Umbilical venous catheter misplacement due to unexpected supernumerary patent umbilical artery

Abstract

Background

Umbilical vein catheterization is relatively straightforward procedure because the vein is easily recognized as a single, large, thin-walled vessel. However, anomalies of the umbilical vessels, such as the multivessel cord, which embeds more than two arteries or more than one vein, can result in catheter misplacement.

Case presentation

We present a unique case of a supernumerary patent umbilical artery in an asphyxiated term neonate, which resulted in the misplacement of the umbilical venous catheter in one of the three arteries. The diagnosis of artery cannulation was made through a comprehensive analysis of the patient’s blood gases, the use of a pressure transducer to confirm the presence of a pulsatile arterial signal, and the interpretation of a chest X-ray. Subsequently, the catheter was removed without complication. A more detailed examination of the umbilical cord revealed the presence of three arteries and a vein, which was then successfully cannulated.

Conclusions

This case reinforces the notion that the umbilical cord may include more than three vessels, and that umbilical vein cannulation requires prior meticulous observation of the number of vessels to prevent misplacement of the catheter.

Background

Supernumerary vessels in the umbilical cord have rarely been described, probably because of their association with fetal anomalies and poor obstetric outcomes [1]. The most common supernumerary vessel cord anomalies include four vessels (two veins and two arteries or one vein and three arteries) and, less frequently, five and more vessels seen only at the fetal extremity of the umbilical cord [2, 3]. It is noteworthy that supernumerary patent umbilical vessels have never been reported in newborns born alive.

The supernumerary vessels in the umbilical cord are of embryological origin [4]. At 5 weeks of development the embryo is connected to the placenta by a stalk, which contains the umbilical vessels and allantois (primitive excretory duct). The umbilical arteries first appear as ventral branches of the paired dorsal aortas. With fusion of the paired dorsal aortas, the primitive umbilical arteries unite with the descending aorta, and the definitive umbilical arteries arise as two lateral branches from the internal iliac arteries. Simultaneously, an arterial plexus develops around the allantois and coalesces to form a single artery extending almost the entire length of the body stalk. This allantoic artery becomes shorter as the right and left umbilical arteries advance in the body. Adjacent to this stalk is the yolk sac stalk, which consists of the vitelline duct (yolk sac duct) and vitelline vessels, which run through the vitelline stalk to supply the yalk sac [5]. The vitelline artery is usually thin and follows the normal twisting of the main umbilical arteries [3]. It originates from the superior mesenteric artery. These structures all pass through the primitive umbilical ring. By 8 weeks of gestation, the vitelline duct and allantois become obliterated, leaving two umbilical arteries and one umbilical vein [5]. By 10 weeks of development, the vitelline vessels have disappeared, and remnants of the vessels are seen in approximately 4–11% of umbilical cords [2].

The persistence of either the original allantoic artery of the body stalk or a vitelline artery of the vitelline duct, both arising from the superior mesenteric artery, is very uncommon. Most reports describe them as a cause of abdominal pain, midgut volvulus, and hemorrhage, later in life when they become fibrous bands [6, 7].

This is the first report of a term neonate born alive with a four-vessel umbilical cord (three arteries and one vein) in which the umbilical vein catheter was inadvertently placed in a supernumerary umbilical artery, with the potential for serious complications. This case contributes to the existing body of literature on catheter misplacement and reinforces the concept that umbilical vein cannulation is a procedure that requires careful examination of the number and type of cord vessels in order to prevent misplacement of the catheter.

Case report

The infant’s parents consented to the writing and publication of the information presented in this manuscript. A baby boy was born vaginally through meconium-stained amniotic fluid in a level I maternity hospital after an uneventful pregnancy at 41 weeks gestation. Soon after birth, he received bag and mask ventilation for a few minutes because of depressed respiratory drive. Apgar scores were 4 at one minute, 5 at five minutes, and 8 at ten minutes. Birth weight was 3,980 g. Blood gas analysis on umbilical cord revealed base excess − 18.5 mmol/L and lactates 15.5 mmol/L. On physical examination, the infant showed persistent hypotonia accompanied by retention of the immature postural reflexes. The attending neonatologist therefore decided to transfer the baby boy to a level III unit for therapeutic hypothermia and, prior to transportation, inserted a single lumen 5 French umbilical venous catheter. According to the documentation obtained, it appeared that the tip position had not been confirmed by X-ray. Ten per cent glucose solution was infused through the catheter during transportation. Upon arrival to our Pediatric Intensive Care Unit, four hours after birth, the attending physician replaced the single-lumen umbilical catheter with a two-lumen catheter. Because it was just a matter of replacement, she did not look at the umbilical cord closely to make sure the vessel was the umbilical vein. To further complicate the situation, the supernumerary artery appeared as a wide bore, similar to the umbilical vein. The 5-French two-lumen catheter was inserted up to 9 centimeters (depth should have been 10–11 cm for a 3,980 g boy) after which the catheter stopped, even if blood was still easily aspirated. Vital signs were hemoglobin oxygen saturation 100%, fractional inspired oxygen 0.21, heart rate 110 beats per minute, respiratory rate 37 breaths per minute, core temperature 34.9 °C. Blood gases from the umbilical catheter yielded pH 7.32, partial pressure of carbon dioxide (pCO₂) 27 mmHg, partial pressure of oxygen (pO₂) 75 mmHg. Because the pO₂ and pCO₂ values were compatible with an arterial sample, the catheter was connected to a pressure transducer, and a high and pulsatile pressure signal indicated artery placement. A chest X-ray confirmed catheter misplacement (Fig. 1). After a more thorough examination of the umbilical cord revealed the presence of an additional vessel, namely the umbilical vein, facing the three arteries (Fig. 2). Following cannulation, blood gases and pressure signal confirmed it was the umbilical vein. Blood gases from the venous catheter were pH 7.31, pCO₂ 34 mmHg, pO₂ 45 mmHg. In the ensuing days, the infant underwent a series of diagnostic procedures for the detection of possible physical malformations. These included head magnetic resonance imaging, echocardiography, abdominal ultrasound, an ophthalmological examination, and a hearing evaluation. Gross malformations were excluded. No complications from artery catheterization were observed.

