Serum digoxin concentrations in the human fetus, neonate and infant

Principles of Pharmacokinetics in the Pregnant Woman and Fetus

Pregnancy profoundly alters a woman's physiology. These changes alter drug absorption, distribution, metabolism, and elimination and emphasize the pharmacologic complexity of pregnancy. They also emphasize the dangers of extrapolating pharmacologic expectations from nonpregnant populations to pregnant women and their fetuses. Although concerns about fetal safety have historically limited pharmacokinetic studies during pregnancy, it is important to recognize that many medications are clinically indicated for various maternal or fetal conditions, and it is particularly important that these therapies be evidence-based with appropriate study, including short-term and long-term outcomes data.

Role of endogenous digitalis-like factors in the clinical manifestations of severe preeclampsia: a sytematic review

Endogenous digitalis-like factor(s), originally proposed as a vasoconstrictor natriuretic hormone, was discovered in fetal and neonatal blood accidentally because it cross-reacts with antidigoxin antibodies (ADAs). Early studies using immunoassays with ADA identified the digoxin-like immuno-reactive factor(s) (EDLF) in maternal blood as well, and suggested it originated in the feto-placental unit. Mammalian digoxin-like factors have recently been identified as at least two classes of steroid compounds, plant derived ouabain (O), and several toad derived bufodienolides, most prominent being marinobufagenin (MBG). A synthetic pathway for MBG has been identified in mammalian placental tissue. Elevated maternal and fetal EDLF, O and MBG have been demonstrated in preeclampsia (PE), and inhibition of red cell membrane sodium, potassium ATPase (Na, K ATPase (NKA)) by EDLF is reversed by ADA fragments (ADA-FAB). Accordingly, maternal administration of a commercial ADA-antibody fragment (FAB) was tested in several anecdotal cases of PE, and two, small randomized, prospective, double-blind clinical trials. In the first randomized trial, ADA-FAB was administered post-partum, in the second antepartum. In the post-partum trial, ADA-FAB reduced use of antihypertensive drugs. In the second trial, there was no effect of ADA-FAB on blood pressure, but the fall in maternal creatinine clearance (CrCl) was prevented. In a secondary analysis using the pre-treatment maternal level of circulating Na, K ATPase (NKA) inhibitory activity (NKAI), ADA-FAB reduced the incidence of pulmonary edema and, unexpectedly, that of severe neonatal intraventricular hemorrhage (IVH). The fall in CrCl in patients given placebo was proportional to the circulating level of NKAI. The implications of these findings on the pathophysiology of the clinical manifestations PE are discussed, and a new model of the respective roles of placenta derived anti-angiogenic (AAG) factors (AAGFs) and EDLF is proposed.

Pregnancy-related pharmacokinetic changes

The pharmacokinetics of many drugs are altered by pregnancy. Drug distribution and protein binding are changed by pregnancy. While some drug metabolizing enzymes have an apparent increase in activity, others have an apparent decrease in activity. Not only is drug metabolism affected by pregnancy, but renal filtration is also increased. In addition, pregnancy alters the apparent activities of multiple drug transporters resulting in changes in the net renal secretion of drugs.

Antiarrhythmic drugs in pregnancy

The risk of arrhythmia development or recurrence is increased during pregnancy. For those arrhythmias that are unresponsive to conservative therapy, such as vagal maneuvers or life style interventions, or that present a higher risk to the mother or fetus, medical therapy may be necessary. In each case, the patient and provider must carefully consider the risks and benefits of a particular therapy. This requires an understanding of the data regarding the safety and efficacy of any particular drug, which in some cases may be extensive and in others quite limited. Fortunately, options exist for the treatment of arrhythmias during pregnancy.

The pediatric cardiology pharmacopeia: 2013 update

The use of medications plays a pivotal role in the management of children with heart diseases. Most children with increased pulmonary blood flow require chronic use of anticongestive heart failure medications until more definitive interventional or surgical procedures are performed. The use of such medications, particularly inotropic agents and diuretics, is even more amplified during the postoperative period. Currently, children are undergoing surgical intervention at an ever younger age with excellent results aided by advanced anesthetic and postoperative care. The most significant of these advanced measures includes invasive and noninvasive monitoring as well as a wide array of pharmacologic agents. This review update provides a medication guide for medical practitioners involved in care of children with heart diseases.

Maternal cardiac arrhythmias during pregnancy and lactation

Arrhythmias occurring during pregnancy can cause significant symptoms and even death in mother and fetus. The management of these arrhythmias is complicated by the need to avoid harm to the fetus and neonate. It is useful to classify patients with arrhythmias into those with and without structural heart disease. Those with a primary electrical problem, but an otherwise normal heart, often tolerate rapid heart rates without compromise whereas patients with problems such as rheumatic heart disease, congenital heart disease or cardiomyopathy may quickly decompensate during an arrhythmia.

