Utility of POCUS in estimating blood volume in neurocritical patients with hyponatremia, in the Polyvalent Intensive Care Unit of the Viedma Clinical Hospital

Introduction: Hyponatremia is one of the most common hydroelectrolytic disorders in patients with neurocritical pathology. Estimating blood volume in critically ill patients with hyponatremia is a challenge, and this is where point-of-care ultrasound (POCUS) becomes relevant.Methods: An observational, analytical, prospective, and longitudinal study was conducted in an ICU with a high influx of neurocritical patients. Thirty-one neurocritical patients who developed acute hyponatremia participated. They were evaluated clinically, analytically, and underwent ultrasound measurements at the bedside of the patients. It was determined which of the variables (clinical, analytical, and ultrasound) achieved the greatest sensitivity and specificity when determining blood volume. Results: More than half developed hyponatremia during their stay in the ICU, the predominant gender was male with more than 61% and more than 77% had a diagnosis of head trauma. The ROC curve was able to show that the ultrasound variables presented a sensitivity of 93% and specificity of 94% with an area under the curve (AUC) of 0.93. And of these (ITV, GC, Echo-pulmonary, VEXUS and IVC indices) were the ones that best predict blood volume. In our survival analysis (Kaplan Meier) we found a mean survival of 37.5 days (36.4 - 38.49) in the group (Hypovolemic = CPS), compared to a mean survival of 27.7 days (25.4 - 29.9) in the group (Normo-hypervolemic = SIADH) (CI 95% P: 0.078), which expresses higher mortality in those neurocritical patients who developed acute hyponatremia (Normo-hypervolemic = CPS).Conclusions:More than half of the neurocritical patients developed hyponatremia during their stay in the ICU, the mean age of the patients was 44 for the hypovolemic group and 35 for the normo-hypervolemic group, the predominant gender was male and most had a diagnosis of head trauma. POCUS (LUS, VEXUS, FoCUS) showed higher sensitivity and specificity in predicting blood volume in neurocritical patients with acute hyponatremia. The time to resolution of hyponatremia after starting treatment was a median of 3 days in the hypovolemic group, in contrast to the normo-hypervolemic group, which required more time, and no cases of overcorrection were reported in either group. Neurocritical patients with acute hyponatremia (Hypovolemic = CPS) would have more days of survival compared to neurocritical patients with acute hyponatremia (Normo-hypervolemic = SIADH)