Carmine Rocco Militano

INTRODUCTION: The beneficial effect of low tidal volume (TV) ventilation strategy on mortality in patients with acute respiratory distress syndrome (ARDS) has been attributed to the protective effect on ventilator-induced lung injury, and yet its effect on cardiovascular function might also play an important role. The aim of this study was to assess whether low TV ventilation improves cardiac output and oxygen delivery compared with high TV ventilation strategy in patients with ARDS. METHODS: In this crossover randomized clinical trial 16 ARDS patients were recruited in an intensive care unit at a university-affiliated hospital. Each patient was ventilated for 30 min with low (6 mL/kg) and 30 min with high (12 mL/kg) TV. The two experimental periods, applied in random order and with allocation concealment, were separated by 30 min of basal ventilation. Minute ventilation was constantly maintained by appropriate respiratory rate changes. RESULTS: Compared with high TV ventilation, low TV ventilation showed decreased pH (7.37 vs. 7.41, P = 0.001) and increased PaCO₂ (49 vs. 43 mmHg; P = 0.002). Cardiac index and oxygen delivery index were increased with low compared with high TV ventilation (3.9 vs. 3.5 L.min⁻¹.m⁻², P = 0.012, and 521 vs. 463 mL.min⁻¹.m⁻², P = 0.002, respectively), while oxygen extraction ratio decreased (0.36 vs. 0.44, P = 0.027). In four patients oxygen extraction ratio was >0.5 during high TV but not during low TV strategy. The magnitude of the change in cardiac index was positively associated with PaCO₂ variation (P = 0.004), while it was unrelated to the magnitude of changes in TV and airway pressure. The decrease of cardiac index was predicted by PaCO₂ reduction, with and area under ROC curve of 0.72. CONCLUSIONS: Our findings suggest that a low TV ventilation strategy increases cardiac index and oxygen delivery, thus supporting the hypothesis that the beneficial effect of low TV ventilation in patients with ARDS could be partially explained by hemodynamic improvement. In other words, low tidal volume ventilation could be protective also for the cardiovascular system and not only for the lung. The slight increase of PaCO₂ during low TV ventilation seems to predict the increase of cardiac index. TRIAL REGISTRATION: ClinicalTrials.gov: NCT00713713.

BACKGROUND: Mean arterial pressure above 65 mmHg is recommended for critically ill hypotensive patients whereas they do not benefit from supranormal cardiac output values. In this study we investigated if the increase of mean arterial pressure after volume expansion could be predicted by cardiovascular and renal variables. This is a relevant topic because unnecessary positive fluid balance increases mortality, organ dysfunction and Intensive Care Unit length of stay. METHODS: Thirty-six hypotensive patients (mean arterial pressure < 65 mmH) received a fluid challenge with hydroxyethyl starch. Patients were excluded if they had active bleeding and/or required changes in vasoactive agents infusion rate in the previous 30 minutes. Responders were defined by the increase of mean arterial pressure value to over 65 mmHg or by more than 20% with respect to the value recorded before fluid challenge. Measurements were performed before and at one hour after the end of fluid challenge. RESULTS: Twenty-two patients (61%) increased arterial pressure after volume expansion. Baseline heart rate, arterial pressure, central venous pressure, central venous saturation, central venous to arterial PCO2 difference, lactate, urinary output, fractional excretion of sodium and urinary sodium/potassium ratio were similar between responder and non-responder. Only 7 out of 36 patients had valuable dynamic indices and then we excluded them from analysis. When the variables were tested as predictors of responders, they showed values of areas under the ROC curve ranging between 0.502 and 0.604. Logistic regression did not reveal any association between variables and responder definition. CONCLUSIONS: Fluid challenge did not improve arterial pressure in about one third of hypotensive critically ill patients. Cardiovascular and renal variables did not enable us to predict the individual response to volume administration. TRIAL REGISTRATION: ClinicalTrials.gov: NCT00721604.

To the Editor-Early tracheotomy is associated with shorter intensive care unit (ICU) stay compared to late tracheotomy, 1 and this procedure could therefore be useful in a context of severely limited resources like the one observed during the novel coronavirus disease 2019 (COVID-19) pandemic. 2 Nevertheless, tracheotomy in COVID-19 patients is considered risky for healthcare workers. ] Data were collected in patients admitted to the ICU of Fondazione Poliambulanza hospital in Brescia (Italy) from February 20, 2020, to May 5, 2020. Two cohorts of healthcare workers were identified: (1) the exposed cohort included doctors and nurses who participated in the early percutaneous tracheostomy procedure as first operator, fiberoscopist, instrumental or anesthesia nurse and (2) the nonexposed cohort included staff on duty in the COVID-19 ICU who never participated in the procedure.