1 Department of Anesthesiology, 2 Department of Physiology and 3 Department of Pharmacology, Texas Tech University Health Sciences Center, Lubbock, Texas, USA
Corresponding author. E-mail: james.heavner@ttmc.ttuhsc.edu Declaration of interest: This lab has participated in several studies sponsored by Baxter Healthcare, the sponsor of the study reported in this manuscript. Dr Alan Kaye is a paid speaker on Baxters speakers bureau.
Accepted for publication: April 29, 2003
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Abstract |
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Methods. Fifty ASA physical status I, II, or III patients, 65 yr of age or older, undergoing anaesthesia expected to last two or more hours were randomly assigned to receive desflurane/nitrous oxide or sevoflurane/nitrous oxide anaesthesia. Patients were given 12 µg kg1 fentanyl i.v. and anaesthesia was induced with propofol 1.52.5 mg kg1 i.v. and maintained with either desflurane 26% or sevoflurane 0.61.75% with nitrous oxide 65% in oxygen. Inspired anaesthetic concentrations were adjusted to obtain adequate surgical anaesthesia and to maintain mean arterial pressure within 20% of baseline values. Early and intermediate recovery times were recorded. Digit-Symbol Substitution Test (DSST) scores and Visual Analog Scale (VAS) scores for pain and nausea were recorded before pre-medication and every 15 min in the Post Anaesthesia Care Unit (PACU) until patients were discharged.
Results. Early recovery times are given as median, quartiles. The times to extubation (5 (49); 9 (513) min), eye opening (5 (35); 11 (816) min), squeezing fingers on command (7 (49); 12 (817) min); and orientation (7 (59); 16 (1021) min) were significantly less (P<0.05) for desflurane than for sevoflurane. Intermediate recovery, as measured by the DSST and time to ready for discharge from the PACU (56 (3581); 71 (6181) min) was similar in the two groups.
Conclusions. Early but not intermediate recovery times of elderly patients undergoing a wide range of surgical procedures requiring two or more hours of anaesthesia is significantly (P0.05) faster after desflurane.
Br J Anaesth 2003; 91: 5026
Keywords: anaesthesia, general; anaesthesia, geriatric; anaesthetics volatile, desflurane; anaesthetics volatile, sevoflurane; recovery
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Introduction |
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Methods |
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We excluded patients with significant coronary disease or chronic pulmonary disease; renal failure and/or hepatic dysfunction; morbid obesity (body weight >110 kg); a recent (within 12 months) history of alcohol or drug abuse; haematocrit <25%; a personal or family history of malignant hyperthermia; exposure to general anaesthetic agents within the previous 7 days, and if use of nitrous oxide was not appropriate.
Subjects were randomly assigned to receive either desflurane/nitrous oxide (n=25) or sevoflurane/nitrous oxide (n=25). Group assignment was made using computerized randomization. Data were recorded by an observer masked to the anaesthetic allocation. Before pre-medication, subjects were asked to take a Digit-Symbol Substitution Test (DSST)8 and indicate their current pain and nausea on a 10 cm Visual Analog Scale (VAS; 0=no pain, 10=excruciating pain; 0=no nausea, 10=excruciating nausea). In the DSST, patients were given 2 min to replace digits with appropriate symbols located in a legend at the top of the page.
Anaesthesia was induced with fentanyl (12 µg kg1 i.v.) and propofol (1.52.5 mg kg1 i.v.) and muscle paralysis obtained with vecuronium (0.1 mg kg1 i.v.).
Desflurane group
Anaesthesia was maintained with desflurane 26% in combination with nitrous oxide 60% in oxygen. Inspired desflurane concentration (gas flow rate of 2.0 litre min1) was adjusted as necessary to maintain pulse and arterial pressure within 15% of pre-induction values. If acute increases occurred, the inspired concentration of desflurane was increased by up to 50%. Fentanyl (50 µg i.v.) was used to control acute changes that did not respond to two consecutive 50% increases in the inspired concentration of desflurane or if there were other signs of inadequate analgesia (i.e. tearing, purposeful movements, diaphoresis).
Sevoflurane group
Anaesthesia was maintained with sevoflurane 0.61.75% and nitrous oxide 60% plus oxygen. Inspired sevoflurane concentration (gas flow rate of 2.0 litre min1) was adjusted as necessary to maintain haemodynamic variables within 15% of pre-induction values. Similar treatments were used for signs of inadequate anaesthesia, using increased anaesthetic concentrations and doses of fentanyl.
