D. J. Pavlin

Effects of Combining Propofol and Alfentanil on Ventilation, Analgesia, Sedation and Emesis in Human Volunteers

Background Propofol and alfentanil frequently are administered together for intravenous sedation. This study investigated pharmacokinetic and pharmacodynamic interactions between propofol and alfentanil, at sedative concentrations, with specific regard to effects on ventilation, analgesia, sedation, and nausea. Methods Ten male volunteers underwent steady‐state infusions on 3 separate days consisting of propofol alone, alfentanil alone, or a combination of the two. Target plasma concentrations for propofol were 150, 300, and 600 ng/ml for 1 h at each concentration; for alfentanil it was 40 ng/ml for 3 h. Assessment included serial measurements of (1) ventilatory function (minute ventilation, carbon dioxide production, end‐tidal carbon dioxide, ventilatory response to rebreathing 7% CO2); (2) analgesia (subjective pain report in response to graded finger shock and evoked potential amplitude); (3) sedation (subjective rating, observer scores, and digit symbol substitution test); (4) nausea (visual analog scale, 0–100 mm). Results During combination treatment, propofol plasma concentration was 22% greater than during propofol alone using replicate infusion schemes (P < 0.009). End‐tidal carbon dioxide was unchanged by propofol, and increased equally by alfentanil and alfentanil/propofol combined (Delta end‐tidal carbon dioxide 7.5 and 6.2 mmHg, respectively). Analgesia with propofol/alfentanil combined was greater than with alfentanil alone. (Pain report decreased 50% by PA vs. 28% for alfentanil, P < 0.05). Sedation was greater with propofol/alfentanil combined than with alfentanil or propofol alone (digit symbol substitution test 30 for propofol/alfentanil combined vs. 57 for alfentanil, and 46 for propofol, P < 0.05). Nausea occurred in 50% of subjects during alfentanil, but in none during propofol/alfentanil combination treatment. Conclusions The combination of propofol and alfentanil produced greater sedation and analgesia than that with either drug alone. Propofol offset the emetic effects of alfentanil. Equivalent depression of the carbon dioxide response curve, and elevation of end‐tidal carbon dioxide occurred with propofol/alfentanil combined and alfentanil.

Comparison of desflurane with propofol in outpatients undergoing peripheral orthopedic surgery

This study was undertaken to compare desflurane with propofol anesthesia in outpatients undergoing peripheral orthopedic surgery. Data were combined from two institutions participating in a multicenter study. Ninety-one patients, ASA physical status I or II, were each randomly assigned to one of four groups. After administration of fentanyl (2 micrograms/kg) and d-tubocurarine (3 mg), intravenous propofol was administered to induce anesthesia in groups I and II and desflurane in groups III and IV. Maintenance was provided by desflurane/N2O in groups I and III, propofol/N2O in group II, and desflurane/O2 in group IV. Emergence and recovery variables, psychometric test results, and side effects were recorded by observers unaware of the experimental treatment. Patients in group II experienced less nausea than other groups (P = 0.002) despite this group having required more intraoperative fentanyl supplementation than groups III and IV (P = 0.01). Time to emergence, discharge, and psychometric test results were similar in all groups. Desflurane appears to be comparable with propofol as an outpatient anesthetic, facilitating rapid recovery and discharge home.

Vaso-vagal reactions in an ambulatory surgery center

This prospective study was undertaken to determine the incidence and factors predisposing to vaso-vagal reactions during venous cannulation in an ambulatory surgery population. In 141 ambulatory surgery patients, signs and symptoms of a reaction together with mean arterial pressure and heart rate were recorded at 1-min intervals during and for 6 min after venous cannulation. Overall, 10.6% of patients were symptomatic (95% confidence interval [CI] 6%-17%). The incidence was 16.6% (95% CI 8.4%-24.9%) in patients < or = 40 yr and 33.3% (95% CI 6.7%-60.0%) with a prior fainting history. Young age, duration or number of attempts at venous cannulation, and fainting history were independently associated with increased risk of a reaction (P < 0.03-0.004 by multiple repression analysis). Minimum mean arterial pressure was less in symptomatic patients than in those who were asymptomatic (58 mm Hg +/- 11.3 SD versus 82 mm Hg +/- 14.3 SD, P < 0.0001). We conclude that reactions occur commonly, particularly in the young or in patients with a history of fainting. Reactions are typically associated with significant hypotension that may require treatment.

