Columns, Patient Care, Trauma

Assessing the Accuracy of the Signs of Shock

Issue 5 and Volume 39.

Mutschler M, Nienaber U, Münzberg M, et al. Assessment of hypovolaemic shock at scene: Is the PHTLS classification of hypovolaemic shock really valid? Emerg Med J. 2014;31(1):35–40.

The EMS Science
Study objective: Validation of the classification of hypovolaemic shock suggested by the prehospital trauma life support (PHTLS) in its sixth student course manual.

Methods: Adults, entered into the TraumaRegister DGU database from 2002 to 2011, were classified into reference ranges for heart rate (HR), systolic blood pressure (SBP) and Glasgow coma scale (GCS) according to the Prehospital Trauma Life Support (PHTLS) classification of hypovolemic shock. First, patients were grouped by a combination of all three parameters (HR, SBP and GCS) as suggested by PHTLS. Second, patients were classified by only one parameter (HR, SBP or GCS) according to PHTLS and alterations in the remaining two parameters were assessed. Furthermore, subgroup analysis for trauma mechanism and traumatic brain injury (TBI) were performed.

Results: Out of 46,689 patients, only 12,432 (26.5%) could be adequately classified according to PHTLS if all three criteria was assessed. In TBI patients, only 12.2% could be classified adequately, whereas trauma mechanism had no significant influence. When patients were grouped by HR, there was only a slight reduction in SBP. When grouped by SBP, GCS dropped from 14 to 8, while no significant tachycardia was observed in any group. In patients with a GCS less than 12, HR was unaltered whereas SBP was slightly reduced to 114 (±42) mmHg. On average, GCS in TBI patients was lower within all shock groups. In penetrating trauma patients, changes in HR and SBP were more distinct, but still less than predicted by PHTLS.

Conclusions: The PHTLS classification of hypovolemic shock displays substantial deficits in adequately risk-stratifying trauma patients.

Mangement of critically ill trauma patients requires rapid identification of shock.

Mangement of critically ill trauma patients requires rapid identification of shock. Photo Raul Torres


Medic Karen Wesley Comments
Management of critically ill trauma patients requires rapid identification of shock. Fortunately, shock presenting with hypotension isn’t hard to identify.

Shock in the trauma patient is most often the result of hypovolemia. In the prehospital setting, scene management often becomes a distracting factor in recognizing patients who are beginning to exhibit signs and symptoms
of shock.

After scene safety, our first contact with the patient gives us vital information that could make our determination of the potential severity of injury. We assess the level of consciousness and do our primary assessment of circulation by examining skin color and rate and quality of pulses. Too often, actual vital signs of blood pressure and pulse rate aren’t taken until extrication and movement to the confines of the ambulance. We’re taught assessment of rate and quality of pulse, and absence of peripheral pulses, is enough to make our status determination. So while minutes pass in getting to vital signs (beginning of secondary assessment), we’re losing valuable time to getting a good evaluation of potential shock.

The study points out what we already know: the first set of vital signs taken may be during a state of compensation, and can’t stand alone. Prehospital providers and ED staff need to be on the same page, and reports to the receiving facility need to reflect the severity of the patient. Reporting mental status and trending vitals is inherent to appropriate triage of patients arriving in the ED.

The volume of patients studied in this paper clearly indicates that altered mental status is the first sign of shock. PHTLS and advanced trauma life support (ATLS) both look at GCS scores and vital sign numbers as the signs we should be using to evaluate our patients.

It may be time to review and revise our trauma evaluation by looking at shock index versus vital sign changes. Using the ratio of heart rate to SBP may help identify hypo-perfused patients with more subtle vital sign abnormalities sooner.

Doc Wesley Comments
To be fair to PHTLS and ATLS, this study was concerned with the shock classification in the sixth edition of these courses. The seventh and current edition removed level of consciousness from that classification scheme. (See Table 1.)

PHTLS & ATLS classifications of shock, seventh edition version

Since 50% of major trauma victims have an associated head injury with altered level of consciousness, GCS alone isn’t predictive of shock. However, this study showed that even in the absence of an altered GCS, heart rate and blood pressure were only 25% accurate in classifying the severity of shock.

These “classification schemes” should be taken with a grain of salt because they aren’t based on large numbers of injured patients. They were derived from early studies of young healthy military recruits who were stressed into shock by various means. The classifications were further refined from actual military experience, which for the most part related to penetrating trauma. The majority of trauma patients treated by U.S. EMS are blunt mechanisms and the age range is greater than in the study. Older patients may not show classic shock vital signs due to prescription medication use and impaired mechanisms of compensation.

The authors do suggest utilizing the shock index (SI) to classify shock. The SI is obtained by dividing the pulse by systolic blood pressure. Normal SI is 0.5–0.7. Studies have shown that patients with SI greater than 0.9 are 50% more likely to be in profound shock. However, the authors didn’t analyze the SI in this study but instead focused on the inadequacy of the PHTLS
shock classification.

The bottom line for me is that shock can’t be defined by any combination of vital signs but must be determined based on overall presentation and evidence of hypoperfusion such as skin color, tone and quality of pulses. Any altered mental status should be considered a sign of shock and the patient should be quickly transported to the nearest, and highest-level, trauma center.

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