The Effects of General Anesthesia on Cognitive Dysfunction - Research Paper Example

Role of General Anesthesia on Cognitive Dysfunction in Elderly Patients Research Paper for Research Methodology for Nurse Anesthetists CONTENTS Introduction 2. Statement of problem 3. Theoretical/conceptual basis for the research 4. Review of Literature 5. Significance of the study 6. Methodology Introduction Surgical interventions in the elderly are not free from associated as well as subsequent problems. Surgery itself when recommended may elicit apprehension progressing to actual fear in all and more so in the elderly. The psychological effect of surgery may be profound in overtly sensitive patients who fear the surgeon’s scalpel. General anesthetics too have a variety of metabolic pathways in the body and exert unavoidable side effects, which sometimes lead to cognitive disorders post surgically (Bryson & Wyand, 2006). The condition has been encountered with alarmingly high frequency in patients past their prime and assumes serious overtones in the elderly (Parikh & Chung, 1995). Relatives of elderly patients have reported post surgical cognitive disorders in most of the patients in many hospitals (Peisah, 2002). Postoperative Cognitive Decline (POCD) in the elderly is now a well established and recognized disorder which has forced the world medical community to re-think their strategies in handling such patients (Lewisa et al, 2006). Regional anesthesia instead of general is advisable in such patients in order to minimize POCD when minor surgical procedures are undertaken (Canet et al, 2003). The issue has assumed more significance since there is increasing number of elderly patients in the world with the growing figures of better life expectancy (Muravchick, 2008). Significant co-morbid conditions like cardiovascular disease further aggravate the side effects of general anesthesia in elderly patients (Muravchick, 2008). Genetic factors of robustness in certain races of the world also complicate the issue as some races have predisposition towards longevity and variability in tolerance to medications including anesthetics and toxins (Goodman & Gilman, 2001). There have been difficulties to show that age is an independent factor in the cognitive loss in the elderly after anesthesia (Muravchick, 2008). When a patient is presented for surgery, he or she has an array of medical conditions which are the determinants to selection of anesthetic as the preexisting conditions will determine the series of physiological stressors from which the patient has to be protected, including the very agents used to initiate and sustain the anesthetic condition. Surgical stress causes varied responses in the body involving the hypothalamic-pituitary-adrenal axis, the sympathetic nervous system and the acute-phase response which are activated by multifarious triggers (Udelsman and Holbrook, 1994). The preoperative, intraoperative and the postoperative periods of surgery are important considerations when providing anesthesia. Preexisting comorbidities like electrocardiogram of the patient, abnormalities if any in the cardiovascular, pulmonary, hepatic and renal systems need to be analyzed in the preoperative period. The choice and dosage of preanesthetic medication is also decided at this stage. During the intraoperative period continuous electrocardiography, pulse oximetry, body temperature, CO2 concentration in the exhaled gas, blood pressure, urine output and blood loss must be monitored precisely. Postoperative recovery and return to a normal physiological as well as psychological status are very essential although they tend to be neglected if the surgical procedure has been a success. The matter assumes great significance in the elderly in whom the mental status is already on the decline due to age and susceptible to damage even with the recommended exposure to anesthetics, which results in cognitive dysfunction. Therefore there is a need to determine which anesthetic agents, surgical procedures, pre and coexisting disorders and post surgical procedures lead to loss of cognitive function in the elderly and what approaches can be tried to minimize the occurrence of such conditions. The matter is currently under intensive research and new insights have been gained in the last few years. Statement of problem or questions The adverse effects of the medication administered to the elderly usually include cognitive disability post operatively as has been shown in various studies (Bryson and Wyand, 2006; Canet J et al, 2003; Ritchie Karenet al, 2005). What needs to be researched is whether post operative care needs to incorporate cognitive therapy in cases when the anesthesia causes cognitive disability. Is there a role of palliative therapy in such cases? There is a need for studies on elderly patients presented at various hospitals for major or minor surgery involving the use of anesthetics shown to cause cognitive disorders. This should lead to choosing the least damaging agent followed by cognitive therapy after the surgery which could be a combination of both drug therapy as well as emotional support. Theoretical/conceptual basis for the research The growing numbers of elderly people in the society are subject to diseases and disorders which can be of physiological or pathological