Lynn K. Harstad

Effect of enteral feeding with eicosapentaenoic acid, γ-linolenic acid, and antioxidants in patients with acute respiratory distress syndrome

OBJECTIVES Recent studies in animal models of sepsis-induced acute respiratory distress syndrome (ARDS) have shown that a low-carbohydrate, high-fat diet combining the anti-inflammatory and vasodilatory properties of eicosapentaenoic acid (EPA; fish oil), gamma-linolenic acid (GLA; borage oil) (EPA+GLA), and antioxidants improves lung microvascular permeability, oxygenation, and cardiopulmonary function and reduces proinflammatory eicosanoid synthesis and lung inflammation. These findings suggest that enteral nutrition with EPA+GLA and antioxidants may reduce pulmonary inflammation and may improve oxygenation and clinical outcomes in patients with ARDS. DESIGN Prospective, multicentered, double-blind, randomized controlled trial. SETTING Intensive care units of five academic and teaching hospitals in the United States. PATIENTS We enrolled 146 patients with ARDS (as defined by the American-European Consensus Conference) caused by sepsis/pneumonia, trauma, or aspiration injury in the study. INTERVENTIONS Patients meeting entry criteria were randomized and continuously tube-fed either EPA+GLA or an isonitrogenous, isocaloric standard diet at a minimum caloric delivery of 75% of basal energy expenditure x 1.3 for at least 4-7 days. MEASUREMENTS AND MAIN RESULTS Arterial blood gases were measured, and ventilator settings were recorded at baseline and study days 4 and 7 to enable calculation of PaO2/FIO2, a measure of gas exchange. Pulmonary neutrophil recruitment was assessed by measuring the number of neutrophils and the total cell count in bronchoalveolar lavage fluid at the same time points. Clinical outcomes were recorded. Baseline characteristics of 98 evaluable patients revealed that key demographic, physiologic, and ventilatory variables were similar at entry between both groups. Multiple bronchoalveolar lavages revealed significant decreases (approximately 2.5-fold) in the number of total cells and neutrophils per mL of recovered lavage fluid during the study with EPA+GLA compared with patients fed the control diet. Significant improvements in oxygenation (PaO2/FIO2) from baseline to study days 4 and 7 with lower ventilation variables (FIO2, positive end-expiratory pressure, and minute ventilation) occurred in patients fed EPA+GLA compared with controls. Patients fed EPA+GLA required significantly fewer days of ventilatory support (11 vs. 16.3 days; p = .011), and had a decreased length of stay in the intensive care unit (12.8 vs. 17.5 days; p = .016) compared with controls. Only four of 51 (8%) patients fed EPA+GLA vs. 13 of 47 (28%) control patients developed a new organ failure during the study (p = .015). CONCLUSIONS The beneficial effects of the EPA+GLA diet on pulmonary neutrophil recruitment, gas exchange, requirement for mechanical ventilation, length of intensive care unit stay, and the reduction of new organ failures suggest that this enteral nutrition formula would be a useful adjuvant therapy in the clinical management of patients with or at risk of developing ARDS.

Impaired Natriuretic and Renal Endocrine Response to Acute Volume Expansion in Pre-Clinical Systolic and Diastolic Dysfunction

OBJECTIVES We hypothesized an impaired renal endocrine and natriuretic response to volume expansion (VE) in humans with pre-clinical systolic dysfunction (PSD) and pre-clinical diastolic dysfunction (PDD). We further hypothesized that exogenous B-type natriuretic peptide (BNP) could rescue an impaired natriuretic response in PSD and PDD. BACKGROUND Recent reports suggest that in early systolic heart failure (HF), there is an impaired natriuretic response to acute VE. METHODS PSD was defined as left ventricular ejection fraction <40% without HF symptoms. PDD was defined as ejection fraction >50%, moderate to severe diastolic dysfunction by Doppler criteria, and no HF symptoms. A double-blinded, placebo-controlled, crossover study was employed to determine the renal response to VE (0.25 ml/kg/min of normal saline for 60 min) in the presence and absence of exogenous BNP. Twenty healthy control subjects, 20 PSD subjects, and 18 PDD subjects participated. RESULTS In healthy control subjects, urinary cyclic guanosine monophosphate (cGMP) and natriuresis increased after VE. In contrast, among PSD and PDD subjects, there was a paradoxical decrease in urinary cGMP and attenuated natriuresis. Pre-treatment with subcutaneous BNP resulted in similar increases in both urinary cGMP and natriuresis among healthy normal, PSD, and PDD subjects. CONCLUSIONS In PSD and PDD, there is impaired renal cGMP activation, which contributes to impaired natriuresis in response to VE. Impaired activation of urinary cGMP and reduced natriuresis may contribute to volume overload and the progression of HF among PSD and PDD subjects. Importantly, the impaired renal excretory response to VE is rescued by exogenous BNP in PSD and PDD.

Local renal delivery of a natriuretic peptide a renal-enhancing strategy for B-type natriuretic peptide in overt experimental heart failure.

OBJECTIVES The purpose of this study was to test the hypothesis that local renal delivery of B-type natriuretic peptide (BNP) will overcome renal resistance to BNP without systemic hypotension. BACKGROUND BNP has vasodilating, natriuretic, and renin-inhibiting properties. In overt heart failure (HF), there is development of renal resistance to BNP. METHODS We defined the cardiorenal and humoral effects of systemic (n = 6) or local renal (n = 7) administration of canine BNP (0.01 microg/kg/min) in 2 separate groups of dogs with pacing-induced subacute overt HF complicated by renal dysfunction. We used a commercially available small (3.1-F) bifurcated renal catheter (FlowMedica Inc., Fremont, California) for direct bilateral infusion of BNP into both renal arteries. RESULTS With systemic BNP at this clinically used dose (without the bolus), urine flow increased, but there was only a trend for an increase in urinary sodium excretion and glomerular filtration rate (GFR). In contrast, local renal delivery of BNP resulted in significant diuresis and natriuresis and an increase in GFR. These diuretic and natriuretic responses were greater with local renal BNP compared with systemic BNP, and were associated with increased delivery of BNP to the renal tubules as evident by a greater urinary BNP excretion resulting in a decrease in distal reabsorption of sodium. Importantly, local renal BNP did not result in a significant decrease in mean arterial pressure that was observed with systemic BNP. CONCLUSIONS We conclude that local renal BNP delivery is a novel strategy that may overcome renal assistance to BNP in overt HF by increasing local delivery of BNP to the renal tubules.

Chronic subcutaneous brain natriuretic peptide therapy in asymptomatic systolic heart failure.

We have previously reported that asymptomatic systolic heart failure (HF) is characterized by an impaired renal response to volume expansion due to lack of activation of urinary cGMP which is corrected by subcutaneous (SQ) BNP. In the current study, we sought to define the cardiorenal response to intravascular volume expansion after 12 weeks of SQ BNP therapy.

The effects of dose reduction of furosemide on glomerular filtration rate in stable systolic heart failure.

Loop diuretics are effective and necessary to improve hemodynamics and relieve congestion in subjects with systolic heart failure (HF) and fluid overload. In contrast, in compensated/noncongested patients with left ventricular systolic dysfunction, reports suggest negative consequences of chronic