Anesthesiology
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Despite evidence from animal experiments to the contrary, nitrous oxide (N2O) reportedly does not induce myocardial ischemia when used as an adjunct to fentanyl anesthesia in patients with coronary artery disease who have well-preserved left ventricular (LV) function. However, the incidence of ischemia with N2O administration in similar patients with poor LV function may be different. The effects of N2O on segmental LV function, as determined by two-dimensional transesophageal echocardiography, changes in the ST-segment of the electrocardiogram were compared with the effects of an equal concentration of nitrogen (N2) (crossover design) in 70 patients who required elective coronary artery bypass grafting. ⋯ Preoperative calcium channel blockers made no such differences. Onset of ischemia was not closely associated with hemodynamic changes. Thus, N2O does not induce clinically detectable myocardial ischemia in patients who have coronary artery disease, and poor LV function in situations in which the effects of deepening anesthetic depth and mild depression of global myocardial function are deemed desirable or harmless.
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Randomized Controlled Trial Comparative Study Clinical Trial
Effect of oral liquids and ranitidine on gastric fluid volume and pH in children undergoing outpatient surgery.
Eighty-eight children (mean age 5.6 yr, range 1-14 yr) about to undergo elective outpatient surgery were randomly assigned to four groups. All children were given phenolsulfonphthalein (PSP) orally 2-3 h before the scheduled time of surgery as a marker dye to assess gastric emptying. Immediately after receiving PSP they were given: group A--liquids, up to 5 ml/kg + placebo (glucose water 0.2 ml/kg); group B--liquids, up to 5 ml/kg + ranitidine 2 mg/kg in glucose water 0.2 ml/kg; group C--placebo only; group D--ranitidine only. ⋯ PSP could not be detected in the gastric samples from children in whom the ingestion-sampling interval was more than 2.25 h. In comparison with prolonged starvation, administration of oral liquids without ranitidine 2-3 h preoperatively did not produce a significant increase in mean volume of gastric aspirate, and there was no increase in the number of patients with gastric aspirate greater than 0.4 ml/kg. Administration of ranitidine with or without fluids resulted in a decrease in both volume and acidity of gastric contents.
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Randomized Controlled Trial Comparative Study Clinical Trial
A randomized, double-blind comparison of the effects of interpleural bupivacaine and saline on morphine requirements and pulmonary function after cholecystectomy.
The effect of interpleural bupivacaine and saline placebo on morphine requirements and pulmonary function after cholecystectomy was investigated. Twenty-six patients were randomly assigned on postoperative day 1 to receive either 20 ml preservative-free saline (group 1) or 20 ml 0.5% bupivacaine with epinephrine, 5 micrograms/ml (group 2) through an interpleural catheter. Adequacy of pain relief was determined by the amount of morphine used by the patient following interpleural injection. ⋯ Mean PCA use in group 2 was 0.52 +/- 0.2 mg/h (73% reduction vs. control) for the third hour after bupivacaine (P less than 0.05). At the fourth and fifth hours after bupivacaine injection, mean PCA morphine use was not significantly different from that in group 1. FVC and FEV1 did not improve after interpleural saline.(ABSTRACT TRUNCATED AT 250 WORDS)
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Comparative Study
Pressure and flow limitations of anesthesia ventilators.
The effect of increasing airway pressure on the mean inspiratory flow and maximum minute ventilation (VE) capabilities of five anesthesia ventilators (Ohio Anesthesia, Airshields Ventimeter, Ohmeda 7000, Draeger AV-E and Siemens 900D) was compared to identify mechanical factor(s) limiting intraoperative ventilation of the lungs of patients with acute respiratory failure. The effect of increasing airway pressure on mean inspiratory flow was determined by cycling each ventilator through increasing restrictors. Maximum VE was measured under three study conditions using a test lung: 1) low compliance (10-30 ml/cmH2O) and minimal airflow resistance; 2) positive end-expiratory pressure (PEEP) of 0, 10, and 20 cmH2O at a compliance of 20 ml/cmH2O with minimal airflow resistance; and 3) increased resistance (19 +/- 11 cmH2O.1(-1).s-1) and compliance of 30 ml/cmH2O. ⋯ Thus, mean inspiratory flow of conventional anesthesia ventilators decreases with increasing airway pressure. The decreased inspiratory flow limits maximum VE when airway pressure is elevated because of decreased lung-thorax compliance and/or increased airway resistance, such as that characterizing patients with acute respiratory failure. Significant airway resistance further limits maximum VE by limiting the maximal T1/TTOT that can be used without increasing end-expiratory lung pressure.(ABSTRACT TRUNCATED AT 250 WORDS)
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Comparative Study
Clinical recovery and train-of-four ratio measured mechanically and electromyographically following atracurium.
Indices of clinical recovery were compared with mechanically (adductor pollicis muscle) and electromyographically (first dorsal interosseal muscle) recorded train-of-four (TOF) ratios during antagonism of atracurium blockade in 23 healthy neurolept anesthetized patients. Clinical recovery was evaluated from the ability to lift the head, sustain headlift for 5 or 10 s, protrude the tongue, open the eyes, and the presence of ptosis of the eyelids. In all patients the mechanical TOF ratio was recorded. ⋯ All patients could open the eyes and protrude the tongue at a TOF ratio of 0.65, and ptosis remained present during the entire testing period. There was no statistically significant difference between the mechanical and the EMG methods with regard to the TOF ratios at which the tests could be performed. During recovery a linear relationship was found between mechanical TOF ratios and the square root of the EMG TOF ratios.(ABSTRACT TRUNCATED AT 250 WORDS)