Vocal Cord Paralysis and Dysphagia after Aortic Arch Reconstruction and Norwood Procedure

Abstract

Objectives

Determine the incidence of vocal cord paralysis and dysphagia after aortic arch reconstruction including Norwood procedure.

Setting

Tertiary Children’s Hospital

Study Design

Retrospective cohort.

Methods

Database/chart review of neonates requiring Norwood or arch surgery between January 2005 through December 2012. Demographics, postoperative vocal cord function, dysphagia, need for gastrostomy tube and/or tracheotomy, and long-term follow-up were reviewed.

Results

One hundred fifty-one consecutive subjects(96 Norwood, 55 aortic arch) were reviewed. Median age at repair was 9 days(IQR 7–13) for Norwood, 24 days(IQR 12–49) for arch reconstruction(p<0.001). Documentation of VC motion abnormality was found in 60/104(57.6%) subjects, and unavailable in 47:16 without documentation and 31 who expired prior to extubation. There were no significant differences in proportions of documented VC motion(p=0.337), dysphagia(p=0.987), and VC paralysis(p=0.706) between the arch and Norwood groups. Dysphagia was found in 73.5% of Norwood and 69.2% of arch subjects who had documented VC paralysis. Even without UVCP, dysphagia was present (56% Norwood,61% arch). Overall, 120/151(79.5%) required feeding evaluation and modified feeding regimen. Gastrostomy was required in 31% of Norwood and 23.6% of arch reconstruction overall. To date, mortality in this series is 55/151(36.4%) patients. Of those with VC paralysis, only 23(22%) had any otolaryngology follow-up after discharge from surgery. Over 75% with VC paralysis with follow-up after hospital discharge had persistent VC paralysis 11.5 months after diagnosis.

Conclusion

There is high incidence of UVCP and dysphagia after Norwood and arch reconstruction. Dysphagia was highly prevalent in both groups even without UVCP. Preoperative discussion on vocal cord function and dysphagia should be considered.

Introduction

One of the most commonly observed outcomes of neonatal cardiothoracic surgery (CTS) is left vocal cord paralysis, which may be attributable to sustained ventilation or surgical repairs.^1–3 Two common neonatal CTS procedures are aortic arch reconstruction and the Norwood procedure. These procedures involve surgical correction of the aortic arch, putting the left recurrent laryngeal nerve (RLN) at considerable risk of injury. In this patient population, there has been a wide range of reported incidences of vocal cord dysfunction, primarily unilateral vocal cord paralysis, ranging from 9% to 59%.^4–6

The RLN is a branch of the vagus (CN X), and the left RLN is longer than the right since it courses under the aortic arch at the ligamentum arteriosum then ascends along the tracheoesophageal groove. In addition to motor control of all intrinsic laryngeal muscles except the cricothyroid (innervated by superior laryngeal nerve), studies have shown variation in extralaryngeal branches from the RLN which provide sensory or autonomic fibers to the larynx, trachea, esophagus, pharynx, and inferior constrictor muscle amongst individuals.^7–10 Additionally, the interarytenoid muscle is the only intrinsic laryngeal muscle with bilateral innervation. Left vocal cord paralysis in neonates, regardless of cause, results in not only respiratory difficulty but concomitant dysphagia.

Unilateral vocal cord paralysis (UVCP) in neonates may presents postoperatively with stridor, weak cry, dysphonia, poor feeding, and/or aspiration.^11–13 Once identified, nasogastric tube feeding, and even gastrostomy tube placement, may be necessary. Concomitant tracheotomy may also be needed for prolonged mechanical ventilation, respiratory compromise, and aspiration.^12,13,14 Up to 45% of the patients with UVCP after cardiothoracic surgery demonstrate abnormalities on barium swallowing studies including frank aspiration.¹⁵

Unilateral vocal cord paralysis following CTS is also associated with the significant use of health care resources. Neonatal CTS patients that have UVCP have a significantly longer length of stay in the hospital and a more frequent need for alternative feeding regimens compared to patients without vocal cord dysfunction.^4,16,17 In a single-center study, vocal cord paralysis from iatrogenic causes has been shown to have lower spontaneous recovery rates than other causes.³

Consultation to pediatric otolaryngology to assess vocal cord function after CTS surgery is common but not yet universal. Although dysphagia may return to normal after several months, the recovery rate of full vocal cord motion has not been extensively studied.¹ The incidence and long-term outcomes of VC dysfunction following CTS in neonates remain unknown.