Mammary excretion of digoxin in goats

The binding of digoxin to proteins in plasma and milk was about 20% lower after the addition of the drug to plasma and milk (in vitro) than its binding in plasma and milk from animals administered digoxin parenterally. The mammary excretion of digoxin was examined in the experiments on goats. The concentration of non-protein-bound digoxin in milk was slightly lower than the concentration of non-protein-bound in plasma suggesting a passive diffusion. The amount of digoxin excreted with the milk per day should be far below the dose usually recommended for a newborn child.

The challenge of fetal dysrhythmias: echocardiographic diagnosis and clinical management

OBJECTIVE

The present study aimed to evaluate the management of fetal cardiac dysrhythmias based on prior identification of the underlying electrophysiological mechanism.

METHODS

We studied 36 consecutive fetuses with cardiac dysrhythmia. Rhythm diagnosis was based on M-mode, pulsed wave Doppler and tissue Doppler imaging (TDI). Only fetuses with: (i) incessant tachycardia (> 12 h) and mean ventricular rate > 200 beats/min, (ii) signs of left ventricular dysfunction, or (iii) hydrops, were treated using oral maternal drug therapy.

RESULTS

The mean gestational age at diagnosis was 24.3 +/- 4.5 weeks. Twenty-one fetuses had tachycardia with a 1: 1 atrial-ventricular (AV) conduction. Based on ventricular-atrial interval, prenatal diagnosis was: permanent junctional reciprocating (n = 6), atrial ectopic (n = 6) or atrial-ventricular re-entry tachycardia (n = 9). One had atrial flutter, one ventricular tachycardia and four congenital AV block. Nine showed premature atrial or ventricular beats. Fifteen fetuses with incessant tachycardia, left ventricular dysfunction or hydrops were prenatally treated with maternal administration of digoxin, sotalol or flecainide. The total success rate (sinus rhythm or rate control) was 14/15 (93%). Seven fetuses were hydropics. Three of these died (one at 28 weeks of gestation, two in the first week of life). The prenatal diagnosis of dysrhythmia was confirmed at the birth in 31 of 35 live-born. No misdiagnosis was made using TDI. At 3 +/- 1.1-year follow-up, 33/35 children were alive and well.

CONCLUSIONS

Fetal echocardiography could clarify the electrophysiological mechanism of fetal cardiac dysrhythmias and guide the therapy.

Cardiovascular pharmacotherapeutic considerations during pregnancy and lactation

Cardiovascular drugs are often used in pregnancy for the treatment of maternal and fetal conditions. Mothers could also require continued postpartum drug therapy. Most cardiovascular drugs taken by pregnant women can cross the placenta and therefore expose the developing embryo and fetus to their pharmacologic and teratogenic effects. These effects are influenced by the intrinsic pharmacokinetic properties of a given drug as well as by the complex physiological changes occurring during pregnancy. Many drugs are also transferred into human milk and therefore can potentially have adverse effects on the nursing infant. This 2-part article summarizes some of the available literature concerning the risks and benefits of using various cardiovascular drugs and drug classes during pregnancy and lactation. Included in the discussion are cardiac glycosides, antiarrhythmic drugs, drugs used to treat both acute and chronic hypertension, cholesterol-lowering agents, anticoagulants, thrombolytics, and antiplatelet drugs.

Cardiac arrhythmias in the human fetus

Fetal cardiac arrhythmias have been recognized with increasing frequency during the past several years. Most fetal arrythmias are intermittent extrasystoles, often presenting as irregular pauses of rhythm. These are significant only when they occur with appropriate timing to initiate sustained tachycardia, mediated by anatomic bypass pathways. The most common important fetal arrhythmias are: 1) supraventricular tachycardias, and 2) severe bradyarrhythmias, associated with complete heart block. Symptomatic fetal tachycardias are usually supraventricular in origin, and may be associated with the developmet of hydrops fetalis. These patients may respond to antiarrhythmic drug therapy, administered via maternal ingestion or via direct fetal injection. Such therapy should be offered with careful fetal and maternal monitoring, and must be based on a logical, sequential analysis of the electrical mechanism underlying the arrhythmia, and an appreciation of the pharmacology and pharmacokinetics of the maternal, placental fetal system. Bradycardia from complete heart block may either be associated with complex congential heart malformations involving the atrioventricular junction of the heart, or may present in fetuses with normal cardiac structure, in mothers with autoimmune conditions associated with high titres of anti-SS-A or anti-SS-B antibody, which cross the placenta to cause immune-related inflammatory damage to the fetal atroventricular node. This paper reviews experience with the analysis of fetal caridac rhythm, a detailed discussion of the pathophysiology of arrhythmias and their effect on the fetal circulatory system, and offers a logical framework for the construction of treatment algorithms for fetuses at risk for circulatory compromise from fetal arrhythmias.

