Difficult mask ventilation in obese patients: analysis of predictive factors.

BACKGROUND: This study aimed to determine the accuracy of commonly used preoperative difficult airway indices as predictors of difficult mask ventilation (DMV) in obese patients (BMI >30 kg/m2). METHODS: In 309 consecutive obese patients undergoing general surgery, the modified Mallampati test, patient's Height/Thyromental distance ratio, Inter-Incisor Distance, Protruding Mandible (PM), history of Obstructive Sleep Apnea and Neck Circumference (NC) were recorded preoperatively. DMV was defined as Grade 3 mask ventilation (MV) by the Han's scale (MV inadequate, unstable or requiring two practitioners). Data are shown as means±SD or number and proportions. Independent DMV predictors were identified by multivariate analysis. The discriminating capacity of the model (ROC curve area) and adjusted weights for the risk factors (odds ratios) were also determined. RESULTS: BMI averaged 42.5±8.3 kg/m2. DMV was reported in 27 out of 309 patients (8.8%; 95%CI 5.6-11.9%). The multivariate analysis retained NC (OR 1.17; P<0.0001), limited PM (1.99; P=0.046) and Mallampati test (OR 2.12; P=0.009) as risk predictors for DMV. Male gender was also included in the final model (OR 1.87; P=0.06) as biologically important variable albeit the borderline statistical significance. The model yielded a good discriminating capacity (ROC curve 0.85). The four parameters were used to create an unweighted prediction score (ROC curve 0.84) with >2 associated factors as the best discriminating point for DMV. CONCLUSION: Obese patients show increased incidence of DMV with respect to the undifferentiated surgical population. Limited PM, Mallampati test and NC are important DMV predictors.

Muscle enzyme elevation after elective neurosurgery.

BACKGROUND: Serum creatine kinase and myoglobin elevation has been described involving muscle manipulation after surgery and also after bariatric, urologic and gynaecologic procedures. It encompasses a wide range of severity, reflecting in the worst cases true rhabdomyolysis. We occasionally noted creatine kinase elevations after intracranial neurosurgery, an occurrence that has not yet been described. To assess whether the issue of postoperative muscle enzyme elevation is relevant to neurosurgery, we prospectively measured serum creatine kinase and myoglobin in a series of neurosurgical patients submitted to craniotomy. MATERIALS AND METHODS: We studied 30 patients aged 22-69 yr submitted to craniotomy. Blood samples were taken prior to the procedure, at the end of anaesthesia and on the first, second and third postoperative days. Blood was checked for creatine kinase, myoglobin, lactate dehydrogenase, aspartate aminotransferase, alanine aminotransferase, blood urea nitrogen, creatinine and serum electrolytes. We recorded the patient's age, sex, height, weight and body mass index. Throughout surgery, we recorded the highest and the lowest body temperature and sampled the mean arterial pressure at 5 min intervals. We performed backwards stepwise logistic regression analysis to identify the elements that best correlate with the development of cell muscle damage. RESULTS: On the first postoperative day creatine kinase peaked from baseline (305 (107-1306) UI L(-1) vs. 59 (42-94) UI L(-1); P < 0.001) while myoglobin rose significantly from baseline to the end of surgery (70 (42-147) ng mL(-1) vs. 36 (3044) ng mL(-1); P = 0.002). Logistic regression showed that length of surgery was the only factor clearly influencing peak creatine kinase (P < 0.001; R2 0.7) and myoglobin (P = 0.011; R2 0.41) concentration. CONCLUSIONS: Creatine kinase and myoglobin elevation may occur after intracranial neurosurgery. In our series, length of surgery was a risk factor.

Comparison between epidural infusion of fentanyl/bupivacaine and morphine/bupivacaine after orthopaedic surgery.

