Which is most pungent: isoflurane, sevoflurane or desflurane?

We compared the pungency and tolerability of three inhaled anaesthetics in a randomized, double-blind study. Eighty-one unpremedicated patients (n = 27, each group) inhaled 2 MAC of isoflurane (2.3%), desflurane (12%) or sevoflurane (4%) for 60 s from an anaesthetic breathing circuit via a mask. Two blinded observers recorded coughing, complaints of burning and irritation, and how long the inhalation was tolerated. One sevoflurane patient coughed, but completed the study period, whereas 11 isoflurane patients and 20 desflurane patients coughed, objected verbally or removed the mask forcefully. All sevoflurane, 20 isoflurane and seven desflurane patients completed the study period (average 60, 49 and 33 s, respectively, P < 0.05). The irritability grading was: desflurane > isoflurane > sevoflurane (P < 0.05). Sevoflurane is the least irritating agent for inhalation at 2 MAC concentration.

Remifentanil versus propofol as adjuncts to regional anesthesia. Remifentanil 3010 Study Group.

STUDY OBJECTIVE: To compare the safety and efficacy of remifentanil and propofol as adjuncts to regional anesthesia in patients undergoing orthopedic or urogenital surgery. DESIGN: Prospective, randomized study. SETTING: Multicenter university hospitals. PATIENTS: 107 ASA physical status I, II, and III adult patients who underwent orthopedic or urogenital surgery with axillary, ankle, or spinal block. INTERVENTIONS: Patients were randomized to receive either an infusion of remifentanil 0.2 microg/kg/min or propofol 100 microg/kg/min 5 minutes before nerve block placement. The infusions were decreased by 50% on block completion, increased by 50% for patient discomfort, and decreased by 50% for hypoventilation (< 8 breaths/min) or hemodynamic instability. MEASUREMENTS AND MAIN RESULTS: Pain, discomfort, anxiety, and sedation were assessed by both patient and investigator. Vital signs and adverse events were recorded. Fewer patients in the remifentanil group experienced pain during block placement (6%), and were oversedated (7%) than patients in the propofol group (23% and 26%, respectively; p < 0.05). Hypoventilation during and after block placement (21% and 25%, respectively) and nausea and vomiting during and after block placement (60% and 21%, respectively) were more common in the remifentanil group than in the propofol group (0% and 3%; 17% and 6%, respectively; p < 0.05). The incidence of hypoventilation in remifentanil-treated patients was higher in patients over 65 years of age (p < 0.05), but was transient, resolving within minutes of discontinuing the infusion. CONCLUSIONS: At the doses studied, remifentanil was more effective than propofol in minimizing pain without producing excessive sedation. Remifentanil was associated with more transient respiratory depression and short-term nausea. Our findings indicate that the initial remifentanil rate should be 0.1 microg/kg/min (50% lower than the study's initial rate) and should be further decreased an additional 50% in the elderly to minimize adverse effects.

Remifentanil versus remifentanil/midazolam for ambulatory surgery during monitored anesthesia care.

