Elevated hemidiaphragm after cardiac operations: incidence, prognosis, and relationship to the use of topical ice slush

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.

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.

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.

Best Approach and Benefit of Plication for Paralyzed Diaphragm

Diaphragmatic eventration and diaphragmatic paralysis are 2 entities with different etiology and pathology, and are often clinically indistinguishable. When symptomatic, their treatment is the same, with the objective to reduce the dysfunctional cephalad excursion of the diaphragm during inspiration. This can be achieved with diaphragmatic plication through the thorax or the abdomen with either open or minimally invasive techniques. We prefer the laparoscopic approach, due to its easy access to the diaphragm and to avoid pain associated with intercostal incisions and instrument use. Short-term and long-term results are excellent with this technique.

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.

The Effects of Phrenic Nerve Degeneration by Axotomy and Crush on the Electrical Activities of Diaphragm Muscles of Rats

The aim of this study was to investigate the effect of axotomy and crush-related degeneration on the electrical activities of diaphragm muscle strips of experimental rats. In the present study, twenty-one male Wistar-albino rats were used and divided into three groups. The animals in the first group were not crushed or axotomized and served as controls. Phrenic nerves of the rats in the second and third groups were crushed or axotomized in the diaphragm muscle. Resting membrane potential (RMP) was decreased significantly in both crush and axotomy of diaphragm muscle strips of experimental rats (p < 0.05). Depolarization time (T DEP) and half-repolarization (1/2 RT) time were significantly prolonged in crush and axotomy rats (p < 0.05). Crushing or axotomizing the phrenic nerves may produce electrical activities in the diaphragm muscle of the rat by depolarization time and half-repolarization time prolonged in crush and axotomy rats.

Postoperative Critical Care of the Adult Cardiac Surgical Patient. Part I: Routine Postoperative Care

OBJECTIVES

Cardiac surgery, including coronary artery bypass, cardiac valve, and aortic procedures, is among the most common surgical procedures performed in the United States. Successful outcomes after cardiac surgery depend on optimum postoperative critical care. The cardiac intensivist must have a comprehensive understanding of cardiopulmonary physiology and the sequelae of cardiopulmonary bypass. In this concise review, targeted at intensivists and surgeons, we discuss the routine management of the postoperative cardiac surgical patient.

DATA SOURCE AND SYNTHESIS

Narrative review of relevant English-language peer-reviewed medical literature.

CONCLUSIONS

Critical care of the cardiac surgical patient is a complex and dynamic endeavor. Adequate fluid resuscitation, appropriate inotropic support, attention to rewarming, and ventilator management are key components. Patient safety is enhanced by experienced personnel, a structured handover between the operating room and ICU teams, and appropriate transfusion strategies.

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.

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.

Diaphragm plication for eventration or paralysis: a review of the literature

Although etiology and pathology of symptomatic diaphragm paralysis and eventration are distinct, their treatments are the same: to reduce dysfunctional caudal excursion of the diaphragm during inspiration by plication. Minimally invasive diaphragm plication techniques have emerged as equally effective and less morbid alternatives to open plication. This review focuses on the etiology, pathophysiology, diagnosis, and treatment of diaphragmatic eventration or paralysis in adults.

Incidence and management of diaphragmatic palsy in patients after cardiac surgery

Background:

Diaphragm is the most important part of the respiratory system. Diaphragmatic palsy following cardiac surgery is not uncommon and can cause deterioration of pulmonary functions and attendant pulmonary complications.

Objectives:

Aim of this study was to observe the incidence of diaphragmatic palsy after off pump coronary artery bypass grafting (OPCAB) as compared to conventional CABG and to assess the efficacy of chest physiotherapy on diaphragmatic palsy in post cardiac surgical patients.

Design and Setting:

An observational prospective interventional study done at a tertiary care cardiac centre.

Patients:

2280 consecutive adult patients who underwent cardiac surgery from February 2005 to august 2005.

