Influence of hypothermic cardiopulmonary bypass on atrial natriuretic factor levels

Cardiac Biomarkers of Low Cardiac Output Syndrome in the Postoperative Period After Congenital Heart Disease Surgery in Children

INTRODUCTION AND OBJECTIVES

To assess the predictive value of atrial natriuretic peptide, β-type natriuretic peptide, copeptin, mid-regional pro-adrenomedullin (MR-proADM) and cardiac troponin I (cTn-I) as indicators of low cardiac output syndrome in children with congenital heart disease undergoing cardiopulmonary bypass (CPB).

METHODS

After corrective surgery for congenital heart disease under CPB, 117 children (aged 10 days to 180 months) were enrolled in a prospective observational pilot study during a 2-year period. The patients were classified according to whether they developed low cardiac output syndrome. Biomarker levels were measured at 2, 12, 24, and 48 hours post-CPB. The clinical data and outcome variables were analyzed by a multiple logistic regression model.

RESULTS

Thirty-three (29%) patients developed low cardiac output syndrome (group 1) and the remaining 84 (71%) patients were included in group 2. cTn-I levels >14 ng/mL at 2hours after CPB (OR, 4.05; 95%CI, 1.29-12.64; P=.016) and MR-proADM levels>1.5 nmol/L at 24hours following CPB (OR, 15.54; 95%CI, 4.41-54.71; P<.001) were independent predictors of low cardiac output syndrome.

CONCLUSIONS

Our results suggest that cTn-I at 2hours post-CPB is, by itself, an evident independent early predictor of low cardiac output syndrome. This predictive capacity is, moreover, reinforced when cTn-I is combined with MR-proADM levels at 24hours following CPB. These 2 cardiac biomarkers would aid in therapeutic decision-making in clinical practice and would also enable clinicians to modify the type of support to be used in the pediatric intensive care unit.

Atrial natriuretic factor in normothermic and hypothermic cardiopulmonary bypass

Background: To evaluate the plasmatic changes of atrial natriuretic factor (ANF) during and after cardiopulmonary bypass (CPB) in normothermia and hypothermia.

Methods: Twenty-three patients (n=23) undergoing coronary artery bypass graft surgery were randomly assigned to two groups. In Group I (n=11), the patients underwent operation in normothermia; in Group II (n=12), the operation was performed in hypothermia (268C).

Results: Plasma ANF levels were determined after induction of anaesthesia, at the end of CPB and one hour postoperatively. There were no demographic differences between the two groups, diuresis (p=0.90) and natriuresis (p=0.95). Plasma levels of ANF were significantly elevated during and after CPB in both groups (p <0.01). The groups differed significantly for plasma levels of ANF during CPB and postoperatively ( p<0.05), but did not differ prebypass (p=0.08). There was no correlation in either group between ANF release and central venous pressure, natriuresis and diuresis. There was only a borderline relationship between ANF concentration and diuresis after CPB in Group I.

Conclusion: CPB triggers the production and release of ANF. The present study demonstrates a significantly enhanced ANF release during hypothermia and reperfusion after ischaemia. Thus, these data suggest the protective role of ANF on the hypoxic myocardium, and they confirm that ANF does not play a role in diuresis and natriuresis during and after hypothermic CPB.

A review of the natriuretic hormone system's diagnostic and therapeutic potential in critically ill children

OBJECTIVE

To review the natriuretic hormone system and discuss its diagnostic, prognostic, and therapeutic potential in critically ill children.

DATA SOURCE

A thorough literature search of MEDLINE was performed using search terms including heart defects, congenital; cardiopulmonary bypass, atrial natriuretic factor; natriuretic peptide, brain; carperitide; nesiritide. Preclinical and clinical investigations and review articles were identified that describe the current understanding of the natriuretic hormone system and its role in the regulation of vascular tone and fluid balance in healthy adults and children and in those with underlying cardiac, pulmonary, and renal disease.

