A comparison of two doses of mannitol on brain relaxation during supratentorial brain tumor craniotomy: a randomized trial.

BACKGROUND: Twenty percent mannitol is widely used to reduce brain bulk and facilitate the surgical approach in intracranial surgery. However, a dose-response relationship has not yet been established. In this study, we compared the effects of 0.7 and 1.4 g·kg(-1) mannitol on brain relaxation during elective supratentorial brain tumor surgery. METHODS: In this prospective, randomized, double-blind study, we enrolled 80 patients undergoing supratentorial craniotomy for tumor resection. Patients were assigned to receive 0.7 g·kg(-1) (group L) or 1.4 g·kg(-1) (group H) of 20% mannitol at surgical incision. Brain relaxation was assessed immediately after opening of the dura on a scale ranging from 1 to 4 (1 = perfectly relaxed, 2 = satisfactorily relaxed, 3 = firm brain, 4 = bulging brain). RESULTS: There was no significant difference between the 2 groups regarding age, sex, body mass index, and brain tumor localization or size. In group L 52.5% of patients and in group H 77.5% of patients presented a midline shift (P = 0.03). The median scores of brain relaxation (interquantile range) were 2.0 (1.75-3) and 2.0 (1-3) (P = 0.16 for patients in group L and H, respectively). We then used a proportional odds model to adjust for this unbalanced distribution and to assess the group effect (low-dose versus high-dose mannitol) on brain relaxation scores. When adjusted for the presence of midline shift, the use of a higher dose of mannitol resulted in an odds ratio of 2.5 (P = 0.03). This indicates that, considering the effect of a midline shift, the odds of having a 1-level improvement in relaxation score in patients who received a higher dose of mannitol (group H) was 2.5 times as large as the odds for the low-dose group. The odds ratio of 0.29 (P = 0.007) for the midline shift indicates that its occurrence was associated with a higher probability of a lower relaxation score, on average. CONCLUSION: In this study, we show that 1.4 g·kg(-1) of 20% mannitol results in equivalent brain relaxation scores as 0.7 g·kg(-1) in patients undergoing craniotomy for supratentorial brain tumor. When corrected for the presence of midline shift, this study reveals that patients in the high-dose group had significantly more chances of obtaining a better relaxation score compared with the lower-dose group.

The effect of sedation on intracranial pressure in patients with an intracranial space-occupying lesion: remifentanil versus propofol.

BACKGROUND: In this study, we compared the effect of light sedation with remifentanil versus propofol on intracranial (ICP) and cerebral perfusion pressure (CPP) of patients undergoing stereotactic brain tumor biopsy under regional anesthesia. METHODS: This was a prospective, open-label, randomized, and controlled study. Forty patients undergoing stereotactic brain tumor biopsy under regional anesthesia were randomized into two groups to receive remifentanil or propofol titrated to a level of four on the modified Assessment of Alertness/Sedation Scale. ICP was measured via the biopsy needle. RESULTS: At the targeted level of sedation, the rates of infusion for remifentanil and propofol were, respectively, 4.2 +/- 1.8 microg x kg(-1) x h(-1) and 4.3 +/- 2.5 mg x kg(-1) x h(-1). At the time of ICP measurement, patients in the remifentanil group had a slower respiratory rate (11/min +/- 3 vs 15 per min +/- 3, P = 0.0001) and a higher PCO2 (48.3 +/- 6.2 mm Hg vs 43.1 +/- 5.5 mm Hg, P = 0.009) than patients in the propofol group. The mean was similar for both groups, 19.0 +/- 11.9 mm Hg vs 16.4 +/- 11.1 mm Hg for remifentanil and propofol, respectively (P = 0.48). Higher mean arterial blood pressure in the remifentanil group (101.1 +/- 13.7 mm Hg vs 85.8 +/- 12.7 mm Hg, P = 0.0008) resulted in a higher CPP than the propofol group: 82.0 +/- 19.0 mm Hg vs 69.5 +/- 17.0 +/- 19.0 mm Hg (P = 0.03). CONCLUSION: Light sedation with remifentanil does not result in a higher ICP than propofol in patients undergoing stereotactic brain tumor biopsy. CPP might be better preserved with remifentanil.

Cisatracurium-induced neuromuscular blockade is affected by chronic phenytoin or carbamazepine treatment in neurosurgical patients.

The effect of chronic anticonvulsant therapy (CAT) on the maintenance and recovery profiles of cisatracurium-induced neuromuscular blockade has not been adequately studied. In this study, we compared the pharmacokinetics and pharmacodynamics of cisatracurium after a prolonged infusion in patients with or without CAT. Thirty patients undergoing intracranial surgery were enrolled in the study: 15 patients under CAT (carbamazepine and phenytoin, Group A) and 15 controls receiving no anticonvulsant therapy (Group C). Anesthesia was standardized and both groups received a bolus of cisatracurium followed by an infusion to maintain a 95% twitch depression. A steady-state was obtained and the infusion was kept constant for 2 additional hours. Neuromuscular blockade was then allowed to spontaneously recover. Blood samples were taken for measurement of cisatracurium plasma concentration during the steady-state period (Cp(ss)95) and at various times during recovery. Demographic and intraoperative data were similar. CAT resulted in faster 25% and 75% recovery of the first twitch. The rate of infusion of cisatracurium needed to maintain a 95% twitch depression at steady-state was 44% faster in Group A (P < 0.001). The clearance of cisatracurium was significantly faster in Group A when compared with Group C (7.12 +/- 1.87 versus 5.72 +/- 0.70 L . kg(-1) . min(-1), P = 0.01). The Cp(ss)95 was also significantly larger in Group A (191 +/- 45 versus 159 +/- 36 ng/mL, P = 0.04). In addition, patients receiving CAT had a 20% increase in the clearance of cisatracurium that, in turn, resulted in a faster recovery of neuromuscular blockade after an infusion of the drug. Also, patients under CAT had a 20% increase in their Cp(ss)95, indicating an increased resistance to the effect of cisatracurium.

The effect of propofol sedation on the intracranial pressure of patients with an intracranial space-occupying lesion.

The fear of producing CO(2) retention and a secondary increase of intracranial pressure (ICP) sometimes precludes the use of sedation for the spontaneously breathing patient in the presence of an intracranial space-occupying lesion. In this study we assessed the effect of moderately deep propofol sedation on the ICP of patients undergoing stereotactic brain tumor biopsy under regional anesthesia. Thirty patients were randomized into 2 groups to receive propofol titrated to a level of 2 on the Observer's Assessment of Alertness/Sedation Scale or no sedation. ICP was measured via the biopsy needle. Preoperative data were similar in both groups. During surgery, patients receiving propofol had a higher arterial Pco(2) (48 +/- 8 mm Hg versus 41 +/- 3 mm Hg; P = 0.005) (95% confidence interval, 43-53 mm Hg and 39-43 mm Hg, respectively), resulting in a lower arterial pH (P = 0.002) than patients in the no-sedation group. The median ICP (95% confidence interval) for both groups was similar-13 mm Hg (8.2-16.2 mm Hg) and 15 mm Hg (8.3-21.7 mm Hg)-for the propofol and no-sedation groups, respectively (P = 0.66). Cerebral perfusion pressure was lower in the propofol group (76 +/- 18 mm Hg versus 89 +/- 18 mm Hg; P = 0.003). Moderately deep propofol sedation does not result in a higher ICP than no sedation in patients undergoing stereotactic brain tumor biopsy. Further studies are needed to assess the effect on ICP of other sedative medications.