Fig. 1

Posteroanterior radiograph of the chest and abdomen. The venous catheter is misplaced in the patent supernumerary artery. On the right is a schematic representation of the catheter path

Fig. 2

Umbilical cord showing three arteries and one vein. The patent supernumerary artery and the vein are both cannulated

Unfortunately, the placenta was not available for examination and no information about umbilical cord vascular structure was found in prenatal ultrasonographies.

Discussion and conclusions

We report a unique case of inadvertent cannulation of a patent supernumerary umbilical artery during placement of an umbilical venous catheter in an asphyxiated neonate with a four-vessel cord. Blood gas analysis, use of a pressure transducer, and a chest radiograph helped identify the venous catheter misplaced in an artery. Careful inspection of the umbilical cord allowed visualization of the umbilical vein in the classic position facing the arteries, and a proper venous cannulation was possible. Our case differs from previously reported examples of supernumerary umbilical cord vessels in which the embryonic arterial remnants were visible at birth but were not patent and did not result in erroneous maneuvers.

Typical misplacement of an umbilical vein catheter is in the portal venous system, as evidenced by resistance to catheter advancement and inability to aspirate blood. In our case, although the insertion depth should have been 10–11 cm according to the formula Birth Weight times 3 plus 9 divided by 2, the catheter was inserted only 9 cm from the skin, as it could not be advanced any further [8]. The inability to advance a venous catheter is usually a sign of a hepatic vein cannulation and contrasts with the ability to draw blood easily, as in our case. Fortunately, we did not push the catheter deeper and avoided vascular trauma that would have possibly resulted in artery injury and likely hemoperitoneum.

Several conditions contributed to the misplacement of the catheter in the artery in our case. First, counting umbilical vessels is an uncommon medical practice; therefore, when two arteries are identified, it is generally assumed that the third vessel observed is actually the umbilical vein [2, 9]. Second, the vein usually faces the arteries (the umbilical cord looks like a face with two eyes and a mouth) [10], whereas in our case the third artery mistaken for the vein was located right between the two umbilical arteries. Consequently, even for a procedure that may appear elementary, such as umbilical vessel catheterization, it is imperative to be aware of the anatomical location of the umbilical vein relative to the arteries, and to acknowledge that the number of vessels in the umbilical cord can exceed three.

The most common numerical anomaly of the umbilical cord vessels includes a single artery and one vein, and, less frequently, two arteries and two veins [2, 3]. Supernumerary arteries have been reported rarely [3]. Over 1,000 umbilical cords, Jauniaux et al. showed microscopic evidence of embryonic remnants in 23.1% cases, and the embryonic vessels (30.4%) included only one case of accessory small artery, with no associated fetal malformation. This fourth vessel followed the course of the others and was present at both extremities of the cord [11].

When three arteries are present, one artery may be the consequence of the inhibition of the regression of the right vitelline artery, which remains as the caudal portion [5]. Another possible explanation for the presence of three arteries in the umbilical cord is the persistence of the allantoic artery, which may result from developmental errors, such as when the allantoic artery unites with the right and left umbilical artery [2]. We have no elements that would support either of these hypotheses.

If more than three vessels are present on either ultrasound or postnatal examination, the extra lumen may be a vein, an artery, or a remnant of the omphalomesenteric or allantoic duct. Although no other case of umbilical venous catheter malposition in a supernumerary artery has been reported, another cause of umbilical venous catheter malposition is the embryonic remnant of a persistent allantoic duct (urachus). Mattei described a newborn boy who developed urinary ascites after undergoing an attempted umbilical vein catheterization, which resulted in bladder perforation [12].

In conclusion, we present a case of inadvertent placement of an umbilical venous catheter into a patent supernumerary artery and its prompt detection by blood gas analysis, a pressure transducer and radiography. Those performing umbilical vein catheterization should be aware of the presence of a variant number of umbilical cord vessels, including three arteries and one vein, to avoid catheter misplacement.