Anesthesia and analgesia
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Anesthesia and analgesia · Nov 2001
Randomized Controlled Trial Clinical TrialVoluntary hyperventilation before a rapid-sequence induction of anesthesia does not decrease postintubation PaCO2.
To prevent hypercapnia, voluntary hyperventilation is recommended for patients with increased intracranial pressure before the induction of general anesthesia. We sought to determine whether this maneuver results in a lower PaCO2 than breathing 3 min of oxygen 100% by face mask (preoxygenation) after intubation. Thirty patients requiring general anesthesia were randomly assigned to breathe either 3 min of oxygen 100% by face mask (Group P) or 1 min of oxygen 100% followed by 2 min of voluntary hyperventilation with oxygen 100% (Group H). All patients received a standard rapid-sequence induction of anesthesia followed by a 90-s period of apnea. Patients were then tracheally intubated and mechanically ventilated. Five arterial blood gas samples were taken: with room air, after preoxygenation or hyperventilation, after 60 and 90 s of apnea, and after tracheal intubation. Voluntary hyperventilation decreased PaCO2 before rapid-sequence induction (hyperventilation, 30.0 +/- 3.5 mm Hg versus preoxygenation, 37.9 +/- 5.2 mm Hg; P < 0.0001), but after 60 s of apnea, both groups had similar PaCO2 (hyperventilation, 36.1 +/- 3.3 mm Hg versus preoxygenation, 35.6 +/- 3.4 mm Hg; P = 0.673), and no benefit was found after intubation (hyperventilation, 40.5 +/- 3.9 mm Hg versus preoxygenation, 41.4 +/- 2.7 mm Hg; P = 0.603). We conclude that voluntary hyperventilation before rapid-sequence induction does not provide protection against potential hypercapnia during intubation. ⋯ Voluntary hyperventilation before anesthesia induction is recommended for patients with increased intracranial pressure to prevent hypercapnia. This randomized, prospective study demonstrated that this maneuver does not result in a lower postintubation PaCO2 than standard preoxygenation.
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Anesthesia and analgesia · Nov 2001
Randomized Controlled Trial Clinical TrialThe effect of noise on the bispectral index during propofol sedation.
Because noise in the operating room has been alleged to interfere with the ability to sedate patients before surgery, we evaluated the effect of noise on the Bispectral index (BIS) value during propofol sedation. Thirty unpremedicated patients were studied before the start of surgery while receiving propofol sedation on two separate occasions according to a randomized, crossover protocol design. After achieving a stable baseline BIS value of either 75 or 80 with a target-controlled infusion of propofol, an external sound source administered noise at 50, 80, 110, and 120 dB. The changes in the BIS value were recorded over a 1-min interval at each noise level. In the BIS 75 group, increasing levels of noise did not significantly alter the BIS value. However, in the BIS 80 group, the BIS values at 80, 110, and 120 dB were significantly higher compared to the value at 50 dB. In conclusion, experimental noise increases the BIS and appears to have a greater effect on the BIS value at "lighter" levels of propofol sedation. ⋯ Experimental noise levels can increase the Bispectral index (BIS) values during propofol sedation in the operating room. However, the magnitude of the BIS response is influenced by the depth of sedation.
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Anesthesia and analgesia · Nov 2001
Randomized Controlled Trial Clinical TrialPositive pressure ventilation with the ProSeal versus classic laryngeal mask airway: a randomized, crossover study of healthy female patients.
The ProSeal and classic laryngeal mask airways are equally effective ventilatory devices in healthy female patients at tidal volumes of 8 and 12 mL/kg with the cuff semi- or fully inflated, but leakage of small volumes of air from the mouth occurs more frequently with the laryngeal mask airway.
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Anesthesia and analgesia · Nov 2001
Randomized Controlled Trial Clinical TrialThe recovery profile of baroreflex control of heart rate after isoflurane or sevoflurane anesthesia in humans.
Volatile anesthetics attenuate baroreflex function in a concentration-dependent manner. This study was designed to determine how long full recovery of baroreflex control of heart rate takes after isoflurane or sevoflurane anesthesia in healthy volunteers. We assessed baroreflex sensitivity in 20 subjects randomized to receive either isoflurane or sevoflurane (n = 10 each). After an 8- to 10-h fast and no premedication, mea- surements of R-R intervals obtained from the electrocardiogram (lead II) and systolic blood pressure (SBP) measured through a radial artery catheter were made at conscious baseline and 20, 60, and 120 min after the induction during end-tidal isoflurane 1.3% or sevoflurane 2.0% in air and oxygen, and 20, 60, 120, and 180 min after the emergence from general anesthesia. Baroreflex responses were triggered by bolus IV injection of phenylephrine and nitroprusside to increase and decrease SBP by 15-30 mm Hg, respectively. The linear portions of the baroreflex curves relating R-R intervals and SBP were determined to obtain baroreflex sensitivity. During anesthesia, baroreflex sensitivities of both the pressor and depressor tests were decreased by 50%-60% compared with conscious baseline values in both groups (P <0.05). Pressor test sensitivities returned to the baseline values at 120 min, whereas depressor test sensitivities returned to the baseline values at 60 min, after general anesthesia in both groups. There were no significant differences in baroreflex sensitivities between groups at any interval. Our results indicate that the recovery characteristics of baroreflex sensitivity are similar after isoflurane and sevoflurane anesthesia and that the depressor test sensitivity is restored more rapidly than the pressor test sensitivity after both anesthetic techniques. ⋯ Arterial baroreflex function is an important neural control system for maintaining cardiovascular stability. The authors found that 2 h was required for full recovery of baroreflex function and that recovery characteristics were similar after isoflurane and sevoflurane anesthesia in healthy volunteers not undergoing surgery.
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Anesthesia and analgesia · Nov 2001
Clinical TrialThoracic epidural analgesia via the caudal approach in pediatric patients undergoing fundoplication using nerve stimulation guidance.
Epidural catheter placement using electrical stimulation guidance is an alternative approach for positioning the catheter into the thoracic region via the caudal space. This easily performed clinical assessment provides optimization of catheter tip positioning for achieving effective pain control.