Haemodynamic effects of frusemide and its influence on repetitive rapid volume loading in acute myocardial infarction

Challenging management dogma where evidence is non-existent, weak or outdated

Medical practice is dogged by dogma. A conclusive evidence base is lacking for many aspects of patient management. Clinicians, therefore, rely upon engrained treatment strategies as the dogma seems to work, or at least is assumed to do so. Evidence is often distorted, overlooked or misapplied in the re-telling. However, it is incorporated as fact in textbooks, policies, guidelines and protocols with resource and medicolegal implications. We provide here four examples of medical dogma that underline the above points: loop diuretic treatment for acute heart failure; the effectiveness of heparin thromboprophylaxis; the rate of sodium correction for hyponatraemia; and the mantra of "each hour counts" for treating meningitis. It is notable that the underpinning evidence is largely unsupportive of these doctrines. We do not necessarily advocate change, but rather encourage critical reflection on current practices and the need for prospective studies.

Perioperative risk factors for acute kidney injury after off-pump coronary artery bypass grafting: a retrospective study

Background

Acute kidney injury (AKI) after cardiac surgery is associated with increased morbidity and mortality. Although morbidity of AKI after off-pump coronary artery bypass grafting (OPCAB) has been investigated, little is known about risk factors for AKI after OPCAB. To identify risk factors for AKI, we examined the association between perioperative variables and AKI after OPCAB.

Findings

We reviewed the medical records of consecutive adult patients who underwent isolated OPCAB between January 2010 and February 2013 in a single institute, retrospectively. The primary outcome was the incidence of AKI evaluated using Acute Kidney Injury Network classifications during the first 48 h postoperatively. We investigated preoperative and intraoperative variables, including hemodynamic parameters, as potential risk factors for AKI. The relationship between candidates of AKI and incidence of AKI was examined by multivariate logistic regression analysis.A total of 298 patients were enrolled in this study. Acute kidney injury occurred in 47 patients (15.7%). Multivariate logistic regression analysis showed that intraoperative furosemide administration (odds ratio [OR], 5.163; 95% confidence interval, 2.171 to 12.185; P < 0.001] and diabetes mellitus (OR, 1.954; 95% confidence interval, 1.004 to 3.880; P = 0.049) were significantly associated with AKI.

Conclusions

Intraoperative furosemide administration and diabetes mellitus were significantly associated with AKI in patients who had received OPCAB.

The Effect of Hypertonic (3%) Saline With and Without Furosemide on Plasma Osmolality, Sodium Concentration, and Brain Water Content After Closed Head Trauma in Rats

Adding furosemide (F) to mannitol causes a greater decrease of brain volume, intracranial pressure, and brain water content (BW) as compared with mannitol alone. We examined whether adding F to hypertonic saline (HS) causes less increase of BW early after closed head trauma (CHT) as compared with HS alone. With institutional approval, 125 rats underwent sham surgery or CHT and then immediately received no treatment, HS (1.2 g/kg, 3% solution), or HS + F (2 mg/kg). In groups 1-10 (n = 8/group), the percent BW content was determined at 30, 60, or 120 minutes. In groups 11-14 (n = 8/group), physiologic values were determined at 0, 30, 60, and 120 minutes. At 120 minutes, the increase of BW caused by CHT (sham = 78.9 +/- 0.6% and CHT = 81.5 +/- 2.2%, mean +/- SD) was prevented by HS + F (78.0 +/- 0.8%) but not by HS (80.7 +/- 2.2%). Both HS and HS + F similarly increased plasma osmolality and sodium concentration. Post-CHT hypotension and acidosis (30 and 60 minutes) and decrease of hemoglobin concentration (120 minutes) were less with HS + F than with HS. We conclude that adding F to HS decreases BW without causing more increase of osmolality and Na than that caused by HS alone.

Modern Management of Cardiogenic Pulmonary Edema

Cardiogenic pulmonary edema (CPE) is a life-threatening condition that is frequently encountered in standard emergency medicine practice. Traditionally, diagnosis was based on physical assessment and chest radiography and treatment focused on the use of morphine sulfate and diuretics. Numerous advances in diagnosis and treatment have been made, however. Serum testing for B-type natriuretic peptide (BNP) has improved the accuracy of diagnoses in these patients. Treatment should focus on fluid redistribution with aggressive preload and afterload reduction rather than simply on diuresis. Some specific medications and noninvasive positive pressure ventilation have been shown to be safe and rapidly effective in improving patients' symptoms and improve outcomes.

