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Ann Thorac Surg 1996;61:814-816
© 1996 The Society of Thoracic Surgeons

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Original Articles: Cardiovascular

Incidence of Vocal Fold Paralysis in Infants Undergoing Ligation of Patent Ductus Arteriosus

Department of Otolaryngology-Head and Neck Surgery, Division of Cardiothoracic Surgery, Department of Surgery, and Division of Neonatology, Department of Pediatrics, University of Iowa Hospitals and Clinics, Iowa City, Iowa

Accepted for publication October 31, 1995.

	Abstract

Top Footnotes Abstract Introduction Material and Methods Results Comment References

 
Background. Left-sided, iatrogenic vocal fold paralysis (IVFP) secondary to recurrent laryngeal nerve injury is a potential complication of ligation of patent ductus arteriosus (PDA). This study investigates specific risk factors associated with IVFP.

Methods. A retrospective chart review was performed for all infants 12 months of age or younger who underwent operative PDA closure at the University of Iowa from January 1, 1991, to January 1, 1994.

Results. Six cases of IVFP were diagnosed in 68 infants who underwent PDA ligation using clips (52.9%), suture ligatures (41.2%), or both (5.9%). Compared with infants without postoperative IVFP, infants with IVFP were smaller at birth (0.9 versus 2.3 kg; p < 0.001) and more premature (gestational age, 26.3 versus 33.8 weeks; p < 0.001), and were smaller (1.1 versus 3.4 kg; p < 0.001) and younger (31.9 versus 88.4 days; p < 0.001) at operation. Weight gain from birth to operation was significant only in infants without postoperative IVFP (p < 0.05). Although the overall incidence of IVFP in all infants undergoing PDA closure was 8.8%, five of the six cases (83.3%) of IVFP occurred in extremely low birth weight infants, ie, those weighing 1 kg or less at birth. Among the cohort of extremely low birth weight babies undergoing operation, the incidence of IVFP was 22.7%. Iatrogenic vocal fold paralysis was associated only with the use of surgical clips; however, because clips were used in 90.9% of the premature infants requiring PDA ligation, it was not possible to establish whether suture ligature is a safer technique.

Conclusions. This study demonstrates that the single major risk factor for IVFP after ligation of PDA is birth weight less than 1 kg.

	Introduction

Top Footnotes Abstract Introduction Material and Methods Results Comment References

 
Vocal fold paralysis in infants can be congenital, iatrogenic, idiopathic, or neurologic. Studies from the last decade have ranked Arnold-Chiari malformation as the most common cause of vocal fold paralysis [1–3],although idiopathic causes also were common. More recent data suggest that iatrogenic factors are now the greatest cause of vocal fold paralysis in infants [4]. This relative change reflects advances in medical care and technology. Smaller and more critically ill infants are undergoing operative closure of patent ductus arteriosus (PDA) and are subject to the known risks of this procedure, including left-sided vocal fold paralysis. The purpose of this study was to determine the incidence of iatrogenic vocal fold paralysis (IVFP) after PDA ligation and to establish whether specific risk factors are associated with this outcome.

	Material and Methods

Top Footnotes Abstract Introduction Material and Methods Results Comment References

 
We reviewed the charts of all infants 12 months of age or younger who underwent operative PDA closure at the University of Iowa from January 1, 1991, to January 1, 1994. For each patient, sex, birth weight, gestational age, weight at operation, age at operation, date of operation, operative team, and method of ligation were recorded. All patients who underwent operative PDA closure had failed at least one trial of indomethacin in an attempt to close the ductus medically. Ligation was performed by either one of two staff surgeons using a limited dissection and placement of the clip near the aortic end of the ductus.

Infants who were referred to the Department of Otolaryngology for evaluation of postoperative stridor, hoarseness, or failure to wean from nasal continuous positive airway pressure underwent flexible fiberoptic nasolaryngoscopy to assess laryngeal dynamics. Vocal fold paralysis was defined as an immobile vocal fold during respiration, with otherwise normal anatomy including arytenoid contouring. Asymptomatic patients were not referred to the Department of Otolaryngology and therefore did not undergo this examination.