Results:

30 patients out of 2280 (1.31%) developed diaphragmatic palsy. Patients were divided based on the presence or absence of symptoms viz. breathlessness at rest or exertion or with the change of posture along with hypoxemia and / or hypercapnia. Group I included 14 patients who were symptomatic (CABG n=13, post valve surgery n=1), While Group II included 16 asymptomatic patients (CABG n=12, post valve surgery n=4), 9 patients (64%) from Group I (n=14) and 4 patients (25%) from group II showed complete recovery from diaphragmatic palsy as demonstrated ultrasonographically.

Conclusion:

The incidence of diaphragmatic palsy was remarkably less in our adult cardiac surgical patients because most of the cardiac surgeries were performed off pump and intensive chest physiotherapy beginning shortly after extubation helped in complete or near complete recovery of diaphragmatic palsy. Chest Physiotherapy led to marked improvement in functional outcome following post cardiac surgery diaphragmatic palsy.

We also conclude that ultrasonography is a simple valuable bed-side tool for rapid diagnosis of diaphragmatic palsy

Diaphragmatic eventration

Symptomatic diaphragmatic eventration is an uncommon condition and is sometimes impossible to distinguish clinically from paralysis. Patients who are asymptomatic require no treatment; patients who are symptomatic benefit significantly from diaphragm plication. The choice of plication approach is dependent upon the expertise of the surgeon.

Myocardial cooling with ice-slush provides no cardioprotective effects in aortic valve replacement

OBJECTIVES

Topical cooling of the heart with ice-slush has been widely used for myocardial protection. No prospective, randomized study has evaluated the effect of ice-slush on acknowledged markers (CK-MB, troponin-T) of myocardial damage during aortic valve replacement (AVR). This was the first aim of the present study. A second aim was to examine whether performing a study per se reduced myocardial damage.

DESIGN

Sixty patients undergoing AVR were receiving cold crystalloid antegrade cardioplegia every 20 min. Thirty patients were randomized to achieve additional topical cooling with ice-slush. CK-MB and troponin-T were compared between groups as well as to a group of patients undergoing AVR immediately prior to the study.

RESULTS

There were no significant differences in myocardial markers between patients with or without ice-slush. However, we found significantly higher levels of troponin-T and CK-MB in patients undergoing AVR prior to start of the study.

CONCLUSIONS

Topical cooling with ice-slush does not provide additional cardioprotective effects. Comparison with an historical cohort indicates that administration of crystalloid cardioplegia following a rigid protocol might reduce myocardial damage.

Diaphragmatic paralysis following minor cervical trauma

Two asthmatic patients developed unilateral diaphragmatic paralysis from phrenic nerve injury, in one case following cervical chiropractic manipulation and in the other after a motorcycle accident. Both presented with increased dyspnea and orthopnea. Diagnosis, severity, and level of the lesion were established by neurophysiological methods, which are preferred to chest radiography and diaphragmatic ultrasonography. In spite of only partial electrophysiological recovery of the nerve, both patients were asymptomatic 1 year later.

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.

Pseudodyskinesis of the inferior left ventricular wall: recognizing an echocardiographic mimic of myocardial infarction

INTRODUCTION

Dyskinesis is diagnosed by outward systolic bulging, but a similar inferior wall (IW) motion is sometimes observed in patients without infarction. Such diastolic flattening of the IW is followed by systolic rounding and outward bulging, consistent with extrinsic diastolic compression that is overcome by systolic contraction.

HYPOTHESIS

Pseudodyskinesis (PD) (paradoxical IW motion) is associated with preserved systolic wall thickening and does not reflect ischemic dysfunction.

METHODS

We compared 100 consecutive patients having a pattern of PD on transthoracic echocardiography with control groups of 50 patients with documented inferior myocardial infarction and 50 healthy individuals. Percent systolic thickening of the inferior, anterior, septal, and lateral left ventricular (LV) walls was measured in a midventricular short-axis view, and LV cross-sectional shape was evaluated by the ratio of two perpendicular diameters. Diaphragmatic position was evaluated on chest radiograph.

