Course, Predictors of Diaphragm Recovery After Phrenic Nerve Injury During Pediatric Cardiac Surgery

Interest of thoracic ultrasound after cardiac surgery or interventional cardiology

Thoracic ultrasound has attracted much interest in detecting pleural effusion or pulmonary consolidation after cardiac surgery. In 2016, Trovato reported, in the World Journal of Cardiology, the interest of using, in addition to echocardiography, thoracic ultrasound. In this editorial, we highlight the value of assessing diaphragm function after cardiac surgery and interventional cardiology procedures. Various factors are able to impair diaphragm function after such interventions. Diaphragm motion may be decreased by chest pain secondary to sternotomy, pleural effusion or impaired muscle function. Hemidiaphragmatic paralysis may be secondary to phrenic nerve damage complicating cardiac surgery or atrial fibrillation ablation. Diagnosis may be delayed. Indeed, respiratory troubles induced by diaphragm dysfunction are frequently attributed to pre-existing heart disease or pulmonary complications secondary to surgery. In addition, elevated hemidiaphragm secondary to diaphragm dysfunction is sometimes not observed on chest X-ray performed in supine position in the intensive care unit. Analysis of diaphragm function by ultrasound during the recovery period appears essential. Both hemidiaphragms can be studied by two complementary ultrasound methods. The mobility of each hemidiaphragms is measured by M-mode ultrasonography. In addition, recording the percentage of inspiratory thickening provides important information about the quality of muscle function. These two approaches make it possible to detect hemidiaphragm paralysis or dysfunction. Such a diagnosis is important because persistent diaphragm dysfunction after cardiac surgery has been shown to be associated with adverse respiratory outcome. Early respiratory physiotherapy is able to improve respiratory function through strengthening of the inspiratory muscles i.e. diaphragm and accessory inspiratory muscles.

A porcine model of postoperative hemi-diaphragmatic paresis to evaluate a unilateral diaphragmatic pacemaker

Unilateral phrenic nerve damage is a dreaded complication in congenital heart surgery. It has deleterious effects in neonates and children with uni-ventricular circulation. Diaphragmatic palsy, caused by phrenic nerve damage, impairs respiratory function, especially in new-borns, because their respiration depends on diaphragmatic contractions. Furthermore, Fontan patients with passive pulmonary perfusion are seriously affected by phrenic nerve injury, because diaphragmatic contraction augments pulmonary blood flow. Diaphragmatic plication is currently employed to ameliorate the negative effects of diaphragmatic palsy on pulmonary perfusion and respiratory mechanics. This procedure attenuates pulmonary compression by the abdominal contents. However, there is no contraction of the plicated diaphragm and consequently no contribution to the pulmonary blood flow. Hence, we developed a porcine model of unilateral diaphragmatic palsy in order to evaluate a diaphragmatic pacemaker. Our illustrated step-by-step description of the model generation enables others to replicate and use our model for future studies. Thereby, it might contribute to investigation and advancement of potential improvements for these patients.

Diagnostic Utility of Point-of-Care Ultrasound in the Pediatric Cardiac Intensive Care Unit

Purpose of Review

Recent Findings

Summary

Supplementary Information

Management of phrenic nerve injury post-cardiac surgery in the paediatric patient

BACKGROUND

Phrenic nerve injury is a common complication of cardiac and thoracic surgical procedures, with potentially severe effects on the health of a child. This review aims to summarise the available literature on the diagnosis and management of PNI post-cardiac surgery in paediatric patients with CHD.

MAIN BODY

The presence of injury post-surgery can be difficult to detect and may present with non-specific symptoms, emphasising the importance of an effective diagnostic strategy. Chest X-ray is usually the first investigation for a suspected diagnosis of PNI, which is usually confirmed using fluoroscopy, ultrasound scan, or phrenic nerve stimulation (gold standard). Management options include supportive ventilation and/or invasive diaphragmatic plication surgery. While the optimal timing of plication surgery remains controversial, it is now the most widely accepted treatment for PNI in children post-CHD surgery, especially for very young patients who cannot be weaned off supportive ventilation. Further research is needed to determine the optimal timing of surgical intervention for positive outcomes and to explore the benefits of using minimally invasive surgical techniques in children.

