Paul F. White

Sedative Infusions during Local and Regional Anesthesia: A Comparison of Midazolam and Propofol

Abstract Study Objective: To compare the intraoperative effects and recovery characteristics when either midazolam or propofol was used for sedation during local or regional anesthesia. Design: Open-label, randomized study with blinded observer assessing recovery data. Setting: Outpatients undergoing elective surgical procedures under local or regional anesthesia at Stanford University Hospital, Stanford, California. Patients: Sixty-eight consenting, unpremedicated ASA physical status I, II, or III patients. Interventions: After achieving adequate analgesia with local anesthetic solutions, patients were administered a loading dose of either midazolam (4.2 ± 1.4 mg) or propofol (69 ± 23 mg) followed by a variable-rate maintenance infusion equal to 8.6 ± 5.4 mg/h or 265 ± 185 mg/h, respectively, to maintain a stable level of sedation during the operation. Measurements and Main Results: Intraoperative assessments included level of sedation, as well as cardiovascular and respiratory status, at 1- to 5-minute intervals during the operation. Postoperatively, recovery of cognitive and psychomotor function was assessed using analog scales and the digit-symbol substitution test. The overall quality of intraoperative sedation was similar in the two sedative treatment groups. Although midazolam produced less pain on injection and more effective intraoperative amnesia, use of propofol was associated with less postoperative sedation, drowsiness, confusion, clumsiness, and amnesia, as well as more rapid recovery of cognitive function. However, discharge times were similar in the two sedative treatment groups. Conclusions: Propofol infusion is a clinically useful alternative to midazolam for sedation during ambulatory surgery under local or regional anesthesia.

Anesthesia for Laparoscopic Cholecystectomy Is Nitrous Oxide Contraindicated

Since it has been suggested that the use of nitrous oxide (N2O) may contribute to bowel distention, we evaluated the effects of N2O on operating conditions during laparoscopic cholecystectomy in 50 healthy patients using a double-blind protocol design. All patients received the same preanesthetic medication (midazolam, 2 mg intravenously) and induction of anesthesia consisted of intravenously administered fentanyl 1.5 micrograms.kg-1, thiopental 4-6 mg.kg-1, and a nondepolarizing muscle relaxant. For maintenance of anesthesia, patients were randomly assigned to one of two treatment groups: group 1 (n = 26) received isoflurane with 70% N2O in oxygen (O2), whereas group 2 (n = 24) received isoflurane in an air/O2 mixture. The surgeon (blinded to the anesthetic technique) estimated the degree of technical difficulty before beginning the operation using a five-point scale. At 15-min intervals throughout the operation, the surgeon was asked to evaluate both overall operating conditions and degree of bowel distension using independent five-point scales. At the end of the operation, the surgeon was asked whether or not N2O had been used as part of the anesthetic technique. There were no significant intraoperative differences between the two groups with respect to operating conditions or bowel distension. More importantly, there was no time-related change in either variable during the course of the operation. Finally, the incidence of postoperative nausea and vomiting was similar in both treatment groups. The surgeon was able to correctly determine that N2O had been administered only 44% of the time. Thus, N2O had no clinically apparent deleterious effects during laparoscopic cholecystectomy.

Midazolam in combination with propofol for sedation during local anesthesia

STUDY OBJECTIVEnTo compare the sedative, anxiolytic, and amnestic effects, as well as the recovery characteristics, when midazolam (vs. a placebo) is administered to patients receiving a propofol infusion for sedation during local anesthesia.nnnDESIGNnRandomized, double-blind, placebo-controlled study to evaluate the perioperative effects of intravenous (IV) midazolam.nnnSETTINGnOutpatient surgery center of a university-affiliated medical center.nnnPATIENTSnOne hundred thirty-nine consenting, ASA physical status I, II, and III outpatients undergoing elective surgical procedures under local anesthesia.nnnINTERVENTIONSnPatients were randomly assigned to receive either midazolam 2 mg IV or saline 2 ml IV prior to injection of local anesthesia. Intraoperative sedation was maintained using a variable-rate propofol infusion.nnnMEASUREMENTS AND MAIN RESULTSnPreoperative assessment of sedation, anxiety, and amnesia was performed before and after IV midazolam. Intraoperative evaluations included level of sedation, as well as cardiovascular and respiratory measurements, at 1- to 5-minute intervals during the operation. Postoperatively, recovery of psychomotor function and patients subjective feelings were assessed using the visual analog scale and questionnaires. Amnesia was assessed using picture recall during the perioperative period. In the operating room, midazolam 2 mg IV, compared with the placebo, produced a significantly greater increase in patients level of sedation (7 +/- 13 mm to 49 +/- 21 mm for midazolam vs. 8 +/- 11 mm to 19 +/- 21 mm for the placebo; p less than 0.01) and a greater decrease in anxiety level (62 +/- 25 mm to 21 +/- 21 mm for midazolam vs. 54 +/- 27 mm to 53 +/- 22 mm for the placebo; p less than 0.01). Although the propofol dosage requirements to maintain comparable levels of sedation were similar in both groups, midazolam decreased patients recall of intraoperative events (e.g., propofol-induced pain on injection and discomfort with local anesthetic injection) without significantly altering cardiorespiratory parameters or prolonging times to ambulation and discharge from the outpatient facility.nnnCONCLUSIONSnPremedication with midazolam 2 mg IV produced increased sedation, amnesia, and anxiolysis when administered immediately prior to the propofol infusion as part of a sedation technique for outpatient surgery. This combination did not prolong the recovery room stay when compared with propofol alone.

