Phrenic nerve dysfunction after cardiac operations: electrophysiologic evaluation of risk factors

Diaphragmatic Nerve Paralysis After Redo Aortic Valve Replacement That Improved Over Time and Led to Successful Ventilator Weaning: A Case Report

We report a 75-year-old female with a history of two heart operations: aortic valve replacement (St. Jude MedicalTM 21 mm) at the age of 44 years for severe rheumatic aortic stenosis and mitral valve replacement (CarbomedicsTM 29 mm) at the age of 51 years for rheumatic mitral regurgitation. Decades later, she presented with exertional dyspnea. Echocardiography revealed aortic stenosis with an effective orifice area of 0.79 cm². Coronary angiography showed #6 75% stenosis and a limited mechanical valve opening. After a thorough discussion, the patient agreed to undergo redo surgery. The surgery involved re-median sternotomy, left internal thoracic artery (LITA) harvesting, pannus removal, and replacement of the aortic valve with a 20 mm ATS advanced performance (AP) prosthesis (ATS Medical, Minneapolis, MN) in a supra-annular position. The LITA-left anterior descending (LAD) bypass was completed, and the patient was weaned from the cardiopulmonary bypass without complications. Postoperatively, the right phrenic nerve paralysis caused transient respiratory challenges requiring tracheotomy and prolonged ventilation. Rehabilitation improved diaphragmatic function and respiratory independence. At six months, the right phrenic nerve function had recovered, and the patient resumed walking independently with a cane. Two years postoperatively, the patient remained ambulatory and attended independent outpatient follow-ups. This report highlights the potential for gradual recovery from phrenic nerve paralysis following open heart surgery, emphasizing the importance of long-term multidisciplinary care.

Early diaphragm dysfunction assessed by ultrasonography after cardiac surgery: a retrospective cohort study

Objective

Approximately 10%-70% of patients may develop diaphragmatic dysfunction after cardiac surgery, which may lead to delayed weaning from mechanical ventilation, increased ICU stays, postoperative hospitalization stays, and respiratory complications. However, its impact on prognosis and risk factors remain controversy. Therefore, we conducted a retrospective cohort study in which we evaluated diaphragmatic dysfunction in patients who underwent cardiac surgery via bedside diaphragm ultrasound to investigate its prognosis and possible risk factors.

Methods

Data from the electronic medical records system included case records and ultrasound images of the diaphragm for 177 consecutive patients admitted to the ICU following cardiac thoracotomy surgeries performed between June and September 2020. Diaphragmatic dysfunction was defined as a diaphragmatic excursion of less than 9 mm in women and less than 10 mm in men at rest, with an average thickening fraction of less than 20%. SPSS 25.0 software was used to analyse the relationships between patients' general information, intraoperative and postoperative factors and diaphragmatic dysfunction, as well as the impact on patients' hospitalization days, mechanical ventilation time and respiratory system complications.

Results

The incidence of early postoperative diaphragmatic dysfunction after cardiac surgery was 40.7%. Patients with diaphragmatic insufficiency were more likely to sequentially use noninvasive ventilation within 24 h after weaning off mechanical ventilation (3.8% vs. 12.5%, P = 0.029) and to require more oxygen support (23.8% vs. 40.3%, P = 0.019). Although there was no significant difference, the diaphragmatic dysfunction group tended to have longer ICU stays and postoperative hospital stays than did the normal diaphragmatic function group (P = 0.119, P = 0.073). Univariate and multivariate logistic regression analyses both revealed that chest tube drainage placed during surgery accompanied by bloody drainage fluid was an independent risk factor for diaphragmatic dysfunction (univariate analysis: 95% CI: 1.126-4.137, P = 0.021; multivariate analysis: 95% CI: 1.036-3.897, P = 0.039).

Conclusion

Eearly diaphragmatic dysfunction after cardiac surgery increased the proportion of patients who underwent sequential noninvasive ventilation after weaning from mechanical ventilation and who required more oxygen. Chest tube drainage placed during surgery accompanied by bloody drainage fluid was an independent risk factor for diaphragmatic dysfunction, providing evidence-based guidance for respiratory rehabilitation after cardiac surgery.

Management of Diaphragm Paralysis and Eventration

An elevated diaphragm may be due to eventration or paralysis. Diaphragm elevation is often asymptomatic and found incidentally on imaging. Fluoroscopic testing can be used to differentiate eventration (no paradoxic motion) from paralysis (paradoxic motion). Regardless of etiology, a diaphragm plication is indicated in all symptomatic patients with an elevated diaphragm. Plication can be approached either from a thoracic or abdominal approach, though most thoracic surgeons perform minimally invasive thoracoscopic plication. The goal of plication is to improve lung volumes and decrease paradoxic elevation of the hemidiaphragm. Diaphragm plication is safe, has excellent outcomes, and is associated with symptom improvement.

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.

Imaging of the Diaphragm Following Cardiac Surgery: Focus on Ultrasonographic Assessment

Diaphragm dysfunction is a common complication following cardiac surgery. Its clinical impact is variable, ranging from the absence of symptoms to the acute respiratory failure. Post-operative diaphragm dysfunction may negatively affect patients' prognosis delaying the weaning from the mechanical ventilation (MV), extending the time of hospitalization and increasing mortality. Ultrasonography is a valid tool to evaluate diaphragmatic impairment in different settings, like the Intensive Care Unit, to predict successful weaning from the MV, and the Cardiovascular Rehabilitation Unit, to stratify patients in terms of risk of functional recovery failure. The aim of this review is to describe the pathophysiology of post-cardiac surgery diaphragm dysfunction, the techniques used for its diagnosis and the potential applications of diaphragm ultrasound.

