title: Estimated versus actual weight when dosing rt-PA in acute ischemic stroke: is there a difference?
abstract: BACKGROUND
  Intravenous (IV) recombinant tissue plasminogen activator (rt-PA) is the standard of care for patients exhibiting signs of acute ischemic stroke. IV rt-PA uses weight-based dosing, and often an estimated weight is used. The clinical effects of using estimated weight in dosing IV rt-PA remain unclear. The goal of this descriptive study was to determine if there was a significant difference in estimated versus actual weight dosing of rt-PA.
  
  
  METHODS
  A retrospective chart review was performed to compare estimated versus actual patient weight. The sample consisted of patients from the hospital database who received IV rt-PA during June 2009-June 2010. Patients were included if they presented to the emergency department with stroke symptoms, received IV rt-PA, and had documented estimated and actual weights. Recorded (prescribed) dosing of IV rt-PA was compared with the suggested dosing using the admission weight. The differences between the weights and doses were calculated, analyzed, and categorized as being underdosed or overdosed.
  
  
  RESULTS
  Twenty-six charts met the inclusion criteria. Using descriptive statistics and tests of difference, the mean estimated weight was 79.9 kg (±3.92 kg) and the mean actual weight was 78.5 kg (±3.86 kg); four patients had an estimated weight discrepancy of ≥5 kg. Six had correct estimated dosing; however, all of these patients were greater than 100 kg and received the maximum dose of 90 mg. Eleven patients' estimated weights were underestimated, resulting in underdosing of IV rt-PA. Nine estimated weights were overestimated, leading to overdosing of the medication, but none of the dosing overages exceeded 10%. No statistical significance was found between the two groups' estimated weights or dosing errors, t(26) = 0.69, p = .79.
  
  
  CONCLUSIONS
  Results from this study found documented estimated weights were not significantly different from actual weights and the precision of estimated weight were similar to weights obtained using a scale. Despite these results, methods for obtaining actual weights in the emergency department for high-risk patients should be explored.
authors.affiliation: University of Colorado Hospital, Aurora, CO, USA. Alexandra.graves@ucdenver.edu
authors.forename: Alexandra
authors.initials: A
authors.lastname: Graves
authors.forename: Anna
authors.initials: A
authors.lastname: VerHage
authors.forename: Brian
authors.initials: B
authors.lastname: Richlik
authors.forename: Mary Beth Flynn
authors.initials: MB
authors.lastname: Makic
mesh_terms: D000368:Aged; D001835:Body Weight; D004305:Dose-Response Relationship, Drug; D016529:Emergency Nursing / Q000379:methods*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D011994:Recombinant Proteins / Q000008:administration & dosage*; D012189:Retrospective Studies; D020521:Stroke / Q000188:drug therapy* / Q000451:nursing*; D015912:Thrombolytic Therapy / Q000379:methods / Q000451:nursing; D010959:Tissue Plasminogen Activator / Q000008:administration & dosage*
chemical_list: D011994:Recombinant Proteins; D010959:Tissue Plasminogen Activator