Methods

An institutional review board–approved retrospective cohort study was performed at Children’s Mercy Hospitals and Clinics (CMH) in Kansas City, Missouri. This 317-bed tertiary care, freestanding, pediatric hospital serves 150 counties over six Midwestern states. Consecutive cases were identified by a data query of the Heart Center Database using Current Procedural Terminology (CPT) codes for the Norwood procedure and aortic arch reconstruction. Patients were treated between January 2005 and December 2012. Documentation of post-operative airway stability, presence of dysphagia, need for clinical and formal feeding evaluation and assessments, need for alternative feeding modalities, need for gastrostomy tube and/or tracheostomy tube placements, were all assessed and reviewed. If vocal cord paralysis was identified, subsequent follow-up data on vocal cord function by otolaryngology were also reviewed.

Statistical Analyses

Data were abstracted from medical charts and entered into a database for analysis. Descriptive statistics are listed as medians with interquartile ranges (IQR) for continuous variables and a number percentage for categorical variables. Medians were chosen due to the presence of significant outliers that disproportionately affect the mean values. The Wilcoxon rank sum test was used for comparisons of medians. The χ² test or Fisher’s exact tests were used for comparisons of categorical variables, as appropriate. Statistical significance was established a priori at 0.05. Statistical analysis was performed with SPSS, version 20.0 (SPSS Inc, Chicago, IL, USA).

Results

During the study period 151 consecutive patients underwent either a Norwood procedure (n=96) or an aortic arch reconstruction (n=55), with 87 (57.6%) males. Baseline characteristics are summarized in Table I. The median age at time of repair was 9 days (IQR 7–13) for Norwood procedures and 24 days (IQR 12–49) for aortic arch reconstruction (p<0.001). Since this study aimed at reviewing incidence and prevalence of UVCP and dysphagia, and for the purposes of reviewing outcomes related to vocal cord function and feeding, we excluded 16 patients (6 Norwood, 10 arch) who did not have documentation of vocal cord function postoperatively. Additionally, 31 patients (25 Norwood, 6 arch) expired prior to extubation after surgery so vocal cord function was not assessed. Data summary is therefore based on 104 patients with documentation of vocal cord function by bedside awake flexible fiberoptic laryngoscopy after extubation. Of the 104 patients, 65 underwent the Norwood procedure while 39 underwent aortic arch reconstruction only. The most common medical comorbidities include DiGeorge Syndrome (5.3%) and prematurity (4.6%).

TABLE I.

Baseline Characteristics.

	Norwood (n=96)		Arch (n=55)		p-value	Total Study Population (n=151)
	Median	IQR	Median	IQR		Median	IQR
Age, days	9	7–13	24	12–49	<0.001	12	7–21
	n	%	n	%		n	%
Gender
Male	59	61.5	28	50.9	0.233	87	57.6
Female	37	38.5	27	49.1		64	42.4
Medical Co-Morbidity Totals	14	14.6	22	40	<0.001	36	23.8
DiGeorge Syndrome	1	1.0	7	12.7		8	5.3
Prematurity	2	2.1	5	9.1		7	4.6
Trisomy 21	2	2.1	3	5.5		5	3.3
Turner Syndrome	2	2.1	2	3.6		4	2.6
Dextrocardia	1	1.0	0	0.0		1	0.7
CHARGE	0	0.0	1	1.8		1	0.7
Other Genetic/Congenital Abnormality	6	6.2	4	7.3		10	6.6

