Incidence of early postoperative cognitive dysfunction and other adverse events in elderly patients undergoing elective total hip replacement (THR)

Archives of Gerontology and Geriatrics 53 (2011) 328–333

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Incidence of early postoperative cognitive dysfunction and other adverse events in elderly patients undergoing elective total hip replacement (THR) A. Postler a, J. Neidel b, K.-P. Gu¨nther a, S. Kirschner a,* a b

Department of Orthopaedic Surgery, University Hospital Carl Gustav Carus, Medical Faculty of the Technical University of Dresden, Fetscherstr. 74, D-01307 Dresden, Germany Department of Anesthesia, University Hospital Carl Gustav Carus, Medical Faculty of the Technical University of Dresden, Fetscherstr. 74, D-01307 Dresden, Germany

A R T I C L E I N F O

A B S T R A C T

Article history: Received 30 July 2010 Received in revised form 8 December 2010 Accepted 9 December 2010 Available online 1 February 2011

In elderly patients cognitive dysfunction and other adverse events (AEs) can impair the outcome of surgical procedures. As THR is performed with increasing frequency in aging populations, it is important to know the impact of these problems on the postoperative result. In this prospective cohort study 60 patients older than 65 years (66.7% female, 33.3% male) who received THR were included. The cognitive function was measured preoperatively, one week and six months postoperatively by the mini-mental state test (MMSE). Shortly after surgery 4 patients (6.7%) developed postoperative cognitive dysfunction, which has recovered at six-months-follow-up. In 41 patients (68.3%) AEs were recorded. Postoperative anemia occurred as the most common AE (n = 32; 53.3%). During hospital stay older patients are at an increased risk for AEs. The incidence of postoperative cognitive dysfunction was observed less often than expected. Further research is necessary to assess the effect of early interventions in case of cognitive dysfunction. With use of a simple and quickly performed test like the MMSE patients can be effectively screened for impaired cognitive function. Secure identification of those patients is mandatory to avoid complications with harmful long-term effects. ß 2010 Elsevier Ireland Ltd. All rights reserved.

Keywords: Surgery of aged Frail elderly Postoperative complications Delirium/prevention and control Total hip arthroplasty

1. Introduction THR is a successful treatment for patients with osteoarthritis of the hip after failed conservative treatment (Learmonth et al., 2007). In the past there were great objections against surgical intervention in elderly patients and thus this treatment was chosen very hesitatingly. Studies reported high complication (postoperative dislocation and femoral fractures) and mortality rates (Newington et al., 1990; Ekelund et al., 1992; Whittle et al., 1993; Baron et al., 1996). The patient’s perioperative care has significantly improved, however and current data in the literature support high benefits for quality of life and recovery of self care and independent living, especially for elderly patients after THR (Hamel et al., 2008; Scha¨fer et al., 2010). Several AEs can impair the treatment results. While surgeons are especially afraid of the procedure-specific risks (i.e., infection, dislocation of the prostheses and fractures), other potential AEs are often not addressed as equally important. Postoperative cognitive dysfunction (POCD) for example is relatively frequent after major surgery and can be associated with decline of normal or already

* Corresponding author. Tel.: +49 351 458 4246; fax: +49 351 458 4344. E-mail address: [email protected] (S. Kirschner). 0167-4943/$ – see front matter ß 2010 Elsevier Ireland Ltd. All rights reserved. doi:10.1016/j.archger.2010.12.010

impaired preoperative cognitive function. It can even lead to postoperative delirium, which impairs the healing process and may result in a prolonged hospital stay as well as increased morbidity and mortality. As even a preoperatively existing mild cognitive dysfunction can cause a cognitive decline or delirium, it is necessary to assess the preoperative mental status in order to identify patients who are at risk and to provide successful and safe treatment for them (NIH Consensus Panel, 2004). Aim of the current study was therefore, to evaluate AE in elderly patients after THR and to specifically assess their pre- and postoperative cognitive function. In addition possible influencing factors on cognitive function and the surgical outcomes were evaluated. 2. Subjects and methods 2.1. Study design Upon approval by the ethics commission, a prospective cohort study including 60 elderly patients undergoing elective primary hip arthroplasty was conducted as a pilot study. From February 2008 to April 2009 data were collected at four distinct time points. During their hospital stay the patients were interviewed preoperatively (on the day of admission) and one week postoperatively. Between two and four months after the hospital stay the

