Kuang-Yi Chang

Factors Affecting Patient-controlled Analgesia Requirements

BACKGROUND/PURPOSEnIntravenous patient-controlled analgesia (IVPCA) is one of the most widely used postoperative analgesic methods. Many factors could affect the total analgesic consumption of IVPCA. This retrospective study investigated the relationship between patient characteristics and total morphine consumption during a 3-day course of postoperative IVPCA.nnnMETHODSnPatients receiving surgery under general anesthesia with postoperative IVPCA for 3 days during the period between January 2002 and December 2003 were included. Patient data including age, sex, weight, height, body mass index (BMI), operation type and site were collected. Total morphine consumption was recorded at the end of the 3-day IVPCA course. Stepwise regression analyses were conducted to select factors significantly associated with morphine consumption. Stratified analyses were also conducted among different surgical, BMI and age subgroups.nnnRESULTSnA total of 1308 patients (646 men, 662 women) were included in the analysis. For all operations, weight, age, procedures involving malignant disease, and surgical sites were significantly associated with total morphine consumption. The R and adjusted R2 values of the selected model were 0.509 and 0.256, respectively. Weight was the only common factor among all stratified analyses (all p < 0.001). Age was negatively correlated with morphine consumption. Gender was not a significant factor except in lower abdominal operations. Height was not associated with total morphine consumption. BMI status was not significantly associated with components of the selected factors.nnnCONCLUSIONnThis study demonstrated that weight and surgical sites significantly influence total IVPCA requirements. The effect of surgical sites should be considered when evaluating the influence of demographic characteristics on IVPCA demand.

Gastroesophageal Reflux Disease and Sleep Quality in a Chinese Population

BACKGROUND/PURPOSEnAlthough evidence suggests that gastroesophageal reflux disease (GERD) may interrupt sleep, the effects of symptomatic and endoscopically diagnosed GERD remain elusive because the patient population is heterogeneous. Accordingly, we designed a cross-sectional study to assess their association.nnnMETHODSnConsecutive participants in a routine health examination were enrolled. Definition and severity of erosive esophagitis were assessed using the Los Angeles classification system. Demographic data, reflux symptoms, sleep quality and duration, exercise amount, alcohol consumption, and smoking habits were recorded. Factors affecting sleep quality and sleep duration were revealed by a polytomous logistic regression analysis.nnnRESULTSnA total of 3663 participants were recruited. Subjects with reflux symptoms, female gender, higher body mass index, and regular use of hypnotics had poorer sleep quality. Exercise was associated with better sleep quality. Either symptomatically or endoscopically, GERD did not disturb sleep duration. Among the 3158 asymptomatic patients, those with erosive esophagitis were more likely to have poor sleep quality. The risk increased with the severity of erosive changes (p = 0.03).nnnCONCLUSIONnThe present study highlights the adverse effect of gastroesophageal reflux on sleep, even in the absence of reflux symptoms. This finding has therapeutic implications in patients with silent erosive disease, and future trials are warranted.

Statistical item analysis of the examination in anesthesiology for medical students using the Rasch model

Background: Test evaluation in a clinical curriculum is important for medical education. To identify examinee ability and appropriateness of the test content, this study used the Rasch model to analyze an examination in anesthesiology for medical students. Methods: Fifty items were administered to 119 fifth‐ and sixth‐year medical students in the exam. The Rasch model was used to perform item analysis of the examination. Misfit items or examinees were excluded first, then test reliability was assessed with reliability indices. Both examinee ability measures and item difficulty were estimated and expressed in a common logit unit, which could be further translated into probability of correct responses in the examination. Results: After the exclusion of two misfit items and one misfit examinee, the estimated test reliability was only 0.63. The mean item difficulty was set at 0 by definition (SD = 2.02) and the mean examinee ability was 1.56 (SD = 0.71), which means that the examinees were able to correctly answer 83% of items on average. There were 21 items with difficulty lower than the least able examinee and two items with difficulty higher than the most able one. Conclusion: We demonstrated that statistical item analysis with the Rasch model could provide valuable information related to test reliability, item difficulty and examinee ability, which could be applied to further item modification and future test development of clinical curriculums for medical students.

Patients and surgery-related factors that affect time to recovery of consciousness in adult patients undergoing elective cardiac surgery

Background: Central nervous system dysfunction is a serious complication following cardiac surgery. The prompt and predictable recovery of consciousness (ROC) from anesthesia is essential for neurological evaluations. This retrospective study aimed to determine the factors that were related to ROC time after elective cardiac surgery. Methods: Patients receiving elective cardiac surgery under general anesthesia were included in the analysis. Patient and surgery‐related factors were collected through chart review. Cox regression model was used to evaluate the associations between collected variables and ROC time. Backward model selection strategy was further applied to selecting independent factors from significant ones that affected ROC time in the univariate analysis. Results: A total of 253 patients were recruited in our study. Among significant patient characteristics, higher body mass index (hazard ratio, HR = 1.06) and female gender (HR = 1.72) tended to shorten ROC time, but older age was inclined to prolong it (HR = 0.98). Higher preoperative blood urea nitrogen level also significantly delayed ROC after cardiac surgery (HR = 0.99). Among surgery‐related factors, only longer duration of cardiopulmonary bypass significantly increased ROC time after the model selection processes (HR = 0.96). Other factors were not significant after adjustment for these five factors. Conclusion: This study demonstrated that older age, male gender, lower body mass index, higher preoperative blood urea nitrogen level, and longer bypass duration were independent risk factors of delayed emergence after elective cardiac surgery. These findings provide insights into patient care and anesthetic management for clinicians in related fields.

