title: Preoperative angiotensin system inhibitor use attenuates heparin-induced hypotension in patients undergoing cardiac surgery.
abstract: OBJECTIVE
  Both angiotensin system inhibitor (ASI) use and heparin are associated with hypotension. This study attempted to determine whether preoperative ASI therapy affected the hemodynamic response to heparin administered to patients undergoing cardiac surgery.
  
  
  METHODS
  Sixty-two patients undergoing elective cardiac surgery requiring full (300 units/kg) systemic heparinization were studied prospectively. Thirty-three patients were receiving preoperative ASI therapy, whereas 29 patients were not. Anesthetic technique and mechanical ventilation parameters were standardized. Hemodynamics were recorded at 3 time points: baseline (just before the administration of heparin), 1-minute post-heparin administration, and 4-minute post-heparin administration.
  
  
  METHODS
  Single university hospital.
  
  
  METHODS
  Patients undergoing elective cardiac surgery.
  
  
  METHODS
  None.
  
  
  RESULTS
  The 2 groups were similar regarding preoperative demographics and baseline hemodynamics. Baseline mean arterial pressure (MAP) in non-ASI patients was 82.0 mmHg, and it decreased significantly to 76.3 mmHg (1 min; p<0.05) and 70.7 mmHg (4 min; p<0.05) following heparin administration. MAP values in ASI patients were 81.9 mmHg, 81.8 mmHg, and 76.8 mmHg at baseline, 1-minute post-heparin, and 4-minute post-heparin administration, respectively (changes not significant).Within-group analysis revealed that non-ASI patients experienced significant decrease in MAP at 1-minute (-6.6%, p = 0.01) and 4-minute (-13.0%, p = 0.0011) post-heparin administration, whereas ASI patients did not (+1.9%, p = 0.52; -3.8%, p = 0.16, respectively). Between-group analysis revealed that differences in MAP values at 1 minute were significant (p = 0.03), whereas differences at 4 minutes were not significant (p = 0.05).
  
  
  CONCLUSIONS
  This prospective clinical study indicated that preoperative ASI therapy until the day before surgery may attenuate heparin-induced hypotension. Definitive mechanistic insight requires further clinical study.
authors.affiliation: Department of Anesthesia and Critical Care, University of Chicago, Chicago IL.
authors.forename: Richa
authors.initials: R
authors.lastname: Dhawan
authors.forename: Mark A
authors.initials: MA
authors.lastname: Chaney
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000806:Angiotensin-Converting Enzyme Inhibitors / Q000494:pharmacology / Q000627:therapeutic use; D000809:Angiotensins / Q000037:antagonists & inhibitors* / Q000502:physiology; D006348:Cardiac Surgical Procedures / Q000379:methods*; D017558:Elective Surgical Procedures / Q000379:methods*; D005260:Female; D006493:Heparin / Q000009:adverse effects*; D006801:Humans; D007022:Hypotension / Q000139:chemically induced / Q000503:physiopathology / Q000517:prevention & control*; D008297:Male; D008875:Middle Aged; D011300:Preoperative Care / Q000379:methods*; D011446:Prospective Studies; D055815:Young Adult
chemical_list: D000806:Angiotensin-Converting Enzyme Inhibitors; D000809:Angiotensins; D006493:Heparin
keywords: angiotensin system inhibitors; cardiac surgery; heparin; hypotension