A. Postler et al. / Archives of Gerontology and Geriatrics 53 (2011) 328–333

Fig. 1. To assess the patient’s constructional abilities, they are asked to copy these two intersecting pentagons.

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To evaluate and analyze algofunction before and after THR, the HHS modified by Haddad et al. (Harris, 1969; Haddad et al., 1990) was used. Standardized assessment and grading of comorbidities was performed with the Charlson comorbidity index (CCI) (Charlson et al., 1987). For this index, 19 different comorbidities are varied in weights with point values from 1 to 6. The higher the sum of these values, the higher the illness rate, which is associated with four disease ranks: no comorbidity (0 points), mild to moderate comorbidity (1–2 points), moderate to severe comorbidity (3–4 points) or very severe comorbidity (5 points). The CCI is supposed to predict the relative risk for mortality resulting from comorbidity. Assessed perioperative care characteristics included duration of surgery (cut-sew-time), duration of hospital stay, amount of blood loss, noticeable problems during recovery phase after anesthesia and all medical measures including administered medication. Furthermore all AEs appearing during the hospital stay and six months after surgery were recorded according to the guidelines for Good Clinical Practice (GCP) (European Medicines Agency, 1996). 2.4. Statistical methods

questionnaires were mailed to the patients and six months after surgery the patients were invited to a follow-up clinic visit. 2.2. Participants Inclusion criteria for the study were age 65 years or older, severe osteoarthritis of the hip and the patients’ consent to participation. Non-elective surgery, proceeding indemnity claim, sensory perception disorder, diagnosed progressed dementia and thereby resulting inadequate communication ability were be defined as excluding criteria. 2.3. Measurement For each patient sociodemographic characteristics were obtained according to a recommendation of the Robert Koch Institute (Ahrens et al., 1998). Preoperatively as well as one week and six months postoperatively several questionnaires: MMSE, the Barthel index (BI), the European quality of life questionnaire (EQ5D), and the Harris hip-score (HHS) were completed. At discharge information about surgical treatment, medical comorbidities and AEs were collected in a standardized manner. Cognitive function was measured in the present study with the MMSE (Folstein et al., 1975). The MMSE was designed as a screening test to diagnose dementia. It includes items that evaluate different domains of cognitive functioning: orientation in time and space, registration, attention and calculation, recall and language (Fig. 1). The maximum score is 30 points, with normal function present at scores from 27 to 30, mild cognitive dysfunction from 18 to 26, moderate from 10 to 17, and severe cognitive dysfunction with less than 10 points. On the basis of the results for the MMSE there is no limit defined, which enables to make the diagnosis of the POCD clearly. An impairment compared to the preoperative results, however, should be considered as a sign of cognitive dysfunction. As a generic outcome instrument for measuring health-related quality of life the EQ-5D was used (The EuroQol Group, 1990). For assessing the patient’s self care ability the BI was applied (Mahoney and Barthel, 1965). Nursing staff is documenting the need for help in activities of daily living. If all activities are done independently the patient scores 100 points. Patients’ achieving 91–99 points are in mild dependence, 61–90 points in moderate dependence, 21–60 points in severe dependence and 0–20 points in complete dependence.

