Marian Weisenberg

Increased body mass index per se is not a predictor of difficult laryngoscopy.

PurposeWe investigated the association between morbid obesity and difficult laryngoscopy (DL).MethodsIn a prospective, controlled study we evaluated the impact of different variables on the prediction of DL in 200 morbidly obese (study group-SG), and 1,272 non-obese (control group-CG) patients undergoing elective surgery. Variables assessed included age, sex, body mass index (BMI), protruding, loose, and missing upper teeth, thyro-mental distance, temporo-mandibular joint (TMJ) function, neck extension, and Mallampati class. A Cormack grade III or IV was considered DL.ResultsThe SG patients were younger (P < 0.000), there were more females in the SG (P < 0.000) and more in the SG had teeth problems (P = 0.026). More patients in the SG (10%vs 1%), had obstructive sleep apnea (P < 0.001) with 90% of them in the SG having a grade III laryngoscopy. High BMI did not affect the laryngoscopy difficulty (P = 0.56). Multivariable regression analysis revealed that morbid obesity, increased age, male sex, pathology of TMJ, and higher Mallampati class, were independent predictors of DL. When interaction between the predictors and the group was added to the multivariable model, the SG was no longer a predictor by itself, rather its association with abnormal upper teeth turned to be significant for prediction of DL.ConclusionsIncreased age, male sex, TMJ pathology, Mallampati 3 and 4, a history of obstructive sleep apnea and abnormal upper teeth were associated with a higher incidence of DL. The magnitude of BMI had no influence on difficulty with laryngoscopy.RésuméObjectifNous avons examiné le lien entre l’obésité morbide et la laryngoscopie difficile (LD).MéthodeDans une étude prospective et contrôlée, nous avons évalué l’impact de différentes variables sur la prédiction de LD chez 200 patients présentant une obésité morbide (groupe expérimentai — GE) et 1272 patients non obèses (groupe témoin — GT) devant subir une intervention chirurgicale réglée. Les variables évaluées ont été: l’âge, le sexe, l’indice de masse corporelle (IMC), la protrusion, la mobilité et l’absence de dents supérieures, la distance thyromentonnière, la compétence de l’articulation temporo-mandibulaire (ATM), l’extension du cou et la classification de Mallampati. Une cote III ou IV de Cormack a été considérée comme une LD.RésultatsLes patients du GE étaient plus jeunes (P < 0,000), comprenaient plus de femmes (P < 0.000) et présentaient plus de problèmes dentaires (P = 0,026). Un plus grand nombre de patients du GE (10 % vs 1%) avaient une apnée du sommeil d’origine obstructive (P < 0,001) dont 90 % présentaient une laryngoscopie de classe III. Un IMC élevé n’a pas eu d’influence sur la laryngoscopie difficile (P = 0,56). Une analyse de régression multivariable a révélé que l’obésité morbide, l’âge avancé, le sexe mâle, une pathologie de l’ATM et une cote de Mallampati plus élevée ont été des prédicteurs indépendants de LD. Si on ajoute l’interaction entre les prédicteurs et le groupe au modèle multivariable, le GE n’est pius un prédicteur en lui-même, quoique son association avec une dentition supérieure anormale apparaisse significative pour prédire une LD.ConclusionLe vieillissement, le sexe masculin, une pathologie de l’ATM, une ciasse 3 ou 4 de Mallampati, des antécédents d’apnée du sommeil d’origine obstructive et des anomalies de la dentition supérieure ont été associés à une plus grande incidence de LD. Un IMC plus élevé n’a pas d’influence sur les difficultés laryngoscopiques.

Association of ethnicity with the minimum alveolar concentration of sevoflurane.

Background:Selective breeding produces animal strains with varying anesthetic sensitivity. It thus seems unlikely that various human ethnicities have identical anesthetic requirements. Therefore, the authors tested the hypothesis that the minimum alveolar concentration of sevoflurane differs significantly as a function of ethnicity. Methods:The authors recruited 90 American Society of Anesthesiologists physical status I and II adult patients belonging to three Jewish ethnic groups: European, Oriental, and Caucasian (from the Caucasus Mountain region). All were scheduled to undergo surgery requiring a skin incision exceeding 3 cm. Without premedication, anesthesia was induced with 6–8% sevoflurane in 100% oxygen, and tracheal intubation was facilitated with succinylcholine. The skin incision was made after a predetermined end-tidal concentration of sevoflurane of 2.0% was maintained for at least 10 min in the first patient in each group. Blinded investigators observed the patient for movement during the subsequent minute. The concentration in the next patient was increased by 0.2% when patients moved, or decreased by the same amount when they did not. Results are presented as means [95% confidence intervals]. Results:Morphometric and demographic characteristics were similar among the groups; however, mean arterial pressure was slightly greater in European Jews. Minimum alveolar concentration for sevoflurane was greatest in Caucasian Jews (2.32% [2.27–2.41%]), less in Oriental Jews (2.14% [2.06–2.22%]), and still less in European Jews (1.9% [1.82–1.99%]) (P < 0.001). Conclusions:The results suggest that minimum alveolar concentration varies as a function of ethnicity. However, the extent to which confounding characteristics contribute, including lifestyle choices and environmental factors, remains unknown.

