From the Guidelines
Blood lactate is the most sensitive test to estimate and monitor the extent of tissue hypoperfusion, as recommended by the European guideline on management of major bleeding and coagulopathy following trauma: sixth edition 1.
Key Indicators for Tissue Perfusion
The assessment of tissue perfusion is a complex process that involves evaluating multiple clinical parameters. Some of the key indicators include:
- Capillary refill time: provides immediate bedside information about peripheral perfusion
- Urine output: reflects renal perfusion, with a target of >0.5 mL/kg/hr
- Serum lactate levels: rises when tissues experience inadequate oxygen delivery, with levels above 2 mmol/L suggesting impaired perfusion
- Base deficit: may represent a suitable alternative to lactate measurements in certain situations 1
- Blood pressure, heart rate, arterial pH, and central venous oxygen saturation: also provide valuable information about tissue perfusion
Importance of a Multi-Parameter Approach
A multi-parameter approach is essential for assessing tissue perfusion, as relying on a single indicator could miss significant perfusion deficits in specific tissues or organs. This approach allows for a more comprehensive understanding of tissue perfusion and can help guide resuscitation efforts.
Guiding Resuscitation Efforts
Guiding resuscitation to normalize lactate in patients with elevated lactate levels as a marker of tissue hypoperfusion is a recommended approach, although the quality of evidence is low 2.
Prioritizing Blood Lactate
Given the current evidence, blood lactate is the most sensitive test for estimating and monitoring tissue hypoperfusion, and its measurement should be prioritized in clinical practice 1.
From the Research
Indicators of Tissue Perfusion
- Lactate and central venous oxygen saturation (ScvO2) are commonly used endpoints for assessing shock and guiding resuscitation in critically ill patients 3.
- However, each of these endpoints has its own limitations, and when used together, they provide a more comprehensive understanding of the underlying pathophysiologic state 3.
- Capillary refill time (CRT) has been proposed as an alternative resuscitation target, and studies have shown that it can be an effective indicator of tissue perfusion 4, 5, 6.
Comparison of Indicators
- A study comparing CRT-targeted and lactate-targeted fluid resuscitation strategies found that CRT-targeted resuscitation was associated with a higher achievement of the predefined perfusion target, but no significant differences in perfusion-related variables or hypoxia surrogates were observed 4.
- Another study found that ΔA b, a quantitative index of circulatory status measured using quantitative capillary refill time, was independently and significantly associated with high lactate levels 5.
- A prospective observational study found that abnormal CRT after initial fluid resuscitation was associated with increased risk of adverse outcomes and hospital mortality in hyperlactatemic septic patients 6.
Predictors of Oxygen Consumption
- A study found that lactate and venoarterial carbon dioxide difference/arterial-venous oxygen difference ratio, but not central venous oxygen saturation, predicted increase in oxygen consumption in fluid responders 7.
- This suggests that indicators of anaerobic metabolism, such as lactate, may be more useful than central venous oxygen saturation in predicting the response to fluid resuscitation and guiding hemodynamic resuscitation 7.