Table II summarizes the findings on 104 patients (65 Norwood, 39 arch) with documented assessments of VC function and whether they experienced dysphagia postoperatively. Overall, vocal cord motion abnormality was found in 60/104 (57.6%) of subjects, 34/65 (52.3%) in the Norwood group and 26/39 (67%) in the aortic arch reconstruction group. When vocal cord motion abnormality was documented, dysphagia was noted in 70.6 % of Norwood and 57.7% of arch patients. Even when vocal cord motion was documented to be normal without paralysis, 61.5% of patients in both groups were noted to demonstrate dysphagia as defined by inability to tolerate adequate oral intake without supplementation by nasogastric (NG) tube feeding. Overall, dysphagia was noted in 65% of those with documented vocal cord motion abnormality and in 61% of those with documented normal vocal cord function.

Table II.

VC Motion and Dysphagia (p=0.218)

	Norwood (n=65)		Arch (n=39)			Total
	n	%	n	%	p-value	n	%
Abnormal VC Motion	34	52.3	26	67.0		60	57.6
Dysphagia	24	70.6	15	57.7	0.414	39	65.0
No Dysphagia	10	29.4	11	42.3		21	35.0
Normal VC Motion	31	32.3	13	23.6		44	29.1
Dysphagia	19	61.5	8	61.5	1.000	27	61.4
No Dysphagia	12	38.5	5	38.4		17	38.6

The types of documented abnormal VC motion are summarized in Table III. The most common VC dysfunction documented by pediatric otolaryngology was left UVCP paralysis, found in 91.2% of Norwood and 96.2% or arch reconstruction patients. There were 2 cases of unilateral right VC paralysis identified in the Norwood group, and one case in each group with bilateral vocal cord paralysis. Statistical analyses showed that there were no significant differences in the proportions of documented VC motion (p=0.337), dysphagia (p=0.987), and VC dysfunction (p=0.706) between the subjects that received aortic arch reconstruction and the subjects that underwent the Norwood procedure. There were also no differences based on surgeon. Overall, 76/104(73%) required some form of feeding evaluation and modified feeding regimen. There was no standard protocol regarding work up once clinical dysphagia was identified. Overall, 30 subjects underwent a modified barium swallow study, 23 had an upper GI study, 13 received clinical feeding evaluation with an occupational therapist, and 2 underwent pH studies. A wide array of alternative feeding modalities were utilized in these subjects once dysphagia was identified, including chilled and thickened feedings, use of nasogastric tube with or without oral feeding. Overall in Norwood subjects, 12/32 (37.5%) with normal VC motion and 18/34 (52.9%) with vocal cord dysfunction required gastrostomy tube placement. For arch reconstruction only, 5/13 (38.4%) with normal VC motion and 8/26 (30.7%) with vocal cord motion abnormality required gastrostomy tube placement. For the entire group, gastrostomy tubes were placed in 27/60 (45%) patients with VC dysfunction, and 17/45 (37.7%) subjects with normal VC motion.

Table III.

VC Motion Abnormalities

	Norwood (n=34)		Arch (n=26)		Total (n=60)
	n	%	n	%	n	%
Unilateral Left VC Paralysis	31	91.2	25	96.2	56	93.3
Unilateral Right VC Paralysis	2	5.9	0	0.0	2	3.3
Bilateral VCP	1	2.9	1	3.8	2	3.3

Table IV summarized the forms of feeding for the entire study group of 151 consecutive patients upon time of hospital discharge, with only 25% of Norwood and 36.4% of arch reconstructions patients able to safely tolerate adequate oral intake without needing additional supplementation by other modalities of feeding. About 20% of the entire study population was discharged with instructions for strict non-oral (nil per os) feeding due to risk of aspiration. Gastrostomy tube placement with or without Nissen fundoplication was required in 31.3% of Norwood and 16.3 % of arch patients, while 3.1% of Norwood and 12.7% of arch reconstruction patients required tracheostomy tube in addition to the gastrostomy tube placement.

