Standard vital signs are monitored on scene, en route and upon arrival at hospital, and are considered to be important parameters in any triage system. Haemodynamic stability assessment is critical as patients who are stable are managed very differently from patients who are unstable (Jacoby and Wisner, 2008). In the prehospital setting, patients with injuries that require emergency surgical intervention are an evacuation priority. Haemodynamic stability is an important consideration in determining the destination and urgency of the evacuation process. However, standard vital signs are neither sensitive nor specific for haemodynamic instability and may be inadequate for early detection of a requirement to implement an intervention (Orlinsky et al, 2001).
Haemodynamic stability is a somewhat illusory concept and one for which there is no consensus definition (Scalea and Henry, 1992). Hypotension (systolic blood pressure (SPB) <90 mmHg in an adult) is generally considered to be worthy of concern and a high index of suspicion for ongoing haemorrhage should be maintained. However, patients sustaining severe trauma are at significant risk for haemorrhage, even if they are normotensive in the field. There is a special importance to define the indices that indicate the highest probability of such injuries (Cherry et al, 2007), but the best method to identify those patients is yet to be established (Bond et al, 1997).
Laboratory and imaging studies obtained in the emergency department (ED) help to identify the source and magnitude of bleeding. For instance; arterial blood gases are extremely valuable in assessing perfusion deficits (Rutherford, 1992). Unfortunately, laboratory and imaging studies are not available in the field, and even if they were, they would not reveal changes so soon after the injury. In most cases, patients who have been haemodynamically unstable require a faster trip to the operating room. As stated, the blood pressure and the pulse rate are crude methods of evaluating perfusion. Hence, to prevent undertriage, additional triage criteria such as a penetrating injury to the torso and paramedic judgment are being used in most trauma systems (Sava et al, 2002; Lin et al, 2010).
Until new technologies for the early detection of shock come into use, the standard vital signs will remain the key determinants for activation of hospital trauma teams. Comparing the ED vital signs to the prehospital vital signs may be valuable—stable vital signs over time are expected to identify the patients who are not actively bleeding (Esposito et al, 1995).
The purpose of this prospective study is to re-evaluate changes in vital signs of trauma victims from the prehospital to the hospital setting, and their associations with injury severity and a need for an emergency operation. Better interpretation of the vital signs can improve the activation of the trauma system, and reduce over and under triage.
Materials and methods
This study was approved by the University of Miami institutional review board. From 1 July to 30 September 2007, Ryder Trauma Centre patients were prospectively entered into the study if they met the Miami-Dade county trauma centre triage criteria. Patients were excluded from the study for: age less than 15; thermal, chemical and electrical injury; patients experiencing a cardiac arrest before any surgical procedure; those transferred from another hospital, and when adequate prehospital data could not be obtained. Demographic data collected were: age, sex, mechanism of injury, injury time (as estimated by the 911 call), hospital arrival time and the trauma alert criteria as determined by the paramedics. The Glasgow coma score (GCS), heart rate (HR), SBP, respiratory rate (Resp) and pulse oximetry values (SaO2) were measured and recorded during prehospital transport and on arrival at the hospital. Prehospital GCS ≤12, BP ≤90 and a combination of HR ≥120 with Resp ≥30 mandates trauma team activation in Miami Dade County.
All major surgical procedures were graded by the team as: emergency (a lifesaving operation is needed within minutes), urgent (a lifesaving operation is needed within hours), and not urgent. Open fractures were referred as not urgent in this study. In order to reduce bias, the classification of the surgical procedure was approved by one of the investigators. For all the patients, the injury severity score (ISS) was calculated following completion of all diagnostic work-up. The length of intensive care unit (ICU) stay was added later to the data collection sheet. Patients were classified as major trauma victims when their calculated ISS was 16 or greater, when they needed emergency surgery and when they needed ICU care. A further subdivision to a ‘very severe trauma’ for patients with an ISS ≥25 was performed. All other patients were categorized as ‘over triaged’, meaning that the trauma team activation was in fact unnecessary; with a further subdivision to an ‘obvious over triaged’ for patients who stayed in the hospital less than 24 hours.
