Prostacyclin: a New Treatment for Vasospasm Associated with Subarachnoid Haemorrhage

Summary

One of the major problems associated with the treatment of ruptured intracranial aneurysms is the syndrome of late onset ischaemia. Patients so affected deteriorate neurologically and cerebral angiography often shows narrowing of the intracranial arteries, commonly known as vasospasm.

Many drugs have been used to treat the condition but with little success. A new group of compounds have come into clinical use recently, the Prostaglandins. One member, Prostacyclin (PGI₂ or Epoprostenol) is claimed to be one of the most potent vasodilators known. It was used at Manchester first on an experimental model. An isolated piece of human basilar artery was caused to contract using various agents. Prostacyclin was then used in an attempt to relax the contracted segment of artery. It, suprisingly, caused profound relaxation at very low concentrations of Prostacyclin, yet at higher concentrations it again caused the artery to contract. A literature search suggested this also was seen in the living subject and the crossover occurred at a dosage of 5 ng/kg/min.

A limited pilot trial was therefore devised using Prostacyclin at the low concentration of 1 ng/kg/min and used on six patients. Patients were assessed, in the main, for clinical improvement and change in radiological spasm. Clinically, the results exceeded our expectations in that all patients improved, some back to normal. Radiologically, the vasospasm changed but did not revert completely and also unusual extracranial-intracranial anastomoses appeared in the angiograms. In addition, in one patient, cerebral blood flow showed a more than threefold increase. No generalised cardiovascular collapse occurred and no bleeding tendency was observed.