Determinants of acute kidney injury during high-power mechanical ventilation: secondary analysis from experimental data.

BACKGROUND: The individual components of mechanical ventilation may have distinct effects on kidney perfusion and on the risk of developing acute kidney injury; we aimed to explore ventilatory predictors of acute kidney failure and the hemodynamic changes consequent to experimental high-power mechanical ventilation. METHODS: Secondary analysis of two animal studies focused on the outcomes of different mechanical power settings, including 78 pigs mechanically ventilated with high mechanical power for 48 h. The animals were categorized in four groups in accordance with the RIFLE criteria for acute kidney injury (AKI), using the end-experimental creatinine: (1) NO AKI: no increase in creatinine; (2) RIFLE 1-Risk: increase of creatinine of > 50%; (3) RIFLE 2-Injury: two-fold increase of creatinine; (4) RIFLE 3-Failure: three-fold increase of creatinine; RESULTS: The main ventilatory parameter associated with AKI was the positive end-expiratory pressure (PEEP) component of mechanical power. At 30 min from the initiation of high mechanical power ventilation, the heart rate and the pulmonary artery pressure progressively increased from group NO AKI to group RIFLE 3. At 48 h, the hemodynamic variables associated with AKI were the heart rate, cardiac output, mean perfusion pressure (the difference between mean arterial and central venous pressures) and central venous pressure. Linear regression and receiving operator characteristic analyses showed that PEEP-induced changes in mean perfusion pressure (mainly due to an increase in CVP) had the strongest association with AKI. CONCLUSIONS: In an experimental setting of ventilation with high mechanical power, higher PEEP had the strongest association with AKI. The most likely physiological determinant of AKI was an increase of pleural pressure and CVP with reduced mean perfusion pressure. These changes resulted from PEEP per se and from increase in fluid administration to compensate for hemodynamic impairment consequent to high PEEP.

Impact of mechanical power and positive end expiratory pressure on central vs. mixed oxygen and carbon dioxide related variables in a population of female piglets.

INTRODUCTION: The use of the pulmonary artery catheter has decreased overtime; central venous blood gases are generally used in place of mixed venous samples. We want to evaluate the accuracy of oxygen and carbon dioxide related parameters from a central versus a mixed venous sample, and whether this difference is influenced by mechanical ventilation. MATERIALS AND METHODS: We analyzed 78 healthy female piglets ventilated with different mechanical power. RESULTS: There was a significant difference in oxygen-derived parameters between samples taken from the central venous and mixed venous blood (S v ¯ $$ \overline{v} $$ O2 = 74.6%, ScvO2 = 83%, p < 0.0001). Conversely, CO2-related parameters were similar, with strong correlation. Ventilation with higher mechanical power and PEEP increased the difference between oxygen saturations, (Δ[ScvO2-S v ¯ $$ \overline{v} $$ O2 ] = 7.22% vs. 10.0% respectively in the low and high MP groups, p = 0.020); carbon dioxide-related parameters remained unchanged (p = 0.344). CONCLUSIONS: The venous oxygen saturation (central or mixed) may be influenced by the effects of mechanical ventilation. Therefore, central venous data should be interpreted with more caution when using higher mechanical power. On the contrary, carbon dioxide-derived parameters are more stable and similar between the two sampling sites, independently of mechanical power or positive end expiratory pressures.

Estimation of normal lung weight index in healthy female domestic pigs.

