The relationship between systemic oxygen uptake and del ivery during moderate hypothermic cardiopulmonary bypass: critical values and effects of vasodilation by hydralazine

Abstract

The relationship between oxygen delivery (DO₂) and uptake (VO₂) has been studied during moderately hypothermic cardiopulmonary bypass (CPB) in 15 patients undergoing myocardial revascularization. As soon as nasopharyngeal temperature was lowered to 32°C, blood flow was decreased from 2.4 to 2.0 l/min/m². Arterial and mixed venous blood gas analyses were performed five and eight minutes later and DO₂ and VO₂ were calculated; VO₂ stabilized in five minutes after changing blood flow and neither DO₂ nor VO₂ values changed three minutes later (DO₂: 217 ± 19 versus 215 ± 17 ml/min/m2; VO₂: 63 ± 12 versus 66 ± 14 ml/min/m2). Blood flow then was increased to 2.3 l/min/m² and DO₂ and VO₂ were determined again, five minutes later; they both increased significantly, to 243 ± 20 and 74 ± 13 ml/min/m², respectively. However, a further blood flow increase to 2.6 l/min/m² which caused DO₂ to increase to 277 ± 24 ml/min/m², did not affect VO₂ which was unchanged five minutes later (76 ± 13 ml/min/m²); VO₂ dependence on DO₂ values higher than 243 ± 20 ml/min/m² was consequently ruled out. Ten patients, having a mean arterial pressure higher than 80 mmHg, were eventually vasodilated with hydralazine, 0.1 mg/kg intravenously, and DO₂ and VO₂ were determined after five and ten minutes. As blood flow did not change, DO₂ was unaffected while a slight increase in VO₂ mean values was observed which was not statistically significant (prior to hydralazine: 78 ± 15 ml/min/m²; five minutes later: 82 ± 17 ml/min/m²; 10 minutes later: 76 ± 18 ml/min/m²).

In conclusion, during hypothermic CPB at 32°C, VO₂ plateau ranges between 48 and 102 mi/min/m² (mean ± 2 SD) in 95% of patients, corresponding to 66 and 141 ml/min/m² at 37°C; this finding closely matches other literature reports. Consequently, lower VO₂ values suggest inadequate oxygen supply to tissues. Critical DO₂ at 32°C is lower than 283 ml/min/m² in 97.5% of patients. Finally, arterial vasoconstriction does not seem to play a significant role in tissue hypoperfusion.

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References

Koning HM , Koning AJ , Defauw Jjam. Optimal perfusion during extra-corporeal circulation. Scand J Thorac Cardiovasc Surg 1987; 21: 207-13.

Harris EA , Seelye ER , Squire AW Oxygen consumption during cardiopulmonary bypass with moderate hypothermia in man. BrJAnaesth 1971; 43: 1113-20.

Tominaga R. , Kurisu K. , Fukumura F. et al. Effects of pump flow rate on oxygen use during moderate hypothermic cardiopulmonary bypass. ASAIO J 1993; 39: 126-31.

Schlichtig R. O2 uptake, critical O2 delivery, and tissue wellness . In: Pinsky MR, Dhainaut JFA eds. Pathophysiologic foundations of critical care. Baltimore: Williams and Wilkins, 1993: 119-39.

Bhatt SB , Hutchinson RC , Tomlinson B. , Oh TE , Mak M. Effect of dobutamine on oxygen supply and uptake in healthy volunteers . Br J Anaesth 1992; 69 : 298-303.

Irish CL , Murkin JM , Cleland A. , MacDonald JL , Mayer R. Neuromuscular blockade significantly decreases systemic oxygen consumption during hypothermic cardiopulmonary bypass. J Cardiothorac Vasc Anesth 1991; 5 : 132-34.

Harris EA , Seelye ER , Barratt-Boyes BG On the availability of oxygen to the body during cardiopulmonary bypass in man. Br J Anaesth 1974; 46: 425-31.

Shoemaker WC , Appel PL , Kram HB Tissue oxygen debt as a determinant of lethal and nonlethal postoperative organ failure. Crit Care Med 1988; 16: 1117-20.

Shibutani K. , Komatsu T. , Kubal K. , Sanchala V. , Kumar V. , Bizzarri DV Critical level of oxygen delivery in anesthetized man. Crit Care Med 1983; 11: 640-43.

10.

Hickey RF , Hoar PF Whole-body oxygen consumption during low-flow hypothermic cardiopulmonary bypass. J Thorac Cardiovasc Surg 1983 ; 86: 903-906.

11.

Matsuda H. , Sasako Y. , Nakano S. et al. Determination of optimal perfusion flow rate for deep hypothermic cardiopulmonary bypass in the adult based on distributions of blood flow and oxygen consumption. J Thorac Cardiovasc Surg 1992;103: 541-48.

12.

Fox LS , Blackstone EH , Kirklin JW , Stewart RW , Samuelson PN Relationship of whole body oxygen consumption to perfusion flow rate during hypothermic cardiopulmonary bypass. J Thorac Cardiovasc Surg 1982; 83: 239-48.

13.

Emerick T. , Sessler DI Current concepts in thermoregulation. Anesthetic effects. Probl Anesth 1994; 8 : 1-10.

14.

Belani K. , Sessler DI , Sessler AM et al. Leg heat content continues to decrease during the core temperature plateau in humans anesthetized with isoflurane. Anesthesiology 1993; 78 : 856-63.

15.

Alston RP , Singh M. , McLaren AD Systemic oxygen uptake during hypothermic cardiopulmonary bypass. Effects of flow rate, flow character, and arterial pH. J Thorac Cardiovasc Surg 1989; 98 : 757-68.

16.

Tuppurainen T. , Settergren G. , Stensved P. The effect of arterial pH on whole body oxygen uptake during hypothermic cardiopulmonary bypass in man. J Thorac Cardiovasc Surg 1989; 98: 769-73.

17.

Dunn J. , Kirsh MM , Harness J. , Carroll M. , Straker J. , Sloan H. Hemodynamic, metabolic, and hematologic effects of pulsatile cardiopulmonary bypass. J Thorac Cardiovasc Surg 1974 ; 68: 138-47.

18.

Bihari D. , Smithies M. , Gimson A. , Tinker J. The effects of vasodilation with prostacyclin on oxygen delivery and uptake in critically ill patients. New Engl J Med 1987; 317: 397-403.

19.

Evans PJ , Ruygrok P. , Seelye ER , Harris EA

Does sodium nitroprusside improve tissue oxygenation during cardiopulmonary bypass?

Br J Anaesth 1977; 49: 799-803.