Thomas W. Cutter

Assessing the behavioral effects and abuse potential of propofol bolus injections in healthy volunteers

Propofol is a recently introduced intravenous anesthetic agent, commonly administered to surgical patients because it induces anesthesia smoothly (i.e., provides loss of consciousness rapidly and usually with no complications) and is associated with rapid recovery. Propofol has psychoactive effects that could be construed as pleasant, although little abuse liability testing has been done on this agent in humans. Accordingly, we examined various effects of this agent at different subanesthetic doses (0.2-0.6 mg/kg) in order to characterize this drugs abuse potential (for recreational use or potential for diversion). Using a double-blind, randomized, crossover design, healthy normal volunteers (N = 10) were injected intravenously with the drug or with placebo. Before the injection and for up to 1 h afterwards, mood (including drug liking), memory and psychomotor performance were assessed. Propofol impaired memory and psychomotor performance and produced changes in 10 of 20 VAS mood ratings. Although there was variability in self-reported drug liking, some subjects clearly liked the effects of propofol, especially at the two higher doses. At the debriefing interview held after completion of the study, five subjects said if they had to participate in one more session in which they were given a choice between being injected with the highest dose (0.6 mg/kg) or a placebo, they would choose propofol. These preliminary results suggest that this agent may have some potential for abuse/diversion and perhaps stricter accountability procedures should be established for this drug in settings where general anesthesia or conscious sedation procedures are done.

Supraglottic Airway Devices in the Ambulatory Setting

Supraglottic airway devices (SGAs) offer certain advantages over endotracheal intubation, making them particularly well suited for the specific demands of outpatient anesthesia. Patients may tolerate the placement and maintenance of an SGA at a lower dose of anesthetic than that needed for an endotracheal tube; neuromuscular blocking agents are rarely necessary for airway management with an SGA; the incidence of airway morbidity is lower with SGAs than with endotracheal tubes; and SGAs may facilitate faster recovery and earlier discharge of patients. Two limitations of SGAs are incomplete protection against aspiration of gastric contents and inadequate delivery of positive pressure ventilation. Newer variants of the original laryngeal mask airway, the LMA Classic (LMA North America, Inc), as well as an array of other recently developed SGAs, aim to address these limitations. Their utility and safety in specific patient populations (eg, the morbidly obese) and during certain procedures (eg, laparoscopic surgery) remain to be determined.

Subjective, behavioral and physiological responses to intravenous meperidine in healthy volunteers

Meperidine is a mu opiate agonist that is frequently used to treat pain. We examined in healthy volunteers (N=10) the effects of intravenous meperidine (0, 0.25, 0.5, and 1.0 mg/kg) on mood and psychomotor performance. A randomized, placebo-controlled, crossover design was used in which subjects were injected with meperidine or saline in a double-blind fashion. Subjects completed several subjective effects questionnaires commonly used in abuse liability testing studies before drug injection and at periodic intervals for up to 5 h after drug injection. Subjects also completed several psychomotor tests. Meperidine produced a constellation of subjective effects in a dose-related fashion, including increases in ratings of “sedated,” “coasting or spaced out” and “feel drug effect” ratings. Many of the drugs subjective effects persisted up to 4 or 5 h after administration of the 1.0 mg/kg dose. Drug liking ratings assessed on a visual analog scale were increased after meperidine injection in about half of the subjects (P=0.09). Eye-hand coordination was affected slightly by meperidine but other indices of psychomotor functioning were unaffected. Miosis increased in a dose-related fashion. Other physiological parameters, such as vital signs, were not affected by meperidine. We conclude that meperidine in healthy volunteers has robust and long-lasting effects on mood, but may have weaker effects on psychomotor performance.

Cardiac arrest after labetalol and metoclopramide administration in a patient with scleroderma.

IMPLICATIONS Although recent Food and Drug Administration warnings have noted proarrhythmic effects of droperidol, other antiemetic drugs may have similar effects. We report a case of cardiac arrest after uncomplicated regional anesthesia in a patient with scleroderma who received labetalol and metoclopramide after surgery. Metoclopramide should be used with caution when risk factors for dysrhythmia are present.

