title: Venous-arterial PCO2 and pH gradients in acutely ill postsurgical patients.
abstract: OBJECTIVE
  To investigate the venous-arterial PCO2 gradient, and the mixed venous blood acid-base status together with the oxygen transport variables in a group of acutely ill postsurgical patients.
  
  
  METHODS
  Retrospective, descriptive study of hemodynamic and acid-base data collected immediately after the patients' admission to the Postsurgical Intensive Care Unit.
  
  
  METHODS
  Eight-bed, Postsurgical Intensive Care Unit in a University Hospital.
  
  
  METHODS
  A total of one hundred and one postsurgical patients (87 male, 14 female; 14 to 86 years).
  
  
  METHODS
  None immediately before the first measurement.
  
  
  RESULTS
  Hemodynamic, oxygen transport variables, and arterial and mixed venous acid-base status measurements obtained immediately after the admission to the Postsurgical Intensive Care Unit. The venous-arterial PCO2 gradient was elevated (> 6 torr) in 23 patients and normal (< or = 6 torr) in 78 patients (respectively 9.1 +/- 3.3 vs 4.4 +/- 1.0 torr, p < 0.001). Patients with an increased venous-arterial PCO2 gradient had a higher arterial-venous pH gradient (0.05 +/- 0.03 vs 0.03 +/- 0.01 Unit, p < 0.001) and mixed venous PCO2 (47.5 +/- 8.0 vs 42.1 +/- 5.6 torr, p < 0.001). These patients had a lower cardiac index, oxygen delivery, mixed venous oxygen saturation, and a higher oxygen extraction index than the patients with normal venous-arterial PCO2 and pH gradients. For all the measurements, there was an inverse non linear significant relation between oxygen delivery, venous-arterial PCO2 (r = 0.74, p < 0.001) and pH (r = 0.57, p < 0.01) gradients.
  
  
  CONCLUSIONS
  This study suggests that in acutely ill postoperative patients increased venous-arterial PCO2 and pH gradients are directly and principally related to the reduction in blood flow and are both suggestive of low-flow state.
authors.affiliation: Istituto di Clinica Chirurgica Generale, Università degli Studi, Pisa.
authors.forename: L S
authors.initials: LS
authors.lastname: Brandi
authors.forename: F
authors.initials: F
authors.lastname: Giunta
authors.forename: M
authors.initials: M
authors.lastname: Pieri
authors.forename: A M
authors.initials: AM
authors.lastname: Sironi
authors.forename: T
authors.initials: T
authors.lastname: Mazzanti
mesh_terms: D000136:Acid-Base Equilibrium / Q000502:physiology*; D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D002245:Carbon Dioxide / Q000097:blood*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D011183:Postoperative Complications / Q000097:blood* / Q000503:physiopathology; D012189:Retrospective Studies
chemical_list: D002245:Carbon Dioxide