Table IV.

Form of Feeding Upon Discharge (p=0.011), no. (%)

	Norwood (n=96)	Arch (n=55)	Total (n=151)
PO	24 (25.0)	20 (36.4)	44 (29.1)
NPO	25 (26.0)	6 (10.9)	31 (20.5)
G-Tube ± Fundoplication	30 (31.3)	1 (16.3)	39 (25.8)
G-Tube/Fundoplication/Tracheotomy	3 (3.1)	7 (12.7)	10 (6.6)
NG-Tube/PO	8 (8.3)	6 (10.9)	14 (9.3)
NG-Tube	5 (5.2)	7 (12.7)	12 (7.9)
TPN	1 (1.0)	0 (0.0)	1 (0.7)

Follow-up data, defined as a subsequent outpatient visit to pediatric otolaryngology with documentation of vocal cord motion by awake flexible fiberoptic laryngoscopy, was available on 23/60 (38.3%) of patients identified with vocal cord dysfunction. Length of follow-up varied with mean of 11.5 months (median 3 months, maximum 72 months). Overall, 15 had no improvement; six had partial improvement; and two had normal VC motion. Documentation was performed by several pediatric otolaryngology providers. To date, mortality in this series was confirmed in 55/151 (36.4%) subjects, six of whom had initially followed-up. Specifically, the mortality proportion of the subjects that underwent the Norwood procedure (45/96, 46.9%) was significantly higher than the subjects that underwent aortic arch reconstruction (10/55, 18.2%; p<0.001). Excluding the deceased population, 79/96 (82.3%) of subjects had no follow-up data regarding VC motion after hospital discharge.

Discussion

Surgical trauma and endotracheal intubation are the most common iatrogenic causes of VC paralysis.^2,3 Unilateral VCP limits the vocal cord’s ability to abduct upon inspiration, causing stridor.¹⁸ It may lead to increased risk of aspiration due to failure of adduction upon swallowing.¹⁹ We chose to review vocal cord paralysis and dysphagia in patients undergoing either the Norwood Procedure or isolated aortic arch reconstruction since the risk of iatrogenic surgical trauma to the left RLN is the highest in these two operations as the nerve courses under the aortic arch through the ligamentum arteriosum. ¹⁵ Hypoplastic Left Heart Syndrome (HLHS) is the most complex congenital heart defect which is defined by 4 main anatomical anomalies: 1) hypoplastic ascending aorta and aortic arch, 2)hypoplastic left ventricle, 3) large patent ductus arteriosus supplying the only source of blood flow to the body, and 4) atrial septal defect allowing blood returning from the lungs to reach the single ventricle. The surgical repair for HLHS involves three staged operations performed during the first two years of life: The Norwood Procedure, Bi-Directional Glenn, and the Fontan Operation. The Norwood procedure primarily palliates neonates born with congenital hypoplastic left heart syndrome (HLHS) or one of its variants. The Norwood is performed shortly after birth and converts the right ventricle into the main functioning ventricle to provide blood to the lungs and body as well as a shunt placement which connects the main pulmonary artery to the aorta. The main pulmonary artery is separated from the two branching pulmonary arteries that direct blood to the lungs. Aortic arch surgery is performed on neonates with a variety of aortic arch anomalies including those with HLHS, interrupted aortic arch, hypoplastic aortic arch, and complex aortic coarctation. This surgery requires a period of circulatory arrest and deep hypothermia. Neonates undergo the Norwood Procedure earlier than isolated aortic surgery due to the severity of HLHS, which explains the significant difference in age between the two groups at the time of surgery. The severity of HLHS is also reflected by the higher mortality rate in this group compared to the aortic arch repair group without HLHS. However, the proportions of VC dysfunction and dysphagia were comparable in both treatment groups.