Ultrasonographic Assessment of Diaphragmatic Function and Its Clinical Application in the Management of Patients with Acute Respiratory Failure

Acute respiratory failure (ARF) is a common life-threatening medical condition, with multiple underlying etiologies. In these cases, many factors related to systemic inflammation, prolonged use of steroids, and lung mechanical abnormalities (such as hyperinflation or increased elastic recoil due to pulmonary oedema or fibrosis) may act as synergic mechanisms leading to diaphragm dysfunction. The assessment of diaphragm function with ultrasound has been increasingly investigated in the emergency department and during hospital stay as a valuable tool for providing additional anatomical and functional information in many acute respiratory diseases. The diaphragmatic ultrasound is a noninvasive and repeatable bedside tool, has no contraindications, and allows the physician to rapidly assess the presence of diaphragmatic dysfunction; this evaluation may help in estimating the need for mechanical ventilation (and the risk of weaning failure), as well as the risk of longer hospital stay and higher mortality rate. This study presents an overview of the recent evidence regarding the evaluation of diaphragmatic function with bedside ultrasound and its clinical applications, including a discussion of real-life clinical cases.

Diaphragm Dysfunction after Cardiac Surgery: Insights from Ultrasound Imaging during Cardiac Rehabilitation

Diaphragm dysfunction is common after cardiac surgery and can be evaluated with ultrasonography (US). We aimed at assessing with US the incidence of diaphragmatic dysfunction and the impact of cardiovascular rehabilitation (CR) on its recovery. A single-center cohort study was performed. Patients were enrolled after cardiac surgery. The 6-min walking test (6MWT) and diaphragm US were performed at CR admission and after 10 rehabilitative sessions. One hundred eighty-five patients were eligible for final analysis. One hundred thirty-one patients (70.8%) were found to have diaphragm dysfunction (excursion <2 cm). After CR, 68 patients regained normal diaphragmatic function; those with persistent dysfunction had a lower level of functional performance on the 6MWT (metabolic equivalents of tasks: 3.3 vs. 3.6, p = 0.013). The patients who underwent combined surgery (adjusted odds ratio [aOR] = 4.09, p = 0.001) and those with post-operative pneumothorax (aOR = 3.02, p = 0.042) were at increased risk of failure to improve diaphragmatic excursion. US parameters were more powerful tools in predicting diaphragmatic evolution compared with the 6MWT indexes: baseline diaphragm excursion and thickening fraction were associated with complete diaphragmatic functional recovery after CR (aOR = 9.101, p < 0.001, and aOR = 1.058, p = 0.020 respectively). US is a valuable tool for the assessment of post-operative diaphragmatic dysfunction and can identify patients at risk of diaphragmatic recovery failure.

Diaphragm Ultrasound in Cardiac Surgery: State of the Art

In cardiac surgery, patients are at risk of phrenic nerve injury, which leads to diaphragm dysfunction and acute respiratory failure. Diaphragm dysfunction (DD) is relatively frequent in cardiac surgery and particularly affects patients after coronary artery bypass graft. The onset of DD affects patients’ prognosis in term of weaning from mechanical ventilation and hospital length of stay. The authors present a narrative review about diaphragm physiology, techniques used to assess diaphragm function, and the clinical application of diaphragm ultrasound in patients undergoing cardiac surgery.

A New Methodology for Intraoperative Monitoring of the Functional Integrity of the Phrenic Nerve During Cardiothoracic Surgery

INTRODUCTION

The phrenic nerve could be easily injured during cardiothoracic surgeries because of its anatomical relationships. The aim of this study is to describe a new, feasible, and reproducible methodology to achieve a continuous intraoperative neuromonitoring of the phrenic nerve.

METHODS

Consecutive patients who underwent open-chest surgery were included. The recording active electrode was placed 5 cm superior to the tip of the xiphoid process, and a hook wire inserted at the motor point of the ipsilateral hemidiaphragm was used as the reference electrode.

RESULTS

We studied 45 patients (92% men, mean age 67 years). Mean height and weight were 167 ± 6.9 cm and 75.6 ± 12.3 kg, respectively. A reproducible compound motor action potential was recorded in 38 (85%) subjects. The mean latency and amplitude values were 9.68 ± 2.40 ms and 1.36 ± 3.83 mV, respectively. No intraoperative events were recorded.

CONCLUSIONS

We reported a new methodology which allows the assessment of phrenic nerve functional integrity during surgical procedures.

A Novel Normalized Cross-Correlation Speckle-Tracking Ultrasound Algorithm for the Evaluation of Diaphragm Deformation

Objectives: To develop a two-dimensional normalized cross-correlation (NCC)-based ultrasonic speckle-tracking algorithm for right diaphragm deformation analysis.

Methods: Six healthy and eight mechanical ventilation patients were enrolled in this study. Images were acquired by a portable ultrasound system in three sections. DICOM data were processed with NCC to obtain the interframe/cumulative vertical and horizontal displacements, as well as the global strain of the right diaphragm, with continuous tracking and drift correction.

Results: The NCC algorithm can track the contraction and relaxation of the right diaphragm by following the respiratory movement continuously. For all three sections, the interframe and accumulated horizontal displacements were both significantly larger than the corresponding vertical displacements (interframe p values: 0.031, 0.004, and 0.000; cumulative p values: 0.039, 0.001, and <0.0001). For the global strain of the right diaphragm, there was no significant difference between each pair of sections (all p > 0.05), regardless of whether the horizontal interval of the initial diaphragm point was 1, 3, 5, or 10 times in the sampling interval.

