Discussions
In this study, we investigated the effect of preoperative hospitalization periods on early POCD development and the associated risk factors in adult patients undergoing total hip placement surgery under regional anesthesia. We observed a higher POCD incidence rate in patients with prolonged preoperative hospitalization period, advanced age, high ASA score, present comorbidities, extended operation periods and low post-op hematocrit levels.
Mean MMT scores of the patients were significantly lower when compared MMT scores at 24 hours after the operation and initial admission MMT scores, which demonstrated us cognitive dysfunction. In our study, at 24-hour POCD after surgery incidence rate was 43.8%. Our results were similar with the previous studies.
In previous studies reported orthopedic surgeries on elderly patients had a high risk of developing POCD and incidence was reported as 15-60% among especially elderly patients after hip fracture surgery (5, 8).
Advanced age is reported the most important risk factor for developing POCD (9). Elderly patients were reported to have a higher risk of developing POCD compared to younger patients (10, 11). In the study of Salazar including 150 patients reported that POCD incidence rate in patients over 65 was 12% at 4th day after knee replacement surgery (12). In ISPOCD1 study including 1218 patients over 60 who underwent non-cardiac surgery reported POCD incidence rate was 25.8% (13).
We revealed statistical significance between age and POCD development. Mean age of the patients who did not develop POCD in 24 hours was 50.6±21.9 years, while patients who developed POCD, the mean age was 79.0±10.0 years.
The previous studies in the literature also report the ASA risk classification may play an important role on cognitive functions. A study which included 118 patients over 75 who underwent major abdominal surgery reported postoperative delirium in 28 (24%) of the patients and ASA 3 score is one of the risk factors for the development of POCD (14). In our study, Although 46.4% of patients who developed POCD had ASA 1-2 score, 53.6% of had ASA 3 score. Our results are similar with the previous studies which reported a significant association between POCD development and high ASA scores.
Presence of comorbidity, which is one of the most important factors in the assessment of ASA scores, is also reported to be a risk factor in POCD development in various studies (15). In addition, several studies reported association between not only with diabetes and hypertension, but also with coronary artery disease (CAD), congestive heart failure (CHF), respiratory diseases and POCD development (16). In this study, we also found a significant association between presence of comorbidities and POCD development. When comorbidities were classified and evaluated separately, HT and CAD were found to be a risk factor for POCD development. We consider that association between presence of comorbidities and POCD development may be depend on the level of systemic effects of the comorbid disease and duration.
The effect of prolonged preoperative hospitalization period on POCD development was evaluated in this study regardless of the factors such comorbidities and high ASA scores, which might affect the preoperative hospitalization period. Our results showed us that the preoperative hospitalization period is significantly longer in patients who developed POCD compared to other patients, regardless of comorbidity presence and high ASA score factors. Patients without POCD had a lower mean preoperative hospitalization period compared to patients who developed POCD.
There are limited studies in the literature investigating the effect of preoperative hospitalization period on POCD development. In a study including 54 patients reported that even an increase in hospitalization periods from 14 hours to 32 hours could be attributed to delirium development in postoperative period (17). Although POCD and delirium could be clinically similar, they are different diagnoses that should be differentiated properly. Another study performed on elderly patients operated for hip fractures also reported that increased preoperative hospitalization periods could also increase postoperative hospitalization and might cause POCD development in those cases (5).
Most of the important risk factors for POCD development are patient-related and could not be changed. Especially elderly patients with comorbidities and high ASA scores are under a high risk for POCD development. Moreover, POCD could be seen even in postoperative 3rd month in 14% of those patients (18). Since prolonged preoperative hospitalization periods could affect POCD development after surgery, regardless of other factors, we suggest preoperative hospitalization period should be minimized in patients have risk factors for developing POCD.
In the study of Bitsch including 100 operated hip fracture patients reported a severe cognitive dysfunction in 32% of patients. According to this study, age is a risk factor for POCD, in addition to low postoperative hematocrit (Htc) and perioperative transfusion volume (5). According to our study results, postoperative Htc levels had a significant effect on postoperative MMT values similar to Bitsch’ study.
Although blood loss volume and postoperative Htc values might be related with POCD, in our study, we could not observed a significant association between POCD development and total transfused erythrocyte suspension volume, crystalloid and colloid replacement. Erythrocyte and liquid transfusion must be planned according to preoperative Htc values of the patient and his comorbidities which may be related and cause different outcomes among patients with POCD.
In our study, we found a significant association between POCD development and ephedrine administration. Although there are no studies investigating association between ephedrine administration and POCD in such surgeries, we consider that this is probably due to ephedrine-induced hypotension, not ephedrine administration.
There are some studies reported increased POCD incidence rates with prolonged surgery periods (19). In our study, we also observed that the POCD group had a longer operation time compared to the non-POCD group, in accordance with the literature.
Some of the limitations of this study are its low patient population and short-term evaluation of postoperative cognitive functions. Longer follow-up periods in patients with cognitive function assessment will be beneficial for long-term results.