Anesthesia and analgesia
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Anesthesia and analgesia · Sep 2002
Comparative StudyComparing methods of administering high-frequency jet ventilation in a model of laryngotracheal stenosis.
We administered high-frequency jet ventilation (HFJV) to a tracheal-lung model with connectors of internal diameter 2.5-8.5 mm to simulate ventilation through varying degrees of laryngotracheal stenosis. With reductions in diameter, end-expiratory pressure (EEP) and peak inspiratory pressure (PIP) increased. During supraglottic, translaryngeal, and transtracheal HFJV, respectively, EEP was > or =10 mm Hg at diameters narrower than 5.5, 4.0, and 3.5 cm, and PIP was >20 mm Hg at diameters narrower than 5.5, 3.5, and 3.0 cm. EEP and PIP were greater during supraglottic HFJV than during translaryngeal and transtracheal HFJV (P < 0.01). At diameters of <3.5 and 4.0 cm, respectively, PIP and EEP increased and were significantly greater (P < 0.01) during translaryngeal HFJV than during transtracheal HFJV. In a second experiment, the degree of ventilation and air entrainment was assessed by administering nitrous oxide 4 L/min to the model. Nitrous oxide concentrations were significantly (P < 0.01) smaller and nitrogen concentrations were significantly (P < 0.01) larger during supraglottic HFJV than either translaryngeal or transtracheal HFJV. The larger EEP and PIP associated with supraglottic HFJV may be attributable to increased ventilation and air entrainment compared with translaryngeal and transtracheal HFJV. ⋯ Ventilatory driving pressure during supraglottic high-frequency jet ventilation may be reduced to minimize high airway pressures and hence the potential for pulmonary barotrauma in patients with laryngotracheal stenosis.
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Anesthesia and analgesia · Sep 2002
Clinical TrialThe use of a uniquely designed anesthetic scavenging hood to reduce operating room anesthetic gas contamination during general anesthesia.
Numerous studies have suggested that chronic exposure to trace levels of anesthetic gas is harmful to operating room (OR) personnel. In the delivery of pediatric general anesthesia, an uncuffed endotracheal tube (ETT) is normally used which can result in considerable volatile anesthetic and nitrous oxide contamination of the OR. In this report, we present a method to reduce exposure to these anesthetic gases by means of an anesthetic scavenging hood (ASH). The ASH was used on six pediatric patients undergoing general endotracheal anesthesia via an uncuffed ETT. Measurements of all ambient gas levels were made 6 in. horizontally from the patient's ear and 6 in. from the table surface. The application of the vacuum source to the ASH resulted in a very significant (P < 0.01, paired t-test) decrease in levels of ambient anesthetic gas, with no measurable change in ventilatory variables or changes in body temperature (P > 0.05, paired t-test). Discontinuation of the vacuum force to the ASH resulted in a marked increase in ambient levels of anesthetic gas. We conclude that the ASH is extremely effective in reducing waste anesthetic gas associated with anesthesia administered via an uncuffed ETT. The ASH may be a valuable and cost-effective addition in the OR for both reducing ambient anesthetic waste gas levels and conserving patient heat. ⋯ Chronic exposure to trace levels of anesthetic gas is harmful to operating room personnel, especially in the delivery of pediatric general anesthesia via an uncuffed endotracheal tube. The anesthetic scavenging hood is a cost-effective and efficient method to reduce these waste anesthetic gases, and it offers patient heat conservation.
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We report a previously undescribed complication of peripheral nerve catheter placement. The catheter was sheared when its stylet was removed with the placement needle still in the tissues. The lost distal fragment was identified with computed tomography scanning.
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Anesthesia and analgesia · Sep 2002
Case ReportsUnsolicited paresthesias with nerve stimulator: case reports of four patients.
Unsolicited paresthesias may occur when a nerve stimulator is used and may indicate valid proximity to the nerve. This phenomenon suggests that nerve stimulator use does not protect against unplanned direct contact with peripheral nerves during performance of a nerve block on an obtunded patient.
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Anesthesia and analgesia · Sep 2002
The pharmacokinetics and tolerability of an intravenous infusion of the new hydroxyethyl starch 130/0.4 (6%, 500 mL) in mild-to-severe renal impairment.
Hydroxyethyl starches (HES) are almost exclusively excreted glomerularly, in part after hydrolysis by amylase. HES 130/0.4 (Voluven; Fresenius Kabi Deutschland GmbH, Bad Homburg, Germany) was developed to improve pharmacokinetics whereas preserving the efficacy of volume effect. We studied the dependency of pharmacokinetics of HES 130/0.4 on renal function. Nineteen volunteers with stable, non-anuric renal dysfunction, ranging from almost normal creatinine clearance (CL(cr)) to severe renal impairment (mean CL(cr): 50.6 mL. min(-1). 1.73 m(-2)), were given a single infusion of 500 mL 6% HES 130/0.4 over 30 min. HES plasma concentrations were determined until 72 h, urinary excretion until 72-96 h. CL(cr) had been obtained at least twice before and twice after dosing. Standard pharmacokinetic calculations and regression analysis were performed. Area under the time concentration curve (AUC(0-inf)) clearly depended on renal function comparing subjects with CL(cr) < 50 with those with CL(cr) > or =50 (ratio 1.73). Peak concentration (C(max), 4.34 mg/mL) as well as terminal half-life (16.1 h, model independent) were not affected by renal impairment. At CL(cr) > or =30, 59% of the drug could be retrieved in urine, versus 51% at CL(cr) 15-<30. The mean molecular weight of HES in plasma was 62,704 d at 30 min, showing lower values with increased renal impairment (P = 0.04). Pre-dose amylase concentrations inversely correlated with baseline CL(cr). Residual HES plasma concentrations after 24 h were small in all subjects (< or =0.6 mg/mL). We conclude that HES 130/0.4 (500 mL 6%) can be safely administered to patients even with severe renal impairment, as long as urine flow is preserved, without plasma accumulation. ⋯ Dependency of the pharmacokinetics of hydroxyethyl starch 130/0.4 on renal function was studied. The area under the time concentration curve increased moderately with more severe renal dysfunction; however, small plasma concentrations were observed after 24 h. Terminal half-life and peak concentration remained unaffected by renal impairment.