Continuous intravenous furosemide in haemodynamically unstable children after cardiac surgery

Diuretics in neonatology: a narrative review and update

Diuretics are medications that promote the excretion of water and electrolytes. They are primarily used in the management and treatment of states of inappropriate salt and water retention. Diuretics represent one of the most common classes of drugs administered to sick neonates, the more so in very low birth weight infants. Diuretic drugs, especially loop diuretics, are often administered in the neonatal intensive care unit as off-label medications. This is the case for a variety of clinical situations, in which an increase in sodium excretion is not the primary goal of treatment (transitory tachypnoea of the newborn at term, hyaline membrane disease, patent ductus arteriosus of preterm infants). Thiazides and furosemide are widely used to treat preterm infants with oxygen-dependent chronic lung disease, despite a lack of data on beneficial effect of long-term therapy on pulmonary function or clinical outcome. This article reviews the mechanism of action, indications, administration, posology, adverse effects and contraindications of diuretics in newborn infants. Based on the most recent information available in the literature, we will discuss data supporting (or questioning) the use of diuretic in specific neonatal diseases. Research priorities over this issue will be briefly presented.

Furosemide in pediatric intensive care: a retrospective cohort analysis

Introduction

Furosemide is the most commonly used medication in pediatric intensive care. Growing data indicates improved hemodynamic stability and efficacy of furosemide infusions compared to intermittent injections, thereby suggesting furosemide infusions might be considered as first line therapy in critically ill, paediatric patients. The objective of this study is to examine furosemide treatment as either continuous infusions or intermittent injections and subsequent patient outcomes.

Methods

This is a retrospective cohort analysis of patients treated in a pediatric intensive care unit (ICU) over a nine year period (July 31st 2006 and July 31, 2015). Eligible patients were admitted to either the general pediatric or cardiac specific ICU for a duration of at least 6 hours and who received intravenous furosemide treatment.

Results

A total of 7,478 patients were identified who received a total of 118,438 furosemide administrations for a total of 113,951 (96%) intermittent doses and 4,487 (4%) infusions running for a total of 1,588,750 hours. A total of 5,996 (80%) patients received exclusively furosemide injections and 1,482 (20%) patients received at least one furosemide infusion. A total of 193 patients died during ICU admission, amounting to 87 (6%) of the 1,482 patients who received an infusion and 106 (2%) of the 5,996 who received intermittent injections. Multivariable regression analysis showed no statistically significant decrease in adjusted mortality for patients who received furosemide injections compared to furosemide infusions (aOR 1.20, CI 0.76-1.89).

Discussion

This retrospective study observed similar mortality for patients who received furosemide infusions compared to furosemide injections. More research on furosemide in the ICU could provide insights on fluid management, drug effectiveness, and pharmacologic stewardship for critically ill children.

Use of diuretics in the neonatal period

The use of diuretics is extremely frequent in sick neonates, the more so in very premature newborn infants. The use of diuretics in patients whose kidney function is immature necessitates a thorough knowledge of renal developmental physiology and pathophysiology. This review presents the basic aspects of body fluid homeostasis in the neonate, discusses the development of kidney function, and describes the mechanisms involved in electrolyte and water reabsorption along the nephron. Diuretics are then classified according to the site of their action on sodium reabsorption. The use of diuretics in sodium-retaining states, in oliguric states, in electrolyte disorders, and in arterial hypertension, as well as in a few specific disorders, is presented. Common and specific adverse effects are discussed. Recommended dosages for the main diuretics used in the neonatal period are given. New developments in diuretic therapy are briefly mentioned.

A systematic review of the evidence supporting post-operative medication use in congenital heart disease

BACKGROUND

Targeted drug development efforts in patients with CHD are needed to standardise care, improve outcomes, and limit adverse events in the post-operative period. To identify major gaps in knowledge that can be addressed by drug development efforts and provide a rationale for current clinical practice, this review evaluates the evidence behind the most common medication classes used in the post-operative care of children with CHD undergoing cardiac surgery with cardiopulmonary bypass.

METHODS

We systematically searched PubMed and EMBASE from 2000 to 2019 using a controlled vocabulary and keywords related to diuretics, vasoactives, sedatives, analgesics, pulmonary vasodilators, coagulation system medications, antiarrhythmics, steroids, and other endocrine drugs. We included studies of drugs given post-operatively to children with CHD undergoing repair or palliation with cardiopulmonary bypass.

RESULTS

We identified a total of 127 studies with 51,573 total children across medication classes. Most studies were retrospective cohorts at single centres. There is significant age- and disease-related variability in drug disposition, efficacy, and safety.

CONCLUSION

In this study, we discovered major gaps in knowledge for each medication class and identified areas for future research. Advances in data collection through electronic health records, novel trial methods, and collaboration can aid drug development efforts in standardising care, improving outcomes, and limiting adverse events in the post-operative period.

A systematic review of the evidence supporting post-operative diuretic use following cardiopulmonary bypass in children with Congenital Heart Disease

BACKGROUND

Paediatric cardiac surgery on cardiopulmonary bypass induces substantial physiologic changes that contribute to post-operative morbidity and mortality. Fluid overload and oedema are prevalent complications, routinely treated with diuretics. The optimal diuretic choice, timing of initiation, dose, and interval remain largely unknown.

METHODS

To guide clinical practice and future studies, we used PubMed and EMBASE to systematically review the existing literature of clinical trials involving diuretics following cardiac surgery from 2000 to 2020 in children aged 0-18 years. Studies were assessed by two reviewers to ensure that they met eligibility criteria.

