Anesthesia and analgesia
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Anesthesia and analgesia · Jan 1999
Randomized Controlled Trial Clinical TrialThe effects on resting ventilation of intravenous infusions of morphine or sameridine, a novel molecule with both local anesthetic and opioid properties.
Sameridine has both local anesthetic and partial mu-opioid receptor agonistic properties. The aim of this single-blinded, randomized, three-way cross-over study of 12 subjects was to investigate the effects on resting ventilation of two doses of sameridine: 0.15 mg/kg (S-Small) and 0.73 mg/kg (S-Large) compared with 0.10 mg/kg morphine. Each drug was infused IV over 20 min. Ventilation was measured by pneumotachography and in-line capnography, and sedation was rated by the subjects using a visual analog scale (VAS). Plasma was collected and analyzed for sameridine and morphine. At the end of drug infusion, minute ventilation (VE) and tidal volume (VT) were reduced in the S-Large group, and VE was reduced in the morphine group. End-tidal CO2 increased in both groups (P < 0.05), but respiratory rates remained unchanged. In the S-Small group, no ventilatory changes were recorded. In the S-Large group, the median sedation score was 6.8 cm with corresponding values in the morphine and S-Small groups of 3.3 and 2.5 cm, respectively. There was a relationship between the plasma concentration of sameridine and the depression of ventilation. We conclude that sameridine influences resting ventilation and that this effect is directly related to plasma concentrations of sameridine. From a ventilatory aspect, a clinical dose of sameridine with both local anesthetic and opioid properties seems safe. ⋯ Sameridine, a molecule with both local anesthetic and analgesic properties, impaired resting ventilation after a large IV dose (0.73 mg/kg), more so than 0.10 mg/kg IV morphine. A clinical dose of sameridine (0.15 mg/kg) did not have any effects on ventilation.
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Anesthesia and analgesia · Jan 1999
Randomized Controlled Trial Comparative Study Clinical TrialFiberoptic-guided airway exchange of the esophageal-tracheal Combitube in spontaneously breathing versus mechanically ventilated patients.
The aim of this study was to compare fiberoptic-guided airway exchange of the esophageal-tracheal Combitube (ETC, Kendall-Sheridan Catheter Corp., Argyle, NY) with an endotracheal tube in spontaneously breathing versus mechanically ventilated patients. Forty patients with Mallampati score III and IV scheduled for elective surgery were randomly allocated into two groups (n = 20 each): nonparalyzed, spontaneously breathing or paralyzed, mechanically ventilated patients. After anesthetic induction and insertion of the ETC, a fiberoptic bronchoscope threaded into an armored endotracheal tube was passed transnasally into the larynx. Endotracheal intubation was successful in 18 spontaneously breathing patients and in 15 patients during controlled ventilation. Successful airway exchange was completed in significantly less time (P < 0.05) in spontaneously breathing patients (9+/-3 min; mean +/- SD) than in mechanically ventilated patients (13+/-4 min). Both methods allowed for continuous airway control and maintenance of ventilation and oxygenation. The described method is a means of replacing the ETC with an endotracheal tube without interruption of airway control or ventilation. Replacing the ETC with an endotracheal tube using this method is more readily accomplished during spontaneous ventilation than during controlled ventilation. ⋯ We describe the replacement of the Combitube by an endotracheal tube by the aid of fiberoptic bronchoscopy and without interruption of airway control or ventilation. The performance of this technique was facilitated by spontaneous ventilation compared with mechanical ventilation.
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Anesthesia and analgesia · Jan 1999
Randomized Controlled Trial Clinical TrialConcentration of lidocaine affects intensity of sensory block during lumbar epidural anesthesia.
We investigated the effects of a twofold difference in concentration and volume of lidocaine on lumbar epidural block using a cutaneous current perception threshold (CPT) quantitative sensory testing device. Twenty ASA I patients scheduled for elective gynecological surgery were randomly divided into two equal groups to receive either 20 mL of 1% lidocaine or 10 mL of 2% lidocaine through an epidural catheter inserted at the L1-2 interspace. CPTs at 2000-, 250-, and 5-Hz stimulation and sensation to light touch, temperature, and pinprick at ipsilateral dermatomes V, T9, and L2 were measured before and every 5 min until 60 min after the epidural lidocaine. Epidural anesthesia with both solutions produced a significant increase in all CPTs at dermatomes T9 and L2. Alterations in CPTs were similar for both groups at T9 but were significantly greater in patients given 2% lidocaine than in those given 1% lidocaine at L2. There were no differences in the upper level of sensory block to cold, pinprick, and touch between the two groups. We conclude that lumbar epidural anesthesia with 10 mL of 2% lidocaine produces more intense blockade of both large- and small-diameter sensory nerve fibers than that with 20 mL of 1% lidocaine. ⋯ The effects of local anesthetic concentration and volume on the quality of epidural anesthesia have not been adequately investigated. The results of the present study suggest that the concentration affects the intensity of sensory block during epidural anesthesia with lidocaine.
