Anesthesia and analgesia
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Anesthesia and analgesia · Jul 1999
Randomized Controlled Trial Comparative Study Clinical TrialQuality of emergence from anesthesia and incidence of vomiting with remifentanil in a pediatric population.
We conducted a randomized trial to compare the incidence of vomiting and the quality of emergence from anesthesia associated with the use of remifentanil versus a nonopiate. It was expected that remifentanil would provide smoother emergence from anesthesia with a comparably low rate of vomiting. The study sample consisted of 115 pediatric patients undergoing dental restoration and extraction who were randomly assigned to the nonopiate or remifentanil groups based on their hospital admission numbers. The nonopiate patients received sufficient desflurane to prevent movement, typically 7%-9%. The remifentanil group received remifentanil 0.2 microg x kg(-1) x min(-1) and enough desflurane to prevent movement, typically 3.2%-3.6%. A trained postanesthesia care unit nurse, blinded to the anesthetic technique, assessed the quality of emergence and incidence of vomiting. Sixty-three patients received remifentanil and 52 received the nonopiate. The groups were not significantly different in either quality of emergence or incidence of vomiting. Remifentanil provided results comparable to a nonopiate with no increase in emesis. ⋯ A randomized, controlled clinical trial of 115 patients undergoing dental restoration indicated that an anesthetic technique using remifentanil provided quality of emergence comparable to and no greater incidence of vomiting than a nonopiate technique.
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Anesthesia and analgesia · Jul 1999
Randomized Controlled Trial Clinical TrialNitrous oxide increases endotracheal cuff pressure and the incidence of tracheal lesions in anesthetized patients.
The pressure in air-filled endotracheal cuffs increases steadily throughout general anesthesia with nitrous oxide (N2O). High cuff pressures can be responsible for local ischemia, which may induce tracheal mucosal injury. In this study, cuff pressure was monitored in anesthetized patients, and postanesthesia endotracheal lesions were assessed by endoscopy. Sixty-five patients undergoing general anesthesia with tracheal intubation >1 h in duration were randomized into two groups. The endotracheal tube cuff was inflated to 30-40 cm H2O with air in Group 1 (n = 33) and with a gas mixture (N2O 50% in oxygen) in Group 2 (n = 32). At the time of tracheal extubation, a fiberoptic examination via the endotracheal tube was performed by an independent observer. Aspects of trachea at the level of cuff contact area were scored as 0 = normal, 1 = mucosal erythema or edema, 2 = mucosal erosion or hemorrhage, 3 = mucosal erosion or hemorrhage on both anterior and posterior tracheal walls. Cuff pressure increased throughout the procedure (P<0.01) in Group 1 and remained stable in Group 2. In Group 1, tracheal lesions in the area of the cuff were more frequent than they were in Group 2 (79% vs. 37%; P<0.001). Tracheal injury was correlated to cuff pressure (r = 0.62, P<0.001). No postoperative respiratory complication was observed in any patient. In patients anesthetized with N2O, the inflation of the tracheal tube cuff with a gas mixture of the same composition as the inhaled mixture can prevent excessive cuff pressure and reduce the incidence of tracheal injury. ⋯ In patients anesthetized with nitrous oxide, the inflation of the tracheal tube cuff with a gas mixture of the same composition as the inhaled mixture can prevent excessive cuff pressure and reduce the incidence of tracheal injury.
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Anesthesia and analgesia · Jul 1999
Randomized Controlled Trial Clinical TrialPropofol anesthesia enhances pressor response to ephedrine in patients given clonidine.
