Normal Capillary Refill Time
Normal capillary refill time (CRT) is defined as less than 2 seconds, measured by applying pressure to the nail bed until blanching occurs and then timing the return to pink color after pressure release. 1
Definition and Measurement Technique
- CRT is performed on the nail beds as an indicator of tissue perfusion and is also called the nail blanch test. 1
- The test involves applying pressure until the nail bed blanches, then releasing and timing how long it takes for the pink color to return. 1
- Normal CRT is defined as return to pink color in less than 2 seconds after pressure is removed. 1
- Delayed CRT is defined as return to pink color in greater than 2 seconds after pressure is removed. 1
Clinical Significance for Circulatory Status
A normal CRT ≤2 seconds indicates adequate tissue perfusion and is a key therapeutic endpoint in shock resuscitation, particularly in pediatric patients. 1
In Shock Assessment
- Prolonged CRT >2 seconds is a clinical sign of inadequate tissue perfusion and shock, particularly "cold shock" with peripheral vasoconstriction. 1
- The American College of Critical Care Medicine uses CRT ≤2 seconds as a therapeutic endpoint for pediatric septic shock resuscitation. 1
- Delayed CRT ≥2 seconds, combined with other signs (altered mental status, cool extremities, mottled skin), indicates septic shock even without hypotension. 1
Prognostic Value
- Delayed CRT ≥2 seconds is a reasonable prognostic indicator, especially in children with decreased conscious level. 1
- In Class III hemorrhagic shock, prolonged CRT >2 seconds is one of the defining characteristics along with hypotension and tachycardia. 2
- A normal CRT ≤2 seconds is associated with superior vena cava oxygen saturation (ScvO₂) ≥70%, indicating adequate oxygen delivery. 3
Important Clinical Caveats
Age and Gender Variations
- While the 2-second cutoff is standard in guidelines, research shows CRT varies with age and gender, though guidelines maintain the 2-second threshold for clinical decision-making. 4, 5
- Median CRT in healthy individuals ranges from 0.7 seconds in young females to 1.8 seconds in elderly men. 4
- The 2-second cutoff may result in false-positive rates of 4% in pediatric/adult males, 13.7% in adult females, and 29% in elderly patients. 4
Environmental Factors
- CRT is temperature-dependent and can be prolonged in cold environments, which may affect reliability in prehospital settings. 4, 5
- CRT decreases by 1.2% per degree Celsius rise in ambient temperature and by 5% per degree Celsius rise in patient temperature. 5
- After cold water immersion, median CRT increased from 1.3 to 2.9 seconds. 4
Measurement Site Considerations
- Central CRT (forehead/sternum) has 84.4% sensitivity and 71.4% specificity for predicting ScvO₂ ≥70%. 3
- Peripheral CRT (finger/toe) has 71.9% sensitivity and 85.7% specificity for predicting ScvO₂ ≥70%. 3
- Both central and peripheral CRT ≤2 seconds are associated with adequate oxygen delivery. 3
Limitations in Post-Resuscitation Phase
- In the intensive care unit post-resuscitation phase, CRT correlates poorly with hemodynamic parameters in post-cardiac surgery patients. 6
- In general ICU patients (mostly septic shock), CRT relates weakly to stroke volume index and lactate, with a CRT ≥6 seconds having the best predictive value for reduced stroke volume. 6
- The standard 2-second cutoff may be too conservative for ventilated ICU patients in the post-resuscitation phase. 6
Clinical Application Algorithm
For acute assessment and resuscitation:
- Use CRT ≤2 seconds as the target therapeutic endpoint. 1
- Measure centrally (sternum) or peripherally (nail beds) depending on clinical context. 3
- Interpret prolonged CRT in context with other perfusion indicators: mental status, pulse quality, extremity temperature, urine output, and blood pressure. 1
For ongoing monitoring: