Effects of renal and hepatic venous congestion on renal function in the presence of low and normal cardiac output in dogs

Kidney function changes in acute heart failure: a practical approach to interpretation and management

Worsening kidney function (WKF) is common in patients with acute heart failure (AHF) syndromes. Although WKF has traditionally been associated with worse outcomes on a population level, serum creatinine concentrations vary greatly during episodes of worsening heart failure, with substantial individual heterogeneity in terms of their clinical meaning. Consequently, interpreting such changes within the appropriate clinical context is essential to unravel the pathophysiology of kidney function changes and appropriately interpret their clinical meaning. This article aims to provide a critical overview of WKF in AHF, aiming to provide physicians with some tips and tricks to appropriately interpret kidney function changes in the context of AHF.

Edema formation in congestive heart failure and the underlying mechanisms

Congestive heart failure (HF) is a complex disease state characterized by impaired ventricular function and insufficient peripheral blood supply. The resultant reduced blood flow characterizing HF promotes activation of neurohormonal systems which leads to fluid retention, often exhibited as pulmonary congestion, peripheral edema, dyspnea, and fatigue. Despite intensive research, the exact mechanisms underlying edema formation in HF are poorly characterized. However, the unique relationship between the heart and the kidneys plays a central role in this phenomenon. Specifically, the interplay between the heart and the kidneys in HF involves multiple interdependent mechanisms, including hemodynamic alterations resulting in insufficient peripheral and renal perfusion which can lead to renal tubule hypoxia. Furthermore, HF is characterized by activation of neurohormonal factors including renin-angiotensin-aldosterone system (RAAS), sympathetic nervous system (SNS), endothelin-1 (ET-1), and anti-diuretic hormone (ADH) due to reduced cardiac output (CO) and renal perfusion. Persistent activation of these systems results in deleterious effects on both the kidneys and the heart, including sodium and water retention, vasoconstriction, increased central venous pressure (CVP), which is associated with renal venous hypertension/congestion along with increased intra-abdominal pressure (IAP). The latter was shown to reduce renal blood flow (RBF), leading to a decline in the glomerular filtration rate (GFR). Besides the activation of the above-mentioned vasoconstrictor/anti-natriuretic neurohormonal systems, HF is associated with exceptionally elevated levels of atrial natriuretic peptide (ANP) and brain natriuretic peptide (BNP). However, the supremacy of the deleterious neurohormonal systems over the beneficial natriuretic peptides (NP) in HF is evident by persistent sodium and water retention and cardiac remodeling. Many mechanisms have been suggested to explain this phenomenon which seems to be multifactorial and play a major role in the development of renal hyporesponsiveness to NPs and cardiac remodeling. This review focuses on the mechanisms underlying the development of edema in HF with reduced ejection fraction and refers to the therapeutic maneuvers applied today to overcome abnormal salt/water balance characterizing HF.

Quantification and treatment of congestion in heart failure: A clinical and pathophysiological overview

Renal sodium and water retention with resulting extracellular volume expansion and redistribution are hallmark features of heart failure syndromes. However, congestion assessment, monitoring, and treatment represent a real challenge in daily clinical practice. This document reviewed historical and contemporary evidence of available methods for determining volume status and discuss pharmacological aspects and pathophysiological principles that underlie diuretic use.

Quantification and Treatment of Congestion in Heart Failure: A Clinical and Pathophysiological Overview

Renal sodium and water retention with resulting extracellular volume expansion and redistribution are hallmark features of heart failure syndromes. However, congestion assessment, monitoring, and treatment represent a real challenge in daily clinical practice. This document reviewed historical and contemporary evidence of available methods for determining volume status and discuss pharmacological aspects and pathophysiological principles that underlie diuretic use.

Admission Peripheral Edema, Central Venous Pressure, and Survival in Critically Ill Patients

RATIONALE

The clinical significance of peripheral edema has not been well described in critical illness.

OBJECTIVES

To assess the clinical significance of peripheral edema detected on physical examination at the time of hospital admission for patients who were treated in an intensive care unit (ICU).

METHODS

Using a large inception cohort of critically ill patients, we examined the association of peripheral edema, as documented on hospital admission physical examination, with hospital and 1-year survival.

