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Background: The aim of this study was to determine whether the ED(50) dose of bupivacaine 0.5% for supraclavicular brachial plexus block increases with increasing body mass index (BMI).Methods: This double-blind, non-randomized trial followed an up-and-down sequential allocation design. Adult patients undergoing elective upper limb surgery under ultrasound-guided supraclavicular brachial block were recruited. A preliminary study was used to guide the dosing schedule for the main study in which patients were divided into three groups according to their BMI (Group A, BMI >27 kg m(-2); Group B, BMI 24-27 kg m(-2); Group C, BMI <24 kg m(-2)). The study design and analysis followed Dixon's small sample model using a 'nominal' sample size of six per group.Results: Twenty-one patients were recruited to the preliminary study. Using isotonic regression, the ED(50) for bupivacaine 0.5% was estimated to be 8.9 ml [95% confidence interval (CI) 7.8-15.9]. In comparison, the ED(50) volume was found to be 10.8 ml (95% CI 5.9-19.7) using the Dixon-Massey formula. In the main study, six patients were recruited in each group with mean (range) BMI of 31.5 (27.2-38.8) kg m(-2) in Group A, 25.6 (24.4-26.3) kg m(-2) in Group B, and 21.6 (19.7-23.8) kg m(-2) in Group C. The ED(50) (95% CI) for Groups A, B, and C were 8.9 (6.2-12.7), 10.7 (7.5-15.4), and 13.4 (9.3-19.1) ml, respectively (P=0.05 for Group A vs Group C).Conclusions: Our study demonstrates that the ED(50) of bupivacaine 0.5% does not increase with an increase in BMI. We found evidence of a possible inverse relationship between ED(50) and BMI. [ABSTRACT FROM AUTHOR]

Study Objectives: To assess the utility of nasopharyngeal tube insertion in the management of hypoxemia during flexible bronchoscopy (FB) in lung transplant recipients, and to determine the incidence and risk factors of upper-airway obstruction (UAO) leading to significant hypoxemia during FB.Setting: Heart-lung transplant unit of a university hospital.Patients and Methods: Ninety-six lung transplant recipients (47 men and 49 women; mean +/- SD age, 41.4 +/- 13.1 years) underwent 714 FB procedures from January 1997 to May 2000.Intervention: A fall in oxygen saturation (< or = 90%) in patients receiving 6 L/min of oxygen via nasal prongs was treated with insertion of a nasopharyngeal tube, continued oxygen supplementation, and withdrawal of the bronchoscope to the trachea. If oxygen desaturation persisted at < 90% despite additional oxygen administration via a 7F catheter placed either just above the larynx or in the proximal trachea, the bronchoscope was withdrawn, reversal of sedation was administered, and bag and mask ventilation was instituted until satisfactory spontaneous ventilation was achieved.Results: Forty-six patients (47.9%) were treated with nasopharyngeal tube insertion on 102 occasions at a mean duration of 168 +/- 178 days after lung transplantation. In 90 of 102 procedures (88.2%), significant hypoxemia due to UAO was successfully treated with nasopharyngeal tube insertion. The mean oxygen saturation after nasopharyngeal tube insertion was 97 +/- 3%. Male gender, increase in body mass index after lung transplantation, and presence of obstructive sleep apnea were significant factors associated with the need for nasopharyngeal tube insertion during FB in lung transplant recipients.Conclusions: Significant oxygen desaturation during FB in lung transplant recipients is mainly due to UAO. Insertion of a nasopharyngeal tube is a novel and a highly effective approach to the management of acute hypoxemia during FB. [ABSTRACT FROM AUTHOR]