title: Orthostatic hypotension occurs frequently in the first hour after anesthesia.
abstract: Symptoms of orthostatic intolerance are common after general anesthesia and are associated with an increased risk of postoperative morbidity. The contribution of orthostatic hypotension (OH) has not been well defined. We conducted a head-up tilt test on patients after general anesthesia for minor surgery to assess the incidence of and risk factors for OH after general anesthesia. One-hundred-four patients were enrolled and were prospectively divided into four groups: older female, older male, young female, and young male. The incidence of OH was 76.0%, 72.0%, 45.5%, and 62.5% respectively and was associated with increasing age (P < 0.05) and posttest dizziness (P < 0.05). Body mass index, preoperative blood pressure, ASA class, anesthetic duration, IV fluid administration, and use of analgesics and antiemetics in the postanesthetic care unit were not different in subjects who demonstrated OH compared with those with a normotensive response. Subjects with OH after general anesthesia did not increase their heart rate and diastolic blood pressure with a head-up tilt which may have been caused by persistent effects of anesthetics on reflex cardiovascular control and/or bedrest-induced dysregulation of reflex cardiovascular control. We conclude that OH is common after general anesthesia for minor surgery and may be the major cause of postoperative orthostatic intolerance.
  
  
  CONCLUSIONS
  Orthostatic hypotension, a failure to maintain blood pressure on assuming an upright posture, is common after general anesthesia for minor surgery and may be the major cause of postoperative orthostatic intolerance.
authors.affiliation: *Department of Anesthesia and Perioperative Medicine, London Health Sciences Centre, and The University of Western Ontario; and †School of Kinesiology, The University of Western Ontario, London, Ontario, Canada.
authors.forename: Dean A
authors.initials: DA
authors.lastname: Cowie
authors.forename: J Kevin
authors.initials: JK
authors.lastname: Shoemaker
authors.forename: Adrian W
authors.initials: AW
authors.lastname: Gelb
mesh_terms: D000293:Adolescent; D000328:Adult; D000367:Age Factors; D000368:Aged; D000758:Anesthesia / Q000009:adverse effects*; D001794:Blood Pressure / Q000502:physiology; D005260:Female; D006801:Humans; D007024:Hypotension, Orthostatic / Q000453:epidemiology* / Q000503:physiopathology; D008297:Male; D008875:Middle Aged; D011183:Postoperative Complications / Q000453:epidemiology* / Q000503:physiopathology; D020250:Postoperative Nausea and Vomiting / Q000453:epidemiology; D011187:Posture / Q000502:physiology; D011446:Prospective Studies; D012307:Risk Factors; D012737:Sex Factors; D016683:Supine Position / Q000502:physiology