Phrenic nerve injury following cardiac surgery: a review

Strategies to reduce morbidity following pleurectomy and decortication for malignant pleural mesothelioma

BACKGROUND

Pleurectomy and decortication (PD) in malignant pleural mesothelioma has a high morbidity mostly associated with aspiration pneumonia (PNA), deep vein thrombosis (DVT), and foreign catheter sepsis. We instituted four strategies to reduce these complications and report our experience.

METHODS

This was a retrospective review of patients who underwent PD at the University of Pennsylvania between 2015 and 2022. Our patients underwent standard of care PD in addition to tracheostomy and gastrostomy/jejunostomy tube with therapeutic anticoagulation (AC) leading up to surgery. Measured outcomes were postoperative PNA, DVT, and sepsis. The predicted risk of those same outcomes had patients not undergone the interventions was calculated based on the American College of Surgeons (ACS) surgical risk calculator (SRC). A McNemar's test was used to determine whether the risk of having PNA, DVT and sepsis differed between the two subgroups.

RESULTS

Fifty-five patients were included in the study. The mean age was 70 years (SD 6.2) with a mean of 21 (SD 19) pack-years of smoking. PNA, DVT, and catheter-related sepsis occurred in 12, four, and seven patients, respectively. Upon using the ACS SRC prediction model of the nonintervention group, PNA, DVT and catheter related sepsis was predicted to occur in 24 (paired data OR 5, 95% CI: 1.4-17.2; McNemar's test p = 0.008), 14 (paired data OR 3.5, 95% CI: 1.15-10.6; McNemar's test p = 0.03), and 17 (paired OR 3, 95% CI: 1.09-8.3; McNemar's test p = 0.04) patients, respectively.

DISCUSSION

Patients undergoing tracheostomy creation, therapeutic AC at the time of diagnosis, and gastrostomy tube placement had a reduced risk of aspiration PNA, DVT, and catheter sepsis.

Optimal prevention method of phrenic nerve injury in superior vena cava isolation: efficacy of high-power, short-duration radiofrequency energy application on the risk points

BACKGROUND OR PURPOSE

Superior vena cava isolation (SVCI) is widely performed adjunctively to atrial fibrillation (AF) ablation. Right phrenic nerve injury (PNI) is a complication of this procedure. The purpose of the study is to determine the optimal PNI prevention method in SVCI.

METHODS

A total of 1656 patients who underwent SVCI between 2009 and 2022 were retrospectively examined. PNI was diagnosed based on the diaphragm position and movement in the upright position on chest radiographs before and after SVCI.

RESULTS

With the introduction of various PN monitoring systems over the years, the incidence of SVCI-associated PNI has decreased. However, complete PNI avoidance has not been achieved. PNI incidence according to fluoroscopy-guided PN monitoring, high-output pace-guided, compound motor action potential-guided, and 3-dimensional electro-anatomical mapping (EAM) systems was 8.1% (38/467), 2.7% (13/476), 2.4% (4/130), and 2.8% (11/389), respectively. However, a high-power, short-duration (50 W/7 s) radiofrequency (RF) energy application only on PNI risk points tagged by a 3-dimensional EAM system completely avoids PNI (0%; 0 /160 since April 2021). PNI showed no symptoms and recovered within an average of 188 days post-SVCI, except for a few patients who required > 1 year.

CONCLUSIONS

Although PNI incidence decreased annually with the introduction of various monitoring systems, these monitoring systems did not prevent PNI completely. Most notably, the delivery of a high-power, short-duration RF energy only on risk points tagged by EAM prevented PNI completely. PNI recovered in all patients. The application of higher-power, shorter-duration RF energy on risk points tagged by EAM appears to be an optimal PNI prevention maneuver.

Common Focal Neuropathies in the Hospitalized Patient

Neuropathies are a common problem encountered by neurologist in the hospitalized setting. Nerve injury may occur secondary to compression, stretch, and direct trauma, among other causes. Common focal neuropathies include the ulnar, median, and radial nerve in the upper extremities and sciatic, peroneal, and femoral nerve in the lower extremities. Surgical and obstetric risk factors are especially important considerations in evaluation of patients with focal neuropathies. Treatment is either conservative therapy or surgery depending on the mechanism of injury and extent of recovery.

A prospective evaluation of phrenic nerve injury after lung transplantation: Incidence, risk factors, and analysis of the surgical procedure

BACKGROUND

Phrenic nerve injury (PNI) is a complication of lung transplantation related to the surgical procedure and associated with increased morbidity. However, the incidence and risk factors, specifically regarding surgical techniques, have not been adequately studied.

METHODS

We conducted a prospective single-center study over 4-years, in recipients of lung transplantation with a normal pretransplant phrenic nerve conduction study (PNCS). Diaphragm ultrasound and PNCS were performed in the first 21 postoperative days and PNI was defined when both tests were abnormal. Patients were followed up until hospital discharge. The association between transplant characteristics and PNI was analyzed by using logistic regression models.

RESULTS

Two hundred eleven lung grafts implanted in 127 patients were included in the study. After lung transplantation, PNI was diagnosed in 43.3% of the subjects and 29% of the operated hemithorax. Regression logistic model showed that the variables related to PNI were female gender (p = 0.02), bilateral lung transplantation (BLT) (p = 0.001), right lung graft (p = 0.003), clamshell incision (p = 0.01), mediastinal adhesions (p = 0.002), longer operative time (p = 0.003), intraoperative extracorporeal support (p = 0.02), and blood transfusion (p = 0.003). Conversely, age >61 years (p = 0.008) and higher thoracic diameter (p = 0.04) were protective factors. The use of electrocautery, cardiac mechanical retractors, and diaphragmatic traction was not associated with PNI. Morbidity was increased without any difference in mortality.

CONCLUSIONS

PNI is a frequent complication after lung transplantation, associated with higher morbidity. Mainly risk factors were age, BLT, female gender, and variables related to surgical difficulties. Lung graft in the right hemithorax and mediastinal adhesiolysis were the most relevant technical variables.