RESULTS

We identified nine studies of 430 children across four medication classes. Five studies were retrospective, and four were prospective, two of which included randomisation. All were single centre. There were five primary endpoints - urine output, acute kidney injury, fluid balance, change in serum bicarbonate level, and required dose of diuretic. Included studies showed early post-operative diuretic resistance, suggesting higher initial doses. Two studies of ethacrynic acid showed increased urine output and lower diuretic requirement compared to furosemide. Children receiving peritoneal dialysis were less likely to develop fluid overload than those receiving furosemide. Chlorothiazide, acetazolamide, and tolvaptan demonstrated potential benefit as adjuncts to traditional diuretic regimens.

CONCLUSIONS

Early diuretic resistance is seen in children following cardiopulmonary bypass. Ethacrynic acid appears superior to furosemide. Adjunct diuretic therapies may provide additional benefit. Study populations were heterogeneous and endpoints varied. Standardised, validated endpoints and pragmatic trial designs may allow investigators to determine the optimal diuretic, timing of initiation, dose, and interval to improve post-operative outcomes.

Use of Fenoldopam in Children with Congenital Heart Disease to Decrease Fluid Balance: A Retrospective, Descriptive Study and Insights into Predictors of Decreased Fluid Balance

This retrospective study aimed to determine if fenoldopam is associated with a decrease in fluid balance and to define the factors that may promote this in children with a history of congenital heart disease at the cardiac intensive care unit (CICU). Patients cared from January 2014 to December 2018 in the CICU were reviewed, and those on fenoldopam infusion were identified. Patient cohort data included demographics, clinical information, laboratory results, hemodynamic and urine output measurements, and information regarding fenoldopam infusion were compared between those with and without decrease in fluid balance. Forty-six patients were identified. Patients received a starting dose of fenoldopam of 0.2 mcg/kg/h, a maximum dose of 0.3 mcg/kg/h, and duration of 64 hours. Over the 4-hour study period, statistically significant change was noted in systolic pressure (decrease of 5.4%; p < 0.001), diastolic pressure (decrease of 3.5%; p = 0.01), fluid balance, and urine output (decrease of 1.3%; p = 0.027). In the cohort, 34 patients (74%) had a decrease in fluid balance, 18 (39%) had an increase in urine output, and 25 (54%) had a decrease in fluid input after the initiation of fenoldopam. Patients that had a decrease in fluid balance tended to have a higher blood urea nitrogen level at the time of fenoldopam initiation. Fenoldopam was associated with decrease in fluid balance and fluid input, but not associated with an increase in urine output. The identification of factors that can decrease fluid balance may help identify those patients who can be benefited with this treatment.

Lower-Dose, Intravenous Chlorothiazide Is an Effective Adjunct Diuretic to Furosemide Following Pediatric Cardiac Surgery

OBJECTIVES

Postoperative fluid overload is ubiquitous in neonates and infants following operative intervention for congenital heart defects; ineffective diuresis is associated with poor outcomes. Diuresis with furosemide is widely used, yet there is often resistance at higher doses. In theory, furosemide resistance may be overcome with chlorothiazide; however, its efficacy is unclear, especially in lower doses and in this population. We hypothesized the addition of lower-dose, intravenous chlorothiazide following surgery in patients on high-dose furosemide would induce meaningful diuresis with minimal side effects.

METHODS

This was a retrospective, cohort study. Postoperative infants younger than 6 months, receiving high-dose furosemide, and given lower-dose chlorothiazide (1-2 mg/kg every 6-12 hours) were identified. Diuretic doses, urine output, fluid balance, vasoactive-inotropic scores, total fluid intake, and electrolyte levels were recorded.

RESULTS

There were 73 patients included. The addition of lower-dose chlorothiazide was associated with a significant increase in urine output (3.8 ± 0.18 vs 5.6 ± 0.27 mL/kg/hr, p < 0.001), more negative fluid balance (16.1 ± 4.2 vs -25.0 ± 6.3 mL/kg/day, p < 0.001), and marginal changes in electrolytes. Multivariate analysis was performed, demonstrating that increased urine output and more negative fluid balance were independently associated with addition of chlorothiazide. Subgroup analysis of 21 patients without a change in furosemide dose demonstrated the addition of chlorothiazide significantly increased urine output (p = 0.03) and reduced fluid balance (p < 0.01), further validating the adjunct effects of chlorothiazide.

CONCLUSION

Lower-dose, intravenous chlorothiazide is an effective adjunct treatment in postoperative neonates and infants younger than 6 months following cardiothoracic surgery.

Peritoneal Dialysis Vs Diuretics in Children After Congenital Heart Surgery

BACKGROUND

This study sought to evaluate outcomes of patients undergoing congenital heart surgery who underwent peritoneal dialysis (PD) vs a diuretic regimen.

METHODS

This study conducted a comprehensive search in Medline, EMBASE, Scopus, the Cochrane Central Register of Controlled Trials, and the Cochrane Database of Systematic Reviews from the databases' inception through April 24, 2018. Independent reviewers selected studies and extracted data. A random effects meta-analysis was performed to pool the outcomes of interest across studies.

RESULTS

A total of 8 studies (2 prospective studies, 2 randomized clinical trials, and 4 retrospective studies) with 507 patients were included in this review. A total of 204 (40%) patients underwent PD, whereas the remaining patients underwent fluid removal with diuretics. The analyses demonstrated a significantly shorter time of mechanical ventilation in those patients who underwent PD (mean difference, -1.25 days; 95% confidence interval, -2.18 to -0.33; P = .008) and increased odds of mortality (odds ratio, 2.27; 95% confidence interval, 1.13 to 4.56; P = .02) compared with the diuretic group. No differences were identified in terms of incidence of negative fluid balance by postoperative day 1, presence of peritonitis, and intensive care unit length of stay.