Conclusions: This study developed a novel diaphragm deformation ultrasound imaging method. This method can be used to estimate the diaphragm interframe/accumulated displacement in the horizontal and vertical directions and the global strain on three different imaging planes, and it was found that the strain was not sensitive to the imaging plane.

Diaphragm Dysfunction After Cardiac Surgery: Reappraisal

OBJECTIVES

The aim of this study was to re-investigate the incidence, risk factors, and outcomes of postoperative diaphragmatic dysfunction (DD) with actual cardiac surgery procedures.

DESIGN

Single-center, retrospective, observational study based on a prospectively collected database.

SETTING

Tertiary care cardiac surgery center.

PARTICIPANTS

Patients who underwent cardiac surgery between January 2016 and September 2019.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

The DD group included patients with clinically perceptible diaphragmatic paralysis, which was confirmed by chest ultrasound (amplitude of the diaphragm movement in time-motion mode at rest, after a sniff test). The primary endpoint was the incidence of DD. Among 3,577 patients included, the authors found 272 cases of DD (7.6%). Individuals with DD had more arterial hypertension (64.3% v 52.6%; p < 0.0001), higher body mass index (BMI) (28 [25-30] kg/m²v 26 [24-29] kg/m²; p < 0.0002), and higher incidence of coronary bypass grafting (CABG) (58.8% v 46.6%; p = 0.0001). DD was associated with more postoperative pneumonia (23.9% v 8.7%; p < 0.0001), reintubation (8.8% v 2.9%; p < 0.0001), tracheotomy (3.3% v 0.3%; p < 0.0001), noninvasive ventilation (45.6% v 5.4%; p < 0.0001), duration of mechanical ventilation (five [four-11] hours v four [three-six] hours; p < 0.0001), and intensive care unit and hospital stays (14 [11-17] days v 13 [11-16] days; p < 0.0001). In multivariate analysis, DD was associated with CABG (odds ratio [OR] 1.9 [1.5-2.6]; p = 0.0001), arterial hypertension (OR 1.4 [1.1-1.9]; p = 0.008), and BMI (OR per point 1.04 [1.01-1.07] kg/m²; p = 0.003).

CONCLUSIONS

The incidence of symptomatic DD after cardiac surgery was 7.6%, leading to respiratory complications and increased ICU stay. CABG was the principal factor associated with DD.

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.

Significant diaphragm elevation suggestive of phrenic nerve injury after thoracoscopic lobectomy for lung cancer: an underestimated problem

Background

Phrenic nerve injury (PNI) during lung cancer surgery, without apparent nerve section or damage, is still not well-studied. The aim of our study is to find an easy and objective way to evaluate a significant diaphragm elevation (SDE) suggestive of inadvertent PNI and its incidence and impact on lung cancer patients undergone video-assisted thoracoscopic surgery (VATS) lobectomy.

Methods

Extent of diaphragm elevation was first examined on chest X-ray in a cohort of patients with invasive thymoma in whom phrenic nerve was intentionally transected. The result was then used as the criterion to diagnose a SDE suggestive of PNI in another cohort of VATS lobectomy patients. Fluoroscopy test was used to validate the results. Spirometry test was repeated to evaluate pulmonary function loss after surgery.

Results

Diaphragm elevation was 24.24%±6.2% in 22 invasive thymoma-patients, with 30% elevation adopted as the criterion to diagnose SDE suggestive of PNI. In 753 VATS lobectomy patients, 56 (7.4%) were diagnosed of SDE. On Fluoroscopy test, diaphragm movement was significantly less in patients with diaphragm elevation >30% than those without (5.0 vs. 11.0 mm, P=0.003), together with a significantly smaller diaphragm movement ratio on the operation (OP) side than on the contralateral side (17% vs. 42%, P=0.018). Although no difference in postoperative complications was found, reduction in FEV1, FVC, and DLCO was significantly greater in patients with a SDE than those without (P=0.009).

Conclusions

Patients with more than 30% diaphragm elevation after VATS lobectomy is highly likely to have PNI and should undergo fluoroscopic validation. Inadvertent PNI during VATS lobectomy is an underestimated phenomenon and is associated with significantly greater loss of pulmonary function.

Unilateral diaphragmatic paralysis associated with surgical mitral valve repair in dogs

OBJECTIVES

Unilateral diaphragmatic paralysis (UDP) due to phrenic nerve injury is a potential complication of thoracic surgery. This study evaluated the prevalence of UDP associated with surgical mitral valve repair (MVR) and its effect on surgical outcomes in dogs.

ANIMALS, MATERIALS AND METHODS

Two hundred ninety-four dogs that underwent MVR were included in the study. A retrospective review of medical records was performed for dogs surviving surgery. Diagnosis of UDP was based on preoperative and postoperative thoracic dorsoventral radiographs.

RESULTS

A total of 284 dogs survived until the day after surgery. The prevalence of UDP on the day after surgery, on the day of discharge, and after the first postoperative month was 30%, 24%, and 9%, respectively. One case of UDP was observed at 3 months after surgery. Unilateral diaphragmatic paralysis was exhibited by nine of the 21 patients that died in the hospital. The proportion of patients with UDP was higher in dogs that died of respiratory failure than in dogs that died of other causes (p = 0.002). Most dogs whose deaths were suspected to have been related to respiratory failure also had pre-existing respiratory diseases. The occurrence of UDP did not relate to the lengths of stay in the intensive care unit or the hospital.

