Peripheral Nerve Injuries During Cardiac Surgery: Risk Factors, Diagnosis, Prognosis, and Prevention

Neuropathies involving the brachial plexus, phrenic, recurrent laryngeal, and saphenous nerves, as well as the sympathetic chain are complications of cardiac surgery. The reported frequency of nerve injuries varies from 1.5% to 24% for the brachial plexus and 10% to 60% for the phrenic nerve (1–5). Neuropathies of the recurrent laryngeal, lower limb (saphenous) nerves, and the sympathetic chain are less frequent. This review will focus on the risk factors, diagnostic modalities, prognosis, and preventive measures that can be used to reduce the severity and frequency of neuropathies after cardiac surgery. Particular attention will be directed to discussion of brachial plexus and phrenic nerve injury. Brachial Plexus Neuropathy During Cardiac Surgery Brachial Plexus Anatomy The brachial plexus is formed by the anterior rami of the fifth to eighth cervical and the first thoracic spinal nerves (6). After exiting from the intervertebral foramina, the roots of the brachial plexus pass inferiorly between the middle and anterior scalene muscles combining to form the superior, middle, and inferior trunks. In this position, the brachial plexus is invested in a fascial covering that represents an extension of the prevertebral fascia. As the three trunks pass over the first rib and under the clavicle, they split into divisions, recombining to form the cords that pass down through the axilla. There are three principal anatomical features that make the brachial plexus susceptible to neuropathy. First, its superficial location makes it susceptible to direct damage. Second, the nerve roots of the brachial plexus are fixed both proximally at their site of origin (the intervertebral foramina) and distally where they are tethered to the investing fascia, muscles, and other tissues. As a result, force applied between these points increases the likelihood of producing a stretch neuropathy (7). Third, the space between the first rib and the clavicle is limited. Thus, fracture and/or displacement of the first rib can directly damage the brachial plexus (7). Cell bodies in the dorsal root ganglion provide a continuous supply of nutrients distally to the peripheral axons. Any injury that interferes with this supply can damage the nerve. In 1973, Upton and McComas (8) described the “double crush” hypothesis to explain nerve entrapment syndromes. This hypothesis states that two relatively minor nerve lesions, which by themselves are incapable of producing significant nerve damage, can combine to produce a significant lesion. For example, clinically silent ulnar nerve entrapment in the cubital tunnel (present preoperatively) may be converted to an overt ulnar neuropathy by a minor stretch neuropathy to the lower trunk of the brachial plexus during sternal retraction. This hypothesis may hold true for many brachial plexus injuries after cardiac surgery. However, despite the wide acceptance of this double crush hypothesis by the medical community, serious questions have been raised about this concept because no experimental studies have shown conclusively that double lesions across a nerve cause magnified damage (9–12). Risk Factors for Brachial Plexus Neuropathy Sternal Retraction and Internal Mammary Artery Dissection. Sternal retraction is one of the key factors responsible for brachial plexus neuropathy. As discussed previously, the anatomical features of the brachial plexus render it susceptible to stretch injury. In 1971, Kirsh et al. (7) performed sternal retraction in human cadavers and demonstrated that retraction produced superior rotation of the first rib and pushed the clavicles into the retroclavicular space, thereby stretching the brachial plexus (Figure 1). This stretching may be made worse by subsequent turning of the head to the contralateral side (13).Figure 1: A, Normal course of the brachial plexus as it passes over the first rib. B, Opening the sternum widely causes superior rotation of the first rib that pushes the clavicles into the retroclavicular space leading to stretching of the brachial plexus. Reprinted with permission (7).Direct trauma of the brachial plexus can occur by first rib fracture fragments or the associated fracture hematoma directly compressing the nerves (Figure 2) (14,15). Posterior fractures of the first rib can easily remain undiagnosed by routine radiography. The incidence of upper rib fractures after median sternotomy is uncertain. The radiographically reported frequency of first and second rib fractures varies from 4% to 16% (16–18). Greenwald et al. (16) prospectively studied 24 patients undergoing cardiac surgery with pre- and postoperative chest radiography and postoperative bone scans. Bone scans revealed 44 rib fractures, 30 on the left and 14 on the right. In contrast, chest radiography revealed only one rib fracture. On retrospective review of chest radiography, only three new fractures could be identified. Posterior fractures of the first rib were the most common site of fractures. In addition to their potential adverse effects on the brachial plexus, the authors suggested that rib fractures should be included in the differential diagnoses of unexplained postoperative nonincisional