Positive end-expiratory pressure ventilation decreases plasma atrial and brain natriuretic peptide levels in humans

Anesthesia and the renal sympathetic nervous system in perioperative AKI

Approximately 7% of patients undergoing non-cardiac surgery with general anesthesia develop postoperative acute kidney injury (AKI). It is well-known that general anesthesia may have an impact on renal function and water balance regulation, but the mechanisms and potential differences between anesthetics are not yet completely clear. Recently published large animal studies have demonstrated that volatile (gas) anesthesia stimulates the renal sympathetic nervous system more than intravenous propofol anesthesia, resulting in decreased water and sodium excretion and reduced renal perfusion and oxygenation. Whether this is the case also in humans remains to be clarified. Increased renal sympathetic nerve activity may impair renal excretory function and oxygenation and induce structural injury in ischemic AKI models and could therefore be a contributing factor to AKI in the perioperative setting. This review summarizes anesthetic agents' effects on the renal sympathetic nervous system that may be important in the pathogenesis of perioperative AKI.

Polyphenols of the Mediterranean Diet and Their Metabolites in the Prevention of Colorectal Cancer

The Mediterranean diet is a central element of a healthy lifestyle, where polyphenols play a key role due to their anti-oxidant properties, and for some of them, as nutripharmacological compounds capable of preventing a number of diseases, including cancer. Due to the high prevalence of intestinal cancer (ranking second in causing morbidity and mortality), this review is focused on the beneficial effects of selected dietary phytophenols, largely present in Mediterranean cooking: apigenin, curcumin, epigallocatechin gallate, quercetin-rutine, and resveratrol. The role of the Mediterranean diet in the prevention of colorectal cancer and future perspectives are discussed in terms of food polyphenol content, the effectiveness, the plasma level, and the importance of other factors, such as the polyphenol metabolites and the influence of the microbiome. Perspectives are discussed in terms of microbiome-dependency of the brain-second brain axis. The emergence of polyphenol formulations may strengthen the efficiency of the Mediterranean diet in the prevention of cancer.

Effect of lipopolysaccharide, cytokines, and catecholamines on brain natriuretic peptide release from human myocardium

BACKGROUND

During sepsis and septic shock, elevated plasma concentrations of brain natriuretic peptide (BNP) have been reported but may be related to several underlying mechanisms. The aim of the present experimental study was to investigate the effect of lipopolysaccharide (LPS), tumor necrosis factor α (TNF-α), interleukin 1β (IL-1β), interleukin 6 (IL-6), dobutamine (Dobu), epinephrine (Epi), and norepinephrine (Nor) on BNP synthesis by atrial human myocardium in vitro.

METHODS

After the approval of local ethics committee, right atrial appendages were obtained during cannulation for cardiac surgery and pinned in a isolated organ bath containing 15 ml of Tyrode's modified solution. Preparations were oxygenated, maintained at 36 ± 0.5°C and stimulated at a frequency of 1 Hz. A 60-min equilibration period was followed by 180-min exposure to 1 μM endothelin 1 (ET-1; n = 9), 20,000 pg/ml TNF-α (n = 10), 1000 pg/ml IL-1β (n = 10), 5000 pg/ml IL-6 (n = 10), 10,000 pg/ml LPS (n = 10), 100 μM Epi (n = 9), 100 μM Nor (n = 10), and 100 μM Dobu (n = 8). No product was added in Control group (n = 10). Two BNP dosages were performed: the first after 60 min of stabilization and the second after 180 min of stimulation. Absolute and relative changes in BNP concentration were compared between groups.

RESULTS

Exposure to ET-1 significantly increased BNP release as compared with Control group. Dobu, Epi, Nor, and LPS significantly increased BNP concentration but not TNF-α, IL-1β, or IL-6.

CONCLUSIONS

In vitro, LPS, Dobu, Epi, and Nor induced BNP synthesis by human atrial myocardium.

