Results: At 7 days, POCD was found in 37/188 patients (19.7%, [14.3—26.1%]) after general anaesthesia and in 22/176 (12.5%, [8.0—18.3%]) after regional anaesthesia, P ¼ 0.06. After 3 months, POCD was present in 25/175 patients (14.3%, [9.5—20.4%]) after general anaesthesia vs. 23/165 (13.9%, [9.0—20.2%]) after regional anaesthesia, P ¼ 0.93. The incidence of POCD after 1 week was significantly greater after general anaesthesia when we excluded patients who did not receive the allocated anaesthetic: 33/156 (21.2% [15.0—28.4%]) vs. 20/158 (12.7% [7.9—18.9%]) (P ¼ 0.04). Mortality was significantly greater after general anaesthesia (4/217 vs. 0/211 (P < 0.05)). Conclusion: No significant difference was found in the incidence of cognitive dysfunction 3 months after either general or regional anaesthesia in elderly patients. Thus, there seems to be no causative relationship between general anaesthesia and long-term POCD. Regional anaesthesia may decrease mortality and the incidence of POCD early after surgery.

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Does anaesthesia cause postoperative cognitive dysfunction? A randomised study of regional versus general anaesthesia in 438 elderly patients

This article describes a systematic review on the research into postoperative cognitive dysfunction (POCD) in noncardiac surgery to ascertain the status of the evidence and to examine the methodologies used in studies. The review demonstrated that in the early weeks after major noncardiac surgery, a significant proportion of people show POCD, with the elderly being more at risk. Minimal evidence was found that patients continue to show POCD up to 6 months and beyond. Studies on regional versus general anesthesia have not found differences in POCD. Many studies were found to be underpowered, and a number of other methodologic difficulties were identified. These include the different types of surgery in studies and variations in the number and range of neuropsychological tests used. A particular issue is the variety of definitions used to classify individuals as having POCD.

https://chguv.san.gva.es/docro/hgu/document_library/servicios_de_salud/servicios_y_unidades/Servicio_anestesia/Sesiones_clinicas/2007-2008/080715_Protocolo.pdf

Postoperative cognitive dysfunction after noncardiac surgery: a systematic review.

Postoperative cognitive function (POCD) has been subject to extensive research. In the literature, large differences are apparent in methodology such as the test batteries, the interval between sessions, the endpoints to be analysed, statistical methods, and how neuropsychological deficits are defined. Traditionally, intelligence tests or tests developed for clinical neuropsychology have been used. The tests for detecting POCD should be based on well-described sensitivity and suitability in relation to surgical patients. In tests using scores, floor/ceiling effects may compromise the evaluation if the tests are either too easy or to difficult. Uncontrolled testing facilities and change of test personnel may affect the test performance. Practice effects are pronounced in neuropsychological tests but have generally been ignored. The use of a suitable normative population is essential to allow correction for practice effects and variability between sessions. Missing follow-up may severely compromise valid conclusions since subjects unable or unwilling to be examined are particularly prone to suffer from POCD. In the statistical analysis of the test results, the evaluation should be based on differences between pre- and postoperative performance. Parametric statistical tests are not relevant unless the appropriate Gaussian distributions are present, perhaps after transformation of data. The definition of cognitive dysfunction should be restrictive and the criteria should be fulfilled in only a small proportion of volunteers. In the literature, these requirements often have not been fulfilled. This precludes a reasonable estimation of the incidence of POCD and the conclusions of comparative studies should be interpreted with great caution. In this review article, we present a number of recommendations for the design and execution of studies within this area. In addition, the critical reader may use these recommendations in the evaluation of the literature.

The assessment of postoperative cognitive function.

We conducted an on-line search and manual searches for 1966 through 1992 to determine the incidence, diagnosis, risk factors, and treatment of postoperative delirium. Of the 374 citations found, 277 articles were excluded after criteria of relevance were applied. After methodologic criteria for validity were applied to the remaining 80 articles, 26 studies were retained for the final information synthesis. The incidence of postoperative delirium was 36.8% (range, 0% to 73.5%). Primary reasons for this disparity were insufficient sample size and inconsistent application of numerous diagnostic tools. One study provided statistically significant data that demonstrated that postoperative delirium is underdiagnosed by physicians and nurses. Four of the articles that met the established criteria provided risk factor data. Although age, preoperative cognitive impairment, and the use of anticholinergic drugs were significantly associated with postoperative delirium, gender, type and route of anesthesia, and sleep deprivation were not. Two studies demonstrated a decreased incidence of postoperative delirium when patients underwent preoperative psychiatric counseling or participated in a structured perioperative program. These findings indicate a need for (1) accurate incidence data with further definition of risk factors and (2) studies that address the diagnosis and treatment of this common postoperative problem. (Arch Intern Med. 1995;155:461-465)

Postoperative Delirium: A Review of 80 Primary Data-Collection Studies

Objective
To compare the effect of post-operative analgesia using epidural versus intravenous infusions on the incidence of delirium after bilateral knee replacement surgery in elderly patients. Additional risk factors and impact on post-operative recovery were also assessed.