RESULTS

Systolic IW thickening was not significantly different in PD from that of normal (58.2 +/- 6.2% vs 53.0 +/- 4.6%) and of non-IW in the same patients (50.4 +/- 6.8%). The LV was circular (diameter ratio = 1.0) in systole and diastole in healthy individuals; in PD, it was noncircular in diastole consistent with IW compression (P < .01), and circular in systole; in inferior myocardial infarction, it was circular in diastole and noncircular in systole (P < .01) consistent with decreased IW contraction. The left hemidiaphragm was more elevated in PD (78% vs 8.5%, P < .01).

CONCLUSIONS

In PD, the IW thickens normally to produce a circular LV cavity in systole. This motion, consistent with extrinsic compression, is important to distinguish from inferior myocardial infarction.

Electrophysiologic evaluation of phrenic nerve and diaphragm function after coronary bypass surgery: Prospective study of diabetes and other risk factors

OBJECTIVE

Phrenic neuropathy after coronary artery bypass grafting has been related to various risk factors with conflicting results. The aim of this study was to assess the incidence, characteristics, and clinical consequences of phrenic neuropathy and the influence of diabetes and other risk factors.

METHODS

We conducted an observational, prospective study of parallel groups including 94 consecutive patients subjected to coronary artery bypass grafting, half of them with diabetes and associated polyneuropathy. Electrophysiologic study of phrenic nerve conduction as the reference method, chest radiography, diaphragm ultrasound, and functional respiratory tests were performed 24 to 48 hours before and 7 days after surgery. In those patients showing phrenic neuropathy, explorations were repeated, including needle diaphragmatic electromyography, at 1, 3, 6, 9, 12, 18, and 24 months or until recovery.

RESULTS

Fifteen of the 94 patients (16%) had phrenic neuropathy, 9 in the left side, 3 on the right, and 3 bilateral. Nine (60%) of the affected patients had diabetes, but diabetes did not represent a greater risk of neuropathy (relative risk 1.5, 95% confidence interval 0.6-3.9). Multivariate analysis showed no association of phrenic nerve injury with age, sex, ejection fraction, diabetes, use of internal thoracic artery, or number of grafts as risk factors. Phrenic neuropathy did not result in greater morbidity, and most patients recovered in less than 1 year.

CONCLUSIONS

None of the risk factors studied, including diabetes, influenced the appearance of phrenic neuropathy, thus indicating a role for nerve damage during surgery. Low morbidity and relatively rapid recovery were observed.

Iatrogenic-induced dysfunction of the neuromuscular respiratory system

In the presence of respiratory symptoms that are associated with alveolar hypoventilation or a restrictive ventilatory defect and in the absence of parenchymal or pleural abnormalities on the chest radiograph, iatrogenic causes must be evoked, exactly as they are in the presence of interstitial lung disease. In most cases, the anamnestic and clinical contexts provide a strong diagnostic presumption. It is important to establish carefully the mechanism of the observed disorders, using the currently available arsenal of diagnostic tools for clinical and prognostic reasons and from a medicolegal standpoint. It is necessary to evaluate precisely the clinical repercussions of the respiratory neuromuscular abnormality to serve as a basis for follow-up and to discuss therapeutic options in certain cases (eg, nocturnal ventilation to correct nocturnal hypoventilation due to diaphragmatic dysfunction, diaphragm plication to alleviate dyspnea after complete phrenic nerve destruction, phrenic nerve pacing), again in the perspective of medicolegal actions.

Laparoscopic diaphragmatic plication: long-term results of a novel surgical technique for postoperative phrenic nerve palsy

BACKGROUND

Paralysis of the diaphragm is a severe complication of cardiothoracic surgery carrying significant morbidity and mortality. This study demonstrates a novel minimally invasive technique for treatment of phrenic nerve injuries presenting with symptomatic eventration of the diaphragm. It also presents long-term results of three patients treated with this operation.

