Obstructive sleep apnoea and perioperative complications in bariatric patients.

BACKGROUND: The objective of this study was to determine the relationship between perioperative complications and the severity of obstructive sleep apnoea (OSA) in patients undergoing bariatric surgery who had undergone preoperative polysomnography (PSG). METHODS: The records of 797 patients, age >18 yr, who underwent bariatric operations (442 open and 355 laparoscopic procedures) at Mayo Clinic and were assessed before operation by PSG, were reviewed retrospectively. OSA was quantified using the apnoea-hypopnoea index (AHI) as none (≤ 4), mild (5-15), moderate (16-30), and severe (≥ 31). Pulmonary, surgical, and 'other' complications within the first 30 postoperative days were analysed according to OSA severity. Logistic regression was used to assess the multivariable association of OSA, age, sex, BMI, and surgical approach with postoperative complications. RESULTS: Most patients with OSA (93%) received perioperative positive airway pressure therapy, and all patients were closely monitored after operation with pulse oximetry on either regular nursing floors or in intensive or intermediate care units. At least one postoperative complication occurred in 259 patients (33%). In a multivariable model, the overall complication rate was increased with open procedures compared with laparoscopic. In addition, increased BMI and age were associated with increased likelihood of pulmonary and other complications. Complication rates were not associated with OSA severity. CONCLUSIONS: In obese patients evaluated before operation by PSG before bariatric surgery and managed accordingly, the severity of OSA, as assessed by the AHI, was not associated with the rate of perioperative complications. These results cannot determine whether unrecognized and untreated OSA increases risk.

Sensitive determination of nitrofurantoin in human plasma and urine by high-performance liquid chromatography.

A highly sensitive and selective HPLC method was developed and validated for the determination of nitrofurantoin in human plasma and urine. The method involves the liquid-liquid extraction of drug and internal standard from plasma with ethyl acetate followed by evaporation and reconstitution in mobile phase. Urine samples were simply diluted with purified water. UV detection was done at 370 nm. The limit of quantification for nitrofurantoin in plasma was 0.010 micrograms/ml. In urine nitrofurantoin could be quantified down to 0.380 microgram/ml. Linearity was proven over the whole calibration range in plasma (2.48-0.0100 microgram/ml) as well as in urine (187 micrograms/ml-0.380 microgram/ml). The method was validated according to Good Laboratory Practice guidelines and its suitability was demonstrated by analysis of samples from a pharmacokinetic study.

Cimetidine increases steady state plasma levels of propranolol.

1 The influence of cimetidine (1000 mg daily) on propranolol steady state plasma levels has been studied in seven normal volunteers. Cimetidine was used as a 200 mg normal release tablet whereas propranolol was given as a 160 mg slow release formulation once daily. 2 After 1 day of cimetidine treatment (day 9 of the study) the mean (Css) and minimal (Css min) propranolol steady state plasma levels increased significantly from 24.1 +/- 14.9 ng/ml (mean +/- s.d.) to 39.2 +/- 27.7 ng/ml (P = 0.01) and from 14.8 +/- 9.3 ng/ml to 27.1 +/- 21.2 ng/ml (P = 0.03), respectively. The apparent oral clearance (Clo) was reduced from 6.7 +/- 4.3 l/min to 4.6 +/- 3.11/min (P = 0.006). 3 A prolongation of cimetidine administration to 5 days (day 13 of the study) intensified this effect significantly (P = 0.02): Css of propranolol was elevated from 23.2 +/- 14.4 ng/ml to 44.9 +/- 26.7 ng/ml (P = 0.003); Css min was increased from 14.1 +/- 10.2 ng/ml to 28.4 +/- 17.9 ng/ml (P = 0.02) while Clo decreased from 6.9 +/- 4.1 1/min to 3.3 +/- 1.61/min (P = 0.006). 4 We conclude that the drug interaction between propranolol and cimetidine leads to significant elevations of propranolol steady state plasma concentrations which may cause a clinically relevant enhancement of the effect of a given dosage. This requires careful observation of patients under concomitant treatment with propranolol and cimetidine.