Mechanical ventilation and renal function: an area for concern?

Acute renal response to changes in carbon dioxide in mechanically ventilated female pigs

Kidney response to acute and mechanically induced variation in ventilation associated with different levels of PEEP has not been investigated. We aimed to quantify the effect of ventilatory settings on renal acid-base compensation. Forty-one pigs undergoing hypo- (<0.2 Lkg-1 min-1, PEEP 25 cmH2O), intermediate (0.2-0.4 Lkg-1 min-1 with either PEEP 5 or 25 cmH2O), or hyper-ventilation (>0.4 Lkg-1 min-1, PEEP 5 cmH2O) for 48 h were retrospectively included. The decrease in pH paralleled the decrease in plasma strong ion difference (SID) in hyper- and intermediately ventilated groups with lower PEEP. In contrast, the plasma SID remained nearly constant in hypo- and intermediately ventilated groups with higher PEEP. Changes in plasma chloride concentration accounted for the changes in plasma SID (conditional R2 = 0.86). The plasma SID changes were paralleled by mirror changes in urinary SID. Higher PEEP (25 cmH2O), compared to lower PEEP (5 cmH2O) dampened or abolished the renal compensation through its effect on hemodynamics (higher central venous and mean pulmonary pressures), irrespective of minute ventilation. During mechanical ventilation, the compensatory renal response to respiratory derangement is immediate and progressive but can be dampened by high PEEP levels.

Causes and management of urinary system problems in children on long-term home invasive mechanical ventilation

Many ventilator-dependent children have comorbid conditions including urinary tract disorders. We aimed to present a focused review of the literature describing the causes and management of urinary system problems in children with long-term home mechanical ventilation. We performed a literature search in PubMed/MEDLINE, Scopus, and Web of Science with keywords "children," "home mechanical ventilation," "urinary system," "urinary tract," "neurogenic bladder," "clean intermittent catheterization," "urinary tract infection," "urolithiasis," and "acute kidney injury." We included original articles, reviews, guidelines, and case reports published in English. Ventilator-dependent children may have neurogenic bladder/bowel dysfunction which renders them prone to urinary tract infection, high bladder pressure, vesicoureteral reflux, hydronephrosis, and renal dysfunction. These children require bladder catheterization, medications affecting parasympathetic/sympathetic nervous systems, or surgical procedures to prevent urinary infections, and to maintain continence and renal functions. However, bladder catheterization or surgical procedures like augmentation cystoplasty may also be complicated with urinary infections, urolithiasis, or urethral strictures. Urolithiasis frequency is also increased due to immobilization-related hypercalciuria, hypocitraturia caused by antiepileptic drugs, urinary stasis, and urinary infections. On the other hand, mechanical ventilation can impair renal function by reduction of cardiac output, redistribution of intrarenal blood flow and stimulation of sympathetic and hormonal pathways. Children requiring long-term invasive home mechanical ventilation may have other comorbid conditions, including urinary system diseases, which become manifest as these patients are being kept alive due to the advances in ventilation strategies. These children must be carefully observed for urological complications and managed accordingly to prevent kidney injury.

Incidence, risk factors and outcomes of acute kidney injury in surgical intensive care unit octogenarians at the Jordan University Hospital

BACKGROUND

Acute kidney damage (AKI) is among the most severe consequences observed in surgical intensive care units (SICUs). We aim to observe the incidence, risk factors, and outcomes of acute kidney injury in SICU octogenarians.

METHODS

A cross-sectional retrospective study was conducted at the SICU of Jordan University Hospital (JUH), a tertiary teaching hospital in a developing country, between January 2018 and December 2019. Patients who were 80 years or older at the time of data collection were included. The definition of AKI was based on Kidney Disease Improving Global Outcomes (KDIGO) criteria. Demographic, clinical, and laboratory data were reviewed.