CONCLUSION

PNI is a common and serious complication of CHD surgery, therefore, its diagnosis and management in the paediatric population are of major importance. Further research is needed to determine the optimal timing of surgical intervention for positive outcomes and to explore the benefits of using minimally invasive surgical techniques in children.

Fluorographic findings of diaphragmatic paralysis with spontaneous recovery

BACKGROUND

Postoperative diaphragmatic paralysis is an unavoidable complication of cardiovascular surgery. Although diaphragmatic plication, as a surgical treatment, can be performed, spontaneous recovery is possible. We aimed to identify differences in fluorographic findings of diaphragmatic paralysis between pediatric patients with and without spontaneous recovery within 1 year of intrathoracic surgery.

METHODS

Ten children, who had been followed-up for at least 1 year post-surgery and who had not received diaphragmatic plication were included and classified into those with or without spontaneous recovery. The presence or absence of the paradoxical movement of the diaphragm and mediastinum was evaluated based on fluorographic findings. Fisher's exact test was used to compare the presence or absence of paradoxical movement between the groups.

RESULTS

Eight patients experienced spontaneous recovery. The mean ± standard deviation time to spontaneous recovery was 150 ± 114 days (range, 18-338 days). In the spontaneous recovery group, no patient had paradoxical movement of the mediastinum, and a significant between-group difference was observed in the presence of the paradoxical movement of the mediastinum (present/absent in patients with vs. without spontaneous recovery: 0/8 vs. 2/0, P = 0.02). There was no significant between-group difference in paradoxical movement of the diaphragm (present/absent in patients with vs. without spontaneous recovery: 1/7 vs. 2/0, P = 0.07). Pediatric patients without paradoxical movement of the mediastinum spontaneously recovered within 1 year of intrathoracic surgery.

CONCLUSIONS

Pediatric patients without paradoxical movement of the mediastinum, based on fluorography findings, spontaneously recovered within 1 year of surgery. The timing of spontaneous recovery varied between cases.

Outcome analysis of a conservative approach to diaphragmatic paralysis following congenital cardiac surgery in neonates and infants: a bicentric retrospective study

 

OBJECTIVES

Diaphragmatic paralysis following congenital cardiac surgery is associated with significant morbidity and mortality. Spontaneous recovery of diaphragmatic function has been described, contrasting with centres providing early diaphragmatic plication. We aimed to describe the outcomes of a conservative approach, as well as to identify factors associated with a failure of the strategy.

METHODS

This is a retrospective study of patients admitted after cardiac surgery and suffering unilateral diaphragmatic paralysis within 2 French Paediatric Cardiac Surgery Centers. The conservative approach, defined by the prolonged use of ventilation until successful weaning from respiratory support, was the primary strategy adopted in both centres. In case of unsuccessful evolution, a diaphragmatic plication was scheduled. Total ventilation time included invasive and non-invasive ventilation. Diaphragm asymmetry was defined by the number of posterior rib segments counted between the 2 hemi-diaphragms on the chest X-ray after cardiac surgery.

RESULTS

Fifty-one neonates and infants were included in the analysis. Patients' median age was 12.0 days at cardiac surgery (5.0-82.0), and median weight was 3.5 kg (2.8-4.9). The conservative approach was successful for 32/51 patients (63%), whereas 19/51 patients (37%) needed diaphragm plication. There was no difference in patients' characteristics between groups. Respiratory support prolonged for 21 days or more and diaphragm asymmetry more than 2 rib segments were independently associated with the failure of the conservative strategy [odds ratio (OR) 6.9 (1.29-37.3); P = 0.024 and OR 6.0 (1.4-24.7); P = 0.013, respectively].

CONCLUSIONS

The conservative approach was successful for 63% of the patients. We identified risk factors associated with the strategy's failure.