METHODS

Chest x-ray proved eventration of the left diaphragm in all patients. Two patients required treatment due to prolonged respirator therapy/assisted ventilation for 4 weeks after cardiac surgery. One patient suffered from progressive dyspnea caused by increasing left-sided diaphragmatic elevation and underwent surgery 2 years after cardiac surgery. In all cases, a minimally invasive abdominal approach was chosen. During surgery the dome of the diaphragm was pulled down via three percutaneously inserted retention stitches. This resulted in two or three folds of the diaphragm located within the abdomen. These diaphragmatic folds were subsequently tightened using 12 to 15 unresorbable sutures with extracorporally prepared knots. Surgical as well as long-term follow-up results are presented of all patients and a review of the current literature is provided.

RESULTS

Mean operating time was 203 min; mean intraoperative blood loss was 130 ml. No major complications occurred during surgery or the postoperative period. At a median follow-up of 72 months no recurrence was observed.

CONCLUSIONS

Laparoscopic diaphragmatic plication provides excellent relief of symptoms caused by diaphragmatic paralysis. There is no perioperative morbidity, and hospital stay is short. The laparoscopic approach, therefore, is an attractive surgical alternative for the treatment of phrenic nerve palsy and should be considered in all suitable patients.

Pulmonary function 4 months after coronary artery bypass graft surgery

The objective of this study was to describe the pulmonary function and pain 4 months after coronary artery bypass graft surgery. Twenty-five male patients performed pulmonary function tests before surgery, on the 4th postoperative day and 4 months after surgery. A severe reduction in pulmonary function was present after surgery. Four months postoperatively, the patients still showed a significant decrease (6-13% of preoperative values) in vital capacity (P<0.001), inspiratory capacity (P<0.001), forced expiratory volume in 1 s (P<0.001) peak expiratory flow rate (P<0.001), functional residual capacity (P=0.05) total lung capacity (P<0.001) and single-breath carbon monoxide diffusing capacity (P<0.01). Residual volume and single-breath carbon monoxide diffusing capacity per litre of alveolar volume had returned to the preoperative level. Four months postoperatively, the median values for sternotomy pain while taking a deep breath was 0.2 and while coughing 0.3 on a 10 cm visual analogue pain scale. In conclusion, a significant restrictive pulmonary impairment persisting up to 4 months into the postoperative period was found after CABG. Measured levels of pain were low and could not explain the impairment.

A review of perioperative nerve injury to the upper extremities

Perioperative nerve injuries can be a complication of surgical procedures and accounts for approximately 16% of all anesthesia-related claims in the United States. Whereas ulnar neuropathy at the elbow is the most common, other nerve injuries of the upper extremity and the phrenic nerve are not rare occurrences. A number of possible etiologies have been proposed to explain perioperative nerve injury to include stretch, compression, ischemia, and metabolic derangement. There appears to be additional factors making some patients more prone to nerve injury than others, for example, the sex of the patient and pre-existing disease. Also, in some cases there is a discrepancy between the timing of the surgery and the injury manifestations that can be the result of delayed recognition or an insult in the postoperative setting.

Critical illness neuromuscular abnormalities

CINMAs occur commonly in acutely critically ill inflamed patients, and can prolong respiratory failure, lead to ventilator dependency, and contribute to the development of chronic critical illness. The etiology of NMDs are diverse and overlap, and distinguishing different disease entities by clinical exam and electrophysiologic studies can be difficult. CIP, which has been the most widely studied CINMA, represents the peripheral nervous system manifestation of the MODS. Patients with CIP, particularly those with severely reduced nerve function, have a prolonged rehabilitation and a high mortality rate. Although there are no definitive treatments, diagnosing a CINMA may provide helpful prognostic information. Future preventative measures may include immunoglobulin, nerve growth factors, or strict glycemic control, although in the CCI phase general supportive care is given, including prevention of iatrogenic complications, nutritional support, psychosocial support, and physical therapy. The early recognition of CINMAs and prevention of associated complications are important to enabling CCI patients with CINMAs to recover and return home with an acceptable functional level and quality of life.