RESULTS

A total number of 168 patients were included. The mean age was 84.0 ± 3.8 years, and 54.8% of the participants were women. Of those, 115 (68.5%) had surgery before or during ICU stay, and 28.7% of the patients' surgeries were an emergency surgery. Also, 47.8% of surgeries were considered by anesthesia to be high-risk surgeries. A total of 55 patients (32.7%) developed AKI during their SICU stay. The factors that were significantly associated with AKI in the ICU patients included use of beta blocker [AOR: 3.7; 95% CI: 1.2-11.8; p = 0.025], and inotropes [AOR:4.0; 95% CI: 1.2-13.3; p = 0.03]. The factors that were significantly associated with mortality in the ICU included using mechanical ventilation [AOR:18.7; 95% CI: 2.4-141.9; p = 0.005] and inotropes use [AOR: 12.3; 95% CI: 1.2-120.7; p = 0.031].

CONCLUSIONS

The incidence of AKI during SICU stay in this study was 32.7% and it was significantly associated with the use of beta blockers, mechanical ventilation, and inotropes. The mortality rate among octogenarians who developed AKI during SICU stay was 36.4%. Further studies are needed globally to assess the incidence of AKI in octogenarian surgical patients and identify risk factors to provide preventative measurements and strategies.

[Pulmonary-renal crosstalk in the critically ill patient]

Despite advances in the development of renal replacement therapy, mortality of acute renal failure remains high, especially when occurring simultaneously with distant organic failure as it is in the case of the acute respiratory distress syndrome. In this update, birideccional deleterious relationship between lung and kidney on the setting of organ dysfunction is reviewed, which presents important clinical aspects of knowing. Specifically, the renal effects of acute respiratory distress syndrome and the use of positive-pressure mechanical ventilation are discussed, being ventilator induced lung injury one of the most common models for studying the lung-kidney crosstalk. The role of renal failure induced by mechanical ventilation (ventilator-induced kidney injury) in the pathogenesis of acute renal failure is emphasized. We also analyze the impact of the acute renal failure in the lung, recognizing an increase in pulmonary vascular permeability, inflammation, and alteration of sodium and water channels in the alveolar epithelial. This conceptual model can be the basis for the development of new therapeutic strategies to use in patients with multiple organ dysfunction syndrome.

Pulmonary and renal protection: targeting PARP to ventilator-induced lung and kidney injury?

Both acute lung injury and acute kidney injury (AKI) are frequent and serious problems in intensive care medicine. Therefore, the avoiding of any iatrogenic insult to these organs is of great importance. While an increasing body of evidence suggests that mechanical ventilation is capable of inducing lung and distant organ injury, the complex underlying molecular mechanisms remain insufficiently understood. In the previous issue of Critical Care, Vaschetto and colleagues reported the results of an experimental study designed to further explore pathways linking injurious ventilation with AKI. The authors demonstrated that scavenging of peroxynitrite or inhibiting poly(ADP-ribose) polymerase (PARP) afforded protection against AKI induced by double-hit lung injury. Although PARP inhibition or peroxynitrite detoxification or both may become viable candidates for a protective strategy in this setting, the implementation of a lung-protective ventilatory strategy remains the only clinical tool to mitigate the lung biotrauma and its systemic consequences.

Mechanical ventilation and the kidney

Acute lung injury (ALI) and acute kidney injury (AKI) are complications often encountered in the setting of critical illness. Both forms of end-organ injury commonly occur in similar settings of systemic inflammatory response syndrome, shock, and evolving multiple organ dysfunction. Recent elucidation of the pathobiology of critical illness has led to a more basic mechanistic understanding of the complex interplay between injured organs in patients with multiple organ dysfunction syndrome; this has been aptly called 'the slippery slope of critical illness' [Kidney Int Suppl 1998;66:S25-S33]. Distant organ effects of apparently isolated injuries to the lungs, gut, and kidneys have all been discovered in recent years. In this article, we will review the harmful bidirectional interaction between ALI and AKI, which appears to be a common clinical syndrome with routine clinical implications. We will review the current understanding of lung-kidney interactions from both perspectives, including the renal effects of ALI and mechanical ventilation, and the pulmonary sequelae of AKI. In this review of the emerging evidence of deleterious bidirectional organ cross talk between lung and kidney, we will focus on the role of ventilator-induced kidney injury in the pathogenesis of AKI in patients with ALI.