CONCLUSIONS

The meta-analysis did not identify differences between the 2 groups with regard to negative fluid balance after postoperative day 1, incidence of peritonitis, or length of intensive care unit stay. There is a need for large, prospective, multicenter studies to evaluate the benefits and complications associated with PD use further in selected children after congenital heart surgery. Because some of the outcomes were present in only 2 studies, results from the pooled analysis may be underpowered.

Acute kidney injury after pediatric cardiac surgery

Acute kidney injury is a common complication after pediatric cardiac surgery. The definition, staging, risk factors, biomarkers and management of acute kidney injury in children is detailed in the following review article.

Efficacy and Safety of a Furosemide Continuous Infusion Following Cardiac Surgery

Objective:

To review the literature regarding the efficacy and safety of continuous intravenous infusion of loop diuretics following cardiac surgery.

Data Sources:

Articles were identified through a MEDLINE search (1966–March 2006) using the key words furosemide, bumetanide, torsemide, ethacrynic acid, loop diuretics, continuous infusions, intravenous infusions, surgery, cardiac surgery, cardiovascular surgery, and thoracic surgery. Search results were limited to studies in human subjects published in English. Additional references were identified through review of the bibliographies of the articles cited.

Study Selection and Data Extraction:

All clinical trials and observational reports identified that evaluated or described the efficacy and/or safety of a continuous infusion of a loop diuretic in adult or pediatric patients who had undergone cardiac surgery were included in this review.

Data Synthesis:

Loop diuretics are often used to promote diuresis following cardiac surgery. Studies in patients who have undergone cardiac surgery have demonstrated that a more consistent and sustained diuresis is produced by a continuous infusion of furosemide compared with intermittent bolus doses of furosemide. However, there does not appear to be a significant difference in total urine output or change in serum electrolyte levels when furosemide is administered as a continuous infusion compared with intermittent bolus doses.

Conclusions:

A continuous infusion of furosemide is an effective and safe method of diuresis in patients undergoing cardiac surgery.

Clinical Factors Associated with Dose of Loop Diuretics After Pediatric Cardiac Surgery: Post Hoc Analysis

A post hoc analysis of a randomized controlled trial comparing the clinical effects of furosemide and ethacrynic acid was conducted. Infants undergoing cardiac surgery with cardiopulmonary bypass were included in order to explore which clinical factors are associated with diuretic dose in infants with congenital heart disease. Overall, 67 patients with median (interquartile range) age of 48 (13-139) days were enrolled. Median diuretic dose was 0.34 (0.25-0.4) mg/kg/h at the end of postoperative day (POD) 0 and it significantly decreased (p = 0.04) over the following PODs; during this period, the ratio between urine output and diuretic dose increased significantly (p = 0.04). Age (r -0.26, p = 0.02), weight (r -0.28, p = 0.01), cross-clamp time (r 0.27, p = 0.03), administration of ethacrynic acid (OR 0.01, p = 0.03), and, at the end of POD0, creatinine levels (r 0.3, p = 0.009), renal near-infrared spectroscopy saturation (-0.44, p = 0.008), whole-blood neutrophil gelatinase-associated lipocalin levels (r 0.30, p = 0.01), pH (r -0.26, p = 0.02), urinary volume (r -0.2755, p = 0.03), and fluid balance (r 0.2577, p = 0.0266) showed a significant association with diuretic dose. At multivariable logistic regression cross-clamp time (OR 1.007, p = 0.04), use of ethacrynic acid (OR 0.2, p = 0.01) and blood pH at the end of POD0 (OR 0.0001, p = 0.03) was independently associated with diuretic dose. Early resistance to loop diuretics continuous infusion is evident in post-cardiac surgery infants: Higher doses are administered to patients with lower urinary output. Independently associated variables with diuretic dose in our population appeared to be cross-clamping time, the administration of ethacrynic acid, and blood pH.

Pediatric Cardiac Intensive Care Society 2014 Consensus Statement: Pharmacotherapies in Cardiac Critical Care Fluid Management

OBJECTIVE

In this Consensus Statement, we review the etiology and pathophysiology of fluid disturbances in critically ill children with cardiac disease. Clinical tools used to recognize pathologic fluid states are summarized, as are the mechanisms of action of many drugs aimed at optimal fluid management.

DATA SOURCES

The expertise of the authors and a review of the medical literature were used as data sources.

DATA SYNTHESIS

The authors synthesized the data in the literature in order to present clinical tools used to recognize pathologic fluid states. For each drug, the physiologic rationale, mechanism of action, and pharmacokinetics are synthesized, and the evidence in the literature to support the therapy is discussed.

CONCLUSIONS

Fluid management is challenging in critically ill pediatric cardiac patients. A myriad of causes may be contributory, including intrinsic myocardial dysfunction with its associated neuroendocrine response, renal dysfunction with oliguria, and systemic inflammation with resulting endothelial dysfunction. The development of fluid overload has been associated with adverse outcomes, including acute kidney injury, prolonged mechanical ventilation, increased vasoactive support, prolonged hospital length of stay, and mortality. An in-depth understanding of the many factors that influence volume status is necessary to guide optimal management.

Implementation of a diuretic stewardship program in a pediatric cardiovascular intensive care unit to reduce medication expenditures

PURPOSE

The implementation of a diuretic stewardship program in a pediatric cardiovascular intensive care unit (ICU) is described.