Is phrenic nerve dysfunction after cardiac surgery related to internal mammary harvesting?

BACKGROUND

Although many surgeons feel that internal mammary artery (IMA) harvesting is a risk factor for phrenic nerve dysfunction (PND) following coronary artery bypass grafting surgery (CABG), objective data confirming this are lacking. We sought to compare two groups of cardiac surgical patients to determine if an association exists between IMA harvesting and PND following CABG.

METHODS

Using inpatient medical records and chest radiographs, we performed a retrospective analysis of 25 consecutive CABG patients and 25 consecutive valve procedure patients in order to compare the incidence of PND following cardiac surgery with and without IMA harvesting.

RESULTS

Two patients were excluded. Thirty-one patients underwent IMA harvesting as part of their procedure, of whom 42% had PND evidenced on postextubation chest X-ray. Seventeen patients did not have IMA harvesting, and the incidence of PND in this group was 12% (p = 0.05). Both groups were similar in preoperative variables and operative techniques.

CONCLUSION

This study suggests IMA harvesting is indeed a risk factor for PND following CABG.

Pulmonary complications after coronary revascularization

Pulmonary complications are common after coronary artery bypass grafting. Identifying those individuals with increased risk of respiratory complications allows for appropriate preoperative intervention. The most commonly seen pulmonary complications include pleural effusion, hemothorax, atelectasis, pulmonary edema, diaphragmatic dysfunction, and pneumonia. Clinical features and appropriate management of these common problems are discussed.

Internal mammary artery harvesting using the harmonic scalpel

Internal mammary artery (IMA) harvesting using the harmonic scalpel (HS) was recently introduced. We studied 541 IMAs harvested by the same surgeon through a standard median sternotomy in 472 coronary bypass patients; 252 (47%) with the HS, while 289 (53%) were with electrocautery (EC). Patient demographics included mean ages: 67 years HS vs. 65 years EC (p = NS); male:female ratio: 3:1; and insulin dependent diabetes mellitus (IDDM): 11% HS vs. 12.5% EC (NS). Mean ultrasonic IMA flow at a mean SBP of 70 mm Hg in 10 consecutive patients of each group were: preharvest, HS 11.9 +/- 2.3 ml/min vs. EC 8.5 +/- 1.6 ml/min (p = 0.256); postharvest, HS 35.7 +/- 10.7 ml/min vs. EC 22 +/- 2.9 ml/min (0.235); and postcardiopulmonary bypass (post-CPB), HS 47.8 +/- 6.2 ml/min vs. EC 41.7 +/- 2.5 ml/min (0.381). Histologic samples of 50 consecutive IMAs showed no evidence of vessel injury in either group. Clinical results revealed postoperative bleeding in 6/217 (2.7%) HS vs. 7/255 (2.7%) EC (p = 0.783), none attributed to bleeding from the IMA; phrenic paresis: 0/217 in HS but 1/255 (0.4%) in EC (p = 0.960); sternal wound infection: 5/217 (2.3%) HS vs. 6/255 (2.4%) EC (p = 0.787); postoperative IABP: 6/217 (2.7%) HS vs. 5/255 (2%) EC (p = 0.859); mortality: 2/217 (0.9%) HS vs. 2/255 (0.8%) EC (p = 0.710). Hemodynamic, histologic, and clinical results were comparable in both groups. The authors believe the HS is safe and effective for IMA harvesting.

Mini-thoracotomy for diaphragmatic plication with thoracoscopic assistance

We describe a technique of mini-thoracotomy to plicate the paralyzed hemidiaphragm with thoracoscopic assistance. Most of the hemidiaphragm can be plicated expeditiously under direct vision with light derived from a posterior thoracoscope placed in the auscultatory triangle. Videoscopic vision is employed only occasionally when the view of the posteromedial hemidiaphragm is obscured. Continuous suture traction can be easily applied through the mini-thoracotomy, thus maintaining suture tension and enabling maximal inversion of the elevated hemidiaphragm.