Early detection and monitoring of vocal cord immobility is critical for respiratory and swallowing function. While traditional otolaryngology belief and experience is that adults may be able to have a safe airway, minimal dysphagia, and good quality of voice despite UVCP, this is in fact not the case with neonates. Early identification of UVCP explains potential difficulty with inadequate airway requiring intervention, and commonly need for alternative feeding regimens. Another frequent experience shared by pediatric otolaryngologists who perform this diagnosis as a part of inpatient consultation is the difficulty in counseling the parents regarding prognosis and long term outcome of unilateral vocal cord paralysis once identified post cardiothoracic procedure. Identifying the presence of vocal cord dysfunction is the first step in directing subsequent therapy, including surgical intervention as medialization of the affected vocal cord has been shown to reduce the rate of pneumonia and length of stay.^20,21

Excluding the 31 patients who expired prior to extubation, there were only 16/120 (13.3%) patients in whom documentation of vocal cord function was not found in our review. Since the publication by Skinner et al in 2005, the CTS department adopted a clinical pathway with the intent that all patients undergoing aortic arch reconstruction would receive pediatric otolaryngology consultation and awake flexible fiberoptic laryngoscopy to document vocal cord motion after successful extubation from the procedures.⁴ Otolaryngology consultation and request for evaluation of vocal cord function by awake flexible laryngoscopy are typically ordered as soon as the neonate is extubated after Norwood or arch reconstruction surgery, before leaving the intensive care unit. We suspect that due to variations in pediatric intensivist’s coverage not all patients followed this protocol and may have not had documentation of VC function post-extubation. Our data interpretation and discussions regarding normal vocal cord motion are based only in the context of their documentation as there is no presumed presence or absence of vocal cord motion based on other factors.

An interdisciplinary approach to pediatric patients needing cardiothoracic surgery would prepare families and reduce the “unexpected” morbidities associated with unilateral vocal cord paralysis postoperatively. In our study, 79.5% of patients required a modified feeding regimen. A significantly higher proportion of Norwood patients required an altered form of feeding compared to arch repair patients. Cardiothoracic surgeons can report on their impression of probable damage to the recurrent laryngeal nerve.²² Occupational therapists and speech pathologists can be consulted early to assess feeding abnormalities. Videofluoroscopic barium swallow studies can be used to assess the severity of dysphagia, presence of laryngeal penetration, and/or frank aspiration, and hence influence the need for either nasogastric tube feeding or even need for gastrostomy tube placement.¹³ Based on our findings we believe there is a need to develop protocol for step-wise work up once clinical dysphagia has been identified post-extubation. Such a protocol may reduce unnecessary and potentially redundant radiation exposure from ordering both barium and modified barium swallow studies.

Several alterations in medical and surgical care have been shown to reduce the incidence of vocal cord injury. Intraoperative monitoring of the recurrent laryngeal nerve has been proven to be useful in pediatric cervical surgeries.²³ However, there are currently no intraoperative NIM (nerve integrity monitor) electromyography endotracheal tubes small enough for CTS surgery in neonates, as the smallest NIM electromyography endotracheal tubes are currently sized at 5.0 (outer diameter 6.5 mm). Another type of monitoring device was the “Contact EMG” endotracheal tubes which had taped on or wrapped around the electrodes on the outside of the endotracheal tubes. Videolaryngoscopy could assist in successfully intubating difficult cases.²⁴ Modifications in surgical techniques could also reduce the incidence of vocal cord injury.¹⁵ Although these changes have been studied, they have not yet been widely adopted, and until routine use of electromyography endotracheal tubes are available for neonates, or another method of reliable monitoring of vocal cord motion (electroglottigraph), the focus must be directed at the diagnosis and routine follow-up surveillance of all infants s/p Norwood and arch reconstruction. Our study is the first to show that the rate of dysphagia is significant after Norwood and arch reconstruction even if there is no vocal cord dysfunction identified postoperatively. Therefore, we advocate collaborative follow up between cardiothoracic surgery, cardiology, otolaryngology, speech language pathology and/or occupational therapy. Long term follow up with otolaryngology is necessary in order to follow status of vocal cord function and dysphagia, in hopes that there may be return to normal and competent swallowing regardless of return of vocal cord function.

