Relationship between svo2 and scvo2

Venous Oximetry Overview

relationship between svo2 and scvo2

surement (ScvO2) as a surrogate for mixed venous oxygen saturation . Thus, ScvO2 is not S¯vO2 (41), and the relationship between these two variables changes with .. Shunt fraction = (1 2 SaO2)/(1 2 SvO2). For example. The correlation between mixed venous oxygen saturation and cardiac output was poor. The relationship between Svo2 and Scvo2 has not assessed in such. The influence of surgery, cardiopulmonary bypass and anaesthesia drugs on the relationship between SvO2 and ScvO2 has never been studied. METHODS.

Abstract Hemodynamic monitoring has become a real challenge in the intensive care unit. However, technical limitations and potential iatrogenic complications constitute important limits for a widespread use.

Regular central venous catheters coupled with a fiberoptic lumen for central venous oxygen saturation ScvO2 monitoring have been proposed as a surrogate for SvO2 monitoring. The purpose of the present article is to review the physiological backgrounds of circulation, the pathophysiology of circulatory failure and subsequent venous oxygen saturation alterations, and finally the merits and the limits of the use of ScvO2 in different clinical situations.

Introduction Hemodynamic monitoring has become a common practice in the intensive care unit. Besides blood pressure measurement, most industrial efforts have concentrated on providing devices for cardiac output monitoring.

However, adequate adaptation of these macrohemodynamic parameters is somehow challenging. Indeed, as cardiac output is an adaptive parameter, it is always difficult to judge whether a given value at a given time for a given patient is appropriate or not.

relationship between svo2 and scvo2

Similarly, which value should be considered an appropriate goal for blood pressure, considering regional perfusion specificities e. Therefore, considering that O2 supply to the tissue is the basic objective, intensivists have been trying to find out an integrative parameter that would be more suitable to globally assess hemodynamic status of their patients. As explained for the dummies, oxygen venous saturation is interpreted as a bank statement at the end of the month: Normal Circulation Physiology One of the main goals of blood circulation is to ensure oxygen supply to organs and tissues.

relationship between svo2 and scvo2

The arterial content in oxygen has 2 components. The main component is oxygen bound to hemoglobin Hb.

relationship between svo2 and scvo2

If this is not sufficient to meet tissue energy needs, we move to our second compensation. Anaerobic Metabolism iIncreases If the tissues fail to receive an adequate supply of oxygen, anaerobic metabolism becomes the only mechanism to produce tissue ATP.

Anaerobic metabolism is inefficient, producing a large amount of metabolic waste e. It also produces a relatively poor supply of ATP.

relationship between svo2 and scvo2

Prolonged anaerobic metabolism leads to energy depletion and metabolic acidosis. If SvO2 decreases, it indicates that the tissues are extracting a higher percentage of oxygen from the blood than normal. In otherwords, a decreased SvO2 indicates that the cardiac output is not high enough to meet tissue oxygen needs. Thus, SvO2 can indicate whether an individual's cardiac output is high enough to meet their needs.

A rise in SvO2 demonstrates a decrease in oxygen extraction, and usually indiates that the cardiac output is meeting the tissue oxygen need. A return of the SvO2 to normal suggests patient improvement.

Central venous and mixed venous oxygen saturation in critically ill patients.

However, a rise in SvO2 in the presence of a rising lactate is inappropriate - the patient who has resorted to anaerobic metabolism third compensation should have evidence of a high cardiac output and increased extraction. This is an ominous finding, suggesting that the tissues are unable to extract. It can be seen in late septic shock, or in cell poisoning such as cyanide. Cardiac output is routinely measured to evaluate drug effectiveness.

relationship between svo2 and scvo2

Unfortunately, the cardiac output measurement only gives us a value, it does not indicate whether the measured cardiac output is meeting the patient's needs. For some individuals, a cardiac output that falls below the normal range may be adequte, whereas for others, a normal or elevated cardiac output value may be too low.

Central venous and mixed venous oxygen saturation in critically ill patients.

SVO2 can be very helpful when attempting to determine whether a change in therapy is beneficial. Measuring SvO2 before and after a change can assist in determining whether the therapy made the patient better or worse.


SvO2 can also be useful when evaluating changes to ventilator therapy, especially in unstable patients. Changes may be made to the ventilator to increase the oxygen content of the blood, which is important to the total oxygen delivery cardiac ouptut X oxygen content.

Tissue oxygen need is met when the amount of oxygen being delivered to the tissues is sufficient to meet the amount of oxygen being consumed VO2. When the oxygen delivery falls below oxygen consumption needs, lactic acidosis develops. The cardiac output is not high enough to meet tissue oxygen needs The Hb is too low The SaO2 is too low Oxygen consumption has increased without an increase in oxgyen delivery Brenda Morgan.