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Is ATLS wrong about palpable blood pressure estimates?

Posted Mar 31 2013 12:00am

In Advanced Trauma Life Support (ATLS), we learn that a carotid, femoral, and radial pulse correlates to a certain systolic blood pressure (SBP) in hypotensive trauma patients.  Specifically ATLS states:
  •   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 are two studies that evaluated this paradigm.
Poulton TJ. ATLS Paradigm Fails. Ann Emerg Med 1988; 17: 107. PMID: 3337405

What they did: In 20 hypovolemic trauma patients with SBP <90 mmHg, the investigators palpated pulses and correlated to BP with sphygmomanometry (BP cuff).
  •  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.

Deakin CD, Low JL. Accuracy of the advanced trauma life support guidelines for predicting systolic blood pressure using carotid, femoral, and radial pulses: observational study. BMJ. 2000 Sep 16;321(7262):673-4. PMID: 10987771

What they did: In 20 pts 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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