Variables are expressed as the number of cases and percentage for categorical data (GCS) and as means and standard deviations for numerical data (BP, HR, Resp, SaO2). These vital signs were set as independent variables. Dependent variables were the classification into groups of major trauma or over triage, and the need for an emergency operation. Associations were analyzed using the chi-squared test. The results are given as relative risks (RR) with the 95% confidence intervals (95% CI). The prehospital vital signs were compared to the admission vital signs using paired students T-test. The statistical significance level was set at 5% (P ≥0.05).
Results
Demographics
A cohort of 601 patients who met inclusion criteria represents the study population. This group includes 490 men and 111 women. The mean age was 38.25 ± 18.43 years (range 15–100)—103 of the patients were more than 55 years old. Injury mechanisms were blunt in 417 cases: motor vehicle collisions (MVC)—192; pedestrian hit by car (PHBC)—52; motorcycle (including ATV) collisions (MCC)—58; falls—65; water sports—7; industrial accidents—14, and assaults—29. 184 (30.6%) patients suffered a penetrating mechanism: Gun shot wounds (GSW)— 104 and stab wounds (SW)—80. The mean time from injury to hospital arrival was 44.8 ± 17.63 minutes (range 10–144 minutes). The mean time from injury to hospital arrival was not significantly different for the wounded who needed emergency surgical treatment (43.4 ± 11.7, P=0.57).
Two hundred and forty-three patients were defined as major trauma (40%). One hundred and twenty-six (21%) major trauma patients had an ISS of 25 or more. The mean ISS of the cohort was 14.32 ± 13.71 (range 1–75). Thirty-nine patients required an emergency operative intervention: 24 for active bleeding (liver 7, spleen 3, other abdominal 4, neck 2, femoral vessels 2 and massive haemothorax 2); 5 patients sustained a pericardial tamponade whereas 10 patients required an immediate neurosurgical intervention for imminent cerebral herniation (5 had an epidural haematoma and 5 had a subdural haematoma). A further 42 patients underwent urgent operations (which could have been delayed for several hours). The disposition of patients was as follows: ICU—148 patients; regular floors—262 patients; discharged from the ER—168 patients; expired in the operating room (OR)—17 patients. The mean ICU stay was 17.84 ± 22.03 days (range 1–120). The median ICU stay was 6 days. Overall, the cohort experienced a 38/601 (6.3%) incidence of mortality (17 patients died in the OR and 21 succumbed to their illness in the intensive care unit (ICU) (Table 1).
| Characteristics | Value |
|---|---|
| Age | 38.25–18.43 years (range 15–100) |
| Age > 55 | 103 (17.14%) |
| Men | 490 (81.26%) |
| Women | 111 (18.74%) |
| Time from injury to hospital | 44.8 ± 17.63 minutes (range10–144) |
| ISS | 14.32 ± 13.71 (range 1–75) |
| Overtriage | 358 (60%) |
| Obvious overtriage (hospital stay < 24 hrs) | 168 (28%) |
| ISS≥25 | 126 (21%) |
| Injury mechanisms—blunt | 417 (69.38%) |
| Motor vehicle crash (MVC) | 192 |
| Pedestrian hit by car (PHBC) | 52 |
| Motorcycle crash (MCC) | 58 |
| Fall | 65 |
| Water sports | 7 |
| Industrial/crush | 14 |
| Assault | 29 |
| Injury mechanisms—penetrating | 185 (30.62%) |
| Gunshot wounds (GSW) | 104 |
| Stab wound (SW) | 80 |
| Emergency operation | 39 |
| Bleeding control | 24 |
| Pericardial tamponade | 5 |
| Neurosurgical emergency | 10 |
| Urgent operations | 42 |
Vital signs measurements
GCS
One hundred and twenty-eight patients had a prehospital GCS ≤12, 90 of them were defined as sustaining major trauma. In 65 of them, the ISS was 25 or more (RR, 95% CI: 3.00, 1.98–4.53; 6.97, 4.49–10.81; respectively). Twenty of these 128 patients needed an emergency surgical procedure (RR, 95% CI 4.43, 2.28–8.58). One patient from the 473 with a GCS ≥14 in the field and no one from the 483 patients with a GCS ≥14 on admission needed a neurosurgical procedure.
