Effects of thiopentone and mannitol on cerebral perfusion pressure and E.E.G. in head injured patients with intracranial hypertension.

The effects on intracranial pressure (ICP), cerebral perfusion pressure (CPP) and EEG monitored by Cerebral Function Monitor (CFM) were compared after bolus administration of mannitol (n = 55) and thiopentone (n = 67) to control intracranial hypertension in 18 severely head injured patients. Mannitol increased CPP in 89% of occasions and thiopentone in only 54% (p < 0.001). Thiopentone caused a mean increase in CPP +0.6 kPa (+5.0 +/- 1.6 mmHg) when the minimum pre-bolus voltage of CFM was above 4 microV and a fall in CPP -0.5 kPa (-4.1 +/- 1.6 mmHg) when cortical electrical activity was already severely depressed (p < 0.0002). When pre-bolus CFM was below 4 microV mannitol was superior to thiopentone. This different effect on CPP was due to a significantly greater fall in mean arterial pressure in the thiopentone sub-group -1.6 versus -0.3 kPa (-12.4 +/- 1.5 mmHg, -2.8 +/- 1.2 mmHg; p < 0.001). Severe and unpredictable hypotension occurred, particularly in the thiopentone low CFM sub-group. This symptomatic therapy seems inadequate but a targeted treatment of intracranial hypertension could be possible only with a more sophisticated monitoring, including continuous data on cerebral blood flow and adequacy to metabolic demand.