Long-term use of the CentriMag® Ventricular Assist System as a right ventricular assist device: a case report.

Right ventricular failure (RVF) following implantation of a left ventricular assist system (LVAS) is associated with high morbidity and mortality.( 1-4 ) Numerous centers have reported short-term use of the CentriMag (®) Ventricular Assist System (CVAS) (Levitronix LLC, Waltham, MA) for treatment of cardiogenic shock, decompensated heart failure and right ventricular failure (RVF) following LVAS implantation.( 5-9 ) The present report reviews the clinical course of a patient requiring long-term right ventricular support utilizing the CVAS, following a HeartMate (®) II LVAS (Thoratec Corp. Pleasanton, CA) implantation. Elevated cytotoxic antibody levels complicated the patient's treatment plan by precluding orthotropic heart transplantation. The CVAS operated for 304 days without mechanical difficulty until replaced with the HeartWare (®) Ventricular Assist System (HeartWare Inc. Miramar, FL).

Amphetamine effects on striatal neurons: implications for models of dopamine function.

Models of dopamine function based on the bidirectional neuromodulation of afferents (40, 95) were tested by determining whether cortical ablation would affect the excitatory and inhibitory effects of amphetamine (AMPH) on striatal neurons in freely moving rats. By minimizing pre-and post-AMPH behavioral differences, behavioral clamping revealed that cortical ablation blocked the capacity of AMPH to produce a net excitation of striatal neurons that had shown AMPH-induced excitations under non-clamping conditions. Cortical ablation did not affect AMPH-induced neuronal inhibitions under behavioral clamping conditions. These results suggest that AMPH, possibly by enhancing dopaminergic neuromodulation, facilities or inhibits the activity of neurons that respectively receive substantial or little cortical input. Thus, the findings support models that assign dopamine the capacity to increase the gain of neuronal information processing. Basic research relevant to these models is reviewed and potential clinical implications are discussed.

Cortical lesions attenuate the opposing effects of amphetamine and haloperidol on neostriatal neurons in freely moving rats.

Neuronal activity was recorded from the neostriatum of freely moving rats at least 1 week following either sham or bilateral ablations of frontal and somatosensory cortex. In both groups of animals, the majority of neurons increased firing rate in close temporal association with spontaneous movement. No group differences emerged either with respect to baseline firing rates or open-field behavior. Following amphetamine administration, however, the excitatory response of motor-related neurons was suppressed in cortical-lesioned rats. A behavioral clamping procedure, which assessed neuronal activity during matched pre- and post-amphetamine behaviors, confirmed these results, suggesting that the amphetamine-induced changes in neuronal activity reflect a direct drug effect independent of behavioral feedback. In animals that received a subsequent injection of 1.0 mg/kg haloperidol, cortical lesions attenuated the ability of this neuroleptic to block both the behavioral and neuronal effects of amphetamine. Collectively, these results support mounting evidence for an important modulatory influence of cortical afferents on the amphetamine-induced excitation of neostriatal neurons and the reversal of this effect by haloperidol.

Bilateral cortical ablations attenuate amphetamine-induced excitations of neostriatal motor-related neurons in freely moving rats.

Single-unit recordings from neostriatal neurons showing movement-related excitations were obtained in freely moving, cortically ablated rats and sham-lesioned controls. D-Amphetamine (AMPH, 1.0 mg/kg s.c.) increased neuronal activity relative to resting baseline firing rates in both groups of animals, but cortical ablation significantly attenuated this effect. A behavioral clamping analysis, which compared neuronal activity during identically rated pre- and post-AMPH behaviors, revealed that: (a) AMPH enhanced movement-related neuronal activity in sham-lesioned controls, but not in cortically ablated rats; and (b) the drug-induced neuronal activation in control rats was not simply secondary to the behavioral activation produced by AMPH. In contrast to its neuronal effects, cortical ablation did not affect ratings of AMPH-induced locomotion, rearing, or head movements, though sniffing scores showed a positive correlation with lesion size. Thus, corticostriatal projections are critically involved in AMPH-induced excitations of neostriatal motor-related neurons.

Predicting oxygenator clinical performance from laboratory in-vitro testing.