A comparison of transcutaneous Doppler corrected flow time, b-type natriuretic peptide and central venous pressure as predictors of fluid responsiveness in septic shock: a preliminary evaluation

Aortic corrected flow time (FTc) is easily measured by Doppler techniques. Recent data using transoesophageal Doppler suggest that it may predict fluid responsiveness in critical care. This use of FTc has not previously been evaluated in septic shock, nor have any studies incorporated transcutaneously measured FTc. Furthermore, no comparison has been made between FTc, plasma B-type natriuretic peptide concentration (BNP) or central venous pressure. The aim of this preliminary study was to compare FTc, BNP and central venous pressure as predictors of fluid responsiveness in septic shock patients without cardiac dysrhythmia. This was a prospective study of 10 consecutive adult septic shock patients (in sinus rhythm; 60% mechanically ventilated) treated with intravenous fluid challenge (4% albumin 250 ml over 15 minutes) in a mixed medical/ surgical tertiary intensive care unit. Mean + SD Acute Physiological and Chronic Health Evaluation II score was 21.8 +/- 12.7. Haemodynamic assessment incorporating transcutaneous aortic Doppler (USCOM) occurred before and five minutes after fluid challenge. Concurrent with initial assessment, blood samples were collected for BNP assay (ADIVA Centaur). Four patients demonstrated an increase in stroke volume > or = 15% (responders). Percent change in stroke volume strongly correlated with baseline FTc (r = -0.81, P = 0.004) but not BNP (r = -0.3, P = 0.4) or central venous pressure (r = -0.4, P = 0.2). Baseline FTc < 350 ms discriminated responders from non-responders (P = 0.047). Our data support FTc as a better predictor of fluid responsiveness than either BNP or central venous pressure in septic shock. Transcutaneous aortic Doppler FTc offers promise as a simple, completely non-invasive predictor of fluid responsiveness and should be evaluated further

Prediction of hospital outcome in septic shock: a prospective comparison of tissue Doppler and cardiac biomarkers

Introduction

Diastolic dysfunction as demonstrated by tissue Doppler imaging (TDI), particularly E/e' (peak early diastolic transmitral/peak early diastolic mitral annular velocity) is common in critical illness. In septic shock, the prognostic value of TDI is undefined. This study sought to evaluate and compare the prognostic significance of TDI and cardiac biomarkers (B-type natriuretic peptide (BNP); N-terminal proBNP (NTproBNP); troponin T (TnT)) in septic shock. The contribution of fluid management and diastolic dysfunction to elevation of BNP was also evaluated.

Methods

Twenty-one consecutive adult patients from a multidisciplinary intensive care unit underwent transthoracic echocardiography and blood collection within 72 hours of developing septic shock.

Results

Mean ± SD APACHE III score was 80.1 ± 23.8. Hospital mortality was 29%. E/e' was significantly higher in hospital non-survivors (15.32 ± 2.74, survivors 9.05 ± 2.75; P = 0.0002). Area under ROC curves were E/e' 0.94, TnT 0.86, BNP 0.78 and NTproBNP 0.67. An E/e' threshold of 14.5 offered 100% sensitivity and 83% specificity. Adjustment for APACHE III, cardiac disease, fluid balance and grade of diastolic function, demonstrated E/e' as an independent predictor of hospital mortality (P = 0.019). Multiple linear regression incorporating APACHE III, gender, cardiac disease, fluid balance, noradrenaline dose, C reactive protein, ejection fraction and diastolic dysfunction yielded APACHE III (P = 0.033), fluid balance (P = 0.001) and diastolic dysfunction (P = 0.009) as independent predictors of BNP concentration.

Conclusions

E/e' is an independent predictor of hospital survival in septic shock. It offers better discrimination between survivors and non-survivors than cardiac biomarkers. Fluid balance and diastolic dysfunction were independent predictors of BNP concentration in septic shock.