Perioperative rofecoxib plus local anesthetic field block diminishes pain and recovery time after outpatient inguinal hernia repair.

In this study, we compared pain scores after inguinal herniorrhaphy in patients treated by preincisional local anesthetic field block (PL), or PL combined with perioperative rofecoxib, with controls who received standard care. Seventy-five patients having herniorrhaphy under general anesthesia were randomly assigned to receive a placebo pill preoperatively, and for 5 days postoperatively (CONT); preoperative bupivacaine field block and perioperative placebo (PL); preoperative field block plus rofecoxib, 50 mg preoperatively and for 5 days postoperatively (PLR). Bupivacaine infiltration in the wound at closure, IV fentanyl and acetaminophen/oxycodone were administered postoperatively to all. Discharge time, pain scores (0–10), analgesic use, and satisfaction scores (1–6) were compared using analysis of variance. PLR patients had lower maximum pain scores (worst pain) in the postanesthesia care unit (3.7 versus 5.3, P = 0.02) and at 24 h (5.3 versus 6.8, P = 0.03), were discharged 38 min sooner (P = 0.01), required 28% less oxycodone 0–24 h after discharge (P = 0.04), and reported higher satisfaction scores compared with CONT. Pain in PL was less than CONT for 30 min. There were no differences among the 3 groups after 24 h postoperatively. We conclude that perioperative rofecoxib with PL reduces in-hospital recovery time, decreases pain scores and opioid use, and improves satisfaction scores in the first 24 h after surgery.

Hemodynamic and metabolic effects of aortic unclamping following emergency surgery for traumatic thoracic aortic tear in shunted and unshunted patients

Nine cases of traumatic aortic tear treated during 1986-1987 were reviewed. Two patients had functioning Gott shunts, six patients had simple crossclamp, and one patient had a Gott shunt placed which was nonfunctional. Anesthetic management was similar in all patients. Clamp times ranged in unshunted patients from 25 to 38 minutes, and in shunted patients from 42 to 50 minutes. The crossclamp time of the patient with the nonfunctional shunt was 42 minutes. Declamping was accompanied in unshunted patients by decreases in core temperature of up to 1 degree C and acute decreases in PaO2. Marked respiratory and metabolic acidosis occurred with declamping. Respiratory acidosis resolved within 30 minutes with hyperventilation, but metabolic acidosis persisted despite bicarbonate therapy (mean = 1.2 mEq/kg) up to 6 hours after declamping. Associated elevations in serum potassium resolved as pH returned to baseline. Acid-base and electrolyte abnormalities were less marked in patients who were shunted.

Effects of breathing 80% oxygen on water and albumin accumulation in oleic acid-injured rabbit lungs.

This study was done to determine whether breathing 80% oxygen would enhance edema formation in oleic acid (OA) lung injury. Rabbits breathed air (n = 51) or 80% oxygen (n = 51) for 1 to 7 days after OA lung injury (0.09 ml/kg iv). Control groups breathed 80% oxygen (n = 37) or room air (n = 8) without OA injury. Pulmonary vascular permeability was assessed by measuring 131I-albumin (RISA) concentration in extravascular, extracellular lung water (EVECW) relative to plasma (RISAL/RISAPL). EVECW (ml/g dry lung) was measured by 24Na, and total lung water (TLW) by wet/dry weight (g/g dry lung).Air-breathing control values were 4.53 ± 0.25 (SD) for TLW and 0.40 ± 0.09 for RISAL/RISAPL. In the air-breathing OA group, TLW and RISAL/RISAPL increased to 8.32 ± 0.85 and 0.93 ± 0.16, respectively, 2 h after OA (p < .001) but by 24 h, were equal to air-breathing controls.TLW and RISAL/RISAPL in the oxygen treated OA group did not differ from the air breathing OA group on days 2 through 7 inclusive, suggesting that 80% oxygen had no effect on edema formation in the OA-injured lung. Breathing 80% oxygen alone, without OA injury, significantly (p < .005) increased TLW and RISAL/RISAPL on days 5 and 6. Thus, preexisting lung injury had a protective effect against edema formation from a high fraction of inspired oxygen.