Mannitol for resuscitation in acute head injury: effects on cerebral perfusion and osmolality

To review the use of mannitol during initial resuscitation following traumatic brain injury and to determine the effects of mannitol on subsequent management following resuscitation and commencement of neuromonitoring.

A retrospective audit of patients presenting to a tertiary hospital with severe head injury (Glasgow coma score < or = 8). Patients were divided into two groups according to whether they received mannitol during initial resuscitation. Measurements included initial plasma osmolality, cerebral perfusion pressure (CPP), intracranial pressure (ICP) and jugular venous saturation (SjO2).

Forty patients were identified: 19 received mannitol prior to admission to the intensive care unit. Of these, only 2 patients fulfilled acceptable neurological indications for mannitol. The mannitol patients received a mean dose of 237 mL of 20% mannitol (47.4 g) and had significantly higher initial osmolalities than the patients who did not receive mannitol (293 vs 279 mosmol/L, p < 0.05). No significant difference in initial CPP, ICP, or SjO2 was identified. The mannitol patients were further subdivided into two 12-month periods (1994 and 1995). A dose related, significant difference in initial osmolalities was identified (140 vs 344 mL and 284 vs 304 mosmol/L respectively, p < 0.05). The latter group (n = 9) had significantly lower initial CPPs (72 vs 59 mmHg) and higher ICPs (14 vs 18 mmHg). No difference in 6 month Glasgow outcome scores between groups was demonstrated.

The empirical overuse of mannitol is common. Mannitol did not exert any beneficial effect on CPP, ICP or SjO2 in the initial phases of management. Larger doses (i.e. > 20 g) are associated with increased osmolality which may reduce CPP.