Our study has several limitations. First, selection bias may be an inherent weakness of this study design as we chose to review 151 consecutive cases. However, our study population consisted of consecutive patients that underwent a surgical procedure of interest. Therefore, we believe our findings appropriately represent this particular patient population. Second, contrary to previous studies, our findings of vocal cord dysfunction were not significantly associated with feeding difficulties. However, there may be a difference that we were unable to detect with the current sample size. Third, long-term outcome in patients with identified vocal cord motion abnormality could not be adequately interpreted as only 38% of our patients had documented otolaryngology follow up for vocal cord dysfunction once identified and discharged from the hospital. Since the study population were cared for at a children’s hospital which serves patients from over 150 counties, the lack of consistent outpatient otolaryngology follow-up demonstrates an opportunity for improvement in clear communication to parents and caretakers by both CTS and otolaryngology teams.

Long term follow up should be routinely scheduled as a part of the overall follow up for their cardiac status. Some patients are lost to follow up by otolaryngology especially if they are followed by local cardiologists once they are stable postoperatively. Prospectively evaluation of this group of patients will enable data collection to determine the long-term outcomes of both vocal cord dysfunction and dysphagia. We did not review duration of cardiopulmonary bypass time as a potential factor which has recently been found to be associated with higher incidence of UVCP in neonates undergoing aortic surgery.²⁵

The strengths of this study are that this represents one of the largest cohort of aortic surgery patients reviewed specifically for vocal cord dysfunction and dysphagia, and our findings support the need to develop an awareness across disciplines for collaborative and active discussions amongst cardiothoracic surgeons and otolaryngologists at tertiary children’s hospitals. Developing consistent protocols for the evaluation, diagnosis, work-up, and follow-up for both vocal cord dysfunction and dysphagia in this population will improve best practice for patients and avoid potential unnecessary delays in diagnosis and treatments. Finding a high prevalence of dysphagia in both Norwood and arch reconstruction patients even when UVCP was not identified challenges potential misconception that as long as UVCP is not found otolaryngology participation is complete after consultation. Based on our findings, we suggest emphasis to pediatric intensivists to routinely obtain otolaryngology consultation after extubation of every patient undergoing these two procedures, as well as, consistent documentation by otolaryngologists who perform these inpatient consultations. Clear communication to families about the impact of vocal cord dysfunction and/or dysphagia is necessary to ensure compliance with scheduled follow-up visits to otolaryngology after hospital discharge. Currently these two patient populations do not routinely undergo preoperative assessment of vocal cord function; This preoperative assessment should be part of future studies to differentiate between iatrogenic versus congenital causes of UVCP.

As stated in our introduction, since there are variation in extralaryngeal branches from the RLN which provide sensory or autonomic fibers to the larynx, trachea, esophagus, pharynx, and inferior constrictor muscle amongst individuals, this may explain why we found high rates of dysphagia in patients from both groups even when no vocal cord paralysis were identified postoperatively. Impairment to the sensory or autonomic fibers alone may significantly impact swallowing in neonates, but more studies are needed to clarify this issue.

Conclusion

Unilateral vocal cord paralysis and dysphagia are highly prevalent after arch reconstruction, including the Norwood procedure. Dysphagia is prevalent in this population even when vocal cord motion is normal after cardiothoracic surgery, resulting in modified feeding regimen and potential need for gastrostomy tube placement. Our study demonstrated a lack of consistent routine surveillance for vocal cord function in patients after aortic arch repair. Further studies and continued surveillance of this population are necessary to assess resolution rates and complications.