CONCLUSIONS

Our findings suggest that UDP is a common complication in dogs after MVR and that the prevalence of UDP decreases with time after surgery. Unilateral diaphragmatic paralysis is a risk factor for postoperative death, especially in patients with pre-existing respiratory disease.

Diaphragm thickening in cardiac surgery: a perioperative prospective ultrasound study

Background

Diaphragm paresis is common after cardiac surgery and may delay the weaning from the ventilator. Our objective was to evaluate diaphragm thickening during weaning and secondly the muscle thickness as a marker of myotrauma.

Methods

Patients undergoing elective cardiac surgery were prospectively included. Ultrasonic index of right hemidiaphragm thickening fraction (TF) was measured as a surrogate criterion of work of breathing. A TF < 20% was defined as a low diaphragm thickening. Measurements of TF were performed during three periods to study diaphragm thickening evolution defined by the difference between two consecutive time line point: preoperative (D − 1), during a spontaneous breathing trial (SBT) in the intensive care unit and postoperative (D + 1). We studied three patterns of diaphragm thickness at end expiration evolution from D − 1 to D + 1: > 10% decrease, stability and > 10% increase. Demographical data, length of surgery, type of surgery, ICU length of stay (LOS) and extubation failure were collected.

Results

Of the 100 consecutively included patients, 75 patients had a low diaphragm thickening during SBT. Compared to TF values at D − 1 (36% ± 18), TF was reduced during SBT (17% ± 14) and D + 1 (12% ± 11) (P < 0.0001). Thickness and TF did not change according to the type of surgery or cooling method. TF at SBT was correlated to the length of surgery (both r = − 0.4; P < 0.0001). Diaphragm thickness as continuous variable did not change over time. Twenty-eight patients (42%) had a > 10% decrease thickness, 19 patients (29%) stability and 19 patients (28%) in > 10% increase, and this thickness evolution pattern was associated with: a longer LOS 3 days [2–5] versus 2 days [2–4] and 2 days [2], respectively (ANOVA P = 0.046), and diaphragm thickening evolution (ANOVA P = 0.02). Two patients experience extubation failure.

Conclusion

These findings indicate that diaphragm thickening is frequently decreased after elective cardiac surgery without impact on respiratory outcome, whereas an altered thickness pattern was associated with a longer length of stay in the ICU. Contractile activity influenced thickness evolution.

Trial registry number ClinicalTrial.gov ID NCT02208479

Electronic supplementary material

The online version of this article (10.1186/s13613-019-0521-z) contains supplementary material, which is available to authorized users.

Diaphragmatic Palsy

The diaphragm is the primary muscle of respiration, and its weakness can lead to respiratory failure. Diaphragmatic palsy can be caused by various causes. Injury to the phrenic nerve during thoracic surgeries is the most common cause for diaphragmatic palsy. Depending on the cause, the symptoms of diaphragmatic palsies vary from completely asymptomatic to disabling dyspnea requiring mechanical ventilation. On pulmonary function tests, there will be a decrease in the maximum respiratory muscle power. Spirometry shows reduced lung functions and a significant drop of lung function in supine position is typical of diaphragmatic palsy. Diaphragmatic movements with respiration can be directly visualized by fluoroscopic examination. Currently, this test is being replaced by bedside thoracic ultrasound examination, looking at the diaphragmic excursion with deep breathing or sniffing. This test is found to be equally efficient, and without risks of ionizing radiation of fluoroscope. Treatment of diaphragmatic palsy depends on the cause. Surgical approach of repair of diaphragm or nonsurgical approach of noninvasive ventilation has been tried with good success. Overall prognosis of diaphragmatic palsy is good, except when it is related to neuromuscular degeneration conditions.

In-situ left-sided bilateral internal thoracic artery: elevated hemidiaphragm

Background Procurement of the internal thoracic artery risks ipsilateral phrenic nerve injury and elevated hemidiaphragm. Anatomical variations increase the risk on the right side. Patients receiving left-sided in-situ right internal thoracic artery configurations appear to be at greatest risk. Methods From 2014 to 2016, 432 patients undergoing left-sided in-situ bilateral internal thoracic artery grafting were grouped according to right internal thoracic artery configuration: retroaortic via transverse sinus (77%) or ante-aortic (23%); targets were the circumflex and left anterior descending artery territories, respectively. Elevated hemidiaphragm was assessed by serial chest radiographs and categorized by side, complete (≥2 intercostal spaces) versus partial, and permanent versus transient. Results Right elevated hemidiaphragm occurred in 4.2% of patients. The incidence of radiological complete right elevated hemidiaphragm was 2.8% (12/432); 8 cases were transient with recovery in 3.5 ± 0.3 weeks. Permanent right elevated hemidiaphragm occurred in 0.9% (retroaortic group only). Permanent left elevated hemidiaphragm occurred in 0.9% and was significantly higher in the ante-aortic group (3/99 vs. 1/333, p = 0.039). No bilateral hemidiaphragm elevation was documented. Partial right elevated hemidiaphragm occurred in 1.4% and was not associated with adverse early or late respiratory outcomes. Conclusions Despite susceptible right phrenic nerve-internal thoracic artery anatomy, the incidence of permanent right elevated hemidiaphragm is low and no higher than left-sided in prone bilateral internal thoracic artery subsets. This reflects skeletonized internal thoracic artery procurement. Although statistical significance was not achieved, a retroaortic right internal thoracic artery configuration may constitute a higher risk of right phrenic nerve injury.

