title: Effects of phenylephrine on the sublingual microcirculation during cardiopulmonary bypass.
abstract: BACKGROUND
  The objective of the present study was to investigate sublingual microvascular blood flow and microcirculatory haemoglobin oxygen saturation (Smc(O(2))) during cardiopulmonary bypass (CPB) using constant systemic blood flow but different perfusion pressures achieved by phenylephrine administration.
  
  
  METHODS
  Fifteen patients undergoing coronary artery bypass grafting were enrolled in this pilot study. Systemic haemodynamics, oxygen transport variables, arterial and mixed venous blood gas analysis, and microcirculatory variables were determined after initiation of general anaesthesia, during CPB (systemic blood flow=2.4 litre m(-2)), after increasing perfusion pressure by 20 mm Hg with a continuous infusion of phenylephrine, and after termination of phenylephrine infusion.
  
  
  RESULTS
  CPB immediately resulted in a significant (P<0.05) decrease in systemic oxygen transport without alterations in sublingual microcirculatory blood flow and Smc(O(2)). Increasing perfusion pressure from 47 (SD 9) to 68 (7) mm Hg using phenylephrine=1.4 (1.0) microg kg(-1) min(-1) resulted in a significant decrease in sublingual small vessel blood flow (from median 2.5 to 1.8 arbitrary units) representing mostly capillary blood flow, but not in medium-sized vessels (median 3 to 2.8 arbitrary units). Concurrently, global tissue blood flow from 110 (54) to 197 (100) perfusion units and Smc(O(2)) increased from 72 (11)% to 84 (7)%, suggesting significant microcirculatory blood flow shunting in vessels with diameters >25 microm.
  
  
  CONCLUSIONS
  Our data demonstrate that an increased perfusion pressure produced by phenylephrine at constant CPB flow may decrease microcirculatory blood flow in the sublingual mucosal microcirculation due to microvascular blood flow shunting.
authors.affiliation: Department of Anaesthesiology and Critical Care Medicine, Innsbruck Medical University, Anichstrasse 35, A-6020 Innsbruck, Austria.
authors.forename: S
authors.initials: S
authors.lastname: Maier
authors.forename: W R
authors.initials: WR
authors.lastname: Hasibeder
authors.forename: C
authors.initials: C
authors.lastname: Hengl
authors.forename: W
authors.initials: W
authors.lastname: Pajk
authors.forename: B
authors.initials: B
authors.lastname: Schwarz
authors.forename: J
authors.initials: J
authors.lastname: Margreiter
authors.forename: H
authors.initials: H
authors.lastname: Ulmer
authors.forename: J
authors.initials: J
authors.lastname: Engl
authors.forename: H
authors.initials: H
authors.lastname: Knotzer
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D000768:Anesthesia, General; D002245:Carbon Dioxide; D002315:Cardiopulmonary Bypass; D001026:Coronary Artery Bypass; D005260:Female; D006801:Humans; D008297:Male; D008833:Microcirculation / Q000187:drug effects*; D008875:Middle Aged; D016343:Monitoring, Intraoperative / Q000379:methods; D009060:Mouth Floor / Q000098:blood supply*; D010100:Oxygen / Q000097:blood; D010313:Partial Pressure; D010656:Phenylephrine / Q000494:pharmacology*; D010865:Pilot Projects; D014662:Vasoconstrictor Agents / Q000494:pharmacology*
chemical_list: D014662:Vasoconstrictor Agents; D002245:Carbon Dioxide; D010656:Phenylephrine; D010100:Oxygen