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Anesthesia and analgesia · Jan 1999
Comparative Study Clinical TrialEvaluation of a new operating room ventilator with volume-controlled ventilation: the Ohmeda 7900.
Changes in fresh gas flow (FGF) during volume-controlled ventilation with the circle system have clinically important effects on the ventilatory variables of children. Current operating room ventilators allow a portion of the FGF to be added to the delivered tidal volume. The Ohmeda 7900 (Madison, WI) ventilator was designed to compensate for changes in FGF. We compared this ventilator with a standard ventilator, the Ohmeda 7000. Twenty patients (13-56 kg) undergoing dental or lower extremity surgery were studied. A side-by-side comparison of the two ventilators was performed using each patient as his or her own control. Beginning with the 7900 ventilator, FGF was set at 3.0 L/min, and the inspiratory to expiratory ratio was set at 1:2. Respiratory rate and tidal volume were adjusted to achieve an ETCO2 of 30-40 mm Hg. After a 10-min period of stabilization, inspired minute ventilation (VI), expired minute ventilation (VE), and ETCO2 were measured. FGF was then increased to 6.0 L/min, and the measurements were repeated after 10 min; FGF was then decreased to 1.5 L/min, and measurements were repeated after 10 min. The patient was then ventilated with an Ohmeda 7000 ventilator, and the sequence was repeated. The Ohmeda 7000 ventilator demonstrated significant changes in VI, VE, plateau pressure, and ETCO2, with changes in FGF (P = 0.0039-0.0001). The Ohmeda 7900 ventilator demonstrated compensation for changes in FGF; there were no significant changes in VI, VE, and ETCO2. We conclude that the Ohmeda 7900 ventilator provides stable ventilatory variables regardless of alterations in FGF (1.5-6.0 L/min). ⋯ In this study, we compared the effects of changing fresh gas flow on volume-controlled ventilation using two operating room ventilators (Ohmeda 7000 and Ohmeda 7900). The Ohmeda 7900, but not the Ohmeda 7000, provided stable ventilatory variables with fresh gas flows between 1.5 and 6.0 L/min.
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Anesthesia and analgesia · Jan 1999
Clinical TrialCapnography monitoring during neurosurgery: reliability in relation to various intraoperative positions.
In neurosurgery, estimation of PaCO2 from PETCO2 has been questioned. The aim of this study was to reevaluate the accuracy of PETCO2 in estimating PaCO2 during neurosurgical procedures lasting >3 h and to measure the effect of surgical positioning on arterial to end-tidal CO2 gradient (P[a-ET]CO2) over time. One hundred four neurosurgical patients classified into four groups (supine [SP], lateral [LT], prone [PR], sitting [ST]) were included in a prospective study. PaCO2, PETCO2, and P(a-ET)CO2 were measured after induction of anesthesia (T0), after positioning (T1), each following hour (T2, T3, T4), and at the end of the procedure after return to the SP position (T5). Data are expressed as the mean +/- SD, and statistical analysis used linear regression, the Bland-Altman method, and analysis of variance. The mean durations of positioning and surgery were 4.1+/-1 h and 3.7+/-1.3 h, respectively. We performed 624 simultaneous measurements of PaCO2 (33+/-5 mm Hg) and PETCO2 (27+/-4 mm Hg), leading to a mean P(a-ET)CO2 of 6+/-4 mm Hg. P(a-ET)CO2 of the LT group (7+/-3 mm Hg) was larger (compared with the SP, PR, and ST groups) because of a lower PETCO2 (26+/-4 mm Hg). Negative P(a-ET)CO2 (PETCO2 > PaCO2) occurred 22 times, only in the SP (n = 9) and ST groups (n = 13). Changes in opposite directions of PETCO2 and PaCO2 between two successive measurements were found in 26% of the cases. Correlation coefficients in the four groups (PaCO2 versus PETCO2) were not in good agreement (0.46 to 0.62; P < 0.001). The mean bias was between 5 and 7 mm Hg. The superior (13-15 mm Hg) and inferior (-5 to 0 mm Hg) limits of agreement were too large to expect PETCO2 to replace PaCO2. In conclusion, during neurosurgical procedures of >3 h, capnography should be performed with regular analysis of arterial blood gases for optimal ventilator adjustment. ⋯ This study, which aimed to reevaluate the ability of PETCO2 to estimate PaCO2 during neurosurgical procedures according to surgical position, indicates that PETCO2 cannot replace PaCO2 for the following reasons: scattering of individual values; occurrence of negative arterial to end-tidal CO2 gradient (P[a-ET]CO2; PaCO2 and PETCO2 variations in opposite directions; large changes in P(a-ET)CO2 between two samples; and instability of P(a-ET)CO2 over time.