INTRODUCTION: Lung weight is an important study endpoint to assess lung edema in porcine experiments on acute respiratory distress syndrome and ventilatory induced lung injury. Evidence on the relationship between lung-body weight relationship is lacking in the literature. The aim of this work is to provide a reference equation between normal lung and body weight in female domestic piglets. MATERIALS AND METHODS: 177 healthy female domestic piglets from previous studies were included in the analysis. Lung weight was assessed either via a CT-scan before any experimental injury or with a scale after autopsy. The animals were randomly divided in a training (n = 141) and a validation population (n = 36). The relation between body weight and lung weight index (lung weight/body weight, g/kg) was described by an exponential function on the training population. The equation was tested on the validation population. A Bland-Altman analysis was performed to compare the lung weight index in the validation population and its theoretical value calculated with the reference equation. RESULTS: A good fit was found between the validation population and the exponential equation extracted from the training population (RMSE = 0.060). The equation to determine lung weight index from body weight was: [Formula: see text] At the Bland and Altman analyses, the mean bias between the real and the expected lung weight index was - 0.26 g/kg (95% CI - 0.96-0.43), upper LOA 3.80 g/kg [95% CI 2.59-5.01], lower LOA - 4.33 g/kg [95% CI = - 5.54-(- 3.12)]. CONCLUSIONS: This exponential function might be a valuable tool to assess lung edema in experiments involving 16-50 kg female domestic piglets. The error that can be made due to the 95% confidence intervals of the formula is smaller than the one made considering the lung to body weight as a linear relationship.

Early time-course of respiratory mechanics, mechanical power and gas exchange in ARDS patients.

PURPOSE: To describe the clinical course of ARDS during the first three days of mechanical ventilation, to compare ventilatory setting, respiratory mechanics and gas exchange variables collected during the first three days of mechanical ventilation between patients who survived and died during intensive care unit (ICU) stay and to investigate the variables associated with mortality at ICU admission and throughout the first three days of mechanical ventilation. MATERIALS AND METHODS: Prospective observational study. Mechanically ventilated ARDS patients were studied at ICU admission and for the following three days. Univariate logistic regression models were performed for PaO2/FiO2 ratio, driving pressure and alveolar dead space fraction and for mechanical power and mechanical power ratio. RESULTS: Mechanical power ratio was higher in non survivors at ICU admission and over time; PaO2/FiO2 ratio was higher in survivors with a similar behavior over time in the two groups while alveolar dead space fraction was similar at ICU admission and over time between groups. Mechanical power ratio was the only physiological variable which remained consistently associated with ICU mortality throughout the study. CONCLUSIONS: The alteration in oxygenation, dead space, and mechanical power ratio should be assessed not at intensive care admission, but during the first days of mechanical ventilation to better predict outcome.

The intraoperative management of robotic-assisted laparoscopic prostatectomy.

PURPOSE OF REVIEW: Robotic-assisted laparoscopic radical prostatectomy has become the second most commonly performed robotic surgical procedure worldwide, therefore, anesthesiologists should be aware of the intraoperative pathophysiological consequences. The aim of this narrative review is to report the most recent updates regarding the intraoperative management of anesthesia, ventilation, hemodynamics and central nervous system, during robotic-assisted laparoscopic radical prostatectomy. RECENT FINDINGS: Surgical innovations and the advent of new technologies make it imperative to optimize the anesthesia management to provide the most holistic approach possible. In addition, an ageing population with an increasing burden of comorbidities requires multifocal attention to reduce the surgical stress. SUMMARY: Total intravenous anesthesia (TIVA) and balanced general anesthesia are similar in terms of postoperative complications and hospital stay. Reversal of rocuronium is associated with shorter hospital stay and postanesthesia recovery time. Adequate PEEP levels improve oxygenation and driving pressure, and the use of a single recruitment maneuver after the intubation reduces postoperative pulmonary complications. Restrictive intravenous fluid administration minimizes bladder-urethra anastomosis complications and facial edema. TIVA maintains a better autoregulation compared with balanced general anesthesia. Anesthesiologists should be able to optimize the intraoperative management to improve outcomes.

Ventilation strategy during urological and gynaecological robotic-assisted surgery: a narrative review.