High frequency jet ventilation is associated with increased levels of plasma alpha-atrial natriuretic peptide -- a preliminary study

PURPOSE

To determine if high frequency jet ventilation (HFJV) influences the secretion of alpha-atrial natriuretic peptide (alpha- ANP).

METHODS

Sixteen patients undergoing otolaryngeal surgery were studied. Nine patients were subjected to intermittent positive pressure ventilation (IPPV), and seven patients underwent HFJV. Blood samples were drawn for the measurement of plasma alpha-ANP levels and blood gases before anesthesia, and at 30-min after starting either type of ventilation. The study was started at 2:00 p.m., and was completed before surgery. The plasma concentration of alpha-ANP was assayed by radioimmunoassay.

RESULTS

There were no significant differences in mean arterial pressure, heart rate, oxygenation index and PaCO(2) between the two groups. IPPV was not associated with any changes in plasma -ANP levels, whereas HFJV was associated with significantly increased plasma alpha-ANP levels (from 60.0 +/- 5.7 pg x mL(-1) before anesthesia to 112.0 +/- 11.6 pg x mL(-1) after ventilation, P < 0.01). The urine output of the HFJV patients was significantly greater than that of the IPPV patients (P < 0.05).

CONCLUSION

These preliminary results suggest that HFJV is associated with a significant increase in plasma ANP and in urine output in anesthetized patients.

Neurohormonal responses during positive pressure mechanical ventilation

Positive pressure mechanical ventilation is used daily in critical care units to support ventilation and improve oxygenation in critically ill patients. One adverse response to positive pressure mechanical ventilation is a reduction in urinary output and sodium and water retention. This consequence is attributed to complex neurohormonal responses intended to maintain hemodynamic homeostasis. This article reviews the physiologic nature of these responses and research findings related to these responses and provides clinicians with information about the importance of these responses, particularly in patients with underlying cardiac dysfunction.

Enalaprilat decreases plasma endothelin and atrial natriuretic peptide levels and preload in patients with left ventricular dysfunction after cardiac surgery

OBJECTIVE

To study the acute effects of angiotensin-converting enzyme inhibition by intravenous enalaprilat infusion in patients with left ventricular dysfunction after cardiac surgery.

DESIGN

Prospective, consecutive sample, before-after trial.

SETTING

Surgical intensive care unit in a tertiary care university hospital.

PARTICIPANTS

Eight patients with left ventricular dysfunction after cardiac surgery. Patients were defined as having left ventricular dysfunction if the pulmonary capillary wedge pressure persisted above 18 mmHg in spite of conventional vasoactive medication (inotropic or vasodilating and diuretic drugs) and intermittent mandatory ventilation during the first postoperative week.

INTERVENTIONS

Enalaprilat was infused initially at 1 mg/ hour. The rate was doubled every 30 minutes until pulmonary capillary wedge pressure decreased at least 20% or until a maximum total dose of 10 mg was achieved.

MEASUREMENTS AND RESULTS

Central hemodynamics, systemic oxygenation, and hormonal regulation of circulation (plasma renin activity, plasma endothelin, atrial natriuretic peptide, norepinephrine, epinephrine, and vasopressin concentrations, serum angiotensin-converting enzyme activity, and serum levels of aldosterone) were assessed at baseline before enalaprilat infusion, and repeatedly over 2 hours after the infusion. Enalaprilat infusion (median dose, 2.0 mg; infusion time, 48 minutes) caused a significant decrease in pulmonary capillary wedge pressure (p = 0.004), lasting until the end of the 2 hours' follow-up. This coincided with inhibition of serum angiotensin-converting enzyme activity (p < 0.001), an increase in plasma renin activity (p = 0.022), and decreases in plasma endothelin (p = 0.035), atrial natriuretic peptide (p = 0.005), and serum aldosterone (p = 0.001) concentrations. Cardiac output, venous admixture, and oxygen delivery and consumption remained unchanged.

