Oxygenation in patients with a functionally univentricular circulation and complete mixing of blood - Are saturation and flow interchangeable?

被引:22
作者
Francis, DP
Willson, K
Thorne, SA
Davies, LC
Coats, AJS
机构
[1] Royal Brompton Hosp, Dept Cardiol, Heart Funct Unit, London SW3 6LY, England
[2] Royal Brompton Hosp, Biomed Engn Res Unit, London SW3 6LY, England
[3] Univ London Imperial Coll Sci Technol & Med, Natl Heart & Lung Inst, London, England
关键词
oxygen; circulation; blood flow;
D O I
10.1161/01.CIR.100.21.2198
中图分类号
R5 [内科学];
学科分类号
1002 ; 100201 ;
摘要
Background-Perioperative management of patients with complete mixing of pulmonary and systemic blood centers on approximately equating pulmonary (Qp) and systemic (Qs) blood flow (Qp/Qs approximate to 1). This empirically derived target is opposed by theoretical studies advocating a target Qp/Qs well below 1. We studied the cause of this persistent discrepancy. Methods and Results-Classic theoretical studies have concentrated on maximizing 1 of many potential combination parameters of arterial oxygen content (Cao(2)) and systemic blood flow: total oxygen delivery (Do(2))=Cao(2) X Qs. We defined "useful" oxygen delivery as the amount of oxygen above a notional saturation threshold (Sat(Thresh)): D(u)o(2) = carrying capacityX(Sao(2) - Sat(Thresh)) X Qs, Whereas Do(2) peaks at Qp/Qs ratios <1, D(u)o(2) peaks at higher Qp/Qs ratios, nearer to (or exceeding) 1. Systemic venous saturation (which mirrors tissue oxygen tension) peaks at Qp/Qs=1. Conclusions-First, the standard model of single-ventricle physiology can be reexpressed in a form allowing analysis by differential calculus, which allows broader conclusions to be drawn than does computer modeling alone. Second, the classic measure Dot fails to reflect the fact that proportional changes in saturation and flow are not clinically equivalent, Recognizing this asymmetry by using D(u)O-2 can give a target Qp:Qs balance that better represents clinical experience. Finally, to avoid an arbitrary choice of Sat(Thresh), systemic venous oxygen saturation (Ssvo(2)) may be a useful parameter to maximize: this occurs at a Qp/Qs ratio of 1. Attempts to increase Do, by altering Qp/Qs away from this value will inevitably reduce Ssvo(2) and therefore tissue oxygenation. Oxygen delivery is far from synonymous with tissue oxygen status.
引用
收藏
页码:2198 / 2203
页数:6
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