PURPOSE: To compare epidural infusions of bupivacaine-fentanyl and bupivacaine-morphine mixtures for postoperative pain relief after total hip replacement. METHODS: In a prospective, randomized, double-blind study, 30 ASA physical status I-II patients undergoing total hip replacement were studied. Anaesthesia was provided by combined general/epidural anaesthesia without epidural opioids. Postoperative epidural analgesia was by continuous infusion of bupivacaine 0.125% (4 ml.hr-1) with either 0.05 mg.ml-1 morphine (morphine, n = 15) or 0.005 mg.ml-1 fentanyl (fentanyl, n = 15). Visual analogue pain scale (VAS), sedation (four-point scale), respiratory rate, pulse oximetry, rescue analgesics and supplemental oxygen were recorded by a blind observer at 1, 3, 6, 9, 12 and 24 hr after surgery. RESULTS: No differences in pain relief, sedation, or non-respiratory side effects were observed between the two groups. Rescue analgesics were required in three patients in the fentanyl group (20%) and in two receiving morphine (13.3%) (P:NS). Two patients in the fentanyl group and three in the morphine group required oxygen due to SpO2 < 90% (P:NS). Both opioid/bupivacaine mixtures decreased haemoglobin oxygen saturation compared with preoperative values. The mean +/- SD SpO2 values measured at 3, 6, 12 and 24 hr were 94.4 +/- 1, 92.6 +/- 0.9, 92 +/- 0.8, and 92.8 +/- 1 in the morphine group, 95.3 +/- 0.5, 95 +/- 0.5, 94.6 +/- 1.2, and 95.6 +/- 1 in the fentanyl group (P < 0.05). CONCLUSION: Continuous epidural infusion of bupivacaine-morphine or bupivacaine-fentanyl mixtures provided similar pain relief. Patients receiving morphine showed a more marked decrease in SpO2 than those receiving fentanyl. However, the average SpO2 remained > 90% in both groups.

[Anesthesiologic incidents from esophageal intubation. Presentation of three cases and medico-legal evaluation]. / Incidenti anestesiologici da intubazione esofagea. Presentazione di tre casi clinici e valutazione medico-legale.

Undiagnosed esophageal intubation is still prominently in anesthesia-related morbidity and mortality. Three cases of undiagnosed esophageal intubation taken into consideration for possible anesthesiologic malpractice are presented. A review of the international anesthetic-related morbidity and mortality statistics indicates that this misadventure remains a problem even among anesthesia personnel, a medical population specifically trained in such a procedure. It is not only the frequency of this misadventure but the potential catastrophic consequences for the patient that underline the importance of being able to recognise and correct an esophageal intubation. The reliability of commonly prescribed methods of assessing tracheal tube position is reviewed and the conclusion is drawn that continuous end-tidal carbon dioxide measurement during anesthesia is perhaps the most reliable means under all circumstances for determining proper tube position and should be employed routinely whenever possible.

Active warming, not passive heat retention, maintains normothermia during combined epidural-general anesthesia for hip and knee arthroplasty.

STUDY OBJECTIVE: to compare passive heat retention by low-flow anesthesia, alone and with additional thermal insulation by reflective blankets, with forced-air warming preventing intraoperative hypothermia during combined epidural-general anesthesia. DESIGN: Randomized, controlled study. SETTING: Inpatient anesthesia at a university department of orthopedic surgery. PATIENTS: 30 ASA physical status I and II patients, who were scheduled for elective hip or knee arthroplasty and were free from systemic disease. INTERVENTIONS: Patients received epidural block up to T10 by alkalinized lidocaine 2%, and then were administered standard general anesthesia by means of low-flow rebreathing system (fresh gas flow = 1 L/min). All procedures started between 8 and 10 AM, and operating room (OR) temperature was maintained between 21 degrees and 23 degrees C, with relative humidity ranging between 40% and 45%. For heat retention or warming therapy, patients received either low-flow anesthesia only (control, n = 10), low-flow anesthesia with additional reflective blankets (blanket, n = 10), or low-flow anesthesia with active forced-air warming (forced-air, n = 10). Tympanic temperature was measured at OR arrival (baseline); immediately following general anesthesia induction; 30, 60, 90, and 120 minutes from general anesthesia induction; and at the end of surgery. MEASUREMENTS AND MAIN RESULTS: Duration of anesthesia, invasiveness of surgery, and baseline core temperature were similar in the three groups. Core temperature decreased in all the three groups 30 minutes after general anesthesia induction compared with baseline (p < 0.01); afterwards, it progressively decreased in the control and blankets groups (p = 0.004), with a reduction from baseline values measured at the end of surgery of 2.0 degrees C and 1.6 degrees C, respectively. In the forced-air group, after the initial significant decrease (p = 0.01 vs. baseline), core temperature progressively increased to 35.8 +/- 0.6 degrees C, which was similar to preoperative values and significantly higher than either the control or blankets groups (p = 0.004). CONCLUSIONS: During combined epidural-general anesthesia for elective hip and knee arthroplasty, passive heat retention by means of low-flow anesthesia alone and in combination with reflective blankets is ineffective in maintaining intraoperative normothermia and definitely inferior to active forced-air warning.