RESULTS

A predictable activation of the natriuretic hormone system occurs in children with congenital heart disease and congestive heart failure. Further study is needed to confirm preliminary reports that measurement of natriuretic hormone levels in critically ill children provides diagnostic and prognostic information, as has been demonstrated in adult cardiac populations. Natriuretic hormone infusions provide favorable hemodynamic changes and symptomatic relief when used in adults with decompensated congestive heart failure, and uncontrolled case series suggest that similar benefits may exist in children. The biological activity of the natriuretic hormone system may be decreased following pediatric cardiopulmonary bypass, and additional studies are needed to determine whether natriuretic hormone infusions provide clinical benefit in the postoperative period. Preliminary reports suggest that natriuretic hormone infusions cause physiologic improvements in adults with acute lung injury and asthma but not in those with acute renal failure.

CONCLUSIONS

Although important perturbations of the natriuretic hormone system occur in critically ill infants and children, further investigation is needed before the measurement of natriuretic peptides and the use of natriuretic hormone infusions are incorporated into routine practice.

Effect of cardiopulmonary bypass and surgical intervention on the natriuretic hormone system in children

OBJECTIVES

We sought to determine the effect of cardiopulmonary bypass and surgical intervention on the natriuretic hormone system in children and to assess whether such changes are associated with morbidity.

METHODS

At 6 perioperative time points in 25 patients, plasma levels of atrial natriuretic peptide, brain natriuretic peptide, and guanosine 3', 5'-monophosphate were measured, and the biologic activity of the natriuretic hormone system was quantified. Relationships were sought between changes in brain natriuretic peptide levels, biologic activity, and a number of morbidity indicators.

RESULTS

There was a significant change in atrial natriuretic peptide levels (P = .037), brain natriuretic peptide levels (P = .001), and biologic activity of the natriuretic hormone system (P = .009) over the first 4 time points in the study. Atrial natriuretic peptide levels transiently decreased from baseline to 12 hours after surgical intervention. Compared with baseline values, brain natriuretic peptide levels were increased at 12 hours after surgical intervention and on postoperative day 1. The increase in brain natriuretic peptide levels from baseline to 12 hours after surgical intervention was associated with cardiopulmonary bypass time (r(s) = 0.4, P = .047). The biologic activity transiently decreased from baseline to intensive care unit admission but was not associated with any morbidity indicators.

CONCLUSIONS

Increased postoperative brain natriuretic peptide levels are associated with longer bypass times. The biologic activity of the natriuretic hormone system is transiently impaired. Larger studies should investigate brain natriuretic peptide as a predictor of postoperative morbidity and the potential for natriuretic hormone infusions to improve postoperative hemodynamics and urine output.

Utility of B-type natriuretic peptide for the evaluation of intensive care unit shock*

OBJECTIVES

Among patients with congestive heart failure, B-type natriuretic peptide measurement is useful to estimate filling pressures and to prognosticate adverse outcome. However, among critically ill intensive care unit patients with shock, the utility of B-type natriuretic peptide to assess cardiac hemodynamics or prognosis has not been explored.

DESIGN

Clinical investigation.

SETTING

Hospital.

PATIENTS

Forty-nine patients with shock and indication for pulmonary artery catheterization.

INTERVENTIONS

Analysis for B-type natriuretic peptide was performed on blood obtained at the time of catheter placement.

MEASUREMENTS AND MAIN RESULTS

Correlations between B-type natriuretic peptide and pulmonary artery occlusion pressure as well as cardiac index were calculated using Spearman analysis. Mortality at the time of study completion was correlated with B-type natriuretic peptide values and Acute Physiology and Chronic Health Evaluation II scores, and logistic regression identified independent predictors of mortality. A wide range of B-type natriuretic peptide concentrations was seen in intensive care unit patients (<5 to >5000 pg/mL); only eight patients (16%) had normal B-type natriuretic peptide concentrations. Log-transformed B-type natriuretic peptide concentrations did not correlate with interpatient cardiac index or pulmonary artery occlusion pressure (all p = not significant); however, a B-type natriuretic peptide <350 pg/mL had a negative predictive value of 95% for the diagnosis of cardiogenic shock. Median B-type natriuretic peptide concentrations were higher in those who died than those who survived (943 pg/mL vs. 378 pg/mL, p <.001). In multivariable analysis, a B-type natriuretic peptide concentration in the highest log-quartile was the strongest predictor of mortality (odds ratio = 4.50, 95% confidence interval = 1.87-99.0, p <.001).