BACKGROUND: This study was designed to define the appropriate dose of remifentanil hydrochloride alone or combined with midazolam to provide satisfactory comfort and maintain adequate respiration for a monitored anesthesia care setting. METHODS: One hundred fifty-nine patients scheduled for outpatient surgery participated in this multicenter, double-blind study. Patients were randomly assigned to one of two groups: remifentanil, 1 microgram/kg, given over 30 s followed by a continuous infusion of 0.1 microgram.kg-1.min-1 (remifentanil), remifentanil, 0.5 microgram/kg, given over 30 s followed by a continuous infusion of 0.05 microgram.kg-1.min-1 (remifentanil+midazolam). Five minutes after the start of the infusion, patients received a loading dose of saline placebo (remifentanil) or midazolam, 1 mg, (remifentanil+midazolam). If patients were not oversedated, a second dose of placebo or midazolam, 1 mg, was given. Remifentanil was titrated (in increments of 50% from the initial rate) to limit patient discomfort or pain intraoperatively, and the infusion was terminated at the completion of skin closure. RESULTS: At the time of the local anesthetic, most patients in the remifentanil and remifentanil+midazolam groups experienced no pain (66% and 60%, respectively) and no discomfort (66% and 65%, respectively). The final mean (+/-SD) remifentanil infusion rates were 0.12 +/- 0.05 microgram.kg-1.min-1 (remifentanil) and 0.07 +/- 0.03 microgram.kg-1.min-1 (remifentanil+midazolam). Fewer patients in the remifentanil+midazolam group experienced nauses compared with the remifentanil group (16% vs. 36%, respectively; P < 0.05). Four patients (5%) in the remifentanil group and two patients (2%) in the remifentanil+midazolam group experienced brief periods of oxygen desaturation (SpO2 < 90%) and hypoventilation (< 8 breaths/ min). CONCLUSIONS: Remifentanil alone or combined with midazolam provided adequate analgesia and maintained adequate respiration at the doses reported. The low dose of remifentanil combined with 2 mg midazolam, compared with remifentanil alone, resulted in fewer side effects, slightly greater sedation, and less anxiety.

Comparison of propofol with isoflurane for maintenance of anesthesia in patients with chronic obstructive pulmonary disease: use of pulmonary mechanics, peak flow rates, and blood gases.

Patients with chronic obstructive pulmonary disease (COPD) are usually anesthetized with an inhalation agent. After Institutional Review Board approval, informed consent was obtained from 60 patients with moderate to severe COPD according to a preoperative severity scoring system, which took into account history and objective findings. By using objective criteria, such patients were randomly assigned to receive propofol (group I) or isoflurane (group II) as primary maintenance agents. Preoperative and postoperative arterial blood gases, peak expiratory flow rates (PEFR), and chest X-rays were compared. Total dynamic compliance (CDYN) and V1 (% volume exhaled in first second) were measured using Pitot tube sidestream spirometry. A 1,000-mL super-syringe was used to measure total static compliance (CST). Measurements were recorded postintubation, midanesthesia, and pre-extubation. All patients received fentanyl, lidocaine, and propofol, 1.5 to 2.0 mg/kg, for induction. Succinylcholine, 1-1.5 mg/kg, was administered to facilitate intubation. Maintenance was with N2O-O2, vecuronium, and either propofol (n = 30) or isoflurane (n = 30). Both groups showed decreases in postoperative PaO2, SaO2, and PEFR (p < 0.05), but there were no differences between groups (p > 0.05). There were no significant chest X-ray differences. There were no differences between groups with respect to intraoperative pulmonary mechanics (p > 0.05). The only difference between groups was an increase in postoperative PaCO2 in group I and a decrease in group II (p < 0.05). Use of Pitot tube sidestream spirometry is a practical and noninvasive technique for monitoring pulmonary mechanics during anesthesia.(ABSTRACT TRUNCATED AT 250 WORDS)

Minimum alveolar concentration of desflurane in patients older than 65 yr.

BACKGROUND: The minimum alveolar concentration (MAC) of desflurane/oxygen is 7.25% in the 18-30-yr age group, and 6.0% in the 31-65-yr age group. The addition of 60% N2O reduces MAC to 4.0 and 2.83%, respectively. Because MAC of other inhaled anesthetics is less than that for younger adults, we determined MAC of desflurane in adults aged 65 yr and older. METHODS: Thirty-nine patients, 21 of whom received 60% N2O/O2/desflurane, and 18 of whom received desflurane/oxygen, scheduled for surgery, were enrolled. They received no premedication, intravenous induction agent, opioid, or neuromuscular blocking agent for intubation. After 10 min or more at a steady end-tidal desflurane concentration, the incision was made. In both groups, six crossover pairs of patients responses (movement-no movement) provided a mean end-tidal concentration. Minimum alveolar concentration was defined as the average of the six crossover midpoints in each subgroup. RESULTS: MAC was 5.17 +/ 0.6% (mean +/- SD) in the desflurane/oxygen group. It was 1.67 +/- 0.4% in the desflurane/nitrous oxide/oxygen group. CONCLUSIONS: In the geriatric patient, MAC of desflurane, with or without nitrous oxide, is less than that reported in patients aged 18-65 yr. This is in agreement with results with all other inhalation agents.

