The value of early (prehospital) blood glucose testing for trauma victims

The most common cause of raised blood glucose (hyperglycemia) is diabetes but the stress of any acute/critical illnesses as well as traumatic injury is associated with a hypermetabolic state that can result in transitory hyperglycemia. Results of numerous studies have suggested that this so-called “stress-induced hyperglycemia” is an independent predictor of morbidity and mortality among both the critically ill and injured patient. As a consequence, normalization of blood glucose, with insulin therapy if necessary, has become a standard of intensive/critical care.

This highlighted retrospective chart review study focuses on stress-induced hyperglycemia in trauma victims, specifically during the time framed by the incident traumatic event and admission to hospital emergency/trauma care center. The study was designed to assess if prehospital blood glucose concentration is predictive of imminent hypotension and the need for resuscitation. For the purposes of the study hypotension was defined as systolic blood pressure <90 mmHg, and stress hyperglycemia was defined as blood glucose >200 mg/dL or 11.1 mmol/L in the absence of diabetes.

Investigators interrogated the medical records (charts) of all 1623 trauma victims transported by their US air ambulance company during 2018. They identified 107 individuals for study; exclusion criteria included; recorded diagnosis of diabetes, age less than 18 years, no point-of-care glucose recorded, point-of-care glucose <200 mg/dL (11.1 mmol/L).

The study population thus comprised 107 non-diabetic adult trauma victims with stress hyperglycemia (glucose >200 mg/dL, 11.1 mmol/L) identified during initial assessment at the site of the trauma or during air ambulance transfer to hospital (trauma center). For each patient two blood pressure measurements were retrieved: blood pressure at initial assessment and blood pressure on arrival at trauma center.

The primary outcome variable of interest in this study is systolic blood pressure on arrival at the receiving trauma center. Of the 107 study patients, 22 (20.6 %) were hypotensive (systolic BP <90 mmHg) on arrival. Blood glucose was shown to be associated with a statistically significant increased relative risk of hypotension. Statistical analysis revealed that the optimal diagnostic cut-off glucose value for prediction of hypotension was 220 mg/dL.

Of the 22 patients with hypotension on arrival, 19 (86 %) had a point-of-care blood glucose >220 mg/dL. However, 54 % of 85 patients who were not hypotensive on arrival also had a point-of-care glucose >220 mg/dL. Thus, although a cut-off glucose value of 220 mg/dL is shown to have relatively high sensitivity (86 %) for impending hypotension, it is also associated with low specificity and consequent high false positive rate (63 %).

Further evidence that cut-off glucose 220 mg/dL is a valid predictor of hypotension came when the initial and final blood pressures were compared. Patients whose point-of-care glucose was <220 mg/dL had no significant change in mean systolic BP during the period between initial and final assessment, but those with blood glucose >220 mg/dL had significant lowering of systolic BP (mean reduction 13.5 mmHg).

Although, as acknowledged and discussed by the authors, this study has limitations, it provides further evidence of the additional threat to health that stress-induced hyperglycemia poses for trauma victims. It also suggests that point-of-care glucose measurement might be a useful tool for improving the prehospital care of trauma victims. The authors conclude: “Based on these findings, a point of care glucose measurement greater than 220 mg/dl should prompt prehospital clinicians to initiate aggressive balanced resuscitation before arrival at the receiving trauma center in order to prevent worsening hypotension and hemorrhagic shock”.