origin. This necessitates therapeutic interventions which may sometimes require surgery. As anesthetic agents exert profound effects on the central nervous system, their use in the elderly has to be appropriate or minimal keeping in mind the already compromised central nervous system in such people. Increasing incidents of POCD and delirium encountered frequently post anesthetically in the elderly necessitates research in order to short list the least damaging anesthetic agents and the development of therapeutic strategy needed post surgically to rehabilitate such patients. Model or theory supporting the study A well designed study was undertaken by Bryson and Wyand in 2006 in which they explored the risk of delirium and POCD in the elderly after general anesthesia as compared to local anesthesia. Past clinical trials and incidents of delirium and POCD were evaluated using modern software and the authors concluded that there was no significant difference in the two conditions when either local or general anesthetic was used. This study just collected historical data and analyzed it but did not correlate variations such as pre existing diseases and moreover the data was of anesthetics which have been discontinued in modern anesthesiology. Post surgical therapeutic interventions, if any, have not been taken into account. Advances in anesthesiology with the availability of safer agents as well as modern monitoring techniques during surgery can give a better clinical picture of such patients and a new study can be designed to evaluate the effects and the development of a sound post surgical rehabilitation strategy using pertinent drugs and palliative care. Pre surgical evaluation of the patients and prognosis needs to be incorporated in the study. Cognitive Tests such as the Mini-Mental State (MMS) need to be employed to evaluate the patients (Chen Xiaoguang et al, 2001) and appropriate therapeutic strategies designed. Scientific support In previous studies of this kind Ritchie Karen et al, (2005) found significant cognitive dysfunction in the elderly up to 3 days post surgically but could not arrive at any significant result as far as long term impairment was concerned due to the heterogeneity of the procedures used and the populations targeted for such studies. Such factors therefore need to be eliminated in a fresh study. Lewisa et al (2007) have suggested that regional anesthesia may be favorably considered in the elderly rather than general anesthesia and deep sedation as the latter usually is associated with POCD and its increase in morbidity as well as mortality figures. This approach needs to be studied further and the least damaging agents and route need to be identified. Review of Literature The impact of anesthesia on the cognitive functioning of the elderly has been studied widely during the last decade. Ritchie Karen et al (1997) reported that although there was significant cognitive dysfunction in elderly patients 1 to 3 days post operatively, reports on long term impairment were inconsistent due to heterogeneity of the procedures used and the type of populations targeted for such studies. They have postulated the existence of other interacting etiological factors as there were variations in long term effects in the studied cases, but the authors have only speculated on these interacting factors and not specified them. Canet J et al, (2003) conducted a study in which they inferred that cognitive dysfunction occurred in the elderly undergoing even minor surgery, only if they were hospitalized. Patients treated in the out patient department were significantly better off in their cognitive abilities than those who were hospitalized. This again signifies the emotional fear and apprehension associated with hospitalization by the elderly patient. The authors accordingly advocated the use of a strategy in which hospitalization should be avoided in elderly patients undergoing minor surgery as far as possible. Comparative studies have been undertaken where the recovery of cognitive function in the elderly and the young after anesthesia has been evaluated. In one such study by Chung F. et al (1990), the rate of mental recovery in the young and the elderly undergoing abdominal surgery using general anesthesia were compared. Accepted protocols of tests were followed for assessing neuropsychiatric functioning both pre and post operatively. The results were variable and the authors concluded that there were no differences in cognitive recovery in the young as compared with the elders. Bryson and Wyand (2006) have undertaken a massive review for a clinical update on the risk of delirium and postoperative cognitive dysfunction in the elderly using the latest software and statistical tools and have analyzed the evidence of such occurrences till date when both regional and general anesthetics have been used. They identified a total of eighteen randomized and controlled trials where the role of general and regional anesthetics on both delirium and POCD were compared. Their analysis of more than 2500 patients showed that there were no significant differences in the outcomes on both delirium and POCD when either regional or general anesthesia was used in elderly patients. The authors have suggested that preexisting pathological conditions in such