Intravenous ondansetron for postsurgical opioid-induced nausea and vomiting. S3A-255 Study Group.

The use of opioids for postoperative analgesia may be limited by side effects such as nausea and vomiting. Because ondansetron, a selective serotonin type 3 (5-hydroxytryptamine [5-HT3]) antagonist, is effective for chemotherapy and general anesthesia-induced nausea and vomiting, we hypothesized that it may also be effective for opioid-induced nausea and vomiting. ASA physical status I-III patients undergoing regional anesthesia were eligible for the study. Those who requested an antiemetic after postsurgical opioid administration were randomized to receive a single dose of ondansetron (0.1 mg, 4 mg, or 16 mg intravenously [I.V.]) or placebo in a double-blind fashion. Emetic episodes, nausea and pain ratings, and adverse events were recorded for 24 h after study drug administration. Patient satisfaction scores were obtained 24 h after study drug infusion. A significantly (P < 0.05) larger proportion of patients treated with ondansetron 4 mg and 16 mg experienced no emetic episodes, received no rescue antiemetic, and completed the study compared with placebo. Nausea scores and patient satisfaction scores in the ondansetron 16-mg group were significantly (P < 0.05) more favorable than in the placebo group. Postsurgical pain scores did not differ among groups. The incidence of adverse events was similarly low across groups. The results of this study support our hypothesis that I.V. ondansetron is effective for postsurgical opioid-induced nausea and vomiting.

Effect of sympathetic nerve block on acute inflammatory pain and hyperalgesia.

BACKGROUND: Sympathetic nerve blocks relieve pain in certain chronic pain states, but the role of the sympathetic pathways in acute pain is unclear. Thus the authors wanted to determine whether a sympathetic block could reduce acute pain and hyperalgesia after a heat injury in healthy volunteers. METHODS: The study was made as a randomized, single blinded investigation, in which the volunteers served as their own controls. A lumbar sympathetic nerve block and a contralateral placebo block were performed in 24 persons by injecting 10 ml bupivacaine (0.5%) and 10 ml saline, respectively. The duration and quality of blocks were evaluated by the sympatogalvanic skin response and skin temperature. Bilateral heat injuries were produced on the medial surfaces of the calves with a 50 x 25 mm thermode (47 degrees C, 7 min) 45 min after the blocks. Pain intensity induced by heat, pain thresholds to thermal and mechanical stimulation, and secondary hyperalgesia were assessed before block, after block, and 1, 2, 4, and 6 h after the heat injuries. RESULTS: Of the 24 volunteers, eight were excluded because of somatic block or incomplete sympathetic block. The study revealed no significant differences between sympathetic block and placebo for pain or mechanical allodynia during injury, or pain thresholds, pain responses to heat, or areas of secondary hyperalgesia after the injury. The comparisons were done for the period when the block was effective. CONCLUSION: Sympathetic nerve block did not change acute inflammatory pain or hyperalgesia after a heat injury in human skin.

Postoperative opioid analgesia: time for a reconsideration?

Postoperative pain relief has improved in recent years with the development of new analgesics, additional routes of administration and the appearance of the hypothesis of preemptive as well as balanced analgesia (Kehlet H; Postoperative pain relief-what is the issue? Br J Anaesth 1994;72:375-8). Many initial improvements simply involved the administration of opioid analgesics in new ways, such as continuous or on demand intravenous (i.v.) or epidural infusion. These methods allow lower total opioid dosages, provide a more stable concentration of opioid at the receptor and correspondingly better analgesic effects, and also fewer unwanted side effects. Although opioids have played a prominent role in postoperative analgesia for centuries and are still often administered as a matter of routine, their frequent minor side effects and the increasing availability of suitable alternatives may limit their future use in some situations. Thus, the recent emphasis on ambulatory surgery and accelerated surgical stay programs, both with a focus on early recovery of organ function and provision of functional analgesia [i.e., pain relief that allows normal function (Kehlet H: Postoperative pain relief-what is the issue? Br J Anaesth 1994;72:375-8)] provide an opportunity for a reappraisal of opioid use in these settings. For this debate, controlled clinical studies on the opioid-sparing effect of different analgesic techniques are mentioned, and preferably studies with multiple dosing of analgesics and/or a reasonably large patient sample size. These data do not allow a proper meta-analysis to be performed because of the large variability in surgical procedures, dosing regimens, assessment criteria, among others.