Pulmonary Complications of Cardiac Surgery

Cardiothoracic surgery posits an arrangement of large, significant hemodynamic, and physiologic alterations upon the human body, which predisposes a patient to develop pathology. The care of these patients in the postoperative realm requires an astute physician with deep understanding of the cardiopulmonary system, who is able to address subtle developing problems promptly, before the patient suffers further sequelae. In this review, we describe the presentation and management of an assortment of important complications which occur in the pulmonary system. In addition, we aim to shed better light upon how the physiology of a patient responds to the condition of cardiothoracic surgery.

Osteopathic treatment leads to significantly greater reductions in chronic thoracic pain after CABG surgery: A randomised controlled trial

BACKGROUND

There are a number of long-term postoperative complications after coronary artery bypass graft (CABG) surgery. Pulmonary function is decreased by 12% and 30%-50% of the patients have chronic thoracic pain.

METHODS

This randomised controlled trial with two parallel groups aimed to explore the effectiveness of osteopathic treatments (OTs) on these conditions. The standard care (SC) group and the and OT group received a 12-week standard cardiac rehabilitation programme, which was supplemented with four OTs for the OT group only. The outcome assessors were blinded to the patients' allocation.

RESULTS

Eighty-two patients with median sternotomy after CABG surgery were randomly allocated in a 1:1 ratio (SC: n = 42, OT: n = 42). Slow vital capacity and pain intensity were measured at baseline and at 12 weeks and 52 weeks after surgery. Pain intensity was significantly lower in the OT group 12 weeks after surgery (3.6-0.80 vs. 2.6 to 1.2, p = 0.030). One year after surgery, there still was a significantly lower pain intensity in the OT group (3.6-0.56, vs. 2.6 to 1.2, p = 0.014). No significant changes between groups were found in pulmonary function. There were no adverse events reported.

CONCLUSIONS

From this study, it can be concluded that the addition of OT to exercise-based cardiac rehabilitation may lead to significantly greater reductions in thoracic pain after CABG surgery.

TRIAL REGISTRATION

This study was registered on ClinicalTrials.gov (NCT01714791).

[Diaphragm relaxation surgery]

AIM

To develop examination algorithm and to determine the indications for various options for surgical treatment.

MATERIAL AND METHODS

It is presented analysis of surgical treatment of 25 patients with unilateral diaphragm relaxation for the period from 1963 to 2016. There were 15 men and 10 women aged from 39 to 65 years. Diagnosis included predominantly radiological methods. All patients were operated openly through thoracotomy. Procedure consisted of creation of new diaphragmatic cupola at the usual level with two flaps of diaphragm and prosthesis between them. In 12 (48%) patients who were operated before 1990 xenopericardial patch was used. Further, synthetic materials (Teflon, polypropylene) were preferred.

RESULTS

Postoperative morbidity and mortality was 20% (n=6) and 4% (n=1) respectively. Long-term results were followed-up within terms from 8 months to 12 years. Recurrent relaxation was absent. Most of patients had improved dyspnea, increased vital capacity and FEV1 in long-term period. Certain and general values of SF-36 life quality questionnaire were high in long-term postoperative period and similar to those in general population.

Effects of osteopathic treatment on pulmonary function and chronic thoracic pain after coronary artery bypass graft surgery (OstinCaRe): study protocol for a randomised controlled trial

Background

Coronary artery bypass graft surgery (CABG) is an effective and widespread coronary revascularisation technique, nevertheless there are a number of long-term postoperative complications from which patients can suffer. One year after CABG surgery pulmonary function is decreased by 12% and 30% of the patients suffer from chronic thoracic pain. To date and to our knowledge there are no effective treatments for these conditions. The aim of the present clinical trial is to explore the effectiveness of osteopathic treatment on these conditions.

Methods

The study is designed as a randomised controlled trial with two parallel groups. Group A will receive a standard cardiac rehabilitation programme during 12 weeks and group B will receive the same standard cardiac rehabilitation programme supplemented with four osteopathic treatments (OT). OT will be performed at week 4, 5, 8 and 12 after surgery. Three hundred and eight patients (Group A: n = 154, Group B: n = 154) will be enrolled from the cardiothoracic surgery department of the Jessa Hospital Hasselt. Blinding will be assured for the staff of the cardiac rehabilitation centre and outcome assessors. Primary outcome measure will be the mean difference in change from baseline in slow vital capacity (SVC) at 12 weeks after surgery between groups. Secondary outcome measures will be the change from baseline in quality of life, pain, thoracic stiffness and maximal aerobic capacity at 12 weeks after surgery. A follow-up is planned 52 weeks after surgery for SVC, quality of life, pain and thoracic stiffness. Intention to treat analysis will be executed.

Discussion

The OstinCare study has been designed to explore the potential long-term added value of osteopathic treatment in the management of decreased pulmonary function, chronic thoracic pain and diminished thoracic mobility after CABG surgery.

Trial registration

The protocol has been retrospectively registered on ClinicalTrials.gov (NCT01714791).

Routine postoperative care of patients undergoing coronary artery bypass grafting on cardiopulmonary bypass

The postoperative course of a patient undergoing cardiac surgery (CS) is dictated by a largely predictable set of interactions between disease-specific and therapeutic factors. ICU personnel need to quickly develop a detailed understanding of the patient's current status and how critical care resources can be used to promote further recovery and eventual independence from external support. The goal of this article is to describe a typical operative and postoperative course, with emphasis on the latter, and the diagnostic and therapeutic options necessary for the proper care of these patients. This paper will focus on coronary artery bypass grafting as a model for understanding the course of CS patients; however, many of the principles discussed are applicable to most cardiac surgery patients.

Effects of topical hypothermia on postoperative inflammatory markers in patients undergoing coronary artery bypass surgery

Background

We aimed to examine the effects of topical hypothermia on inflammatory markers in patients undergoing coronary artery bypass surgery.