MEASUREMENTS AND MAIN RESULTS

Of 12,778 patients admitted to an ICU at a teaching hospital in Boston, Massachusetts, 2,338 (18%) had peripheral edema. Adjusting for severity of illness and comorbidities, including pulmonary edema, admission peripheral edema was associated with a 26% (95% confidence interval [CI] = 1.11-1.44, P < 0.001) higher risk of hospital mortality. In those patients whose peripheral edema could be graded, trace, 1+, 2+, and 3+ admission peripheral edema was associated with a 2% (95% CI = 0.80-1.31, P = 0.89), 17% (95% CI = 1.00-1.56, P = 0.05), 60% (95% CI = 1.26-2.04, P < 0.001), and 54% (95% CI = 1.04-2.29, P = 0.03) higher adjusted risk of hospital mortality, respectively, compared with patients without edema. The association was consistent across strata of patients with diabetes, congestive heart failure, sepsis, and premorbid diuretic or calcium channel blocker use. In a subset of patients with central venous pressures measurements obtained within 6 hours of ICU admission, the highest central venous pressure quartile (>13 cm H2O) was similarly associated with a 35% (95% CI = 1.05-1.75, P = 0.02) higher adjusted risk of hospital mortality compared with the lowest quartile (≤7 cm H2O).

CONCLUSIONS

Peripheral edema, as detected on physical examination at the time of hospital admission, is a poor prognostic indicator in critical illness. Whether peripheral edema simply reflects underlying pathophysiology, or has an independent pathogenic role, will require further interventional studies.

Hepatic vein pressure predicts GFR in cirrhotic patients with hemodynamic kidney dysfunction

The role of “nephrocongestion” in hemodynamic renal disease is understudied. Intra‐abdominal hypertension accompanies liver disease and renal disease. Our hypothesis states that in those patients with liver disease, hepatic vein pressure measured during a transjugular intrahepatic portosystemic shunt (TIPS) procedure reflects intra‐abdominal pressure and predicts estimated glomerular filtration rate (eGFR). We gathered data from our clinical database and chart review on a cohort of cirrhotic patients who received TIPS at Montefiore as part of their clinical care between 2004 and 2014. We evaluated association of demographic and measured variables with eGFR in those subjects without end‐stage renal disease (ESRD). Using multivariate regression, we examined the relationship between eGFR and hepatic vein pressure while adjusting for age, proteinuria, and ultrasound evidence for parenchymal kidney disease. The mean age of the subjects was 57 years old. Two thirds of the patients were male, 23% were White, and 20% were Black. A higher percentage of patients with chronic kidney disease (CKD), as determined by lower than 60 mL/min/1.73 m², had proteinuria and ultrasound evidence for parenchymal kidney disease. A multivariate linear regression showed a significant and negative association between hepatic vein pressure and eGFR when adjusting for age, race, and proteinuria. Hepatic vein pressure is negatively and significantly associated with eGFR in those patients with liver failure. This finding has major implications for the way we evaluate hemodynamic renal disease.

Cardiorenal Syndrome in Acute Heart Failure: Revisiting Paradigms

Cardiorenal syndrome has been defined as the simultaneous dysfunction of both the heart and the kidney. Worsening renal function that occurs in patients with acute heart failure has been classified as cardiorenal syndrome type 1. In this setting, worsening renal function is a common finding and is due to complex, multifactorial, and not fully understood processes involving hemodynamic (renal arterial hypoperfusion and renal venous congestion) and nonhemodynamic factors. Traditionally, worsening renal function has been associated with worse outcomes, but recent findings have revealed mixed and heterogeneous results, perhaps suggesting that the same phenotype represents a diversity of pathophysiological and clinical situations. Interpreting the magnitude and chronology of renal changes together with baseline renal function, fluid overload status, and clinical response to therapy might help clinicians to unravel the clinical meaning of renal function changes that occur during an episode of heart failure decompensation. In this article, we critically review the contemporary evidence on the pathophysiology and clinical aspects of worsening renal function in acute heart failure.

Fluid loss, venous congestion, and worsening renal function in acute decompensated heart failure

AIMS

To investigate the relationship between decongestion, central venous pressure, and risk of worsening renal function (WRF) in patients with acute decompensated heart failure (ADHF).

METHODS AND RESULTS

We studied 475 patients with ADHF, of whom 238 underwent right heart catheterization. Right atrial pressure (RAP) was measured at baseline and at 24 h. Net fluid loss was recorded in the first 24 h. WRF was defined as a >0.3 mg/dL increase in serum creatinine above baseline. WRF occurred in 84 catheterized patients (35.3%). There was a weak correlation between baseline RAP and baseline estimated glomerular filtration rate (r = -0.17, P = 0.009). The amount of fluid removed during the first 24 h did not correlate with the magnitude of RAP reduction (r = 0.06, P = 0.35). No association was observed between WRF and baseline RAP [odds ratio (OR) 1.06, 95% confidence interval (CI) 0.80-1.41, P = 0.68 per 6.6 mmHg] or the decrease in RAP (adjusted OR 1.13, 95% CI 0.85-1.49, P = 0.40 per 5.3 mmHg reduction in RAP). In contrast, smaller net fluid loss was strongly associated with increased WRF risk. Compared with the first net fluid loss tertile, the adjusted OR was 1.85 (95% CI 0.90-3.80, P = 0.10) and 2.58 (95% CI 1.27-5.25; P = 0.009) for the second and third tertile, respectively (P for trend <0.0001).