METHODS

This retrospective study compared the use of i.v. chlorothiazide and i.v. ethacrynic acid in pediatric cardiovascular surgery patients before and after implementation of a diuretic stewardship program. All pediatric patients admitted to the pediatric cardiovascular service were included. The cardiovascular surgery service was educated on formal indications for specific diuretic agents, and the diuretic stewardship program was implemented on January 1, 2013. Under the stewardship program, i.v. ethacrynic acid was indicated in patients with a sulfonamide allergy, and i.v. chlorothiazide was considered appropriate in patients receiving maximized i.v. loop diuretic doses. A detailed review of the pharmacy database and medical records was performed for each patient to determine i.v. chlorothiazide and i.v. ethacrynic acid use and expenditures, appropriateness of use, days using a ventilator, and cardiovascular ICU length of stay.

RESULTS

After implementation of diuretic stewardship, the use of i.v. chlorothiazide decreased by 74% (531 fewer doses) while i.v. ethacrynic acid use decreased by 92% (47 fewer doses), resulting in a total reduction of $91,398 in expenditures on these diuretics over the six-month study period and an estimated annual saving of over $182,000. The median number of days using a ventilator and the length of ICU stay did not differ significantly during the study period.

CONCLUSION

Implementation of a diuretic stewardship program reduced the use of i.v. chlorothiazide and i.v. ethacrynic acid without adversely affecting clinical outcomes such as ventilator days and length of stay in a pediatric cardiovascular ICU.

Bumetanide continuous infusions in critically ill pediatric patients

OBJECTIVE

Limited data exist for the use of bumetanide continuous infusions in children. The purpose of this study was to evaluate the use of bumetanide continuous infusions in critically ill pediatric patients.

DESIGN

This study was an institutional review board approved, single-center, retrospective chart review of 95 patients. Dosing practices were described by rate (μg/kg/hr), duration (days), and previous diuretic use. Efficacy, determined by ability to achieve negative fluid balance and time to reach negative fluid balance, was assessed at 12, 24, and 48 hours. Safety was evaluated based on prevalence of adverse drug reactions. Adverse drug reactions were predefined as serum potassium concentration less than 3 mEq/L, serum chloride concentration less than 90 mEq/L, serum carbon dioxide concentration greater than 35 mEq/L, and serum creatinine increased greater than 1.5 times baseline and above patient-specific normal range.

SETTING

Le Bonheur Children's Hospital, Memphis, TN.

PATIENTS

Critically ill patients who are 18 years old or younger and received bumetanide continuous infusions. A total of 95 patients were included.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

The mean dose of bumetanide was 5.7 ± 2.2 μg/kg/hr (1-10 μg/kg/hr) with a median duration of 3.3 days (0.3-18.5). The total percentage of patients achieving negative fluid balance by 48 hours was 76% with 54% of patients reaching negative fluid balance within 12 hours.

CONCLUSIONS

This study showed that a bumetanide dose of 5.7 μg/kg/hr was effective in achieving negative fluid balance in the majority of critically ill pediatric patients. Additionally, bumetanide appears to be a safe loop diuretic for use as a continuous infusion at the doses described in critically ill pediatric patients.

Furosemide versus ethacrynic acid in pediatric patients undergoing cardiac surgery: a randomized controlled trial

Introduction

Clinical effects of furosemide (F) and ethacrynic acid (EA) continuous infusion on urine output (UO), fluid balance, and renal, cardiac, respiratory, and metabolic function were compared in infants undergoing surgery for congenital heart diseases.

Methods

A prospective randomized double-blinded study was conducted. Patients received 0.2 mg/kg/h (up to 0.8 mg/kg/h) of either F or EA.

Results

In total, 38 patients were enrolled in the F group, and 36, in the EA group. No adverse reactions were recorded. UO at postoperative day (POD) 0 was significantly higher in the EA group, 6.9 (3.3) ml/kg/h, compared with the F group, 4.6 (2.3) ml/kg/h (P = 0.002) but tended to be similar in the two groups thereafter. Mean administered F dose was 0.33 (0.19) mg/kg/h compared with 0.22 (0.13) mg/kg/h of EA (P < 0.0001). Fluid balance was significantly more negative in the EA group at postoperative day 0: −43 (54) ml/kg/h versus −17 (32) ml/kg/h in the F group (P = 0.01). Serum creatinine, cystatin C and neutrophil gelatinase-associated lipocalin levels and incidence of acute kidney injury did not show significant differences between groups. Metabolic alkalosis occurred frequently (about 70% of cases) in both groups, but mean bicarbonate level was higher in the EA group: 27.8 (1.5) M in the F group versus 29.1 (2) mM in the EA group (P = 0.006). Mean cardiac index (CI) values were 2.6 (0.1) L/min/m² in the F group compared with 2.98 (0.09) L/min/m² in the EA group (P = 0.0081). Length of mechanical ventilation was shorter in the EA group, 5.5 (8.8) days compared with the F group, 6.7 (5.9) (P = 0.06). Length of Pediatric Cardiac Intensive Care Unit (PCICU) admission was shorter in the EA group: 14 (19) days compared with 16 (15) in the F group (P = 0.046).

Conclusions

In cardiac surgery infants, EA produced more UO compared with F on POD0. Generally, a smaller EA dose is required to achieve similar UO than F. EA and F were safe in terms of renal function, but EA caused a more-intense metabolic alkalosis. EA patients achieved better CI, and shorter mechanical ventilation and PCICU admission time.

Trial registration

Clinicaltrials.gov NCT01628731. Registered 24 June 2012.

Ethacrynic Acid continuous infusions in critically ill pediatric patients

OBJECTIVES

The purpose of this study was to describe dosage regimens and treatment outcomes in critically ill children receiving ethacrynic acid continuous infusions (CI).

