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TECHNOLOGY, COMPUTING, AND SIMULATION

The Effect of Pain on Health-Related Quality of Life in the Immediate Postoperative Period

Christopher L. Wu, MD^*, Mohammad Naqibuddin, MBBS, MPH^*, Andrew J. Rowlingson, BA, Steven A. Lietman, MD, Roland M. Jermyn, BA^*, and Lee A. Fleisher, MD^*,

*Department of Anesthesiology and Critical Care Medicine, Joint Appointment in Medicine (Cardiology), Biomedical Information Sciences and Health Policy and Management, and the Department of Orthopaedic Surgery, The Johns Hopkins Hospital, Baltimore, Maryland

Address correspondence and reprint requests to Christopher L. Wu, MD, The Johns Hopkins Hospital, 600 North Wolfe Street, Carnegie 280, Baltimore, MD 21287. Address email to chwu{at}jhmi.edu

	Abstract

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The hypothesis of this study was to determine if the severity of postoperative pain would affect patients’ health-related quality of life (HRQL) in the immediate postoperative period (within 2 wk of surgery). We designed this study as a prospective, nonrandomized observational trial in a tertiary academic care center. Patients undergoing elective total hip or knee replacement surgery were eligible. Patients received a standardized intraoperative general or epidural anesthetic followed by IV patient-controlled analgesia or patient-controlled epidural analgesia. Short Form (SF)-12, visual analog scores for pain at rest and pain with activity, nausea, and itching were assessed on postoperative days 1–5, 7, and 14. The severity of pain correlated with a decrease in both the physical and mental component of the SF-12. The severity of nausea correlated with a decrease in the mental but not physical component of the SF-12. The severity of itching did not correlate with a change in the SF-12. Our findings suggest that an increase in postoperative pain will decrease a patient’s quality of life in the immediate postoperative period; however, several methodologic issues exist when assessing HRQL in the immediate postoperative period.

IMPLICATIONS: Severity of postoperative pain may affect quality of life

	Introduction

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Health-related quality-of-life (HRQL) consists of a patient’s comprehensive assessment of the medical care received and is being used in outcomes research in anesthesiology (1). HRQL assessments include not only dimensions typically evaluated by health care providers (e.g., physical functioning, mental health, cognitive functioning, and symptoms such as pain, nausea, and headache) but also those not routinely considered but important to patients (e.g., role and social functioning, general health perceptions, sleep, and energy). HRQL is measured with validated questionnaires, which are typically either generic or specific instruments. The assessment of HRQL has been most frequent in chronic disease states and also used to assess the long-term effects of surgery; however, HRQL has not been evaluated in the immediate postoperative period (e.g., within 1–2 wk of surgery).

Optimal control of postoperative pain and side effects is associated with improvements in some "traditional" clinically oriented patient outcomes such as morbidity, development of chronic pain, and patient rehabilitation (1–3); however, the effect of postoperative pain and analgesic medication side effects on HRQL is unclear. Optimizing postoperative analgesia may theoretically improve HRQL, in part through controlling of postoperative pain, minimizing some medication-related side effects (cognitive function), or facilitating patient convalescence (4). As there is no HRQL instrument validated for the immediate postoperative period and there are little data examining the effect of postoperative pain and analgesic medication side effects on HRQL, we performed a prospective observational study using a generic validated HRQL instrument, Short Form-12 (SF-12) (5), to determine if there was a correlation between the severity of symptoms and HRQL in patients undergoing elective total hip or knee replacement.

	Methods

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This protocol was approved by our IRB, and informed consent was obtained for all patients enrolled in this study. The study was designed as a prospective trial. Patients undergoing elective total knee or hip replacement were eligible for this study. Inclusion criteria included age >18 yr, patients receiving either epidural or general anesthesia, and those undergoing elective total knee or hip replacement. Exclusion criteria were age <18 yr of age, emergency surgery, altered mental status, chronic opioid use, allergy to any study medication, and patients scheduled for a postoperative intensive care unit stay.