Variables predicting reintubation after cardiac surgical procedures

BACKGROUND

This study sought to determine patient characteristics, processes of care, and intermediate outcomes as predictors of reintubation after cardiac surgical procedures.

METHODS

We performed a retrospective case-control study that included all patients undergoing cardiac surgical intervention who required reintubation and an equal number of control patients not requiring reintubation. Putative risk factors were analyzed univariately by chi2, Fisher exact, Student's t, or Mann-Whitney tests. A logistic regression model was developed using data from patients requiring reintubation for cardiorespiratory reasons.

RESULTS

Of the 1,000 consecutive patients reviewed, 41 (4.1%) required reintubation (30 [3%] for cardiorespiratory reasons and 11 [1.1] for unplanned operations). Univariate predictors of reintubation (p<0.05) were older age, chronic obstructive pulmonary disease, New York Heart Association functional class IV, preoperative renal failure, lower arterial oxygen tension, insertion of intraaortic balloon pump, longer time in the operating room, longer duration of cardiopulmonary bypass times, positive fluid balance, postoperative renal failure, and worse pulmonary mechanics. Patients requiring reintubation also required a longer initial period of mechanical ventilation (median, 16.3 versus 6.0 hours; p<0.05). Excellent prediction was found with a model consisting of four variables: operating room time, respiratory rate, vital capacity, and chronic obstructive pulmonary disease.

CONCLUSIONS

Patients who required reintubation were sicker and had worse respiratory function and more comorbidity. Prompt extubation did not contribute to reintubation. Patients identified as having a high risk for reintubation should be followed up closely, and interventions should be directed to treating the problems leading to reintubation.

Phrenic nerve injury following cardiac surgery: a review

Phrenic nerve injury following cardiac surgery is variable in its incidence depending on the diligence with which it is sought. Definitive studies have shown this complication to be related to cold-induced injury during myocardial protection strategies and possibly to mechanical injury during internal mammary artery harvesting. The consequences are also variable and depend to a large extent on the underlying condition of the patient, particularly with regard to pulmonary function. The response of the patient may range from an asymptomatic radiographic abnormality to severe pulmonary dysfunction requiring prolonged mechanical ventilation and other associated morbidities and even mortality. Two cases are presented to demonstrate the variability in clinical responses to diaphragmatic dysfunction secondary to phrenic nerve injury from cardiac surgery. In addition, treatment strategies are reviewed including early tracheostomy and diaphragmatic plication, which appear to be the most effective options for patients who are compromised by phrenic injuries.

Iatrogenic nerve injuries

Iatrogenic nerve injuries are an undesired byproduct of the practice of medicine and have been so since antiquity. The majority of such injuries occur perioperatively, and are, therefore, attributed to surgeons and anesthesiologists. Nonetheless, the members of almost every clinical specialty are at risk to some degree. Iatrogenic nerve injuries can affect almost any portion of the peripheral nervous system, and can result from many different causes. This article reviews many of the more common iatrogenic nerve lesions.

Topical hypothermia: ineffective and deleterious as adjunct to cardioplegia for myocardial protection

BACKGROUND

Topical hypothermia, an early method developed for myocardial protection by virtue of its reduction of cardiac metabolic rate, is not without sequelae such as phrenic nerve paralysis and pulmonary complications.

METHODS

The hospital records of 505 nonrandomized consecutive patients undergoing coronary artery bypass grafting between 1991 and 1995 at the University of South Alabama were reviewed to evaluate the effectiveness of topical hypothermia and its relationship to pulmonary complications. Group A included 191 patients between 1991 and 1992 who received systemic hypothermia and topical hypothermia with iced slush in addition to cold blood cardioplegia. Group B included 314 patients between 1993 and 1995 who received systemic hypothermia and intermittent cold blood cardioplegia without iced slush.