METHODS

This retrospective cross-sectional study evaluated patients less than 18 years of age who received ethacrynic acid CI with a duration exceeding 12 hours, from January 1, 2007, through January 31, 2012. The primary objective was to determine the mean/median doses of ethacrynic acid CI. Secondary objectives were to assess surrogate efficacy markers (e.g., urine output [UOP], fluid balance) and the number of patients with electrolyte abnormalities or metabolic alkalosis. Descriptive statistics were used. A series of repeated measures analyses of variance were conducted to assess differences in surrogate efficacy markers and in adverse events that occurred pre-, mid-, and posttherapy.

RESULTS

Nine patients were included. The mean ± SD initial and maximum doses (mg/kg/hr) were 0.13 ± 0.07 (median 0.1; range, 0.08-0.3) and 0.17 ± 0.08 (median, 0.16; range 0.09-0.3), respectively. The median UOP (mL/kg/hr) pre-, mid-, and postinfusions (interquartile range [IQR]) were 2.4 (1.8-3.2), 4.2 (3.5-6), and 4 (3.4-5.3), respectively. The median fluid balance (mL; IQR) was 189 (90-526), -258 (-411.7 to 249) and -113.5 (-212.5 to 80.2), respectively. There were statistically significant differences in UOP and fluid balance pre- versus mid-therapy (0.014) and pre- versus posttherapy (p=0.010). No significant differences were noted with magnesium and potassium. Five children (55.6%) developed metabolic alkalosis.

CONCLUSIONS

This study provides preliminary evidence for ethacrynic acid CI in children. The median initial dose and maximum dose in this cohort were 0.13 mg/kg/hr and 0.17 mg/kg/hr, respectively. Larger prospective studies are needed to confirm these findings.

Clinical pharmacology of furosemide in neonates: a review

Furosemide is the diuretic most used in newborn infants. It blocks the Na⁺-K⁺-2Cl⁻ symporter in the thick ascending limb of the loop of Henle increasing urinary excretion of Na⁺ and Cl⁻. This article aimed to review the published data on the clinical pharmacology of furosemide in neonates to provide a critical, comprehensive, authoritative and, updated survey on the metabolism, pharmacokinetics, pharmacodynamics and side-effects of furosemide in neonates. The bibliographic search was performed using PubMed and EMBASE databases as search engines; January 2013 was the cutoff point. Furosemide half-life (t_1/2) is 6 to 20-fold longer, clearance (Cl) is 1.2 to 14-fold smaller and volume of distribution (Vd) is 1.3 to 6-fold larger than the adult values. t_1/2 shortens and Cl increases as the neonatal maturation proceeds. Continuous intravenous infusion of furosemide yields more controlled diuresis than the intermittent intravenous infusion. Furosemide may be administered by inhalation to infants with chronic lung disease to improve pulmonary mechanics. Furosemide stimulates prostaglandin E2 synthesis, a potent dilator of the patent ductus arteriosus, and the administration of furosemide to any preterm infants should be carefully weighed against the risk of precipitation of a symptomatic patent ductus arteriosus. Infants with low birthweight treated with chronic furosemide are at risk for the development of intra-renal calcifications.

Clinical pharmacology of the loop diuretics furosemide and bumetanide in neonates and infants

The loop diuretics furosemide and bumetanide are used widely for the management of fluid overload in both acute and chronic disease states. To date, most pharmacokinetic studies in neonates have been conducted with furosemide and little is known about bumetanide. The aim of this article was to review the published data on the pharmacology of furosemide and bumetanide in neonates and infants in order to provide a critical analysis of the literature, and a useful tool for physicians. The bibliographic search was performed electronically using PubMed and EMBASE databases as search engines and March 2011 was the cutoff point. The half-life (t(½)) of both furosemide and bumetanide is considerably longer in neonates than in adults and consequently the clearance (CL) of these drugs is reduced at birth. In healthy volunteers, plasma t(½) of furosemide ranges from 33 to 100 minutes, whereas in neonates it ranges from 8 to 27 hours. The volume of distribution (V(d)) of furosemide undergoes little variation during neonate maturation. The dose of furosemide, administered by intermittent intravenous infusion, is 1 mg/kg and may increase to a maximum of 2 mg/kg every 24 hours in premature infants and every 12 hours in full-term infants. Comparison of continuous infusion versus intermittent infusion of furosemide showed that the diuresis is more controlled with fewer hemodynamic and electrolytic variations during continuous infusion. The appropriate infusion rate of furosemide ranges from 0.1 to 0.2 mg/kg/h and when the diuresis is <1 mL/kg/h the infusion rate may be increased to 0.4 mg/kg/h. Treatment with theophylline before administration of furosemide results in a significant increase of urine flow rate. Bumetanide is more potent than furosemide and its dose after intermittent intravenous infusion ranges from 0.005 to 0.1 mg/kg every 24 hours. The t(½) of bumetanide in neonates ranges from 1.74 to 7.0 hours. Up to now, no data are available on the continuous infusion of bumetanide. Extracorporeal membrane oxygenation (ECMO) is used for a variety of indications including sepsis, persistent pulmonary hypertension, meconium aspiration syndrome, cardiac defects and congenital diaphragmatic hernia. There are two studies of furosemide in neonates undergoing ECMO and only one on the pharmacokinetics of bumetanide under ECMO. When ECMO was conducted for 72 hours, the total amount of furosemide administered was 7.0 mg/kg, and the urine production in the 3 days of treatment was about 6 mL/kg/h, which is the target value. The t(½) of bumetanide in neonates during ECMO was extremely variable. CL, t(½), and V(d) were 0.63 mL/min/kg, 13.2 hours, and 0.45 L/kg, respectively. Furosemide may be administered by inhalation and inhibits the bronco-constrictive effect of exercise, cold air ventilation and antigen challenge. However, inhaled furosemide is not active in infants with viral bronchiolitis and its effect on broncho-pulmonary dysplasia is still uncertain. Furosemide does not significantly increase the risk of failure of patent ductus arteriosus closure when indomethacin or ibuprofen have been co-administered. Infants with low birth weight treated long-term with furosemide are at risk for the development of intra-renal calcification. Furosemide therapy above 10 mg/kg bodyweight cumulative dose had a 48-fold increased risk of nephrocalcinosis. The use of furosemide in combination with indomethacin increased the incidence of acute renal failure. The maturation of the kidney governs the pharmacokinetics of furosemide and bumetanide in the infant. CL and t(½) are influenced by development, and this must be taken into consideration when planning a dosage regimen with these drugs.