Patients received a standardized intraoperative general or epidural anesthesia based on patient preference. Blood lost during the perioperative period was replaced with a balanced salt solution, and administration of blood products was at the discretion of the anesthesia team caring for the patient. Use of monitors in addition to those recommended by current American Society of Anesthesiologists guidelines was at the discretion of the anesthesiologist.

For patients receiving general anesthesia, midazolam up to 2 mg was given IV for anxiolysis. General anesthesia was induced with propofol (2–3 mg/kg) with subsequent administration of rocuronium (0.6–1 mg/kg) to facilitate tracheal intubation. The patient’s larynx was subsequently intubated and intraoperative anesthesia was maintained with an opioid (morphine or hydromorphone), nitrous oxide (up to 70%), and isoflurane. Rocuronium was given as needed throughout the case and was reversed with neostigmine (up to 5 mg) and glycopyrrolate (up to 1 mg) at the conclusion of surgery. Afterwards, the patient’s larynx was extubated, and the patient was transported to the recovery room, where patient-controlled IV analgesia (IV-PCA) was started. IV-PCA settings (morphine 5 mg/mL) were as follows: continuous infusion, 0 mg/h; demand dose, 1 mg; lockout interval, 6 min. The IV-PCA was continued until the morning of postoperative day (POD) 2 at which time the patient received sustained-release oxycodone 10 mg orally twice a day with immediate-release oxycodone 5–10 mg orally every 4 h as needed for breakthrough pain.

For patients receiving epidural anesthesia, midazolam up to 2 mg was given IV for anxiolysis. An epidural catheter was inserted under sterile conditions at either the L2-3 or L3-4 interspace through a 17-gauge Tuohy needle after the epidural space was located by the loss-of-resistance technique. After confirming negative aspiration through the catheter and a negative test dose (3 mL of 2% lidocaine with 1:200,000 epinephrine), epidural anesthesia was induced with 15–20 mL of 2% lidocaine with 1:200,000 epinephrine. Intraoperative anesthesia was maintained with either 2% lidocaine with 1:200,000 epinephrine or 0.5% bupivacaine. At the conclusion of surgery, the patient was transported to the recovery room where patient-controlled epidural analgesia (PCEA) was started. PCEA settings (0.0625% bupivacaine with 5 µg/mL fentanyl) were as follows: continuous infusion, 6 mL/h; demand dose, 3 mL; lockout interval, 15 min. The PCEA was continued until the morning of POD 2 at which time the patient received sustained-release oxycodone 10 mg orally twice a day with immediate-release oxycodone 5–10 mg orally every 4 h as needed for breakthrough pain.

Patient assessments included the SF-12 and visual analog scales (VAS) scores for pain at rest, pain with activity, nausea, and pruritus. VAS scores for pain at rest, pain with activity, nausea, and pruritus were obtained every evening during hospitalization. The SF-12 was administered preoperatively and in each evening of PODs 1–5, 7, and 14. The SF-12 survey was modified to reflect the appropriate time frame (daily assessment) (see Appendix). If the patients were discharged from the hospital before the remaining surveys could be administered, patients were called at home at the appropriate time to complete the remaining surveys. During the telephone calls, one interviewer asked questions in a scripted structured interview.

The relationship between the physical and mental subscales of the SF-12 and the severity of pain at rest, pain with activity, nausea, or itching were analyzed with Pearson correlation (best linear fit). A P value 0.05 was considered statistically significant. The composite SF-12 mental and physical components scores were obtained using the SF-12 Version 2.0 (QualityMetric, Lincoln, RI). All analyses were performed using JMP Statistical Discovery Software, Version 4 (SAS Institute, Cary, NC).

	Results

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Of the 41 patients screened, 4 were excluded from consideration for the following reasons: 3 were scheduled for postoperative intensive care unit admission and 1 had an inability to comprehend the questions posed. A total of 37 patients completed the surveys. There was no loss to follow-up. Demographic data are shown in Table 1. Postoperative VAS scores for pain (both at rest and with movement), nausea, and itching are shown in Table 2. Mean perioperative Physical Component Score (PCS) and Mental Component Scores (MCS) of the SF-12 are shown in Table 3.