Methods

Fifty patients undergoing isolated coronary artery bypass surgery were included the study. They were randomised to two groups. Mild hypothermic cardiopulmonary bypass (28–32°C) was performed on both groups using standardised anaesthesiology and surgical techniques. Furthermore, topical cooling with 4°C saline was performed on patients in group I. We recorded peri-operative and intra-operative results of blood samples, pre-operative and postoperative outcomes of electrocardiography and echocardiography, diaphragm levels on X-ray, and the necessity of positive inotropic medication and intra-aortic balloon pump (IABP).

Results

Time-dependent changes in blood samples were compared between the two groups. The changes on complement 3 (C3) and TNF-α levels were more significant in group I than group II (p < 0.05 and p < 0.001, respectively). Spontaneous restoration rate of sinus rhythm was higher in group II than group I (80 vs 32%, p < 0.01). Atrial fibrillation was seen in six patients in group I and one patient in group II (p < 0.05). IABP was performed on four patients (16%) in group I (p < 0.05). Diaphragmatic paralysis was seen in seven patients in group I but not in group II (p < 0.01). Partial pericardiotomy rates were compared within the groups but there was no statistically significant difference (p > 0.05). One patient in group I died on the 18th postoperative day, but operative mortality rate was not statistically significant between the two groups (p > 0.05).

Conclusions

Topical hypothermia had a negative impact on inflammatory markers and postoperative morbidities.

Is video-assisted thoracoscopic diaphragmatic plication a widespread technique for diaphragmatic hernia in adults? Review of the literature and results of a national survey

Diaphragmatic plication is the most accepted treatment for symptomatic diaphragmatic hernia in adults. The fact that this pathology is infrequent and this procedure not been widespread means that this is an exceptional technique in our field. To estimate its use in the literature, we carried out a review in English and Spanish, to which we added our series. We found only six series that contribute 59 video-assisted mini-thoractomy for diaphragmatic plications in adults, and none in Spanish. Our series will be the second largest with 18 cases. Finally, we conducted a survey in all the Spanish Thoracic Surgery units in Spain: none reported more than 10 cases operated by thoracoscopy in the last 8 years (except our series) and most continue employing thoracotomy as the main approach. We believe that many patients with symptomatic diaphragmatic hernia could benefit from the use of such techniques.

Neuroanatomic considerations in percutaneous tumor ablation

Percutaneous ablation is increasingly being used as focal therapy for tumors in the chest, abdomen, and pelvis, including tumors in proximity to neural structures. To ensure that tumor ablation is performed safely, knowledge of the regional neuroanatomy is particularly important because most relevant nerves are not visualized with the conventional imaging techniques used to guide ablation procedures. Familiarity with the expected course of nerves in commonly targeted areas is helpful in preventing inadvertent nerve injury and in accurately informing the patient of potential risks. In the chest and shoulder girdle, the brachial plexus as well as the phrenic, recurrent laryngeal, intercostal-subcostal, long thoracic, dorsal scapular, and suprascapular nerves may be encountered. Vulnerable neural structures in the abdomen and pelvis arise from the lumbar and sacral plexuses and include the femoral, obturator, sciatic, and pudendal nerves. Nerve protection and monitoring techniques should be used, when appropriate, to minimize the risk of neural injury during percutaneous tumor ablation and depend on the vulnerable nerve, the location of the targeted tumor, and the ablation device used for treatment. Nerves may be protected using displacement techniques, including instillation of air or fluid, insertion and insufflation of angioplastic or endoscopic balloons, and mechanical manipulation of the ablation device. Nerves may be monitored with cross-sectional imaging evaluation of the critical nerve or ablation zone, or with functional evaluation using electromyographic equipment or focused clinical examination. Supplemental material available at http://radiographics.rsna.org/lookup/suppl/doi:10.1148/rg334125141/-/DC1.

Early hemi-diaphragmatic plication through a video assisted mini-thoracotomy in postcardiotomy phrenic nerve paresis

New symptom onset of respiratory distress without other cause, and new hemi-diaphragmatic elevation on chest radiography postcardiotomy, are usually adequate for the diagnosis of phrenic nerve paresis. The symptom severity varies (asymptomatic state to severe respiratory failure) depending on the degree of the lesion (paresis vs. paralysis), the laterality (unilateral or bilateral), the age, and the co-morbidity (respiratory, cardiac disease, morbid obesity, etc). Surgical treatment (hemi-diaphragmatic plication) is indicated only in the presence of symptoms. The established surgical treatment is plication of the affected hemidiaphragm which is generally considered safe and effective. Several techniques and approaches are employed for diaphragmatic plication (thoracotomy, video-assisted thoracoscopic surgery, video-assisted mini-thoracotomy, laparoscopic surgery). The timing of surgery depends on the severity and the progression of symptoms. In infants and young children with postcardiotomy phrenic nerve paresis the clinical status is usually severe (failure to wean from mechanical ventilation), and early plication is indicated. Adults with postcardiotomy phrenic nerve paresis usually suffer from chronic dyspnoea, and, in the absence of respiratory distress, conservative treatment is recommended for 6 months -2 years, since improvement is often observed. Nevertheless, earlier surgical treatment may be indicated in non-resolving respiratory failure. We present early (25(th) day postcardiotomy) right hemi-diaphragm plication, through a video assisted mini-thoracotomy in a high risk patient with postcardiotomy phrenic nerve paresis and respiratory distress. Early surgery with minimal surgical trauma, short operative time, minimal blood loss and postoperative pain, led to fast rehabilitation and avoidance of prolonged hospitalization complications. The relevant literature is discussed.