Statistical testing was performed using the two-sample t test for independent samples with unequal variances (Cochran's method) or the two-sample t test for independent samples with equal variances. Incidence rates of IVFP were calculated in the standard manner.

	Results

Top Footnotes Abstract Introduction Material and Methods Results Comment References

 
Sixty-eight patients (32 males, 47.1%) aged 12 months or less underwent PDA ligation at the University of Iowa during the study period. Six infants had IVFP, for an overall incidence of 8.8%. Average birth weights and gestational ages of the infants with and without IVFP were 0.9 and 2.3 kg and 26.3 and 33.8 weeks, respectively. These differences are statistically significant (p < 0.001). Significant differences also existed between infants with and without IVFP for both weight and age at the time of operation. Infants with IVFP weighed less at operation than those without IVFP (1.1 versus 3.4 kg; p < 0.001) (Fig 1) and were younger at operation (31.9 versus 88.4 days; p < 0.001) (Fig 2).

View larger version (23K): [in this window] [in a new window]   Fig 1. . Distribution of weight of infants at the time of patent ductus arteriosus ligation (L-PDA). The average weight of infants without vocal fold paralysis (VFP) was 3.4 kg, whereas the average weight of infants with VFP was 1.1 kg (p < 0.001). (s/p = status post.)

View larger version (17K): [in this window] [in a new window]   Fig 2. . Distribution of age of infants at the time of patent ductus arteriosus ligation (L-PDA). The average age of infants without vocal fold paralysis (VFP) was 88.4 days, whereas the average age of infants with VFP was 31.9 days (p < 0.001). (s/p = status post.)

Although the methods of ligation included clip (36 infants, 52.9%), suture (28 infants, 41.2%), or both (4 infants, 5.9%) (Fig 3), only clip ligation was associated with IVFP. Among ELBW babies, 20 (90.9%) had clip ligation and 2 (9.1%) had suture ligation (Fig 4).

View larger version (12K): [in this window] [in a new window]   Fig 3. . Methods of patent ductus arteriosus ligation (L-PDA) for all patients in this study. Thirty-six infants (53%) underwent ligation with a clip, 28 infants (48%) had ligation with suture ligature, and 4 (6%) had both methods. (s/p = status post; VFP = vocal fold paralysis.)

View larger version (13K): [in this window] [in a new window]   Fig 4. . Methods of patent ductus arteriosus ligation (L-PDA) for extremely low birth weight infants (1 kg or less). Twenty infants (91%) underwent ligation with a clip and 2 (9%) underwent ligation with a suture ligature. (s/p = status post; VFP = vocal fold paralysis.)

	Comment

Top Footnotes Abstract Introduction Material and Methods Results Comment References

 
The incidence of left-sided IVFP after operative PDA closure in this study was 8.8%. However, this figure belies the fact that two distinct populations undergo ductus operations: ELBW babies and infants greater than 1 kg in weight. Within these two populations, the incidence of IVFP was radically different. Among ELBW babies, the incidence was 22.7% (5 of 22); for heavier babies, the incidence was only 2.2% (1 of 46).

Statistically significant differences existed between patients with and without IVFP after PDA ligation, including differences in birth weight, gestational age, weight at operation, and age at operation. Five of six cases of IVFP in this series occurred in ELBW babies. These patients were smaller and younger at both birth and operation compared with patients in whom IVFP did not develop, implying that ELBW patients are at greater risk for IVFP.

By comparing birth weight versus operative weight in patients undergoing operative PDA closure, we documented a statistically significant gain in weight only in patients without IVFP. Among patients with IVFP, no significant weight gain occurred, reflecting the fact that these infants were sicker and required ligation earlier.