Patient selection in outpatient surgery.

Ambulatory surgery is commonplace for a multitude of procedures and a wide range of patients. The types of procedures performed in the ambulatory setting are becoming more work-intensive, and patients with comorbidities make for a challenging environment. For a safe environment for surgery in ambulatory facilities, the complex task of patient selection is necessary. Until an algorithm is created that includes provider, procedure, facility, and patient comorbidites, clinicians must rely on general guidelines rather than precise recommendations.

Hypothermia and hyperthermia in the ambulatory surgical patient.

Homeotherms, including humans, are able to maintain a relatively constant temperature despite variations in their thermal environment. We normally maintain a narrow thermoregulatory threshold range of approximately 0.2°C, and little change in core temperature is required to trigger compensatory mechanisms to either cool or warm our core temperature back to normothermia. This article focuses on the mechanisms and consequences of hypothermia and hyperthermia in the surgical patient and reviews techniques to prevent and treat these conditions.

Three-in-one nerve block with different concentrations of bupivacaine in total knee arthroplasty: randomized, placebo-controlled, double-blind trial.

Pain after total knee arthroplasty may be severe and lead to adverse outcomes. Using 2 concentrations of bupivacaine, we investigated 3-in-1 nerve blocks effect on pain control, narcotic use, sedation, and patient satisfaction. One hundred five patients undergoing unilateral total knee arthroplasty were randomized into 3 groups: low-dose or high-dose bupivacaine or placebo. Ninety-nine patients completed the study. Three-in-1 nerve block reduced patient-controlled opioid analgesia usage and improved pain relief in the early postoperative period but had little effect beyond postoperative day 1. There were no significant differences among groups with respect to nausea or sedation. Patients in each group exhibited high overall satisfaction. Low-dose bupivacaine was superior to high-dose bupivacaine for pain relief, narcotic consumption, and patient satisfaction in the early postoperative period.

What is the role of neuromuscular blocking drugs in ambulatory anesthesia

Purpose of review During ambulatory anesthesia, muscle relaxants should be used judiciously because of their impact on operating room efficiency and the potential for morbidity and mortality. Recent findings Short-acting and low doses of medium-acting muscle relaxants are appropriate for the typically short period of anesthesia required in ambulatory settings, but they are not necessarily indicated. Their adverse effects range from annoying to lethal. Even when the effects are relatively benign, delays may reduce efficiency. Direct laryngoscopy and endotracheal intubation can often safely be accomplished with opioids and propofol, or with topical anesthesia. Procedures such as laparoscopic cholecystectomies can safely be performed with anesthesia via a laryngeal mask airway; with other procedures, a regional technique or monitored anesthesia care is satisfactory. New agents may improve upon currently available muscle relaxants in terms of rapid onset, short duration, and minimal adverse effects. Summary Anesthetic and surgical needs should dictate the use of muscle relaxants, and alternatives to their use should be considered.

Radiologists and Anesthesiologists

This article discusses the anesthesiologists role in diagnostic and therapeutic radiologic procedures. It addresses the use of monitored anesthesia care, regional anesthesia, and general anesthesia, with an emphasis on patient safety. The discussion is based on guidelines published by the American Society of Anesthesiologists and the American College of Radiology.

An Anesthesiologist’s View of Tumor Ablation in the Radiology Suite

The advent of radiology image-guided tumor ablation procedures has opened up a new era in minimally invasive procedures. Using CT, MRI, ultrasound, and other modalities, radiologists and surgeons can now ablate a tumor through percutaneous entry sites. What traditionally was done in an operating room via large open incisions, with multiple days in the hospital recovering, is now becoming an outpatient procedure via these new techniques. Anesthesiologists play a critical role in optimizing outcome in these patients. Knowledge by anesthesiologists of procedural goals, technology used, and inherit safety concerns of anesthetizing patients in the radiology suite are all critical to patients and proceduralists.