title: Defining intra-operative hypotension--a pilot comparison of blood pressure during sleep and general anaesthesia.
abstract: The scientific justification for particular values of intra-operative hypotension is poorly substantiated. To provide a rationale for appropriate values we recorded blood pressure measurements at home for 24 h using an automated non-invasive ambulatory blood pressure measurement device. These blood pressures were compared with blood pressure measured before and during general anaesthesia in 18 subjects undergoing elective day surgery. We confirmed that a pre-operative reading taken upon admission to hospital is significantly elevated compared to a usual daytime blood pressure in the same patient. The median (IQR [range]) increases in systolic and mean arterial pressures were 10 (2-15 [-5 to 59]) mmHg, p = 0.003 and 10 (5-14 [-5 to 35]) mmHg, p = 0.002, respectively. When using this admission blood pressure measurement as a 'baseline', systolic and mean arterial pressures decreased during sleep by 41 (30-46 [6-83]) mmHg and 34 (26-36 [6-58]) mmHg, respectively (p = 0.001). This decreased even further intra-operatively: systolic blood pressure by 49 (36-64 [15-96]) mmHg and mean arterial pressure by 36 (26-46 [8-66]) mmHg (p = 0.001).
authors.affiliation: St Vincent's Hospital, Melbourne, Victoria, Australia.
authors.forename: J C L
authors.initials: JC
authors.lastname: Soo
authors.forename: S
authors.initials: S
authors.lastname: Lacey
authors.forename: R
authors.initials: R
authors.lastname: Kluger
authors.forename: B S
authors.initials: BS
authors.lastname: Silbert
mesh_terms: D000328:Adult; D000368:Aged; D000556:Ambulatory Surgical Procedures; D000768:Anesthesia, General; D001794:Blood Pressure / Q000502:physiology; D018660:Blood Pressure Monitoring, Ambulatory / Q000379:methods; D002940:Circadian Rhythm / Q000502:physiology; D005260:Female; D006801:Humans; D007022:Hypotension / Q000175:diagnosis* / Q000503:physiopathology; D007431:Intraoperative Complications / Q000175:diagnosis* / Q000503:physiopathology; D008297:Male; D008875:Middle Aged; D010865:Pilot Projects; D012890:Sleep / Q000502:physiology*; D014851:Wakefulness / Q000502:physiology