A novel sonographic sign of paradoxical movement of diaphragmatic paralysis in pediatric patients after cardiovascular surgery

We demonstrate a quick sliding of the descending aorta toward the unaffected side of the diaphragm as a new sonographic finding during breathing in pediatric patients with diaphragmatic paralysis. We present three pediatric patients with diaphragmatic paralysis after cardiovascular surgery with this new sonographic finding. This finding consisted of paradoxical movement of the diaphragm as shown by fluorography. This sonographic sign was only obtained by a B-mode scan in the subxiphoid plane, was easily demonstrated at the patient's bedside, and may be useful for diagnosing severe diaphragmatic paralysis.

Diaphragm Paralysis After Pediatric Cardiac Surgery: An STS Congenital Heart Surgery Database Study

BACKGROUND

Previous single-center studies of diaphragm paralysis (DP) after pediatric cardiac surgery report incidence of 0.3% to 12.8% and associate DP with respiratory complications, prolonged ventilation and length of stay, and mortality. To better define incidence and associations between DP and various procedures and outcomes, we performed a multicenter study.

METHODS

The Society of Thoracic Surgeons Congenital Heart Surgery Database was queried to identify children who experienced DP after cardiac surgery (2010-2018; 126 centers). Baseline characteristics and postoperative outcomes were compared between patients with and without DP as well as between patients who underwent plication and those who did not. Associations between center volume and center rates of DP and use of plication were also explored.

RESULTS

A total of 2214 of 191,463 (1.2%) patients experienced DP. Postoperative DP portended worse outcomes, including mortality (5.6% vs 3.5%; P < .001), major morbidity (37.2% vs 10.7%; P < .001), tracheostomy (7.1% vs 0.9%; P < .001), prolonged mechanical ventilation (38.0% vs 7.8%; P < .001), and 30-day readmission (22.0% vs 10.6%; P < .001). A total of 1105 of 2214 (49.9%) patients with DP underwent plication. Patients who underwent plication were younger, were smaller, had more risk factors, and underwent more complex surgeries. Plication rates varied widely across centers. There was no correlation between center volume and center risk-adjusted rates of DP (r = .05, P = .5), nor frequency of plication (r = .08, P = .4).

CONCLUSIONS

DP complicating pediatric heart surgery is rare but portends significantly worse outcomes. One-half of patients underwent plication. Center-level risk-adjusted rates of DP and plication are not associated with case volume. Significant variability in plication practices suggests a target for quality improvement.

Impact of prior diaphragm plication on subsequent stages of single ventricle palliation

BACKGROUND

Phrenic nerve injury is a known cause of morbidity after single ventricle palliation. Previous studies have shown that hemidiaphragm plication improves short-term outcomes. The effect of plication on the outcomes of subsequent stages of single ventricle palliation is unknown.

METHODS

From 1997 to 2015, 1146 patients underwent surgical management of single ventricle physiology at our institution. We reviewed the records of 30 patients who had undergone diaphragm plication for phrenic nerve injury before Fontan completion. Each patient was compared with 2 propensity-matched controls identified from patients who underwent the Glenn or Fontan procedure during the same period without diaphragm plication. Propensity matching was achieved for each test subject using the nearest neighbor algorithm. Data are presented as the median and quartiles or numbers and percentages.

RESULTS

The cohort included 18 boys (60%). Of the 30 patients, 19 (63%) had undergone plication after first-stage palliation. Of these, 13 have undergone completion Fontan, 5 were awaiting Fontan at the last follow-up, and 1 had died. An additional 11 patients had undergone plication after Glenn and proceeded to Fontan completion. Thus, 24 patients with diaphragm plication have undergone Fontan completion. No difference was found in pulmonary pressure or resistance between the plicated patients and their propensity-matched controls. Both groups had comparable chest tube output and hospital lengths of stay. Equal proportions of patients in both groups required pulmonary vasodilator therapy and/or supplemental oxygen at hospital discharge.

