Supranormal Elevation of Systemic Oxygen Delivery in Critically Ill Patients


Intervention

Indications

Cautions

Side effects

Protocol

Notes

Supranormal elevation of oxygen delivery

Critically ill patients at increased risk of death

Patients not responding to initial challenge have a worse prognosis

Older and sicker patients tend not to reach therapeutic goals

Extensive use of dobutamine is associated with increased incidence of tachyarrhythmias and ischemic electrocardiographic findings

Supranormal targets: cardiac index ≥4.5 L/min/m2, oxygen delivery ≥600 mL/min/m2, oxygen consumption ≥170 mL/min/m2, and mixed venous oxygen saturation ≥70 %

Aiming to increase oxygen consumption is demonstrated to increase mortality




Box 12.1. Definitions

Oxygen content

The oxygen content of blood is determined by several factors with the major proportion provided by the saturation of hemoglobin in the blood.


$$ {\mathrm{CaO}}_2=\left({\mathrm{SaO}}_2\times \mathrm{H}\mathrm{b}\times 1.34\right)+0.003\left({\mathrm{PaO}}_2\right) $$




  • Hb = hemoglobin concentration in g/l


  • SaO2 = oxygen saturation


  • PaO2 = arterial oxygen partial pressure

Oxygen delivery

Oxygen delivery is simply a product of the arterial oxygen content and cardiac output.


$$ {\mathrm{DO}}_2=\mathrm{C}\mathrm{O}\times {\mathrm{CaO}}_2 $$




  • CO = cardiac output (heart rate x stroke volume)

Oxygen consumption

Oxygen consumption can be calculated from the product of the cardiac output and the difference between the arterial and venous oxygen content.


$$ {\mathrm{VO}}_2=\mathrm{C}\mathrm{O}\left({\mathrm{CaO}}_2-{\mathrm{CvO}}_2\right) $$




  • CO = cardiac output


  • CaO2 = arterial oxygen content


  • CvO2 = venous oxygen content

Oxygen extraction ratio

The ability to extract oxygen from the blood is determined by the ratio of oxygen consumption to oxygen delivery.


$$ {}_{\mathrm{O}2}\mathrm{E}\mathrm{R}={\mathrm{VO}}_2/{\mathrm{DO}}_2 $$




  • VO2 = oxygen consumption, DO2 = oxygen delivery



References



1.

Sakr Y, Lobo SM, Moreno RP, Gerlach H, Ranieri VM, Michalopoulos A, Vincent JL, The SOAP Investigators (2012) Patterns and early evolution of organ failure in the intensive care unit and their relation to outcome. Crit Care 16(6):R222CrossRefPubMedCentralPubMed


2.

Seely AJ, Christou NV (2000) Multiple organ dysfunction syndrome: exploring the paradigm of complex nonlinear systems. Crit Care Med 28:2193–2200CrossRefPubMed


3.

Third European Consensus Conference in Intensive Care Medicine. Tissue hypoxia: how to detect, how to correct, how to prevent. Societe de Reanimation de Langue Franchise. The American Thoracic Society. European Society of Intensive Care Medicine (1996) Am J Respir Crit Care Med. 154:1573–1578


4.

Shoemaker WC, Appel PL, Kram HB (1992) Role of oxygen debt in the development of organ failure sepsis, and death in high-risk surgical patients. Chest 102(1):208–215CrossRefPubMed

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May 9, 2017 | Posted by in CRITICAL CARE | Comments Off on Supranormal Elevation of Systemic Oxygen Delivery in Critically Ill Patients

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