The sociodemographic characteristics and the hospital course data were descriptively analyzed: mean, percentages, minimal and maximal values. The results for the MMSE, HHS, BI and EQ-5D were analyzed to assess whether cognitive function, algofunction, selfcare ability and health-related quality of life had changed between the preoperative test and the one week and the six month postoperative test. These variables were compared with use of the Wilcoxon test for non-parametric samples. Statistical dependences were measured with the help of Spearman’s rank correlation coefficient to investigate variables that may have influence on the course of hospital stay and AEs. Factors considered were age, gender, education, number of comorbidities and taken drugs, the physical status classification system of the American Society of Anesthesiologists (ASA score) and length of surgical intervention. A p  0.05 was considered significant. All analyses were carried out using the SPSS 16.0. 3. Results 3.1. Participants The mean age of the patients was 76.3 years (ranging 68–88 years) and the majority (66.7%) was of female gender. At time of surgery most of the patients were either married (60%) and lived at home with a cohabitant (56.7%). Most of the patients (60%) completed 8–9 years of schooling, 16.7% obtained a higher education degree, 11.7% high school, 8.3% completed 10 years of schooling and 3.3% received no education (Table 1). 3.1.1. Medication At time of the preoperative examination the patients took on average 4.65 different drugs (0–16), at the first examination postoperatively 7.57 (3–20) and at the time of the outpatient examination 6.13 (1–18). During the first days postoperatively the patients needed more anticoagulant agents, analgesics, proton pump inhibitors and antianemic preparations, which were not continued. 3.1.2. Perioperative care characteristics Of the patients, 48 (80.0%) were admitted to the hospital one day preoperatively, the other 12 (20%) on the day of surgery; 34 patients (56.7%) received a cemented THR, 24 (40%) a hybride THR and one patient a cementless THR. A lateral surgical approach was

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Table 1 Sociodemographics and comorbidities of the patient cohort, n (range) or n (%). Patients Age (years) Gender female male ASA ASA II ASA III Not classified Education None 8–9 years 10 years High school More than high school Marital status Married Widowed Single Divorced Housing With cohabitant Alone With children

The patients were hospitalized on average 10.37 days (6–74 days), two of them longer than 14 days. After discharge, 53 patients were transferred to an inpatient rehabilitation unit with a mean treatment duration of 20.9 days (19–27 days).

76.32 (68–88) 40 (66.7) 20 (33.3)

3.1.3. Six-month follow-up Six months postoperatively, 55 patients attended the clinical follow-up investigation. Five patients did not return to the visit, therefore, only data from the assessment one week postoperatively was included in the analyses.

36 (60.0) 22 (36.7) 2 (3.3) 2 (3.3) 36 (60.0) 5 (8.3) 7 (11.7) 10 (16.7)

3.2. Descriptive data 3.2.1. Cognitive function The mean MMSE score declined from a mean preoperative value of 27.4 (22–30) to 26.8 (16–30) at one week and then reached 28.0 (21–30) at six months (Table 2). The improvement of 0.65 points between preoperatively and six months postoperatively is statistically significant (p = 0.003). Thirty of the 55 patients who could be investigated six months postoperatively, had a higher MMSE score at that time than preoperatively. Two patients showed a moderate cognitive dysfunction (<18), one patient a mild dysfunction (18) and the other patient a normal function (29) one week after surgery. The preoperative MMSE in those four patients were 27, 28, 22 and 30, respectively.

36 (60.0) 19 (31.7) 4 (6.7) 1 (1.7) 34 (56.7) 21 (35.0) 5 (8.3)

Comorbidities Number of comorbidities CCI Cumulative index rating scale (CIRS) Arterial hypertension Diabetes mellitus Cardiac arrhythmia Hyperlipidemia Hypothyroidism Cardiac defect Depression Condition after TIA/stroke Chronic compensated renal insufficiency COPD

4.08 (1–9) 1 (0–9) 21 (15–29) 53 (93.3) 22 (36.7) 20 (33.3) 17 (28.3) 11 (18.3) 9 (15.0) 7 (11.7) 6 (10.0) 5 (8.3) 4 (6.7)