Preliminary findings on the expression of plasma CD63, CD62P, and PAI 1 in patients with acute cerebral infarction

To investigate the expression and clinical significance of lysosomal granule glycoprotein 63 (CD63), P-selectin (CD62P) and endothelial cell plasminogen activator inhibitor (PAI-1) in patients with acute cerebral infarction. A total of 106 patients with acute cerebral infarction (ACI) admitted to our hospital from January to July in 2017 were selected as the patient group; 80 healthy subjects for physical examination in our hospital were selected as the control group. The expression levels of serum CD63, CD62P, and PAI-1 of the subjects were detected. The levels of CD63, CD62P, and PAI-1 in the serum of the patient group were significantly higher than those in the control group. There was a positive correlation between serum CD63 and CD62P (r = 0.672, P < 0.05) in the patient group. There was a positive correlation between serum CD63 and PAI-1 (r = 0.643, P < 0.05) in the patient group. There was also a positive correlation between serum CD62P and PAI-1 (r = 0.601, P < 0.05) in the patient group. Moreover, in other subtypes of cerebral infarction, the expression of CD63, CD62P, and PAI-1 was significantly higher than that of lacunar infarction. CD63, CD62P, and PAI-1 are highly expressed in peripheral blood mononuclear cells (PBMC) and serum of patients with ACI, which may be closely related to the occurrence and development of patients with ACI. These indices may be used as indicators of clinical diagnosis and prognosis in patients with ACI.

Topical Ice Slush Adversely Affects Sniff Nasal Inspiratory Force After Coronary Bypass Surgery

BACKGROUND

Topical cooling with ice slush as an adjunct for myocardial protection during cardiac surgery has been shown to cause freezing injury of the phrenic nerves. This can cause diaphragmatic dysfunction and respiratory complications.

METHODS

Twenty (n=20) male patients between the ages of 40 and 60 years were equally randomised to undergo elective coronary artery bypass grafting (CABG) with either cold cardioplegic arrest with topical ice slush cooling or cold cardioplegic arrest without the use of ice slush. The sniff nasal inspiratory force (SNIF) was used to compare inspiratory muscle strength.

RESULTS

There was no difference in the preoperative SNIF in the two randomised groups. In the immediate postoperative period, the ice slush group had worse SNIF (33.5±9.6cm H2O versus 47.8±12.2cm H2O; p=0.009). The pre-home discharge SNIF was still significantly lower for the ice slush group despite a noted improvement in SNIF recovery in both groups (38.3±10.6cm H2O versus 53.5±13.2cm H2O; p=0.011). Two patients in the ice slush group had left diaphragmatic dysfunction with none in the control group.

CONCLUSION

The use of topical ice slush is associated with freezing injury of the phrenic nerves. This will adversely affect the inspiratory muscle force which may lead to respiratory complications after surgery.

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.

Neurologic complications of cardiac and vascular surgery

This chapter will provide an overview of the major neurologic complications of common cardiac and vascular surgeries, such as coronary artery bypass grafting and carotid endarterectomy. Neurologic complications after cardiac and vascular surgeries can cause significant morbidity and mortality, which can negate the beneficial effects of the intervention. Some of the complications to be discussed include ischemic and hemorrhagic stroke, seizures, delirium, cognitive dysfunction, cerebral hyperperfusion syndrome, cranial nerve injuries, and peripheral neuropathies. The severity of these complications can range from mild to lethal. The etiology of complications can include a variety of mechanisms, which can differ based on the type of cardiac or vascular surgery that is performed. Our knowledge about neuropathology, prevention, and management of surgical complications is growing and will be discussed in this chapter. It is imperative for clinicians to be familiar with these complications in order to narrow the differential diagnosis, start early management, anticipate the natural history, and improve outcomes.

Diaphragm Dysfunction: Diagnostic Approaches and Management Strategies

The diaphragm is the main inspiratory muscle, and its dysfunction can lead to significant adverse clinical consequences. The aim of this review is to provide clinicians with an overview of the main causes of uni- and bi-lateral diaphragm dysfunction, explore the clinical and physiological consequences of the disease on lung function, exercise physiology and sleep and review the available diagnostic tools used in the evaluation of diaphragm function. A particular emphasis is placed on the clinical significance of diaphragm weakness in the intensive care unit setting and the use of ultrasound to evaluate diaphragmatic action.

“Other” Neurologic Complications After Cardiac Surgery

Compared to the neurologic morbidity of stroke and cognitive dysfunction, “other” neurologic complications involving injuries to the brachial plexus, phrenic nerve, cranial nerves, other peripheral nerves, as well as the visual pathways, have been disproportionately underrepresented in the cardiac surgery and anesthesiology literature. These injuries are often missed in the early postoperative period when attention is focused principally on recovery from the acute trespass of cardiac surgery and cardiopulmonary bypass. However, when these problems do become apparent, they can cause considerable discomfort and morbidity. An overview of the current concepts of injury mechanisms/etiology, diagnosis, prognosis, and when possible, prevention of these injuries is presented.

