CEREBRAL HEMODYNAMIC-EFFECTS OF DIHYDROERGOTAMINE IN PATIENTS WITH SEVERE TRAUMATIC BRAIN-LESIONS

Dihydroergotamine (DHE) is used in our recently introduced therapy of post-traumatic brain oedema and is suggested to reduce ICP through red uction in both cerebral blood volume and brain water content. This stu dy aims at increasing our knowledge of the mechanisms behind the ICP r educing effect of DHE by analysing cerebrovascular effects of a bolus dose of DHE in severely head injured patients (GCS<8). Mean hemispheri c cerebral blood flow (CBF) calculated from the clearance of i.v. (133 )Xenon, ICP, and cerebral arterio-venous difference in oxygen content (AVDO(2)); were measured before and after hyperventilation and after a bolus dose of DHE (4 mu g/kg). The patients were divided into two gro ups, one with preserved and one with impaired cerebrovascular CO2-reac tivity to hyperventilation, the latter being predictive of poor outcom e. The haemodynamic effects of DHE were compared to those of hypervent ilation. Regional CBF and brain volume SPECT measurements were perform ed in two patients. DHE increased cerebrovascular resistance (CVR) by about 20% and significantly reduced ICP in both groups of patients, re sulting in unchanged AVDO(2). Hyperventilation with preserved CO2-reac tivity caused a similar decrease in ICP as by DHE but with a much larg er increase in CVR (by 70%) and a substantial increase in AVDO(2). Hyp erventilation with impaired CO2-reactivity reduced ICP but otherwise h ad no significant cerebrovascular effects. The study supports the conc ept that the ICP reducing effect of DHE results more from constriction of the large veins than from arterial vasoconstriction, also implying a relatively smaller risk of ischaemia with DHE than with hyperventil ation.