Risk factors for pulmonary complications following cardiac surgery with cardiopulmonary bypass

BACKGROUND

Pulmonary complications following cardiac surgery with cardiopulmonary bypass (CPB) are often associated with significant morbidity and mortality. However, few reports have focused on evaluating intra- and post-operative independent risk factors for pulmonary complications following cardiac surgery with CPB. This study aimed to evaluate peri-operative independent risk factors for postoperative pulmonary complications through investigating and analyzing 2056 adult patients undergoing cardiac surgery with CPB.

METHODS

From January 2005 to December 2012, the relevant pre-, intra-, and post-operative data of adult patients undergoing cardiac surgery with CPB in the department of cardiovascular surgery of Tongji Hospital of Tongji University in Shanghai were investigated and retrospectively analyzed. The independent risk factors for pulmonary complications following cardiac surgery with CPB were obtained through descriptive analysis and then logistic regression analysis.

RESULTS

One hundred and forty-three adult patients suffered from pulmonary complications following cardiac surgery with CPB, with an incidence of 6.96%. Through descriptive analysis and then logistic regression, independent risk factors for postoperative pulmonary complications were as follows: older age (>65 years) (OR=3.31, 95%CI 1.71-7.13), preoperative congestive heart failure (OR=2.95, 95%CI 1.41-5.84), preoperative arterial oxygenation (PaO2) (OR=0.67, 95%CI 0.33-0.85), duration of CPB (OR=3.15, 95%CI 1.55-6.21), intra-operative phrenic nerve injury (OR=4.59, 95%CI 2.52-9.24), and postoperative acute kidney injury (OR=3.21, 95%CI 1.91-6.67). Postoperative pulmonary complication was not a risk factor for hospital death (OR=2.10, 95%CI 0.89-4.33).

CONCLUSIONS

A variety of peri-operative factors increased the incidence of pulmonary complications following cardiac surgery with cardiopulmonary bypass.

Reinnervation of the paralyzed diaphragm: application of nerve surgery techniques following unilateral phrenic nerve injury

BACKGROUND

Unilateral phrenic nerve injury often results in symptomatic hemidiaphragm paralysis, and currently few treatment options exist. Reported etiologies include cardiac surgery, neck surgery, chiropractic manipulation, and interscalene nerve blocks. Although diaphragmatic plication has been an option for treatment, the ideal treatment would be restoration of function to the paralyzed hemidiaphragm. The application of peripheral nerve surgery techniques for phrenic nerve injuries has not been adequately evaluated.

METHODS

Twelve patients presenting with long-term, symptomatic, unilateral phrenic nerve injuries following surgery, chiropractic manipulation, trauma, or anesthetic blocks underwent a comprehensive evaluation, including radiographic and electrophysiologic assessments. Surgical treatment was offered following a minimum of 6 months of conservative management. Operative planning was based on preoperative and intraoperative testing using one or more established nerve reconstruction techniques (neurolysis, interpositional grafting, or neurotization).

RESULTS

Measures of postoperative improvement included pulmonary function testing, fluoroscopic sniff testing, and a standardized quality-of-life survey, from which it was determined that eight of nine patients who could be completely evaluated experienced improvements in diaphragmatic function.

CONCLUSIONS

Based on the favorable results in this small series, we suggest expanding nerve reconstruction techniques to phrenic nerve injury treatment and propose an algorithm for treatment of unilateral phrenic nerve injury that may expand the current limitations in therapy.

Mini-open anterior instrumentation with diaphragm sparing for thoracolumbar idiopathic scoliosis: its technique and clinical results

The traditional method of thoracoabdominal retroperitoneal approach requires dissection of diaphragm which bears potential complications such as postoperatively weakened abdominal breathing and dysfunction of diaphragm. Mini-open anterior instrumentation with diaphragm sparing is designed to minimize the damage to diaphragm and improve cosmesis. This study compared the traditional anterior instrumentation and mini-open anterior instrumentation under the hypothesis that both results in similar surgical outcomes in treating thoracolumbar scoliosis. In Group A, 38 patients with an average age of 16.5 years underwent mini-open anterior instrumentation with diaphragm sparing. The average standing coronal Cobb angle was 56.4° in Group A. Thirty-eight patients with average age of 16.7 years in Group B received traditional open approach. The preoperative average Cobb angle was 55.8° in Group B. The average correction rate of coronal curve was 78% in group A while 75% in group B. No statistical difference between the two groups in terms of coronal curve correction, sagittal profile restoration and estimated blood loss was observed. The operation time was significantly higher in Group A than that in Group B. All patients in the two groups had good healing of incisions without neurological and instrumental complications during minimal 2 year follow-up. In Groups A and B, two patients suffered from pleural effusion, respectively. The wedging of the vertebral discs distal to the lowest fused level occurred in three and four patients in Group A and B, respectively. One case in group B was found to be suspicious pseudoarthrosis without loss of correction. Mini-open anterior instrumentation with diaphragm sparing could minimize the surgical invasion as well as achieve similar clinical outcomes compared with classical anterior approach.

Can lung volumes and capacities be used as an outcome measure for phrenic nerve recovery after cardiac surgeries?

Phrenic nerve is the main nerve drive to the diaphragm and its injury is a well-known complication following cardiac surgeries. It results in diaphragmatic dysfunction with reduction in lung volumes and capacities. This study aimed to evaluate the objectivity of lung volumes and capacities as an outcome measure for the prognosis of phrenic nerve recovery after cardiac surgeries. In this prospective experimental study, patients were recruited from Cardio-Thoracic Surgery Department, Educational-Hospital of College of Medicine, Cairo University. They were 11 patients with right phrenic nerve injury and 14 patients with left injury. On the basis of receiving low-level laser irradiation, they were divided into irradiated group and non-irradiated group. Measures of phrenic nerve latency, lung volumes and capacities were taken pre and post-operative and at 3-months follow up. After 3 months of low-level laser therapy, the irradiated group showed marked improvement in the phrenic nerve recovery. On the other hand, vital capacity and forced expiratory volume in the first second were the only lung capacity and volume that showed improvement consequent with the recovery of right phrenic nerve (P value <0.001 for both). Furthermore, forced vital capacity was the single lung capacity that showed significant statistical improvement in patients with recovered left phrenic nerve injury (P value <0.001). Study concluded that lung volumes and capacities cannot be used as an objective outcome measure for recovery of phrenic nerve injury after cardiac surgeries.