Endogenous glycosides in critically ill patients

OBJECTIVE

To determine the incidence of critically ill patients displaying endogenous digitalis-like-immunoreactive substances (DLIS) and to examine the relationship of these hormones to routine laboratory variables, the underlying disease, myocardial function, hemodynamic status, severity of illness, systemic inflammation, and mortality rate.

DESIGN

Sera of 401 consecutive critically ill patients, not treated with cardiac glycosides, were analyzed for DLIS (digitoxin and digoxin, TDx; Abbott Diagnostics, North Chicago, IL) and endogenous ouabain. Normal values of endogenous ouabain were determined in 62 healthy volunteers. We measured pro- and anti-inflammatory mediators (L-selectin, tumor necrosis factor-alpha, interleukin-1beta, interleukin-2, interleukin-6, interleukin-10), C-reactive protein, and serum amyloid A protein as well as patients' Acute Physiology and Chronic Health Evaluation II and Goris scores. In a subgroup of patients with a pulmonary artery catheter (n = 95), we determined cardiac output, pulmonary artery occlusion pressure, systemic and pulmonary vascular resistance, left ventricular stroke volume, and right and left stroke work.

SETTING

Two surgical intensive care units of an university hospital.

SUBJECTS

Sera of 401 consecutive critically ill patients.

INTERVENTIONS

Blood sampling.

MEASUREMENTS AND MAIN RESULTS

Of the 401 patients tested, 343 had nonmeasurable DLIS concentrations (DLIS-negative), and 58 (14.5%) had positive digoxin (n = 18) or digitoxin (n = 34) concentrations (DLIS-positive) or were positive in both tests (n = 6). Mean endogenous ouabain concentrations were nine-fold increased in DLIS-positive (3.59 +/- 1.43 nmol/L) and three-fold increased in DLIS-negative (1.34 +/-.81 nmol/L) patients compared with controls (0.38 +/- 0.31 nmol/L). DLIS and ouabain concentrations closely correlated with the Acute Physiology and Chronic Health Evaluation II and Goris score and were associated with increased concentrations of transaminases, bilirubin, aldosterone, cortisol, serum creatinine, fractional sodium excretion, proinflammatory mediators, C-reactive protein, and serum amyloid A (p <or=.009). The hospital mortality rates of DLIS-positive and DLIS-negative patients were 12% and 3.2%, respectively, and for patients with ouabain concentrations above and below 2 nmol/L 38.6% and 0.6%, respectively. In DLIS-positive patients with pulmonary artery catheter (n = 23), cardiac output, stroke volume, and left ventricular stroke work were decreased, and pulmonary artery occlusion pressure and central venous pressure were increased (p <or=.009).

CONCLUSIONS

Different types of endogenous glycosides including endogenous ouabain are elevated in a significant proportion of critically ill patients. The occurrence of these substances is associated with increased morbidity and hospital mortality rates, possibly due to systemic inflammatory processes. DLIS but not endogenous ouabain concentrations were found to be related to left ventricular function.

Drug treatment of fetal tachycardias

The pharmacological treatment of fetal tachycardia (FT) has been described in various publications. We present a study reviewing the necessity for treatment of FT, the regimens of drugs used in the last two decades and their mode of administration. The absence of reliable predictors of fetal hydrops (FH) has led most centers to initiate treatment as soon as the diagnosis of FT has been established, although a small minority advocate nonintervention. As the primary form of pharmacological intervention, oral maternal transplacental therapy is generally preferred. Digoxin is the most common drug used to treat FT; however, effectiveness remains a point of discussion. After digoxin, sotalol seems to be the most promising agent, specifically in atrial flutter and nonhydropic supraventricular tachycardia (SVT). Flecainide is a very effective drug in the treatment of fetal SVT, although concerns about possible pro-arrhythmic effects have limited its use. Amiodarone has been described favorably, but is frequently excluded due to its poor tolerability. Verapamil is contraindicated as it may increase mortality. Conclusions on other less frequently used drugs cannot be drawn. In severely hydropic fetuses and/or therapy-resistant FT, direct fetal therapy is sometimes initiated. To minimize the number of invasive procedures, fetal intramuscular or intraperitoneal injections that provide a more sustained release are preferred. Based on these data we propose a drug protocol of sotalol 160 mg twice daily orally, increased to a maximum of 480 mg daily. Whenever sinus rhythm is not achieved, the addition of digoxin 0.25 mg three times daily is recommended, increased to a maximum of 0.5 mg three times daily. Only in SVT complicated by FH, either maternal digoxin 1 to 2mg IV in 24 hours, and subsequently 0.5 to 1 mg/day IV, or flecainide 200 to 400 mg/day orally is proposed. Initiating direct fetal therapy may follow failure of transplacental therapy.