Difficult laryngoscopy: incidence and predictors in patients undergoing coronary artery bypass surgery versus general surgery patients.

OBJECTIVE Cardiac surgery patients might have a higher incidence of difficult laryngoscopy than the general population because of older age, dental problems, and obesity. The authors estimated the incidence and predictors of difficult laryngoscopy in coronary artery bypass surgery patients. DESIGN Prospective, controlled study. SETTING University setting. PARTICIPANTS Patients undergoing coronary artery bypass or general surgery. INTERVENTIONS Two hundred consecutive patients undergoing coronary artery bypass graft and 444 general surgery patients, all aged >40 years, were compared for the incidence and predictors of difficult laryngoscopy, defined as a grade III or IV view. MEASUREMENTS AND MAIN RESULTS Predictors of difficult laryngoscopy were considered mouth opening <4 cm, limited cervical mobility, thyromental distance <6 cm, protruding or partially missing upper teeth, and Mallampati classes 3 and 4. More cases of difficult laryngoscopy were recorded in cardiac patients (10% v 5.2%, p <0.023). The cardiac patients were older, mostly men, and belonged to ASA III-IV risk classes. Mallampati classes 3 and 4 were more frequent in the control group. With univariate analysis, difficult laryngoscopy correlated with 7 variables: older age, ASA-IV risk class, protruding or partially missing upper teeth, limited mouth opening, limited neck movement, thyromental distance <6 cm, and diabetes mellitus. Multivariate analysis adjusted for propensity score identified older age (odds ratio = 1.05/yr, 95% confidence interval = 1.005-1.09, p < 0.03) and limited neck movement (odds ratio = 9.5, 95% confidence interval = 2.2-41, p < 0.003), but not cardiac surgery per se, as independent predictors of difficult laryngoscopy. CONCLUSIONS Difficult laryngoscopy was more frequent in cardiac surgery patients (10% v 5.2%). Older age and limited neck movement, but not cardiac surgery per se, were independent predictors of difficult laryngoscopy.

Dose-dependent hemodynamic effects of propofol induction following brotizolam premedication in hypertensive patients taking angiotensin-converting enzyme inhibitors

STUDY OBJECTIVE To determine a propofol dose that minimizes hemodynamic changes on induction of anesthesia in patients chronically taking angiotensin-converting enzyme inhibitors (ACEIs). DESIGN Prospective, randomized trial. SETTING Operating room of a university-affiliated general hospital. PATIENTS 88 ASA physical status II and II hypertensive patients chronically taking ACEIs, scheduled for elective abdominal surgery with general anesthesia. INTERVENTIONS Patients were premedicated with brotizolam and anesthesia was induced with propofol, fentanyl, and rocuronium; anesthesia was then maintained with isoflurane. Patients were randomly assigned to undergo anesthetic induction with propofol in doses of 1.3, 1.6, 2.0, or 2.3 mg/kg. MEASUREMENTS Oscillometric blood pressure and heart rate were evaluated at one-minute intervals during the first 10 minutes of anesthesia. End-tidal isoflurane concentrations were also recorded. Episodes of hypertension, tachycardia, bradycardia, or hypotension (defined as > 30% of baseline values) were managed per protocol with esmolol, atropine, phenylephrine, or ephedrine. Administration of any of these drugs was considered a pharmacological intervention. MAIN RESULTS After adjusting for covariables in a model assuming a linear relationship between dose and log-response, each propofol dose increase of 0.3 mg/kg was associated with a 31% increase in mean number of hypotensive/bradycardic episodes requiring interventions (95% confidence intervals of +5% and +65%; P = 0.018). Based on our model, a dose of 1.3 mg/kg resulted in the fewest number of pharmacological interventions. CONCLUSIONS In patients chronically taking ACEIs, low doses of propofol reduce hemodynamic instability.

Listening to music during anesthesia does not reduce the sevoflurane concentration needed to maintain a constant bispectral index.

BACKGROUND: Music reduces stress responses in awake subjects. However, there remains controversy about the role of music or therapeutic suggestions during general anesthesia and postoperative recovery. We thus tested the hypothesis that intraoperative exposure to soothing music reduces the end-tidal concentration of sevoflurane (ETSevo) necessary to maintain bispectral index (BIS) near 50 during laparoscopic surgery. METHODS: Forty patients, aged 40–60 yrs, ASA I and II, undergoing laparoscopic hernias or cholecystectomy under general anesthesia were studied. All patients were connected to a BIS monitor. Anesthesia was induced with fentanyl 2 &mgr;g/kg, sevoflurane in oxygen, rocuronium (0.6 mg/kg), and maintained with sevoflurane in oxygen and 50% nitrous oxide, with an infusion of fentanyl (1 &mgr;g · kg−1 · h−1). Sevoflurane was titrated to maintain BIS near 50 throughout the procedure. Patients were randomly assigned to either listen to music or not. RESULTS: The ETSevo necessary to maintain a BIS near 50 was virtually identical in patients who listened to music (1.29 ± 0.33%) and those who did not (1.27 ± 0.33%, P = 0.84). Patients who listened to music reported slightly less pain, but the difference was not statistically significant. Mean arterial blood pressure was slightly higher in patients who listened to music (101 ± 11 mm Hg) than in those who did not (94 ± 10 mm Hg, P = 0.040). CONCLUSIONS: The end-tidal concentration of sevoflurane required to maintain BIS near 50 during laparoscopic cholecystectomy was virtually identical in patients exposed to music or not. Although previous work suggests that music reduces preoperative stress and may be useful during sedation, our results do not support the use of music during surgery.