chest pain and that bone scans were more sensitive than chest radiography in diagnosing rib fractures.Figure 2: Autopsy findings: posterior first rib fracture fragments penetrating the brachial plexus. Reprinted with permission (14).There are several commonly used sternal retractors. Most of the studies have been conducted with the Cooley and the Ankeney retractors. Several studies have shown that the more caudal placement of the retractors within the sternotomy is associated with a reduced incidence of first rib fractures (1,2,19). The optimal placement of the retractor is controversial. Vander Salm et al. (14) studied the placement of sternal retractors and first rib fractures in 20 noncardiac patients who had autopsies performed through a median sternotomy. They found that the frequency of first rib fractures was completely eliminated by placing the cephalad blade of the sternal retractor in the fourth intercostal space. In contrast, 11 patients had first rib fractures demonstrated by chest radiography when the cephalad blade was placed in the second intercostal space. These authors suggested that, by placing the retractor in the cephalad position, the upper portion of the sternum is spread less and may result in less pressure transmitted to the first rib with a resultant decreased frequency of first rib fractures. Tomlinson et al. (19) prospectively studied 335 cardiac surgery patients undergoing median sternotomy both preoperatively and five to seven days postoperatively for evidence of brachial plexus injury. Patients with abnormal neurological findings were subsequently examined at two-day intervals until discharge. Diagnosis was made after detailed sensory and motor evaluation of muscle groups innervated by the brachial plexus. They attributed the decreased frequency of brachial plexus neuropathy (4.8%) on the relative caudal placement of the Cooley-type sternal retractor. Baisden et al. (1) prospectively studied 36 consecutive cardiac surgery patients undergoing median sternotomy. All patients had preoperative and postoperative chest roentgenograms as well as radionuclide bone scans 7 to 14 days after surgery. By removing the uppermost pair of blades from the Ankeney retractor, they were able to reduce the frequency of first rib fractures from 50% to 16%. Some of the commonly used internal mammary artery (IMA) dissection retractors are the Pittman™ (Minnesota Scientific Instruments Inc., Minneapolis, MN) (Figure 3A), Rultract™ (Rultract Inc., Cleveland, OH) (Figure 3B), and Delacoix-Chevalier™ (Delacoix-Chevalier, Paris, France) (Figure 3C). Jellish et al. (20) prospectively studied the effect of these three sternal retractors on brachial plexus in patients undergoing Artery surgery with an to the retractor performed detailed motor and sensory of the brachial plexus. were by an to the of retractor In to the patients in the Pittman™ and Rultract™ they demonstrated that patients in the Delacoix-Chevalier™ had in after retractor placement that dissection retractors produce effects on the brachial plexus. This may be to the that the Pittman™ and the Rultract™ retractors the sternal the Delacoix-Chevalier™ pushes the sternal and the sternal with on the sternum and brachial plexus. in the of associated with the of the Delacoix-Chevalier™ retractor, was no in frequency of postoperative brachial plexus neuropathy the three The Pittman™ (Minnesota Scientific Instruments Inc., Minneapolis, MN) (Rultract Cleveland, OH) and Paris, France) retractors. Reprinted with permission a of 44 the of the effect of the Rultract™ and Pittman™ retractors on brachial plexus They demonstrated that, both these retractors were associated with in as with were more and more common in the Rultract™ than in the Pittman™ despite these no in the frequency of brachial plexus neuropathy could be between the two The of been to brachial plexus et al. studied cardiac surgery patients prospectively and demonstrated that the frequency of neuropathies in patients was as with in They that dissection a more sternal for to an in brachial plexus and subsequent neuropathy. The authors suggested that retractors should be used with have the of between brachial plexus neuropathy and dissection to with brachial plexus neuropathy have produced studies by and that as of the to no more than anterior of the and of the the was associated with less and of the brachial plexus. The authors the produced by on the brachial plexus in was by and and was from to In their of 335 Tomlinson et al. (19) attributed the frequency (4.8%) and course of brachial plexus neuropathy to this There was no in this Vander Salm et al. (14) prospectively studied patients with to during cardiac surgery and brachial plexus neuropathy. The frequency of neurological was with the by the side than with to this was significant In a this Jellish et al. prospectively studied the effect of as to no more than and of the or by the side on brachial plexus during sternal retraction for in their that was associated with a lower frequency of this in a lower frequency of postoperative brachial plexus This was to this in the are no more than with applied under the to the 20 the Reprinted with permission The internal is to the brachial plexus. of the internal may to direct injury to the brachial