Transplacental treatment of fetal tachycardia: implications of drug transporting proteins in placenta

Sustained fetal tachyarrhythmia (> 180 bpm) is a potentially life-threatening condition for the unborn. Digoxin is commonly used as an initial monotherapy. Flecainide, sotalol, and verapamil are also used as a monotherapy or a combination therapy with digoxin. The treatment success rate with digoxin is about 50%. Presence of hydrops is associated with poor placental transfer of digoxin. Although transplacental pharmacotherapy has been available, it is a challenging task to maximize fetal drug exposure, while minimizing drug exposure of the mother. In addition, clear evidence behind drug of choice and treatment algorithm is lacking. Whereas prospective clinical studies with rigorous design remain to be seen, our knowledge on placental drug transport at a molecular level has been steadily increasing. For example, an ATP-dependent membrane protein, known as P-glycoprotein, is expressed in placenta, decreasing fetal exposure to maternal digoxin. Pharmacological manipulation of drug transporters may open a door to ultimate optimization of the transplacental pharmacotherapy.

Antiarrhythmic drugs in pregnancy

During pregnancy a number of rhythm disturbances can occur in both the mother and fetus; these may range from benign ectopy to life-threatening arrhythmias. With a clear understanding of the maternal hemodynamic changes associated with pregnancy, and the appropriate antiarrhythmic therapies available, almost all such cases can be treated successfully. Although no drug is completely safe, most are well tolerated and can be given with relatively low risk. Drug therapy should be avoided during the first trimester of pregnancy if possible and drugs with the longest record of safety should be used as first-line therapy. Conservative therapies should be used when appropriate. Several drug options exist for most maternal and fetal arrhythmias.

Pharmacokinetic changes during pregnancy and their clinical relevance

The dynamic physiological changes that occur in the maternal-placental-fetal unit during pregnancy influence the pharmacokinetic processes of drug absorption, distribution and elimination. Pregnancy-induced maternal physiological changes may affect gastrointestinal function and hence drug absorption rates. Ventilatory changes may influence the pulmonary absorption of inhaled drugs. As the glomerular filtration rate usually increases during pregnancy, renal drug elimination is generally enhanced, whereas hepatic drug metabolism may increase, decrease or remain unchanged. A mean increase of 8 L in total body water alters drug distribution and results in decreased peak serum concentrations of many drugs. Decreased steady-state concentrations have been documented for many agents as a result of their increased clearance. Pregnancy-related hypoalbuminaemia, leading to decreased protein binding, results in increased free drug fraction. However, as more free drug is available for either hepatic biotransformation or renal excretion, the overall effect is an unaltered free drug concentration. Since the free drug concentration is responsible for drug effects, the above mentioned changes are probably of no clinical relevance. The placental and fetal capacity to metabolise drugs together with physiological factors, such as differences acid-base equilibrium of the mother versus the fetus, determine the fetal exposure to the drugs taken by the mother. As most drugs are excreted into the milk by passive diffusion, the drug concentration in milk is directly proportional to the corresponding concentration in maternal plasma. The milk to plasma (M:P) ratio, which compares milk with maternal plasma drug concentrations, serves as an index of the extent of drug excretion in the milk. For most drugs the amount ingested by the infant rarely attains therapeutic levels.

[Arrhythmias and pregnancy]

Although arrhythmias are one of the most frequent consultations during pregnancy, fortunately the majority are benign. Usually, they are well tolerated assuming they occur in patients with structurally normal hearts. However, pregnancy adds a new aspect to the so called "arrhythmia tolerance", because arrhythmia and therapy may jeopardize the fetus. For acute treatment of narrow and wide tachycardias, with few exceptions, antiarrhythmic medications appear to be safe. In addition to the relative security of drugs such as adenosine, digoxin, propranolol, procainamide and flecainide, we could use direct current countershock with no evidence of significant complications. Because no drug is absolutely safe, chronic pharmacologic therapy is best avoided during pregnancy. Finally, radiofrequency ablation could be recommended as an alternative in women with previous tachycardias who would like to become pregnant.

