Lidoflazine, a calcium channel blocker, was administered to dogs following twelve minutes of cerebral ischemia, induced by aortic cross-clamping. The effects of lidoflazine (1 mg/kg i.v.) on cerebral blood flow following ischemia was studied in 15 anesthetized, mechanically ventilated dogs. Cerebral blood flow was measured with the radiolabelled microsphere technique before and 10, 30, 60, 90 and 150 minutes following ischemia. Cerebral blood flow increased in all brain regions following ischemia, but by 60 minutes had decreased to control values. Lidoflazine had no effect on this reperfusion phenomenon, or on the distribution of blood flow within the brain. Regional cerebral blood flow was also not altered by lidoflazine therapy. Our data demonstrate that this dose of lidoflazine has no effect on regional or total cerebral blood flow following 12 minutes of cerebral ischemia in dogs. These data do not support perfusion preservation as a mechanism of amelioration of neurologic injury after ischemia by this calcium channel blocker.

Animals↗

PubMedDate not supplied

Comparison of thermal clearance measurement of regional cerebral blood flow with radiolabelled microspheres.

A thermal clearance technique for measuring cerebral blood flow is described and compared with the radiolabelled microsphere technique. The thermal technique involves measurement of the rewarming curve generated after bolus infusion of 4-5 ml of ice-cold saline into the common carotid artery with a subdural thermistor placed on the parietal cortex. Evaluation of the biexponential decay curves obtained with this technique demonstrated a close correlation with total hemispheric, parietal, and parietal gray blood flow determined by simultaneous microsphere measurement. Despite significant correlations (p less than 0.001), scatter in the data produced a broad 95% confidence interval, thus making interpretation of blood flow with the thermal clearance technique impossible. Furthermore, instrumentation with the thermal probe, which required opening of the dura, blunted the cerebral blood flow response to hypercapnia. We conclude that the major limitations of the thermal clearance technique include: nonhomogeneous clearance function, significant variability, and depression of CO2 reactivity. These limitations must be addressed before this technique can be used reliably in the laboratory.

Animals↗

PubMedDate not supplied

Epidural morphine decreases postoperative hypertension by attenuating sympathetic nervous system hyperactivity.

Twenty-four adults who were undergoing operations on the abdominal aorta were enrolled in a randomized, double-blind, placebo-controlled study in which epidural morphine sulfate (6 mg) was employed to attenuate the sympathoadrenal response to surgery to evaluate the possible contribution of sympathetic nervous system hyperactivity to postoperative hypertension. Patients who received epidural morphine required less parenteral morphine in the 24 hours following surgery, had lower analogue pain scores, and had markedly lower plasma norepinephrine levels when compared with patients in the control group who received an identical volume of saline in the epidural space. Epidural morphine had no effect on plasma epinephrine or arginine vasopressin levels. Fewer patients in the morphine group (4 of 12 vs 9 of 12 patients in the saline group) required treatment for hypertension (mean arterial blood pressure, greater than or equal to 110 mm Hg) in the 24 hours following surgery. In addition, patients in the morphine group had lower blood pressures in the 24 hours following surgery. These data suggest that sympathetic nervous system activity and not adrenal epinephrine or pituitary secretion of arginine vasopressin is responsible for the development of hypertension following aortic surgery. Furthermore, epidural narcotics appear to provide a means of attenuating this response.

Adult↗