The esophageal detector device. Does it work?

BACKGROUND: The esophageal detector device (EDD) is a diagnostic tool for confirmation of tracheal intubation. Capnography is the accepted standard for such confirmation. The purpose of this investigation was to determine whether results using the EDD and capnography agree. METHODS: Five hundred patients were divided into three separate studies. In study 1, with 300 consecutive patients, tracheal intubation was performed and tested with the EDD followed by capnography. In study 2, 100 patients had the esophagus intentionally intubated, and confirmation was tested similarly. The tube was then removed and the trachea intubated, and testing followed. Study 3 involved 100 patients and used a double-blind, randomized design. The tube was intentionally inserted into either the esophagus (n = 5) or trachea (n = 49), and testing followed. RESULTS: In study 1, the compressed EDD bulb reinflated 270 times and always agreed with capnography; in 20 of the 270 subjects (7%) bulb reinflation was delayed, taking from 5-30 s. In 30 instances, the bulb remained compressed, and there was no capnogram indicating esophageal intubation. In study 2, regardless of esophageal or tracheal intubation, agreement between EDD and capnogram was 100%. In study 3, the agreement between the two detecting instruments was 100%, but reinflation of the EDD bulb was delayed in 4% of tracheal intubations. In the 500 patients studied, results from the EDD and capnogram always agreed, but in 6% of all tracheal intubations, the EDD bulb inflated slowly. Of 181 esophageal intubations, the results from the EDD and capnogram always agreed, i.e., there was no reinflation or capnogram. The sensitivity, specificity, and predictive value for the EDD in all of these studies was 100%. CONCLUSIONS: The EDD is a valuable diagnostic technique for confirming tracheal intubation. Results using EDD agree with results using capnography; in 6% of instances there is a slow reinflation; and where there is no capnography, such as on hospital wards, EDD may be a useful diagnostic tool.

Desflurane versus isoflurane in patients with chronic hepatic and renal disease.

Forty patients with chronic hepatic (n = 20) and renal (n = 20) disease were studied randomly for the purpose of evaluating safety and laboratory values. These included alanine and aspartate aminotransferases, alkaline phosphatase, total bilirubin, creatinine, and blood urea nitrogen. Patients with hepatic disease received either desflurane (n = 9) or isoflurane (n = 11) and patients with renal disease received the two anesthetics in equal subsets. In the patients with hepatic and renal disease, there were no differences in laboratory values (P < 0.05). We conclude that, in patients with either hepatic or renal disease, laboratory values from pre- to postoperative state did not change significantly within 24 h of anesthesia, and no differences in these changes existed between desflurane or isoflurane.

Which drug prevents tachycardia and hypertension associated with tracheal intubation: lidocaine, fentanyl, or esmolol?

Eighty patients, ASA physical status II-IV, scheduled for noncardiac surgery, were randomly assigned in a double-blind, placebo-controlled manner to receive a preintubation dose of either placebo, 200 mg lidocaine, 200 micrograms fentanyl, or 150 mg esmolol. Induction of anesthesia was accomplished with 4-6 mg/kg thiopental IV followed immediately by the study drug; 1-1.5 mg/kg succinylcholine was given at minute 1. Laryngoscopy and intubation were performed at minute 2 with anesthesia thereafter maintained with 1 MAC (+/- 10%) isoflurane in 60% nitrous oxide in oxygen at a 5 L/min flow for 10 min. Heart rate was recorded every 15 s and blood pressure every minute from induction until 10 min after intubation. Maximum percent increases in heart rate (mean +/- SE) during and after intubation were similar in the placebo (44% +/- 6%), lidocaine (51% +/- 10%), and fentanyl (37% +/- 5%) groups, but lower in the esmolol (18% +/- 5%) group (P less than 0.05). Maximum systolic blood pressure percent increases were lower in the lidocaine (20% +/- 6%), fentanyl (12% +/- 3%), and esmolol (19% +/- 4%) groups than in the placebo (36% +/- 5%) group (P less than 0.05), but not different from each other (P greater than 0.05). Only esmolol provided consistent and reliable protection against increases in both heart rate and systolic blood pressure accompanying laryngoscopy and intubation.

