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 microg/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 microg x kg(-1) x 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.

Correct depth of insertion of right internal jugular central venous catheters based on external landmarks: avoiding the right atrium.

OBJECTIVE: Radiographically, a central venous catheter (CVC) tip should lie at the level of the right tracheobronchial angle. Precalculation of length of CVC insertion may avoid unnecessary catheter malposition. The purpose of this study was to assess the accuracy of a method of CVC positioning, based on external topographic landmarks. DESIGN: A prospective, randomized study. SETTING: University-affiliated hospital, single institution. PARTICIPANTS: Patients scheduled for surgery. INTERVENTIONS: Patients were allocated for insertion of the catheter through the right internal jugular vein to either a fixed, predetermined, 15-cm length (n = 50) or to a depth calculated topographically (n = 50) by drawing a line from the level of the thyroid notch to the sternal manubrium. The catheter was repositioned if its tip was situated >5 cm above the carina or >1 cm below it. The distance from the catheter tip to the carina was measured. The main study endpoint was the need for catheter repositioning. MEASUREMENTS AND MAIN RESULTS: Two percent of patients required repositioning in the topographic group compared with 78% in the 15-cm length group (p < 0.001). No patient in the topographic group and 10 patients (20%) in the 15-cm group had the catheter placed in the right atrium (p < 0.05). The mean distance from the CVC tip to the carina was 2.9 +/- 1.4 cm above the carina in the topographic group and 1.9 +/- 1.1 cm below the carina in the 15-cm length group (p < 0.001). No patient had a too proximally placed catheter. Insertion lengths in the topographic group ranged between 9 and 12.5 cm. CONCLUSIONS: It is recommended to use the topographic approach in deciding CVC depth with right internal jugular CVC placement.

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.

Proper insertion depth of endotracheal tubes in adults by topographic landmarks measurements.

STUDY OBJECTIVE: To evaluate a new method of endotracheal tube (ETT) positioning relative to carina, based on external topographic landmarks. DESIGN: Prospective, randomized, crossover study. SETTING: Operating room, university hospital. PATIENTS: 200 American Society of Anesthesiologists (ASA) physical status I-II patients (100 women and 100 men) scheduled for elective surgery with general anesthesia. INTERVENTIONS: ETT insertion depth was topographically determined by adding the distance measured (in cm) from the right mouth corner to right mandibular angle to the distance measured from the right mandibular angle to a point situated on the center of a line running transversally through the middle of the sternal manubrium. This method was compared to the 21/23 cm insertion depth method. MEASUREMENTS: ETT position was assessed fiberoptically. The main end point was considered the percentage of ETT tips situated more than 25% higher or lower than a predetermined "best" tip position (4 cm above the carina). MAIN RESULTS: There were 58.5% ETT tips positioned too closely (<3 cm above the carina) to the carina with the control method and 24% with the study method (P=0.0001). No ETT tip was too high (>5 cm above the carina). The tip-carina distance was shorter in women (2.7+/-2.5 vs 3.6+/-2.2 cm in men P=0.0001) and in those aged more than 65 years (2.8+/-2.4 vs 3.4+/-2.4 cm with age less than 65 years; P=0.012) only with the 21/23 cm method. CONCLUSIONS: With our new ETT positioning method, there were fewer ETTs positioned outside the desired range of distance to carina. Our method may be especially valuable in women and in patients older than 65 years.

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.

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 degrees 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 degrees C, to 37.1 degrees C; in contrast, temperature in the aggressive group decreased significantly, by 0.4 +/- 0.2 degrees C, to 36.4 degrees 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.

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

PURPOSE: We investigated the association between morbid obesity and difficult laryngoscopy (DL). METHODS: In a prospective, controlled study we evaluated the impact of different variables on the prediction of DL in 200 morbidly obese (study group-SG), and 1272 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. RESULTS: The 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. CONCLUSIONS: Increased 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.

Endotracheal intubation with a gum-elastic bougie in unanticipated difficult direct laryngoscopy: comparison of a blind technique versus indirect laryngoscopy with a laryngeal mirror.

UNLABELLED: We evaluated the efficacy of intubation over a gum-elastic bougie by using either a blind technique or indirect laryngoscopy with a laryngeal mirror in patients with unexpected difficult direct laryngoscopy. In a prospective study, 60 consecutive patients with an unexpected Grade III or IV direct laryngoscopy were randomly allocated for intubation with a gum-elastic bougie either blindly (Group 1) or by indirect laryngoscopy with a laryngeal mirror (Group 2). We evaluated the failure rate of each method of intubation, complications related to either method, and the time required for intubation. Out of 725 patients evaluated over a 2-mo period, 60 patients (8.3%) had a Grade III laryngoscopy, and 30 of these were randomized into each group. There were 8 failed intubations in Group 1 compared with 1 failed intubation in Group 2 (P < 0.05). All eight failures in the blind intubation group ended with esophageal intubation. No additional complications were noted in either group. The time required for endotracheal intubation with each group was not significantly different (45 +/- 10 s versus 44 +/- 11 s). We conclude that intubation with a gum-elastic bougie had a lower failure rate using indirect laryngoscopy with a laryngeal mirror than a traditional blind technique. IMPLICATIONS: We evaluated the efficacy of intubation over a gum-elastic bougie by using either a blind technique or a laryngeal mirror. Intubation with a gum-elastic bougie had a lower failure rate using indirect laryngoscopy with a laryngeal mirror (P < 0.05) than a traditional blind technique.