Mechanical ventilation and acute renal failure

OBJECTIVE

To review the current literature on possible mechanisms by which mechanical ventilation may initiate or aggravate acute renal failure.

DATA SOURCE

A Medline database and references from identified articles were used to perform a literature search relating to mechanical ventilation and acute renal failure.

DATA SYNTHESIS

Acute renal failure may be initiated or aggravated by mechanical ventilation through three different mechanisms. First, strategies such as permissive hypercapnia or permissive hypoxemia may compromise renal blood flow. Second, through effects on cardiac output, mechanical ventilation affects systemic and renal hemodynamics. Third, mechanical ventilation may cause biotrauma-a pulmonary inflammatory reaction that may generate systemic release of inflammatory mediators. The harmful effects of mechanical ventilation may become more significant when a comorbidity is present. In these situations, it is more difficult to maintain normal gas exchange, and moderate arterial hypoxemia and hypercapnia are often accepted. Renal blood flow is compromised due to a decreased cardiac output as a consequence of high intrathoracic pressures. Furthermore, the effects of biotrauma are not limited to the lungs but may lead to a systemic inflammatory reaction.

CONCLUSIONS

The development of acute renal failure during mechanical ventilation likely represents a multifactorial process that may become more important in the presence of comorbidities. Development of optimal interventional strategies requires an understanding of physiologic principles and greater insight into the precise molecular and cellular mechanisms that may also play a role.

Acute renal failure needing dialysis in the intensive care unit and prognostic scores

BACKGROUND

Generic prognostic scores used in acute renal failure (ARF) give imprecise results; disease-specific indices applied to distinct populations or intensive care practices becomes inaccurate. The current study evaluates the adequacy of prognostic scores, in patients with severe ARF needing dialysis.

METHODS

Known generic (APACHE II) and disease-specific (ATN-ISS) indices were applied to a cohort (n = 280) with ARF needing dialysis, under intensive care. Possible risk factors as causal factors, organ dysfunctions and clinical variables were examined, and a local index assembled by multivariate logistic regression analysis. Area under the receiver operating characteristics (ROC) curves evaluated the indices discriminating capacity. Goodness-of-fit testing and linear regression analysis appraised calibration. Validation was accomplished by the bootstrapping technique. The end-point was hospital mortality.

RESULTS

Overall mortality was 85%. Female gender < 44 years (OR: 0.29; 95% CI: 0.10-0.84), liver/obstructive biliary disease (OR: 6.03; 95% CI: 1.65-22.08), being conscious (OR: 0.49; 95% CI: 0.21-1.14), use of vasoactive drug (OR: 3.13; 95% CI: 1.25-7.83), respiratory dysfunction (OR: 5.20; 95% CI: 1.25-7.83) or sepsis (OR: 2.62; 95% CI: 1.14-6.02) were associated with outcome. Areas under the ROC curve of 0.815, 0.652 and 0.814; Goodness-of-fit test P = 0.593, P < 0.001 and P = 0.002; and linear regression R2 = 0.973, R2 = 0.526 and R2 = 0.919 for the local index, APACHE II and ATN-ISS, respectively, indicate better performance by the local index. The local index median area under the ROC curve, by bootstrapping, was 0.820 (95% CI: 0.741-0.907).

CONCLUSIONS

APACHE II score was inaccurate, and ATN-ISS poorly calibrated. When mortality or intensive care practices significantly deviate, local scores may better evaluate prognosis in severe ARF.

