Multiple Actions of Phencyclidine and (+)MK-801 on Isolated Bovine Cerebral Arteries.

This study examines the direct effects of 3 noncompetitive N-methyl-D-aspartate receptor antagonists, phencyclidine (PCP), (+)MK-801, and (-)MK-801, on bovine middle cerebral arteries (BMCA). Rings of BMCA were mounted in isolated tissue chambers equipped with isometric tension transducers to obtain pharmacologic dose-response curves. In the absence of endogenous vasoconstrictors, the 3 N-methyl-D-aspartate antagonists each produced direct constriction of BMCA.

Private sector approaches to workforce enhancement.

Objectives: This paper addresses the private practice model of dental care delivery in the US. The great majority of dental care services are delivered through this model and thus changes in the model represent a means to substantially change the supply and availability of dental services. The two main forces that change how private practices function are broad economic factors, which alter the demand for dental care and innovations in practice structure and function which alter the supply and cost of services.

N-methyl-D-aspartate (NMDA) antagonists--S(+)-ketamine, dextrorphan, and dextromethorphan--act as calcium antagonists on bovine cerebral arteries.

Ketamine, an intravenous anesthetic and a major drug of abuse, is a noncompetitive N-methyl-D-aspartate (NMDA) receptor antagonist. Ketamine's enantiomer, S(+)-ketamine, acts stereoselectively on neuronal NMDA receptors. The purpose of this in vitro study was to compare the direct effects of S(+)-ketamine, 2 other noncompetitive NMDA receptor antagonists (dextrorphan and dextromethorphan), and the calcium entry blocker nimodipine on the cerebral vasculature, using bovine middle cerebral arteries as an experimental model.

A surprising twist: an unusual failure of a keyed filling device specific for a volatile inhaled anesthetic.

We describe two cases in which keyed filling devices for sevoflurane were inadvertently screwed onto isoflurane bottles. The mishaps were possible because the collars on sevoflurane and isoflurane bottles are mirror images of each other. The particular keyed filling device was designed with a flexible outer sleeve and could be screwed onto the wrong bottle while slightly gouging its soft plastic collar.

The use of somatosensory evoked potentials to determine the relationship between patient positioning and impending upper extremity nerve injury during spine surgery: a retrospective analysis.

Somatosensory evoked potential (SSEP) monitoring is used to prevent nerve damage in spine surgery and to detect changes in upper extremity nerve function. Upper extremity SSEP conduction changes may indicate impending nerve injury. We investigated the effect of operative positioning on upper extremity nerve function retrospectively in 1000 consecutive spine surgeries that used SSEP monitoring.

A novel dehydroepiandrosterone analog improves functional recovery in a rat traumatic brain injury model.

The purpose of this study was to investigate the efficacy of a novel steroid, fluasterone (DHEF, a dehydroepiandrosterone (DHEA) analog), at improving functional recovery in a rat model of traumatic brain injury (TBI). The lateral cortical impact model was utilized in two studies of efficacy and therapeutic window. DHEF was given (25 mg/kg, intraperitoneally) at the initial time point and once a day for 2 more days.

Effects of stretch or distention on phenylephrine-induced constriction of human coronary artery bypass grafts.

Objective: To determine the effects of grafting saphenous veins into the arterial circulation and to compare the responsiveness of saphenous veins and mammary arteries to vasoconstrictors (phenylephrine or potassium) and a vasodilator (the calcium antagonist isradipine).

Design: Prospective, controlled, in vitro study.

Setting: Laboratory facility in a university teaching hospital.

Vascular effects of etomidate administered for electroencephalographic burst suppression in humans.

Although its status as a neuroprotectant is controversial, etomidate is often employed for pharmacologic cerebral protection in aneurysm surgery. One purported advantage of etomidate over thiopental is its hemodynamic stability. This study examined the cardiovascular effects of etomidate given for electroencephalographic (EEG) burst suppression during cerebral aneurysm clipping in humans and the direct effects of etomidate on arteries in vitro.

Direct effects of triiodothyronine on human internal mammary artery and saphenous veins.

Objective: Thyroid hormone (3,5,3'-triiodo-L-thyronine is under investigation as a positive inotrope and vasodilator for patients undergoing cardiac surgery. This study determined the direct effects of triiodothyronine on human blood vessels.