In both groups of patients, if hypertension and tachycardia (an increase of 20% above the baseline values) persisted despite these measures, esmolol was given i.v.. If the response was inadequate, nitroprusside was given according to usual clinical practice. If hypotension and bradycardia (a decrease of >20% of the baseline values) occurred, the subjects position was adjusted and i.v. fluid administration was increased, inspired concentration of anaesthetic agent was decreased or, if needed, stopped. Phenylephrine, ephedrine, dopamine, or epinephrine were used as necessary according to usual clinical practice. Bradycardia (HR <40 beats min1 or causing haemodynamic compromise) was treated with ephedrine or atropine as clinically indicated.
Arterial pressure, ECG, and arterial oxygen saturation were recorded before induction of anaesthesia then, along with end-tidal carbon dioxide, nitrous oxide, and volatile anaesthetic concentrations, every 2 min after induction of anaesthesia for 15 min and then every 5 min until the end of surgery. End-tidal carbon dioxide was maintained between 32 and 35 mm Hg using assisted or controlled ventilation. Doses of vecuronium (0.51.0 mg increments) were given to maintain a single twitch in the train of four. Bispectral Index was continuously monitored. Total anaesthetic time (from administration of induction agent to stopping the volatile anaesthetic agent); total surgical duration (from skin incision to placement of last suture); time to extubation (discontinuation of volatile agent); early recovery (time to awakening (eyes open); time to verbal command (squeeze finger); time to orientation (place, time, date); time to discharge from operating room; post-operative analgesic use; incidence of vomiting; antiemetic use and dose; and time to meet PACU discharge criteria (Post Anaesthesia Recovery Score 9; Table 1) were recorded. While in the PACU, the subjects were asked to take a DSST and indicate their pain and nausea on VAS every 15 min until discharge.
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Statistics
Time to ready for discharge from the PACU was the primary outcome measure. Power analysis (=0.05 and (1ß)=0.8) showed that 45 patients would be required to demonstrate a difference of 5 min. Numerical data are given as median (interquartile range). DSST scores were expressed as per cent of baseline for each subject. Students two-tailed t-test for unpaired data was used to determine if differences were significantly different (P<0.05 duration of surgery, duration of anaesthesia, induction dose of propofol and fentanyl, time to eyes open, time to squeeze finger, time to extubation, time to orientation, time to meet PACU discharge criteria). Fishers exact test was used to determine if significant difference (P<0.05) existed between the number of patients receiving intraoperative fentanyl and analgesic in the PACU. Statistical computations were done using Pharmacologic Calculation System version 4.2(c) and graphing was done using STATA v8.0(c) on an IBM compatible PC using Windows 2000.
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Results |
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Discussion |
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There is remarkably good agreement, qualitative and quantitative, between early outcome results in the two studies. For example, Chen and colleagues7 reported average time to eye opening following discontinuation of desflurane exactly equal to the average time we found for eye opening (6.3 min). This shows that the type of surgery usually is not a major determinant of early recovery.
We concur with Chen and colleagues7 that further studies of the recovery of cognitive function in the elderly following anaesthesia are needed, but such assessment is not easy. The Saskatoon Delirium Checklist,9 Geriatric Mental State Examination,10 and the Confusion Assessment Method,11 in addition to the DSST and MMS, have all been used to evaluate cognitive function in the elderly, to measure return of consciousness, perception, orientation, coherence, memory, and motor activity. To our knowledge, the sensitivity and selectivity of these tests for assessment of cognitive impairment recovery following anaesthesia has not been demonstrated. It is therefore possible that recovery of cognitive function is indeed different following desflurane vs sevoflurane anaesthesia but a difference was not detected by the DSST in our study or the MMS in the study by Chen and coworkers.7
The DSST scores we obtained (expressed as per cent of pre-anaesthetic value-baseline) were variable. We found that this could indicate at least in part, the distraction of patients by factors such as nausea, pain, and emotional distress that influenced their ability or willingness to perform the test.
In summary, we found in elderly patients after a variety of surgical interventions that early recovery is faster following desflurane vs sevoflurane anaesthesia. However, intermediate recovery as measured by DSST did not differ. Assessment of intermediate and longer recovery could be limited by the lack of sensitive and selective measures.
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Acknowledgement |
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References |
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