Thomas R. Eide

The hemodynamic effects of topical fibrin glue during cardiac operations

The authors have observed hemodynamic changes after the application of fibrin glue to the surface of the heart during cardiac surgery, and wish to report two cases where it produced a hemodynamic response

The effect of sublingual nifedipine on coronary venous graft resistance immediately following cardiopulmonary bypass.

The purpose of this study was to determine the effects of sublingual nifedipine administered immediately after discontinuation of cardiopulmonary bypass on coronary graft resistance and systemic hemodynamics. Twenty patients were prospectively randomized into two groups; one given 10 mg sublingal nifedipine after weaning from bypass, the other given a placebo. Coronary graft blood flow was measured under blinded conditions and graft resistance calculated from measurements obtained with an electromagnetic flow probe applied directly to the graft prior to and 15 minutes after drug administration. Serum nifedipine levels were determined immediately before and 15, 30, and 60 minutes after sublingal administration. All patients receiving nifedipine had therapeutic serum levels. Graft resistance in patients given nifedipine decreased a statistically significant average of 27% and increased slightly, but not statistically significantly so, in patients given sublingual placebos. There were no differences between the two groups in cardiac index or pulmonary capillary wedge pressures. We conclude that the administration of sublingual nifedipine to patients in the immediate postbypass period results in therapeutic serum nifedipine levels and decreases coronary graft resistance without affecting cardiac performance.

Effect of cardiopulmonary bypass on plasma levels of nifedipine

Blood levels of many medications are acutely lowered by cardiopulmonary bypass (CPB). Because nifedipine is often used to provide protection from coronary ischemia, a determination of the effect of CPB on plasma nifedipine levels might help to determine the potential clinical benefit of nifedipine during and after bypass. Four samples of blood were drawn from each of eight patients undergoing cardiac surgery: one before, two during, and one after CPB. Although plasma levels of nifedipine declined during and after bypass (P > 0.05, analysis of variance), the time-course and slope of the decline indicate that this was an effect of normal metabolism of the drug rather than an effect of physiologic changes occurring during CPB. An important additional finding was that the majority of patients had subtherapeutic levels of nifedipine before bypass, suggesting that additional nifedipine given during and after surgery might be of benefit. The effect of the CPB circuit itself was also examined in vitro by mixing nifedipine into a pump prime solution that was then recirculated with 2 U of outdated blood while levels of nifedipine were measured for 3 h. Plasma levels did not change in either a CPB circuit exposed to light or kept in a darkened room.

ISOFLURANE VERSUS SODIUM NITROPRUSSIDE FOR THE CONTROL OF PROXIMAL HYPERTENSION DURING THORACIC AORTIC CROSS CLAMPING

OBJECTIVE This study was designed to compare the effects of isoflurane and nitroprusside on spinal cord ischemia when they are used to control proximal hypertension during thoracic aortic cross-clamping (TACC). DESIGN Prospective, randomized, blinded experimental study. SETTING Laboratory and animal research facility. PARTICIPANTS Adult mongrel dogs. INTERVENTIONS Two groups of eight dogs had TACC for 45 minutes. Proximal aortic, distal aortic, and cerebrospinal pressure was calculated as the distal mean pressure minus the CSF pressure. Group 1 received nitroprusside and group 2 received isoflurane to control proximal hypertension during cross-clamping. The dogs were neurologically evaluated 24 and 48 hours later by an observer blinded as to the study group. Spinal cord segments were obtained for histopathologic examination. MEASUREMENTS AND MAIN RESULTS Distal perfusion pressure and spinal cord perfusion pressure were significantly higher in the isoflurane group (p < .005). At 24 hours, seven of eight dogs in group 1 had severe neurologic injury (ie, paraplegia), with the eight having mild neurologic injury. This is in contrast to group 2, where 6 of 8 dogs had either minimal or no injury, one had mild injury, and one had severe injury. Similar results were observed at 48 hours (p < .005). CONCLUSIONS Isoflurane, when used to control proximal hypertension during TACC, produces a higher spinal cord perfusion pressure and is associated with a lower incidence of neurologic injury than nitroprusside in this canine model.