A comparison of patient-controlled analgesia and continuous lumbar plexus block after anterior cruciate ligament reconstruction.

Anterior cruciate ligament (ACL) reconstruction is often a painful operation. Fifty-eight patients who underwent ACL reconstruction using patellar tendon autograft received either a lumbar plexus block (LPB) or patient-controlled analgesia (PCA) for pain relief during the first 24 h after surgery. The average total dose of narcotic used was dramatically less for the LPB group (10.1 mg) than for the PCA group (91.9 mg). The common narcotic analgesic side effects of nausea, pruritus, sedation, and urinary retention were significantly less in the LPB group. The LPB is a safe and effective alternative analgesia after ACL reconstruction.

Thiopental as an adjunct to hypothermia for EEG suppression in infants prior to circulatory arrest.

Fifteen infants were studied to evaluate the effect of profound hypothermia (16 degrees C to 18 degrees C) and hypothermia plus thiopental on the electroencephalogram (EEG) prior to circulatory arrest. Mean patient age and weight were 5.5 +/- 1.2 months and 4.9 +/- 0.3 kg, respectively. After core cooling on cardiopulmonary bypass (CPB), all patients received thiopental, 8 mg/kg, 5 minutes prior to circulatory arrest. Satisfactory EEG recordings were obtained for 9 patients, and serum thiopental concentration was measured in 12 patients. Hypothermia (mean venous return temperature, 17.8 degrees C +/- 1.6 degrees C) alone was associated with persistent cerebral electrical activity in 8 of 9 patients (89%). The addition of thiopental, 8 mg/kg, produced an isoelectric EEG in 6 of these 8 patients (75%). Mean circulatory arrest duration was 44 +/- 4 minutes. EEG activity resumed after reinstitution of CPB in all patients. Serum thiopental concentration at the end of CPB was negligible. It is concluded that hypothermia alone often may not produce EEG isoelectricity, and that the associated cerebral metabolic activity may be suppressed by adjunctive use of thiopental.

Hemodynamic effects of muscle relaxant drugs during anesthetic induction in patients with mitral or aortic valvular heart disease.

The hemodynamic effects of three nondepolarizing skeletal muscle relaxant drug regimens were compared during the induction of general anesthesia in 64 patients with valvular heart disease using a double-blind protocol. Patients were first stratified according to primary valvular defect (aortic stenosis, aortic regurgitation, mitral stenosis, or mitral regurgitation). Next, patients were randomly allocated to a drug group, either group A (atracurium), group V (vecuronium), or group MP (metocurine plus pancuronium). Data were collected during three periods: awake, postanesthetic induction, and posttracheal intubation. Four cardiovascular variables were designated a priori as primary variables of interest. These were heart rate (HR), mean arterial pressure (MAP), cardiac index (CI), and systemic vascular resistance index (SVRI). Patients with mitral stenosis showed two significant hemodynamic differences among muscle relaxant drug groups: (1) CI increased in group A but decreased in group MP between the awake and postinduction measurements (P = 0.032); and (2) SVRI decreased in group A but increased in group MP between the awake and postintubation periods (P = 0.034). In contrast, patients with aortic stenosis, aortic regurgitation, or mitral regurgitation demonstrated no statistically significant difference in cardiovascular responses among drug groups. Further analysis was performed using the following data: (1) other hemodynamic variables; (2) incidence of deviations from cardiovascular stability; and (3) the frequency of cardiovascular drug use. This examination showed no important differences among the muscle relaxant drug groups. The small but significant hemodynamic changes observed in mitral stenosis patients in drug groups A and MP were not noted with vecuronium.(ABSTRACT TRUNCATED AT 250 WORDS)

The onset and duration of neuromuscular blockade using combinations of atracurium and vecuronium.

