Serendipity: Being in the Right Place at the Right Time.

Effect of Nitrous Oxide and of Narcotic Premedication on the Alveolar Concentration Required for Anesthesia. By , Eger EI II. Anesthesiology 1964; 25:302-6. Hyperthermia during Anesthesia. By Saidman LJ, Havard ES, Eger EI II. JAMA 1964; 190:1029-32. The minimum alveolar concentration (MAC) of an inhaled anesthetic preventing movement in response to a surgical incision as a measure of equipotency was "invented" in 1964 at the University of California, San Francisco. The principal advantage of MAC is that it allows the pharmacologic effects of inhaled anesthetics to be compared against each other at a similar anesthetic depth. Thus, if the hemodynamic effect (hypotension, decreased cardiac output) of anesthetic "A" is greater than that of anesthetic "B," the anesthesiologist may elect to use "A" in patients with myocardial dysfunction. A rare side effect of a volatile anesthetic is that in some patients, malignant hyperthermia may occur with or without succinylcholine use. This phenomenon was detected in a patient in whom halothane MAC was being measured. The availability of the Severinghaus blood gas device allowed for the first ever measurement of the metabolic and respiratory acidemia that accompanies malignant hyperthermia.

Caroline B. Palmer: Pioneer Physician Anesthetist and First Chair of Anesthesia at Stanford.

Caroline B. Palmer was appointed as Chief of Anesthesia at Cooper Medical College (soon renamed as Stanford Medical School) in 1909. For the next 28 years, she was an innovative leader, a clinical researcher, and a strong advocate for recognition of anesthesiology as a medical specialty. To honor her accomplishments, the operating room suite in the new Stanford Hospital will be named after this pioneering woman anesthesiologist.

Obesity modestly affects inhaled anesthetic kinetics in humans.

BACKGROUND: Few studies have determined the effect of obesity on inhaled anesthetic pharmacokinetics. We hypothesized that the solubility of potent inhaled anesthetics in fat and increased body mass index (BMI) in obese patients interact to increase anesthetic uptake and decrease the rate at which the delivered (FD) and inspired (FI) concentrations of an inhaled anesthetic approach a constantly maintained alveolar concentration (end-tidal or FA). This hypothesis implies that the effect of obesity would be greater with a more soluble anesthetic such as isoflurane versus desflurane. METHODS: In 107 ASA physical status I-III patients, anesthesia was induced with propofol, tracheal intubation facilitated with neuromuscular blockade, and ventilation controlled with 50% nitrous oxide in oxygen to maintain end-tidal carbon dioxide concentrations between 35 and 45 mm Hg. Isoflurane or desflurane was administered in a 1 L/min inflow rate at FD concentrations sufficient to maintain FA at 0.6 minimum alveolar anesthetic concentration (0.7% or 3.7%, respectively). FD, FI, and FA were measured 5, 10, 20, 40, 60, 90, 120,150, and 180 min after starting potent inhaled anesthetic delivery. RESULTS: Fifty-nine patients received isoflurane and 48 received desflurane. BMI ranged between 18 and 63 kg/m(2) and demographic variables did not differ between anesthetic groups. For isoflurane, FD/FA or FI/FA weakly (but significantly) correlated with BMI at 9/18 time points whereas for desflurane FD/FA or FI/FA correlated significantly with BMI at only one time point (P < 0.01). After dividing each group into nonobese (BMI < 30) and obese (BMI > or = 30) patients, with isoflurane, FD/FA or FI/FA was higher in obese patients at four time points whereas there was no difference between nonobese and obese patients for desflurane. Patients receiving isoflurane took longer to respond to command after discontinuing anesthesia but obesity did not increase or decrease awakening time for either isoflurane or desflurane. When BMI was used to normalize FI/FA and FD/FA the median values for isoflurane consistently exceeded the median value for desflurane by factors ranging from 3 to 5, values comparable to the ratios of their blood/gas (3.1), muscle/gas (4.6), and fat/gas (5.4) partition coefficients. CONCLUSION: BMI modestly affects FD/FA and FI/FA, and this effect is most apparent for an anesthetic having a greater solubility in all tissues. An increased BMI increases anesthetic uptake and, thus, the need for delivered anesthetic to sustain a constant alveolar anesthetic concentration, particularly with a more soluble anesthetic. However, the increase with an increased body mass is small.