plexus, of the internal been shown to be associated with an frequency of brachial plexus et al. in of cardiac surgery patients found that, in of the the side of the brachial plexus injury with the side of internal This was because brachial after surgery occur on the left side most the internal is for In to this by et al. in which internal was performed after the patients were many are with the and pain be the the brachial plexus the of brachial plexus injury. most patients who internal are cardiac surgery. The frequency of brachial plexus neuropathies in this noncardiac surgery is have found the between internal and brachial plexus neuropathy and been to brachial plexus neuropathy of and of to be significant risk factors The of during or of used have been associated with frequency of brachial plexus neuropathies after surgery Diagnosis of Brachial Plexus Neuropathy The of brachial plexus neuropathies after cardiac surgery stretching of the lower roots to of sternal retractors and postoperatively as ulnar neuropathy where the ulnar nerve can be the of the muscle the ulnar at the cubital and the of the of the brachial plexus a detailed of upper of to and of motor of muscle groups innervated by the brachial plexus. evaluation of the and rotation of the and of the ulnar and and and extension of the and and extension of the and extension of the and motor associated with ulnar neuropathy can on the site of nerve damage 1: with et al. studied ulnar neuropathy in patients The frequency of ulnar neuropathy in noncardiac patients as sensory or motor than was in a of patients In contrast, the frequency of ulnar neuropathy (the most common form of brachial plexus in cardiac surgery patients is to and patients who to a with brachial over They of brachial plexus neuropathy during this and that cardiac surgery is associated more with brachial plexus neuropathy to the lower roots as with upper and middle root with noncardiac brachial plexus neuropathy after cardiac surgery in sensory as with relatively motor associated with noncardiac surgery plexus brachial plexus neuropathy after cardiac surgery is associated with a more as with noncardiac surgery. et al. and and of as for the of postoperative ulnar neuropathy in noncardiac an been with cardiac surgery studies can in nerve during the these are sensitive and postoperative the of studies in the and of brachial plexus neuropathy are of motor and sensory and are of the common motor and sensory can be across the and neuropathies are associated with of nerve et al. prospectively studied ulnar nerve in 20 patients after cardiac and to They of more than in the relative to the significant for ulnar neuropathy. 7 patients had ulnar nerve of more than with and more than in of the postoperative of more than in of preoperative ulnar However, were no significant in the 7 ulnar nerves in which preoperative was more than one of three with significant evidence of ulnar neuropathy. This demonstrated that of patients had preoperative across the ulnar nerve. However, ulnar neuropathy after surgery was by the preoperative of the ulnar nerve. In contrast, et al. prospectively studied from median and ulnar nerves in 30 patients undergoing cardiac surgery. They a three in and in of postoperative brachial plexus neuropathy. In their an to the of brachial plexus neuropathy in the postoperative They demonstrated that was associated with in of of of sternal retractors was associated with significant in of In of to and demonstrated postoperative brachial plexus The of the patients demonstrated postoperative neurological In of these five associated with sternal retraction until the of surgery. The authors suggested that upper be used to postoperative peripheral nerve injury. However, et al. found no between with and postoperative brachial plexus neuropathy. of are studies are routine in an to reduce the frequency of postoperative brachial plexus the true of is as the of studies have had to of Brachial Plexus Neuropathy The of brachial plexus neuropathies after cardiac surgery is However, to one at with been reported In a of 335 Tomlinson et al. (19) reported brachial plexus neuropathy in only of patients to have postoperative brachial plexus neuropathy. The patients (4.8%) were at the of discharge. et al. studied patients prospectively and the of brachial plexus neuropathy was made in of only of of patients had for more than et al. in a of that of patients had for more than three of Brachial Plexus Neuropathy that, despite optimal and brachial plexus neuropathies can Factors that may reduce the frequency of brachial plexus neuropathies sternotomy to subsequent sternal more caudal placement of the sternal retractor, of sternal and of head of these have reduced the frequency or severity of brachial plexus Neuropathy During Cardiac Surgery Anatomy The phrenic nerve from the fourth cervical nerve with from the and fifth cervical The left phrenic nerve passes cephalad through the thoracic between the and the of the in with the In contrast, the phrenic nerve is more to the and superior (6). Risk Factors for Neuropathy In et al. used for or in with is a in cardiac surgery. to was described by et al. who to phrenic neuropathy as neuropathy is well with is associated with a in nerve with at On nerves a wide of