Changes in cognitive functions after total hip arthroplasty

Abstract

PURPOSE OF THE STUDY The postoperative delirium is a frequent, oftentimes underestimated complication of total hip arthroplasty. Its occurrence is reported to be between 10% and 50%. The postoperative delirium increases mortality, the length of hospital stay and leads to worse functional results. Even though there is evidence of efficiency of preventive measures and effectiveness of treatment interventions, inadequate attention has been paid so far to this serious complication related to inpatient hospital care. This paper aimed to determine the incidence of cognitive function impairment in relation to the total hip replacement, to determine the influence of the defined parameters on changes in cognitive functions and to draft practice guidelines for the care of patients after a total hip replacement in the framework of prevention and early detection of changes in cognition of patients after total hip replacement. MATERIAL AND METHODS Prospective observational descriptive study, the evaluated parameters included: type of anaesthesia, duration of surgical procedure (operation), type of analgesia, 02 saturation, haemoglobin levels, changes in the ionogram, body temperature, presence of concomitant diseases, polypragmasia, abuse, level of self-sufficiency of patients evaluated by ADL. In order to obtain the data, the Mini Mental State Examination (MMSE), the Abbreviated Mental Test Score (AMTS), Recall and naming test, and the Activities of Daily Living Test (ADL) were used. The monitored group of patients included a total of 116 persons, of whom 68 men and 48 women. The mean age was 71.16 years; the range from 65 to 86 years; median-72.36 years. RESULTS A statistically significant dependence was revealed between the change in cognitive functions and all the monitored parameters, except for the haemoglobin levels after 120 hours postoperatively, ion levels after 120 hours and sex by the 10-point Mini Mental Test score. A statistically significant dependence was revealed between the change in cognitive functions and 02 saturation, ion levels, elevated body temperature after 120 hours postoperatively, age, diabetes, polypragmasia and in correlation with the ADL 120 hours postoperatively by the MMSE test. A statistically significant dependence was revealed between the change in cognitive functions and all the monitored parameters, except for anaesthesia and analgesia, haemoglobin levels after 24 and 120 hours, ion levels after 120 hours, renal insufficiency and in correlation with the ADL after 24 hours by the "Recall and naming" test. DISCUSSION The correlation between delirium and long-term cognition impairment was described by several studies. Both the recent literature and our study clearly indicate a correlation between the postoperative cognitive impairment on the one hand and polypragmasia, age, presence of concomitant diseases on the other hand. In some parameters such as the sex of the patient its influence was not clearly established by the relevant literature or our study. The perioperative factors influencing the onset of delirium referred to in literature are anaesthesia and its duration. Our study reveals the correlation between the anaesthesia and the onset of cognitive impairment when evaluated by the Abbreviated Mental Test Score. As regards the monitored postoperative parameters, the influence of postoperative hyposaturation, decreased haemoglobin level, changes in ionogram, elevated body temperature, lower self-sufficiency of the patient was established. Also our study shows the correlation between the change in the aforementioned parameters and the cognitive impairment, even though not quite clearly in all the parameters. The most sensitive evaluation tool turned out to be the Abbreviated Mental Test Score. CONCLUSIONS Our study clearly showed that a highly sensitive test to detect the current changes in cognition in a short-term horizon is the Abbreviated Mental Test Score. Based on the statistically significant factors determining the onset of the change in cognition that we had revealed, we elaborated a clearly arranged scheme of identified risk factors and interventions for the prevention and early identification of the onset of changes in cognitive functions and potential delirium.