CONCLUSION

B-type natriuretic peptide concentrations are frequently elevated among critically ill patients in the intensive care unit and cannot be used as a surrogate for pulmonary artery catheterization. B-type natriuretic peptide concentrations in intensive care unit shock may provide powerful information for use in mortality prediction.

Alterations in the natriuretic hormone system related to cardiopulmonary bypass in infants with congestive heart failure

This study examined changes in the natriuretic hormone system in five infants with congestive heart failure (CHF) due to intracardiac left-to-right shunting who were exposed to cardiopulmonary bypass (CPB) during surgical repair. Plasma concentrations of three hormones [atrial natriuretic peptide (ANP), brain natriuretic peptide (BNP), and dendroaspis natriuretic peptide (DNP)] and their secondary messenger, guanosine 3',5'-monophosphate (cGMP), were measured, and the biological activity of the system was quantified. At baseline, BNP and DNP concentrations were normal in our patients, a finding that is strikingly different from that of adult CHF patients, whereas ANP concentrations were elevated. Following CPB, ANP concentrations decreased (median, 175 vs 44 pg/ml; p = 0.043) and BNP concentrations increased (median, 25 vs 66 pg/ ml; p = 0.043), whereas DNP concentrations did not change. Following modified ultrafiltration, BNP concentrations increased (p = 0.043), but other natriuretic peptide concentrations did not change. The calculated biological activity of the natriuretic hormone system decreased following CPB [molar ratio, cGMP / (ANP + BNP + DNP); median, 213 vs 127; p = 0.043)]. Additional studies are needed to expand on these findings and identify patients with other types of congenital heart disease who have perioperative disturbances in the natriuretic hormone system and thus might benefit from pharmacologic intervention.

Changes in calcitonin gene-related peptide, atrial natriuretic peptide and brain natriuretic peptide in patients undergoing coronary artery bypass grafting

The initiation of cardiopulmonary bypass creates significant derangements in cardiovascular volume status and both endocrine and autonomic nervous system function. To examine whether such derangements might differ in patients with different pre-operative physical status scores, we measured the plasma concentrations of calcitonin gene-related peptide, atrial natriuretic peptide and brain natriuretic peptide, catecholamines and antidiuretic hormone, as well as haemodynamic variables, during and after cardiopulmonary bypass in 27 consecutive patients undergoing coronary artery bypass grafting. The pre-operative levels of atrial natriuretic peptide and brain natriuretic peptide differed significantly between ASA II patients and III and IV patients [mean (SD) brain natriuretic peptide levels = 14 (8.2) vs. 129 (51) pg.ml-1]. Plasma calcitonin gene-related peptide increased significantly in both groups after the initiation of cardiopulmonary bypass, and remained increased throughout cardiopulmonary bypass. The changes in plasma epinephrine, norepinephrine and antidiuretic hormone were similar to those reported previously. The changes in plasma calcitonin gene-related peptide, atrial natriuretic peptide and brain natriuretic peptide did not correlate with any changes in haemodynamic variables before or after cardiopulmonary bypass. Measurement of plasma brain natriuretic peptide might usefully be included in the pre-operative evaluation of patients with cardiac disease.

Effects of intraoperative administration of atrial natriuretic peptide

BACKGROUND

Biological activity of endogenous atrial natriuretic peptide (ANP) may decrease during cardiopulmonary bypass. To evaluate the effects of intraoperative administration of exogenous ANP in patients undergoing cardiopulmonary bypass, we conducted a prospective randomized study.

METHODS

Eighteen patients undergoing mitral valve surgery were randomized to receive either ANP treatment (ANP group; n = 9) or no ANP treatment (control group; n = 9). Atrial natriuretic peptide was given immediately after initiation of cardiopulmonary bypass for 6 hours (0.05 microg x kg(-1) x min(-1)). Plasma ANP, brain natriuretic peptide and cyclic guanosine monophosphate (cGMP) levels, hemodynamic variables and renal function were assessed perioperatively.

