James A. Alonso

Initial severity of metabolic acidosis predicts the development of acute lung injury in severely traumatized patients

Objectives: First, to determine whether the severity of shock, as measured by systemic hypotension and metabolic acidosis, is significantly associated with a higher risk of acute lung injury in patients with severe trauma. Second, to determine whether the volumes of blood and crystalloid solutions administered in the early posttrauma period are independent risk factors for acute lung injury in severely traumatized patients. Design: Prospective observational study. Setting: Level I urban trauma center in a university hospital. Patients: A total of 102 severely injured, mechanically ventilated trauma patients with an Injury Severity Score ≥16 and aged between 18 and 75 yrs. Interventions: None. Measurements and Main Results: Initial clinical and laboratory data were collected in the emergency department, and on a daily basis thereafter during the patients intensive care unit stay. Of the 102 severely injured patients enrolled, 42 developed acute lung injury (41%) and 60 did not (59%). A total of 93% of the trauma patients who developed acute lung injury during the 17‐month study period were included in the study. Initial base deficit was significantly lower in patients who developed acute lung injury than in those who did not (−8.8 ± 4.5 vs. −5.6 ± 5.1, p < .01). The difference in systolic blood pressure between the two groups was not significant. Conclusions: In this group of severely injured trauma patients, the degree of metabolic acidosis at the time of admission identified those patients with the highest probability of developing acute lung injury. In addition, the volume of crystalloid solution administered during the first 24 hrs was significantly greater in patients who later developed acute lung injury. Finally, there was a significantly higher morbidity in patients who developed acute lung injury, whereas mortality did not differ between the two groups.

Improved flow and pressure capabilities of the Datex-Ohmeda SmartVent anesthesia ventilator

STUDY OBJECTIVE To compare the flow and pressure capabilities of the Datex-Ohmeda SmartVent (Ohmeda 7900, Datex-Ohmeda, Madison, WI) to previous Ohmeda (7810 and 7000, Datex-Ohmeda, Madison, WI) anesthesia ventilators. To determine airway pressure and minute ventilation thresholds for intraoperative use of a critical care ventilator. DESIGN Three anesthesia ventilators and one critical care ventilator (Siemens Servo 900C, Siemens, Solna, Sweden) were studied in a lung model. Retrospective medical record review. SETTING Research Laboratory and Critical Care Unit of a Level I Trauma Center. PATIENTS 145 mechanically ventilated patients treated for acute respiratory failure who underwent 200 surgical procedures. INTERVENTIONS The effect of increasing pressure on mean inspiratory flow was determined by cycling each ventilator through increasing restrictors. Maximum minute ventilation was measured at low compliance (10-30 mL/cm H2O), positive end-expiratory pressure (PEEP) (0-20 cm H2O), and increased airway resistance (approximately 19 and approximately 36 cm H2O/L/sec) in a mechanical lung model. MEASUREMENTS AND MAIN RESULTS Flow, volume, and pressure were measured with a pulmonary mechanics monitor (BICORE CP-100, Thermo Respiratory Group, Yorba Linda, CA). Preoperative peak airway pressure and minute ventilation (VE) were extracted from the medical record. Mean inspiratory flow declined with increasing pressure in all anesthesia ventilators. The SmartVent and the 7810 produced greater mean inspiratory flow than did the 7000 ventilator. As compliance progressively decreased, the Siemens, the SmartVent, and the 7810 ventilators maintained VE compared to the 7000 ventilator. The Siemens and the SmartVent maintained VE with PEEP, compared to the 7810 and 7000 ventilators. During increased airway resistance, maximal VE was lower for all ventilators. The SmartVent met the ventilation requirements in 90% of the patients compared to 67% of patients with the 7000 ventilator. CONCLUSION The improved pressure and flow capabilities of the SmartVent increase the threshold for using a critical care ventilator intraoperatively to a peak airway pressure > 65 cm H2O and/or VE > 18 L/min.

Quantifying the Severity of Acute Lung Injury Using Dead-Space Ventilation: Should the Lung Injury Score Be Updated?

During the past decade of research on acute lung injury (ALI) and acute respiratory distress syndrome (ARDS) there has been heightened interest in measuring physiologic dead-space fraction (VD/VT). Since ARDS first was described 44 years ago, the primary focus on gas exchange abnormalities concerned