Decreased blood pressure and vascular smooth muscle tone in mice lacking basolateral Na(+)-K(+)-2Cl(-) cotransporter

The basolateral Na(+)-K(+)-2Cl(-) cotransporter (NKCC1) functions in the maintenance of cellular electrolyte and volume homeostasis. NKCC1-deficient (Nkcc1(-/-)) mice were used to examine its role in cardiac function and in the maintenance of blood pressure and vascular tone. Tail-cuff measurements demonstrated that awake Nkcc1(-/-) mice had significantly lower systolic blood pressure than wild-type (Nkcc1(+/+)) mice (114.5 +/- 2.2 and 131.8 +/- 2.5 mmHg, respectively). Serum aldosterone levels were normal, indicating that extracellular fluid-volume homeostasis was not impaired. Studies using pressure transducers in the femoral artery and left ventricle showed that anesthetized Nkcc1(-/-) mice have decreased mean arterial pressure and left ventricular pressure, whereas myocardial contraction parameters were not significantly different from those of Nkcc1(+/+) mice. When stimulated with phenylephrine, aortic smooth muscle from Nkcc1(+/+) and Nkcc1(-/-) mice exhibited no significant differences in maximum contractility and only moderate dose-response shifts. In phasic portal vein smooth muscle from Nkcc1(-/-) mice, however, a sharp reduction in mechanical force was noted. These results indicate that NKCC1 can be important for the maintenance of normal blood pressure and vascular tone.

Diuretic therapy in elderly heart failure patients with and without left ventricular systolic dysfunction

Long term prescription of diuretics for heart failure is very prevalent among elderly patients, although the rationale for such a treatment strategy is often unclear, as diuretics are not indicated if volume overload is absent. The concept of diastolic heart failure in the elderly might particularly change the role of diuretic therapy, since diuretics may have additional adverse effects in these patients. This paper reviews the effects of diuretic therapy in elderly patients with heart failure, emphasising the differences between patients with normal and decreased left ventricular systolic function. Studies on diuretic withdrawal in elderly patients with heart failure are discussed, with emphasis on issues involved in decision making such as diuretic dose reduction and withdrawal in elderly patients and factors that have been established to predict successful withdrawal. Existing guidelines on the prescription of diuretics in elderly patients with heart failure with normal and decreased left ventricular systolic function and in those with diastolic heart failure are also discussed. By reducing intravascular volume, diuretics may further impair ventricular diastolic filling in patients with diastolic heart failure and thus reduce stroke volume. Indeed, preliminary studies demonstrate that diuretics may provoke or aggravate hypotension on standing and after meals in these patients. Therefore, it is suggested that elderly patients with heart failure with intact left ventricular systolic function should not receive long term diuretic therapy, unless proven necessary to treat or prevent congestive heart failure. This implies that physicians should carefully evaluate the opportunities for diuretic dose tapering or withdrawal in all of these patients, and that a cautiously guided intermittent diuretic treatment modality may be critical in the care for older patients with heart failure with intact left ventricular systolic function.

Lack of renoprotective effects of dopamine and furosemide during cardiac surgery

Because development of acute renal failure is one of the most potent predictors of outcome in cardiac surgery patients, the prevention of renal dysfunction is of utmost importance in perioperative care. In a double-blind randomized controlled trial, the effectiveness of dopamine or furosemide in prevention of renal impairment after cardiac surgery was evaluated. A total of 126 patients with preoperatively normal renal function undergoing elective cardiac surgery received a continuous infusion of either "renal-dose" dopamine (2 microg/kg per min) (group D), furosemide (0.5 microg/kg per min) (group F), or isotonic sodium chloride as placebo (group P), starting at the beginning of surgery and continuing for 48 h or until discharge from the intensive care unit, whichever came first. Renal function parameters and the maximal increase of serum creatinine above baseline value within 48 h (deltaCrea(max)) were determined. The increase in plasma creatinine was twice as high in group F as in groups D and P (P < 0.01). Acute renal injury (defined as deltaCreamax) >0.5 mg/dl) occurred more frequently in group F (six of 41 patients) than in group D (one of 42) and group P (zero of 40) (P < 0.01). (The difference between group D and group P was not significant.) Creatinine clearance was lower in group F (P < 0.05). Two patients in group F required renal replacement therapy. The mean volume of infused fluids, blood urea nitrogen, serum sodium, serum potassium, and osmolar- and free-water clearance was similar in all groups. It was shown that continuous infusion of dopamine for renal protection was ineffective and was not superior to placebo in preventing postoperative dysfunction after cardiac surgery. In contrast, continuous infusion of furosemide was associated with the highest rate of renal impairment. Thus, renaldose dopamine is ineffective and furosemide is even detrimental in the protection of renal dysfunction after cardiac surgery.