from to Several studies have demonstrated as the principal cause of postoperative phrenic neuropathy et al. in both a and retrospective of chest from cardiac surgery examined the frequency of new left lower They attributed left lower to left by left phrenic nerve or They demonstrated a of frequency of left lower when was In contrast, in in which with was the frequency of left lower was of in the retrospective and of in the In the of had left or as demonstrated by of the left on radiography. In a et al. demonstrated of the left with in of patients after cardiac In the of these the left phrenic nerve was The for this was the of the left phrenic nerve with the can be by the of or it that is more than Internal Mammary Artery Dissection. dissection during been in postoperative phrenic neuropathy. et al. performed phrenic nerve studies in surgery patients that were to from In of the was between the side of and The for the of dissection with phrenic neuropathy could be direct damage during dissection or phrenic nerve after of the phrenic nerve. However, the between dissection and phrenic neuropathy is and by the that the left is the most used and the left phrenic nerve is more susceptible to as discussed et al. prospectively patients undergoing surgery and found no between left dissection and phrenic neuropathy. In an et al. studied the effects of left dissection on phrenic nerve In the first the left was completely with of its This in a in left phrenic nerve with on the In the second left dissection was the a that the phrenic nerve. In this left phrenic nerve was decreased by only The authors that left dissection with of the artery to of the supply to the phrenic which may the effect of phrenic neuropathy. The origin of the artery in is and from the upper to of the left and the of to have no to postoperative phrenic neuropathy Diagnosis of Neuropathy Some of the commonly used to phrenic neuropathy chest radiography, and phrenic nerve The used to phrenic neuropathy a postoperative of the in to the by one intercostal space than that on preoperative chest This is with phrenic neuropathy because and postoperative can the Thus, the of chest findings for phrenic nerve injury is In an is in to of patients after cardiac surgery. However, chest findings of phrenic neuropathy can be when at in the in the This is in the position, of the muscles can the during during in the position, muscle can of the despite chest have a of the can be with and because the the and pushes the the during in patients with phrenic neuropathy can or a of the However, can be made by the of and In to the between two directly the In patients with phrenic can a or can in the of phrenic neuropathy. et al. demonstrated muscle with a on in patients with phrenic nerve injury. in the of neuropathies an to to and decreased of the potential a its more of can in phrenic neuropathies motor motor potential and The of is of damage. In a et al. examined the incidence of phrenic neuropathy in that of the patients had abnormal postoperative chest was the most common chest by an of had abnormal by of of the patients with abnormal had abnormal nerve Thus, of the had findings on chest and with phrenic of these the left phrenic nerve. In patients in this with and nerve than with abnormal and nerve in cardiac patients is and a of to to phrenic after surgery is to be by injury to the phrenic The first of phrenic neuropathy may be in patients from of the for pressure chest radiography and is in In of the pressure by and may be the only diagnostic for pressure and pressure pressure et al. found in patients with that to a in both and and that during pressure to 20 a to of and an in nerve can be by direct of the nerve at the cervical and at the intercostal space. et al. prospectively in patients undergoing surgery. of the three patients with overt phrenic neuropathy. In this the authors suggested that postoperative may be in patients when was and during from studies are to in on phrenic nerve can reduce postoperative phrenic neuropathy. In of is no for the of phrenic neuropathy radiography a have the and is of neuropathy. may be of or phrenic neuropathies can be by may be by and of Neuropathy In the and from phrenic neuropathy is is associated with to no because of of and intercostal muscles to with The most common of patients with phrenic neuropathy are as well as with et al. found that was no in the of and postoperative complications at in patients with phrenic nerve with with phrenic neuropathy. In of muscles to with may be as a result of pain from chest and a sternotomy This may to in and chest is most that by phrenic nerve is because of There are no studies that have the of of phrenic neuropathy. The for phrenic nerve on the of injury and the over which is of phrenic nerve In with with the of from and may or after is several several and may be The of phrenic neuropathies after surgery by to There are no studies that have the course of phrenic neuropathies in to the In the with phrenic neuropathy can have than in the of Patients with have a and the of phrenic nerve injury can to in et al. in a of patients with demonstrated that patients with who had phrenic neuropathy during surgery had and more and as well as decreased is a serious medical by can on the and of