RESULTS

Administration of ANP increased plasma cyclic guanosine monophosphate levels, urine output and fractional sodium excretion, and decreased preload, afterload and plasma brain natriuretic peptide levels significantly (p < 0.05). Plasma cyclic guanosine monophosphate levels correlated with plasma ANP levels (r = 0.95, p = 0.0001), correlated with fractional sodium excretion (r = 0.53, p = 0.02), and correlated inversely with systemic vascular resistance (r = -0.54, p = 0.02).

CONCLUSIONS

Intraoperative administration of ANP had potent effects on natriuresis and systemic vasodilation by elevating cyclic guanosine monophosphate levels. The results suggest that the technique is useful for the management of hemodynamics and water-sodium retention after cardiopulmonary bypass.

Biological activity of endogenous atrial natriuretic peptide during cardiopulmonary bypass

To evaluate the effect of cardiopulmonary bypass (CPB) on atrial natriuretic peptide (ANP) biological activity in patients undergoing cardiac operations, we conducted a prospective study. Ten patients undergoing mitral valve surgery were enrolled. Plasma levels of ANP and cyclic guanosine monophosphate (cGMP), hemodynamic variables, and renal function parameters were assessed perioperatively. The molar ratio of cGMP to ANP (as a marker for ANP biological activity) decreased significantly (p < 0.05) during CPB despite similar plasma ANP levels. The ratio correlated inversely with the duration of CPB (r = -0.85, p = 0.002). The ratio also correlated with fractional sodium excretion (r = 0.65, p = 0.04) and correlated inversely with pulmonary vascular resistance (r = -0.79, p = 0.009) and atrial filling pressure (r = -0.84, p= 0.003) postoperatively. CPB decreased the molar ratio of cGMP to ANP, which may represent ANP biological activity, such as vasodilation and natriuresis. The phenomenon may contribute to water-sodium retention and pulmonary hypertension after cardiac surgery.

Perioperative changes in plasma brain natriuretic peptide concentrations in patients undergoing cardiac surgery

The plasma concentrations of brain natriuretic peptide (BNP), a cardiac hormone, were measured in 30 consecutive adult patients undergoing cardiac surgery with cardiopulmonary bypass (CPB) during the perioperative period. BNP concentrations remained unchanged until 6 h after the cessation of bypass, and were elevated 12, 24, and 48 h post-bypass (P < 0.0001 versus baseline). They had returned to the baseline values when measured 3 weeks postoperatively. The preoperative plasma BNP concentration correlated significantly with the left ventricular ejection fraction (r = -0.895). The peak plasma BNP concentration 24 h after bypass correlated with the cardiac index (r = -0.64), stroke volume index (r = -0.62), injection rate of dopamine hydrochloride (r = 0.65), and aortic crossclamp time (r = 0.57). There was also a significant correlation between the preoperative BNP concentration and the plasma BNP concentration 24 h post-CPB. These findings led us to conclude that the plasma concentrations of BNP become markedly and acutely elevated after cardiac surgery with CPB, and reflect the state of left ventricular function. Moreover, the severity of acute heart failure after cardiac surgery can be predicted by the preoperative plasma BNP concentration.

Atrial natriuretic peptide and N-terminal atrial natriuretic peptide in plasma reflect right ventricular volumes following coronary artery surgery

BACKGROUND

Atrial natriuretic peptide (ANP) and the more stable N-terminal fragment (N-ANP) of prohormone are peptides, released in equimolar amounts from cardiac myocytes in response to atrial stretch or ventricular overload and myocardial ischaemia. Protection of the right ventricular (RV) myocardium during ischaemia in cardiac surgery is difficult, especially in patients with severe right coronary artery (RCA) disease. This prospective study was designed to ascertain a possible relationship between changes in plasma ANP/N-ANP concentration and RV function in RCA-diseased patients.

METHODS

Plasma ANP and N-ANP concentrations and RV function, measured by fast-response thermodilution, were determined serially in 15 patients with total RCA stenosis and in another 15 with no significant RCA disease (controls) before, during and after coronary surgery.