Epidural patient-controlled analgesia (PCA): an alternative to continuous epidural infusions

In a clinical study involving 16 surgical patients receiving epidural hydromorphone for postoperative analgesia, we compared the use of a continuous infusion technique to an intermittent bolus technique (involving the use of a PCA device). Although comparable analgesia was achieved in the 2 treatment groups during the 48 h study period, the hydromorphone usage (mean value +/- S.D.) was significantly higher in the continuous infusion group (10.2 +/- 3.6 mg vs. 4.6 +/- 2.2 mg in the intermittent bolus group). In spite of this difference in the analgesic dosage requirement, the side effect profile was similar for the 2 groups. Further studies are needed to confirm this observation and to determine the implications with respect to postoperative recovery.

Patient and nurse evaluation of paient-controlled analgesia delivery systems for postoperative pian management

Five different patient-controlled analgesia (PCA) delivery systems were evaluated for the treatment of acute postoperative pain in 423 patients undergoing elective operations at a large tertiary care hospital. The PCA trial was conducted on four different postsurgical wards over a 5-mo period. All five devices were utilized on each ward for a 1-mo period. According to the nurses, the mean time (+/- SD) required to become comfortable using the Pharmacia Deltec CADD-PCA was significantly longer (50 +/- 37 min) than that using the Abbott Lifecare Plus (19 +/- 17 min), Bard PCA I (17 +/- 14 min), IVAC PCA (17 +/- 14 min), or Baxter PCA Infusor (7 +/- 8 min). With respect to ease of documentation by the nursing staff, the Baxter device was superior to the Pharmacia device. Similarly, mechanical problems were less frequent with the Baxter (6%) compared with the Pharmacia device (71%). The patients felt that the nurses were more comfortable using the Baxter device than the Pharmacia device. The patients also found the Baxter device easier to use, especially at night, and the least likely to interfere with ambulation. In conclusion, 80% of the nurses at this teaching center preferred the Baxter PCA Infusor over four widely used electronic PCA devices for the management of acute postoperative pain. The Pharmacia device was felt by the nurses to be less user friendly than the other programmable PCA devices used in this trial. Of the electronic devices we studied, the Bard and IVAC devices were the most cost-effective.

Comparative effects of desflurane and isoflurane on vecuronium-induced neuromuscular blockade

STUDY OBJECTIVEnTo evaluate the neuromuscular effects of a nondepolarizing muscle relaxant (vecuronium) during anesthesia with equipotent concentrations of either desflurane or isoflurane.nnnDESIGNnRandomized open study comparing effects of desflurane and isoflurane on vecuronium-induced neuromuscular blockade.nnnSETTINGnUniversity-affiliated medical center.nnnPATIENTSnForty-five healthy adults undergoing elective surgical procedures randomly assigned to receive either desflurane, nitrous oxide (N2O), and vecuronium or isoflurane, N2O, and vecuronium for maintenance of general anesthesia.nnnINTERVENTIONSnFollowing a standardized induction sequence, patients receiving either desflurane and N2O or isoflurane and N2O were administered bolus doses of vecuronium equal to 0.01, 0.02, or 0.03 mg/kg intravenously (IV) during the maintenance period. Neuromuscular transmission was measured using a Relaxograph monitor.nnnMEASUREMENTS AND MAIN RESULTSnVecuronium produced similar depression of neuromuscular function at equipotent (50% of the minimum alveolar concentration) end-tidal concentrations of isoflurane 0.6% and desflurane 3.0%. Following administration of vecuronium 0.01 to 0.03 mg/kg IV, onset times (3.4 +/- 0.4 minutes to 3.2 +/- 0.4 minutes and 3.2 +/- 0.5 minutes to 3.0 +/- 0.6 minutes), maximum T1 twitch depression (80% +/- 10% to 95% +/- 9% and 81% +/- 9% to 97% +/- 10%), clinical duration of blockade (12 +/- 5 minutes to 20 +/- 8 minutes and 10 +/- 5 minutes to 19 +/- 17 minutes), and T1 recovery times (10 +/- 3 minutes to 12 +/- 6 minutes and 10 +/- 3 minutes to 12 +/- 4 minutes) were similar in the isoflurane and desflurane treatment groups, respectively (means +/- SD).nnnCONCLUSIONnVecuronium has similar neuromuscular effects when administered in the presence of desflurane 3% and isoflurane 0.6%.

