Minimum alveolar concentration of desflurane in patients older than 65 yr.

BACKGROUND: The minimum alveolar concentration (MAC) of desflurane/oxygen is 7.25% in the 18-30-yr age group, and 6.0% in the 31-65-yr age group. The addition of 60% N2O reduces MAC to 4.0 and 2.83%, respectively. Because MAC of other inhaled anesthetics is less than that for younger adults, we determined MAC of desflurane in adults aged 65 yr and older. METHODS: Thirty-nine patients, 21 of whom received 60% N2O/O2/desflurane, and 18 of whom received desflurane/oxygen, scheduled for surgery, were enrolled. They received no premedication, intravenous induction agent, opioid, or neuromuscular blocking agent for intubation. After 10 min or more at a steady end-tidal desflurane concentration, the incision was made. In both groups, six crossover pairs of patients responses (movement-no movement) provided a mean end-tidal concentration. Minimum alveolar concentration was defined as the average of the six crossover midpoints in each subgroup. RESULTS: MAC was 5.17 +/ 0.6% (mean +/- SD) in the desflurane/oxygen group. It was 1.67 +/- 0.4% in the desflurane/nitrous oxide/oxygen group. CONCLUSIONS: In the geriatric patient, MAC of desflurane, with or without nitrous oxide, is less than that reported in patients aged 18-65 yr. This is in agreement with results with all other inhalation agents.

The esophageal detector device. Does it work?

BACKGROUND: The esophageal detector device (EDD) is a diagnostic tool for confirmation of tracheal intubation. Capnography is the accepted standard for such confirmation. The purpose of this investigation was to determine whether results using the EDD and capnography agree. METHODS: Five hundred patients were divided into three separate studies. In study 1, with 300 consecutive patients, tracheal intubation was performed and tested with the EDD followed by capnography. In study 2, 100 patients had the esophagus intentionally intubated, and confirmation was tested similarly. The tube was then removed and the trachea intubated, and testing followed. Study 3 involved 100 patients and used a double-blind, randomized design. The tube was intentionally inserted into either the esophagus (n = 5) or trachea (n = 49), and testing followed. RESULTS: In study 1, the compressed EDD bulb reinflated 270 times and always agreed with capnography; in 20 of the 270 subjects (7%) bulb reinflation was delayed, taking from 5-30 s. In 30 instances, the bulb remained compressed, and there was no capnogram indicating esophageal intubation. In study 2, regardless of esophageal or tracheal intubation, agreement between EDD and capnogram was 100%. In study 3, the agreement between the two detecting instruments was 100%, but reinflation of the EDD bulb was delayed in 4% of tracheal intubations. In the 500 patients studied, results from the EDD and capnogram always agreed, but in 6% of all tracheal intubations, the EDD bulb inflated slowly. Of 181 esophageal intubations, the results from the EDD and capnogram always agreed, i.e., there was no reinflation or capnogram. The sensitivity, specificity, and predictive value for the EDD in all of these studies was 100%. CONCLUSIONS: The EDD is a valuable diagnostic technique for confirming tracheal intubation. Results using EDD agree with results using capnography; in 6% of instances there is a slow reinflation; and where there is no capnography, such as on hospital wards, EDD may be a useful diagnostic tool.

Desflurane versus isoflurane in patients with chronic hepatic and renal disease.

Forty patients with chronic hepatic (n = 20) and renal (n = 20) disease were studied randomly for the purpose of evaluating safety and laboratory values. These included alanine and aspartate aminotransferases, alkaline phosphatase, total bilirubin, creatinine, and blood urea nitrogen. Patients with hepatic disease received either desflurane (n = 9) or isoflurane (n = 11) and patients with renal disease received the two anesthetics in equal subsets. In the patients with hepatic and renal disease, there were no differences in laboratory values (P < 0.05). We conclude that, in patients with either hepatic or renal disease, laboratory values from pre- to postoperative state did not change significantly within 24 h of anesthesia, and no differences in these changes existed between desflurane or isoflurane.