CONCLUSIONS

Prior diaphragm plication does not adversely affect Fontan completion in children with single ventricle physiology. The hospital course during subsequent stages of palliation for plicated patients was no different than that of matched controls.

Impact of Phrenic Nerve Palsy on Late Fontan Circulation

BACKGROUND

Although adverse effects of phrenic nerve palsy (PNP) on early Fontan circulation have been reported, detailed late impact remains unclear.

METHODS

Of 218 patients undergoing extracardiac total cavopulmonary connection between 1995 and 2008, 160 who all underwent cardiac catheter examination, spirometry, and exercise capacity testing 10 years after the operation were enrolled. The cohort was divided into 2 groups: with (N = 21) or without PNP (control group, N = 139). The patients with PNP were further divided into the recovered PNP group (n = 10) and the persistent PNP group (n = 11). All but 2 patients who developed PNP (90.9%) underwent diaphragmatic plication. There was no difference in hemodynamic indices at pre-Fontan evaluation among the three groups.

RESULTS

Ten years after the Fontan procedure, the averaged forced vital capacity was 81% ± 18% of predicted in the control group, 86% ± 17% in the recovered PNP group, and 56% ± 12% in the persistent PNP group (P < .001). Peak oxygen consumption was linearly correlated to the forced vital capacity (r = 0.222, P = .009). There was no significant difference in the peak oxygen consumption between groups. Significant veno-venous collaterals into the diaphragm from lower body to pulmonary vein(s) or atria more frequently developed in patients who underwent diaphragmatic plication compared with those who did not (P < .001).

CONCLUSIONS

Persistent PNP resulted in reduced forced vital capacity; however, its influence on exercise intolerance could not be identified. Diaphragmatic plication should be reserved for patients who experience clinically significant respiratory or hemodynamic sequelae of PNP.

Impact of Phrenic Nerve Palsy and Need for Diaphragm Plication Following Surgery for Pulmonary Atresia With Ventricular Septal Defect and Major Aortopulmonary Collaterals

Injury to the phrenic nerves may occur during surgery for pulmonary atresia with ventricular septal defect and major aortopulmonary collateral arteries (PA-VSD and MAPCAs). These patients may develop respiratory failure and require diaphragm plication. The purpose of this study was to evaluate the impact of phrenic nerve palsy on recovery following surgery for PA-VSD and MAPCAs. Between 2007 and 2016, approximately 500 patients underwent surgery for PA-VSD and MAPCAs at our institution. Twenty-four patients (4.8%) subsequently had evidence of new phrenic nerve palsy. Sixteen patients were undergoing their first surgical procedure, whereas 8 were undergoing reoperations. All 24 patients underwent diaphragm plication. A cohort of matched controls was identified based on identical diagnosis and procedures but did not sustain a phrenic nerve palsy. Eighteen of the 24 patients (75%) had clinical improvement following diaphragm plication as evidenced by the ability to undergo successful extubation (5 ± 2 days), transition out of the intensive care unit (32 ± 16 days), and discharge from the hospital (42 ± 19 days). In contrast, there were 6 patients (25%) who did not demonstrate a temporal improvement following diaphragm plication, as evidenced by intervals of 61 ± 38, 106 ± 45, and 108 ± 46 days, respectively (P < 0.05 for all 3 comparisons). The 6 patients who failed to improve following diaphragm plication had a significantly greater number of comorbidities compared to the 18 patients who demonstrated improvement (2.2 vs 0.6 per patient, P < 0.05). When compared with the control group, patients who improved following diaphragm plication spent an additional 22 days and patients who failed to improve an additional 90 days in the hospital. The data demonstrate a bifurcation of clinical outcome in patients undergoing diaphragm plication following surgery for PA-VSD and MAPCAs. This bifurcation appears to be linked to the presence or absence of other comorbidities.

Bilateral diaphragmatic paresis following pediatric liver transplantation

Background:

Although diaphragm paresis or paralysis is fairly common following cardiac procedures; it is a less common complication following liver transplantation. Unilateral diaphragm paresis, usually right sided, has been described following liver transplantation in adults and has been rarely described in children.