We studied the hemodynamic effects of ephedrine in patients with or without clonidine premedication during either isoflurane or propofol anesthesia. Forty adult patients were randomly assigned to one of two groups: 20 patients received famotidine 20 mg orally (control group) and 20 received clonidine 3 microg/kg and famotidine 20 mg orally (clonidine group). Within each group, 10 patients were then anesthetized with isoflurane and 10 with propofol. Hemodynamic measurements were taken at 1-min intervals for 10 min after a bolus injection of ephedrine 0.1 mg/kg. The magnitude of the maximal pressor response to ephedrine was no different whether patients without clonidine were anesthetized with isoflurane (increase 5+/-7 mm Hg) or propofol (3+/-9 mm Hg); however, this response was greater (P<0.05) with propofol (17+/-6 mm Hg) versus isoflurane (6+/-5 mm Hg) in patients given clonidine. The arterial blood pressure increase in clonidine-premedicated patients with propofol anesthesia was the largest among the four subgroups. The heart rate response to ephedrine was not significant in patients anesthetized with isoflurane and was small but significant in those anesthetized with propofol. The present results, together with previous studies on the effect of ephedrine in patients medicated with clonidine, suggest that the interaction between clonidine and ephedrine is modulated by the anesthetic used. ⋯ We evaluated the pressor response to ephedrine during isoflurane or propofol anesthesia with or without clonidine premedication. Our study suggests that, in anesthetized patients premedicated with clonidine, decreases in blood pressure may be easier to reverse with ephedrine with some types of anesthesia (e.g., propofol) than with others (e.g., isoflurane).
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Anesthesia and analgesia · Jul 1999
Randomized Controlled Trial Clinical TrialA controlled study of transesophageal echocardiography to guide central venous catheter placement in congenital heart surgery patients.
Transesophageal echocardiography (TEE) and central venous catheter (CVC) placement are often used during congenital cardiac surgery. Complications of CVC placement include cardiac perforation, inadvertent arterial placement, and erroneous hemodynamic data from unrecognized malposition. In this study, we used a prospective, randomized, controlled design to evaluate the use of TEE to guide depth of insertion and confirm superior vena cava cannulation, and to improve the percentage of correctly placed CVCs and reduce complications of CVC placement. One hundred forty-five patients were studied. Eighty patients were randomized to have subclavian vein insertion, 64 to have internal jugular insertion, and 1 to have external jugular insertion of CVC. TEE-guided CVC placement resulted in 100% correct placement when assessed by preoperative TEE, versus 86% in the control group (72 of 72 vs. 63 of 73; P = 0.01). There was no difference in correct placement between the two groups when assessed by postoperative chest radiograph (81.9% TEE versus 75.3% control; P = not significant). One significant complication, a superior vena cava perforation, occurred in the control group. Time to placement was 9.6 min in the TEE group versus 8.0 min in the control group (P = 0.015). ⋯ Transesophageal echocardiography can be used to guide central venous catheter placement in congenital heart surgery. Central venous catheters that seem to be located high in the right atrium by chest radiograph in these patients are often actually in the superior vena cava and pose little risk of cardiac perforation.
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Anesthesia and analgesia · Jul 1999
The effects of nitrous oxide and oxygen on transient hyperemic response in human volunteers.
The aim of this study was to determine the effects of breathing 100% oxygen or 50% nitrous oxide in oxygen on the indices of cerebral autoregulation derived from the transient hyperemic response (THR) test in human volunteers. Data were analyzed from nine healthy subjects. Middle cerebral artery (MCA) blood flow velocity (FV) was measured by transcranial Doppler ultrasound, and the THR test was performed using 10-s compression of the common carotid artery. Continuous measurement of P(ETCO2) and expired fractions of oxygen (F(ETO2)) and nitrous oxide (F(ETN2O)) was established, and mean arterial pressure (MAP) was recorded at 2-min intervals. All measurements were performed while the volunteers were breathing room air and were repeated 10 min after achieving F(ETO2) >0.95 and 10 min after achieving F(ETN2O) 0.48-0.52. Two indices derived from the THR test, the transient hyperemic response ratio (THRR) and strength of autoregulation (SA), were used to assess cerebral autoregulation. P(ETCO2) and mean arterial pressure did not change significantly throughout the study period. Breathing 100% oxygen did not change MCA FV, THRR, or SA. Inhalation of nitrous oxide resulted in a marked and significant increase in the MCA FV (from 48+/-9 to 72+/-8 cm/s; mean +/- SD) and a significant decrease in the THRR (from 1.5+/-0.2 to 1.2+/-0.1) and the SA (from 1.0+/-0.1 to 0.8+/-0.1) (P<0.05 for all). We conclude that breathing 50% nitrous oxide in oxygen results in both a significant increase in MCA FV and impairment of transient hyperemic response. ⋯ Our study suggests that nitrous oxide impairs cerebral autoregulation and may have implications for its use in neurosurgical anesthesia and for interpretation of the results from studies of anesthetics in which nitrous oxide is used in the background.