title: Effect of varying intravenous patient-controlled analgesia dose and lockout interval while maintaining a constant hourly maximum dose.
abstract: OBJECTIVE
  To investigate the effect on the use of intravenous patient-controlled analgesia (PCA) of varying the dose (D) and lockout interval (LI) while keeping the hourly maximum dose constant.
  
  
  METHODS
  Randomized, prospective study.
  
  
  METHODS
  Teaching hospital.
  
  
  METHODS
  75 patients scheduled to receive PCA morphine following abdominal surgery.
  
  
  METHODS
  Postoperatively, patients were randomly assigned to receive PCA morphine with the following parameters: D = 1 mg, LI = 6 min (Group 1-6), D = 1.5 mg, LI = 9 min (Group 1.5-9), or D = 2 mg, LI = 12 min (Group 2-12), so that each group could receive a maximum hourly dose or 10 mg. Inadequate analgesia was managed by increasing the dose and lockout interval, while excessive sedation or respiratory rate less than 10 breaths/min resulted in decreasing the dose and lockout interval.
  
  
  RESULTS
  Patients were assessed for pain [visual analog scale (VAS), verbal rating scale (VRS)] and side effects at 1, 2, 4, and 24 hours. The number of doses administered, missed attempts, and morphine used for the first 24 hours was recorded by automatic printout from the PCA machine. There was no difference in the total 24-hour morphine consumption, analgesia, or incidence of side effects among the three groups at any of the measurement times. Two patients, one each in the 1.5-9 and 2-12 groups, required naloxone for respiratory depression. The number of PCA injections, attempts, missed attempts, and the incidence of dosage adjustment were all significantly higher for the 1-6 group (p < 0.05).
  
  
  CONCLUSIONS
  The use of 1.0 mg with a 6-minute lockout may represent appropriate dose titration because this group obtained equivalent analgesia, morphine use, and side effects as the two larger dose and lockout groups. However, the increased number of PCA attempts and missed attempts may reflect lower satisfaction with PCA therapy.
authors.affiliation: Department of Anaesthesia, London Health Sciences Center, University of Western Ontario, Canada.
authors.forename: N H
authors.initials: NH
authors.lastname: Badner
authors.forename: J A
authors.initials: JA
authors.lastname: Doyle
authors.forename: M H
authors.initials: MH
authors.lastname: Smith
authors.forename: I A
authors.initials: IA
authors.lastname: Herrick
mesh_terms: D000005:Abdomen / Q000601:surgery; D000328:Adult; D016058:Analgesia, Patient-Controlled / Q000379:methods; D000701:Analgesics, Opioid / Q000008:administration & dosage* / Q000009:adverse effects; D000704:Analysis of Variance; D003243:Consciousness / Q000187:drug effects; D005260:Female; D006801:Humans; D015994:Incidence; D007275:Injections, Intravenous; D008297:Male; D008875:Middle Aged; D009020:Morphine / Q000008:administration & dosage* / Q000009:adverse effects; D009270:Naloxone / Q000627:therapeutic use; D009292:Narcotic Antagonists / Q000627:therapeutic use; D010147:Pain Measurement; D010149:Postoperative Pain / Q000517:prevention & control; D017060:Patient Satisfaction; D011446:Prospective Studies; D012119:Respiration / Q000187:drug effects; D013997:Time Factors
chemical_list: D000701:Analgesics, Opioid; D009292:Narcotic Antagonists; D009270:Naloxone; D009020:Morphine