GCS values changed significantly from the field to the hospital (Table 2). The admission GCS as obtained in the ER was significantly higher than the field GCS as obtained by the paramedics for the entire cohort. For the subgroup of patients (n=112) with a GCS ≤12, the mean GCS increased 1.64 points (P <0.001). For the subgroup of patients (n=47) with a GCS ≤8, the mean GCS increased 4.81 points (P <0.01). Overall, 10 patients needed an immediate neurosurgical intervention (5 to evacuate a subdural haematoma and 5 to evacuate an epidural haematoma). In eight cases, both the prehospital and the admission GCS was 8 or less. In one case, the prehospital GCS was 11, and the score decreased to 8 on admission. In another case of an epidural haematoma, the admission GCS was 13 and the score decreased to 8 over the next 60 minutes.
| Prehospital parameter | No | Major trauma | ISS ≥ 25 | Emergency operation | Change (Mean) | |
|---|---|---|---|---|---|---|
| GCS ≤ 12 | 128 | 90* | 65* | 20* | +1.64* points | |
| RR | 3.00 | 6.97 | 4.43 | |||
| 95% CI | 1.98–4.53 | 4.49–10.81 | 4.49–10.81 | 2.28–8.58 | ||
| GCS ≤ 8 | 47 | +4.81* Points | ||||
| SBP ≤ 90 mmHg | 63 | 52* | 37* | 21* | +23.8* mmHg | |
| RR | 4.60 | 5.23 | 11.69 | |||
| 95% | 2.67–7.94 | 3.12–8.75 | 5.85–23.36 | |||
| Mean HR | 94.8±20.74 bpm | NS | ||||
| HR ≥ 120 | 68 | NS | NS | NS | ||
| Increased HR (≥20) | 72 | NS | NS | NS | ||
| Decreased HR (≥20) | 65 | NS | NS | NS |
*Significant; NS = Non-significance
Blood pressure
Sixty-eight patients had a SBP ≤90 mmHg in the field. 55 of them were defined as sustaining major trauma. In 37 of them, the ISS was 25 or more (RR, 95% CI: 4.60, 2.67–7.94; 5.23, 3.12–8.75; respectively). 21 of the 68 patients needed an emergency surgical procedure (16 for bleeding; 5 for neurosurgery) (RR, 95% CI 11.69, 5.85–23.36). A significant increase in blood pressure was observed during the evacuation period, with a mean elevation of 23.8 mmHg, while 26 of the 68 patients with a prehospital SBP ≤90 had an admission SBP >90. 13 patients with prehospital SBP ≤90 and 15 patients with an admission SBP ≤90 were only mildly injured.
A separate analysis has focused on the non-hypotensive patients (defined as SBP >90 mmHg). A SBP >90 on admission, but not a prehospital SBP >90, which was significantly associated with no need for an emergency bleeding control; 13/533 (2.4%) patients with a prehospital SBP >90, and only 2/542(0.4%) patients with a SBP >90 on admission needed an emergency bleeding control (P <0.01).
Heart rate (HR)
The HR was not associated with injury severity or a need for emergency surgery. The mean prehospital heart rate was 94.80 ± 20.74 and the mean admission HR was 98.28 ± 32.97. Sixty-eight patients had a prehospital HR ≥120 beats per minute (bpm). Change of 20 or more bpm was measured in 137 patients. 72 patients increased their HR by 20 or more bpm (23 of them to more than 120 bpm), from the prehospital measurement to the admission measurement, and 65 patients decreased their HR by 20 bpm or more. Still, there was no association with injury severity or a need for an emergency surgery in all these subgroups analysis.
Respiratory rate and SaO2
An orotracheal intubation or an attempted intubation had been performed at the scene on 40 patients. For those who were not intubated, the O2 saturation and respiratory rate were not associated with major trauma, and their values have not changed significantly from the prehospital to the hospital setting.
Discussion
Current trauma triage relies on abnormal physiologic criteria to determine a patient's mode of transport; priority of treatment; destination for treatment; injury severity; mortality; and need for possible life-saving interventions. Most of the existing triage tools are based on the presence of abnormal vital signs in the patient. Common vital signs are used because these measurements are usually readily obtainable at the site of injury.