Can esmolol manage surgically-induced tachycardia? Bolus esmolol treatment of intra-operative tachycardia due to surgical stimulation.

A double-blind, randomised study was conducted to examine the efficacy of a single bolus dose of esmolol in treating surgically-induced tachycardia. Anaesthetic technique was identical in all patients, and consisted of premedication with midazolam and glycopyrronium, induction with thiopentone followed by suxamethonium, tracheal intubation, and maintenance with isoflurane 0.6% (end-tidal) and 60% nitrous oxide in oxygen. Forty-eight patients developed a heart rate of greater than 95 beats/minute or 20% more than pre-induction values at an average time of 34 minutes after tracheal intubation and received placebo (15 patients), esmolol 50 mg (16 patients), or esmolol 100 mg (17 patients). Controlled intervention was instituted if heart rate or blood pressure was not adequate. Both 50 and 100 mg of esmolol resulted in lower heart rates compared to placebo (p less than 0.05), with no difference between the two esmolol groups (p greater than 0.05). Patients who received placebo had more episodes of medical intervention than those given esmolol (p less than 0.05). No adverse effects occurred in any patient.

Use of esmolol during anesthesia to treat tachycardia and hypertension.

We evaluated the clinical effectiveness of esmolol, an ultra-short-acting, cardioselective beta-adrenergic receptor blocker, in controlling sinus tachycardia and increased systolic blood pressure occurring perioperatively in 30 ASA physical status II or III patients having elective, non-cardiac surgery. Esmolol 80 mg I.V. bolus (N = 15) or placebo (N = 15) followed by 12 mg/min or placebo were infused in 30 isoflurane-anesthetized patients using a randomized double-blind study design. The bolus plus infusions were given when surgical stimuli caused heart rate to exceed 95 bpm or systolic blood pressure 140 mm Hg. Esmolol significantly decreased heart rate (107 +/- 4, mean +/- SEM to 99 +/- 4, mean +/- SEM bpm) within 45 sec after starting the bolus plus infusion; the placebo had no effect, heart rate being 105 +/- 4 before and 106 +/- 3 bpm after the bolus plus infusion. Patients given esmolol continued to have heart rates significantly lower than patients given placebo injections throughout a six min infusion (Ex., at 5 min 81 +/- 3 vs 91 +/- 4 bpm). The study demonstrated no apparent effect of esmolol on blood pressure but that esmolol is effective in treating perioperative sinus tachycardia.

Comparison of propofol with thiopental and isoflurane for induction and maintenance of general anesthesia.

Propofol, a phenol compound with a short elimination half-life, was compared with thiopental and isoflurane for induction and maintenance of general anesthesia in 60 consenting ASA I, II, and III patients. The study was randomized and open label in design. Hemodynamically, the propofol patients showed a mean +/- SEM decrease in systolic blood pressure in comparison with the thiopental/isoflurane group at 2 (115.1 +/- 4.9 vs. 136.6 +/- 6.0 mmHg), 3 (125.7 +/- 5.1 vs. 149.4 +/- 5.6 mmHg), and 5 min (126.6 +/- 3.8 vs. 144.4 +/- 6.1 mmHg) postinduction and at intubation (135.2 +/- 4.7 vs. 157.8 +/- 6.0 mmHg) (p less than 0.05). The heart rate was lower in the propofol group throughout the induction period (p less than 0.05). Patients who received propofol were ready for discharge from the recovery room sooner (67.9 +/- 4.0 vs. 80.0 +/- 3.6 min) than the thiopental/isoflurane-treated patients (p less than 0.05). Propofol is as safe and effective for induction and maintenance of general anesthesia as thiopental and isoflurane.