Long-term results of diaphragmatic plication in adults with unilateral diaphragm paralysis

BACKGROUND

In this study we aimed to evaluate the long-term outcome of diaphragmatic plication for symptomatic unilateral diaphragm paralysis.

METHODS

Thirteen patients who underwent unilateral diaphragmatic plication (2 patients had right, 11 left plication) between January 2003 and December 2006 were evaluated. One patient died postoperatively due to sepsis. The remaining 12 patients [9 males, 3 females; mean age 60 (36-66) years] were reevaluated with chest radiography, flouroscopy or ultrasonography, pulmonary function tests, computed tomography (CT) or magnetic resonance imaging (MRI), and the MRC/ATS dyspnea score at an average of 5.4 (4-7) years after diaphragmatic plication.

RESULTS

The etiology of paralysis was trauma (9 patients), cardiac by pass surgery (3 patients), and idiopathic (1 patient). The principle symptom was progressive dyspnea with a mean duration of 32.9 (22-60) months before surgery. All patients had an elevated hemidiaphragm and paradoxical movement radiologically prior to surgery. There were partial atelectasis and reccurent infection of the lower lobe in the affected side on CT in 9 patients. Atelectasis was completely improved in 9 patients after plication. Preoperative spirometry showed a clear restrictive pattern. Mean preoperative FVC was 56.7 ± 11.6% and FEV1 65.3 ± 8.7%. FVC and FEV1 improved by 43.6 ± 30.6% (p < 0.001) and 27.3 ± 10.9% (p < 0.001) at late follow-up. MRC/ATS dyspnea scores improved 3 points in 11 patients and 1 point in 1 patient at long-term (p < 0.0001). Eight patients had returned to work at 3 months after surgery.

CONCLUSIONS

Diaphragmatic plication for unilateral diaphragm paralysis decreases lung compression, ensures remission of symptoms, and improves quality of life in long-term period.

Effect of tDCS with an extracephalic reference electrode on cardio-respiratory and autonomic functions

Background

Transcranial direct current stimulation (tDCS) is used in human physiological studies and for therapeutic trials in patients with abnormalities of cortical excitability. Its safety profile places tDCS in the pole-position for translating in real-world therapeutic application. However, an episode of transient respiratory depression in a subject receiving tDCS with an extracephalic electrode led to the suggestion that such an electrode montage could modulate the brainstem autonomic centres.

We investigated whether tDCS applied over the midline frontal cortex in 30 healthy volunteers (sham n = 10, cathodal n = 10, anodal n = 10) with an extracephalic reference electrode would modulate brainstem activity as reflected by the monitoring and stringent analysis of vital parameters: heart rate (variability), respiratory rate, blood pressure and sympatho-vagal balance.

We reasoned that this study could lead to two opposite but equally interesting outcomes: 1) If tDCS with an extracephalic electrode modulated vital parameters, it could be used as a new tool to explore the autonomic nervous system and, even, to modulate its activity for therapeutic purposes. 2) On the opposite, if applying tDCS with an extracephalic electrode had no effect, it could thus be used safely in healthy human subjects. This outcome would significantly impact the field of non-invasive brain stimulation with tDCS. Indeed, on the one hand, using an extracephalic electrode as a genuine neutral reference (as opposed to the classical "bi-cephalic" tDCS montages which deliver bi-polar stimulation of the brain) would help to comfort the conclusions of several modern studies regarding the spatial location and polarity of tDCS. On the other hand, using an extracephalic reference electrode may impact differently on a given cortical target due to the change of direct current flow direction; this may enlarge the potential interventions with tDCS.

Results

Whereas the respiratory frequency decreased mildly over time and the blood pressure increased steadily, there was no differential impact of real (anodal or cathodal) versus sham tDCS. The heart rate remained stable during the monitoring period. The parameters reflecting the sympathovagal balance suggested a progressive shift over time favouring the sympathetic tone, again without differential impact of real versus sham tDCS.

Conclusions

Applying tDCS with an extracephalic reference electrode in healthy volunteers did not significantly modulate the activity of the brainstem autonomic centres. Therefore, using an extracephalic reference electrode for tDCS appears safe in healthy volunteers, at least under similar experimental conditions.

Respiratory movements are altered three months and one year following cardiac surgery

OBJECTIVE

Pulmonary complications following cardiac surgery through sternotomy are well known, but little is known about the proposed alterations of the chest wall mechanism. The purpose of this study was to examine changes in chest wall motion and pulmonary function after cardiac surgery.

DESIGN

The subjects were 20 cardiac surgery patients, 13 men and 7 women, mean age 65 years.

MEASUREMENTS

Bilateral respiratory movements were measured using the Respiratory Movement Measuring Instrument before, 3 and 12 months after the operation. Vital capacity (VC), forced vital capacity (FVC) and forced expiratory volume (FEV1) were measured with the Pulminet III (Gold Godart Ltd Vitalograph Alpha Ltd. Maids Morton, Buckingham, England) preoperatively, 3 and 12 months postoperatively, and radiographs were taken at the same points in time.

ANALYSIS

Descriptive statistics, paired sample t-tests, Mann-Whitney and Wilcoxon Signed Rank tests were used for analyses, p < or = 0.05.

RESULTS

Average abdominal movements 3 months postoperatively were significantly decreased and the difference between right and left side in upper thoracic and abdominal movements was significant. All pulmonary function measurements except the FEV1/FVC showed a significant decrease and a restrictive pattern compared with preoperative values. Twelve months after the operation the upper thoracic movements were significantly increased. Five patients had an abnormal chest x-ray before the operation, eight 3 months and three 12 months after the operation.