Diffusion characteristics of placental preparations affect the digoxin passage across the isolated placental lobule

Our aim was to evaluate the isolated placental lobule to study maternofetal transplacental digoxin transfer and accumulation in placental tissue in vitro. Digoxin passage across the isolated lobule of 10 human placentas was calculated from repeated fetal and maternal perfusate samples, and placental tissue digoxin concentrations were measured at the end of the experiments. To determine the degree of overlap of the fetal and the maternal circulation, the antipyrine clearance was used. Digoxin disappearance from the maternal circuit was not significantly affected by the degree of overlap. In contrast, the increase of digoxin in the fetal compartment was significantly higher in "well-perfused" placentas (antipyrine clearance > 1.60 ml/min; n = 5) than in "malperfused" placentas (antipyrine clearance < 1.50 ml/min; n = 5) (end-feto to initial maternal digoxin ratio 0.44 +/- 0.08 vs. 0.30 +/- 0.08; p < 0.05), whilst the accumulation in placental tissue was higher in the latter group (0.45 +/- 0.07 vs. 0.62 +/- 0.10 ng/mg protein; p < 0.05). We conclude that the isolated placental lobule is suitable to quantify transplacental digoxin transfer in vitro, but the diffusion characteristics of each preparation have to be considered.

Atrial flutter in the human fetus: diagnosis, hemodynamic consequences, and therapy

In the context of a large program of prenatal echocardiographic detection of fetal heart disease, special attention was paid to the in utero detection and identification of fetal heart rate disorders. This article focuses on 18 cases of tachycardiac fetuses. It provides information on how to identify the nature of the detected tachycardia, the hemodynamic consequences of tachycardia, the particular characteristics of fetal atrial flutter, and the efficacy of the transmaternal treatment of fetal tachycardia. It also describes an original way to grade and score the degree of fetal heart failure that proved useful for the assessment and monitoring of in utero therapeutic procedures. The results presented stress the efficacy of digoxin for fetal atrial flutter as well as the usefulness of prenatal echocardiography in the assessment of anatomical, functional, and rhythmic conditions of the fetal heart.

Single daily dose of digoxin for maintenance therapy of infants and children with cardiac disease: is it reliable?

Between July 1990 and September 1991, 30 infants and children, most of whom had a congenital heart defect and who had been treated at least during the previous 20 days by two daily doses of digoxin and were in a stable clinical condition, were selected at random. A maintenance dose of digoxin was administered at 24-h intervals for 7 days in the study group (n = 15); no change was made in the 12-h dosage interval in the control group (n = 15). When the serum digoxin concentrations were compared, no significant difference was found between pre- and poststudy values in the study group (1.0 +/- 0.6 and 0.8 +/- 0.3 ng/ml, respectively) or between the control and study groups (0.9 +/- 0.6 and 0.8 +/- 0.3 ng/ml, respectively) in terms of trough serum digoxin concentrations. Although the peak serum concentrations in the study group were increased significantly (2.3 +/- 0.8 ng/ml) compared with prestudy peak levels (1.6 +/- 0.7 ng/ml, p < 0.05) and with the level in the control group (1.5 +/- 0.8 ng/ml, p < 0.05), a toxic concentration was not reached, and toxicity symptoms were not observed clinically. Blood pressure, heart rate, and liver size did not change significantly in any patient during the study.

Drug therapy of the fetus

The fetus has become an intended object of drug therapy administered through the mother with the successful prevention of hyaline membrane disease with glucocorticoids. Maternal drug treatment has now been undertaken for a variety of fetal problems, including arrhythmias, congestive heart failure, infections, and inborn errors of adrenal metabolism. Interestingly, this planned maternal drug exposure during pregnancy coincided with increasing concerns during the last two decades about inadvertent transplacental exposure of the fetus to licit and illicit drugs. Efforts to direct drug therapy to the fetus have pointed out important gaps in knowledge of the pharmacology of the maternal-placental-fetal-unit (MPFU), whereas other observations illustrated recognized principles of the pharmacology of the MPFU. Many of these principles fit the basic framework of pharmacokinetics: absorption, distribution, metabolism and excretion. Rapid changes in maternal-placental physiology and fetal development during gestation, however, lead to dramatic variations in these processes throughout pregnancy.

