Artery Bypass Grafting

Delayed tetraplegia after CABG surgery Acute Delayed-onset Tetraplegia after Coronary Artery Bypass Grafting Wei-Cheng Liu 1, Chin-Chen Chu 2, Yao-Tsung Lin 3, Chung-Hsi Hsing 2, Li-Kai Wang 2, Jen-Yin Chen 2, Ming-Chung Lin 3 Abstract Postoperative tetraplegia after coronary artery bypass graft (CABG) surgery is extremely rare and mostly due to posture-related exacerbation of preexisting cervical spondylotic myelopathy (CSM). Most of the previous reported cases were diagnosed immediately after emergence from general anesthesia. However, the patient we brought here developed delayed but abrupt onset of tetraplegia after CABG surgery. The cervical magnetic resonance imaging revealed CSM and severe stenosis of right vertebral artery. Acute exacerbation of CSM superimposed with vascular ischemic infarction of his cervical cord was speculated. The neurological prognosis of complete postoperative tetraplegia is poor in general and in this case, despite of supportive care concomitant with or without urgent surgical decompression. Thorough preoperative history taking and neurological examinations, careful positioning of the neck while performing procedures intraoperatively and even postoperatively might be helpful to prevent such complication, when dealing with patients of CSM. Key Words: coronary bypass, spondylosis, myelopathy, spinal cord infarction, tetraplegia Introduction Tetraplegia is a rare complication after major cardiovascular surgery and may cause significant mortality and morbidity. Most previous cases were reported after aortic surgery while only few ones were reported after cardiac surgery. Further, for these few cases, the majority were noted immediately after operation. Here we present a case with delayed but abrupt onset of tetraplegia after coronary artery bypass graft (CABG) surgery and briefly discuss the possible causes, management, and preventive measures of the catastrophic complication. Case Report A 56-year-old man, weighting 75 kg and standing 166 cm, scheduled for CABG surgery due to unstable angina. He had the following co-morbidities, such as diabetes mellitus, hypertension, chronic renal insufficiency, and episodes of transient ischemic attack. Preoperative cardiovascular history includes an episode of severe acute myocardial infarction (Killip IV) seven years ago, rescued by Correspondence: Dr. Ming-Chung Lin Department of Anesthesiology, Chi Mei Medical Center, Liouying; 201, Taikang, Taikang Village, Liouying District, Tainan City 73657, Taiwan 3 Phone: +886-6-281-2811 ext. 53321; E-mail: mygegon@gmail.com Department of Anesthesiology, Chi Mei Medical Center, Chiali, Tainan, Taiwan 1 Department of Anesthesiology, Chi Mei Medical Center, Tainan, Taiwan 2 151

Wei-Cheng Liu et al. successful percutaneous transluminal coronary angioplasty with stenting. This time, he received CABG surgery for his restenotic left anterior descending artery and left circumflex artery, using his left internal mammary artery and left great saphenous vein grafts respectively. The patient s preoperative neck and neurological evaluations were normal in general. His Mallampati classification was scored one. The vital signs before anesthesia showed BP 156/107 mmhg, HR 81 bpm, and SpO 2 97%. General anesthesia was induced with succinylcholine, fentanyl, thiopental and rocuronium. Orotracheal intubation was performed smoothly without the need of excessive neck extension by conventional laryngoscopy. Subsequently, the transesophageal echocardiography (TEE) probe and the central venous catheter were also inserted without difficulties. The patient was then positioned with a 5 cm-thick gel pad placed below the patient s shoulder and with a gel donut pad placed below his head to achieve a slightly neck-extended position for sternotomy and surgical exposure. The patient s cardiac functions and hemodynamics were monitored with TEE, arterial blood pressure, central venous pressure and pulse oximeter throughout the operation and