The effect of atracurium-vecuronium combinations on the onset and duration of neuromuscular blockade was investigated in 30 adult patients undergoing general anaesthesia for elective surgery. The patients were randomized to receive either atracurium 0.6 mg.kg-1, vecuronium 0.1 mg.kg-1, or quarter-dose, half-dose, or full-dose combinations of the two drugs. Neuromuscular blockade was assessed by measuring the evoked electromyographic response of the abductor digiti minimi to transcutaneous stimulation of the ulnar nerve. It was found that half-dose combinations of atracurium and vecuronium did not produce a shorter onset time, but did result in a longer duration of neuromuscular blockade than full-doses of either drug alone (P less than 0.01). The quarter-dose combinations did not reduce onset time or increase duration. The full-dose combinations produced both a shorter onset time (P less than 0.01) and a longer duration (P less than 0.001). The results indicate that atracurium-vecuronium combinations are supra-additive in terms of the duration of the neuromuscular blockade produced. However, the inability of atracurium-vecuronium combinations to reduce onset time without increasing duration suggests that there is little advantage in combining the two drugs in clinical practice.

Nerve blocks in the critical care environment.

The critical care patient population has much to gain from properly administered neural blockade. Effective analgesia alone may make the difference between a patient who is able to compensate for their acute insult and one who cannot. A good example is the patient with multiple fractured ribs, who, after intercostal nerve blocks, no longer requires intubation and mechanical ventilation. The authors believe that effective analgesia is just the beginning of the beneficial effects of neural blockade, because blockade of the afferent limb of sympathetic and sensory nerves may circumvent the neuroendocrine response to acute injury. There is evidence that the stress response is not beneficial in the hospital setting and in fact may be detrimental. Some of the effects include elevated plasma catecholamines, ADH, cortisol, and blood glucose, which contribute to tachycardia, hypertension, increased myocardial work and oxygen consumption, salt and water retention, and a catabolic state with negative nitrogen balance. Whether these changes result in reduced morbidity and mortality has been the subject of several studies, but more studies are needed. It would seem that critically ill patients with little physiologic reserve might be the best population to study because even a small improvement may improve survival. A small beneficial effect in healthy postoperative patients may not be clinically apparent. Most would agree that neural blockade used intraoperatively results in reduced blood loss and a lower incidence of postoperative thromboembolism. The continuation of these techniques into the postoperative period may reduce morbidity and mortality in high-risk patients. A word of caution is in order. The indiscriminate application of the techniques described in this article to critically ill patients would not be in the patients' best interest. Nerve blocks are only safe in the hands of those physicians specifically trained to perform them. In addition, local anesthetics have a low therapeutic ratio, and their administration requires continual observation. The use of epidural or intrathecal opioids alone or in combination with other agents also has potentially serious side effects, and requires continual patient monitoring. The proper performance and maintenance of these techniques requires a large commitment of time, manpower, equipment, and a multidisciplinary approach to include physicians, nursing, and support staff. Nerve blocks and other sophisticated techniques started in the operating room or critical care unit should not necessarily be discontinued when the patient is transferred to a ward bed because the full benefit of this therapy may not have been fully realized.(ABSTRACT TRUNCATED AT 400 WORDS)

The effect of a standardized premedication on oxygen saturation in the cardiac patient before transfer to the operating room.

The effect of premedication with morphine and scopolamine on arterial hemoglobin oxygen saturation (SaO2) was measured continuously in 26 undisturbed patients in their hospital rooms before coronary artery bypass surgery. Two hours preoperatively each patient received morphine, 0.1 mg/kg, and scopolamine, 0.2 or 0.4 mg. SaO2 was continuously recorded using pulse oximetry from one-half hour before premedication until 1 1/2 hours after premedication. The lowest SaO2 measured both the evening before surgery and one-half hour before premedication was 95% +/- 0.5% (mean +/- SEM). After administration of premedication, the lowest SaO2 for the patient population decreased to 93% +/- 0.4% (P less than 0.001 compared with that before premedication), and occurred 52 +/- 2 minutes after premedication was given. Two patients (8%) had an SaO2 less than 90% (lowest SaO2 for both was 88%). It is concluded that the dose of morphine/scopolamine premedication used was associated with a low risk of clinically important hypoxemia in the patient population studied.