Ductus venosus blood velocity in persistent pulmonary hypertension of the newborn

Rates of Air Embolism in Pediatric Patients Undergoing Surgical Procedures of the Peritoneum

Background: Air embolism during laparoscopic surgery is a rare but feared complication in the pediatric population. The objective of this study was to identify rates of air embolus in pediatric patients during hospitalization for laparoscopic or open surgical procedures of the peritoneal cavity. Materials and Methods: Patients 0-18 years old within the Pediatric Health Information System who underwent a predefined, common inpatient laparoscopic or open surgical procedure involving the peritoneal cavity from 2015 to 2020 were studied. International Classification of Diseases, Tenth Revision, Clinical Modification diagnosis codes for air embolism were then searched among patients during the same admission. Firth logistic regression was used to compare rates of air embolism in open and laparoscopic cohorts and in patients >1 and ≤1 year. Results: Unadjusted rates of air embolism were higher in patients undergoing open compared with laparoscopic surgery (open: 9/45,080; 20.0/100,000 patients versus laparoscopic: 3/101,892; 2.9/100,000 patients). In patients ≤1 year (45,726), 2 patients undergoing open surgery (2/1,031; 9.5/100,000 patients) and all 3 patients undergoing laparoscopic surgery had an air embolism diagnosis (3/22,329; 13.4/100,000 patients). For laparoscopic surgery, a suggested lower relative risk (RR) of air embolism was demonstrated for children >1 year compared with children ≤1 year (RR: 0.05, P = .05). Conclusion: Air embolism associated with common pediatric surgical procedures of the peritoneum is rare and patients undergoing laparoscopic and open surgery have similar risks for air embolism. Although rare, the risk should be considered during surgical planning and abdominal access, especially in children ≤1 year old.

Case Report: Clinical Features of Congenital Portosystemic Shunts in the Neonatal Period

Objective: The aim of this single-center retrospective study was to analyze the clinical characteristics, treatment options, and course of neonatal-onset congenital portosystemic shunts (CPSS). Methods: We included all patients with CPSS who presented with clinical symptoms within the neonatal period in our institution between 2015 and 2020. Results: Sixteen patients were identified, including 13 patients with intrahepatic portosystemic shunts (IPSS) and three patients with extrahepatic portosystemic shunts (EPSS). The median age of diagnosis was 16 days (range prenatal 24 weeks-12 months). Hyperammonemia (60%), neonatal cholestasis (44%), elevated liver enzyme (40%), hypoglycemia (40%), thrombocytopenia (38%), and coagulation abnormalities (23%) appeared in neonatal CPSS. Twelve patients (75%) presented with congenital anomalies, of which congenital heart disease (CHD) (44%) was the most common. Thirteen patients with IPSS initially underwent conservative treatment, but two of them were recommended for the catheter interventional therapy and liver transplantation, respectively, due to progressive deterioration of liver function. Spontaneous closure occurred in nine patients with IPSS. The shunt was closed using transcatheter embolization in one patient with EPSS type II. Another patient with EPSS type II underwent surgical treatment of CHD firstly. The remaining patient with EPSS type Ib received medical therapy and refused liver transplantation. Conclusion: Hyperammonemia, neonatal cholestasis, elevated liver enzyme, hypoglycemia, and thrombocytopenia are the main complications of neonatal CPSS. Moreover, CPSS is associated with multiple congenital abnormalities, especially CHD. Intrahepatic portosystemic shunts may close spontaneously, and conservative treatment can be taken first. Extrahepatic portosystemic shunts should be closed to prevent complications.

Patent Ductus Venosus and Congenital Heart Disease: A Case Report and Review

In utero, the ductus venosus connects the left portal vein to the inferior vena cava, allowing a portion of the venous blood to bypass the liver and return to the heart. After birth, the ductus venosus closes due to changes in intracardiac pressures and a decrease in endogenous prostaglandins. Failure of the ductus venosus to close may result in galactosemia, hypoxemia, encephalopathy with hyperammonia, and hepatic dysfunction. We report an infant with complex congenital heart disease (CHD) who developed coagulopathy and hyperammonia during the preoperative period secondary to patent ductus venosus (PDV). Previous reports of PDV in CHD are presented, its etiology and clinical consequences reviewed, and options for therapeutic treatment discussed.

Physiology of the fetal circulation

Our understanding of fetal circulatory physiology is based on experimental animal data, and this continues to be an important source of new insight into developmental mechanisms. A growing number of human studies have investigated the human physiology, with results that are similar but not identical to those from animal studies. It is time to appreciate these differences and base more of our clinical approach on human physiology. Accordingly, the present review focuses on distributional patterns and adaptational mechanisms that were mainly discovered by human studies. These include cardiac output, pulmonary and placental circulation, fetal brain and liver, venous return to the heart, and the fetal shunts (ductus venosus, foramen ovale and ductus arteriosus). Placental compromise induces a set of adaptational and compensational mechanisms reflecting the plasticity of the developing circulation, with both short- and long-term implications. Some of these aspects have become part of the clinical physiology of today with consequences for surveillance and treatment.

