Anesthesiology
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Comparative Study
Differences between aortic and radial artery pressure associated with cardiopulmonary bypass.
Previous investigators have identified an aortic-to-radial artery pressure gradient thought to develop during rewarming and discontinuation of cardiopulmonary bypass. The authors measured mean aortic and radial artery pressures before, during, and after cardiopulmonary bypass in 30 patients, to determine when the pressure gradient develops. The pressure gradient was also measured before and after intravenous injections of sodium nitroprusside (1 microgram/kg) and phenylephrine (7 micrograms/kg) to determine the effect of changes in systemic vascular resistance. ⋯ Sodium nitroprusside significantly decreased systemic vascular resistance, by 15 +/- 2%, during the middle of bypass but did not affect the pressure gradient. Likewise, phenylephrine increased the systemic vascular resistance by 52 +/- 6% and 34 +/- 4% during the middle of bypass and rewarming, respectively, without affecting the pressure gradient. Although the exact mechanisms responsible for the pressure gradient remain unknown, these results suggest its etiology is associated with events occurring during initiation of cardiopulmonary bypass rather than with rewarming or discontinuation of cardiopulmonary bypass.
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Randomized Controlled Trial Clinical Trial
Fifty percent nitrous oxide does not increase the risk of venous air embolism in neurosurgical patients operated upon in the sitting position.
Although nitrous oxide (N2O) should theoretically increase the severity of venous air embolism (VAE), data confirming this hazard in clinical situations are not available. The effect of 50% N2O on the incidence and severity of VAE and on the emergence time from anesthesia was evaluated in 300 neurosurgical patients operated upon while in the sitting position. Of these, 110 patients underwent craniectomy for posterior fossa pathology and 190 patients underwent cervical spine surgery (CSS). ⋯ Emergence time was significantly longer in the craniectomy group than in the CSS group (5 vs. 1 min, respectively; P less than 0.001). Within the craniectomy group, the incidence of Doppler-detected VAE was significantly less in patients with previous surgery at the operative site (21%) compared to patients without previous surgery at the operative site (47%). Postoperatively, no complications could be related to the use of N2O or directly attributed to the occurrence of VAE.(ABSTRACT TRUNCATED AT 400 WORDS)
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Randomized Controlled Trial Clinical Trial
The influence of atropine dose on recovery from vecuronium-induced neuromuscular blockade.
To determine whether the dose of atropine affects the rate of neostigmine-induced recovery from vecuronium-induced neuromuscular blockade, the authors monitored isometric adductor pollicis mechanical activity in 36 anesthetized (thiopental, fentanyl, nitrous oxide) adult patients (ASA physical status 1 or 2). Once surgery was completed and twitch height had spontaneously regained 25% of its initial value, the patients were randomly allocated into three groups (A10, A15, A20; n = 12 in each group) according to the dose of atropine (10, 15, or 20 micrograms/kg) that was mixed with 40 micrograms/kg neostigmine. Twitch height, train-of-four, and 50- and 100-Hz tetanic fade were recorded for 15 min after the administration of the reversal agents. ⋯ Fifteen minutes after reversal, fade in response to 100-Hz tetanus was statistically greater in the A10 group than in the two other groups (70% +/- 3% of control versus 84% +/- 4% and 81% +/- 2%) (mean +/- SEM, P less than 0.05). The present results demonstrate that larger doses of atropine facilitate neostigmine's reversal of vecuronium neuromuscular blockade. The clinical implications of the differences observed in this study remain to be determined.
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Detection and hemodynamic consequences of venous air embolism. Does nitrous oxide make a difference?
Volume expansion of intravascular air by nitrous oxide (N2O) may improve the sensitivity of monitors used to detect venous air embolism (VAE) and/or exacerbate hemodynamic changes following VAE. The purpose of this study was to determine if the administration of N2O alters the sensitivity (i.e., threshold of detection) of monitors used to detect VAE or the hemodynamic consequences of VAE. Twenty-one dogs were monitored for VAE with precordial Doppler ultrasound, transesophageal echocardiography (TEE), changes in end-tidal carbon dioxide tension (ETCO2), and changes in pulmonary artery pressure (PAP). ⋯ Positive responses were defined as follows: unmistakable audible change in frequency on Doppler ultrasound, visualization of densities consistent with air bubbles in the right cardiac chambers or outflow tract on TEE, a decrease in ETCO2 greater than or equal to 2 mmHg, and an increase in mean PAP greater than or equal to 3 mmHg. In group 3 (n = 7), venous air was infused at rates between 0.1 and 0.8 ml.kg-1.min-1 during 1 MAC (total anesthetic level) of isoflurane with and without 50% N2O. In group 3, N2O administration was discontinued immediately upon Doppler detection of VAE and air infusion continued until mean arterial pressure (MAP) decreased by 10 mmHg.(ABSTRACT TRUNCATED AT 250 WORDS)
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Comparative Study
The risk of myocardial ischemia in patients receiving desflurane versus sufentanil anesthesia for coronary artery bypass graft surgery. The S.P.I. Research Group.
Desflurane, a coronary vasodilator, may induce myocardial ischemia in patients with coronary artery disease. To determine whether desflurane is safe to administer to the at-risk patient population (with known coronary artery disease), we compared the incidence and characteristics of perioperative myocardial ischemia in 200 patients undergoing coronary artery bypass graft (CABG) surgery randomly assigned to receive desflurane (thiopental adjuvant) versus sufentanil anesthesia. Under conditions of hemodynamic control, perioperative ischemia was assessed using continuous echocardiography (precordial: during induction; transesophageal: during surgery) and Holter electrocardiography (ECG); hemodynamics (including pulmonary artery pressure) were measured continuously. ⋯ Echocardiographic results: The incidence of precordial echocardiographic ischemia during anesthetic induction was 13% (5/39) in the desflurane group versus 0% (0/29) in the sufentanil group (P = 0.1). Moderate to severe transesophageal echocardiographic (TEE) ischemic episodes occurred in 12% (21/175) of patients during prebypass, with no significant difference between the desflurane group, 16% (15/91) and the sufentanil group, 7% (6/84) (P = 0.09). TEE ischemic episodes occurred in 27% (49/178) of patients during the postbypass period, with no difference between the desflurane, 29% (27/92) and sufentanil, 25% (22/86) groups (P = 0.7).(ABSTRACT TRUNCATED AT 400 WORDS)