Effects of dihydroergotamine on cerebral circulation during experimental intracranial hypertension.

Different cerebral vasoconstrictors have recently been suggested for the treatment of raised intracranial pressure (ICP), in patients with severe traumatic brain lesions. Such treatment may be associated with severe side effects. A porcine model simulating an intracranial mass lesion was utilized to examine the haemodynamic cerebral effects of dihydroergotamine (DHE), a recently introduced pharmacological treatment for raised intracranial pressure. Intracranial hypertension was induced by inflation of two tonometric gastric balloons placed extradurally covering the parieto-occipital region bilaterally. The animals were randomized into one group with six animals receiving 1.0 mg of DHE i.v. followed by a continuous infusion of 0.2 mg/h (high dose) and another group of six animals receiving 0.15 mg i.v. followed by 0.03 mg/h (low dose). Measurements of cerebral blood flow (CBF) and arterio-venous difference in oxygen content (CaVO2) were performed by 5, 20 and 60 min after the DHE infusion. Intracranial pressure (ICP), mean arterial blood pressure (MAP) and cerebral electrical activity (EEG) were recorded continuously. In both groups infusion of DHE caused a lasting decrease in ICP probably achieved mainly by a decrease in cerebral blood volume due to constriction of both arterial and venous capacitance vessels. In the group treated with high-dose DHE, but not in that given low-dose DHE, a progressive increase in CaVO2, a fall in jugular venous pH and an increase in EEG delta activity were observed indicating cerebral hypoxia. The study supports the view that DHE may be a valuable tool in the pharmacological treatment of increased ICP in traumatic brain lesions but underscores the importance of a proper dosage.