Effect of intracarotid and intraventricular morphine on regional cerebral blood flow and metabolism in pentobarbital-anesthetized dogs.

Potent opiate analgesics, administered either epidurally, intrathecally, or intravenously, are a common adjunct to pain control in the perioperative period. Little is known, however, of the effects of opiate agonists on cerebral blood flow (CBF) and metabolism. Current studies are complicated by the hypotensive effects of these compounds and their route of administration. To circumvent these difficulties we studied the effects of intraventricular and intracarotid morphine sulfate, in doses that do not affect arterial blood pressure, on regional CBF and total cerebral oxygen consumption (CMRO2) in pentobarbital-anesthetized dogs. Five dogs received 0.04 mg/kg morphine via intracarotid injection. Five additional dogs received 0.2 mg/kg morphine via ventricular cisternal infusion over 5 min, and five control dogs received mock cerebrospinal fluid at the same infusion rate. CBF was measured using the radiolabeled microsphere technique. Intracarotid morphine decreased neurohypophyseal blood flow to 58% of control, but it did not alter blood flow to any other brain region, except caudate nucleus, or cause a change in CMRO2. Infusion of mock cerebrospinal fluid in the cerebral ventricles did not alter CBF or CMRO2. Ventricular-cisternal perfusion of morphine caused a transient increase in CBF (24 +/- 2 to 37 +/- 6 mL min-1 100 kg-1) but had no effect on spinal cord blood flow or CMRO2. Neurohypophyseal blood flow, however, decreased to 40% of control levels (480 +/- 76 to 176 +/- 42 mL min-1 100 kg-1) after 2 min and gradually returned to control levels at 60 min.(ABSTRACT TRUNCATED AT 250 WORDS)