Clinical and pharmacologic study of fetal supraventricular tachyarrhythmias

The purpose of this study was to evaluate the efficacy of maternal digoxin administration in 16 cases of fetal supraventricular tachyarrhythmia diagnosed by fetal echocardiography; cardiac anatomy was normal in all cases. The retrospective analysis included nine mothers who received digoxin orally in most cases, with control of the arrhythmia in two fetuses. The addition of amiodarone (five cases) and propranolol (two cases) yielded two successes with amiodarone. The therapeutic regimen of digoxin was then modified on the basis of poor response to orally administered digoxin. In the prospective study, digoxin was administered intravenously to seven mothers according to a standard protocol; high doses (1 to 2 mg intravenously) were prescribed for the first 24 hours and intravenous digoxin therapy was maintained for at least 5 days, depending on the fetal response. Digoxin pharmacokinetic studies of four mothers showed an increased plasma clearance and reduced elimination half-life. Digoxin controlled the five supraventricular tachycardias (with hydrops in four cases). Maternal flecainide therapy restored sinus rhythm in two cases of atrial flutter. Our prospective study emphasizes the efficacy and safety for the fetus and the mother of intravenously administered digoxin as a first-choice drug in the treatment of supraventricular tachyarrhythmias. Flecainide may be a promising second-choice drug but requires further clinical investigation. Amiodarone and propranolol seem to be ineffective.

Anesthesia, cardiopulmonary bypass, and the pregnant patient

For the perioperative management of pregnant patients with severe cardiac or aortic disease who require a cardiac surgical procedure and cardiopulmonary bypass, a close, cohesive, working relationship must exist among several medical and surgical specialties. For appropriate management, the well-being of both the mother and the fetus must be considered. The best interests of the mother and the fetus may not coincide, and optimal therapy for one may be inappropriate for the other. We present 10 cases of severe cardiac or aortic disease in pregnant women who required surgical intervention. Eight patients underwent cardiopulmonary bypass during pregnancy, and two patients had cesarean section performed immediately before cardiopulmonary bypass. We also discuss the pertinent pharmacologic aspects related to the perioperative period and the management of cardiopulmonary bypass for the pregnant patient.

Transplacental passage of digoxin in severe Rhesus immunization

Maternal and umbilical vein digoxin concentrations were determined in 16 mothers and fetuses with severe Rhesus-D disease, eight with, and eight without prior digitalization of the mother, when umbilical cord puncture was performed for diagnosis and intrauterine blood transfusion. In the eight patients without digoxin treatment, the digoxin concentrations in both the mother and the umbilical vein were below the limit of detection (less than 0.3 nmol/l). In the other eight patients digitalization of the mother was started 24-48 hours before the first umbilical cord puncture. The maternal and umbilical vein digoxin concentrations were determined on 26 occasions. Except for two instances, digoxin concentrations in the umbilical vein were always below 1 nmol/l. The mean ratio of maternal to fetal digoxin concentrations before initial transfusion was 2.51 ( +/- ISD = 1.47) and before later transfusions 1.67 ( +/- ISD = 0.61). The differences in mean ratios between initial and later transfusions are not significant (p = 0.16). The mean ratio for the total group was 1.93 ( +/- ISD = 1.01). There was no correlation between the maternal to umbilical vein digoxin ratio and either gestational age or umbilical venous hematocrit. The results of our study indicate that the therapeutic effect of transplacental digitalization in severe Rhesus disease is questionable and that a multicentre randomized trial would be necessary to evaluate whether this treatment is of benefit.

Direct treatment of fetal supraventricular tachycardia after failed transplacental therapy

Digitalization by direct intramuscular injection of the fetus successfully controlled supraventricular tachycardia at 24 weeks' gestation after more traditional intensive trials of transplacental therapy with digoxin, verapamil, and procainamide, either separately or in combination, had failed. The fetal pharmacokinetics were calculated from fetal blood samples obtained by cordocentesis. No clear evidence of placental transfer of digoxin administered to the mother could be found despite a digoxin concentration in the mother that ranged from 1.8 to 2.6 ng/ml for 4 days. After direct fetal digitalization we calculated that the coefficient of elimination for digoxin from the fetus was 0.0463 h-1, and digoxin elimination half-life was 15.9 hours. The latter time span is substantially less than the 50-hour half-life previously reported in newborn infants with low birth weight. The fetal/maternal concentration ratio of procainamide was 0.914. However, maternal clearance of procainamide (9.7 ml/kg-1/min-1) was twice as long as the clearance reported for nonpregnant patients undergoing fast acetylation. We conclude first, that at least in the dose of this ill fetus, little digoxin administered to the mother crossed the placentae; and second, that while direct fetal therapy with digoxin is effective, the necessary frequent number of injections render this therapy impractical. Direct fetal digitalization should probably be reserved for the preterm fetus who has evidence of heart failure and has not responded to maternally administered therapy other than digoxin.

