[Prolonged sedation with propofol in resuscitation. Recovery and pharmacokinetic study. Preliminary results]

Deep sedation during catheter ablation for atrial fibrillation in elderly patients

BACKGROUND

Atrial fibrillation (AF) is the most common cardiac arrhythmia. AF incidence increases with age. AF ablation procedures are routinely performed under deep sedation with propofol. The purpose of the study was to evaluate if propofol deep sedation during AF ablation is safe in elderly patients.

METHODS

Four hundred one consecutive patients (mean age, 61.4 ± 11.1 years; range, 20-82; 66.3 % men) who were presented to our institution for ablation of symptomatic AF were enrolled. Patients were divided into three groups: Patients in group A were ≤50 years old; patients in group B were 51-74 years old; and patients in group C were ≥75 years old. Procedures were performed under deep sedation with propofol, midazolam, and piritramide. SaO2, electrocardiogram, arterial blood pressure, and arterial blood gas were monitored throughout the procedure. Sedation-related complications, intraprocedural complications, and other adverse events were evaluated. Fisher exact or χ (2) tests were used for comparison of adverse events and complications among groups. Analysis of variance was used to compare sedation- and procedure-related parameters.

RESULTS

Fifty-three (13.2 %) elderly patients were in group C and were compared to 73 (18.2 %) patients in group A and 275 (68.8 %) in group B. No significant differences in sedation-related or intraprocedural complications were seen (group A, 1.4 %; group B, 1.1 %; group C, 3.7 %; p = 0.336). Despite a significantly greater drop in systolic blood pressure in under sedation in group C (group A, 15.5 ± 9.5 mmHg; group B, 18.9 ± 16.3 mmHg; group C, 32.3 ± 15.5 mmHg; p < 0.001), no prolonged hypotension was observed. The rate of other adverse events (delirium, respiratory infection, renal failure) was significantly higher in group C (9.4 %), compared to group A (0 %) and group B (2.2 %; p = 0.004).

CONCLUSION

Deep sedation with propofol and midazolam during AF ablation did not result in an increased rate in sedation-related complications in elderly patients. Similarly, the rate of procedural complications was not significantly different among the study groups. The rate of respiratory infections and renal failure was significantly higher in the elderly. All adverse events were treated successfully without any remaining sequelae.

Recovery characteristics and post-operative delirium after long-duration laparoscope-assisted surgery in elderly patients: propofol-based vs. sevoflurane-based anesthesia

BACKGROUND

Post-operative mental dysfunction may be an important problem in elderly patients. This study was designed to compare the effects of propofol and sevoflurane anesthesia on recovery characteristics and the incidence of post-operative delirium (POD) in long-duration laparoscopic surgery for elderly patients.

METHODS

Fifty ASA physical status I-II patients over the age of 65 scheduled for laparoscopic surgery lasting 3 h or more randomly received propofol (group P, n = 25) or sevoflurane (group S, n = 25) for both induction and maintenance of general anesthesia. Both groups were combined with continuous perioperative epidural analgesia. The level of primary anesthetics was adjusted to maintain changes in mean arterial pressure within 20% of the pre-anesthetic values. The emergence times from anesthesia (eye opening, extubation, response to command, and orientation) were recorded, and the occurrence of POD was assessed by the delirium rating scale (DRS) during the first 3 days after surgery. All patients received oxygen and continuous epidural analgesia postoperatively.

RESULTS

Immediate emergence, i.e. eye opening and extubation was significantly faster after sevoflurane (P < 0.05). There was no significant difference between the incidences of POD in the two groups during the first 3 days after surgery. The scores for DRS on day 2 and 3 after surgery, however, were significantly higher in group P than in group S (P < 0.01).

CONCLUSION

Sevoflurane may be preferable to propofol for general anesthesia in combination with epidural analgesia with respect to less effect on mental function during the early postoperative period for long-duration laparoscopic surgery in elderly patients.

The comparative effects of sevoflurane versus propofol in the induction and maintenance of anesthesia in adult patients

