Mannitol treatment in experimental haemophilus influenzae type B meningitis

A study was undertaken to evaluate hypertonic mannitol treatment in experimental lapin Haemophilus influenzae type b meningitis and to compare these results with those in normal rabbits. Increased intracranial pressure, brain water content, and concentrations of lactate and hypoxanthine in cerebrospinal fluid (CSF) were measured as a reflection of altered cerebral perfusion and hypoxia and potential brain injury associated with meningitis. A single dose of mannitol reduced transiently the CSF pressure of uninfected rabbits from 2.15 ± 0.20 to 1.34 ± 0.10 mm Hg (maximum reduction 34.9 ± 8.4%; p < 0.005). The time to the lowest pressure was 38.7 ±2.7 min after initiation of the infusion and the time to return of CSF pressure to initial values was 76.7 ± 5.6 min. In infected mannitol-treated animals the CSF pressure was reduced from 4.78 ± 0.53 to 2.61 ± 0.55 mm Hg (maximum reduction 42.0 ± 7.7%; p < 0.005). Time to maximum pressure decrease was 44.0 ± 5.6 min. CSF pressure returned to the initial level after 178.5 ± 25.2 min. Four h after initiation of mannitol infusion the mean brain water content in infected mannitol-treated animals was 412 ± 4 g H₂O/100 g dry weight and in infected untreated animals it was 415 ± 3 g H₂O/100 g dry weight (p > 0.05). CSF lactate and hypoxanthine concentrations were significantly increased during the 20 h of meningeal inflammation (p < 0.005). The mean percentage change from baseline values for lactate concentrations at the end of the experiment (24 h) in infected mannitol-treated rabbits was significantly smaller than that in infected untreated animals (p = 0.035). A single dose of mannitol reduced the CSF hypoxanthine concentrations of infected animals, but this reduction was not statistically significant.