才是决定神经外科手术患者转归的关键。     

The effect of metoprolol upon blood pressure, cerebral blood flow and oxygen consumption in patients subjected to craniotomy for cerebral tumours

Hypertension and cerebral hyperperfusion are often seen in the immediate postoperative period after craniotomy for supratentorial tumours. Metoprolol is known to attenuate the postoperative hypertensive response after hypotensive anaesthesia and this study was carried out to evaluate the effect of metoprolol on cerebral blood flow (CBF) and cerebral metabolic rate of oxygen (CMRo₂) before extubation and cerebral arteriovenous oxygen content difference (AVDo₂), mean arterial blood pressure (MABP), Pao₂ and Paco₂ in a 180–min period after extubation. Twenty patients anaesthetized with thiopentone, fentanyl, nitrous oxide 67%, and halothane 0.5% were randomized to receive intravenous metoprolol or placebo at the end of the peroperative period. There were no significant differences in CBF– and CMRo₂ values between the two groups. In the period between closure of the dura and 5 min after extubation, an increase in MABP was observed in the control group ( P < 0.05), but not in the metoprolol group. During the same period a decrease in AVDo₂ was observed in both groups ( P < 0.05); during the next 10 min an increase was observed, but with no difference in AVDo₂ values between the groups. A higher level of Pao₂ in the metoprolol group was observed in the postoperative period. These findings suggest that peroperative treatment with metoprolol reduces postoperative MABP but does not influence the cerebral blood flow and metabolism.     

Cerebral arteriovenous difference of oxygen during gradual and sudden increase of the concentration of isoflurane for induction of deliberate hypotension

In 20 patients undergoing surgery for cerebral aneurysms, hypotension was induced with either gradual (over 5 min) or sudden increase of inspiratory concentration of isoflurane from 0.5% to 3%. Both modes elicited the same speed of induction of deliberate hypotension and similar decreases of cerebral arteriovenous difference of oxygen (AVDo2). The overall median values of mean arterial blood pressure decreased from 75.5 (range 64-90) mmHg (10 (8.5-12.0) kPa) to 55 (40-66) mmHg (7.3 (5.3-8.8) kPa) and the overall AVDo2 decreased from 6.75 ml/100 ml (3.8-9.4 ml/100 ml) to 5.85 ml/100 ml (2.6-8.1 ml/100 ml) within 10 min. It is concluded that irrespective of gradual or sudden increase of isoflurane concentration, cerebral blood flow is in surplus of metabolism and a favourable oxygen demand/supply ratio is maintained during induction of deliberate hypotension by isoflurane below 2.5 MAC.     

CBF and CMRo2 during craniotomy for small supratentorial cerebral tumours in enflurane anaesthesia. A dose-response study

In 14 patients with supratentorial cerebral tumours with midline shift less than or equal to 10 mm, cerebral blood flow (CBF) and cerebral metabolic rate of oxygen (CMRO2) were measured twice on the contralateral side of the craniotomy, using a modification of the Kety & Schmidt method. For induction of anaesthesia, thiopental, fentanyl and pancuronium were used. The anaesthesia was maintained with enflurane 1% in nitrous oxide 67%. Moderate hypocapnia to a level averaging 4.3 kPa was achieved. The patients were divided into two groups. In Group 1 (n = 7), 1% enflurane was used throughout the anaesthesia, and CBF and CMRO2 measured about 70 min after induction averaged 30.1 ml 100 g-1 min-1 and 1.98 ml O2 100 g-1 min-1, respectively. During the second CBF study 1 h later, CBF and CMRO2 were unchanged (P greater than 0.05). In Group 2 (n = 7), the inspiratory enflurane concentration was increased from 1 to 2% after the first CBF measurement. In this group a significant decrease in CMRO2 was observed, while CBF was unchanged. In six patients EEG was recorded simultaneously with the CBF measurements. In patients subjected to increasing enflurane concentration (Group 2), a suppression in the EEG activity was observed without spike waves. It is concluded that enflurane induces a dose-related decrease in CMRO2 and suppression in the EEG activity, whereas CBF was unchanged.