were optimized using intravenous fluid supplement or titration of inotropic agents accordingly. During cardiopulmonary bypass (CPB), the patient was perfused by a roller pump at a flow rate of 2.4 L/min/m 2 to achieve the mean arterial pressure between 50-60 mmhg. The mean body temperature was maintained at 32 C and the hematocrit was kept at around 25% during CPB. Both the anesthetic and operative course were uneventful. It took about eight hours to complete the surgery, the time of CPB and aortic crossclamp was 110 min and 83 min respectively. The patient was then sent to the intensive care unit without mechanical circulatory support. When the patient awoke five hours after operation, his muscle power was graded as two to three out of five (2-3/5) for four limbs. Subsequently, he underwent two times of routine neurologic examinations at the 8th and 10th-postoperative hour and showed clear consciousness and acceptable muscle power (4-5/5) for all limbs. Sixteen hours after operation, we removed his endotracheal tube. Nevertheless, acute deterioration of the muscle power of his four limbs developed soon after extubation (2/5 in upper limbs; 0/5 in lower limbs). Under the impression of acute cervical spinal cord injury, a neck collar was applied and emergent magnetic resonance imaging (MRI) of his neck was arranged. The MRI scan revealed cervical spondylotic changes with C2-C6 and C4-C5 intervertebral disc herniation, along with marked swelling and edematous changes in the C3- C6 spinal cord, constituting the diagnosis of cervical spondylotic myelopathy (CSM) (Fig. 1). Based on this diagnosis, steroid therapy was initiated immediately and emergent surgical decompression including C3-C5 laminectomy and C4-C5 discectomy was performed two hours later. Unfortunately, loss of sensory and motor function below C5 level persisted after the surgery. Fig. 1. The T2-weighted image of cervical spine MRI obtained soon after the onset of tetraplegia. The image revealed cervical spondylotic changes with spur formation and intervertebral disc herniation at the level of C2-C6. Central hyperintensity and indentation of the spinal cord were also noted at the level of C3-C6. 152

Delayed tetraplegia after CABG surgery Fig. 2. The T2-weighted image of cervical spine MRI obtained eleven days after C3-C5 laminectomy and C4-C5 discectomy with anterior bone fusion. (A) The image showed swelling, edema and suspected hemorrhagic changes of the spinal cord at the level of C3-C6, and with extended central hyperintensity to the level of C6-T2. (B) The upward arrow indicates the severely stenotic right vertebral artery and the downward arrow indicates the normal left vertebral artery. Subsequent MRI scan obtained on the 11th day after decompression still showed swelling, edema and suspected hemorrhagic transformation among his C3-C6 spinal cord. Besides, the central lesion indicated by T2-weighted hyperintensity extended to the C6-T2 spinal cord (Fig. 2A). Severe stenosis of his right vertebral artery was also noted in the same examination (Fig. 2B). By the 35th postoperative day, there was only a slight improvement in the motor power of his upper limbs (3-4/5) and was no evidence of further improvements in his lower limbs (0/5). Consequently, he received tracheostomy for his respiratory insufficiency. Discussion The differential diagnoses of postoperative tetraplegia include acute exacerbation of CSM, direct compression of cervical spinal cord and spinal cord infarction. Direct spinal cord compression by epidural hematoma, abscess or disruption of intervertebral disc was immediately ruled out by the MRI examination. Whereas CSM caused by progressive spinal stenosis due to geriatric degeneration of the cervical spine could become aggravated during excessive flexion or extension of the neck. 1 Finally, spinal cord infarction which usually has an abrupt onset is mostly seen in patients under intra-aortic balloon pump (IABP) support after cardiac surgeries or with preexisting severe atherosclerotic diseases. 2 In addition, the microemboli developed during CPB or other factors compromising the blood supply to spinal cord might cause spinal cord infarction. 3 The first case of tetraplegia after CABG surgery was reported by Fujioka et al. who suggested the pathogenesis of acutely exacerbating CSM due to prolonged neck hyperextension intraoperatively. 4 There were several similar cases reported a few years later on. 5 In addition to the harmful effects of surgical positioning to the preexisting cervical spondylosis, spinal cord 153