RESULTS

Myocardial temperature mapping did not reveal any difference between the two groups. Postoperative cardiac morbidity, manifested as intraaortic balloon use, low cardiac output, inotrope use, and perioperative myocardial infarction, was decreased in group B, but the difference failed to achieve statistical significance. Mortality (group A, 3.14%; group B, 3.82%) and rates of significant morbidity such as sternal infection, stroke, reoperation for bleeding, renal failure, and prolonged ventilation were comparable between the two groups. However, there was a statistically significant difference in the incidence of diaphragmatic paralysis between group A and group B. Group A had a 25% incidence of diaphragmatic paralysis on the first postoperative day, 18% on the 15th postoperative day, and 8% at 6 months, as opposed to group B, which had incidences of 2% on the first postoperative day, 1% on the 15th postoperative day, and 1% at 6 months (p < 0.001). Also, there was a significant difference in incidence of pleural effusions (60% versus 25%) and rate of thoracentesis (25% versus 8%) between groups A and B (p < 0.0001).

CONCLUSIONS

We conclude that topical hypothermia did not offer any additional cardioprotective benefit above systemic hypothermia and cold blood cardioplegia alone in coronary bypass patients, but significantly increased the incidence of diaphragmatic paralysis and associated pulmonary complications.

Southwestern Internal Medicine Conference: preoperative pulmonary evaluation

The purpose of preoperative pulmonary assessment is to predict which patients are at greater risk of pulmonary complications, under which circumstances such complications may occur, and whether surgery should be denied based on that risk. In this article, the author addresses the following major issues in preoperative pulmonary assessment: 1) the risk of pulmonary complications in relation to the type of surgical procedure; 2) the value of preoperative pulmonary function testing, including when such testing should be performed and how the results should be used; and 3) guidelines for assessment of those patients about to undergo resectional surgery of the lung.

Warm heart surgery eliminates diaphragmatic paralysis

Since January 1992, we adopted a new method of myocardial protection: warm blood cardioplegia with continuous ante-retrograde combined delivery during normothermic cardiopulmonary bypass, (CPB) instead of cold blood intermittent cardioplegia plus topical ice slush in hypothermic CPB. We have compared postoperative chest X-rays of 50 patients who underwent elective coronary artery bypass with normothermic CPB to postoperative chest X-rays, of 50 patients operated upon with hypothermia. In the cold group transitory diaphragmatic paralysis, as well as pleural effusions and thoracentesis related to the hypothermia, and topical cooling, were statistically increased over that of warm group. The data suggest that topical cooling with slush ice is responsible for phrenic nerve injury and that warm heart surgery has no associated incidence of diaphragmatic injury.

Phrenic nerve injury following scalenectomy in a patient with thoracic outlet obstruction

We present a case in which a patient with normal pulmonary reserve experienced orthopnea and hypoxia secondary to unilateral diaphragmatic paralysis following right scalenectomy. This operation was performed in an attempt to relieve neurovascular compromise at the thoracic outlet. To our knowledge, this association has not been previously described in the literature.

Lack of association between atelectasis and fever

Postoperative fever occurs in many patients. If no infection is found, atelectasis, if present, may be blamed. This study of 100 postoperative cardiac surgery patients followed up from day of surgery through the second postoperative day with daily portable chest radiographs and continuous bladder thermometry was designed to look for an association between atelectasis and fever. The daily incidence of atelectasis increased from 43 to 69 to 79%. However, the incidence of fever, defined as temperature > or = 38.0 degrees C fell from 37 to 21 to 17%. When defined as temperature > or = 38.5 degrees C, the daily incidence of fever fell daily from 14 to 3 to 1%. Using chi 2 analysis, no association could be found between fever and amount of atelectasis. This contradicts common textbook dogma but agrees with previous human study and animal experiments.