Can Modern Infrared Analyzers Replace Gas Chromatography to Measure Anesthetic Vapor Concentrations?

BACKGROUND: Gas chromatography (GC) has often been considered the most accurate method to measure the concentration of inhaled anesthetic vapors. However, infrared (IR) gas analysis has become the clinically preferred monitoring technique because it provides continuous data, is less expensive and more practical, and is readily available. We examined the accuracy of a modern IR analyzer (M-CAiOV compact gas IR analyzer (General Electric, Helsinki, Finland) by comparing its performance with GC. METHODS: To examine linearity, we analyzed 3 different concentrations of 3 different agents in O2: 0.3, 0.7, and 1.2% isoflurane; 0.5, 1, and 2% sevoflurane; and 1, 3, and 6% desflurane. To examine the effect of carrier gas composition, we prepared mixtures of 1% isoflurane, 1 or 2% sevoflurane, or 6% desflurane in 100% O2 (= O2 group); 30%O2+ 70%N2O (= N2O group), 28%O2 + 66%N2O + 5%CO2 (= CO2 group), or air. To examine consistency between analyzers, four different M-CAiOV analyzers were tested. RESULTS: The IR analyzer response in O2 is linear over the concentration range studied: IR isoflurane % = -0.0256 + (1.006 * GC %), R = 0.998; IR sevoflurane % = -0.008 + (0.946 * GC %), R = 0.993; and IR desflurane % = 0.256 + (0.919 * GC %), R = 0.998. The deviation from GC calculated as (100*(IR-GC)/GC), in %) ranged from -11 to 11% for the medium and higher concentrations, and from -20 to +20% for the lowest concentrations. No carrier gas effect could be detected. Individual modules differed in their accuracy (p = 0.004), with differences between analyzers mounting up to 12% of the medium and highest concentrations and up to 25% of the lowest agent concentrations. CONCLUSION: M-CAiOV compact gas IR analyzers are well compensated for carrier gas cross-sensitivity and are linear over the range of concentrations studied. IR and GC cannot be used interchangeably, because the deviations between GC and IR mount up to ± 20%, and because individual analyzers differ unpredictably in their performance.

Illustrations of inhaled anesthetic uptake, including intertissue diffusion to and from fat.

Although several mathematical and computer simulations of inhaled anesthetic pharmacokinetics have been devised, their complexity sometimes limits an intuitive appreciation of the interactions produced by the determinants of kinetics. In this essay, we illustrate the factors that govern inhaled anesthetic pharmacokinetics with drawings that consider delivery of anesthetic by ventilation to the lungs and dispersion of the anesthetic to tissue depots by the circulation. The illustrations incorporate the effects of both blood flow and blood solubility as determinants of the extent of dispersion. They incorporate tissue volume and solubility as determinants of the capacity of the tissue depots. Capacity to hold (take up) anesthetic is depicted by areas representing specific tissues, and the extent of anesthetic movement is depicted by the length and breadth of arrows to and from the areas depicting capacity. The illustrations incorporate increasingly important elements to kinetics, such as obesity. Obesity increases the depots available for storage of anesthetic, including anesthetic that reaches fat by intertissue diffusion. Such anesthetic returns to the circulation to delay recovery in healthy and obese patients, particularly with more soluble anesthetics. However, the increased anesthetic in fat occurs at a lower partial pressure and thus might not influence emergence materially. We hope that these illustrations will allow anesthesia practitioners to appreciate the interactions of the factors that govern inhaled anesthetic pharmacokinetics.