Design
Prospective randomized controlled trial.

Setting
Urban referral hospital specializing in elective orthopedic surgery.

Patients
60 consecutive patients undergoing bilateral knee replacement surgery with epidural anesthesia were approached; 51 patients were eligible and consented. The mean age was 68, 55% were women, and there was a high prevalence of comorbid medical disease. No patient was demented pre-operatively.

Intervention
Random allocation to either continuous epidural infusion of bupivicaine and fentanyl or continuous intravenous infusion of fentanyl. Infusions were initiated at the first complaint of pain and continued through the 36- to 48-hour stay in the recovery room.

Main Outcome Measure
Acute post-operative delirium defined using an algorithm based on DSM III criteria.

Results
The overall incidence of acute delirium was 41%, with no difference between types of post-operative analgesia. Predictors of delirium were age, gender, and pre-operative alcohol use. All cases resolved within 1 week, and length of stay and achievement of physical therapy goals were the same for delirious and non-delirious patients.

Conclusions
There is a high incidence of post-operative delirium in elderly non-demented patients following bilateral knee replacement, regardless of whether post-operative analgesia is administered by the epidural or intravenous route.

Post-operative delirium: predictors and prognosis in elderly orthopedic patients.

The memory performance of 60 female patients, scheduled for either local or general anaesthesia and extraction of senile cataract, was investigated. Six subtests of the Wechsler Memory Scale and four items of memory tests according to Luria were performed. One week postoperatively there was a diminution in the performance of the Wechsler Memory Scale and Luria tests. Comparison of the pre- and postoperative diminutions between the local and general anaesthesia groups was statistically significant only in the Luria tests. According to this study general anaesthesia does not affect memory function more profoundly than local anaesthesia supplemented with tranquilizing and/or analgesic drugs. In this respect, the advantages of general anesthesia should be utilized, at least in patients without clearcut contraindications.

A comparison of memory function following local and general anaesthesia for extraction of senile cataract.

Background : The Electroretinogram (ERG) is used clinically to assess the function of retina. Anaesthetic agents are known to affect ERG, and as anaesthesia is often needed in children and uncooperative patients, knowledge about its effects is of clinical importance. Barbiturates selectively depress ERG components, and we compared thiopentone with propofol to assess if the latter preserved retinal function better. Methods : Ten pigs, average weight 17 kg ( SD ± 2 kg) were anaesthetized randomly with propofol 10 mg kg -1 or thiopentone 30 mg kg -1 . Anaesthesia was maintained by 65% nitrous oxide in oxygen and continuous infusion of the induction agent, i.e. 10 mg kg -1 h -1 of propofol, or 10 mg kg -1 h -1 for the first hour, then 5 mg kg -1 h -1 of thiopentone, with doses being based on pilot studies. After an interval of one week the programme was repeated using the other agent. After 40 minutes dark-adaptation, responses to single flashes of graded intensities from a xenon flashlamp were recorded at five-minute intervals. The a- and b-wave amplitudes and implicit times (time to peak), and a-wave slopes were determined. Results : The b-wave implicit time was significantly shorter during propofol anaesthesia than when using thiopentone. The effect was most pronounced at the lowest intensities (P < 0.01). No statistically significant differences were found in the amplitudes of the b-waves. The a-wave appeared at lower stimulus intensity (P < 0.05) and the a-wave slopes were significantly steeper (P < 0.01) during propofol anaesthesia. Conclusion : Propofol accordingly appeared to preserve the photoreceptor response better than thiopentone, and may therefore be considered to be more suitable for ERG recordings than thiopentone.

Propofol influences the electroretinogram to a lesser degree than thiopentone

With atracurium and vecuronium, spontaneous recovery of residual neuromuscular blockade monitored electromyographically during 0.5% isoflurane anaesthesia was studied in 60 patients undergoing plastic surgery. After thiopentone, in random order, either atracurium 0.5 mg kg-1 or vecuronium 0.1 mg kg-1 was administered and isoflurane added to N2O and O2 mixture. Following spontaneous recovery of both the single twitch amplitude (T1) to 75% of the control value and the train-of-four ratio (TOF ratio) to 75%, incremental doses of the relaxant were given to maintain the T1 at less than 10%. Before the end of surgery, the blockade was again permitted to recover spontaneously. During the initial spontaneous recovery, the mean recovery time of T1 from 25% to 75% (the recovery index) with atracurium was longer (P less than 0.001) than that with vecuronium (13.2 min and 10.1 min, respectively) but, during the second recovery, the mean recovery index was shorter (P less than 0.05) with atracurium than with vecuronium (16.1 min and 19.8 min, respectively). The recovery time from T1 75% to TOF ratio 75%, indicating the recovery rate of residual neuromuscular blockade, with atracurium was about 15 min after both the initial and the second recoveries. With vecuronium, the respective recovery times were significantly (P less than 0.001) longer (25.6 min and 38.5 min, respectively). It is concluded that with vecuronium there is slower spontaneous recovery of residual neuromuscular blockade than with atracurium.

