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.


CONCLUSIONS
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.
Department of Anesthesiology, Montreal University Medical Centre, Montreal, Quebec, Canada.
Charlotte
C
Quentin
Sonia
S
Charbonneau
Robert
R
Moumdjian
Alexandre
A
Lallo
Alain
A
Bouthilier
Marie-Pierre
MP
Fournier-Gosselin
Michel
M
Bojanowski
Monique
M
Ruel
Marie-Pierre
MP
Sylvestre
Francois
F
Girard
D000368:Aged; D000768:Anesthesia, General; D001784:Blood Gas Analysis; D001921:Brain / Q000187:drug effects*; D001932:Brain Neoplasms / Q000473:pathology / Q000601:surgery*; D003399:Craniotomy / Q000379:methods*; D004232:Diuretics / Q000008:administration & dosage / Q000494:pharmacology*; D004573:Electrolytes / Q000378:metabolism; D005260:Female; D006439:Hemodynamics / Q000187:drug effects; D006801:Humans; D007427:Intracranial Pressure / Q000187:drug effects; D008297:Male; D008353:Mannitol / Q000008:administration & dosage / Q000494:pharmacology*; D008875:Middle Aged; D019635:Neurosurgical Procedures / Q000379:methods*; D009994:Osmolar Concentration; D018401:Sample Size; D015173:Supratentorial Neoplasms / Q000473:pathology / Q000601:surgery*; D016896:Treatment Outcome
D004232:Diuretics; D004573:Electrolytes; D008353:Mannitol