patients and the physiological stress associated with surgery along with the type of medications administered both pre anesthetically and after the surgery might contribute towards the production of delirium and POCD. Moreover the authors feel that in future more established and standardized protocols for the evaluation of both these conditions should be used at the clinical level. The authors have hinted at the presence of some other unidentified factors which might play a role in the production of such disorders. Similar inferences have been drawn in a study by Ritchie Karenet al (2005) that searched five bibliographic databases and analyzed them for the relationship between anesthesia and loss in cognitive function. They found significant cognitive dysfunction in the elderly up to 3 days post surgically but could not arrive at any significant result as far as long term impairment was concerned due to the heterogeneity of the procedures used and the populations targeted for such studies. They too have suggested further research for other unknown etiological factors. Lewisa et al (2007) have suggested that regional anesthesia may be favorably considered in the elderly rather than general anesthesia and deep sedation as the latter usually is associated with POCD and its increase in morbidity as well as mortality figures. To review the effects of anesthetics as well as any other drugs in the elderly, one must understand that there are major pharmacokinetic as well as pharmacodynamic differences in the elderly as compared to young people. Pharmacokinetic parameters are concerned with the processes of absorption, distribution, metabolism and elimination of the drug from the body while pharmacodynamic variables determine the relationship between the concentration of the drug at the site of action and the intensity of effects produced. A review by McLeskey (2008) states that a drug once administered to the elderly patient remains active for a longer duration inside the body and has increased blood levels as compared to youngsters due to smaller volume of distribution initially and later due slower drug metabolism. Hence it has a longer period of pharmacological action in the elderly. The extent of protein binding of the drug also has an important role to play as the protein bound fraction is unavailable for pharmacologic action and also unable to pass the blood brain barrier, which acts as a shield to protect the brain from harmful molecules carried in the blood stream. All anesthetic agents are bound to these plasma proteins up to some extent and this binding is less efficient in the elderly leading to enhance level of unbound anesthetic molecular levels in the blood stream leading to more profound effect of the administered agent in the elderly (Sear et al, 1983). Other factors which lead to variations in the elderly are the change in body compartments, hepatic renal and central nervous systems (Peacock et a 1990). The major change in body compartment in the elderly is the loss of muscular lean mass and increased levels of adipose tissue or fat (McLeskey, 2008). There is also a decrease of total blood volume up to 20% in the elderly (McLeskey, 2008). This will result in higher plasma concentration of the anesthetic drug in the elderly upon administration and also deposition of the drug in the adipose tissue which will keep on leeching for a much longer duration after the operative procedure (McLeskey, 2008). Hepatic and renal functions start reducing by 1% after age 30 and by ages 60-80 they are at a level of about 60% as compared to youngsters (McLeskey, 2008). Hepatic metabolism is reduced as well as the glomerular filtration rate which leads to prolonged periods of drug presence inside the body which can lead to toxic effects (McLeskey, 2008). Therefore there is a much more gradual fall of plasma level of anesthetics in the elderly as compared to young people. In the central nervous system there is a gradual decline of the neuronal cellular population with age and there is a parallel reduction in cerebral blood flow and oxygen consumption (Hilgenberg, 1986). This ultimately results in a reduced age related anesthetic requirement as it is easier to achieve surgical anesthesia in the elderly with lower doses as compared to young people (Scott & Stanski, 1987).. Administration of the standard dose of the anesthetic based on minimum alveolar concentration can thus be dangerous in elderly patients as it can produce irreversible damage (Rampil, 1991). The agents used for anesthesia have undergone dramatic improvements in safety as well as efficacy since the discovery of ether and currently used agents are Nitrous oxide, Desflurane, Isoflurane and Sevoflurane. The safety of the latest agents should be evaluated taking their properties into consideration for use in sensitive patients like children and the elderly. In a comparative study on Desflurane and Isoflurane on the recovery of cognitive function in the elderly, Chen Xiaoguang et al, (2001) found that there was no significant difference between the two agents and cognitive recovery was similar with either. Emergence from anesthesia was more rapid with Desflurane and there was shorter length of stay in the post anesthesia care unit. Both these volatile anesthetics are rapidly eliminated from the body