The nonlactate gap: a novel predictor of organ failure and mortality following major trauma

Introduction

Early identification of patients who are not fully resuscitated following major trauma improves outcome. However, current markers of clinically occult hypoperfusion, such as lactate and base deficit, have serious limitations, and our aim was to establish a new endpoint of resuscitation.

Methods

In a prospective study conducted in a Level 1 trauma unit, 49 consecutive patients admitted to the trauma ICU were evaluated. Serum electrolytes, albumin, phosphate and lactate were measured on admission. We derived the calculated ion gap using a simplified Stewart–Figge equation, and subtracted the measured serum lactate from the calculated ion gap to obtain the nonlactate gap (NLG).

Results

See Table 1. The NLG discriminated survivors from non-survivors (P = 0.008, analysis of variance). An NLG above 2 mmol/l was associated with an increased risk of mortality (P = 0.010, Fisher's exact test). No patient with an NLG less than 2 mmol/l died; 32.4% of the patients with an NLG above 2 mmol/l died. A NLG above 2 mmol/l also correlated strongly with organ failure (Multiple Organ Dysfunction Syndrome score P = 0.011, Sequential Organ Failure Assessment score P = 0.011, Mann–Whitney U test).

Table 1

Conclusion

We describe the NLG for the first time, and quantify it using simple bedside calculations derived from routine blood investigations. The NLG is an excellent marker for organ failure and death following major injury, and should be used to guide trauma resuscitation.