Surgical anatomy of the phrenic nerve and internal mammary artery

Dissection of the thoracic inlet was performed on 22 cadavers to determine the relationship of the phrenic nerve to the internal mammary artery as it passes from lateral to medial behind the first rib. On the left the nerve was found to cross superior to the artery and then medial to it in 14 of 22 specimens; on the right this was found in ten of 22 specimens. In all other specimens, it crossed inferior to the internal mammary artery. These findings demonstrate that there is no constant relationship between these structures, and emphasize the need for caution when dissecting the internal mammary artery at or above the level of the first rib.

Diabetes mellitus, internal thoracic artery grafting, and risk of an elevated hemidiaphragm after coronary artery bypass surgery

The elevated hemidiaphragm after coronary artery bypass grafting (CABG) that occurs in some patients is associated with internal thoracic artery (ITA) grafting as well as with the use of topical cardiac hypothermia. An increased incidence of elevated hemidiaphragm after CABG surgery in diabetic patients was observed. To determine the incidence and risk factors of elevated hemidiaphragm after CABG surgery and the relationship to preoperative diabetes, 200 consecutive patients undergoing CABG were studied; 29 (14.5%) had hemidiaphragm elevation postoperatively (25 on the left, 1 on the right, 3 bilateral). In the remaining 171 there was no hemidiaphragm elevation. Factors analyzed were age, gender, preoperative diabetes, duration of cardiopulmonary bypass (CPB) and aortic cross-clamping, minimum esophageal temperature during CPB, and use of the ITA graft. Univariate analysis showed a significant association between elevated hemidiaphragm and diabetes (P < 0.05), left ITA grafting (P < 0.01), and age (P < 0.05). Right ITA was not used for any patient. Multivariate analysis ruled out age, whereas preoperative diabetes and the use of the ITA remained the independent factors associated with elevated hemidiaphragm (odds ratio, 3.41; 95% confidence interval 1.41 to 8.18, and 2.86; 1.01 to 8.06, respectively). The relative risk of an elevated hemidiaphragm was 9.75 in diabetic patients with the ITA graft, as compared with nondiabetic patients without this graft. All 3 patients with bilateral diaphragm paralysis and a patient with a right hemidiaphragm elevation were diabetic. In conclusion, both diabetes and use of the ITA graft appear to be important risk factors for the development of elevated hemidiaphragm following CABG.(ABSTRACT TRUNCATED AT 250 WORDS)

Fatal bilateral phrenic nerve injury following hypothermic open heart surgery

A 30-year-old woman underwent mitral valvotomy for severe mitral stenosis. Extracorporeal circulation by means of cardiopulmonary bypass and systemic hypothermia, in addition to local topical hypothermia using iced saline solution and slushed ice, was used. Fatal bilateral phrenic nerve paralysis with inability to wean her from the ventilator occurred. This report is presented to illustrate the pathophysiology, pathology, and means of possible prevention of such a potentially highly fatal injury following hypothermic open heart surgery.

Phrenic nerve damage via a right thoracotomy in older children with secundum ASD

Phrenic nerve damage (PND) in children after cardiac operations is now recognized as being more frequent than previously thought. In a prospective study on 400 children, we previously demonstrated electrophysiologic evidence of postoperative PND in approximately 16% of patients, with one third of cases occurring in children under 18 months. In the past 18 months, 30 children have had atrial septal defect (ASD) repairs as their only operative procedure. Fourteen children had ASD repairs via a midline incision, and 16 ASD repairs were via a right thoracotomy. No PND (assessed by phrenic nerve latency) was found after a midline approach. In the right thoracotomy group, 5 children had evidence of PND (31%; p = 0.05). Four of these 5 patients were female and more than 14 years of age. The incidence of damage in this pubescent group was 80% (p < 0.05). In the older age group the duration of ventilation was not prolonged, but affected patients had symptoms of fatigue and breathlessness postoperatively. These data suggest a strong association between right thoracotomies for ASD repairs and PND, especially in the female pubescent group when a low submammary skin incision (seventh to eighth space) is used with a fifth to sixth space entry into the thoracic cavity. In conclusion, the right thoracotomy approach for ASD repair appears to be a significant risk factor for PND in older children.