muscles, patients with may during have serious during et al. reported of these patients had and a 50% in in the phrenic neuropathy a course of with significant associated the patients studied by et al. and et al. one of after and in the other phrenic nerve by the of these patients pressure at to with The of phrenic neuropathy in the from et al. found the frequency of phrenic nerve in cardiac surgery patients to be In phrenic nerve was a in and The authors several after phrenic nerve First, the intercostal muscles of the are and their result in an in the on for Second, as a result of in the is more common in the of Third, the of the is and of the can the to the with the in causes a in of Neuropathy can be from damage by the of an of or of a This may be the neuropathy a wide of features and occur in phrenic et al. used a cardiac They prospectively studied patients undergoing patients to two of consecutive patients undergoing surgery the of and of the in the was nerve injury was on the of of the in the postoperative chest after with the preoperative chest In their 60% of the patients who for demonstrated left and left lower In contrast, only of the patients demonstrated evidence of after the of The authors that the of the the of decreased the risk of the phrenic nerve to neuropathy. Several other can be that may reduce postoperative phrenic neuropathy. dissection of the with attention to of the artery may be in the well for of into the during dissection to of in the may be In risk may be to the of or on a studies are to more this Neuropathy During Cardiac Surgery with brachial plexus and phrenic by damage of the recurrent nerve after cardiac surgery is less The frequency of in patients postoperatively varies from to The left recurrent nerve to the in the upper and posterior of the thoracic as it the of the the is during dissection and of are in the the left recurrent nerve can neuropathy nerve can be during placement and dissection or may to the may cause damage to the anterior of the recurrent nerve that is to the cords The of been examined as a et al. reported that of patients in a was placed and of in was used were with recurrent neuropathy This was and the authors that the of in cardiac surgery patients was associated with an frequency of recurrent neuropathy. The authors that the of and were in patients with recurrent neuropathy. This should be in patients who and after is associated with which in may be associated with The of recurrent neuropathy can be by neuropathy to to Most patients can be may and potential or into the cords to and to the Neuropathy After Cardiac Surgery of the as a the saphenous to be widely used for surgery. The saphenous a sensory of the nerve by the nerve roots the in the superficial in the lower with the saphenous the the of the through its two and the of the saphenous nerve the saphenous in the two of the The saphenous nerve is in with the of the at the injury to the saphenous the is a during saphenous to the saphenous nerve commonly as saphenous that is with the of and pain the side of the and to the of the et al. reported that the frequency of saphenous varies from after surgery to 10% at and demonstrated that of the lower examined after saphenous of at days with after 20 et al. found that the incidence of postoperative after saphenous was in patients was in two and as with one They attributed this to a from the pressure by the across the They of the after of the saphenous The of saphenous dissection may the frequency of saphenous et al. demonstrated that in the saphenous was in the dissection from the and as with the dissection from the and had significant sensory in the saphenous nerve at postoperatively the were After the authors that saphenous dissection to the of the and/or the of the saphenous nerve more than in dissection performed in the in many cardiac saphenous is The of the saphenous with may result in less and hematoma et al. prospectively patients to or saphenous the and the postoperative pain in the of the saphenous nerve was on a from to described as and as no pain at that pain was reduced in the with a of in the and in the The authors this in pain was studies are to result in less saphenous nerve injury and saphenous Neuropathy After Cardiac Surgery The cervical sympathetic chain to the inferior trunk of the brachial plexus as it over the first it to injury the as the brachial plexus. Vander Salm et al. (14) demonstrated that sternal retraction could to posterior first rib fractures, which could directly damage the cervical sympathetic chain neuropathy by and et al. of patients with postoperative In it was and associated with neuropathy to the inferior trunk of the brachial plexus. for more than in two of these patients the other two within studied preventive to for brachial plexus neuropathies may the frequency of sympathetic chain neuropathies after cardiac surgery. In nerve injuries after are well They are a significant of for patients and potential for et al. in the that neuropathies after surgery were the second most common surgery is associated with neuropathies involving the brachial plexus, phrenic, and saphenous nerve. the of patients In a of these neuropathies can be associated with postoperative preventive may reduce both the frequency and severity of these