Purpose:

Diaphragmatic injury following LT is often unrecognized and is typically unilateral, involving the right hemidiaphragm. Bilateral diaphragm dysfunction following liver transplantation in children is a rare complication.

Methods:

This is a case report of bilateral diaphragm paresis in a young child following a repeat liver transplantation.

Conclusion:

Bilateral diaphragm paresis following liver transplantation in children is rare and spontaneous resolution is possible. A conservative approach with noninvasive ventilation as a first line treatment to allow the diaphragm to regain function should be considered.

Bedside Ultrasound for the Diagnosis of Abnormal Diaphragmatic Motion in Children After Heart Surgery

OBJECTIVE

To assess the utility of bedside ultrasound combining B- and M-mode in the diagnosis of abnormal diaphragmatic motion in children after heart surgery.

DESIGN

Prospective post hoc blinded comparison of ultrasound performed by two different intensivists and fluoroscopy results with electromyography.

SETTING

Tertiary university hospital.

SUBJECTS

Children with suspected abnormal diaphragmatic motion after heart surgery.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

Abnormal diaphragmatic motion was suspected in 26 children. Electromyography confirmed the diagnosis in 20 of 24 children (83.3%). The overall occurrence rate of abnormal diaphragmatic motion during the study period was 7.5%. Median patient age was 5 months (range, 16 d to 14 yr). Sensitivity and specificity of chest ultrasound performed at the bedside by the two intensivists (91% and 92% and 92% and 95%, respectively) were higher than those obtained by fluoroscopy (87% and 83%). Interobserver agreement (k) between both intensivists was 0.957 (95% CI, 0.87-100).

CONCLUSIONS

Chest ultrasound performed by intensivists is a valid tool for the diagnosis of diaphragmatic paralysis, presenting greater sensitivity and specificity than fluoroscopy. Chest ultrasound should be routinely used after pediatric heart surgery given its reliability, reproducibility, availability, and safety.

Reversible diaphragmatic paralysis caused by a malpositioned chest tube

We report a case of reversible diaphragmatic paralysis caused by a malpositioned chest tube, a diagnosis to consider when unexplained respiratory failure occurs following drainage of pleural effusion. Prompt recognition and removal of the tube led to full recovery of diaphragm function.

Impact of unilateral denervation on transdiaphragmatic pressure

The diaphragm muscle (DIAm) has a large reserve capacity for force generation such that in rats, the transdiaphragmatic pressure (Pdi) generated during ventilatory behaviors is less than 50% of maximal Pdi (Pd(imax)) elicited by bilateral phrenic nerve stimulation. Accordingly, we hypothesized that following unilateral denervation (DNV), the ability of the contralateral DIAm to generate sufficient Pdi to accomplish ventilatory behaviors will not be compromised and normal ventilation (as determined by arterial blood gas measurements) will not be impacted, although neural drive to the DIAm increases. In contrast, we hypothesized that higher force, non-ventilatory behaviors requiring Pdi generation greater than 50% of Pd(imax) will be compromised following DIAm hemiparalysis, i.e., increased neural drive cannot fully compensate for lack of force generating capacity. Pdi generated during ventilatory behaviors (eupnea and hypoxia (10% O2)-hypercapnia (5% CO2)) did not change after DNV and arterial blood gases were unaffected by DNV. However, neural drive to the contralateral DIAm, assessed by the rate of rise of root mean squared (RMS) EMG at 75 ms after onset of inspiratory activity (RMS75), increased after DNV (p<0.05). In contrast, Pdi generated during higher force, non-ventilatory behaviors was significantly reduced after DNV (p < 0.01), while RMS75 was unchanged. These findings support our hypothesis that only non-ventilatory behaviors requiring Pdi generation greater than 50% of Pd(imax) are impacted after DNV. Clinically, these results indicate that an evaluation of DIAm weakness requires examination of Pdi across multiple motor behaviors, not just ventilation.