GCS has been previously considered as the most reliable triage criterion (Norwood et al, 2002). Routinely, the GCS of the trauma victim is reported to our trauma centre by the paramedic at the scene. We found that a GCS of 12 or less predicts severe trauma and a need for an emergency operation. It is well accepted that low GCS is highly predictive of the need for urgent interventions but the exact break point in the GCS score at which it becomes predictive has not been identified. A GCS as high as 14 and as low as 8 has been proposed to mandate full trauma team activation (Norwood et al, 2002; Lehmann et al, 2007). Although Ochsner et al (1995) have found a GCS of 12 as a cause for a high rate of over triage, the current study justifies our policy of referring a GCS of 12 as the threshold for trauma team activation.
In many cases, the GCS on arrival to the hospital was higher than that measured in the field. Some of the cases probably represent a brain concussion with an expected improvement in level of consciousness during the first hour post-injury. It is also possible that paramedics tend to underestimate the level of consciousness. Accurate assessment of the GCS is important as more selective evacuation of patients sustaining brain injuries to medical centres that have a neurosurgery service may improve outcome and save resources. As patients with a GCS ≥14 on admission did not require any neurosurgical procedure, recalculation of the GCS on admission may modify the trauma team activation and patient disposition from the emergency department (Norwood et al, 2002). An admission GCS ≥14 indicates that further work-up of intracranial injury can be delayed.
The American College of Surgeons Committee on Trauma currently recommends that injured patients with a prehospital systolic blood pressure ≤90 mm Hg be triaged to trauma centers (2008). However, a SBP ≤90 mmHg is a late sign of haemorrhagic shock as it only occurs after a loss of 30–40% of the circulating blood volume. The physiology of the trauma patients suffering from severe haemorrhage is often dynamic and may not reflect the true degree of hypoperfusion present because of normal physiologic compensatory mechanisms.
Significant bleeding and hypoperfusion may occur in blunt and penetrating trauma patients, despite normal standard vital signs—especially in young, healthy patients. Indeed, eight patients had normal blood pressure, despite uncontrolled bleeding. Since haemodynamic stability does not reliably exclude significant haemorrhage, a penetrating injury to the trunk requires immediate evacuation (Brown et al, 2005; Lin et al, 2010). A central nervous system injury can further confound the interpretation of vital signs values (Mahoney et al, 2003).
When the systolic blood pressure is 90 mmHg or lower in an adult, a high index of suspicion for ongoing haemorrhage should be maintained, although Eastridge et al (2007) indicates a BP as high as 110 mm to be worthy of concern. In our study, 21 of the 68 patients with a low prehospital SBP (30.9%) needed operative bleeding control. Obviously, a low prehospital blood pressure cannot differentiate between controlled and uncontrolled bleeding. Even when bleeding ceased, immediate post injury blood pressure can be low before activation of compensatory mechanisms and/or fluid resuscitation. When the bleeding is self-limited, the BP is expected to rise over time, and when the SBP >90 on admission, an emergency operation is rarely needed (only 2/542 (0.4%) patients in this study).
To note, alcohol and other substances abuse are quite common in trauma patients. They may influence blood pressure and compensatory mechanisms and further decrease the SBP sensitivity to the haemodynamic status.
Tachycardia is often listed as an important sign in the initial diagnosis of haemorrhagic shock (ACS 2008). However, its sensitivity and specificity limit its usefulness in the initial evaluation of trauma victims (Victorino et al, 2003). We found that the heart rate is not a good indicator of the haemodynamic status. Although a HR >100 bpm is considered tachycardia, even a HR ≥ 120 bpm did not help to identify major injuries. A change overtime of 20 or more bpm, as measured in 137 patients, did not indicate any significant change in perfusion. Therefore, no triage or management decisions can be based on the HR as a single parameter. Investigators continue to look for other methods to evaluate the physiology of the wounded. Heart rate variability is affected by severe blood loss and may be a better triage parameter than the traditional vital signs (Batchinsky et al, 2007). A study to evaluate the benefits of this technology is currently planned by the authors.
Conclusion
In summary, physiological parameters are limited in their ability to detect serious injuries and a need for emergency surgical intervention. Integration with anatomical criteria is therefore required for a better triage. However, in the near future, until technological breakthrough, the vital signs will continue to have a major role in triage. A better interpretation of the vital signs values can improve our trauma system.