Impact of pexelizumab, an anti-C5 complement antibody, on total mortality and adverse cardiovascular outcomes in cardiac surgical patients undergoing cardiopulmonary bypass.

BACKGROUND: During cardiac surgery requiring cardiopulmonary bypass, pro-inflammatory complement pathways are activated by exposure of blood to bio-incompatible surfaces of the extracorporeal circuit and reperfusion of ischemic organs. Complement activation promotes the generation of additional inflammatory mediators thereby exacerbating tissue injury. We examined the safety and efficacy of a C5 complement inhibitor for attenuating inflammation-mediated cardiovascular dysfunction in cardiac surgical patients undergoing cardiopulmonary bypass. METHODS: Pexelizumab (Alexion Pharmaceuticals, Inc, Cheshire, CT), a recombinant, single-chain, anti-C5 monoclonal antibody, was evaluated in a randomized, double-blinded, placebo-controlled, multicenter trial that involved 914 patients undergoing coronary artery bypass grafting with or without valve surgery requiring cardiopulmonary bypass. RESULTS: Pexelizumab was administered intravenously as a bolus (2.0 mg/kg) or bolus plus infusion (2.0 mg/kg plus 0.05 mg/kg/h for 24 hours), and inhibited complement activation. There were no statistically significant differences between placebo-treated and pexelizumab-treated patients in the primary endpoint (composite of death, or new Q-wave, or non-Q-wave [myocardial-specific isoform of creatine kinase > 60 ng/mL] myocardial infarction, or left ventricular dysfunction, or new central nervous system deficit). However, post hoc analysis revealed a reduction in the composite of death or myocardial infarction (myocardial-specific isoform of creatine kinase >/= 100 ng/mL) for the isolated coronary artery bypass grafting, bolus plus infusion subgroup on POD 4 (p = 0.007) and on POD 30 (p = 0.004). CONCLUSIONS: Pexelizumab had no statistically significant effect on the primary endpoint. However, the reduction in death or myocardial infarction (myocardial-specific isoform of creatine kinase >/= 100 ng/mL) as revealed in the post hoc analysis in the isolated coronary artery bypass grafting bolus plus infusion subpopulation, suggests that further investigation of anti-C5 therapy for ameliorating complement-mediated inflammation and myocardial injury is warranted.

Prevalence of risk factors, and not gender per se, determines short- and long-term survival after coronary artery bypass surgery.

OBJECTIVE: Much attention has been directed towards female gender as an independent risk factor for in-hospital mortality after coronary artery bypass grafting surgery; however, the effects of surgery are known to persist for 6 months or more. Studies that have compared postoperative survival in women and men beyond hospital discharge report disparate results with regard to the independent effect of gender per se on ultimate survival. DESIGN: This investigation was a prospective, observational study. SETTING: The study was a multicenter investigation involving 24 US medical centers. PARTICIPANTS: There were 2,048 patients undergoing isolated coronary artery bypass graft surgery enrolled between September 1991 and September 1993 and after discharge. INTERVENTIONS: There were no interventions with this prospective observational study. MEASUREMENTS AND MAIN RESULTS: Preoperative demographic variables, medical history, and angiographic data were collected for each patient at the time of enrollment. Patients' vital status through the National Death Index up to August 31, 1998, were added to assess postoperative long-term survival. For survivorship analysis, the Kaplan-Meier product-limit method was used with Cox regression model. Survivorship analyses were performed separately and in combination on mortality within 30 days and 6 months of coronary artery bypass graft surgery and during the entire postoperative follow-up period. Among women, preoperative disease status, as expected, was more severe than that in men. Women were older (p = 0.0001) and had more comorbidity, such as congestive heart failure (p = 0.0019), diabetes (p = 0.0001), anemia, and hypertension (p = 0.0001). After surgery, unadjusted survival of 6 months and 5 years in women was worse than that in men. However, there were no gender-related differences in short- or long-term survival after adjusting for covariates in the multivariate model. Preoperative conditions, such as congestive heart failure, anemia, diabetes, and advanced age, are indicative of greater risk in both women and men for lower survival after coronary artery bypass graft surgery. CONCLUSIONS: Disease prevalence in women, and not gender per se, affects mid- and long-term survival after cardiac surgery. Attention, therefore, should be focused on efforts to reduce or modify such disease prevalence earlier in women, which may in turn allow longer survival after surgical intervention. Differences in postoperative survival between women and men were related to the gender differences in the distribution of preoperative risk factors.