CONCLUSION

The motor system of the respiratory organs suffers considerable injury from cardiac surgery, which in part at least can explain the restrictive breathing 3 months postoperatively.

Chest wall motion and pulmonary function are more diminished following cardiac surgery when the internal mammary artery retractor is used

OBJECTIVES

Pulmonary complications following cardiac surgery through sternotomy have been widely studied. The duration of these complications, however, has been less studied and the proposed alterations in chest wall mechanism even less. The purpose of this study was to investigate changes in chest wall motion and pulmonary function of cardiac surgery patients, where both the median and the internal mammary artery retractor was used (IMA group) and cardiac surgery patients, where only the median retractor was used (Median group).

DESIGN

Subjects were 20 cardiac surgery patients with mean age 65 years (12 in the IMA group and 8 in the Median group). Bilateral respiratory movements (RMs) using the Respiratory Movement Measuring Instrument, lung volumes including vital capacity (VC), forced vital capacity (FVC) and forced expiratory volume (FEV1) using the Vitalograph Alpha were measured and pulmonary radiographs analyzed before, 3 and 12 months after the operation.

ANALYSIS

Descriptive statistics, t-tests, Mann-Whitney and Wilcoxon Signed Rank tests were used for analyses, p < or = 0.05.

RESULTS

RMs were symmetrical in both groups prior to the operation and the differences in RMs and lung volumes between the groups were not significant. Three and 12 months postoperatively bilateral abdominal respiratory movements (ARM) were significantly less in the IMA group than in the Median group. Average left ARM were significantly less than the average right ARM in the IMA group 3 months postoperatively, while symmetrical in the Median group. Average FVC and FEV1 were significantly less in the IMA group than in the Median group 3 months postoperatively and FVC was still significantly less in the IMA group 12 months after the operation.

CONCLUSION

The significantly more reduced ARM and lung volumes 3 months postoperatively in the IMA group than in the Median group suggests that the IMA retractor causes greater injury to the rib cage and the diaphragm.

Correlation of respiratory activity of contralateral diaphragm muscles for evaluation of recovery following hemiparesis

Respiration is impaired by disruption of the central drive for inspiration to the diaphragm muscle (DIAm). Some function may recover involving nerve regeneration, reinnervation or neuroplasticity. A research animal model involves inducing hemiparesis of the DIAm and monitoring any recovery under different conditions. Methods to accurately track the level of functional recovery are needed. In this study, an algorithm was developed and tested to quantify the relative amount of electromyogram (EMG) activity that temporally correlated for an experimental (EXP) hemi-DIAm with its intact contralateral hemi-DIAm. An average rectified value (ARV) trace was calculated. A template was formed of the ARV trace of the intact hemi-DIAm, with higher positive values corresponding with periods of inspirations and lower negative values corresponding with quiet periods. This template was multiplied by the EXP ARV trace to reward (more positive) periods of correlating activity, and punish (more negative) periods of high activity on the EXP side that corresponded with quiet periods on the intact side. The average integrated value was the index of correlating contralateral activity (I(CCA)). A negative I(CCA) value indicated no net correlation of activity, and a positive value indicated a net correlation of activity. The algorithm was tested on rats having the conditions of control or hemi-paresis induced by denervatation (DNV), tetrodotoxin administration (TTX) or cervical spinal hemi-section (SH). Control had high positive I(CCA) values, and DNV had negative values. TTX maintained negative I(CCA) values at 3, 7 and 14 days, indicating a lack of functional recovery. SH maintained negative values at 3 and 7 days, but a subset had positive values at 14 days indicating some functional recovery.

Nerve and Conduction Tissue Injury Caused by Contact with BioGlue

BACKGROUND

BioGlue-a surgical adhesive composed of bovine albumin and glutaraldehyde-is commonly used in cardiovascular operations. The objectives of this study were to determine whether BioGlue injures nerves and cardiac conduction tissues, and whether a water-soluble gel barrier protects against such injury.

MATERIALS AND METHODS

In 18 pigs, diaphragmatic excursion during direct phrenic nerve stimulation was measured at baseline and at 3 and 30 min after nerve exposure to albumin (n = 3), glutaraldehyde (n = 3), BioGlue (n = 6), or water-soluble gel followed by BioGlue (n = 6). Additionally, BioGlue was applied to the cavoatrial junction overlying the sinoatrial node (SAN), either alone (n = 12) or after application of gel (n = 6).

RESULTS

Mean diaphragmatic excursions in the BioGlue and glutaraldehyde groups were lower at 3 min and 30 min than in the albumin group (P < 0.05). Mean excursions in the gel group were similar to those of the albumin group (P = 0.9). Five BioGlue pigs (83%) and one gel pig (17%) had diaphragmatic paralysis by 30 min (P < 0.05 and P = 0.3 versus albumin, respectively). Coagulation necrosis extended into the myocardium at the cavoatrial junction in all 12 BioGlue pigs but only two gel pigs (33%, P < 0.01). Two BioGlue pigs (17%), but no gel pigs, had focal SAN degeneration and persistent bradycardia (P < 0.01).

CONCLUSIONS

BioGlue causes acute nerve injury and myocardial necrosis that can lead to SAN damage. A water-soluble gel barrier is protective.

Diaphragm plication in adult patients with diaphragm paralysis leads to long-term improvement of pulmonary function and level of dyspnea

OBJECTIVE

There is still controversy about the feasibility and long-term outcome of surgical treatment of acquired diaphragm paralysis. We analyzed the long-term effects on pulmonary function and level of dyspnea after unilateral or bilateral diaphragm plication.

METHODS

Between December 1996 and January 2006, 22 consecutive patients underwent diaphragm plication. Before surgery, spirometry in both seated and supine positions and a Baseline Dyspnea Index were assessed. The uncut diaphragm was plicated as tight as possible through a limited lateral thoracotomy. Patients with a follow-up exceeding 1 year (n=17) were invited for repeat spirometry and assessment of changes in dyspnea level using the Transition Dyspnea Index (TDI).