The Aryl Hydrocarbon Receptor Is Required for Developmental Closure of the Ductus Venosus in the Neonatal Mouse

A developmental role for the Ahr locus has been indicated by the observation that mice harboring a null allele display a portocaval vascular shunt throughout life. To define the ontogeny and determine the identity of this shunt, we developed a visualization approach in which three-dimensional (3D) images of the developing liver vasculature are generated from serial sections. Applying this 3D visualization approach at multiple developmental times allowed us to demonstrate that the portocaval shunt observed in Ahr-null mice is the remnant of an embryonic structure and is not acquired after birth. We observed that the shunt is found in late-stage wild-type embryos but closes during the first 48 h of postnatal life. In contrast, the same structure fails to close in Ahr-null mice and remains open throughout adulthood. The ontogeny of this shunt, along with its 3D position, allowed us to conclude that this shunt is a patent developmental structure known as the ductus venosus (DV). Upon searching for a physiological cause of the patent DV, we observed that during the first 48 h, most major hepatic veins, such as the portal and umbilical veins, normally decrease in diameter but do not change in Ahr-null mice. This observation suggests that failure of the DV to close may be the consequence of increased blood pressure or a failure in vasoconstriction in the developing liver.

The fetal circulation

Accumulating data on the human fetal circulation shows the similarity to the experimental animal physiology, but with important differences. The human fetus seems to circulate less blood through the placenta, shunt less through the ductus venosus and foramen ovale, but direct more blood through the lungs than the fetal sheep. However, there are substantial individual variations and the pattern changes with gestational age. The normalised umbilical blood flow decreases with gestational age, and, at 28 to 32 weeks, a new level of development seems to be reached. At this stage, the shunting through the ductus venosus and the foramen ovale reaches a minimum, and the flow through the lungs a maximum. The ductus venosus and foramen ovale are functionally closely related and represent an important distributional unit for the venous return. The left portal branch represents a venous watershed, and, similarly, the isthmus aorta an arterial watershed. Thus, the fetal central circulation is a very flexible and adaptive circulatory system. The responses to increased afterload, hypoxaemia and acidaemia in the human fetus are equivalent to those found in animal studies: increased ductus venosus and foramen ovale shunting, increased impedance in the lungs, reduced impedance in the brain, increasingly reversed flow in the aortic isthmus and a more prominent coronary blood flow.

Usefulness of a new Doppler index for assessing both ventricular functions and pulmonary circulation in newborn piglet with hypoxic pulmonary hypertension

Persistent pulmonary hypertension of the newborn is a clinical syndrome associated with a variety of cardiopulmonary diseases. Serial evaluation of pulmonary circulation and cardiac function is important, but available imaging techniques have been limited. A new Doppler index combining systolic and diastolic time intervals (the Tei index, which is a simple and noninvasive measurement) has been reported to be useful for the assessment of global cardiac function in adults and children. The purpose of this study was to test the effectiveness of the Tei index in prospectively assessing ventricular function and pulmonary circulation in a newborn piglet model with hypoxic pulmonary hypertension. One-day-old piglets (1.1-1.6 kg) were intubated and prepared for the experiments under room air and hypoxia. A complete two-dimensional Doppler echocardiographic examination was performed. Common hemodynamic variables were measured continuously throughout the study. The right ventricle (RV) Tei index under hypoxia (fraction of inspired oxygen = 0.10) was significantly higher than the value under air ventilation (medians, 0.38 versus 0.56; p < 0.05). Moreover, there was a significant correlation between RV Tei index and mean pulmonary artery pressure and positive linear correlation between individual changes in RV Tei index and changes in mPAP (r2 = 0.799, p < 0.05). We conclude that the Tei index is useful for assessing the function of the RV and the left ventricle and pulmonary circulation in a newborn piglet model with hypoxic pulmonary hypertension. These results suggest that the Tei index will become an objective method of assessing patients with persistent pulmonary hypertension of the newborn.

The ductus venosus

Until recently, our information on the ductus venosus was based on postmortem and experimental studies. The present review relates to the modern concept of this vein predominantly founded on clinical studies. Recent publications show that the blood distribution through the ductus venosus is particularly sensitive to changes in umbilical venous pressure, blood viscosity, and an active regulation of diameter of the entire ductus venosus. The mean fraction of umbilical blood shunted through the ductus is reduced from 30% to 20% during the second half of the human pregnancy, indicating that, during this period, the fetal liver has a higher priority than the shunting through the ductus venosus, apart from the compensatory redistribution needed during extreme challenges of placental compromize and hypoxemia. Additionally, the ductus venosus acts as a transmission line to the umbilical vein for pulse waves generated in the heart. These waves, reflecting cardiac function, are substantially influenced by the local variation of impedance and compliance.

Ductus venosus flow velocity in newborn lambs during increased pulmonary artery pressure

The aim of the present study was to assess with ultrasound the ductus venosus flow velocity in newborn lambs with increasing pulmonary artery pressures and to evaluate whether this is a useful method to detect elevated pulmonary artery pressure. The ductus venosus flow velocity was studied with pulsed-wave Doppler echocardiography in nine newborn lambs < or = 30 h old. The lambs were anesthetized, mechanically ventilated, and instrumented to measure mean airway pressure and pulmonary artery and arterial blood pressures. A vascular occluder was placed around the main pulmonary artery. With mean pressures ranging from 20 to 50 mm Hg in the pulmonary artery, the ductus venosus flow velocity was examined. In seven lambs, the mean portal pressure and central venous pressure were also measured. With a stepwise increase in the pulmonary artery pressure, the minimum ductus venosus flow velocity during atrial systole decreased to a reversed flow, and the duration of this reversed flow component increased. The systolic forward peak flow velocity signal also gradually decreased. No changes were detected in the mean central venous or in the portal pressure with increasing pulmonary artery pressure or changes in ductus venosus flow. The flow velocity in the ductus venosus, which is higher than in other precordial veins, shows a reduction and even reversal of the nadir and an increase of the duration of reversed flow during atrial systole as a response to increased pulmonary artery pressure. Thus, Doppler ultrasound of the ductus venosus flow velocity may be a useful noninvasive diagnostic supplement to detect pulmonary hypertension of the newborn.