Efficacy and safety of the cyclooxygenase 2 inhibitors parecoxib and valdecoxib in patients undergoing coronary artery bypass surgery.

OBJECTIVE: Inhibition of cyclooxygenase 2 provides analgesia in ambulatory patients. We prospectively evaluated the safety and efficacy of a newly introduced cyclooxygenase 2 inhibitor in patients undergoing coronary artery bypass grafting surgery through a median sternotomy in a randomized clinical trial. METHODS: A total of 462 patients with New York Heart Association classes I to III who were less than 77 years of age and were from 58 institutions in the United States, Canada, Germany, and the United Kingdom participated in this multicenter, phase III, placebo-controlled, double-blind, randomized, parallel-group trial. Patients were allocated at a ratio of 2:1 to parecoxib/valdecoxib or standard care (control) groups, respectively. Intravenous study drug (40 mg) was administered within 30 minutes after extubation and every 12 hours for a minimum of 3 days. Subsequently, oral treatment at a dose of 40 mg every 12 hours was initiated and administered for a combined total of 14 days. Patient-controlled analgesia with morphine, oral opioids, or acetaminophen was available as required. Assessment of the analgesic efficacy of the study drug was primarily based on morphine and morphine equivalent use. Additional efficacy evaluations included daily pain intensity, patient and physician global evaluation of study medication, and pain effect on quality of life. Clinical adverse events were assessed by the principal investigator at each site from the time of the first dose through the 30-day postdosing period. RESULTS: Patients in the parecoxib/valdecoxib group received significantly less morphine or morphine equivalents than patients in the control group during the 0- to 24-hour (P =.009), 24- to 48-hour (P =.017), 72- to 96-hour (P =.002), 96- to 120-hour (P =.004), and 120- to 144-hour (P =.037) periods. Both patients (P <.001) and physicians (P <.001) evaluated the study medication as significantly better than control therapy. The modified Brief Pain Inventory questionnaire used in the oral dosing period detected significant improvements in the parecoxib/valdecoxib treatment group in 6 of 8 domains tested (eg, current pain, worst pain, and mood) beginning on day 4 and continuing for at least 4 days. Although there were no differences between the groups in overall adverse events, serious adverse events occurred twice as frequently in parecoxib/valdecoxib-treated patients (19.0%, 59/311 patients) than in control patients (9.9%, 15/151 patients; P =.015). Regarding individual serious adverse events, a greater incidence in sternal wound infection was found in the parecoxib/valdecoxib patients (10 [3.2%]) versus control patients (0 [0%]) (P =.035). The incidences of other individual serious adverse events, including cerebrovascular complications, myocardial infarction, and renal dysfunction, were proportionally greater but not significantly different between the groups. CONCLUSIONS: In patients undergoing coronary artery bypass grafting surgery, the cyclooxygenase 2 inhibitor combination, parecoxib/valdecoxib, was effective for postoperative analgesia. However, the 14-day treatment regimen also was associated with an increased incidence of serious adverse events overall and sternal wound infections in particular. Therefore our study raises important concerns requiring their comprehensive evaluation in a large-scale trial before these cyclooxygenase 2 inhibitors are used in patients undergoing coronary artery bypass grafting surgery.