RESULTS

Mean follow-up was 4.9 years (range 1.2-8.7). All spirometry variables showed significant improvement. Mean vital capacity (VC) in seated position improved from 70% (of predicted value) to 79% (p<00.03), and in supine position from 54% to 73% (p=0.03). Forced expiratory volume in 1s (FEV1) in supine position improved from 45% to 63% (p=0.02). Before surgery the mean decline in VC changing from seated to supine position was 32%. At follow-up this had improved to 9% (p=0.004). For FEV1 these values were 35% and 17%, respectively (p<0.02). TDI showed remarkable improvement of dyspnea (mean+5.69 points on a scale of -9 to +9).

CONCLUSION

Diaphragm plication for single- or double-sided diaphragm paralysis provides excellent long-term results. Most patients were severely disabled before surgery but could return to a more or less normal way of life afterwards.

Experimental repair of phrenic nerve using a polyglycolic acid and collagen tube

OBJECTIVE

The feasibility of a nerve guide tube for regeneration of the phrenic nerve with the aim of restoring diaphragmatic function was evaluated in a canine model.

METHODS

The nerve tube, made of woven polyglycolic acid mesh, had a diameter of 3 mm and was filled with collagen sponge. This polyglycolic acid-collagen tube was implanted into a 10-mm gap created by transection of the right phrenic nerve in 9 beagle dogs. The tubes were implanted without a tissue covering in 5 of the 9 dogs (group I), and the tubes were covered with a pedicled pericardial fat pad in 4 dogs (group II). Chest x-ray films, muscle action potentials, and histologic samples were examined 4 to 12 months after implantation.

RESULTS

All of the dogs survived without any complications. x-ray film examination showed that the right diaphragm was paralyzed and elevated in all dogs until 3 months after implantation. At 4 months, movement of the diaphragm in the implanted side was observed during spontaneous breathing in 1 dog of group I and in 3 dogs of group II. In the dogs showing diaphragm movement, muscle action potentials were evoked in the diaphragm muscle, indicating restoration of nerve function. Regeneration of the phrenic nerve structure was also examined on the reconstructed site using electron microscopy.

CONCLUSION

The polyglycolic acid-collagen tube induced functional recovery of the injured phrenic nerve and was aided by coverage with a pedicled pericardial fat pad.

Intraoperative diaphragmatic plication during coronary artery bypass

Diaphragmatic paralysis following coronary artery bypass grafting (CABG), while often benign, can sometimes require plication. This paper describes the first reported case of intraoperative (CABG) pulmonary plication for a patient with prior diaphragmatic paralysis.

Tracheostomy in infants and children after cardiothoracic surgery: indications, associated risk factors, and timing

BACKGROUND

Respiratory insufficiency in children after cardiothoracic surgery delays weaning from the ventilator and prolongs intensive care unit stay. There is little consensus as to the indications for tracheostomy and its safety in this population.

METHODS

We reviewed our institutional experience in 37 consecutive infants and children (median age, 8.6 months; weight, 7.2 kg) requiring a tracheostomy after cardiothoracic surgery between January 1998 and December 2001, with follow-up to June 2003.

RESULTS

Twenty-four children underwent tracheostomy after corrective (n = 15) or palliative (n = 9) surgery for congenital heart disease, 8 had undergone thoracic transplantation, and 5 had undergone thoracic surgery. Median duration of pretracheostomy ventilation was 30 days, and median total duration of ventilation was 73 days. Tracheostomy was performed earlier in patients undergoing transplantation (median of 20 days postoperatively), with a duration of ventilation of 34 days. No patient experienced mediastinitis, and a wound infection in 1 child was the only identified complication. Twenty-two children survived to hospital discharge, of whom 15 have since been decannulated; 6 still have a tracheostomy in situ and 1 has been lost to follow-up. A number of preoperative and postoperative factors were identified in this cohort. These were preoperative respiratory insufficiency, a history of neonatal ventilation, the need for cardiac reoperations, diaphragmatic paralysis, tracheobronchomalacia, neurological comorbidity, and associated chromosomal abnormalities.

CONCLUSION

Tracheostomy can be performed safely and without increased risk of complications in infants and children early after cardiothoracic surgery. The presence of identifiable factors in patients in whom weaning has been unsuccessful should alert clinicians to early consideration of tracheostomy.

Mechanisms of Phrenic Nerve Injury During Radiofrequency Ablation at the Pulmonary Vein Orifice

BACKGROUND

The phrenic nerve can be injured with radiofrequency energy delivery. Nevertheless, the mechanisms of injury are unknown. This study was undertaken to examine phrenic nerve tissue temperatures during ablation at the pulmonary vein (PV) orifice, assess the temperature dependence of injury, and to delineate the possible mechanisms of untoward nerve effects.

METHODS

Ten dogs underwent ablation at the right superior PV (RSPV) orifice. Phrenic nerve temperatures were assessed with implanted thermocouples overlying the endocardial ablation site. Using an 8-mm ablation catheter tip, energy was titrated to 50 degrees C and incremented by 5 degrees C for 120 seconds.

RESULTS

Phrenic nerve capture was achieved in nine (90%) dogs after thermocouple implantation. A RSPV orifice tissue temperature >60 degrees C occurred in 32 (84%) of energy deliveries with a power of 34 +/- 22 W. In three (33%) dogs, this resulted in nerve dysfunction (maximum nerve temperature: 41 degrees C, 41 degrees C, and 91 degrees C) with histology consistent with acute thermal injury. In four additional dogs, 17 energy deliveries were made directly to the phrenic nerve using a novel in situ model. In 5 (29%) energy deliveries, nerve function was impacted immediately by the generated current, with resolution simultaneous with discontinuing radiofrequency. Transient phrenic nerve injury occurred in all dogs at a temperature of 47 +/- 3 degrees C (range: 43-53 degrees C) after 38 +/- 32 seconds (range: 20-120 seconds). After termination of the energy delivery, nerve function returned in 15(88%) during 30 seconds of postablation pacing. In two (12%) ablation attempts, nerve recovery was delayed (>3 minutes). Permanent injury occurred in all dogs after 92 +/- 83 seconds (range: 20-280 seconds) of additional energy delivery at a temperature of 51 +/- 6 degrees C (range: 45-65 degrees C).

