[Evidence of occult systemic hypoperfussion in head injured patients. Preliminary study]

To determine the correlation between blood lactic acid levels in the first 48 hours and outcome, in hemodynamically stable patients, with moderate or severe head injury (HI), and to investigate the risk factors associated with abnormal lactate levels.

A prospective observational study, in 210 adults patients with moderate or severe head injury. When the patients were hemodynamically stable, blood lactate concentrations were measured once on admission, twice daily during the first 2 days and once daily until lactate levels were normalized. The whole group 210 patients were divided into 2 groups. Group 1: (LA < 2.2 mmol/L) patients without occult hypoperfussion (OH), and group 2: (LA >or= 2.2 mmol/L) patients with OH.

One hundred and fifteen patients (57.76%) were categorized as group 1, and 95 patients (45.24%) as group 2. In the univariate analysis of risk factors for blood lactate >or=2.2 mmol/L the following variables showed statistical significance: severity of the head injury measured by several scales [Glasgow Coma Scale (GCS), Injury Severity Score (ISS), Revised Trauma Score (RTS) and Acute Physiology and Chronic Health Evaluation (APACHE) II], arterial hypotension, hypoxemia, anaemia, hyperglucemia, hypothermia, a greater incidence of norepinephrine infusion, and the higher percentage of type II lesions in the head computerized tomography at admission showed in the group 1 (53.91% vs. 38.94%) (p<0.03). In the multiple logistic regression analysis only two variables were risk independently associated with elevated blood lactate concentration: APACHE II in the first 24 hours: OR 1.12 (95% IC 1.06--1.196; p<0.0001) and the first 48-hours total fluid infusion volumes: OR 1.09 (95% IC 1.021,16; p < 0.0001). The infection rate (63.2% vs 47.8%, p=0.026), and length of ICU stay [mediana (percentil 25--75)] [13.29 (7.11--21.22) days vs. 8.78 (4.40--16.72) days; p<0.018] were significantly higher in patients with blood lactate >or=2.2 mmol/L (group 2). Although, the percentage of intracranial hypertension and mortality was higher in the group 2, there was no significant difference. In the multivariate analysis, the increase of blood lactate concentration, was not independently associated as a risk factor with studied complications.

The presence of OH in patients with moderate or severe head injury, with postres uscitation arterial pressure, according to present recommendations, is associated with a more severe head injury, showed by APACHE II and the total fluid infusion volumes in the first 48 hours. OH in head injury increases the infection rate and length of ICU stay.