View larger version (20K): [in this window] [in a new window]   Figure 1. Correlation of the physical component score (PCS) of the Short Form-12 to the severity of pain at rest. Pearson correlation of all data, regardless of time obtained, demonstrating that an increase in pain at rest significantly correlates to a decrease in the PCS (P < 0.01).

View larger version (21K): [in this window] [in a new window]   Figure 2. Correlation of the mental component score (MCS) of the Short Form-12 to the severity of pain at rest. Pearson correlation of all data, regardless of time obtained, demonstrating that an increase in pain at rest significantly correlates to a decrease in the MCS (P < 0.01).

	Discussion

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Although HRQL has been frequently measured in other fields, it is an uncommon outcome measure in anesthesiology-related research. HRQL is a valid outcome measurement in clinical trials and has been used as a longer-term assessment (e.g., months rather than days) in chronic diseases, oncology patients, and after surgical procedures. There are a large number of validated generic and specific instruments available to assess HRQL (7). One of the most commonly used generic instruments is the SF-36 (8) with its abbreviated form, the SF-12, which has been validated against the SF-36 in a number of populations (5). Based on previous experience, we chose to use the SF-12 because of its easy acceptance and ease of completion by the postoperative patient.

There are many physiologic disturbances or complications that may occur in the immediate postoperative period that may interfere with patient recovery. In addition, significant symptom distress (e.g., pain, fatigue, nausea and vomiting) and functional status changes are common in the immediate postoperative period (9,10). These changes may result in a decrease in HRQL (11) by adversely affecting many physical, mental, cognitive, and social dimensions of HRQL and thus influencing the patient’s recovery postoperatively. It would seem plausible that a decrease in postoperative pain and other symptoms would result in improvement in various important dimensions of HRQL in the immediate postoperative period.

We found that the severity of postoperative pain generally correlated with a decrease in the physical component of HRQL as assessed by the SF-12. Longer-term studies in other types of pain have also shown a correlation between increased levels of pain and decreased HRQL (some using both the SF-12 and SF-36) (12–14). It would seem intuitive that poorly controlled postoperative pain could limit physical activity and function and, as a result, decrease the physical component of the SF-12. As would be expected for patients whose physical function is limited to the extent of requiring a hip or knee replacement, the preoperative score of 30.1 ± 6.6 for the PCS is lower than that of a normal population at 50 ± 10 (15). As also might be expected, the PCS scores decreased immediately after surgery and increased beyond the baseline score as patients recovered from surgery and began rehabilitation with their new prothesis (16).

The overall MCS scores were approximately equivalent to a typical mean of a normal population (50 ± 10) (5) and did not appear to change significantly over the 2-week study period; however, we found that the severity of postoperative pain generally correlated with a decrease in the mental component of HRQL. In other settings, poorly controlled pain has been shown to adversely affect mood and energy and, consequently, to decrease HRQL (17). Again, it would seem intuitive that poorly controlled postoperative pain could negatively affect mood and energy and, as a result, decrease the mental component of the SF-12. Although we could determine a significant correlation between an increase in pain and a decrease in HRQL in both the PCS and MCS when evaluating individual data, the overall change in HRQL over time (from the first postoperative through the 14th postoperative day) is actually quite small. It is difficult to determine if patients truly had any global differences in HRQL with these small changes. However, these small changes may also be the result of a lack of responsiveness of a generic instrument such as the SF-12 (which has not been validated in this setting) in the immediate postoperative period.

The lack of effect of nausea (PCS only) and itching on HRQL may be related to the small severity of these symptoms throughout the study period. We did note a significant correlation between the severity of nausea and a decrease in the MCS. The overall mean VAS scores for both nausea and itching were generally <1.5 of 10, whereas the mean pain scores were >3 of 10 in the immediate postoperative period. An increased severity of nausea has been shown to decrease HRQL in other settings (18,19). Although not examined to the extent of nausea and emesis, other symptoms (e.g., itching and sedation) resulting from medication side effects may potentially also decrease HRQL with an increase in severity.