Pulmonary Complications After Cardiac Surgery

Over the past two decades there has been a steady evolution in the practice of adult cardiac surgery with the introduction of “off-pump” surgery. However, respiratory complications remain a leading cause of postcardiac surgical morbidity and can prolong hospital stays and increase costs. The high incidence of pulmonary complications is in part due to the disruption of normal ventilatory function that is inherent to surgery in the thoracic region. Furthermore, patients undergoing such surgery often have underlying illnesses such as intrinsic lung disease (e.g., chronic obstructive pulmonary disease) and pulmonary dysfunction secondary to cardiac disease (e.g., congestive heart failure) that increase their susceptibility to postoperative respiratory problems. Given that many patients undergoing cardiac surgery are thus susceptiple to pulmonary complications, it is remarkable that more patients do not suffer from them during and after cardiac surgery. This is to a large degree because of advances in anesthetic, surgical and critical care that, for example, have reduced the physiological insults of surgery (e.g., better myocardial preservation techniques) and streamlined care in the immediate postoperative period (e.g., early extubation). Moreover, the development of minimally invasive surgery and nonbypass techniques are further evidence of the attempts at reducing the homeostatic disruptions of cardiac surgery. This review examines the available information on the incidences, consequences, and treatments of postcardiac surgery respiratory complications.

Feasibility of preoperative inspiratory muscle training in patients undergoing coronary artery bypass surgery with a high risk of postoperative pulmonary complications: a randomized controlled pilot study

Objective: To determine in a pilot study the feasibility and effects of preoperative inspiratory muscle training in patients at high risk of postoperative pulmonary complications who were scheduled for coronary artery bypass graft surgery.

Design: Single-blind, randomized controlled pilot study.

Setting: University Medical Centre Utrecht, the Netherlands.

Subjects: Twenty-six patients at high risk of postoperative pulmonary complications were selected.

Intervention: The intervention group ( N = 14) received 2-4 weeks of preoperative inspiratory muscle training on top of the usual care received by the patients in the control group.

Main measures: Primary outcome variables of feasibility were the occurrence of adverse events, and patient satisfaction and motivation. Secondary outcome variables were postoperative pulmonary complications and length of hospital stay.

Results: The feasibility of inspiratory muscle training was good and no adverse events were observed. Treatment satisfaction and motivation, scored on 10-point scales, were 7.9 (± 0.7) and 8.2 (± 1.0), respectively. Postoperative atelectasis occurred in significantly fewer patients in the intervention group than in the control group (ϰ2DF1 = 3.85; P = 0.05): Length of hospital stay was 7.93 (± 1.94) days in the intervention group and 9.92 (± 5.78) days in the control group ( P = 0.24).

Conclusion: Inspiratory muscle training for 2-4 weeks before coronary artery bypass graft surgery was well tolerated by patients at risk of postoperative pulmonary complications and prevented the occurrence of atelectasis in these patients. A larger randomized clinical trial is warranted.

Evaluation of lung volumes, vital capacity and respiratory muscle strength after cervical, thoracic and lumbar spinal surgery

CONTEXT AND OBJECTIVE

Studies have shown that physiopathological changes to the respiratory system can occur following thoracic and abdominal surgery. Laminectomy is considered to be a peripheral surgical procedure, but it is possible that thoracic spinal surgery exerts a greater influence on lung function. The aim of this study was to evaluate the pulmonary volumes and maximum respiratory pressures of patients undergoing cervical, thoracic or lumbar spinal surgery.

DESIGN AND SETTING

Prospective study in a tertiary-level university hospital.

METHODS

Sixty-three patients undergoing laminectomy due to diagnoses of tumors or herniated discs were evaluated. Vital capacity, tidal volume, minute ventilation and maximum respiratory pressures were evaluated preoperatively and on the first and second postoperative days. Possible associations between the respiratory variables and the duration of the operation, surgical diagnosis and smoking status were investigated.

RESULTS

Vital capacity and maximum inspiratory pressure presented reductions on the first postoperative day (20.9% and 91.6%, respectively) for thoracic surgery (P = 0.01), and maximum expiratory pressure showed reductions on the first postoperative day in cervical surgery patients (15.3%; P = 0.004). The incidence of pulmonary complications was 3.6%.

CONCLUSIONS

There were reductions in vital capacity and maximum respiratory pressures during the postoperative period in patients undergoing laminectomy. Surgery in the thoracic region was associated with greater reductions in vital capacity and maximum inspiratory pressure, compared with cervical and lumbar surgery. Thus, surgical manipulation of the thoracic region appears to have more influence on pulmonary function and respiratory muscle action.

Diaphragm Appearance: A Clue to the Diagnosis of Pulmonary and Extrapulmonary Pathology

The diaphragm is often overlooked or incompletely evaluated when interpreting chest radiographs. Alterations in the appearance of the diaphragm on chest radiographs such as elevation, contour abnormalities, adjacent lucency, and calcifications can offer clues to pulmonary and extrapulmonary pathology. Familiarity with common causes of these alterations facilitates the appropriate selection of additional imaging and leads to the diagnosis of both benign and life-threatening processes. This article reviews normal variations in the appearance of the diaphragm as well as those associated with pulmonary and extrapulmonary pathology.

Improving ultrasonic measurement of diaphragmatic excursion after cardiac surgery using the anatomical M-mode: a randomized crossover study

PURPOSE

Motion-mode (MM) echography allows precise measurement of diaphragmatic excursion when the ultrasound beam is parallel to the diaphragmatic displacement. However, proper alignment is difficult to obtain in patients after cardiac surgery; thus, measurements might be inaccurate. A new imaging modality named the anatomical motion-mode (AMM) allows free placement of the cursor through the numerical image reconstruction and perfect alignment with the diaphragmatic motion. Our goal was to compare MM and AMM measurements of diaphragmatic excursion in cardiac surgical patients.