Factors associated with vomiting in orthopedic patients receiving patient-controlled epidural analgesia.

BACKGROUNDnAlthough patient-controlled epidural analgesia (PCEA) can effectively relieve postoperative pain in orthopedic patients, some adverse effects are still troublesome. We conducted this study to survey the possible risk factors related to vomiting induced by PCEA.nnnMETHODSnThis retrospective study was conducted to review orthopedic patients receiving postoperative PCEA. The agent for PCEA was bupivacaine prepared as a 0.1% solution with added fentanyl (1 microg/mL). Patients characteristics including demographic data and types of surgical procedures were collected. All patients were dichotomized into vomiting and non-vomiting groups and subgroup comparisons were also performed. Stepwise logistic regression analyses were conducted to determine significant factors associated with vomiting in these patients.nnnRESULTSnThere were 320 patients (111 men, 209 women) included in the analysis. No significant differences in demographic data were noted between the groups except in sex distribution. Factors related to surgery, anesthesia and PCEA were similar between groups (p > 0.05 in all). The incidence of vomiting for orthopedic patients receiving PCEA was about 9.7% (12.4% for female, 4.5% for male). After stepwise model selection, we found female sex was the only risk factor of vomiting. The odds ratio of vomiting for female gender was 3 (95% confidence interval, 1.1-8.1). General anesthesia was not associated with vomiting in these patients.nnnCONCLUSIONnOur study demonstrated the risk factor associated with vomiting for orthopedic patients receiving PCEA was female sex. Other demographic variables and factors related to surgery or anesthesia did not have an influence on vomiting.

Decision Analysis for a Data Collection System of Patient-controlled Analgesia With a Multi-attribute Utility Model

Background: Data collection systems are very important for the practice of patient‐controlled analgesia (PCA). This study aimed to evaluate 3 PCA data collection systems and selected the most favorable system with the aid of multiattribute utility (MAU) theory. Methods: We developed a questionnaire with 10 items to evaluate the PCA data collection system and 1 item for overall satisfaction based on MAU theory. Three systems were compared in the questionnaire, including a paper record, optic card reader and personal digital assistant (PDA). A pilot study demonstrated a good internal and test‐retest reliability of the questionnaire. A weighted utility score combining the relative importance of individual items assigned by each participant and their responses to each question was calculated for each system. Sensitivity analyses with distinct weighting protocols were conducted to evaluate the stability of the final results. Results: Thirty potential users of a PCA data collection system were recruited in the study. The item “easy to use” had the highest median rank and received the heaviest mean weight among all items. MAU analysis showed that the PDA system had a higher utility score than that in the other 2 systems. Sensitivity analyses revealed that both inverse and reciprocal weighting processes favored the PDA system. High correlations between overall satisfaction and MAU scores from miscellaneous weighting protocols suggested a good predictive validity of our MAU‐based questionnaire. Conclusion: The PDA system was selected as the most favorable PCA data collection system by the MAU analysis. The item “easy to use” was the most important attribute of the PCA data collection system. MAU theory can evaluate alternatives by taking into account individual preferences of stakeholders and aid in better decision‐making.

Item response analysis on an examination in anesthesiology for medical students in Taiwan: A comparison of one- and two-parameter logistic models

Background: Student examinations are an essential component of medical education and item analyses are important to assess test quality. Among miscellaneous psychometric theories used for test analyses, item response theory is more flexible and versatile than other theories. This study aimed to apply item response models to analyze an anesthesiology examination for medical and dental students. Methods: This examination included 50 items that were administered to 170 5th‐ and 6th‐year medical and dental students. One‐ and two‐parameter logistic (1‐PL and 2‐PL) item response models were used to conduct item analyses of the examination. Fit statistics were examined to exclude misfit items and evaluate test reliability. Goodness‐of‐fit analyses were used to select the model having the better fit to data. Examinees ability and item difficulty were estimated and then expressed on the common scale. Potentially differential items were detected using logistic regression. Results: The goodness‐of‐fit analysis revealed that, in our case, the 1‐PL model was more suitable for item response analyses. No misfit item was noted and the test reliability was 0.81 (1‐PL model). The mean examinees ability was set at 0 by definition [standard deviation (SD) = 0.61] and the mean item difficulty was −2.08 (SD = 1.93). There were 24 items with a difficulty level lower than the least able examinee, and three items had a difficulty level higher than the most able examinee. Four potentially differential items were identified. Conclusion: Item response models are useful for medical test analyses and provide valuable information about model comparisons and identification of differential items other than test reliability, item difficulty, and examinees ability.