Comparison of chronic neutral endopeptidase inhibition and furosemide in an ovine model of heart failure

The hemodynamic, hormonal, and metabolic effects of chronic neutral endopeptidase (NEP) 24.11 inhibition and furosemide were compared in the pacing model of ovine heart failure (HF). Intravenous SCH 39370 induced a dose-related inhibition of NEP activity during 4-days treatment, in association with a transient increase in plasma atrial natriuretic peptide (ANP) and, at the higher dose, an increased mean level of plasma cyclic guanosine monophosphate. There was a significant and persistent decrease in left atrial pressure, a brief increase in cardiac output (CO), and a tendency for arterial pressure to be reduced. Significant dose-related diuresis and natriuresis were also observed. Furosemide induced a similar hemodynamic response, associated with greater diuresis and natriuresis. Both agents significantly reduced plasma aldosterone levels. Coinfusion of captopril on day 4 of treatment resulted in similar responses in both the SCH 39370- and furosemide pretreated groups. Chronic NEP inhibition significantly alters circulatory and renal function and appears to be as effective as furosemide in reducing cardiac preload in this model of congestive HF.

Furosemide elicits immediate sympathoexcitation via a renal mechanism independent of angiotensin II

This investigation aimed at examing the hypothesis that furosemide elicits renal sympathoexcitation through stimulation of renal renin release, which in turn produces increased plasma angiotensin II levels, causing centrally mediated sympathoexcitation. In addition, direct central nervous actions of furosemide on central control of mean arterial pressure, heart rate, and efferent renal sympathetic nerve activity were examined. Furosemide (300 mg/kg intravenously) was administered to four groups of rats: (1) control; (2) nephrectomized; (3) with intravenous losartan blockade (10 mumol/kg); and (4) with intracerebroventricular losartan blockade (10 nmol). In a fifth group of rats, furosemide was administered intracerebroventricularly (0, 2.5, 25 or 250 micrograms). To eliminate reflex control of mean arterial pressure, heart rate and efferent renal sympathetic nerve activity, all experiments were performed in rats with sinoaortic denervation and bilateral vagotomy. Experiments were performed during Saffan anaesthesia (0.9% alphaxalone/0.3% alphadolone), and rats were paralyzed with pancuronium and artifically ventilated. Furosemide produced an immediate 40% increase in efferent renal sympathetic nerve activity while the furosemide vehicle, 2 vol.% ethanolamine, did not affect efferent renal sympathetic nerve activity. The furosemide-induced increase in efferent renal sympathetic nerve activity was abolished in rats with bilateral nephrectomy but it was not affected by intravenous or intracerebroventricular losartan blockade. Intracerebroventricular angiotensin II produced an increase in mean arterial pressure and efferent renal sympathetic nerve activity whereas intravenous angiotensin II produced a pressor response in absence of increased efferent renal sympathetic nerve activity. Losartan effectively blocked responses to intravenous or intracerebroventricular angiotensin II. Intracerebroventricular administration of furosemide produced no changes in mean arterial pressure, heart rate or efferent renal sympathetic nerve activity.(ABSTRACT TRUNCATED AT 250 WORDS)

Diuretics in postinfarction heart failure

Severe left ventricular failure, as evidenced by radiographic pulmonary edema or raised left ventricular filling pressure, accompanying acute myocardial infarction, carries a high mortality risk. In this situation, the intravenous loop-diuretic furosemide induces a rapid reduction in the raised left ventricular filling pressure due to an immediate and substantial increase in systemic venous compliance accompanied by increasing diuresis. This diuretic-induced venodilatation is probably due to the release of prostaglandins. The transient systemic arterial constriction and small increase in systemic blood pressure that follows intravenous furosemide probably results from the release of renin and subsequent activation of angiotensin. These diuretic induced hemodynamic changes are accompanied by restoration of the vasodilator reflex, which enables the heart to accommodate an acute volume load. Orally administered loop diuretics achieve slower, but similar, directional hemodynamic changes. There is no information on hemodynamic or neuroendocrine dose-response effects of loop diuretics, and there is no information pertaining to the use of other diuretic groups in this situation. The hemodynamic changes induced by furosemide summate with the changes induced by other anti-heart-failure drugs. In this subset of patients with acute myocardial infarction and severe heart failure, the influence of the diuretics on morbidity incidence and mortality risk remains to be measured.

