Lung ultrasound as a bedside tool for assessment of extra vascular lung water in critically ill head injured patients - An observational study

Introduction: Incidence of pulmonary edema in patients with traumatic brain injury is 11-71%. Early detection of Extra Vascular Lung Water (EVLW) helps in better clinical outcome of the patient. Primary objective of the study was to identify the presence of extravascular lung water seen as >3 B lines per lung field, using lung ultrasound in critically ill head injured patients. Secondary objectives were to compare the diagnostic accuracy and delay in identification of EVLW using chest x ray versus lung ultrasound. Association of EVLW with duration of mechanical ventilation and ICU stay was observed. Methods: This observational study was conducted in Trauma ICU, Advanced Trauma Centre, PGIMER, Chandigarh during study period of Sep 2015 to Dec 2016. After Ethical clearance (IEC No. INT/IEC/2015/372), a total of 120 patients with head injury requiring mechanical ventilation and critical care were enrolled in the study. Daily routine chest x ray and daily bedside lung ultrasound were done from the day of ICU admission until the patient was on mechanical ventilator support. Results: Incidence of pulmonary edema in our study was found to be 61.67% (n = 74/120, p value <0.001). Lung ultrasound was the initial method of detection of EVLW in n = 68/74, 91.9% and it was both chest X-ray and ultrasound in n = 6/74, 8.1%. Of the 74 patients who showed pulmonary edema on lung ultrasound, chest x ray could identify pulmonary edema in only 49 patients. The mean time gap between identification of EVLW by using lung ultrasound and chest X-ray was 1.42 ± 0.77 days. Conclusions: Lung ultrasound is a good bedside investigative modality for early detection of EVLW compared to routine chest X-ray in critically ill head injured patients. There is a significant association between duration of mechanical ventilation and ICU stay with the presence of EVLW.