Design: Prospective, controlled, in vitro study.

Intravenous vitamin K1 prior to orthotopic heart transplantation: effects in vivo and in vitro.

Background: Vitamin K1 is used to reverse warfarin's anticoagulant action. It is unclear whether intravenous vitamin K1 is safe or efficacious prior to urgent cardiac surgery.

Methods: We retrospectively and prospectively examined the effects of preoperative intravenous vitamin K1 in vivo (administered for warfarin reversal immediately before heart transplantation) on intraoperative blood product utilization, hemodynamics and coagulation parameters.

Porcine gastroepiploic artery as an in vitro experimental model to study vasodilators in microsurgery.

Arterial vasospasm is a common problem in microsurgery. This pharmacological study compares seven vasodilators-lidocaine, papaverine, nicardipine, verapamil, diltiazem, sodium nitroprusside, and hydralazine-for their efficacy and potency in an experimental model of vasospasm. Porcine gastroepiploic arteries were cut into rings to measure isometric tension development in vitro.

The effects of N-methyl-D-aspartate agonists and antagonists on isolated bovine cerebral arteries.

This pharmacologic study examines the direct cerebrovascular effects of N-methyl-D-aspartate (NMDA) receptor agonists and antagonists to determine whether large cerebral arteries have NMDA receptors. Bovine middle cerebral arteries were cut into rings to measure isometric tension development in vitro. Two competitive agonists, L-glutamate and NMDA, each had negligible effects on ring tension in the absence of exogenous vasoconstrictors.

Methylmethacrylate monomer produces direct relaxation of vascular smooth muscle in vitro.

Methylmethacrylate bone cement is associated with severe hypotensive reactions during surgery and anesthesia. The purpose of this in vitro study was to determine if methylmethacrylate monomer could produce hypotension by acting directly on vascular smooth muscle. Segments of human saphenous vein or rabbit thoracic aorta were cut into rings.

Ketamine directly dilates bovine cerebral arteries by acting as a calcium entry blocker.

This in vitro study was performed to determine the role of calcium in ketamine-induced cerebral vasodilation. Isolated bovine middle cerebral arteries were cut into rings to measure isometric tension development or into strips to measure radioactive 45Calcium (45Ca) uptake. Ketamine produced direct relaxation of arterial rings; the relaxation was attenuated in Ca(2+)-deficient media.

Effects of prostaglandin F2 alpha and thromboxane A2 analogue on bovine cerebral arterial tone and calcium fluxes.

We determined sources of activator calcium for prostanoid-induced cerebrovascular constriction by measuring isometric tension and calcium-45 (45Ca) fluxes in bovine middle cerebral arteries. Constriction induced by prostaglandin F2 alpha or the stable thromboxane A2 analogue SQ-26,655 was near-maximally inhibited in calcium-deficient solutions but only partially inhibited by calcium antagonists (10(-5) M verapamil or 3.3 x 10(-7) M nifedipine).

Resource based relative value scale: a new challenge and opportunity for health care cost management.

Beginning in 1992, the use of resource based relative value scale (RBRVS) will greatly change the way physicians are reimbursed for services to Medicare patients. This new system will also have implications for trust funds and corporate providers of health care benefits.

Effects of calcium antagonists on isolated bovine cerebral arteries: inhibition of constriction and calcium-45 uptake induced by potassium or serotonin.

The purpose of this study was to determine the mechanisms by which organic calcium channel blockers inhibit cerebral vasoconstriction. Isolated bovine middle cerebral arteries were cut into rings to measure contractility or into strips to measure radioactive calcium (45Ca) influx and efflux. Calcium channel blockers (10(-5) M verapamil or 3.

Comparative actions of pentobarbital and verapamil on canine cerebral and peripheral arteries in vitro.

Verapamil and pentobarbital were compared for their actions on isolated canine cerebral (basilar and middle cerebral) and peripheral (mesenteric) arteries of similar diameter. The two agents shared several nonselective actions on canine arteries, but differed widely in potency. Both agents produced direct relaxation of cerebral, but not peripheral, arteries, and both agents inhibited constriction of cerebral and peripheral arteries by KCl and CaCl2 (in K+-depolarizing, Ca2+-deficient media).