Postoperative Cognitive Dysfunctions Research Articles

Risk Factors for Postoperative Cognitive Dysfunctions in Elderly Patients

Objective: to study the impact of a wide spectrum of factors on the development of postoperative delirium in elderly patients in relation to the changes in their cognitive functions depending on the type of anesthesia and period after surgery. Subjects and methods. The study covered 100 patients aged 65—90 years who had been electively operated on under general, regional, and combined anesthesia. Their cognitive status was elevated before and 1, 4, and 7 days after surgery, by using the Mini-Mental State Examination (MMSE) schedule. The diagnosis was postoperatively established on the basis of interviews, by applying the diagnostic criteria of ICD-10 and DSM-IV (American Psychiatric Association, 1994) and verified by a psychiatrist’s consultation. Results. Seventeen patients developed delirium within the first two days following surgery. Elevated plasma sodium (p<0.000001), leukocytosis (p<0.00002), and postoperative analgesia mode (p<0.02) proved to be statistically significant risk factors for delirium. Worse results of MMSE tests at all postoperative stages than those obtained prior to surgery were significant (p<0.05). Comparing the results obtained on days 1, 4, and 7 showed a significant cognitive improvement. Analysis indicated no significant differences in MMSE changes between the groups of general, regional, and combined anesthesia at all study stages. Conclusion. In elderly patients, surgery and anesthesia lead to a considerable deterioration of cognitive functions even if the development of delirium can be avoided. There is a significant correlation of the development of delirium with leukocytosis, hypernatremia, and postoperative analgesia mode. Key words: anesthesia, postoperative delirium, cognitive status, MMSE, elderly age.

Drugs of anesthesia acting on central cholinergic system may cause post-operative cognitive dysfunction and delirium

Given the progressive and constant increase of average life expectancy, an increasing number of elderly patients undergo surgery. After surgery, elderly patients often exhibit a transient reversible state of cerebral cognitive alterations. Among these cognitive dysfunctions, a state of delirium may develop. Delirium is an aetiologically non-specific syndrome characterised by concurrent disturbances of consciousness and attention, perception, thinking, memory, psychomotor behaviour and the sleep-wake cycle. Delirium appears to occur in 10-26% of general medical patients over 65, and is frequently associated with a significant increase in morbidity and mortality. During hospitalization, mortality rates have been estimated to be 10-26% of patients who developed post-operative delirium, and 22-76% during the following months. Over the last few decades, post-operative delirium has been associated with several pre-operative predictor factors, as well as age (50 years and older), alcohol abuse, poor cognitive and functional status, electrolyses or glucose abnormalities, and type of surgery. The uncertain pathogenesis of post-operative cognitive dysfunctions and delirium has not permitted a causal approach to developing an effective treatment. General anesthesia affects brain function at all levels, including neuronal membranes, receptors, ion channels, neurotransmitters, cerebral blood flow and metabolism. The functional equivalents of these impairments involve mood, memory, and motor function behavioural changes. These dysfunctions are much more evident in the occurrence of stress-regulating transmission and in the alteration of intra-cellular signal transduction systems. In addition, more essential cellular processes, that play an important role in neurotransmitter synthesis and release, such as intra-neuronal signal transduction and second messenger system, may be altered. Keeping in mind the functions of the central muscarinic cholinergic system and its multiple interactions with drugs of anesthesia, it seems possible to hypothesize that the inhibition of muscarinic cholinergic receptors could have a pivotal role in the pathogenesis not only of post-operative delirium but also the more complex phenomena of post-operative cognitive dysfunction.

Release of neuron-specific enolase and S100 after implantation of cardioverters/defibrillators.

Repeated induction of ventricular fibrillation with ensuing alterations in electroencephalogram and jugular venous oxygen saturation is common practice during insertion of transvenous implantable cardioverters/defibrillators. We investigated whether these functional changes are also associated with cerebral injury. Prospective study. University hospital. We studied 45 patients undergoing implantable cardioverter/defibrillator insertion. Eleven patients with cardiac pacemaker implantation, which was performed in the same manner yet without the necessity to induce ventricular fibrillation, served as controls. Serum neuron-specific enolase and S100 were determined before, immediately postoperatively, and 2 hrs postoperatively. In a randomly composed subgroup, neuron-specific enolase was also determined 6 and 24 hrs after surgery. Implantable cardioverter/defibrillator patients only showed an increase of both markers postoperatively. Median neuron-specific enolase values climbed from a preoperative 9.9 to 12.3 and 14.4 microg/L at 2 and 24 hrs after surgery, respectively. This increase was associated with the number of shocks and the cumulative time in circulatory arrest. The highest median S100 level (0.075 microg/L) was reached 2 hrs after the procedure. Neuron-specific enolase and S100 were extremely elevated (13.7 and 0.970 microg/L, respectively) in one patient after an extended episode of ventricular fibrillation. Plasma hemoglobin levels were in the normal range in implantable cardioverter/defibrillator patients throughout the observation period. Apparently, even brief successive periods of global cerebral ischemia cause neuronal damage without obvious severe neurologic deficits. However, they may be related to subtle postoperative neurologic or cognitive dysfunctions that a number of implantable cardioverter/defibrillator patients exhibit after implantation.