RESULTS

The RV ejection fraction was lower and the RV end-systolic volume index higher in the RCA-diseased patients than in the controls (P < 0.05) on the second postoperative day, and both ANP and N-ANP were higher in the RCA patients (P < 0.05) from 6 h after cardiopulmonary bypass till the second postoperative day. At the same time the changes in N-ANP concentrations from the levels before induction of anaesthesia correlated with RV ejection fraction and RV volume indexes, but not with heart rate or parameters indirectly reflecting left-sided loading. Right atrial pressure did not differ between the groups nor did it increase significantly during the study.

CONCLUSIONS

The relationships found between N-ANP and RV volume indexes and RV ejection fraction suggest ventricular expression of ANP: ANP release may be stimulated by RV distension, the more so the poorer the RV function.

Influence of intravenous administration of angiotensin-converting enzyme inhibitor enalaprilat on cardiovascular mediators in cardiac surgery patients

The renin-angiotensin system (RAS) is important in controlling and maintaining cardiovascular homeostasis. In a randomized, prospective study, the response to intravenous (i.v.) administration of the angiotensin-converting enzyme (ACE) inhibitor enalaprilat (0.06 mg/kg) on important controllers of the circulation was investigated in 14 patients undergoing aortocoronary bypass grafting with a mean arterial blood pressure (MAP) > 85 mm Hg after induction of anesthesia. Fourteen patients received saline solution as placebo (control group). Endothelin (ET), atrial natriuretic peptide (ANP), catecholamine (epinephrine, norepinephrine) plasma levels, and ACE activity were measured from arterial blood sampled before injection of enalaprilat or NaCl solution (baseline values), 10 min and 30 min thereafter, immediately before the start of cardiopulmonary bypass (CPB), immediately after CPB, and at the end of surgery. MAP, heart rate (HR), cardiac index (CI), and systemic vascular resistance (SVR) were also monitored. ACE activity was similar at baseline in both groups; after i.v. injection of enalaprilat, it significantly decreased (from 35.1 +/- 11 to 4.4 +/- 1.0 U.min-1.L-1 30 min after injection) and remained reduced until the end of the operation (295 +/- 31 min after injection). ANP plasma levels were increased beyond normal (> 100 pg/mL) at baseline in both groups. They increased significantly in the control patients, but remained almost unchanged in the enalaprilat-treated patients within the entire study period. Plasma concentration of ET also increased only in the control group and was increased after CPB (8.6 +/- 1.2 pg/mL at the end of the operation).(ABSTRACT TRUNCATED AT 250 WORDS)

RETRACTED: Volume loading with hypertonic saline solution: endocrinologic and circulatory responses

Hypertonic saline solution appears to be an attractive method of volume expansion. In 45 patients undergoing elective aorto-coronary bypass grafting, endocrinologic and circulatory responses to volume loading with hypertonic saline solution prepared in low molecular weight (MW) hydroxyethyl starch (HES) solution (72 g/L NaCl, HES concentration: 6%; MW: 200,000 D; degree of substitution [DS]: 0.5) (HS-HES) was compared randomly to patients who had received low molecular weight HES solution (LMW-HES). A group of patients without volume loading served as a control. Volume was infused to double the low pulmonary capillary wedge pressure (PCWP < 5 mmHg) after induction of anesthesia. Plasma levels of atrial natriuretic peptide (ANP), endothelin, vasopressin, and catecholamines were measured before, during, and after cardiopulmonary bypass (CPB) until the first postoperative day. In addition to systemic circulatory changes, capillary skin blood flow was measured by laser Doppler flowmetry. ANP plasma concentration increased in both volume groups (HS-HES: +79%; HES: +32%), whereas it decreased in the control (-20%). Infusion of HS-HES resulted in an increase in plasma endothelin concentration before and after CPB (from 3 to 6 pg/mL). Five hours after CPB, both treatment groups had higher endothelin plasma concentrations than the control patients (P < 0.05). Epinephrine and norepinephrine plasma levels increased most markedly in the control patients and were highest in the postbypass period in these patients. CI increased most after infusion of HS-HES (+65%) (P < 0.05). In the postbypass period, CI remained significantly higher in both volume groups than in the controls.(ABSTRACT TRUNCATED AT 250 WORDS)