CONCLUSION

Smaller early net fluid loss is associated with increased risk for WRF. RAP is not a reliable surrogate of the magnitude of decongestion and risk of WRF. Future research is necessary to determine if targeting congestion may help prevent WRF.

Congestive renal failure: the pathophysiology and treatment of renal venous hypertension

Longstanding experimental evidence supports the role of renal venous hypertension in causing kidney dysfunction and "congestive renal failure." A focus has been heart failure, in which the cardiorenal syndrome may partly be due to high venous pressure, rather than traditional mechanisms involving low cardiac output. Analogous diseases are intra-abdominal hypertension and renal vein thrombosis. Proposed pathophysiologic mechanisms include reduced transglomerular pressure, elevated renal interstitial pressure, myogenic and neural reflexes, baroreceptor stimulation, activation of sympathetic nervous and renin angiotensin aldosterone systems, and enhanced proinflammatory pathways. Most clinical trials have addressed the underlying condition rather than venous hypertension per se. Interpreting the effects of therapeutic interventions on renal venous congestion are therefore problematic because of such confounders as changes in left ventricular function, cardiac output, and blood pressure. Nevertheless, there is preliminary evidence from small studies of intense medical therapy or extracorporeal ultrafiltration for heart failure that there can be changes to central venous pressure that correlate inversely with renal function, independently from the cardiac index. Larger more rigorous trials are needed to definitively establish under what circumstances conventional pharmacologic or ultrafiltration goals might best be directed toward central venous pressures rather than left ventricular or cardiac output parameters.

Role of the kidney in congestive heart failure

The changes in renal function observed in congestive heart failure include altered pressures and flows and increased reabsorption of sodium and water leading to expanded extracellular fluid volume. These renal effects are mediated by a variety of volume and pressure sensors that stimulate various effectors which act on the kidney. The role of these sensors and effectors, the relationship between left ventricular function (LVF) and urinary sodium excretion (UNaV) and the role of angiotensin II in mediating the renal hemodynamic changes are reviewed. Rats with experimentally induced myocardial infarction (MI) were studied 3 weeks after infarction. Although UNaV decreased as LVF worsened, the decrease in UNaV was evident even in rats with MI and minimal LVF impairment. Infusion of teprotide (an inhibitor of angiotensin I converting enzyme) returned the hemodynamic parameters to or toward values seen in rats without MI, thereby documenting an important role for angiotensin II in congestive heart failure.

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.

Effect of mechanical ventilation on the kidney

Mechanical ventilation is a standard component of intensive care unit management of critically ill patients and is widely used for respiratory support. Recent animal and clinical studies have shown that positive pressure ventilation can worsen pre-existing lung injury and produce ventilator-induced lung injury, which has been linked with the development of systemic inflammation and multi-system organ dysfunction, including renal failure. Although the physiological consequences of mechanical ventilation on pulmonary and cardiovascular function have been extensively studied, its effects on renal function are not as well defined. Previous experimental studies and few clinical reports have shown a significant effect of mechanical ventilation on renal function. Interestingly, recent data are emerging which suggest that renal dysfunction also has a direct, adverse effect on pulmonary function. This chapter reviews the information in these areas and provides a framework for future investigation in this field.

Mechanical ventilation and renal function: an area for concern?

Mechanical ventilation is a standard component of intensive care unit management of critically ill patients and widely used for respiratory support. Patients requiring ventilation often have renal dysfunction that can occur as a consequence of the underlying disease or be related to the therapy. Although the physiological consequences of mechanical ventilation on pulmonary and cardiovascular function have been extensively studied, its effects on renal function are not as well defined. Previous experimental studies and few clinical reports have shown a significant effect of mechanical ventilation on renal function. This review compiles the information in this area and provides a framework for future investigation in this field.

Treatment of edematous disorders with diuretics

Generalized edema results from alterations in renal sodium homeostasis that ultimately result in an expansion of extracellular fluid volume and accumulation of interstitial fluid. The common edematous disorders include congestive heart failure, cirrhosis, nephrotic syndrome, and renal insufficiency. The abnormalities of sodium homeostasis contributing to edema formation in each condition are discussed. Management of volume homeostasis, with an emphasis on the role of diuretic therapy, is reviewed.