Wei-Cheng Liu et al. edema from the fluid load and large volume shifts associated with the initiation and maintenance of CPB were also been proposed. 6 Whereas the case of tetraplegia after an uneventful off-pump CABG surgery reported by Li et al. 7 recently reemphasized the potential catastrophic impact of neck extension on patients with preexisting cervical spondylosis. There is one major difference between this case and the previous ones. All the previous cases developed their symptoms of limb weakness immediately after emergence from general anesthesia. 4,5,7 On the contrary in this case, he awoke without symptoms of tetraplegia postoperatively in ICU, followed by the additional two times of acceptable results of neurological examinations before extubation. The patient encountered delayed but sudden, explosive onset of tetraplegia after extubation. Considering the course of the event, it seems hard to be blamed for the intraoperative surgical positioning. It is more likely that the patient with this kind of clinical course suffered from acute spinal cord infarction which has an acute and often apoplectic onset evolving over minutes. 8 This possibility was further supported by the finding of severe stenosis of his right vertebral artery revealed in the followed MRI study (Fig 2B). Since vertebral arteries contribute significantly to the blood supply of cervical spinal cord, patients carrying a severe stenotic vertebral artery might potentially contract spontaneous spinal cord infarction. 9 Although patients with postoperative spinal cord infarction were reported mostly after aortic surgery or following the use of IABP, Spielmann et al. 3 reported a case who underwent CABG surgery without IABP support developed such complication, as happened in this patient. So far spinal cord ischemic infarction seemed to be the better answer. However, we could not simply exclude the possibility of acute exacerbation of CSM based on his initial MRI scan, showing the central hyperintensity lesion in the spinal levels that was just compatible with the sites of canal stenosis (Fig 1). Strenuous cough along with excessive neck movement during endotracheal suctioning and extubation might also precipitate the acute exacerbation of CSM. In fact, we speculated that both acute CSM and spinal cord infarction might synergistically contribute to the development of tetraplegia in this patient. The management for spinal cord infarction includes supportive treatment and close monitoring for possible complications, maintaining adequate perfusion pressure and avoiding systemic hypotension. Anti-platelet agents may be helpful but are contraindicated after major surgery. 3 On the other hand as to managing acute CSM, early surgical decompression or conservative treatment with steroid or free radical scavenger 4 are chosen according to multiple factors, including the extent of injury, the severity of paralysis, etc. Unfortunately, most patients suffering from tetraplegia after CABG surgery has very poor neurological outcomes regardless of the managing strategies. 4,5,7 Hence, prevention is better than cure. The cornerstone of preventing acute postoperative CSM is identifying the patients who are at risk beforehand. Thorough history taking and neurological examinations are the keys. Common symptoms of CSM include neck stiffness, arm/ shoulder pain, hand/leg weakness or stiffness. 