3.2.2. Algofunction, independence and quality-of-life After THR, a significant improvement of HHS, as well as EQ-5D could be noted (Table 2). The improvement in the patients’ self care ability was shown in the BI with an improvement of 1.67 points (p = 0.013) six months postoperatively. 3.2.3. AEs A total of 58 AEs was recorded in 41 patients: 19 patients (31.7%) did not show any AE. While most of the AEs were mild (8.3%) or moderate (73.3%), nine patients (15%) showed a severe AE (Table 3). The most common complication was postoperative anemia (32 patients) followed by decubitus (5 patients) and POCD (4 patients). In 16.7% of all AE cases no intervention at all was necessary, 48.3% of the patients needed blood transfusion in the postoperative course. After discharge only one serious AE was recorded (readmission due to dislocated THR).

used in 53 patients (88.3%), in 7 patients (11.7%) the operation was performed through an anterolateral approach. General anesthesia was used in 40 patients (66.1%) during surgery, 20 patients (33.3%) had spinal anesthesia. The mean duration of surgery was 101.07 min (63–175 min), the average blood loss was 1818.73 ml (0–5330 ml) as documented in the anesthesia protocols. During the recovery phase after anesthesia, 22 patients showed no noticeable problems, 17 patients (29.8%) needed oxygen therapy and one patient (1.8%) had a disorder of orientation postoperatively. One patient (1.8%) received one blood transfusion immediately after surgery due to an intraoperatively high blood loss, further 26 patients received in median on the first day postoperatively (0–9 days) two (1–5) blood transfusions, two of them after preoperative autologous blood donation. Of the patients, 59 (98.3%) returned postoperatively to the regular ward, one patient was observed on intensive care unit for one night before returning to regular ward.

3.3. Factors influencing POCD 3.3.1. Explorative analysis of correlation The MMSE score showed a significant association with two factors: patients with higher age seem to have a more severe cognitive dysfunction both before and after surgery (1. r = 0.301; p = 0.019, 2. r = 0.495; p < 0.001). The duration of education correlates positively with the MMSE values at every time of recording (1. r = 0.469; p < 0.001; 2. r = 0.306; p = 0.018; 3.

Table 2 Means of the score results at the different times of recording; results of the Wilcoxon test, mean (range). Score

1

2

3

D1–2

D2–3

D1–3

MMSE (max.: 30)

27.37 (22–30)

26.77 (16–30)

28.02 (21–30)

0.6 p = 0.116

+1.25 p = 0.001

+0.65 p = 0.003

EQ-5D scale (%) (max.: = 100)

48.75 (10–80)

59.25 (30–85)

64.83 (20–90)

+10.5 p < 0.001

+5.58 p = 0.013

+16.08 p < 0.001

BI (max.: = 100)

96.58 (80–100)

75.42 (10–95)

98.25 (75–100)

21.16 p < 0.001

+22.83 p < 0.001

+1.67 p = 0.013

HHS (max.: = 100)

43.42 (22–67)

48.70 (20–74)

77.08 (32–97)

+5.28 p = 0.008

+28.38 p < 0.001

+33.66 p < 0.001

Notes: 1: preoperatively; 2: one week postoperatively; 3: BI and EQ-5D 3 months postoperatively, MMSE and HHS 6 months postoperatively; D = difference.

A. Postler et al. / Archives of Gerontology and Geriatrics 53 (2011) 328–333 Table 3 AEs reported according the GCP guidelines, n (%). Type of AE Postoperative anemia Decubitus POCD Cardiovascular Metabolical Fracture Luxation Other Intensity of AE Mild Moderate Severe

Causal connection to surgery 32 (53.3) 5 (8.3) 4 (6.7) 4 (6.7) 2 (3.3) 2 (3.3) 1 (1.7) 8 (13.3)