Interactions between hemodynamic and hormonal modifications during PEEP-induced antidiuresis and antinatriuresis

The interactions between hemodynamic and hormonal modifications during antidiuresis and antinatriuresis induced by positive end-expiratory pressure (PEEP) were studied in six patients under 15 cm H2O PEEP before PEEP and after the addition of lower body positive pressure (LBPP) to PEEP (PEEP+LBPP). We measured or calculated the following: cardiac index, systemic arterial, right atrial, pulmonary arterial, and pulmonary artery occlusive pressures; indexed renal blood flow (iodohippurate 131 sodium clearance); total blood volume (chromium 51 radiolabeled RBCs); glomerular filtration rate; urinary output; fractional excretion of sodium (FE Na+); plasma concentrations of antidiuretic hormone (ADH), plasma renin activity (PRA), norepinephrine and epinephrine; urinary concentration of PGE2 (PGE2u). Although LBPP application corrected PEEP deleterious effects on systemic and renal hemodynamics, sustained fall in Vu and in FE Na+ were observed. Antidiuresis was not due to ADH release. Sympathetic activation and high PRA appeared the main determinants of renal function alterations in PEEP ventilation.

[Kidney function in heart failure]

Congestive cardiac failure is a syndrome in which a decrease of cardiac output triggers a series of neuro-humoral compensatory mechanisms in part involving the kidney. In this response, dysfunction of atrial volume receptors as well as disturbances of the autonomic nervous system have recently been demonstrated and are held responsible for excessive stimulation of angiotensin II, followed by adverse regulatory effects. Renal hemodynamic compensation for heart failure primarily involves constriction of efferent arterioles thereby defending glomerular filtration. In this setting, the occurrence of prerenal insufficiency is indicative of a far advanced reduction in renal blood flow. Apparent diuretic resistance in the treatment of heart failure is usually caused by iatrogenic vascular compromise or by the use of a single diuretic rather than an appropriate combination. Hyponatremia, vasopressin stimulation and elevation of plasma N-epinephrine concentration have been found to be the most reliable indicators of a poor prognosis of heart failure. Atrial natriuretic peptide is stimulated in proportion to the degree of atrial distension in heart failure, however its intrarenal effects are markedly blunted or may even be absent in this particular disease.

Pathogenesis and treatment of edema

Edema results from excess accumulation of interstitial fluid. This may be due to increased transfer of fluid across the capillary membranes or excess retention of salt and water. The kidneys play a significant role in promoting salt and water homeostasis. Correction of the primary disorder should be the main goal in the management. Diuretics aid in promoting increased excretion of salt and water.

Body fluid homeostasis in congestive heart failure and cirrhosis with ascites

The urinary excretion of salt and water in man is regulated by a variety of renal and extrarenal mechanisms that respond to changes in dietary sodium intake as well as to alterations in the holding capacity of the vascular and interstitial compartments. Changes in extracellular fluid volume are detected by volume sensors located in the intrathoracic vascular bed, the kidney and other organs. These sensing mechanisms gauge the adequacy of intravascular volume relative to capacitance at various sites within the circulation. Congestive heart failure and cirrhosis with ascites are two disease states of man in which a hemodynamic disturbance within a given circulatory subcompartment is perceived by these sensing mechanisms and results in renal sodium retention. While the primary disturbance in both of these conditions originates outside the kidney, a variety of renal effector mechanisms respond to the perceived circulatory disturbance and result in enhanced tubule reabsorption of salt and water. These effector mechanisms involve physical adjustments in renal microvascular hemodynamics, tubule fluid composition and flow rate and transtubular ion gradients. These in turn are partially regulated by a variety of neural and humoral pathways including the renin-angiotensin-aldosterone axis, prostaglandins, and kinins.

[The effect of PEEP ventilation on hemodynamics and regional blood flow (author's transl)]

The beneficial effects of PEEP on lung function may be counteracted by its hemodynamic sequelae induced by a reduction of venous return due to the elevated intrathoracic pressure, and by an increased right ventricular afterload secondary to the rise of pulmonary vascular resistance. PEEP redistributes cardiac output in favor of brain, heart, adrenals and intestines, whereas the perfusion of stomach, pancreas and thyroid is diminished out of proportion to the fall of cardiac output. Total renal blood flow is relatively little affected; however, redistribution of intrarenal blood flow will result in a marked salt-water-retention. Reduction of hepatic artery flow, at higher levels of PEEP, may jeopardize liver tissue oxygenation. - Under clinical conditions, individual differences regarding preexisting cardiopulmonary and peripheral-vascular diseases may modify the PEEP-induced hemodynamic alterations in a wide range.