Spontaneous recovery of residual neuromuscular blockade after atracurium or vecuronium during isoflurane anaesthesia.

The effect of prior administration of tubocurarine (5 mg) or alcuronium (3 mg) on changes in cardiac rate and rhythm caused by the second dose of suxamethonium (1 mg/kg) during halothane-nitrous oxide-oxygen anaesthesia was studied in 60 patients. Tubocurarine and, particularly alcuronium were found to prevent bradyarrhythmias caused by the second dose of suxamethonium. These non-depolarizing relaxants had a moderate stabilizing action on the cardiac rhythm also during intubation and the commencement of artificial ventilation. The relaxation obtained by the first dose of suxamethonium (1 mg/kg) was sufficient to permit quiet intubation in all cases. The use of a non-depolarizing muscle relaxant prior to suxamethonium during halothane-nitrous oxide-oxygen anaesthesia is recommended.



ZUSAMMENFASSUNG

Bei 60 Patienten wurde die Wirkung einer Voraus-injektion von Tubocurarin (5 mg) oder Alcuronium (3 mg) auf Veranderungen der Herzfrequenz und des Herzrhythmus, verursacht durch eine Zweitdosis von Suxamethonium (1 mg/kg) wahrend einer Halothan-N2O-Narkose untersucht. Es zeigte sich, das Tubocurarin und insbesondere Al-curonium Bradyarrhythmien verhinderten, die sonst nach der Zweitdosis von Suxamethonium auftreten. Diese nicht-depolarisierenden Relaxantien hatten auch wahrend der Intubation und des Beginns der kunstlichen Beatmung eine masiggradig stabilisie-rende Wirkung auf den Herzrhythmus. Die durch die erste Dosis von Suxamethonium (1 mg/kg) erzielte Erschlaffung war in allen Fallen ausreichend fur eine glatte Intubation. Die Vorausgabe eines nicht-depolarisierenden Muskelrelaxans vor Suxamethonium wahrend einer Halothan-N2O-O2-Narkose wird empfohlen.

The effect of tubocurarine and alcuronium on suxamethonium-induced changes in cardiac rate and rhythm.

Eleven ophthal-moscopically healthy dark adapted dogs were examined by DC ERG technique with single flash full field illumination starting with near b-wave threshold blue (tests 1-3) and white (tests 4-6) stimuli of different intensity and ending with 30 Hz photopic flicker smuli (test 7) after light adaptation. All animals were anaesthetized using 2 different anaesthetic methods: Anaesthesia I (A I): Induction with thiopentone sodium, continued with halothane and nitrous oxide in oxygen. Anaesthesia II (A II): Praemedication with xylazine hydrochloride followed by anaesthesia with ketamine hydrochloride. A minimum interval of 1 week was kept between all anaesthesias. The a- and b-wave amplitudes and latencies were determined. Statistical analysis of results indicated that the a- and b-waves were elicited by weaker intensities in A II. In Tests 3-6 the a-wave was highly significantly (P < 0.001), higher in amplitude in AII than in A I. Differencies in b-wave amplitudes were not statistically significant (except Test 1). The b-wave latencies were longer in AI in Test 2 (using low intensity blue light). The a-wave latencies were slightly shorter in AII in Test 6 (using high intensity white light). In additional experiments the selective action of the different agents (except N2O) used in AI and AII was studied. Thiopentone alone given to 3 dogs seemed to depress the a-wave selectively. Halothane given separately to 3 dogs lowered both the a- and b-wave amplitudes. Ketamine given with a neuromuscular blocking agent to three dogs resulted in responses almost identical to those in AII. Xylazine with vecuronium given to 4 dogs resulted in responses with slighly depressed a- and b-waves in comparison to ketamine with vecuronium. The results indicate that when developing an animal model for the electrophysiologic study of human retinal dystropies, the actions of different anaesthetics upon the ERG components are of great importante.

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Ulla Karhunen

Papers

A comparison of memory function following local and general anaesthesia for extraction of senile cataract.

Propofol influences the electroretinogram to a lesser degree than thiopentone

Spontaneous recovery of residual neuromuscular blockade after atracurium or vecuronium during isoflurane anaesthesia.

The effect of tubocurarine and alcuronium on suxamethonium-induced changes in cardiac rate and rhythm.

Effects of thiopentone halothane-nitrous oxide anaesthesia compared to ketamine-xylazine anaesthesia on the DC recorded dog electroretinogram.