METHODS

Cardiac surgical patients were studied after extubation. The excursions of the right and left hemidiaphragms were measured by two operators, an expert and a trainee, using MM and AMM successively, according to a blinded, randomized, crossover sequence. Values were averaged over three consecutive respiratory cycles. The angle between the MM and AMM cursors was quantified for each measurement.

RESULTS

Fifty patients were studied. The mean (±SD) angle between the MM and AMM cursors was 37° ± 16°. The diaphragmatic excursion as measured by experts was 1.8 ± 0.7 cm using MM and 1.5 ± 0.5 cm using AMM (p < 0.001). Overall, the diaphragmatic excursion as estimated by MM was larger than the value obtained with AMM in 75 % of the measurements. Bland-Altman analysis showed tighter limits of agreement between experts and trainees with AMM [bias: 0.0 cm; 95 % confidence interval (CI): 0.8 cm] than with MM (bias: 0.0 cm; 95 % CI: 1.4 cm).

CONCLUSION

MM overestimates diaphragmatic excursion in comparison to AMM in cardiac surgical patients. Using MM may lead to a lack of recognition of diaphragmatic dysfunction.

Exercise therapy for a patient with persistent dyspnea after combined traumatic diaphragmatic rupture and phrenic nerve injury

We present a case report of a patient with a history of diaphragmatic rupture who had persistent dyspnea for 9 months after primary surgical repair of a right diaphragmatic rupture caused by a car accident. A phrenic nerve conduction study was performed, which demonstrated a rare accompanying ipsilateral phrenic nerve injury with resultant hemidiaphragmatic paralysis. Aerobic exercise therapy for the purpose of improving endurance and dietary modification for weight reduction were prescribed and continued for 6 months. The exercise intensity was prescribed based on the percentage of maximum heart rate as confirmed by an exercise tolerance test. The duration of exercise was gradually increased. In this case, the long-persistent dyspnea was successfully alleviated via nonoperative management to the point that the patient could resume regular activities of daily living.

Neurologic complications of cardiac surgery and interventional cardiology

A wide array of neurologic complications can occur in relation to cardiac surgical procedures, most of which are transient and do not result in permanent sequelae. Specific neurologic insults can occur depending on the type of cardiac procedure and are an important cause of morbidity and mortality. Neurologists practicing in the hospital setting as well as outpatient neurologists should be familiar with the cardiac surgical procedures currently available. Prompt identification of neurologic deficits is important in order to plan an appropriate systematic evaluation and initiate possible treatments in a timely manner. This chapter provides a comprehensive overview of all facets of neurologic complications after cardiac surgical procedures.

Preoperative mild cognitive dysfunction predicts pulmonary complications after coronary artery bypass graft surgery

OBJECTIVES

In elderly patients with mild cognitive impairment, noncompliance with respiratory exercises, ineffective expectoration, reluctance in mobilization, and difficulty in learning the use of drugs such as inhalers were observed in the early postoperative period after coronary artery bypass graft surgery. It was hypothesized that respiratory complications may be more frequent in these patients, and so the postoperative respiratory complications in patients with preoperative mild cognitive impairment were compared with the postoperative respiratory complications of a control group.

DESIGN

A prospective cohort control.

SETTING

A university hospital.

PARTICIPANTS

Patients undergoing elective coronary artery bypass graft surgery.

INTERVENTIONS

Investigators separated 48 patients>70 years old who were scheduled for elective coronary artery bypass graft surgery into two groups: patients with preoperative mild cognitive impairment (group A, n = 25) and patients with no cognitive impairment (control group; group B, n = 23). The patients' cognitive status was evaluated preoperatively by the Montreal Cognitive Assessment test.

MEASUREMENTS AND MAIN RESULTS

Pulmonary functions and respiratory complications were evaluated via chest x-rays and spirometry tests preoperatively and postoperatively. A significant difference was observed between the groups, particularly with regard to atelectasis and prolonged ventilation (p<0.001 and p<0.05). No significant impairment was observed in the spirometry tests of the control group. However, a significant deterioration was observed in the postoperative spirometry tests of patients with preoperative mild cognitive impairment.

CONCLUSIONS

This study suggested that mild cognitive impairment was associated with pulmonary complications after coronary artery bypass graft surgery.

Phrenic nerve injury and diaphragmatic paralysis following pacemaker pulse generator replacement

Diaphragmatic paralysis (DP) is a common condition. It can be unilateral or bilateral and the diagnosis is usually based on a clinical and radiological findings. Bilateral diaphragmatic paralysis is usually symptomatic with dyspnea and acute respiratory failure while unilateral diaphragmatic paralysis is typically asymptomatic and when present, symptoms usually depend on the presence of underlying pulmonary or neurologic disease. DP can be the result of various chest conditions that affect the phrenic nerve such as tumors, vascular abnormalities or traumatic incidents during surgery as well as blunt or penetrating chest or neck injuries. We report a unique case of phrenic nerve injury and unilateral diaphragmatic paralysis secondary to pacemaker pulse generator replacement that was successfully treated with diaphragmatic plication.

Diaphragmatic height index: new diagnostic test for phrenic nerve dysfunction

OBJECT

The diaphragmatic height index (DHI) was developed to measure the difference in diaphragm levels. The purpose of this study was to set definite DHI values and test the accuracy of these values for use as a new diagnostic test for phrenic nerve dysfunction.

METHODS

All data for this study were obtained from medical charts and retrospectively reviewed.

