Anesthesia and analgesia
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Anesthesia and analgesia · Oct 1992
Comparative StudyBuccal pulse oximeter is more accurate than finger pulse oximeter in measuring oxygen saturation.
Although there have been several anecdotal reports of the use of buccal pulse oximeter monitoring (Spo2) when digital Spo2 monitoring cannot be used, there have been no objective evaluations of the accuracy of buccal Spo2 monitoring. The purpose of this study was to systematically compare buccal Spo2 monitoring to both digital Spo2 and arterial O2 saturation monitoring (Sao2) in both generally anesthetized patients in the operating room (n = 31) and critically ill patients in the intensive care unit (n = 23). Buccal Spo2 probes were prepared by taping a malleable metal bar securely over the back of a Nellcor Oxisensor D-25 probe and bending the metal bar and buccal probe firmly around the corner of the patient's mouth. ⋯ We found that buccal Spo2 was higher than finger Spo2 and agreed more closely with Sao2 for both patient groups (98.1% +/- 2.6%, 96.8% +/- 3.5%, 98.5% +/- 2.5%, respectively [mean +/- SD]). The operating room patients had higher buccal and finger Spo2 and Sao2 (99.3% +/- 1.5%, 98.9% +/- 1.4%, 99.5% +/- 0.7%, respectively) than the intensive care unit patients (96.4% +/- 2.9%, 94.1% +/- 3.5%, 96.6% +/- 3.5%, respectively). Although buccal Spo2 monitoring has several disadvantages (i.e., the probe requires preparation, can be more difficult to place, may be less readily accepted in awake patients, and is often mechanically dislodged during airway maneuvers), we conclude that buccal Spo2 monitoring is a more than adequate oximetry alternative when digital Spo2 monitoring is not an option (digits are unavailable or available digits are mechanically interfered with).
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Anesthesia and analgesia · Oct 1992
ReviewCharacteristics and implications of desflurane metabolism and toxicity.
The metabolism of desflurane has been assessed both in animals and humans by measuring the appearance of fluoride metabolites (fluoride ion, nonvolatile organic fluoride, trifluoroacetic acid) in blood and urine. Desflurane administered to rats (either pretreated or not pretreated with phenobarbital or ethanol) for 3.2 MAC-hours and to swine for 5.5 MAC-hours produced fluoride ion levels in blood that were almost indistinguishable from values measured in control animals. In contrast, a significant 17% increase in plasma fluoride ion concentration in swine was detected 4 h after exposure to desflurane. ⋯ Peak serum concentrations averaging 0.38 +/- 0.17 microM trifluoroacetic acid (mean +/- SD) and peak urinary excretion rates averaging 0.169 +/- 0.107 mumol/h were detected in volunteers 24 h after desflurane exposure. Although these increases in trifluoroacetic acid after exposure to desflurane were statistically significant, they are approximately 10-fold less than levels seen after exposure to isoflurane. Desflurane strongly resists biodegradation, and only a small amount is metabolized in animals and humans.
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Anesthesia and analgesia · Oct 1992
Aspects of mechanical ventilation affecting interatrial shunt flow during general anesthesia.
Intraoperative transesophageal echocardiography was used to study the incidence of flow-patent foramen ovale in 33 normal, healthy patients (ASA physical status I) undergoing general anesthesia in the supine position for nonthoracic surgical procedures. Echocardiographic contrast was injected intravenously during mechanical ventilation in the presence of 0, 5, 10, 15, or 19 cm H2O positive end-expiratory pressure (PEEP). A final test was performed during the release of 19 cm H2O PEEP. ⋯ In all three cases, the shunt flow was accentuated on the release of PEEP; however, no additional cases were detected using this respiratory maneuver. These cases represent the first demonstration of right-to-left interatrial shunting evoked as the result of the sustained application of PEEP. This study also revealed a lower than expected incidence of flow-patent foramen ovale (9%) when measured during general anesthesia and positive pressure ventilation with or without PEEP.