Value of the venous-arterial PCO2 gradient to reflect the oxygen supply to demand in humans: effects of dobutamine.
OBJECTIVE
To test the value of venous-arterial PCO2 gradient (deltaPCO2) measurements to reflect the adequacy of cardiac index (CI) to oxygen demand in patients submitted to rapid changes of CI and oxygen demand.


METHODS
Prospective, comparative study.


METHODS
Medical intensive care unit of a university hospital.


METHODS
Ten patients with congestive heart failure exhibiting low baseline CI (< or =2.5 L/min/m2) but no evidence of global tissue hypoxia, as attested by the absence of clinical signs of shock and by normal blood lactate concentrations.


METHODS
Infusion of incremental doses of dobutamine: 0 (D0), 5 (D5), 10 (D10), and 15 (D15) microg/kg/min.


RESULTS
The CI increased by a linear fashion from D0 (1.6+/-0.1 L/min/m2) to D15 (2.4+/-0.2 L/min/m2) (p< .05). The mixed venous oxygen saturation (SVO2) increased from D0 (49+/-2%) to D10 (61+/-2%) (p < .05) and remained unchanged from D10 to D15 (60+/-2%). The oxygen extraction ratio (O2 ER) and the deltaPCO2 decreased from D0 (48+/-2% and 9+/-1 torr [1.2+/-0.3 kPa], respectively) to D10 (36+/-2% and 5+/-1 torr [0.7+/-0.1 kPa], respectively) (p < .05 for both comparisons) and remained unchanged from D10 to D15 (36+/-2% and 6+/-1 torr [0.8+/-0.1 kPa], respectively). The biphasic courses of SVO2, O2 ER, and deltaPCO2 were related to the course of oxygen consumption that remained constant from D0 (113+/-9 mL/min/m2) to D10 (112+/-8 mL/min/m2) and significantly increased from D10 to D15 (127+/-10 mL/min/m2) (p <.05).


CONCLUSIONS
deltaPCO2 can be reliably used at the bedside for informing on the adequacy of CI with respect to a given metabolic condition, and particularly for detecting changes in oxygen demand (e.g., the changes accompanying drug-induced changes in CI). In this regard, deltaPCO2, together with O2 ER and SVO2, can help to assess the adequacy of CI to global oxygen demand.
Teboul
J L
JL
Service de Réanimation Médicale, Hôpital de Bicêtre, Hôpitaux de Paris, Faculté de Médecine Paris-Sud, Université Paris XI, France.
Mercat
A
A
Lenique
F
F
Berton
C
C
Richard
C
C
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001158:Arteries; D002245:Carbon Dioxide / Q000097:blood* / Q000378:metabolism; D002302:Cardiac Output / Q000187:drug effects*; D002316:Cardiotonic Agents / Q000008:administration & dosage / Q000494:pharmacology*; D004280:Dobutamine / Q000008:administration & dosage / Q000494:pharmacology*; D004305:Dose-Response Relationship, Drug; D005260:Female; D006333:Heart Failure / Q000097:blood / Q000378:metabolism / Q000503:physiopathology*; D006801:Humans; D007362:Intensive Care Units; D008297:Male; D008875:Middle Aged; D010101:Oxygen Consumption; D011446:Prospective Studies; D014680:Veins
D002316:Cardiotonic Agents; D002245:Carbon Dioxide; D004280:Dobutamine