Yes Probably Probably Probably Possible Yes Yes

5 (8.3) 44 (73.3) 9 (15)

r = 0.412; p = 0.002). Patients who suffered from POCD in the first postoperative week achieved significantly lower scores in the BI (p = 0.028) at that time (see Table 2). In further explorative analysis was shown that patients with a higher number of comorbidities had a longer time of inpatient stay. A higher value of self care (BI) is associated with a significantly shorter time of inpatient stay. The ASA score, measured preoperatively, correlates positively with the occurrence of postoperative anemia (Table 4). 4. Discussion The changing demographics (Federal Statistical Office of Germany, 2009), which implies an increasing number of elderly and very old age people in the overall population, is also reflected in the changing of the medical clients: the fraction of elderly patients with degenerative joint diseases is increasing and thereby the number of primary joint replacement and revision replacement is also increasing (Lawrence et al., 1998; Iorio et al., 2008). The overall postoperative improvement of functional results and health-related quality-of-life measures is impressive in young patients (Laupacis et al., 1993; Ritter et al., 1995). It can also be reproduced in elderly patients, as our study as well as other investigations have shown (Hamel et al., 2008; Scha¨fer et al., 2010). The success of treatment, however, can be threatened by the occurrence of an AE. In 68.3% of our patients an AE was recorded postoperatively. The most common AE was postoperative anemia, which can adequately be treated by blood transfusion. Because of reduced physiological reserves and a disorder of hematopoiesis, the elderly population is vulnerable to milder degrees of anemia when undergoing surgery (Eisenstaedt et al., 2006). The preoperatively measured concentration of oxyhemoglobin was found as a valid measure to indicate a postoperative blood transfusion after hip or knee arthroplasty (Guerin et al., 2007). In addition to the preoperatively measured concentration of oxyhemoglobin, Salido et al. (2002) described patients’ lower weight as a

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prognostic factor for postoperative blood transfusion after hip or knee arthroplasty. Considering the patients’ physiological transfusion triggers (Executive Committee of the German Medical Association on the recommendation of the Scientific Advisory Board, 2009), transfusing elderly patients should be indicated to prevent perioperative cardiac ischemic events and improve their exercise tolerance and facilitating functional recovery (Lawrence et al., 2003). There were noticed large volumes of blood loss, in average 1818.73 ml, which is combined from intraoperative blood loss and amount of the wound drainage. One patient who suffered from a periprothetic fracture had the highest blood loss (5330 ml) and was treated by blood transfusion. A consecutive surgical intervention was not necessary. Important risk factors for the occurrence of adverse advents are long operation time, high number of currently taken drugs, preexisting cognitive dysfunction and higher age. Our results indicate that a high ASA score and a low HHS preoperatively also correlate with the number of AEs. The number and intensity of preoperative existing comorbidities are also considered as a risk factor for postoperative complications (Greenfield et al., 1993). An instrument to assess the severity of comorbidities is the CCI, by means of a longitudinal study with 685 patients suffering from breast cancer to predict the risk of death from comorbid diseases. Significant correlations were described between the results of the CCI and mortality, the loss of autonomy, readmission to the hospital and duration of stay in the hospital (DeGroot et al., 2003). In the present study the CCI was used to quantify patients’ comorbidities retrospectively after recording all comorbidities. According to the CCI, 17 patients (28.3%) had no comorbidity, 28 (46.7%) had mild to moderate comorbidities, 11 (18.3%) moderate to severe and 3 (5%) had very severe comorbidities. Patients with more severe comorbidities are in more dependence on care. The CCI showed a significant association with the BI preoperatively and six months postoperatively (p < 0.05). Between the CCI and the MMSE, there could not be found any significant association. The BI is advised as a valid and reliable measurement (Hofmann et al., 1995). Indeed, it is checked for these criteria in just few studies (Collin et al., 1988; Nikolaus, 2001). Disadvantages of the BI are that the classification criteria for the several categories are vaguely described and to classify modern care methods is difficult practically. A complementary support is the Hamburg classification manual (Federal Association of Clinical Geriatric Departments, 2002; Lubke et al., 2004). Advantages are that the test could be performed easily and quickly. Furthermore the BI is appropriate to various patients and provides to evaluate the course of patients’ independence in activities of the daily living. This could be confirmed by significant differences between the preoperative and the postoperative values, which were found in the present study (p < 0.05). Between the BI and the MMSE, there were no significant correlations detected in the course of

Table 4 Explorative analysis of correlation.