A controlled investigation of propofol, thiopentone and methohexitone.

This was a randomized study of 180 ASA physical status I and II patients, 60 in each group who received propofol (PROP), 2.5 mg . kg-1, thiopentone (THIO), 4 mg . kg-1, or methohexitone (METH), 1.5 mg . kg-1. Control values, followed by changes after induction and during a 3-min delay before intubation were recorded for the following parameters: heart rate (HR), systolic and diastolic blood pressures (SBP, DBP), respiratory rate (RR), end-tidal CO2 (PETCO2), and induction time (IT). In addition, the incidence of adverse reactions and time for recovery from anaesthesia were noted. The IT (mean +/- SE) was 35 +/- 1 sec for propofol, 35 +/- 1.2 sec for thiopentone and 34 +/- 1.4 sec for methohexitone. Ninety-three per cent of the PROP group fell asleep with one dose and required no additional doses. Fifty per cent of each of the THIO and METH groups required additional agents (p less than 0.05). METH was associated with the highest elevation in HR, PROP the least (p less than 0.05). PROP was associated with the most decrease in SBP and DBP and in addition respiratory depression (p less than 0.05). The incidence of injection pain or excitatory activity was equal in the three groups with the exception that 14 patients who received METH developed hiccoughs while none did in the other groups. PROP was associated with the most rapid recovery, particularly with respect to the orientation time. We conclude that PROP is an effective alternative to barbiturate induction and that the published recommended doses of THIO and METH are often ineffective.

Heart rate and blood pressure effects of esmolol after ketamine induction and intubation.

Both ketamine and tracheal intubation are associated with increased heart rate (HR) and systolic blood pressure (SBP). Beta blockers prevent or attenuate this increase. Esmolol (E) is a new, intravenous, rapidly metabolized beta blocker. An open-label study was performed in 41 ASA Class II and III patients divided into groups 1-4: control, 100, 200, and 300 micrograms X kg-1 X min-1 (n = 10, 10, 11, and 10, respectively). E was infused over 10 min, the first one-fourth of which was a loading dose of 500 micrograms X kg-1 X min-1; at 4 min, ketamine was followed by succinylcholine, intubation, and enflurane-N2O-O2. HR, SBP, blood E, and plasma catecholamine levels were obtained during the 40 min of study. The control group had a baseline HR of 83 +/- 5 beats/min while esmolol groups 2-4 had an HR of 73 +/- 3, 72 +/- 3, and 68 +/- 4 beats/min, respectively (P less than 0.05). After ketamine, the control group HR increased to 93 +/- 6 beats/min and groups 2-4 remained at the baseline level, 73 +/- 3, 73 +/- 3 and 67 +/- 4 beats/min, respectively (P less than 0.05). Postintubation, the control increased further to 113 +/- 5 beats/min while groups 2-4 were significantly less, 91 +/- 5, 84 +/- 3, and 78 +/- 4 beats/min, respectively. The mean SBP in most E groups was less than the control within groups, but only in group 4 between groups was the SBP less at postintubation (P less than 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

The epidemiology of defibrillation in a medical school complex.

Defibrillation is the definitive treatment for ventricular fibrillation (VF). Participation of physicians, paramedical personnel and lay people in cardiopulmonary resuscitation has significantly increased the survival from ventricular fibrillation. The number of defibrillators has increased and their primary placement within the hospital and community has changed. We studied the location, age, history, characteristics and maintenance of every defibrillator (n = 190) within a three hospital, medical school complex. Most defibrillators had been acquired recently but some dated from 1967. More than 85% were plug-in, non-portable. The government hospital had the lowest ratio of defibrillators to beds, but its maintenance, reliability and records were ths most efficient. We conclude that the increase in the number of defibrillators and its modernization reflects their importance, and that the type of hospital determines the age, type of machine, maintenance, and quantity.