Positive end-expiratory pressure in acute respiratory distress syndrome - an old yet mysterious tool

A recent study by Bruhn and colleagues, discussed here, confirms that even high levels of positive end-expiratory pressure (PEEP) – up to 20 cmH₂O – may be applied in conditions of moderate acute respiratory distress syndrome. Such levels of PEEP were found to be safe in terms of their impact on cardiac output and adequacy of gastric mucosal perfusion once systemic haemodynamics were stabilized by adequate fluid replacement and catecholamine therapy. However, we strongly recommend that the reader does not oversimplify the conclusions of that study. PEEP therapy is not inherently safe with respect to haemodynamics and regional organ perfusion, but it may be used safely, even at high levels of up to 20 cmH₂O, if haemodynamic therapy is appropriate.

Outcome and predictive factors of acute renal failure in the intensive care unit

The development of acute renal failure (ARF) in the ICU setting carries a high morbidity and mortality. To assess the outcomes and its predictive factors in our ICU, we analyzed the data of patients with ARF treated during 18 months. The 33 patients included 21 men and 12 women of mean age 51 +/- 21.7 years (13 to 87). Sepsis with multi-organ dysfunction (MOD) was the leading cause of ARF (58%). Comorbid conditions were malignancy in 30% of patients, diabetes mellitus in 24%, hypertension in 21%, ischemic heart disease in 21%, liver disease in 15%, and chronic renal failure in 15%. Predisposing factors were hypotension in 67% of cases, dehydration in 36%, drug related in 33%, congestive heart failure in 24%, and liver cirrhosis in 6%. Twenty-five (76%) patients needed mechanical ventilation, 22 (67%) were anuric, 18 (55%) had MODS, and 15 (45%) needed inotropic support. Length of stay in hospital was 27.2 +/- 28.0 days (2 to 94). Nineteen patients (58%) were managed conservatively and 14 (42%) by renal replacement therapy. Patient mortality was 67% and renal mortality 52%. The impact of the following factor: was assessed on patient and renal outcome was assessed ventilation support, presence of oliguria, need for inotropes, and presence of MOD. Patient mortality was significantly influenced by an elevated odds ratios (OR) (95% CI): mechanical ventilation [OR = 34 (95% CI 1.95 to 538)], and presence of MODS [OR = 12.3 (95% CI 2 to 75)]. Renal mortality was influenced by mechanical ventilation [OR = 12.3 (95% CI 1.6 to 119)], oliguria [OR = 12 (95% CI 2 to 72)], inotrope support [OR = 10 (95% CI 2 to 52), and MOD [OR = 35 (95% CI 3.5 to 35.0)]. This study confirms the high patient and renal mortality of ARF among patients to ICU. The four parameters were excellent predictors of renal outcome, while only the need for mechanical ventilation and the presence of MOD were predictors for patient survival.

Acute renal failure in patients with sepsis in a surgical ICU: predictive factors, incidence, comorbidity, and outcome

Acute renal failure (ARF) is a common complication in intensive care unit (ICU) patients. Although there are several reports on outcome of septic patients with ARF, there are no data regarding predisposing factors for ARF. Therefore, the incidence of ARF was investigated in 185 sepsis patients admitted in a surgical ICU during a 16-mo period. Variables predisposing to ARF on day 1 of sepsis were evaluated with univariate and multivariable analyses. APACHE II and SOFA scores were compared during a 14-d period. Additionally, the impact of organ failure on mortality was evaluated. ARF developed in 16.2% of the patients, and 70.0% of these needed renal replacement therapy (RRT). Patients with ARF were more severely ill and had a higher mortality. Remarkably, serum creatinine was already increased on day 1. Creatinine > 1 mg/dl and pH < 7.30, both on day 1 of sepsis, were independently associated with ARF. Age, need for vasoactive therapy, mechanical ventilation, and RRT, but not ARF itself, were associated with mortality. In conclusion, ARF was a frequent complication in sepsis. Sepsis patients with ARF were more severely ill and had a higher mortality. Need for RRT was independently associated with mortality. A simple risk model for ARF, on basis of two readily available parameters on day 1 of sepsis, was developed. This model allows initiating specific therapeutic measures earlier in the course of sepsis, hopefully resulting in a lower incidence of ARF and needi for RRT, thereby lowering mortality.