Pediatric cardiovascular drug dosing in critically ill children and extracorporeal membrane oxygenation

Cardiovascular disease in children is common and results in significant morbidity and mortality. The sickest children with cardiovascular disease may require support with extracorporeal membrane oxygenation (ECMO), which provides life-saving assistance for children with refractory cardiorespiratory failure. Many classes of cardiovascular drugs are used in children, but very few of these agents have been well studied in children. The knowledge gap is even more pronounced in children supported by ECMO. Pharmacokinetic (PK) data collected to date (primarily from antibiotics and sedatives) suggest that the ECMO circuit has the potential to significantly alter the PK of drugs including changes in clearance and volume of distribution. Of all cardiovascular drugs administered to children supported by ECMO, only 11 have been partially studied and reported in the medical literature. Esmolol, amiodarone, nesiritide, bumetanide, sildenafil, and prostaglandin E1 seem to require dosing modifications in children supported by ECMO, whereas it seems that hydralazine, nicardipine, furosemide, epinephrine, and dopamine can be dosed similarly to children not supported by ECMO. However, trials evaluating the PK of these drugs in patients supported by ECMO are extremely limited (ie, case reports), and therefore, definitive dosing recommendations are not plausible. Research efforts should focus on evaluating the PK of drugs in patients on ECMO to avoid therapeutic failures or unnecessary toxicities.

High-dose fenoldopam reduces postoperative neutrophil gelatinase-associated lipocaline and cystatin C levels in pediatric cardiac surgery

INTRODUCTION

The aim of the study was to evaluate the effects of high-dose fenoldopam, a selective dopamine-1 receptor, on renal function and organ perfusion during cardiopulmonary bypass (CPB) in infants with congenital heart disease (CHD).

METHODS

A prospective single-center randomized double-blind controlled trial was conducted in a pediatric cardiac surgery department. We randomized infants younger than 1 year with CHD and biventricular anatomy (with exclusion of isolated ventricular and atrial septal defect) to receive blindly a continuous infusion of fenoldopam at 1 μg/kg/min or placebo during CPB. Perioperative urinary and plasma levels of neutrophil gelatinase-associated lipocaline (NGAL), cystatin C (CysC), and creatinine were measured to assess renal injury after CPB.

RESULTS

We enrolled 80 patients: 40 received fenoldopam (group F) during CPB, and 40 received placebo (group P). A significant increase of urinary NGAL and CysC levels from baseline to intensive care unit (ICU) admission followed by restoration of normal values after 12 hours was observed in both groups. However, urinary NGAL and CysC values were significantly reduced at the end of surgery and 12 hours after ICU admission (uNGAL only) in group F compared with group P (P = 0.025 and 0.039, respectively). Plasma NGAL and CysC tended to increase from baseline to ICU admission in both groups, but they were not significantly different between the two groups. No differences were observed on urinary and plasma creatinine levels and on urine output between the two groups. Acute kidney injury (AKI) incidence in the postoperative period, as indicated by pRIFLE classification (pediatric score indicating Risk, Injury, Failure, Loss of function, and End-stage kidney disease level of renal damage) was 50% in group F and 72% in group P (P = 0.08; odds ratio (OR), 0.38; 95% confidence interval (CI), 0.14 to 1.02). A significant reduction in diuretics (furosemide) and vasodilators (phentolamine) administration was observed in group F (P = 0.0085; OR, 0.22; 95% CI, 0.07 to 0.7).

CONCLUSIONS

The treatment with high-dose fenoldopam during CPB in pediatric patients undergoing cardiac surgery for CHD with biventricular anatomy significantly decreased urinary levels of NGAL and CysC and reduced the use of diuretics and vasodilators during CPB.

TRIAL REGISTRATION

Clinical Trial.Gov NCT00982527.

Acute kidney injury in an infant after cardiopulmonary bypass

The infant who develops acute kidney injury (AKI) after cardiopulmonary bypass (CPB) surgery presents unique challenges and opportunities to the clinician and to the investigator interested in the study of AKI pathophysiology. Infants do not have many of the comorbid conditions that confound CPB outcome studies of adults. Because the timing of the AKI event is known in this clinical setting, collaboration between cardiology intensivists, nephrologists, and perfusion technologists is essential to minimize the impact of CPB on the kidney. Early institution of ultrafiltration in the operating room and renal replacement therapy in the postoperative period may decrease the proinflammatory milieu and its resultant systemic effects. In addition, early initiation of renal replacement therapy to prevent fluid overload may result in improved infant outcomes.

An exploratory study with an adaptive continuous intravenous furosemide regimen in neonates treated with extracorporeal membrane oxygenation

INTRODUCTION

The objective of the present study was to explore a continuous intravenous furosemide regimen that adapts to urine output in neonates treated with extracorporeal membrane oxygenation (ECMO).

