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.

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.

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.

Acute cardiovascular effects of dimethylsulfoxide.

Dimethylsulfoxide (DMSO) has been advocated as a central nervous system (CNS) protectant against ischemia and trauma. The present study was performed to evaluate acute cardiovascular effects of DMSO which might complicate the clinical treatment of CNS compromised patients. Intravenously administered DMSO in doses which reportedly provide CNS protection, 2 g/kg, were infused in 6 dogs; hemodynamic variables were measured and compared to infusion of equal volumes of 0.9% sodium chloride. Immediately after infusion, DMSO caused increases in cardiac index, heart rate, pulmonary capillary wedge pressures (WP), and pulmonary arterial (systolic, mean, and diastolic) pressures which were significantly greater than changes induced by saline. DMSO decreased systematic diastolic pressure and systemic vascular resistance at the end of infusion. Most DMSO induced changes returned toward pre-infusion values 10 min after the end of infusion. These results suggest transient DMSO effects different from equal volumes of saline, possibly due to hyperosmotic expansion of plasma volume. A decrease in systemic vascular resistances was also observed. Although neither CNS production, intracranial pressure or blood flow were studied, these data suggest that DMSO used for CNS protection would not have adverse acute hemodynamic consequences. This may be particularly relevant in traumatized, hypovolemic patients.

Comparison of bupivacaine, etidocaine, and saline for trigger-point therapy.

Injections of local anesthetics, saline, "dry needling," or other stimuli at specific, tender loci (trigger or acupuncture points) are reportedly efficacious in treatment of chronic pain syndromes. In a randomized, double-blind crossover study, subjective responses of 15 patients with myofascial syndrome to trigger-point injections of either bupivacaine 0.5%, etidocaine 1%, or physiologic saline without preservative were compared. Responses in six pain-related categories were determined before treatment and 15 minutes, 24 hours, and 7 days after treatment. Trigger-point injections with bupivacaine and etidocaine were generally preferred over saline in several pain-tested categories. Implications and possible mechanisms are discussed.

Comparison of dopamine, dobutamine, and epinephrine in CPR.

Two new catecholamines, dopamine and dobutamine, have found widespread use for cardiovascular support. The relative efficacy of these drugs in aiding resuscitation from cardiopulmonary arrest is unknown. Dogs were subjected to either asphyxial or fibrillatory cardiac arrest. Resuscitation was attempted with artificial ventilation, closed chest cardiac massage, and one of four iv drug protocols: dopamine, 40 mg; epinephrine, 1 mg; dobutamine, 50 mg; or no drug. The incidence of successful resuscitation from both asphyxial and fibrillatory arrest was significantly greater in groups receiving dopamine or epinephrine than in groups receiving dobutamine or no drug. There was no difference in success between the dopamine and epinephrine groups. The authors conclude that, in dogs, dopamine is a useful adjunct to CPR because of its alpha-adrenergic stimulating activity at high doses. Dobutamine does not appear to be of value as the initial therapy of cardiac arrest. If the response in man is similar to that in dogs, dopamine may provide an alternative to epinephrine during CPR.