A randomized, prospective study was performed at four institutions to compare anesthetic induction, maintenance, and recovery characteristics between sevoflurane- and propofol-based anesthesia in 186 ASA physical status I and 11 patients undergoing elective surgical procedures of 1-3 h. Group 1 (n = 93) patients received sevoflurane-nitrous oxide for both induction and maintenance of anesthesia while Group 2 (n = 93) received propofol-nitrous oxide anesthesia. Induction of anesthesia and tracheal intubation times were significantly shorter with propofol (2.21 +/- 0.2 min, 5.11 +/- 0.3 min, respectively) than with sevoflurane (3.11 +/- 0.2 min, 7.21 +/- 0.3 min, respectively). Emergence times after sevoflurane (8.81 +/- 1.2 min) were significantly shorter than with propofol (13.21 +/- 1.2 min). Overall frequency of complication-free induction, maintenance, and emergence did not differ between the two anesthetic groups. However, side effects involving airway excitement were more prevalent during mask induction with sevoflurane as compared to propofol. Patients in the sevoflurane group were oriented and required postoperative analgesia much earlier than those who received propofol. Both groups were hemodynamically stable throughout the study period. The incidence of postoperative nausea, vomiting, and pain-discomfort scores were similar between the two groups. Urinary specific gravity decreased in the sevoflurane-treated group while serum creatinine and urinary pH were unchanged from preoperative values in both groups. Sevoflurane compared favorably with propofol when used for anesthesia for elective procedures of 1-3 h duration.

Pharmacokinetic implications for the clinical use of propofol

Propofol, the recently marketed intravenous induction agent for anaesthesia, is chemically unrelated to earlier anaesthetic drugs. This highly lipophilic agent has a fast onset and short, predictable duration of action due to its rapid penetration of the blood-brain barrier and distribution to the CNS, followed by redistribution to inactive tissue depots such as muscle and fat. On the basis of pharmacokinetic-pharmacodynamic modelling, a mean blood-brain equilibration half-life of only 2.9 minutes has been calculated. In most studies, the blood concentration curve of propofol has been best fitted to a 3-compartment open model, although in some patients only 2 exponential phases can be defined. The first exponential phase half-life of 2 to 3 minutes mirrors the rapid onset of action, the second (34 to 56 minutes) that of the high metabolic clearance, whereas the long third exponential phase half-life of 184 to 480 minutes describes the slow elimination of a small proportion of the drug remaining in poorly perfused tissues. Thus, after both a single intravenous injection and a continuous intravenous infusion, the blood concentrations rapidly decrease below those necessary to maintain sleep (around 1 mg/L), based on both the rapid distribution, redistribution and metabolism during the first and second exponential phases (more than 70% of the drug is eliminated during these 2 phases). During long term intravenous infusions cumulative drug concentrations and effects might be expected, but even then the recovery times do not appear to be much delayed. The liver is probably the main eliminating organ, and renal clearance appears to play little part in the total clearance of propofol. On the other hand, because the total body clearance may exceed liver blood flow, an extrahepatic metabolism or extrarenal elimination (e.g. via the lungs) has been suggested. Approximately 60% of a radiolabelled dose of propofol is excreted in the urine as 1- and 4-glucuronide and 4-sulphate conjugates of 2.6-diisopropyl 1,4-quinol, and the remainder consists of the propofol glucuronide. Thus for hepatic and renal diseases, co-medication, surgical procedure, gender and obesity do not appear to cause clinically significant changes in the pharmacokinetic profile of propofol, but the decrease in the clearance value in the elderly might produce higher concentrations during a long term infusion, with an increased drug effect. In addition, the lower induction dose observed in relation to increased age might be partly explained by a smaller central volume of distribution.(ABSTRACT TRUNCATED AT 400 WORDS)

[The course of blood concentrations of propofol administered at a constant rate, combined with fentanyl]

The blood concentration of propofol was studied in 14 ASA 1 informed patients, who were to undergo orthopaedic or plastic surgery lasting at least 90 min. Anaesthesia was induced with a 2 mg.kg-1 bolus of propofol together with 0.86 microgram.kg-1 fentanyl. This was followed by a constant rate infusion of propofol and fentanyl, 5 mg.kg-1.h-1 and 3 micrograms.kg-1.h-1 respectively. The mean duration of propofol infusion was 153 +/- 63 min, with extremes of 90 and 315 min. Propofol concentration was measured using gas phase chromatography on total arterial blood; the lower limit of detection was 0.05 mg.l-1. During the infusion, blood concentrations were found between 2 and 4 mg.l-1. It was 2.25 mg.l-1 at the fifth min; this was 80% of the concentration found at the 120th min. There was in fact no statistically significant difference between the values found at the 90th, 120th and 150th min. On stopping the infusion, the concentrations fell rapidly during the first 5 min, and then more slowly. By the 30th min, it had reached a value 4.5 times less than that at the end of the infusion. However, individual variations were found, which could explain delayed recovery. The calculated pharmacokinetic parameters were: elimination half-life = 41.7 +/- 20 min, clearance = 2.14 +/- 0.55 l.min-1 and equilibrium distribution volume = 43.4 +/- 15.2 l. These results are discussed. It is therefore possible to give propofol continuously at a constant rate without having any accumulative effect.