METHODS

Seven neonates admitted to a paediatric surgical intensive care unit for ECMO therapy were treated with a furosemide regimen consisting of a loading bolus (1-2 mg/kg) followed by a continuous infusion at 0.2 mg/kg per hour, which was adjusted according to the target urine production of 6 ml/kg per hour. Therapeutic drug monitoring for furosemide concentrations in blood was performed.

RESULTS

The mean +/- standard deviation furosemide dose was 0.17 +/- 0.06 mg/kg per hour, 0.08 +/- 0.04 mg/kg per hour and 0.12 +/- 0.07 mg/kg per hour, respectively, on the first day, second day and third day of the study. The median (range of the urine production of the study subjects) urine production over the consecutive study days was 6.8 (0.8-8.4) mg/kg per hour, 6.0 (4.7-8.9) mg/kg per hour and 5.4 (3.4-10.1) ml/kg per hour. The target urine production was reached after a median time of 7 (3-37) hours. The regimen was haemodynamically well tolerated and the median furosemide serum concentration was 3.1 (0.4-12.9) mug/ml, well below the toxic level.

CONCLUSION

The evaluated furosemide infusion appears an effective means to reduce volume overload in neonates treated with ECMO. The data of this preliminary study suggest that the starting dose of furosemide was too high, however, because the urine output was excessive and required frequent adaptations. The results of this study therefore indicate that a novel pharmacokinetic/pharmacodynamic model needs to be developed for neonates treated with ECMO.

Absence of tolerance and toxicity to high-dose continuous intravenous furosemide in haemodynamically unstable infants after cardiac surgery

AIM

To evaluate a high-dose continuous furosemide regimen in infants after cardiac surgery.

METHODS

Fifteen haemodynamically unstable infants with volume overload admitted to a paediatric intensive care unit were treated with an aggressive furosemide regimen consisting of a loading bolus (1-2 mg kg(-1)) followed by a continuous infusion at 0.2 mg kg(-1) h(-1) which was adjusted according to a target urine output of 4 ml kg(-1) h(-1). Frequent sampling for furosemide concentrations in blood and urine was done for 3 days with simultaneous assessment of sodium excretion and urine output.

RESULTS

The mean furosemide dose was 0.22 (+/- 0.06), 0.25 (+/- 0.10) and 0.22 (+/- 0.11) mg kg(-1) h(-1) on the first, second and third day, respectively. Median urine production was 3.0 (0.6-5.3), 4.2 (1.7-6.6) and 3.9 (2.0-8.5) ml kg(-1) h(-1), respectively, on the first, second and third day of the study. The target urine production was reached at a median time of 24 (6-60) h and this was maintained during the study period. The regimen did not result in toxic serum concentrations and was haemodynamically well tolerated.

CONCLUSION

High-dose continuous furosemide infusion for 72 h in haemodynamically unstable infants after cardiac surgery appears to be a safe and effective treatment for volume overload. Development of tolerance against the effects of furosemide and ototoxic furosemide concentrations were not observed.

Evaluation of furosemide regimens in neonates treated with extracorporeal membrane oxygenation

Introduction

Loop diuretics are the most frequently used diuretics in patients treated with extracorporeal membrane oxygenation (ECMO). In patients after cardiopulmonary bypass (CPB) surgery, the use of continuous furosemide infusion is increasingly documented. Because ECMO and CPB are 'comparable' procedures, continuous furosemide infusion is used in newborns on ECMO. We report on the use of continuous intravenous furosemide in neonates treated with ECMO.

Methods

This was a retrospective observational study in neonates treated with continuous intravenous furosemide during ECMO.

Results

Thirty-one patients were included in the study. A median of 25 (9–149) hours after the start of ECMO, continuous furosemide therapy was started at a median rate of 0.08 (0.02–0.17) mg/kg per hour. The continuous furosemide dose was not changed in the individual patient. Seven patients received a furosemide bolus prior to, and five patients received additional loop diuretics during, the continuous infusion. Urine production before continuous furosemide therapy was not significantly different between patients who received a furosemide bolus prior to the infusion and those who did not receive this bolus (P = 0.2879). Although a positive effect of the 'loading' bolus was observed in urine output in the first 24 hours, there was no statistically significant difference in urine output (P = 0.0961) or in time (P = 0.1976) to reach a urine output of 6 ml/kg per hour between patients. After 24 hours, urine production remained a median of 6.2 ml/kg per hour irrespective of furosemide boluses. The forced diuresis was well tolerated as illustrated by stable haemodynamic parameters and a decrease in ECMO flow and vasopressor score over the observation period.

Conclusion

This is the first report on continuous intravenous furosemide therapy in newborns treated with ECMO. The furosemide regimens used in this study varied widely in continuous and intermittent doses. However, all regimens achieved adequate urine output. An advantage of continuous, over intermittent, intravenous furosemide could not be documented. Furosemide dosing regimens should be developed for neonates treated with ECMO. In addition, therapeutic drug-monitoring studies are required to prevent furosemide toxicity because so far no data are available on serum furosemide levels in neonates treated with ECMO.

Diuretics in pediatrics : current knowledge and future prospects

This review summarizes current knowledge on the pharmacology, pharmacokinetics, pharmacodynamics, and clinical application of the most commonly used diuretics in children. Diuretics are frequently prescribed drugs in children. Their main indication is to reduce fluid overload in acute and chronic disease states such as congestive heart failure and renal failure. As with most drugs used in children, optimal dosing schedules are largely unknown and empirical. This is undesirable as it can potentially result in either under- or over-treatment with the possibility of unwanted effects. The pharmacokinetics of diuretics vary in the different pediatric age groups as well as in different disease states. To exert their action, all diuretics, except spironolactone, have to reach the tubular lumen by glomerular filtration and/or proximal tubular secretion. Therefore, renal maturation and function influence drug delivery and consequently pharmacodynamics. Currently advised doses for diuretics are largely based on adult pharmacokinetic and pharmacodynamic studies. Therefore, additional pharmacokinetic and pharmacodynamic studies for the different pediatric age groups are necessary to develop dosing regimens based on pharmacokinetic and pharmacodynamic models for all routes of administration.

