title: Postoperative hemodynamic instability after simultaneous bilateral total knee arthroplasty.
abstract: OBJECTIVE
  After a simultaneously performed bilateral total knee arthroplasty, our institutional clinical experience suggested that there was an alarming incidence of severe postoperative hypotension and bradycardia. We therefore performed this study to define the incidence of postoperative hemodynamic instability and identify associated risk factors.
  
  
  METHODS
  This study involved a retrospective review of 312 consecutive patients undergoing bilateral total knee arthroplasty. The primary outcome was a hypotensive event in the postoperative period. This was defined as a systolic blood pressure of less than 85 mm Hg and/or the need for emergency postoperative medical management. Logistic regression was used to estimate odds ratios.
  
  
  RESULTS
  The incidence of hypotensive events in the postanesthesia care unit was 17% (95% confidence interval [CI], 13%-22%). The incidence of simultaneous hypotension and bradycardia was 7% (95% CI, 4%-10%). Of all patients, 10% required emergent treatment with vasopressors or vagolytics (95% CI, 7%-13%). The performance of the operation under spinal anesthesia was an independent risk factor (odds ratio = 4.5, P < 0.01) for the development of postoperative hypotension (21%) compared with general anesthesia (5.7%). Spinal anesthesia continued to predict hypotension in multivariate modeling that controlled for confounding variables.
  
  
  CONCLUSIONS
  Hypotension was common after bilateral total knee replacement in our series. Performance of the operation under spinal anesthesia was a significant risk factor for the development of postoperative hypotension compared with general anesthesia. General anesthesia may offer a greater margin of postoperative hemodynamic stability and perhaps safety for patients undergoing this procedure.
authors.affiliation: Department of Anesthesiology, Dartmouth-Hitchcock Medical Center, One Medical Center Drive, Lebanon, NH 03756, USA. reidy.christopher@gmail.com
authors.forename: Christopher M
authors.initials: CM
authors.lastname: Reidy
authors.forename: Michael L
authors.initials: ML
authors.lastname: Beach
authors.forename: John D
authors.initials: JD
authors.lastname: Gallagher
authors.forename: Brian D
authors.initials: BD
authors.lastname: Sites
mesh_terms: D000368:Aged; D019645:Arthroplasty, Replacement, Knee / Q000009:adverse effects*; D001919:Bradycardia / Q000453:epidemiology / Q000209:etiology*; D016001:Confidence Intervals; D005260:Female; D006439:Hemodynamics; D006801:Humans; D007022:Hypotension / Q000453:epidemiology / Q000209:etiology*; D015994:Incidence; D008297:Male; D009513:New Hampshire / Q000453:epidemiology; D016017:Odds Ratio; D011183:Postoperative Complications; D012189:Retrospective Studies; D012307:Risk Factors; D013599:Systole; D013997:Time Factors