There are several limitations to our study, many of which are related to methodologic issues in measuring HRQL in the immediate postoperative period. The use of the SF-12 has not been validated in the postoperative setting. A closer examination of the SF-12 reveals that some of the items used may not be appropriate for assessment of HRQL in the immediate postoperative period as the SF-12 was designed as a generic not specific measure of HRQL. For example, the physical functioning items, such as "moving a table, pushing a vacuum cleaner, bowling, or playing golf," are unsuitable for patients who most likely would be not be performing these activities during inpatient postoperative recovery. Likewise, certain questions in the role limitations attributable to either physical or mental health may not be appropriate, as patients would not be at work. In addition, the SF-12 has not been validated for use on a daily basis; the most frequent validated use has been on a weekly basis (www.outcomes-trust.org/instruments.htm). Finally, the SF-12 correlated with severity of pain and nausea (MCS only) but not with severity of nausea (PCS only) and itching. Thus, it is unclear if the SF-12 would be valid and reliable in this new setting or be responsive to daily changes in HRQL. The same dilemma will also be encountered with use of any other validated HRQL instruments in evaluating the effect of postoperative pain on HRQL on a daily basis, as these instruments were not designed to assess HRQL in such a short time frame (daily versus weeks). Finally, the significant correlation between a decrease in postoperative pain and improvement in SF-12 HRQL in our study does not prove a causal relationship. Further modeling (20) and testing of such models are needed to validate the effect of pain on HRQL in the postoperative period.

Currently available instruments, as a whole, are not appropriate to assess HRQL in this setting, and development of a new instrument would most likely be necessary to evaluate HRQL immediately after surgery. A new instrument potentially could incorporate some aspects of recently released postoperative recovery instruments (21,22); however, it is not clear whether these truly reflect HRQL. There are several steps during the development phase (specifying measurement goals, item generation, item reduction, and questionnaire formatting) and testing phase (questionnaire pretesting and assessment of reliability, responsiveness, validity, and interpretability) that are required in development of a new instrument to assess HRQL (23).

Acceptance of HRQL measurements in the postoperative setting may be slow because of the lack of validated instruments (including the ability to be responsive to subtle changes occurring on a daily basis postoperatively), information with regard to their value and benefits, and the perception of these measurements as being "soft" or "unscientific" (24). Anesthesiologists and other health care providers who provide care on a more acute basis typically focus on "traditional" outcomes mea-surements (e.g., mortality and morbidity) rather than "nontraditional" outcomes such as HRQL, which in part may be the result of difficulty by many clinicians in conceptualizing the relationship between clinical variables and HRQL and the effect of clinical interventions on HRQL (24). Thus, further modeling of the relationship between individual postoperative symptoms and HRQL and the interaction between symptoms on HRQL in the immediate postoperative period are needed. There are several other general issues (e.g., development of an external "gold standard" against which HRQL instruments could be tested, further development of conceptual models and theories of HRQL, and greater quality control for research in HRQL) that need to be resolved before the widespread use of HRQL becomes widely accepted (25).

In summary, we have performed one of the first trials investigating the effect of pain and side effects from analgesics using a generic HRQL instrument in the immediate postoperative period. We demonstrated that in patients undergoing elective total hip or knee replacement surgery, the severity of postoperative pain correlates with a decrease in HRQL in the postoperative period as assessed by the SF-12, although we have not demonstrated a casual relationship, owing to the observational nature of the study design. The severity of some analgesic side effects assessed (e.g., nausea, itching) did not generally appear to affect HRQL, with the exception of a decrease in the MCS with an increase in the severity of nausea. There are several methodologic issues that need to be considered when interpreting the results of our study and further trials are needed in different surgical populations and different postoperative analgesic regimens to determine the extent of the decrease in HRQL postoperatively.

	Appendix

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View larger version (37K): [in this window] [in a new window]   Appendix. Modified Short Form–12 Survey

View larger version (28K): [in this window] [in a new window]   Appendix Continued

	Footnotes

 
Presented in part at IARS 75th Clinical and Scientific Congress, Ft. Lauderdale, FL, March, 2001.

	References

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Anesthesia & Analgesia® is published for the International Anesthesia Research Society® by Lippincott Williams & Wilkins with the assistance of Stanford University Libraries' HighWire Press®. Copyright 2006 by the International Anesthesia Research Society. Online ISSN: 1526-7598   Print ISSN: 0003-2999