Is ATLS wrong about palpable blood pressure estimates?
In Advanced Trauma Life Support (ATLS), we learned that a carotid, femoral, and radial pulse correlates to a certain systolic blood pressure (SBP) in hypotensive trauma patients. Specifically ATLS stated:
- Carotid pulse only = SBP 60 – 70 mmHg
- Carotid & Femoral pulse only = SBP 70 – 80 mmHg
- Radial pulse present = SBP >80 mmHg
Is this true or a myth?
There were two studies that evaluated this paradigm.
“ATLS Paradigm Fails”1
What they did: In 20 hypovolemic trauma patients with SBP
- 5/20 (25%) pts were correctly predicted by ATLS guidelines
- 10/20 (50%) pts had false overestimation of BP by ATLS guidelines
- False overestimation of BP was greatest in pts with lowest BPs
- Mean difference of actual and estimated BP using ATLS was 34 mmHg
Conclusion: Radial pulses are often present in severely hypotensive hypovolemic patients, meaning the ATLS paradigm is invalid.
“Accuracy of ATLS guidelines for predicting SBP”2
What they did: In 20 patients with hypovolemic shock and arterial lines, pulses were palpated by an observer blinded to BP readings.
What they found: The disappearance of pulse always occurred in the following order radial > femoral > carotid pulse. There were 4 subgroups:
- Group 1: Radial, femoral, and carotid pulses present
- 10/12 (83%) had SBP <80 mmHg
- Group 2: Femoral and carotid pulses only
- 10/12 (83%) had SBP <70 mmHg
- Group 3: Carotid pulse only
- 0/4 (0%) had SBP >60 mmHg
- Group 4: Radial, femoral, and carotid pulses absent
- 2/3 (67%) had SBP <60 mmHg
Conclusion: ATLS guidelines for assessing SBP are inaccurate and generally overestimate the patient’s SBP.
Although very small studies, they were done by two different authors, using different methods (BP cuff vs arterial line). Both came to the same conclusion: ATLS overestimates SBP based on palpation of radial, femoral, & carotid pulses. Another way to state this is, if using ATLS guidelines to guestimate BP, we are grossly underestimating the degree of hypovolemia our patients have.
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