The Effects of Hydration on Core Temperature in Pediatric Surgical Patients

Background Reduced vascular volume might influence body temperature by diverting heat flow from peripheral tissues to the central organs. We therefore tested the hypothesis that mild hypovolemia helps to prevent intraoperative hypothermia in pediatric patients. Methods Twenty-two pediatric patients (aged 1–3 yr) undergoing prolonged minor surgery were randomly assigned to conservative (n = 12) or aggressive (n = 10) perioperative fluid management. The conservative group fasted 8 h before surgery and received a crystalloid at 1 ml · kg−1 · h−1 during surgery. The aggressive group was allowed to drink liquids until 3 h before surgery and was given a maintenance crystalloid at 8 ml · kg−1 · h−1. Anesthesia was induced and maintained with halothane in nitrous oxide. Ambient temperature was kept near 25°C, but the patients were not actively warmed. During recovery from anesthesia, additional fluid was given to the conservative group so that perioperative fluid totaled 9.5 ml · kg−1 · h−1 in both groups. Results Intraoperative body weight remained unchanged in the aggressive group and decreased only 1% in patients managed conservatively. Heart rate was slightly greater in the conservative group (107 ± 9 vs. 95 ± 4 beats/min, P = 0.002), but blood pressure was similar. Esophageal temperature in patients whose fluid was managed conservatively increased significantly, by 0.4 ± 0.3°C, to 37.1°C; in contrast, temperature in the aggressive group decreased significantly, by 0.4 ± 0.2°C, to 36.4°C (P < 0.001 between groups). Temperatures remained significantly different 1 h after surgery. Conclusions Conservative fluid management, which decreased body weight by only 1%, prevented reduction in core body temperature, presumably by reducing dissipation of metabolic heat from the core thermal compartment to peripheral tissues.

The "inverted traffic light" obstetric difficult airway management algorithm.

The obstetric anesthetist’s approach to the difficult airway is complicated by the simultaneous risk to both the mother and the fetus. In this regard, the airway decision making must be guided by the urgency grade of a planned cesarean section—CS [1, 2]. Harmer [2] classified the urgency of delivery into 5 grades: Grade 1—The mother’s life depends upon the completion of surgery (maternal cardiac arrest, massive bleeding); Grade 2—Regional anesthesia unsuitable (coagulopathy); Grade 3—Sudden and severe fetal distress not recovering between contractions (prolapsed cord); Grade 4—Long-standing fetal distress with good recovery between contractions; Grade 5—Elective CS. Harmer’s grading has the advantage of correlating the decision making with the intubation/ventilation difficulties [2]. It is evident that with grade 1, CS has to be performed even with failed intubation and ventilation [3]. A controversial clinical situation, associated with an inherently difficult decision making is grade 3 CS, where the airway management decision has to be based upon the obstetric circumstances and the quality of the maintained airway [4]. Despite the perception of fetal compromise, consideration should be given to waking the mother up if the airway cannot be controlled or maintained [5]. Management algorithms may help the practitioner to solve, in an organized manner, a predicted difficulty or an unexpected critical airway event. However, airway algorithms are often too complex to be recalled during a critical incident [6]. We present our ‘‘inverted traffic light’’ difficult obstetric airway algorithm—see Fig. 1. This is intended to be a one page, simple, though comprehensive colored algorithm. The algorithm resembles an upside-down traffic light, where green color represents a relatively safe management domain, while red signifies the most dangerous situation. Grade 3 CS was not included in this algorithm owing to the controversial management approaches to this CS category. We should remark that for a situation of predicted difficult airway in a non-emergent CS (green light—scenario A in the algorithm), with spinal anesthesia following epidural analgesia, a dose reduction of local anesthetics has to be considered to avoid a subsequent high block, especially after administration of a recent epidural bolus. With failed intubation (scenario B2 in the algorithm) there is an option to use an LMA variant. Each variant has specific advantages: the LMA classic is easy to insert, the ProSeal and Supreme have a drainage tube while the intubating LMA may serve as a conduit for fiberoptic intubation. With failed intubation and ventilation (scenario C in the algorithm) the patient should be awakened except for grade 1 CS. T. Ezri (&) M. Weisenberg S. Evron Department of Anesthesia, Wolfson Medical Center (Affiliated to Tel Aviv University), 58100 Holon, Israel e-mail: tezri@bezeqint.net