Changes in plasma atrial natriuretic peptide concentration during heart transplantation

Examination of changes in plasma atrial natriuretic peptide (ANP) concentrations during heart transplantation may provide important information about factors influencing plasma ANP in patients with severe heart failure. Serial changes in plasma ANP during heart transplantation, and atrial content of ANP in native and donor atria, were measured in 12 patients. Preoperative plasma ANP was elevated in all patients (387 +/- 77 pg/mL), whereas atrial content of ANP in native atria was reduced (0.36 +/- 0.082 micrograms/mg protein). Preoperative plasma ANP did not correlate with hemodynamics, but was negatively correlated with creatinine clearance (r = -0.76, P < .01). Intraoperative plasma ANP prior to transplantation was strongly correlated with intraoperative plasma ANP after transplantation (r = 0.84, P < .001). Although postoperative plasma ANP was reduced from preoperative plasma ANP by 75%, these two measurements were also significantly correlated (r = 0.70, P < .02). Postoperative plasma ANP was not correlated with hemodynamics, but was negatively correlated with both creatinine clearance (r = -0.65, P < .05) and content of ANP in the native atria (r = -0.75, P < .01). Multiple linear regression analysis suggested that up to 85% of the variability of early postoperative plasma ANP could be accounted for by the variability in these latter two parameters. The decrease in native atrial ANP content, in the context of elevated plasma ANP concentration, is consistent with prior animal studies suggesting that severe heart failure induces cellular adaptations favoring accelerated ANP synthesis and secretion (with resultant reduction in tissue content).(ABSTRACT TRUNCATED AT 250 WORDS)

Release of vasoactive substances during cardiopulmonary bypass

Cardiopulmonary bypass is associated with bleeding and thrombotic complications, massive fluid shifts, and cellular and hormonal defense reactions that are collectively termed "the whole body inflammatory response." A host of vasoactive substances are produced, released or altered during cardiopulmonary bypass. These hormones, autacoids, and cytokines react with specific receptor proteins distributed throughout the body, and mediate the vascular smooth muscle and endothelial cell contractions that are responsible for much of the morbidity associated with open heart operations. This essay briefly reviews the actions, sources, and perturbations of the approximately 25 vasoactive substances known or believed to be altered by cardiopulmonary bypass, and provides an introductory reference list.

Pulmonary extraction and left atrial secretion of atrial natriuretic factor during cardiopulmonary bypass surgery

We have investigated the role of the lungs in the extraction of atrial natriuretic factor (ANF) by measuring plasma levels in samples taken from the central circulation in 12 patients (mean age 59 years; range 43 to 68) undergoing cardiac surgery. We also investigated the effects of cardiopulmonary bypass on ANF levels. ANF levels (mean +/- SD) were lower in pulmonary venous samples (41 +/- 20 pg/ml) than in pulmonary arterial samples (54 +/- 18 pg/ml; p less than 0.001), demonstrating 24% extraction of ANF by the lungs. Both left atrial (47 +/- 23 pg/ml) and systemic arterial levels (52 +/- 22 pg/ml) were higher than pulmonary venous levels (both p less than 0.05), indicating secretion of ANF into the left side of the heart. During cardiopulmonary bypass, plasma ANF concentration fell from 68 +/- 23 pg/ml before aortic cross-clamping to 35 +/- 13 pg/ml 10 minutes after and 28 +/- 9 40 minutes after the application of clamps (both p less than 0.001). A rebound rise to 122 +/- 33 pg/ml followed the release of the clamp (p less than 0.001). This study demonstrates that ANF is extracted by the lungs and secreted directly into the left side of the heart. The considerable fall in plasma levels that was observed during aortic cross-clamping might contribute to the neurohumoral activation and increased peripheral resistance observed after prolonged cardiopulmonary bypass and to the risk of renal ischemic injury.

Renal and vascular effects of atrial natriuretic factor during cardiopulmonary bypass

STUDY OBJECTIVE

To evaluate renal and vasodilator effects of synthetic atrial natriuretic factor (ANF) in patients undergoing cardiopulmonary bypass (CPB) with special reference to the applicability of ANF as a diuretic and natriuretic.

