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Biomedical subjects

C D Blitt

Publications and source records attributed to C D Blitt.

At least 19 recordsLinked to original sources

Hepatic dysfunction after isoflurane anesthesia.

Four members of the Anesthetic and Life Support Advisory Committee of the Food and Drug Administration assessed the contribution of isoflurane (Forane) to 45 instances of hepatic dysfunction after isoflurane anesthesia reported to the FDA for 1981-1984. For 29 (64%) of the cases, at least three members concluded that nonanesthetic causes (e.g., hypoxia, sepsis, viral infection) explained the hepatic injury. For 16 cases (36%), two or more members concluded that isoflurane might be one of several possible causes of the hepatic injury. In the latter cases, patients tended to be younger, had undergone anesthesia of shorter duration for operations outside the chest and abdomen, had developed symptoms later, had higher plasma transaminase values but lower bilirubin values, and had a lower incidence of eosinophilia, anemia, transfusions, and congestive heart failure. The committee concluded that current evidence does not indicate a reasonable likelihood of an association between the use of isoflurane and the occurrence of postoperative hepatic dysfunction.

Adolescent

Evaluation of peripheral nerve stimulators and relationship to possible errors in assessing neuromuscular blockade.

Voltage and current output characteristics were measured on six commercially available peripheral nerve stimulator devices. The results are evaluated as possible sources of variability in peripheral nerve stimulator function and neuromuscular blockade assessment. The authors found significant differences in output voltage waveform and in maximum current into a 470 ohm load (21.4 to 128 mA.). Output current decreased from 25 to 88% in the different devices, with a load impedance increase from 470 to 10,000 ohms. Due to the variability in peripheral nerve stimulation units and the decrease in current output at higher load impedance, less than supramaximal stimulation is possible with erroneous interpretation of neuromuscular blockade.

Electric Stimulation

Clinical pharmacology of lorazepam.

As a preanesthetic medication, lorazepam is available for oral, intravenous, or intramuscular administration. A parenteral dose of 0.04 to 0.06 mg per kg has been shown to be most effective as a preanesthetic medication in terms of antianxiety and antirecall effect (Table 1). Lorazepam has as its predominant advantage over other benzodiazepines the ability to produce anterograde amnesia reliably and for a relatively long duration. From an anesthesia standpoint, the drug finds its major usage as a premedicant or adjuvant (administered in the peri-induction period) to minimize the possibility of recall of unpleasant events during anesthesia and surgery. This is especially germane in patients who are unable to tolerate a sufficient depth of anesthesia to provide this amnesic effect on the basis of anesthetic agent alone. Quite often these patients are critically ill, and from a physiologic standpoint, their cardiovascular systems are unable to tolerate or adapt to moderate to deep anesthetic concentrations of the inhalation anesthetic agents. Even though the metabolic products of lorazepam are not active, the duration of action of this drug dictates that it not be used in the outpatient setting. Indeed, the drug probably should not be used in patients whose expected hospital stay is less than 72 hours. It appears that thrombosis or phlebitis after intravenous injection of lorazepam is less than with diazepam, especially if the drug is injected in small hand or arm veins. Most side effects of lorazepam are associated with central nervous system depression, are dose-related, and fairly predictable. Adverse central nervous system effects may be reversed by administration of physostigmine, but it is worthwhile to note that the duration of action of physostigmine, and repeated administration of physostigmine may be necessary. Lorazepam appears to be acceptable to both physicians and patients. There do not appear to be any obvious adverse interactions between lorazepam and other medications commonly used in anesthesia practice. Nevertheless, it appears that the major value of lorazepam to the anesthesiologist's armamentarium is its ability to prevent recall in appropriate situations.

Adjuvants, Anesthesia

Atrioventricular conduction in dogs during anesthesia with isoflurane.

The effects of 1.25, 2.0, and 2.5 MAC isoflurane on atrioventricular conduction were studied by His-bindle electrocardiography during atrial pacing in ten dogs. No effect upon atrioventricular conduction as evidenced by changes in A--H interval (the time of conduction from low right atrium to His-bundle, representing primary AV nodal conduction) was found at these concentrations. Atrial pacing to 200 beats/min did not influence the A--H interval at the three anesthetic concentrations. The stability of cardiac rhythm observed clinically with isoflurane may be related to this lack of effect upon the AV node.

Anesthetics

Relative importance of alpha and beta adrenergic receptors during resuscitation.

Successful resuscitation from cardiac arrest in the asphyxiated dog model has been ascribed to the use of artificial ventilation, closed chest cardiac massage, and administration of a vasopressor. Controversy remains over whether the most commonly employed vasopressor, epinephrine, exerts its effects primarily by elevating diastolic pressure and reestablishing coronary flow, or by exciting cardiac pacemaker cells and enhancing myocardial contractility. To observe pure alpha and beta adrenergic receptor influences during resuscitation, three groups (alpha-blocked, beta-blocked, unblocked) of dogs were studied. beta-blocked dogs resuscitated with phenylephrine and unblocked dogs resuscitated with epinephrine experienced 100% successful resumption of spontaneous circulation after 5 min of asphyxia-induced arrest. Only 27% of alpha-blocked animals resuscitated with isoproterenol were successfully revived. The appearance of the ECG during cardiac arrest and resuscitation could in no way be used to predict the outcome of resuscitation attempts. Results suggest that, initially, alpha receptor stimulation with concomitant diastolic pressure elevation is more important to the success of resuscitation than beta receptor stimulation.

Animals

Pancuronium bromide enhances atrioventricular conduction in halothane-anesthetized dogs.

The effect of pancuronium bromide on atrioventricular conduction was studied by His-bundle electrocardiography during atrial pacing at different heart rates in halothane-anesthetized dogs. Pancuronium bromide, 0.1 mg/kg, uniformly enhanced atrioventricular conduction, as evidenced by decreased A-H interval (the time from the onset of the first high-frequency component of atrial depolarization to His deflection). Wenckebach second-degree atrioventricular block appeared in five of 14 animals during atrial pacing with halothane anesthesia. This block was uniformly abolished by pancuronium. The enhancement of atrioventricular conduction may contribute to the development of tachyarrhythmias following administration of pancuronium in certain patients, particularly those who have atrial fibrillation or atrial flutter.

Anesthesia, Inhalation