Correlation analysis Age Gender Number of comorbidities ASA score Number of taken drugs 1 Length of surgical intervention a * **

Adverse events

p.o. blood anemia

Duration of hospital stay

HHS 1

HHS 3

EQ-5Da 1 (scale)

EQ-5D 3 (scale)

n.s. n.s. n.s. 0.492** 0.386** n.s.

n.s. n.s. n.s. 0.302* n.s. n.s.

n.s. n.s. 0.344** n.s. n.s. n.s.

n.s. n.s. 0.280* n.s. n.s. n.s.

n.s. n.s. n.s. n.s. n.s. n.s.

n.s. n.s. 0.272* n.s. 0.265* n.s.

0.293* n.s. 0.324* n.s. n.s. n.s.

EQ-5D scale: state of health, subjectively assessed 0–100%. p < 0.05. p < 0.01.

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every distinct time point. However, assuming that association between these two scores is verifiable, there should be searched for in studies with a higher number of cases and more severe manifestation of the POCD. Four of our patients (6.7%) showed clinical signs of POCD. This is a potentially serious AE, but our observed incidence falls below the previously reported incidences (Williams-Russo et al., 1992; Moller et al., 1998). Inouye et al. (2001) reported in a study with 797 patients aged 70 years, a frequency of 16%. She is pointing out, however, the problem of underestimation due to inadequate identification and diagnosis especially by nursing staff (Inouye et al., 2001). It is important, therefore, to train the nursing staff and to apply adequate screening tools. The MMSE is a suitable instrument to assess patients’ cognitive function, as only a short time is needed to perform the test (5– 10 min). Due to it’s high learning effect the MMSE is not suggested for mentoring, however (Folstein et al., 1975; Anthony et al., 1982). Another problem is that this test is evaluating the cognitive function at the time of examination only and therefore the occurrence of a POCD at another time cannot be detected. Several risk factors for cognitive dysfunction can be identified (i.e., higher functional disability, higher number of comorbidities, existing dementia or impairment of the ability to see (Inouye et al., 2006, 2007). The present study could show that a higher age (p < 0.001) has a negative effect on the patient’s cognitive function, whereas a higher level of education (p < 0.001) seems to correlate positively. Our study design has several limits. The data were mainly collected by interviews, so it should be adopted that the patients may have been influenced in their responses (reporting bias, recall bias). Because of the monocentric conducted pilot study the number of cases was limited to 60 patients so that the study has a low power to detect significant risk differences. In future studies with higher number of cases the patient’s cognitive function should be measured in shorter intervals postoperatively. Another drawback is the relatively short followup of six months postoperatively. This is the most important time, however, where relevant complications and AEs do occur. In spite of these limitations, we believe that it is important to identify risk factors for the development of AEs in general and specifically of POCD after THR. Appropriate instruments are available to detect patients who are at risk. In addition new approaches for reducing the AEs appear like preoperative carefully performed preparation for the surgery (individual comorbidity profile, choice of anesthetic method, change of medication). In the literature it is described that older patients profit from an intensive care by few alternating nursing staff, best by geriatric nurses (Gurlit and Mo¨llmann, 2008). Additional prevention measures should include an intensive communication for improving the orientation, early mobilization of the patients, avoidance of sedatives and hypnotics, sufficient liquids and nutrition, visual and hearing aid and optimal pain therapy (Young and Inouye, 2007). 5. Conclusion The present study shows that elderly patients undergoing elective THR suffer from fewer AEs than expected. Although the frequency of POCD is not very high in this unselected cohort of elderly patients, this complication can lead to relevant problems. With use of a simple and quick test like the MMSE patients with an impaired cognitive function can be screened successfully prior to surgery and shortly afterwards. By extending observation of relevant process parameters the outcome of elderly patients in the orthopedic surgery could be improved in the future.

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