Insufficient transplacental digoxin transfer in severe hydrops fetalis

A case of severe nonimmune hydrops fetalis caused by supraventricular tachycardia is presented. Maternal treatment with digoxin and the subsequent addition of verapamil and propranolol failed to be effective. Simultaneous measurement of maternal serum and cord blood digoxin levels showed insufficient transplacental digoxin transfer. Other modalities of treatment are discussed.

Age-related digoxin effects in an intact canine model

The inotropic and electrophysiologic effects of digoxin were studied in anesthetized neonatal and adult dogs to test the hypothesis that digoxin had comparable effects in these groups. Recordings of the ECG and central arterial pressure were made starting at 5.75 hours after an intravenous injection of 50 micrograms/kg of the drug. Parameters measured were heart rate (HR); PR interval; mean, systolic, and diastolic blood pressure; preejection period (PEP); and ejection time (ET). Two indices of systolic function were calculated, the systolic time interval (STI = PEP/ET) and total electromechanical systole (TMS = PEP + ET), which was indexed for HR. There was no significant difference from control animals in either the adult or neonatal groups in the PR interval or blood pressure. In the neonatal dogs, HR and STI were also not significantly different from control. However, in the neonatal dogs, there was a significant decrease in the indexed TMS, 288 +/- 7 vs 270 +/- 11 msec (p less than 0.01). In the adult animals, HR decreased from 116 +/- 35 to 66 +/- 25 bpm (p less than 0.01), STI decreased from 0.559 +/- 0.059 to 0.447 +/- 0.069 (p less than 0.01), and indexed TMS decreased from 333 +/- 10 to 291 +/- 13 msec (p less than 0.001). Two-way analysis of variance demonstrated that digoxin differed significantly in its effects on HR (p = 0.005), STI (p = 0.018), and TMS indexed for HR (p = 0.003) in neonatal compared to adult dogs. Pharmacokinetic studies showed a rapid distribution phase and equilibrium conditions at the time of physiologic measurements.(ABSTRACT TRUNCATED AT 250 WORDS)

Digoxin-like immunoreactive substance in fetuses with and without cardiac pathology

The concentration of digoxin-like immunoreactive substance was measured by immunoassay in umbilical venous blood from six normal and 19 fetuses with a variety of cardiac and noncardiac disorders. Fetal blood was obtained either by percutaneous umbilical blood sampling (n = 13) or at delivery (n = 12). Three women received digoxin for fetal indications. Healthy control fetuses had significantly less digoxin-like immunoreactive substance measured (mean concentration below the limit of the assay sensitivity) than was found in ill fetuses whose mothers received digoxin (p less than 0.005). However, the fetal concentrations of immunoreactive digoxin in fetuses with a cardiac abnormality were similar whether the mother had (0.93 +/- 0.4 ng/ml) or had not (1.27 +/- 0.4 ng/ml) received digoxin (p = 0.1452). Although there was a significant negative correlation between digoxin concentration and gestational age (R = -0.5079, p less than 0.01), the youngest fetuses examined were generally the sickest. The correlation with gestational age was not significant if the normal control fetuses were excluded. One fetus with a cardiac tachyarrhythmia was examined during and after transplacental therapy. There was no change. It is possible that previously measured "digoxin" in "treated" fetuses represents digoxin-like immunoreactive substance and that only small amounts of maternally administered digoxin actually reach the ill fetus. Our findings suggest that a randomized trial of maternal digitalization for the treatment of fetal supraventricular tachycardia is essential prior to its acceptance as effective therapy.

Transplacental passage of digoxin in the case of nonimmune hydrops fetalis

Successful treatment of intrauterine fetal tachyarrhythmia was reported in several cases recently. It was also pointed out that placental transfer of digoxin is unsatisfactory under certain conditions. However, it has not been clearly shown in which cases fetal digoxin level does not reach the maternal level. We present a case of nonimmune hydrops fetalis due to congenital atrial flutter in which digoxin concentration in the sera of the mother and the neonate showed significant dissociation, and discuss perinatological matters about the digoxin treatment and the factor that obstructs the transplacental passage of digoxin. Conclusively, we recommend that maternal digoxin concentration should be raised to near toxic level if the resolution of fetal and placental hydrops is not attained in the initial digoxin loading.

Intrauterine treatment of fetal tachycardia

The presence of sustained tachycardia in a fetus can result in congestive heart failure, hydrops, and eventual fetal death. With the increased use of advanced technology in routine obstetric practice, fetal tachycardias are being diagnosed with greater frequency. Recently, administration of antiarrhythmic medications to the mother has been successful in slowing the fetal heart rate and preventing or reversing potentially lethal complications in the fetus. The medications that have been used to treat fetal tachycardia and their potential effects on the mother are discussed. A case study and nursing protocol are presented.

