title: Patient-machine interactions of intravenous patient-controlled analgesia in bilateral versus unilateral total knee arthroplasty: a retrospective study.
abstract: BACKGROUND
  Continuous passive motion after a major knee surgery optimizes functional prognosis, but causes severe pain. In this study, we assessed the effect of intravenous patient-controlled analgesia (IVPCA) on postoperative pain management in unilateral and bilateral total knee arthroplasty (TKA).
  
  
  METHODS
  Data were collected retrospectively from a single medical center from March 2003 to October 2007. All patients who had undergone TKA were given general anesthesia, and the type of surgery that each patient received was planned according to individual needs. A total of 223 patients qualified for this study, with 174 patients in the unilateral TKA group. Data on patient demography, pain scores, and side effect scores were collected. Total dose consumption, demand, delivery doses, demand-to-delivery ratio, and infusion rate were collected from PCA machines and analyzed.
  
  
  RESULTS
  The patient pain score and patient satisfaction showed no significant difference between the unilateral and bilateral TKA groups. The incidence of sedation (p < 0.001), nausea (p = 0.013), and vomiting (p = 0.044) during the postoperative 24-48-hour period was higher in the bilateral TKA group. Compared with the patients in the unilateral group, those in the bilateral group showed significantly greater dose consumption during the postoperative 6-12-, 12-18-, and 18-24-hour periods. They also showed more demand for medication during the postoperative 12-18- and 18-24-hour periods and received more bolus doses during the postoperative 12-18-, 18-24-, and 30-36-hour periods. In addition, there was also a significantly higher demand-to-delivery ratio for patients in the bilateral group during the postoperative 6-12-, 12-18-hour periods.
  
  
  CONCLUSIONS
  In this study, we successfully demonstrated that our IVPCA protocol can provide adequate analgesia for patients after both bilateral and unilateral TKA. However, sedation, nausea, and vomiting occurred more frequently during the postoperative 24-48-hour period in patients who underwent bilateral than unilateral TKA. This may due of the increased number of bolus doses administered to the patients in the bilateral TKA group during the postoperative 12-18, 18-24, and 30-36-hour periods. Therefore, the initial infusion rates for patients undergoing bilateral TKA could be set at a lower threshold in order to reduce the incidence of these side effects.
authors.affiliation: Department of Anesthesiology, Taipei Veterans General Hospital, Taipei, Taiwan, ROC.
authors.forename: Yu-Chieh
authors.initials: YC
authors.lastname: Wang
authors.forename: Wei-Nung
authors.initials: WN
authors.lastname: Teng
authors.forename: I-Ting
authors.initials: IT
authors.lastname: Kuo
authors.forename: Kuang-Yi
authors.initials: KY
authors.lastname: Chang
authors.forename: Wen-Kuei
authors.initials: WK
authors.lastname: Chang
authors.forename: Mei-Yung
authors.initials: MY
authors.lastname: Tsou
authors.forename: Kwok-Hon
authors.initials: KH
authors.lastname: Chan
authors.forename: Chien-Kun
authors.initials: CK
authors.lastname: Ting
mesh_terms: D000368:Aged; D016058:Analgesia, Patient-Controlled; D019645:Arthroplasty, Replacement, Knee / Q000009:adverse effects / Q000379:methods*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D012189:Retrospective Studies