Anesthesia and analgesia
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Anesthesia and analgesia · Jun 1998
Esophageal stethoscope placement depth: its effect on heart and lung sound monitoring during general anesthesia.
Although the esophageal stethoscope has been used for many years, the effect of the depth of placement on the quality of the sounds obtained has never been investigated. The amplitude and frequency characteristics of the first and second heart sound and of inspiratory and expiratory breath sounds were determined at various stethoscope depths (from the distal tip) in 17 healthy anesthetized adults. The amplitude for each type of sound varied markedly with depth. Maximal amplitude for S1 was at 34 +/- 3 cm, for S2 at 27 +/- 2 cm, for inspiratory breath sound at 28 +/- 2 cm, and for expiratory breath sound at 26 +/- 2 cm. There was a positive linear correlation between the depth of maximal amplitude of these sounds and patient height. Peak frequency, in general, did not change with depth. We conclude that investigators should measure and document depth when performing studies involving the esophageal stethoscope. ⋯ Analysis of sound from the esophageal stethoscope at various depths reveals that placement depth greatly affects the sounds. A depth of 28-32 cm is recommended for clinical use; S1, S2, and inspiratory and expiratory sounds have a high amplitude in that range.
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Anesthesia and analgesia · Jun 1998
Randomized Controlled Trial Comparative Study Clinical TrialAnalgesic and cognitive effects of intravenous ketamine-alfentanil combinations versus either drug alone after intradermal capsaicin in normal subjects.
Combinations of opioids and N-methyl-D-aspartate (NMDA) antagonists enhance acute antinociception and reduce opioid tolerance in some animal experiments but have received little rigorous study in humans. To quantitatively assess the nature of the interaction of these two classes of drugs in producing analgesia and cognitive impairment, we compared i.v. infusions of ketamine, alfentanil, and ketamine-alfentanil combinations in 12 normal volunteers after an intradermal injection of capsaicin. Drug doses for a 70-kg subject in this six-session, randomized, double-blind, cross-over study were: ketamine 20 mg, ketamine 5 mg, alfentanil 2 mg, alfentanil 0.5 mg, ketamine 10 mg + alfentanil 1 mg, and ketamine 2.5 mg + alfentanil 0.25 mg, given over 35 min. Outcome measures were background pain, area and magnitude of hyperalgesia to pinprick, and cognitive performance on the Digit Symbol Substitution Test and the Perception Speed Test. The results demonstrated simple additivity for the effects of ketamine and alfentanil on pain, pinprick hyperalgesia, and cognitive impairment. We conclude that, at least in this experimental pain model, there is no clear advantage or disadvantage of a ketamine-alfentanil combination over equianalgesic doses of either component. ⋯ In a double-blind, controlled trial, we administered doses of an opioid analgesic (alfentanil), an N-methyl-D-aspartate receptor antagonist (ketamine), or their combination to normal volunteers and found no advantage of the combination over a larger dose of either drug alone in relieving pain caused by painful chemical stimulation.