Intraocular pressure and hemodynamic changes following tracheal intubation in children

STUDY OBJECTIVEnTo determine the optimal time in which to make intraocular pressure (IOP) measurements in children following tracheal intubation.nnnDESIGNnRandomized, controlled trial.nnnSETTINGnOperating rooms of a tertiary-care childrens hospital.nnnPATIENTSnThirteen healthy children undergoing elective strabismus correction surgery under halothane and nitrous oxide (N2O) endotracheal anesthesia.nnnINTERVENTIONSnFollowing induction of anesthesia, patients were randomly assigned to receive stable end-tidal halothane concentrations of 0.5% or 1.0% in 66% N2O.nnnMEASUREMENTS AND MAIN RESULTSnBaseline (preintubation) IOP, heart rate (HR), and mean arterial pressure (MAP) were recorded after 10 minutes of steady-state end-tidal concentrations. These measurements were repeated at 1-minute intervals following tracheal intubation, which was facilitated with atracurium. HR and MAP changes were found to be good predictors of IOP changes. IOP returned to baseline (preintubation) values when HR and MAP returned to preintubation levels. However, IOP measurements under anesthesia may not reflect awake values.nnnCONCLUSIONSnWe recommend that IOP be measured only after HR and MAP have returned to preintubation levels in children who have undergone tracheal intubation during halothane and N2O anesthesia.

Mivacurium as an alternative to succinylcholine during outpatient laparoscopy

STUDY OBJECTIVESnTo compare (1) the adequacy of conditions for tracheal intubation; (2) the onset, depth, clinically effective duration, and recovery profile; and (3) adverse effects associated with mivacurium as an alternative to succinylcholine during general (endotracheal) anesthesia for outpatient laparoscopy.nnnDESIGNnA randomized, controlled clinical trial.nnnSETTINGnBarnes Hospital Outpatient Surgery Center.nnnPATIENTSnSixty healthy consenting ASA physical status I or II adult female outpatients.nnnINTERVENTIONSnFollowing a standardized thiopental sodium-alfentanil induction, patients were randomly assigned to one of three groups: Group I-alfentanil-nitrous oxide (N2O)-succinylcholine; Group II-alfentanil-N2O-mivacurium; Group III-enflurane-N2O-mivacurium.nnnMEASUREMENTS AND MAIN RESULTSnNeuromuscular blockade was measured by electromyography of the stimulated adductor pollicis muscle contraction. Tracheal intubation was attempted after achieving 70% or greater blockade and was graded on a four-point scale. Onset and recovery were more rapid with succinylcholine than with mivacurium. The clinically effective duration of action of mivacurium was not significantly different in the enflurane-N2O group compared with the alfentanil-N2O group. Side effects with mivacurium included flushing and occasional wheezing.nnnCONCLUSIONSnMivacurium 0.15 mg/kg given intravenously provided good to excellent conditions for tracheal intubation in 2 to 3 minutes. This dose provided a clinically effective duration of action of 20 to 25 minutes, and the residual blockade was readily reversible with neostigmine. Mivacurium did not, however, offer any apparent advantage over succinylcholine in this outpatient population.

Acute hemodynamic effects of indigo carmine in the presence of compromised cardiac function

This report describes the acute hemodynamic effects of indigo carmine in a surgical patient with compromised cardiac function. A 68-year-old woman with stable but severe cardiac dysfunction and renal artery stenosis was scheduled for an elective aortorenal bypass procedure. No hemodynamic instability occurred during the operation until the patient was administered intravenous (IV) indigo carmine 5 ml. At that time, the patient experienced an acute increase in afterload, which resulted in acute left ventricular failure documented by a decrease in cardiac output (CO) and an increase in pulmonary artery pressure (PAP). Until further studies defining the mechanism for its hypertensive side effect are performed, indigo carmine should be used with caution in patients with severe cardiac dysfunction.

Anaesthesia for day case surgery

Patient selection is critical for safe and efficient day case surgery. Selection should be based on medical, social and surgical factors. Better communication between surgeon, anaesthetist and general practitioner is essential in achieving appropriate selection. A variety of patient factors affect the incidence of postoperative complications (Table 3). Pre-operative evaluation requires a history and physical examination, with special investigations if clinically indicated. Laboratory tests should only be used to screen selected sub-populations (Table 4). Many patients are anxious prior to surgery. Benzodiazepines combine anxiolysis with sedation and amnesia, and agents with short half-lives (temazepam, midazolam) do not delay recovery or discharge. Temazepam is a useful oral premedicant, and parenteral midazolam has a rapid onset in patients for whom logistical factors (e.g. transportation delays, rescheduling of cases) prevent oral premedication.