In this study, surgical clips were used in 52.9% of PDA ligations and in all patients who experienced IVFP. This bias would seem to implicate clipping as a risk factor for IVFP; however, this conclusion cannot be supported by our data. Although 5 of 20 ELBW babies had IVFP after clip ligation of the PDA, only 2 ELBW babies had suture ligation. The small sample size precludes determining whether the method of ligation affects outcome. Our data do indicate that the risk of IVFP is high in ELBW babies who require surgical closure of PDA. Clips are generally preferred in this population because less dissection is required, which minimizes operative time and the chance of tearing the great vessels. With limited dissection, however, the risk of including the recurrent laryngeal nerve in the clip may be increased. Because persistent vocal fold paralysis was documented in all of these patients after an average of 6 months of follow-up, it is likely that the recurrent laryngeal nerve was incorporated in the clip rather than subjected to traction injury alone.

Our results contradict those of Davis and associates [5], who reported finding IVFP in only 3 of 68 (4.4%) premature infants undergoing operative ligation of PDA and in 0 of 38 premature infants undergoing clip ligation.

Fan and colleagues [6] reported the incidence of IVFP after PDA ligation to be 4.2% among all patients and 8.0% in infants with birth weights less than 1.5 kg. These authors also found that IVFP occurred only in infants weighing less than 1.5 kg, results in agreement with our own. Their lower incidence of IVFP may reflect inclusion of a heavier patient population and ascertainment bias by pulmonologists, as other studies have demonstrated that pulmonologists diagnose vocal fold paralysis less frequently than do otolaryngologists examining the same patients [4]. In addition, the survival for ELBW premature babies during the period covered by Fan and colleagues (1983 to 1985) was lower than that during the period covered in this study (1991 to 1994).

Our data suggest that the increasing survival of premature babies has changed the relative incidence of vocal fold paralysis. Thus, IVFP after PDA ligation now appears to be the most common cause of vocal fold paralysis in infants [4]. As neonatologists are improving the survival of premature infants, more ligation procedures probably will be required. Because only infants with stridor, hoarseness, and difficulty weaning from nasal continuous positive airway pressure underwent evaluation for IVFP in this study, there may have been additional infants with IVFP who were not recognized. The data we report represent the minimal incidence rates, and the true incidence rates may be greater. The true incidence could be determined by preoperative and postoperative flexible fiberoptic nasolaryngoscopy studies of all infants undergoing PDA ligation.

	Footnotes

Top Footnotes Abstract Introduction Material and Methods Results Comment References

 
Address reprint requests to Dr Zbar, Department of Otolaryngology-Head and Neck Surgery, University of Iowa Hospitals and Clinics, 200 Hawkins Dr, Iowa City, IA 52242.

	References

Top Footnotes Abstract Introduction Material and Methods Results Comment References

 

1. Rosin DF, Handler SD, Potsic WP, Wetmore RF, Tom LWC. Vocal cord paralysis in children. Laryngoscope 1990;100:1174–9.[Medline]
2. Gentile RD, Miller RH, Woodson GE. Vocal cord paralysis in children one year of age and younger. Ann Otol Rhinol Laryngol 1986;95:622–5.[Medline]
3. Cohen SR, Geller KA, Birns JW, Thompson JW. Laryngeal paralysis in children: a long term retrospective study. Ann Otol Rhinol Laryngol 1982;91:417–24.[Medline]
4. Zbar RIS, Smith RJH. Vocal fold paralysis in infants 12 months of age and younger. Otolaryngol Head Neck Surg (in press).
5. Davis JT, Baciewicz FA, Suriyapa S, Vauthy P, Polamreddy R, Barnett B. Vocal cord paralysis in premature infants undergoing ductal closure. Ann Thorac Surg 1988;46:214–5.[Abstract]
6. Fan LL, Campbell DN, Clarke DR, Washington RL, Fix EJ, White CW. Paralyzed left vocal cord associated with ligation of patent ductus arteriosus. J Thorac Cardiovasc Surg 1989;98:611–3.[Abstract]

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This Article Abstract Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Add to Personal Folders Download to citation manager Author home page(s): Douglas M. Behrendt Permission Requests Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Zbar, R. I. S. Articles by Smith, R. J. H. Search for Related Content PubMed PubMed Citation Articles by Zbar, R. I. S. Articles by Smith, R. J. H.