CONCLUSION

Phrenic nerve injury can be more common than anticipated with RF ablation at the RSPV orifice. Relatively low tissue temperatures can injure the nerve. Immediate nerve effects suggest a second mechanism of nerve dysfunction related to electrical current. Transient nerve effects occur prior to permanent damage, providing an opportunity to discontinue energy delivery before permanent injury.

Respiratory inductance plethysmography used to diagnose bilateral diaphragmatic paralysis: a case report

OBJECTIVE

To report the use of respiratory inductance plethysmography in the diagnosis and management for a case of bilateral diaphragmatic paralysis after repeated sternotomies in a 23-month-old child.

DESIGN

Case report.

SETTING

A 15-bed pediatric cardiothoracic intensive care unit in an academic children's hospital.

INTERVENTIONS

The patient could not be weaned from the ventilator after a repeat sternotomy for pulmonary artery reconstruction. Pulmonary function test results were within normal limits, and plain film radiography, ultrasonography, and fluoroscopy were unable to establish a definitive diagnosis. Evaluation of thoracoabdominal synchrony was undertaken using respiratory inductance plethysmography (RespiTrace). The work of breathing was assessed using esophageal manometry to obtain the pressure-rate product.

RESULTS

During spontaneous breathing, complete thoracoabdominal asynchrony was noted, with clockwise Konno-Mead loops and associated phase angles of nearly 180 degrees. The pressure-rate product was 120 cm H(2)O/min, indicating elevated work of breathing. The pressure-rate product decreased dramatically, as indicated by measurement and observation, in response to increased levels of continuous positive airway pressure.

CONCLUSIONS

The diagnosis of bilateral diaphragmatic paralysis can be confirmed by measurement of thoracoabdominal synchrony. Therapeutic and diagnostic application of continuous positive airway pressure may predict response to diaphragmatic plication. Controlled trials comparing measurement of thoracoabdominal synchrony with standard methods for the early diagnosis of diaphragmatic paralysis are needed.

[Surgery for diaphragmatic palsy]

Diaphragmatic palsy leads to a permanent ascension of one or both hemi-diaphragms with highly variable functional impact. The underlying mechanisms can be divided into two main categories: neurological or muscular disorder leading to peripheral dysfunction; defective or non-transmitted central command causing central dysfunction. A complete morphological and functional work-up is required to determine the circumstances leading to diaphragmatic palsy and the uni- or bilateral nature of the paralysis. The entire phreno-diaphragmatic transmission chain from the cranium to the diaphragmatic muscle must be analyzed to search for a local cause. Function tests are used to examine central command and transmission, function of the phrenic nerve, and the capacity of the diaphragmatic muscle to generate sufficient pressure for efficacious ventilation. Once indirect causes of diaphragmatic ascension (independent of the phreno-diaphragmatic system) have been ruled out, surgery may be proposed for symptomatic, permanent and irreversible diaphragmatic paralysis. A tension procedure may be sufficient in the event of eventration with or without phrenic palsy. For well-selected patients with central paralysis due to supraspinal lesions with intact nerves and muscles, implantation of a phrenic pacemaker may be helpful to eliminate positive pressure mechanical ventilation and restore more physiological respiration.

Electrophysiological evaluation of phrenic nerve injury during cardiac surgery--a prospective, controlled, clinical study

Background

According to some reports, left hemidiaphragmatic paralysis due to phrenic nerve injury may occur following cardiac surgery. The purpose of this study was to document the effects on phrenic nerve injury of whole body hypothermia, use of ice-slush around the heart and mammary artery harvesting.

Methods

Electrophysiology of phrenic nerves was studied bilaterally in 78 subjects before and three weeks after cardiac or peripheral vascular surgery. In 49 patients, coronary artery bypass grafting (CABG) and heart valve replacement with moderate hypothermic (mean 28°C) cardiopulmonary bypass (CPB) were performed. In the other 29, CABG with beating heart was performed, or, in several cases, peripheral vascular surgery with normothermia.

Results

In all patients, measurements of bilateral phrenic nerve function were within normal limits before surgery. Three weeks after surgery, left phrenic nerve function was absent in five patients in the CPB and hypothermia group (3 in CABG and 2 in valve replacement). No phrenic nerve dysfunction was observed after surgery in the CABG with beating heart (no CPB) or the peripheral vascular groups. Except in the five patients with left phrenic nerve paralysis, mean phrenic nerve conduction latency time (ms) and amplitude (mV) did not differ statistically before and after surgery in either group (p > 0.05).

Conclusions

Our results indicate that CPB with hypothermia and local ice-slush application around the heart play a role in phrenic nerve injury following cardiac surgery. Furthermore, phrenic nerve injury during cardiac surgery occurred in 10.2 % of our patients (CABG with CPB plus valve surgery).

The pulmonary physician in critical care * illustrative case 4: neuromusculoskeletal disorders

The case history is presented of a patient admitted to the ICU with ventilatory insufficiency following thoracotomy for thymic resection. The role of non-invasive ventilation for weaning in patients following phrenic nerve injury is discussed.

Bilateral diaphragm paralysis following lung transplantation and cardiac surgery in a 17-year-old

Bilateral diaphragm paralysis is a rare complication of lung transplantation. This report describes the development of chronic respiratory failure due to bilateral diaphragm paralysis following bilateral lung transplantation and closure of a patent foramen ovale. This patient required prolonged mechanical ventilation post-operatively; however, he eventually had adequate recovery of diaphragm function to wean from mechanical ventilation.