To add or not to add? An empirical study on droperidol and intravenous patient-controlled analgesia

Background: Droperidol is commonly added to intravenous patient‐controlled analgesia (IVPCA) regimens as an antiemetic agent. Although some studies have demonstrated its safety and efficacy, it is not clear whether adding droperidol to IVPCA infusate without an extra loading dose can effectively reduce the incidence and severity of postoperative nausea and vomiting (PONV) in real‐life clinical settings. Methods: Patients receiving IVPCA in this retrospective survey were classified into two groups based on their IVPCA regimens. The droperidol group used morphine 1 mg/mL with droperidol 50 μg/mL, and the non‐droperidol group was given morphine 1 mg/mL alone. The incidence and severity of PONV were compared between the two groups during the 3‐day course of IVPCA treatment using logistic regression and ordinal logistic regression. Propensity score methodology was applied to adjust for potential confounders. Results: Among the 186 patients enrolled, 94 patients received IVPCA with droperidol, and 92 patients received a pure morphine solution. There was no significant difference in patient attributes between the two groups. On the 1st postoperative day, there was no significant difference in incidence or severity of PONV between the two groups. From the 2nd day onward, the patients in the droperidol group had significantly fewer and less severe episodes of PONV (relative risk 0.34 and 0.31, respectively). The overall effects of droperidol on PONV and its severity during the whole IVPCA course were also statistically significant, whether or not adjustment for propensity score was made. However, although a statistically significant decrease in nausea was observed in the droperidol group after the 1st day, no significant difference in the incidence of vomiting between the two groups was noted during the study. Conclusion: A loading dose should be considered on the 1st postoperative day. Our study suggests just how beneficial droperidol can be to IVPCA users in practical clinical settings, showing that droperidol can reduce with some significance the amount and severity of nausea suffered by patients postoperatively, even if the frequency of patient vomiting remains unchanged.

Risk factors of vomiting among females on patient-controlled epidural analgesia.

Background: Postoperative pain and postoperative vomiting (POV) are both sources of distress in the postoperative period. Patient‐controlled epidural analgesia (PCEA) is used in patients undergoing lower extremity surgery to improve postoperative quality but is accompanied by a certain incidence of vomiting. We wanted to determine the risk factors of POV in patients using PCEA with the aim of improving the quality of the postoperative period. Methods: We conducted a retrospective study to analyze the risk factors among patients using PCEA after lower‐limb surgery under regional anesthesia. A total of 195 patients (91 males, 104 females) were enrolled. They were categorized into 2 groups: vomiting and non‐vomiting. We found that female gender predominated in the vomiting group. Hence, we analyzed the female subgroup in order to find the risk factors of vomiting in the female PCEA population. Results: Female gender was the most significant factor related to vomiting (crude OR, 11.55; 95% CI, 4.88–27.33). From analysis of the female subgroup, puncture site (OR, 4.07; 95% CI, 1.41–11.79), catheter length in the epidural space (OR, 0.28; 95% CI, 0.16–0.50) and patients height (OR, 1.07; 95% CI, 1.00–1.14) were also factors for vomiting, i.e. higher epidural catheter puncture site, shorter length in the epidural space, and greater height caused a higher incidence of POV. Conclusion: The most important risk factor for POV in patients using PCEA was female gender. Among the female subgroup, the risk factors for POV included higher epidural catheter puncture site, shorter length in the epidural space and greater body height.

The Relationship Between Lockout Interval and Requirement for Patient-controlled Epidural Analgesia

BACKGROUNDnPatient-controlled epidural analgesia (PCEA) with background infusion provides better analgesia than the use of a demand dose alone but might be associated with more consumption of PCEA solution and adverse effects. Therefore, we conducted this retrospective study to evaluate the influence of parameters of the drug delivery system on the PCEA requirements of patients receiving thoracic or upper abdominal surgeries.nnnMETHODSnPatients having operations involving the chest or upper abdomen with postoperative PCEA were included in the analyses. A standardized analgesic solution of bupivacaine (0.0625%) and fentanyl (1 microg/mL) was used for all patients. The cumulative doses of PCEA on the first, second and third postoperative days were recorded. Collected data included patient demographics and their quantity of PCEA. A general linear model was used to compare within-subject time effects and between-subject effects. Interactions with time between subjects were also examined.nnnRESULTSnA total of 228 patients (68 females, 160 males) were included in the study. The PCEA requirements decreased gradually over time (p < 0.001). Patients with lower body mass index had a greater difference in their PCEA requirement between the first and second postoperative days (p < 0.001). For variables related to PCEA usage, patients using PCEA with the 30-minute lockout interval used less PCEA infusate per day (p = 0.04 for main effect, p = 0.02 for interaction with time). Moreover, a longer lockout interval was not associated with poorer analgesic effects (p = 0.48). Other parameters had no significant influence on daily PCEA requirements.nnnCONCLUSIONnPatients receiving PCEA with a 30-minute lockout and background infusion used the least amount of PCEA infusate and the differences increased over time. Further investigations are recommended to evaluate potential benefits and drawbacks of a longer lockout interval.