Critical care in cardiovascular medicine

The field of cardiac intensive care is rapidly evolving with nearly simultaneous advances in surgical techniques and adjunctive therapies, respiratory care, intensive care technology and monitoring, pharmacologic research and development, and computing and electronics. The focus of care has now shifted toward reducing morbidity and improving "quality of life" while the survival of infants and children with congenital heart defects, including those with univentricular hearts has dramatically improved during the last three decades. Despite these advances, there remains a predictable fall in cardiac output after cardiopulmonary bypass. This article focuses on early identification and aggressive treatment of the low cardiac output syndrome peculiar to these patients. The authors also briefly review the recent advances in the treatment of pulmonary hypertension, mechanical support, and neurologic surveillance after cardiac surgery.

Intermittent Bolus Injection versus Continuous Infusion of Furosemide in Normal Adult Greyhound Dogs

Several studies in human subjects have demonstrated greater diuresis with constant rate infusion (CRI) furosemide than intermittent bolus (IB) furosemide. This study was conducted to compare the diuretic efficacy of the same total dose of IB furosemide and CRI furosemide in 6 healthy, adult Greyhound dogs in a randomized crossover design with a 2-week washout period between treatments. For IB administration, dogs received 3 mg/kg at 0 and 4 hours. For CRI administration, dogs received a 0.66 mg/kg loading dose followed by 0.66 mg/kg/h over 8 hours. The same volume of fluid was administered for both methods. Urine output was quantified hourly. Urine electrolyte concentrations, urine specific gravity (USG), packed cell volume (PCV), total protein (TP), serum electrolyte concentrations, total carbon dioxide (TCO2), serum creatinine (sCr), and blood urea nitrogen (BUN) were determined every 2 hours. Urine production and water intake were greater (P < or = 0.05) for CRI than IB. Urine sodium and calcium losses were greater (P < 0.05) and urine potassium loss was less (P = 0.03) for CRI than IB, but there was no evidence of a difference between methods for urine magnesium and chloride losses. Serum chloride concentration was less (P < 0.001), sCr concentration greater (P = 0.04). TP greater (P = 0.01), and PCV greater (P = 0.003) for CRI than IB. No differences in USG, TCO2, BUN, or serum potassium, sodium, and magnesium concentrations were detected between methods. The same total dose of CRI furosemide resulted in more diuresis, natriuresis, and calciuresis and less kaliuresis than IB furosemide in these normal Greyhound dogs over 8 hours, suggesting that furosemide is a more effective diuretic when administered by CRI than by IB.

Serum creatinine and estimated creatinine clearance do not predict perioperatively measured creatinine clearance in neonates undergoing congenital heart surgery

OBJECTIVE

To describe changes in creatinine clearance (CrCl) in a small group of neonates who underwent surgery for repair of transposition of the great arteries or palliation of hypoplastic left heart syndrome. To determine whether serum creatinine, urine output, or the Schwartz formula accurately predict measured CrCl in these patients.

DESIGN

Prospective, randomized controlled trial with subsequent extraction of information regarding renal function from the database.

SETTING

A 14-bed pediatric intensive care unit in a children's hospital.

PATIENTS

A total of 14 neonates (hypoplastic left heart syndrome, 6; transposition of the great arteries, 8).

MEASUREMENTS

Demographic information, urine output, serum creatinine, and 24-hr CrCl preoperatively and postoperatively on days 1 and 2.

MAIN RESULTS

Weight, age, and body surface area were 3.3 +/- 0.6 kg, 8.2 +/- 6.9 days, and 0.2 +/- 0.02 m2, respectively. Urine output increased from 1.8 +/- 0.5 mL x kg(-1) x hr(-1) preoperatively to 2.4 +/- 0.8 mL x kg(-1) x hr(-1) on postoperative day 1 (p = .02) and 2.8 +/- 1.1 mL x kg(-1) x hr(-1) on postoperative day 2 (p = .007). Serum creatinine changed from 0.64 +/- 0.15 mg/dL preoperatively to 0.72 +/- 0.40 mg/dL on postoperative day 1 (p = .4, not significant) to 0.78 +/- 0.41 mg/dL on postoperative day 2 (p = .17, not significant). Measured CrCl changed from 22.8 +/- 9.4 mL x min(-1) x 1.73 m(-2) preoperatively to 25.1 +/- 31 mL x min(-1) x 1.73 m(-2) on postoperative day 1 (p = .77, not significant) and 24.9 +/- 19.9 on postoperative day 2 (p = .69, not significant). No difference in measured CrCl was noted based on hypoplastic left heart syndrome vs. transposition of the great arteries. Median overestimation of CrCl by the Schwartz equation was 58% preoperatively, 78% on postoperative day 1, and 53% on postoperative day 2. Clinically significant correlations were not noted between measured CrCl and serum creatinine or urine production preoperatively, on postoperative day 1, or on postoperative day 2. Bland-Altman plot demonstrated that the Schwartz equation was a biased and imprecise estimate of CrCl at all three time points.

CONCLUSIONS

Perioperative CrCl is unpredictable in neonates with transposition of the great arteries and hypoplastic left heart syndrome. Serum creatinine, urine output, and the Schwartz formula do not accurately predict CrCl. Reliance on estimates of CrCl could result in toxic concentrations of drugs eliminated by the kidneys.