with minimal metabolic breakdown and hence are the ideal candidates for use in the elderly and may reduce both postoperative delirium and cognitive dysfunction. In addition they have lower blood gas partition coefficients as compared to traditional volatile anesthetics which promotes faster emergence from anesthesia. Due to the multifarious post operative conditions, pre existing pathologies, the surgical procedure as such and the post operative delirium and cognitive disorders, the role of palliative care in Geriatric anesthesia assumes great importance. According to Doyle (1994) and Goodlin (1997) palliative medicine is a recent addition to the list of medical sub specialties. There is more emphasis on improving the quality of life in general and care of the elderly patients in particular as due to rise in life expectancy more and more elderly and sick people are in need of urgent medical as well as social attention. According to Goodlin, the WHO defines palliative care as follows: * Affirms life and regards dying as a normal process * Neither hastens nor postpones death * Provides relief from pain and other distressing symptoms * Integrates the psychological and spiritual aspects of patient care * Offers a support system to help the family cope during the patient’s illness and in their own bereavement. Palliative medicine is thus the active total care of the patient whose disease is not responsive to curative treatment. It addresses the psychological, social and spiritual needs of the patient. It is less expensive and provides succor to the patient as well as his or her family. Significance of the study The well being of senior citizens is a matter of great concern to the medical community and society. Anesthesia is now a well developed discipline and highly technical and automated wherein the patients responses during the surgery and dose alteration in the agent used are possible. Alterations in the cognitive abilities post surgically in the elderly are an established and oft encountered malady which causes great distress to the sufferer as well as his or her family. It becomes imperative to study the means and methods of minimizing the effects of anesthetics on the elderly by using a precautionary approach before the initiation of any therapeutic regimen by carefully evaluating the physiological status of the patient, presence of co-pathologies and their amelioration before the procedure and finally selecting the most appropriate time for the surgery by developing forecasting methods predictive of a high success rate. Keen and unfailing attention of the medical fraternity carrying out the procedure needs to be ascertained without an iota of error. Monitoring during and after surgery should be within the environs of highly professional intensive care units till there is complete elimination of the anesthetic from the body. This should be followed by a period of observation during which symptoms of delirium and POCD should be monitored and handled professionally. After the completion of all drug dependent and technology dependent means and measures, the patient should be put in the hands of a new class of nursing attendants who should be experts in the field of palliative medicine. Providing emotional support with patience and tolerance should be the primary objective rather than dependence on sedatives and hypnotics to keep such patients in deep slumber as is the usual practice. Cognitive dysfunction is usually interpreted by otherwise qualified psychiatrists who are invariably young and impatient and there is a tendency to prescribe some anti depressant medications to get rid of one’s responsibility rather than aiming at the total recovery of the patient which is already compromised due to the slow metabolism and the physical as well psychological trauma of surgery. Methodology The study will be conducted at a minimum of five and a maximum of seven hospitals (to make the sample size statistically significant) where geriatric surgery is already a specialty and the frequency of such procedures is high. The patients will be shortlisted from the out patient department and only those will be selected who don’t have any serious co-pathological disorders where the prognosis is grave. Patients suffering from chronic and incurable diseases will not be selected, but those undergoing procedures such as knee replacement or other minor operations which otherwise have a good prognosis will be selected as the emphasis has to be on the effects of general anesthesia on cognitive loss or recovery rather than the condition itself. Preanesthetic evaluation of the shortlisted patients will be carried out to eliminate any inherent physiological disorders or abnormalities. This evaluation will be done at least a month before the actual surgical procedure has to be performed on the patient. Close watch and frequent laboratory analysis of various parameters will be carried out during the month to assure a consistent physiological status with uniformity in all the patients. In addition appropriate psycho analytical tests like the Mini-Mental State (MMS) test will be carried out to evaluate the existing cognitive status of the patient so that no misinterpretation is there after surgery. The surgery itself will be carried out using the safest anesthetic agents