Knowledge and predictability of oxygenator performance is vital to safe and effective conduct of cardiopulmonary bypass. The determination of oxygenator performance in the laboratory, however, is carried out under a strict set of conditions established by the Association for the Advancement of Medical Instrumentation (AAMI). This performance data is of limited value in the clinical setting where the perfusionist generally operates outside this set of parameters. This study (1) reports the laboratory performance characteristics of a hollow fiber membrane oxygenator (Sorin Monolyth), (2) uses this data to develop a model to predict performance under a wide range of clinical conditions, (3) compares predicted performance with clinical data collected at two open heart centers, and (4) reviews the complexities of comparing laboratory and clinical performance. An in-vitro "oxygenator-deoxygenator" circuit was utilized to determine O2 and CO2 gas exchange, blood path pressure drop, and heat exchanger efficiency at a variety of blood and gas flows, under standard (AAMI) blood inlet conditions: [table: see text] This laboratory performance data was compared to hospital and computer modeling data. Simple numerical comparison and analysis of variance of regression coefficients over groups indicated that some clinical parameters of performance (oxygen transfer and coefficient of heat exchange) were not predicted with the laboratory data. It is concluded that the laboratory performance data determined under strict controlled conditions may be of limited value in predicting clinical performance unless modeled to allow for variances in operating conditions.

Priming with rocuronium accelerates the onset of neuromuscular blockade.

STUDY OBJECTIVE: To investigate the effects of priming rocuronium on the time course of neuromuscular blockade. DESIGN: Prospective, controlled, randomized clinical study. SETTING: University teaching hospital. PATIENTS: 42 ASA physical status I and II patients undergoing peripheral surgery with general anesthesia. INTERVENTIONS: Following a standardized propofol-fentanyl induction, patients in Group 1 (n = 21) received a priming dose of rocuronium 0.06 mg/kg followed two minutes later by an intubating dose of rocuronium 0.54 mg/kg. Patients in Group 2 (n = 21) received a saline placebo injection followed two minutes later by rocuronium 0.6 mg/kg. Anesthesia was maintained with isoflurane and nitrous oxide 60% in oxygen. MEASUREMENTS AND MAIN RESULTS: Neuromuscular function was assessed at the wrist using mechanomyography with a single-twitch mode of stimulation at a frequency of 1 Hz until tracheal intubation and at 0.1 Hz thereafter. The times from injection of the intubating dose of rocuronium until 95% suppression of the twitch tension (onset time), recovery of twitch tension to 25% of control (clinical duration of action), and the time from 25% to 75% spontaneous recovery of twitch tension (recovery index) were recorded. The trachea was intubated at 95% depression of the twitch tension and the intubating conditions were graded using a 3-point scale. The onset times with priming rocuronium (34 +/- 6 s) were significantly shorter (p < 0.01) than those without priming (59 +/- 14 s). The intubation conditions were similar in the two groups; however, the intubating times with priming were significantly shorter. The clinical duration of action and the recovery index did not differ significantly between the two groups. CONCLUSIONS: Priming rocuronium decreased the onset times and thus, the intubating times without increasing the clinical duration of action or recovery index.

Preoperative assessment and preparation.

The practice of ambulatory surgery is rapidly expanding, not only the type of surgeries performed, but more "at risk" patients are being allowed outpatient procedures. Warner and colleagues [56] recently published the results of a large prospective outcome survey of morbidity and mortality after ambulatory surgery. Of the 38,598 patients studied, 31 patients experienced a major morbidity (1:1455) and 4 died (2 myocardial infarctions and 2 motor vehicle accidents) (Table 7). There were no deaths secondary to medical complications within the first week after ambulatory surgery. Furthermore, the morbid events were equally distributed among the various ASA classification categories (Table 8). Given the overall low morbidity and mortality rates, it is likely that ambulatory surgery will continue to grow in the future. Improved preoperative assessment and preparation will further increase the number of acceptable candidates for ambulatory surgery. Having recognized the special needs of the surgical outpatient, anesthesiologists should modify their practice patterns to meet the psychological and pharmacological requirements of the outpatient undergoing an elective surgical procedure.