RESULTS

One hundred sixty-five patients with brachial plexus injury who had undergone nerve transfers between 2005 and 2008 were divided into Groups A and B. Group A consisted of 40 patients (mean age 28.0 years) who had sustained concomitant injury of the brachial plexus and phrenic nerves. Patients in Group A1 had right phrenic nerve injury and those in Group A2 had left phrenic nerve injury. Intraoperative direct electrical stimulation of the phrenic nerve was considered the gold standard in assessing nerve function in all patients with brachial plexus injury. Group B consisted of 125 patients (mean age 28.7 years) with brachial plexus injury and normal phrenic nerve function. Group C, the control group, consisted of 80 patients with nonbrachial plexus injury (mean age 34.0 years) who had undergone other kinds of orthopedic operations between April and June 2009. Standard posteroanterior chest radiographs were blindly interpreted using the Siriraj inhouse picture archiving and communication system in all 245 patients in the study. First, a reference line (R line) was drawn along the inferior endplate of T-10. Then, 2 lines (lines A and B) were drawn through the highest point of each diaphragm and parallel to the R line. The difference between these 2 lines divided by the height of T-10 was defined as the DHI. The cutoff points of the DHI for diagnosing right and left phrenic nerve dysfunction were analyzed with a receiver operating characteristic curve. The accuracy of these DHI values was then evaluated. The DHI in Group C was 0.64 ± 0.44, slightly higher than the DHI in Group B, with no significant difference. Diaphragmatic height indexes in Groups A1 and A2 were 2.0 ± 0.99 and -1.04 ± 0.83, respectively, which were significantly different from those in Groups B and C (p < 0.05). The cutoff point of the DHI for diagnosing right phrenic nerve dysfunction was > 1.1, and that for left phrenic nerve dysfunction was < 0.2. The sensitivity and specificity of right and left DHI values were 90.5% and 86.3%, and 94.7 and 88.3%, respectively.

CONCLUSIONS

Data in this study show that diaphragm paralysis can be simply and reliably predicted by the DHI. Diaphragmatic height index values > 1.1 and < 0.2 are proposed as the new diagnostic test for right and left phrenic nerve dysfunction with a high degree of accuracy. This index is applicable in diagnosing phrenic nerve dysfunction that occurs concomitantly with brachial plexus injury or from other etiologies.

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.

Impairment of diaphragm muscle force and neuromuscular transmission after normothermic cardiopulmonary bypass: effect of low-dose inhaled CO

Cardiopulmonary bypass (CPB) is associated with significant postoperative morbidity, but its effects on the neuromuscular system are unclear. Recent studies indicate that even relatively short periods of mechanical ventilation result in significant neuromuscular effects. Carbon monoxide (CO) has gained recent attention as therapy to reduce the deleterious effects of CPB. We hypothesized that 1) CPB results in impaired neuromuscular transmission and reduced diaphragm force generation; and 2) CO treatment during CPB will mitigate these effects. In adult male Sprague-Dawley rats, diaphragm muscle-specific force and neuromuscular transmission properties were measured 90 min after weaning from normothermic CPB (1 h). During CPB, either low-dose inhaled CO (250 ppm) or air was administered. The short period of mechanical ventilation used in the present study ( approximately 3 h) did not adversely affect diaphragm muscle contractile properties or neuromuscular transmission. CPB elicited a significant decrease in isometric diaphragm muscle-specific force compared with time-matched, mechanically ventilated rats ( approximately 25% decline in both twitch and tetanic force). Diaphragm muscle fatigability to 40-Hz repetitive stimulation did not change significantly. Neuromuscular transmission failure during repetitive activation was 60 +/- 2% in CPB animals compared with 76 +/- 4% in mechanically ventilated rats (P < 0.05). CO treatment during CPB abrogated the neuromuscular effects of CPB, such that diaphragm isometric twitch force and neuromuscular transmission were no longer significantly different from mechanically ventilated rats. Thus, CPB has important detrimental effects on diaphragm muscle contractility and neuromuscular transmission that are largely mitigated by CO treatment. Further studies are needed to ascertain the underlying mechanisms of CPB-induced neuromuscular dysfunction and to establish the potential role of CO therapy.

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.

The effect of denervation on protein synthesis and degradation in adult rat diaphragm muscle

Previous studies showed that unilateral denervation (DNV) of the rat diaphragm muscle (DIAm) results in loss of myosin heavy chain protein by 1 day after DNV. We hypothesize that DNV decreases net protein balance as a result of activation of the ubiquitin-proteasome pathway. In DIAm strips, protein synthesis was measured by incorporation of 3H-Tyr, and protein degradation was measured by Tyr release at 1, 3, 5, 7, and 14 days after DNV. Total protein ubiquitination, caspase-3 expression/activity, and actin fragmentation were analyzed by Western analysis. We found that, at 3 days after DNV, protein synthesis increased by 77% relative to sham controls. Protein synthesis remained elevated at 5 (85%), 7 (53%), and 14 days (123%) after DNV. At 5 days after DNV, protein degradation increased by 43% relative to sham controls and remained elevated at 7 (49%) and 14 days (74%) after DNV. Thus, by 5 days after DNV, net protein balance decreased by 43% compared with sham controls and was decreased compared with sham at 7 (49%) and 14 days (72%) after DNV. Protein ubiquitination increased at 5 days after DNV and remained elevated. DNV had no effect on caspase-3 activity or actin fragmentation, suggesting that the ubiquitin-proteasome pathway rather than caspase-3 activation is important in the DIAm response to DNV. Early loss of contractile proteins, such as myosin heavy chain, is likely the result of selective protein degradation rather than generalized protein breakdown. Future studies should evaluate this selective effect of DNV.