available which are recommended for such patients and as advised by the attending anesthesiologist or surgeon. The ideal anesthetics will be a combination of Nitrous oxide, Desflurane, Isoflurane and Sevoflurane whose dosage rate will be adjusted taking into consideration the low minimal alveolar concentration required in the elderly and as determined by a clinical pharmacologist. Pre and post anesthetic medication data will be monitored separately according to the individual conditions of the patients. Post surgical intensive care personnel will be trained to handle the patients gently till recovery from anesthesia is complete. Appropriate recommended psycho analytical protocols will be employed to assess the delirium and the POCD status of the patients. After the discharge of the patients form the intensive care facility the patients will be put into a special nursing care facilities for a period of one to three months where the emphasis will be less on medication but more on emotional support and reorientation of the patients by specially trained nurses who will stay 24 hours a day with the patient. A couple of nursing attendants should be fixed for each patient so that the 100% attention is ensured. Data will be evaluated for recovery of cognitive function by applying appropriate statistical software. References Bryson Gregory L. & Wyand Anna, Evidence-based clinical update: General anesthesia and the risk of delirium and postoperative cognitive dysfunction, Canadian Journal of Anesthesia 2006 53:669-677 . Canet J, Raeder J, Rasmussen LS, Enlund M, Kuipers HM, Hanning CD, Jolles J, Korttila K, Siersma VD, Dodds C, Abildstrom H, Sneyd JR, Vila P, Johnson T, Muñoz Corsini L, Silverstein JH, Nielsen IK, Moller JT; ISPOCD2 investigators. Cognitive dysfunction after minor surgery in the elderly. Acta Anaesthesiol Scand. 2003 Nov;47(10):1204-10 Chung F, Seyone C, Dyck B, Chung A, Ong D, Taylor A, Stone R, Age-related cognitive recovery after general anesthesia. Anesth Analg. 1990 Sep;71(3):217-24. Doyle D. Palliative medicine: A UK specialty. J Palliat Care. 1994; 10(1):8-9. Goodman and Gilman’s the pharmacological basis of therapeutics – 10th ed. / [edited by] Joel G. Hardman, Lee E. Limbird, Alfred Goodman Gilman, 2001, McGraw-Hill Companies, Inc. Chapter 13, Pg. 324 Goodlin SJ. What is palliative care? Hospital Pract (Off Ed). 1997; 32(2):13-14. Hilgenberg JC. Inhalation and intravenous drugs in the elderly patient. Seminars in Anesthesia 1986; 5:44-53. Karen Ritchie , Catherine Polge , Guilhem de Roquefeuil , Michel Djakovic and Bernard Ledesert, Impact of Anesthesia on the Cognitive Functioning of the Elderly, International Psychogeriatrics (1997), 9: 309-326 Cambridge University Press. Lewisa M.C., Nevoa I., Paniaguaab M.A., Ben-Aric A., Prettoa E., Eisdorfera S., Davidsonac E., Matotc I., Eisdorfera C., Uncomplicated general anesthesia in the elderly results in cognitive decline: Does cognitive decline predict morbidity and mortality?, Medical Hypothesis, Elsevier, Volume 68, Issue 3, Pages 484-492 (2007) McLeskey Charles H. (2008) ,Pharmacokinetic and Pharmacodynamic Differences in the Elderly, Syllabus on Geriatric Anesthesiology, American Society of Anesthesiologists, Online. Available: http://www.asahq.org/clinical/geriatrics/pharma.htm Muravchick Stanley, 2008 Geriatric Anesthesia - Are You Ready? Syllabus on Geriatric Anesthesiology American society of Anesthesiologists, http://www.asahq.org/clinical/geriatrics Parikh SS, Chung F. Postoperative delirium in the elderly. Anesth Analg 1995;80:1223–32. Peacock JE, Lewis RP, Reilly CS, et al. Effect of different rates of infusion of propofol for induction of anaesthesia in elderly patients. Br J Anaesth. 1990; 65:346-352. Peisah Carmelle, Persistent Postoperative Cognitive Decline in an Elderly Woman With Preexisting Neuropathology, Psychiatric Services, March 2002 Vol. 53 No. 3 Rampil IJ, Lockhart SH, Zwass MS, et al. Clinical characteristics of desflurane in surgical patients: Minimum alveolar concentration. Anesthesiology. 1991; 74:429-433. Sear JW, Cooper GM, Kumar V. The effect of age on recovery. A comparison of the kinetics of thiopentone and althesin. Anaesthesia. 1983; 38(12):1158-1161. Scott JC, Stanski DR. Decreased fentanyl and alfentanil dose requirements with age: A simultaneous pharmacokinetic and pharmacodynamic evaluation. J Pharmacol Exp Ther. 1987; 240:159-166. Udelsman, R. and Holbrook, N.J. Endocrine and molecular responses to surgical stress. In, Current Problems in Surgery. Vol. 31, no. 8, Mosby, St. Louis, 1994, pp. 653-720. Wenker, Olivier C. "Review of Currently Used Inhalation Anesthetics: Part I". The Internet Journal of Anesthesiology. 3.2(1999): 10 pp. Online. Available: http://www.ispub.com/journals/IJA/Vol3N2/inhal1.htm 15 June 1999. Wenker, Olivier C. "Review of Currently Used Inhalation Anesthetics: Part II". The Internet Journal of Anesthesiology. 3.3(1999): 8 pp. Online. Available: http://www.ispub.com/journals/IJA/Vol3N3/inhal2.htm 8 July 1999. Xiaoguang , Manxu Zhao, Paul F. White, Shitong Li, Jun Tang, Ronald H. Wender, Alexander Sloninsky,Robert Naruse, Robert Kariger,Tom Webband Eve Norel, The Recovery of Cognitive Function After General Anesthesia in Elderly Patients: A Comparison of Desflurane and Sevoflurane, Anesth Analg 2001;93:1489-1494 Read More