Central hemodynamic effects of diuretic therapy in chronic heart failure

In chronic heart failure diuretic drugs improve central hemodynamic variables and cardiac pumping secondary to altered plasma and extracellular volumes; humoral markers of these changes include increased plasma renin and aldosterone levels. The latter increases are maximal over the first week but decline with chronic therapy. The plasma alpha-ANP levels show a reciprocal effect; these data are compatible with a rapid contraction of the plasma volume which is sustained during chronic therapy. The acute hemodynamic actions of diuretic agents reflect both immediate and direct vascular actions and also effects secondary to diuresis (volume redistribution). At rest substantial reductions in pulmonary "wedge" pressure (-29%), with a consequent fall in cardiac output (-10%), are described. Total systemic vascular resistance initially increases but "reverse autoregulation" over subsequent weeks returns this elevation gradually towards control values. Tolerance to these initial hemodynamic effects does not occur with maintained therapy; moreover, echocardiographic markers of contractility and exercise capacity may increase. The early venodilator effects of diuretic drugs can be attributed to prostaglandin release and the initial pressor actions to activation of the renin angiotensin system; these vascular actions may have limited relevance to long-term beneficial effects on hemodynamics. Direct pulmonary vasodilation and improved pulmonary compliance remain an interesting finding. Although most patients are both symptomatically and hemodynamically improved at rest, the actions during exercise are more varied. Some individuals with severely impaired left ventricular function show little hemodynamic improvement, whereas those with milder dysfunction usually benefit; in the main this is probably related to the latter being on a steeper cardiac function curve.(ABSTRACT TRUNCATED AT 250 WORDS)

Acute arteriolar vasoconstriction following furosemide in conscious spontaneously hypertensive rats

In a previous study in conscious spontaneously hypertensive rats (SHR), we observed an immediate decrease in the cardiac index (CI) and an increase in the total peripheral resistance index (TPRI) following the administration of furosemide. The present study was designed to evaluate the regional hemodynamic effects and the involvement of sinoaortic baroreceptors in the increase in TPRI. In SHR instrumented for the measurement of central hemodynamics, 8 mg.kg-1 furosemide decreased CI from 31.0 +/- 2.5 ml.min-1.100 g bw-1 by 9.5 +/- 1.3 ml.min-1.100 g bw-1 (n = 7). TPRI increased maximally from 5.7 +/- 0.8 by 2.7 +/- 0.5 mm Hg.min.100 g bw.ml-1. The effect on TPRI was not affected by sinoaortic denervation (SAD) to abolish arterial baroreflexes. However, furosemide induced a significantly greater decrease in CI (-12.6 +/- 1.2 ml.min-1.100 g bw-1; n = 7) after SAD. Furosemide effectively reduced the mean arterial pressure in SAD SHR (-21 +/- 9 mm Hg) but not in sham-denervated SHR. Furosemide (8 mg.kg-1) reduced renal, mesenteric and hindquarter blood flow to a comparable extent (approximately 20%) in intact SHR. The reduction in renal flow at 3.5 min after injection (-17.9 +/- 4.1%; n = 8) was significantly greater than the reduction in mesenteric (-7.1 +/- 4.7%) and hindquarter blood flow (-4.2 +/- 3.7%), suggesting that the renal bed responds faster. Thereafter, the flow reductions in the three beds were not different. The results show that furosemide causes a general vasoconstriction in conscious SHR.(ABSTRACT TRUNCATED AT 250 WORDS)

Immediate effects of bumetanide on systemic haemodynamics and left ventricular volume in acute and chronic heart failure

1 The haemodynamic and radionuclide effects of i.v. bumetanide (25 micrograms kg-1) were prospectively studied in 24 patients with angiographically documented coronary artery disease and either acute exercise-induced (Group I, n = 12) or chronic (Group II, n = 12) heart failure. 2 Bumetanide at rest increased systemic arterial blood pressure and vascular resistance index; cardiac index and pulmonary artery occluded pressure (PAOP) were reduced at an unchanged heart rate in all patients. The left ventricular ejection fraction fell in patients with normal resting left ventricular filling pressure without change in those with chronic heart failure. The cardiac volumes were unchanged in either group. 3 During constant-load supine bicycle exercise, there were similar effects on systemic arterial pressures, vascular resistance index and PAOP; however the cardiac index was maintained at a reduced left ventricular filling pressure and unchanged ejection fraction and volumes. 4 These data demonstrate immediate mild pressor and vasoconstrictor actions of bumetanide which appear independent of the state of cardiac function; they suggest that any immediate improvement in patient symptomatology following bumetanide may be consequent on the reduction in PAOP; short-term reductions in volume may not occur.

Blood volume distribution in the Trendelenburg position

The Trendelenburg position is used frequently in treating hypotensive patients. It is believed that placing patients in the Trendelenburg position causes an autotransfusion of blood to the central circulation. No published studies document the volume of blood displaced centrally. In our study ten volunteers were placed in the Trendelenburg position. Blood volumes were determined from body surface area, and radionuclide scanning was used to determine blood volume distribution. Placing normovolemic volunteers in the Trendelenburg resulted in a 1.8% (median) displacement of the total volume centrally. The autotransfusion of blood produced by the Trendelenburg position is small and is unlikely to have an important clinical effect.