How do I assess sternal capillary refill time, what is the normal value, and what does a prolonged refill indicate?

Sternal Capillary Refill Time Assessment

Sternal capillary refill time (CRT) should be assessed by applying firm pressure to the midpoint of the sternum for 5 seconds, then measuring the time for color to return; normal is ≤2 seconds in adults and ≤3 seconds in neonates, with prolonged refill indicating inadequate tissue perfusion or shock.

How to Perform the Assessment

Apply firm pressure to the midpoint of the sternum for 5 seconds using moderate pressure 1, 2, 3. Use a stopwatch or digital timer for accurate measurement to reduce inter-observer variability 3. Measure the time from release of pressure until complete return of normal color to the blanched area 1.

Key Technical Points:

• Site selection: The sternum (midpoint of chest) provides the most consistent and reproducible measurements compared to peripheral sites 2, 4
• Pressure duration: 5 seconds of blanching pressure is the standardized approach 2, 3
• Ambient conditions: Perform in room temperature 20-25°C when possible, as temperature affects results 3
• Use timing device: Stopwatches significantly reduce variability between observers 3

Normal Values

Adults and children >7 days: Normal CRT is ≤2 seconds 1, 5, 6, 3

Neonates (first 7 days): Normal sternal CRT is up to 3 seconds 2. The mean sternal CRT in healthy newborns ranges from 1.82-2.01 seconds, with an upper limit of normal at 3 seconds 2.

Important Caveats:

• Sternal CRT is consistently longer than peripheral sites (finger/toe) by approximately 0.5 seconds 4
• Fingertip and sternal measurements are not interchangeable - fingertip CRT averages 1.08 seconds while sternum averages 1.5 seconds in children 4
• Extended pressure duration (>5 seconds) artificially prolongs CRT regardless of site 7

Clinical Significance of Prolonged CRT

Prolonged CRT (>2 seconds in adults/children, >3 seconds in neonates) indicates:

Primary Indication - Inadequate Tissue Perfusion

Prolonged CRT reflects compromised microcirculation and inadequate tissue perfusion 8, 5, 6. It serves as a clinical marker of shock states before hypotension develops 5.

Specific Clinical Contexts:

In sepsis/shock resuscitation: CRT is advocated as a clinical measure of adequate tissue perfusion alongside skin temperature, degree of mottling, pulse, blood pressure, and conscious level 8. Guidelines specifically recommend targeting normal CRT ≤2 seconds as a therapeutic endpoint for goal-directed shock resuscitation 6.

Predictive value: A normal central CRT ≤2 seconds demonstrates 84.4% sensitivity and 71.4% specificity in predicting adequate superior vena cava oxygen saturation (ScvO₂) ≥70% 6. This validates CRT as a reliable bedside indicator when central venous access is unavailable 6.

In cardiac arrest assessment: Prolonged CRT combined with other signs (unresponsiveness, absent breathing, no signs of life) supports the decision to initiate CPR 9, 5. However, CRT should not be used as the sole determinant - it must be combined with pulse check and other clinical signs 9.

Factors That Prolong CRT (Non-Pathologic):

• Ambient temperature <20°C or >25°C 3
• Phototherapy in neonates (though differences are not clinically significant) 2
• Advanced age 10
• Measurement site (peripheral sites show longer CRT than central) 4

Practical Algorithm for Interpretation

1. Measure sternal CRT using standardized technique (5-second pressure, stopwatch, room temperature)
2. If CRT ≤2 seconds: Suggests adequate tissue perfusion (proceed with standard assessment)
3. If CRT >2 seconds: Indicates potential inadequate perfusion
   • Assess for shock: tachycardia, hypotension, altered mental status, decreased urine output 5
   • Check other perfusion markers: skin temperature, mottling, lactate 8
   • Consider fluid resuscitation if hypovolemic shock suspected 11
   • Initiate goal-directed therapy targeting CRT normalization 6

Critical pitfall: In term neonates during the first 4 hours after birth, an unexpected moderate direct correlation exists between elevated blood pressure and prolonged CRT, possibly due to circulating vasoactive substances 7. CRT may be less reliable as a cardiovascular indicator during this specific period 7.