Robotic-assisted surgery has improved the precision and accuracy of surgical movements with subsequent improved outcomes. However, it requires steep Trendelenburg positioning combined with pneumoperitoneum that negatively affects respiratory mechanics and increases the risk of postoperative respiratory complications. This narrative review summarises the state of the art in ventilatory management of these patients in terms of levels of positive end-expiratory pressure (PEEP), tidal volume, recruitment manoeuvres, and ventilation modes during both urological and gynaecological robotic-assisted surgery. A review of the literature was conducted using PubMed/MEDLINE; after completing abstract and full-text review, 31 articles were included. Although different levels of PEEP were often evaluated within a protective ventilation strategy, including higher levels of PEEP, lower tidal volume, and recruitment manoeuvres vs a conventional ventilation strategy, we conclude that the best PEEP in terms of lung mechanics, gas exchange, and ventilation distribution has not been defined, but moderate PEEP levels (4-8 cm H2O) could be associated with better outcomes than lower or highest levels. Recruitment manoeuvres improved intraoperative arterial oxygenation, end-expiratory lung volume and the distribution of ventilation to dependent (dorsal) lung regions. Pressure-controlled compared with volume-controlled ventilation showed lower peak airway pressures with both higher compliance and higher carbon dioxide clearance. We propose directions to optimise ventilatory management during robotic surgery in light of the current evidence.

Risk Factors and Mortality in Elderly ARDS COVID-19 Compared to Patients without COVID-19.

During the last few decades, due to the increase in elderly patients among the general population, the number of patients aged over 80 years admitted in intensive care significantly incremented [...].

Long term feasibility of ultraprotective lung ventilation with low-flow extracorporeal carbon dioxide removal in ARDS patients.

PURPOSE: To explore the feasibility of long-term application of ultraprotective ventilation with low flow ECCO2R support in moderate-severe ARDS patients and the reduction of mechanical power (MP) compared to lung protective ventilation. MATERIAL AND METHODS: ARDS patients with PaO2/FiO2 < 200, PEEP of 10 cmH2O, tidal volume 6 ml/Kg of predicted body weight (PBW), plateau pressure > 24 cmH2O, MP > 17 J/min were prospectively enrolled. After 2 h tidal volume was reduced to 4-5 ml/kg, respiratory rate (RR) and PEEP were changed to maintain similar minute ventilation and mean airway pressure (MAP) to those obtained at baseline. After 2 h, ECCO2R support was started, RR was decreased and PEEP was increased to maintain similar PaCO2 and MAP, respectively. RESULTS: The only reduction of tidal volume with the increase in RR did not decrease MP. The application of low flow ECCO2R support allowed a reduction of RR from 25 [24-30] to 11 [9-14] bpm and MP from 18 [13-23] to 8 [7-11] J/min. During the following 5 days no changes in mechanics variables and gas exchange occurred. CONCLUSIONS: The application of low flow ECCO2R support with ultraprotective ventilation was feasible minimizing the MP without deterioration in oxygenation in ARDS patients.

Acid-Base Disorders in COVID-19 Patients with Acute Respiratory Distress Syndrome.

Our aim was to investigate the distribution of acid-base disorders in patients with COVID-19 ARDS using both the Henderson-Hasselbalch and Stewart's approach and to explore if hypoxemia can influence acid-base disorders. COVID-19 ARDS patients, within the first 48 h of the need for a non-invasive respiratory support, were retrospectively enrolled. Respiratory support was provided by helmet continuous positive airway pressure (CPAP) or by non-invasive ventilation. One hundred and four patients were enrolled, 84% treated with CPAP and 16% with non-invasive ventilation. Using the Henderson-Hasselbalch approach, 40% and 32% of patients presented respiratory and metabolic alkalosis, respectively; 13% did not present acid-base disorders. Using Stewart's approach, 43% and 33% had a respiratory and metabolic alkalosis, respectively; 12% of patients had a mixed disorder characterized by normal pH with a lower SID. The severe hypoxemic and moderate hypoxemic group presented similar frequencies of respiratory and metabolic alkalosis. The most frequent acid-base disorders were respiratory and metabolic alkalosis using both the Henderson-Hasselbalch and Stewart's approach. Stewart's approach detected mixed disorders with a normal pH probably generated by the combined effect of strong ions and weak acids. The impairment of oxygenation did not affect acid-base disorders.