Digoxin inhibition of relaxation induced by prostacyclin and vasoactive intestinal polypeptide in small human placental arteries

Small chorionic plate arteries were obtained from human placentae following normal vaginal delivery. Tubal vascular preparations were dissected, mounted in organ baths, and their isometric tension was recorded. Digoxin (10(-6) M) caused a rise in basic tension, reaching a maximum of 17 per cent of contractions induced by potassium (124 mM) depolarization. Pretreatment with digoxin did not significantly influence the concentration-dependent contractile responses to 5-hydroxytryptamine and prostaglandin F2 alpha (PGF2 alpha). In preparations contracted with PGF2 alpha, cumulative addition of prostacyclin (PGI2) and vasoactive intestinal polypeptide (VIP) produced concentration dependent relaxations. Digoxin (10(-8) to 10(-6) M) inhibited and finally abolished these relaxant effects of PGI2 and VIP in a concentration-dependent fashion. Pretreatment by digoxin (10(-8) to 10(-6) M) diminished the relaxant effect of sodium nitroprusside, but the effect was less pronounced than that on PGI2- and VIP-induced relaxation. As PGI2 and VIP may be of importance for the maintenance of a low resistance of the fetal placental vascular bed, the finding that digoxin decreases the vasodilating effects of these agents might imply effects on placental resistance of cardiac glycosides when used in late human pregnancy.

Twin transfusion syndrome: successful in utero treatment with digoxin

A pregnancy complicated by twin transfusion syndrome is presented. When signs of cardiac failure (edema, ascites and hydramnios) persisted in the recipient twin, maternal digoxin therapy was instituted at 27 weeks' gestation. The signs of failure resolved, and the twins were delivered electively by cesarean section at 34 weeks. At birth, the syndrome was confirmed by examination of the infants and placenta. Both infants survived. Digoxin therapy is recommended for fetal heart failure from circulatory overload in twin transfusion.

Pharmacokinetics, bioavailability and serum levels of cardiac glycosides

Digoxin, the cardiac glycoside most frequently used in clinical practice in the United States, can be given orally or intravenously and has an excretory half-life of 36 to 48 hours in patients with serum creatinine and blood urea nitrogen values in the normal range. Since the drug is excreted predominantly by the kidney, the half-life is prolonged progressively with diminishing renal function, reaching about 5 days on average in patients who are essentially anephric. Serum protein binding of digoxin is only about 20%, and differs markedly in this regard from that of digitoxin, which is 97% bound by serum albumin at usual therapeutic levels. Digitoxin is nearly completely absorbed from the normal gastrointestinal tract and has a half-life averaging 5 to 6 days in patients receiving usual doses irrespective of renal function. The bioavailability of digoxin is appreciably less than that of digitoxin, averaging about two-thirds to three-fourths of the equivalent dose given intravenously in the case of currently available tablet formulations. Recent studies have shown that gut flora of about 10% of patients reduce digoxin to a less bioactive dihydro derivative. This process is sensitive to antibiotic administration, creating the potential for important interactions among drugs. Serum or plasma concentrations of digitalis glycosides can be measured by radioimmunoassay methods that are now widely available, but knowledge of serum levels does not substitute for a sound working knowledge of the clinical pharmacology of the preparation used and careful patient follow-up.

Henoch-Schönlein syndrome and selective IgA deficiency

A 9 year old girl presented with clinical manifestations of Henoch-Schönlein syndrome and macroscopic haematuria. Laboratory investigations showed selective IgA deficiency and renal biopsy showed mesangial proliferative glomerulonephritis with diffuse granular deposits of C3 on immunofluorescence. IgA deposits were absent.

Successful treatment of fetal atrial flutter and congestive heart failure

Fetal supraventricular tachycardia may cause congestive heart failure, hydrops fetalis, and intrauterine death. Tachycardia in a fetus of 34 weeks' gestation was diagnosed as atrial flutter by echocardiography, and was successfully treated by giving the mother digoxin.

New concepts and drugs in the treatment of congestive heart failure

This article seeks to make clear the basic differences in the treatment of heart failure between therapeutic maneuvers that are aimed at improving the mechanical loading conditions of the heart and those that are aimed at augmenting the fundamental contractile or inotropic state of the myocardium. Emphasis is placed on recognizing that treatment expectations must be viewed within an age- or maturity-dependent framework, since a diminished margin of cardiocirculatory reserve exists in the smallest and youngest patients that limits the extent of benefit that may be derived from diverse treatment approaches.