DESIGN

The study consisted of two parts. The first 15 consecutive patients in a university hospital received a pharmacologically effective bolus dose of 100 micrograms ANF, as demonstrated previously in other studies, or placebo. After analysis of the bolus data (see "Results" section below), the 12 subsequent patients were administered ANF 50 micrograms as a constant 30-min infusion at a rate of 1.67 micrograms/min or placebo.

PATIENTS

The patients were scheduled for elective coronary artery bypass grafting operation. There was no evidence of congestive heart failure in any patient, and no one had an endocrine or renal disorder.

INTERVENTIONS

After achievement of hypothermia (29 to 30 degrees C of rectal temperature) during CPB, a bolus dose of ANF 100 micrograms was given or an infusion of ANF 1.67 micrograms/min for 30 min, ie, a total dose of 50 micrograms was started. The control patients received placebo correspondingly. Intravenous fluids were administered according to a predetermined scheme.

MEASUREMENTS AND MAIN RESULTS

For the pharmacologic effects of ANF urine volume, urinary sodium excretion and mean arterial pressure (MAP) were measured. Only three of the eight patients receiving the bolus dose of ANF had a diuretic and natriuretic response to the drug, and the responses were significantly related (r = 0.91, p less than 0.05 and r = 0.98, p less than 0.001, respectively) to the prevailing MAP at the time of the bolus administration. The bolus dose of ANF decreased MAP significantly (p less than 0.001 vs placebo) from 65 +/- 6 (mean +/- SEM) to 55 +/- 6 mm Hg within 5 min. The infusion of ANF did not affect MAP, but it increased urine output (16.1 +/- 5.0 ml/min, when the data obtained during the 30-min infusion and a 30-min period after the infusion were combined) and urinary sodium excretion (1,651 +/- 514 microEq/min) significantly (p less than 0.05 and p less than 0.01, respectively) as compared with the corresponding values of 3.3 +/- 1.1 ml/min and 386 +/- 141 microEq/min after placebo.

CONCLUSIONS

Prevailing arterial pressure is an important determinant of the diuretic and natriuretic activity of synthetic ANF in patients undergoing CPB. A low-dose infusion of ANF (50 micrograms within 30 min) provides diuresis and natriuresis without significant changes in MAP in these patients.

Atrial natriuretic peptide levels in brain venous outflow during cardiopulmonary bypass in humans: evidence for extracardiac hormonal production

Atrial natriuretic peptide (ANP) is a hormone with an important role in the regulation of extracellular fluid volume. The ANP gene is not only expressed in the heart, but the high concentration of ANP in cardiac blood makes it difficult to demonstrate extraatrial hormonal secretion in vivo. This issue was addressed during complete cardiopulmonary bypass (CPB) in 13 patients undergoing elective cardiac surgery in whom ANP concentrations were followed in the internal jugular vein, representing largely brain venous outflow, as well as a peripheral vein and radial artery, after the heart and lungs were excluded from circulation. Plasma ANP levels in the peripheral venous circulation showed no significant changes during extracorporeal circulation, although they tended to decrease (from 6.75 +/- 2.16 fmol/mL to 4.76 +/- 0.69 fmol/mL; P greater than 0.05). ANP levels in the radial artery decreased significantly after the exclusion of the heart (from 16.84 +/- 3.51 fmol/mL to 6.83 +/- 0.97 fmol/mL; P less than 0.01). In contrast, ANP concentration in the internal jugular vein increased in 12 of 13 patients during the first 15 minutes of CPB (from 9.49 +/- 1.96 fmol/mL to 15.96 +/- 2.8 fmol/mL; P less than 0.01) and remained above the levels found simultaneously in other sampling sites during CPB. High-performance liquid chromatography analysis of plasma extracts showed multiple peaks of ANP, but the elution patterns of peripheral venous blood and brain outflow were similar. One of the immunoreactive peaks was located at the position of standard human ANP (Ser99-Met110-Tyr126).(ABSTRACT TRUNCATED AT 250 WORDS)