Dr Charles D. Deakin MA MD MRCP FRCA
Department of Anaesthetics
Southampton General Hospital
Tremona Road
Southampton
SO16 6YD
UK

Tel: 01703-796135
Fax: 01703-794348
E-mail: cdeakin@compuserve.com
 

Abstract

Objectives: To establish the relationship between palpable carotid, femoral and radial pulses and systolic blood pressure.

Design: A sequential, single blinded, observational study.

Setting: Southampton General Hospital N.H.S. Trust.

Subjects: Patients with hypotension secondary to hypovolaemia in whom invasive arterial blood pressure monitoring had been established.

Interventions: Palpation of carotid, femoral and radial pulses.

Main outcome measures: Presence/absence of a pulse as blood pressure increased/decreased.

Results: Using 50% centiles, carotid, femoral and radial pulses are present in patients with a systolic > 70 mmHg, carotid and femoral pulses alone in patients with a systolic > 52 mmHg and only a carotid pulse in patients with a systolic > 42 mmHg.

Conclusions: The Advanced Trauma Life Support (ATLS) course teaching of the relationship between palpable pulses and systolic blood pressure is therefore not supported by this study. ATLS methodology will overestimate the patient’s systolic blood pressure and underestimate the degree of hypovolaemia.
 

Introduction

Hypovolaemic shock is a major cause of morbidity and mortality in trauma patients. Early assessment and appropriate treatment of the hypovolaemia can improve outcome. Assessment of the circulatory state during the primary survey is based on blood pressure, pulse, capillary refill and level of consciousness. Blood pressure may not be immediately available because of delays in attaching monitoring and even when this is established, due to failure to non-invasive blood pressure monitors to detect a weak pulse in hypovolaemic states. As an alternative to sphygnomanometry, assessment of palpable pulses in major vessels has been used as a quick but approximate guide to the systolic blood pressure. The Advanced Trauma Life Support (ATLS) course taught that if only the patient’s carotid pulse is palpable, the systolic blood pressure is between 60-70 mmHg ¹. If both carotid and femoral pulses are palpable, the systolic blood pressure is between 70-80 mmHg and if the radial pulse is also palpable, the systolic blood pressure in above 80 mmHg. The only study to examine the accuracy of this model used non-invasive blood pressure measurements which have a tendency to underestimate systemic arterial BP during hypotension ². No reliable data is therefore available to support the ATLS guidelines upon which clinical decisions are made. A study was therefore undertaken to assess the correlation of palpable radial, femoral and carotid pulses with invasive systolic blood pressure in hypovolaemic patients.
 

Material and Methods

Following Ethics Committee approval, patients who were hypotensive due to hypovolaemia and in whom invasive arterial blood pressure monitoring had been established were studied. An observer blinded to the blood pressure palpated the radial, femoral and carotid pulses at which time the invasive systolic blood pressure was recorded. The presence or absence of each pulse was recorded.

Patients were assessed as hypovolaemic if they were hypotensive with either major blood loss (> 15% estimated blood volume) or if the heart appeared relatively empty on direct inspection. Patients in vasodilated states (e.g. sepsis) were excluded. It was assumed that when a pulse was palpable at a given blood pressure, it remained palpable at higher pressures and when a pulse was not palpable at a given blood pressure, it remained not palpable at lower pressures.
 

Results

Twenty patients were studied. Age ranged from 18-79 years. All patients had been admitted to the intensive care unit or were in the operating theatre at the time of measurement. Not all pulses were palpable when a reading was taken because of impaired patient access secondary to a sterile operating field. Results are shown graphically in figure 1. Data is given in table 1. The radial pulse always disappeared before the femoral pulse which always disappeared before the carotid pulse.

Radial pulse: A palpable radial pulse was present in all patients with a systolic blood pressure of > 79 mmHg. Only 50% patients had a palpable pulse between 70-71 mmHg. No palpable radial pulse was present in patients with a systolic blood pressure of < 51 mmHg.

Femoral pulse: A palpable femoral pulse was present in all patients with a systolic blood pressure of > 76 mmHg. Only 50% patients had a palpable pulse between 52-54 mmHg. No palpable femoral pulse was present in patients with a systolic blood pressure of < 47 mmHg.

Carotid pulse: A palpable carotid pulse was present in all patients with a systolic blood pressure of > 76 mmHg. Only 50% patients had a palpable pulse at 42-47 mmHg. No palpable carotid pulse was present in any patient with a systolic blood pressure of < 37 mmHg.
 

Discussion

In hypovolaemic states, palpable pulses in the radial, femoral and carotid arteries disappear as blood pressure falls. This study confirms that as systolic blood pressure decreases, the palpable radial pulse disappears before the femoral pulse which in turn disappears before the carotid pulse. Using 50% centiles, carotid, femoral and radial pulses are present in patients with a systolic > 70 mmHg, carotid and femoral pulses alone in patients with a systolic > 52 mmHg and only a carotid pulse in patients with a systolic > 42 mmHg. The Advanced Trauma Life Support (ATLS) course teaching of the relationship between palpable pulses and systolic blood pressure is therefore not supported by this study. ATLS methodology will generally overestimate the patient’s systolic blood pressure and therefore underestimate the degree of hypovolaemia.

Use of palpable pulses has been used as a quick and easy method of assessing blood pressure in hypovolaemic patients both in hospital and in pre-hospital settings where direct blood pressure measurement may not be possible. It is also a technique used in triaging mass casualties. This study shows that there is a wide variability between patients using a technique that may underestimate the degree of hypovolaemia. The presence or absence of palpable pulses must therefore be used with caution when using their presence as an estimate of systolic blood pressure.
 

References

1. Collicott PE. Advanced Trauma Life Support course for physicians. Chicago, American College of Surgeons, 1985, p141.
2. Poulton TJ. ATLS paradigm fails. Ann Emerg Med 1988; 17: 107.
 

Funding: None

Conflict of interest: None