CONCLUSIONS

Adding enalaprilat to conventional therapy makes it possible to unload the left ventricle and to relieve overt neurohormonal activation temporarily while maintaining cardiac function and systemic oxygenation.

Volemic status influences the response of plasma atrial natriuretic factor to positive airway pressure

STUDY OBJECTIVE; To evaluate interactive effects of volemic status and positive end-expiratory pressure (PEEP) on the plasma levels of atrial natriuretic factor (ANF) in assist-controlled mechanical ventilation (MV).

DESIGN

Three successive protocols applied in randomized order to each participant.

SETTING

Clinical investigation laboratory.

PARTICIPANTS

Twenty-one young, healthy adults.

INTERVENTIONS

The three protocols were as follows: (1) MV+PEEP, normovolemia; (2) MV+PEEP, hypervolemia; and (3) spontaneous breathing (SB), hypervolemia. In protocols 1 and 2, a preliminary period of SB lasting 2 h was followed by MV alone (0.5 h), MV+20 cm H2O PEEP (1 h), and a recovery period of SB (1.5 h). Hypervolemia was induced by the continuous i.v. infusion of 3 L of 0.9% NaCl in 5 h (protocols 2 and 3).

MEASUREMENTS AND RESULTS

Heart rate, BP, and the plasma levels of immunoreactive ANF and catecholamines were measured serially. During hypervolemia, ANF significantly decreased when PEEP was added to MV (protocol 2: from 31.1 +/- 2.7 to 20.7 +/- 1.5 fmol/mL; p < 0.01). This did not occur in normovolemia (protocol 1: from 20.0 +/- to 16.7 +/- 1.2 fmol/mL; p = NS). The different effects of MV+PEEP in normovolemia and hypervolemia were not related to differences in circulating catecholamine levels.

CONCLUSIONS

These results demonstrate for the first time (to our knowledge) that volemic status modulates the response of plasma ANF to PEEP in humans. The role of ANF in the water and salt retention induced by MV with PEEP might be limited to hypervolemic conditions.

Perioperative plasma concentrations of endothelin and natriuretic peptides in children undergoing living-related liver transplantation

To investigate the clinical significance of endothelin (ET), natriuretic peptides, and the renin-angiotensin-aldosterone system in pediatric liver transplantation, we measured plasma levels of ET, atrial and brain natriuretic peptides (ANP, BNP), aldosterone, and plasma renin activity in 18 patients (aged 0.5-12 yr; median 1 yr) undergoing living-related liver transplantation due to congenital biliary atresia and severe liver cirrhosis. Before transplantation, the plasma ET level (28.9 +/- 2.5 [mean +/- SEM] pg/mL) was increased compared with that of healthy children (10-18 pg/mL), but decreased during the anhepatic phase (22.5 +/- 1.6 pg/mL). It increased again after reperfusion and remained at high levels in the early postoperative period (postoperative day 3, 27.8 +/- 3.0 pg/mL). Plasma levels of ANP and BNP and aldosterone and plasma renin activity were also high before surgery. Plasma ANP and BNP did not change significantly during surgery. After transplantation, plasma BNP significantly increased, and plasma ANP tended to increase. Plasma aldosterone increased markedly during the anhepatic phase, although plasma renin activity decreased. After transplantation, plasma aldosterone and plasma renin activity both decreased to within normal levels. Mean arterial blood pressure increased gradually after reperfusion and surgery (postoperative day 3, 35.7 +/- 5.2% increase). No substantial differences in these variables occurred between the younger (< or = 1.0 yr, n = 9) and older patients (> 1.0 yr, n = 9). These results suggest that ET production in the cirrhotic liver is augmented and ET, natriuretic peptides, and the renin-angiotensin-aldosterone system all play some role in the circulatory regulation during perioperative periods of pediatric liver transplantation.