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.

Superficial cervical plexus block for transitional analgesia in infratentorial and occipital craniotomy: a randomized trial.

BACKGROUND: In this study, we compared the quality of transitional analgesia provided by bilateral superficial cervical plexus block (SCPB) or morphine following a remifentanil-based anesthesia for infratentorial or occipital craniotomy. METHODS: In this randomized controlled and double-blind study, 30 patients scheduled for infratentorial or occipital craniotomy were divided randomly into two groups: group morphine (morphine 0.1 mg·kg⁻¹ iv after dural closure and a SCPB performed with 20 mL of 0.9% saline at the end of the surgery) or group block (10 mL of 0.9% saline iv instead of morphine after dural closure and a SCPB performed with 20 mL of a 1:1 mixture of 0.5% bupivacaine and 2% lidocaine at the end of the surgery). Postoperative pain was assessed at one, two, four, eight, 12, 16, and 24 hr using an 11-point (0-10) numerical rating scale (NRS). Analgesia was provided with subcutaneous codeine. RESULTS: Average NRS scores were similar between the two groups at each time interval over the study period. The average scores (with 95% confidence interval) were 3.9 (3.4-4.4) and 4.3 (3.8-4.9) for the block and morphine groups, respectively (P = 0.25). The delay before administration of the first dose of codeine was not statistically different between the two groups: 25 min (5-2,880) vs 21.5 min (5-90), median and range for the block and morphine groups, respectively. The incidence of nausea and vomiting was similar between the two groups. CONCLUSION: Bilateral superficial cervical plexus block provides transitional analgesia that is clinically equivalent to morphine following remifentanil-based anesthesia in patients undergoing occipital or infratentorial craniotomies.

Recombinant human activated factor VII is thrombogenic in a rabbit model of cyclic flow reduction and does not reduce intra-abdominal bleeding.

Recombinant human activated factor VII (rHuFVIIa) can reduce bleeding but may be associated with arterial thrombosis. We hypothesized that rHuFVIIa would increase the occurrence of cyclic flow reductions (CFR) and reduce intra-abdominal bleeding in an experimental model. An adapted Folts' model of carotid artery lesion and stenosis was used. Twenty four rabbits were randomized to receive rHuFVIIa (group F) or placebo (group P) in a double-blind fashion. A standardized injury to the common carotid artery resulted in CFR and/or thrombosis. Hematological values, coagulation and thromboelastographic (TEG) variables were compared. Intra-abdominal bleeding was evaluated by measuring blood loss from standardized hepatosplenic lesions. The median number (range) of spontaneous CFR [group P: 6 (0-15); group F: 8 (0-16)] was comparable between groups. The number of induced CFR (by "shaking" of the artery) needed to avert thrombosis (group F: 2; group P: 0; p < 0.05) and the incidence of complete carotid artery thrombosis (group F: 3; group P: 0; p < 0.05) were higher in group F. Intra-abdominal bleeding was similar in both groups. TEG analysis demonstrated a hypercoagulable state in both groups but the magnitude of the change was statistically more important in group F. rHuFVIIa increases thrombosis in a rabbit model of carotid artery injury. The bleeding from hepatic and splenic lesions is not reduced by administration of rHuFVIIa despite a hypercoagulable state confirmed by standard TEG analysis.

Anesthetic technique does not affect the performance of a rabbit model of arterial cyclic flow reductions: a pilot study.

PURPOSE: Pentobarbital anesthesia is, typically, used in an experimental model of cyclic flow reductions (CFR) in rabbits. Our initial observations, using a more complete and effective isoflurane-based anesthetic technique, failed to reproduce findings reported previously. Consequently, we compared the effects of these two anesthetic techniques in the model. METHODS: A modified Folts' model of carotid artery lesion and stenosis was used. Twelve rabbits completed the experimental protocol: five in the pentobarbital group (P) and seven in the isoflurane group (I). The carotid artery was exposed and flow was reduced by application of a clamp. A standardized injury was performed by cross clamping the artery with a needle forceps and this produced CFR. The number of CFR and the duration of their occurrence were noted. The incidence of thrombosis was compared in each group as well as hemodynamic, hematologic and bleeding time values. RESULTS: The hematocrit value, platelet count and bleeding time were similar in both groups. The median number and range of CFR [group P: 9 (4-16) ; group I: 9 (5-14)] and the time span of effective CFR formation (group P: 39 +/- 17; group I: 38 +/- 25 min) were comparable in both groups. The incidence of complete thrombosis of the carotid artery was similar in both groups. CONCLUSIONS: The stability of the model is of short duration, but the occurrence of CFR is not affected by the type of anesthesia. Our findings suggest that the ideal duration of the experimental protocol should be between 30 and 45 min in order to maximize the number of animals still developing CFR.