1 Neurological examinations may reveal sensory loss over extremities, atrophy of the muscles of hands, hyperreflexia and positive Lhermitte s sign, which represents a electric shock-like sensation along the spine while patients flexing their necks. 1 C-spine MRI, the most accurate image modality in detecting myelopathy, should be considered if doubt. C-spine lateral film is also a useful alternative. An anterior-posterior diameter of cervical spinal canal less than 10 mm and/or the Pavlov ratio less than 0.8 demand further evaluation. 10 If cervical spinal stenosis is diagnosed preoperatively, excessive extension or movement of the patient s neck while intubation, positioning, or transferring should be avoided. Awake intubation and positioning, and the use of intraoperative neurophysiologic monitoring to guide the perioperative management and the surgery could also be considered in advanced 154

冠狀動脈繞道手術後發生四肢麻痺 cases. 6 Cervical spinal cord injury after CABG surgery is a rare and potentially devastating complication which deserves early intervention. Acute exacerbation of the preexisting CSM contributes to the major portion of such complications. Neurological prognosis is usually very poor in these victims despite aggressive management, especially in cases with complete spinal cord injury and/or superimposed with ischemic infarction due to severe peripheral vascular diseases, as encountered by this patient. Preoperative identification of the patient at risk, careful anesthetic and surgical planning, and implementing the effective preventive strategies during perioperative period are crucial while managing this kind of patients. References 1. Young WF. Cervical spondylotic myelopathy: a common cause of spinal cord dysfunction in older persons. American family physician 2000;62:1064-1073. 2. Thomas NJ, Harvey AT. Paraplegia after coronary bypass operations: relationship to severe hypertension and vascular disease. The Journal of thoracic and cardiovascular surgery 1999;117:834-836. 3. Spielmann PM, Campanella C. Spinal infarction following coronary artery bypass grafting. Interactive cardiovascular and thoracic surgery 2004;3:606-607. 4. Fujioka S, Niimi Y, Hirata K, et al. Tetraplegia after coronary artery bypass grafting. Anesthesia and analgesia 2003;97:979-980. 5. Naja Z, Zeidan A, Maaliki H, et al. Tetraplegia after coronary artery bypass grafting in a patient with undiagnosed cervical stenosis. Anesthesia and analgesia 2005;101:1883-1884. 6. Rao SL, Bundy JT, Stephenson E. Neurophysiologic monitoring during cardiopulmonary bypass in a patient with critical aortic stenosis and cervical spine stenosis. Journal of cardiothoracic and vascular anesthesia 2008;22:115-118. 7. Li CC, Yie JC, Lai CH, Hung MH. Quadriplegia after off-pump coronary artery bypass surgery: look before you place the neck in an extended position. Journal of cardiothoracic and vascular anesthesia 2013;27:e16-17. 8. Cheng MY, Lyu RK, Chang YJ, et al. Spinal cord infarction in Chinese patients. Clinical features, risk factors, imaging and prognosis. Cerebrovascular diseases 2008;26:502-508. 9. Suzuki K, Meguro K, Wada M, et al. Anterior spinal artery syndrome associated with severe stenosis of the vertebral artery. AJNR American journal of neuroradiology 1998;19:1353-1355. 10. Bernhardt M, Hynes RA, Blume HW, White AA, 3rd. Cervical spondylotic myelopathy. The Journal of bone and joint surgery American volume 1993;75:119-128. 155

劉韋呈等 病例報告 -- 於接受冠狀動脈繞道手術後發生急性遲發性四肢麻痺 劉韋呈 1, 褚錦承 2, 林耀聰 3, 邢中熹 2, 王立楷 2, 陳貞吟 2 3, 林明忠 摘要 患者於接受冠狀動脈繞道手術後發生術後四肢麻痺是一項非常少見的併發症, 大部分可以歸因於患者本身的頸椎退化性脊髓病變 (cervical spondylotic myelopathy) 於術中或術後因姿勢而加重 之前被報告的病例大部分在手術後患者從全身麻醉中甦醒就立即被發現而診斷出來 本文所報告的病例則是在接受冠狀動脈繞道手術後發生延遲性的突發性四肢麻痺 頸部核磁共振造影發現患者有頸椎退化性脊髓病變以及嚴重的右側椎動脈狹窄 因此頸椎退化性脊髓病變的急性加重與脊髓梗塞缺血被認為是造成此位患者四肢麻痺的主要原因 不論是否接受緊急手術減壓, 此類患者神經學預後通常非常差 接受心臟術前完整的病史詢問 理學檢查以及術中術後小心擺位會有助於預防此類併發症的發生 關鍵詞 : 冠狀動脈繞道, 脊椎退化, 脊髓病變, 脊髓梗塞, 四肢麻痺 通訊作者 : 林明忠醫師 3 73657 台南市柳營區太康里太康 201 號 ; 奇美醫療財團法人柳營奇美醫院麻醉科電話 :+886-6-2812811 轉 53321;E-mail:mygegon@gmail.com 1 奇美醫療財團法人佳里奇美醫院麻醉部 2 奇美醫療財團法人奇美醫院麻醉部 156