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Youmans:神經學重症治療-5(完)

WCH | 2021-09-17 18:43:33 | 巴幣 128 | 人氣 132



脊髓受損的重症考量

  • Acute spinal cord injury (SCI) is often associated with systemic hemodynamic and pulmonary derangements, and inadequate perfusion or oxygenation of the spinal cord has the potential to worsen neurological injury.
急性脊髓受損往往跟系統性的血液動力學與肺部障礙相關。不適當的血液灌流或供氧會導致神經損傷更加惡化。

血液動力學

  • Hypotension after acute SCI is common. SCI often occurs in the setting of other significant injuries, and the first consideration is to confirm or rule out systemic injuries that result in blood loss, such as lacerations, vascular injuries, injuries to the abdominal contents, and long bone or pelvic fractures, as the cause of the hypotension. Isolated SCI can also result in hypotension, inasmuch as the sympathetic signals from the spinal cord that increase the heart rate and the resistance in the systemic arterioles exit in the thoracic segments T1 to T4. With lesions above this level, bradycardia and hypotension can result. The administration of intravenous fluid is the first step to correct this, but because of lack of resistance in the vascular system, blood may pool within the vascular system, and pharmacologic methods become necessary to maintain hemodynamic support. Phenylephrine, whose almost exclusively α-adrenergic activity increases the tone in the vascular system, is an option, but its administration may result in reflex bradycardia because of the lack of β-adrenergic input. Norepinephrine, which has both α- and β-adrenergic activity, is often a preferable agent in this setting.
急性脊髓受損後往往可見低血壓,脊髓受損通常在很重大的受傷後發生,所以第一個要考量的問題就是會導致失血的受傷,例如撕裂傷、血管受傷、腹部內容物受傷、長骨或骨盆骨折。同時失血會導致低血壓。脊髓受損本身也可能造成低血壓,這是因為交感神經訊號無法從腦透過脊髓往下傳,導致心跳無法加快。同時也會造成交感性小動脈在第一到第四胸椎就失去血管阻力。因此如果受傷處是在第一到第四胸椎,就會導致心跳變慢以及血壓下降(註:血壓的原理一部分本來就是跟血管的回彈能力與阻力有關)。

要校正低血壓首先要給靜脈輸液,但由於失去血管阻力,輸液可能直接就在原處堆積起來。因此這時候就要考慮用藥物治療,來維持血液動力學。Phenylephrine這個幾乎只有α-腎上腺活性的藥物可以增加血管彈性。但這個藥也可能會造成反彈性心跳慢因為缺乏β-腎上腺活性的調控。而Norepinephrine因為同時有α和β,因此通常是很完美的治療方式。
  • The target for blood pressure needs to be individualized. The first consideration is to ensure that perfusion is sufficient to normalize systemic markers of tissue perfusion, such as urine output, serum lactate level, and arterial pH. Placement of a central venous catheter to help assess intravascular volume and provide access for vasoactive medications can aid in the process of resuscitation. There are, however, no measurable indices of the adequacy of spinal cord perfusion and no practical way to determine perfusion pressure of the spinal cord. Arbitrary systemic MAP goals have therefore been postulated as surrogate markers of adequate spinal cord blood flow. In uncontrolled small case series of patients with acute SCI who have been managed with MAP targets between 85 and 90mm Hg, improved neurological outcome has been claimed. The American Association of Neurological Surgeons/Congress of Neurological Surgeons (AANS/CNS) guidelines for the management acute SCI considers this level III evidence and recommends that MAP be kept between 85 and 90mm Hg for the first 7 days after the injury. The dose of vasoactive medication needed to produce this level of pressure in some patients may produce arrhythmias or excessive vasoconstriction, especially in patients with preexisting medical comorbid conditions, and the risks and benefits of this strategy must be weighed on an individual basis. If this regimen is selected, the patient must be monitored carefully in an intensive care unit.
至於要把血壓拉到多少有很多說法,但第一個要考慮的應該是確保血液灌流足夠維持組織灌流的正常。例如維持小便量、血漿乳酸量以及動脈酸鹼值(註:灌流差細胞會缺氧,轉而無氧呼吸生成更多乳酸和二氧化碳)。中央靜脈導管的安裝可以讓我們獲取血管內血流量資訊以及給予活化血管的藥物(註:有些活化血管藥物例如Norepinephrine因為有毒性所以會要求用中央靜脈導管從大血管給予)。但對於脊髓的灌流要維持多少則沒有一個定論。因此不同研究對於脊髓灌流的指標:平均動脈壓就有不同的說法。在一個沒有控制組的小型案例分析,認為平均動脈壓要維持85-90mmHg,可以維持好的神經臨床後果。美國神經外科協會/神經外科記者會的指引則認為在受傷後的七天內要將均動脈壓要維持85-90mmHg,這是一個透過控制組但沒有隨機試驗的結果。

給予活化血管藥物對於一些病患可能造成心律不整或是過度血管收縮,尤其是對於那些有很多共病的病患。所以要對不同病患進行風險評估。一旦給予了病患就要在加護病房接受嚴密的監控。

肺部相關問題

  • The pulmonary consequences of SCI are reflected by the level of the spinal injury. The diaphragm is innervated by the roots of C3 to C5 roots, and so complete lesions above C3 usually result in the need for urgent intubation and mechanical ventilation. In lesions below C5, diaphragmatic function is preserved, but in the acute phase there is flaccid paralysis of the intercostal and abdominal muscles. In this setting, the chest wall collapses with diaphragmatic contraction, markedly reducing the efficiency of respiration. This results in shallow respirations that are compensated by an increase in respiratory rate, and the loss of the abdominal muscles decreases the ability to cough and clear secretions. This promotes a cycle of increasingly rapid shallow breaths, progressive atelectasis, and subsequent fatigue. During the acute phase of SCI, respiratory function must be carefully monitored, and vigorous suctioning and promotion of pulmonary toilet are crucial. Signs of progressive fatigue, such as a persistently rising respiratory rate or an increase in partial pressure of carbon dioxide, should prompt intubation. Respiratory failure occurs in about one third of patients with cervical SCI at an average of 5 days after injury.
肺部問題會因為脊髓受損的位置而不同。支配的橫膈膜神經根位於第三到第五頸椎神經。因此如果完全受損於第三頸椎神經會急需插管和呼吸器。如果傷到第五頸神經以下則不會影響到橫膈膜,但還是可能會造成肋間和腹部肌肉的癱瘓造成呼吸能力受影響。當橫膈膜收縮會導致肺塌陷,造成呼吸變弱。這時候病患就會透過快速呼吸來代償。同時喪失腹部肌力也會造成咳嗽和清喉嚨的能力變差。所以可以看到病患有淺快呼吸、肺塌陷惡化以及變得疲勞。

在急性的脊髓受損,呼吸能力一定要很小心的監控。同時抽痰和呼吸道清潔也很重要。如果有病患變得更疲勞的症狀,例如持續呼吸變快或是血中二氧化碳濃度上升,就需要考慮插管。呼吸衰竭往往發生在1/3的五天內急性脊髓受損的病患。
  • The mean length of time for mechanical ventilation for patients with acute cervical SCI is about 5 weeks. This is largely because the ability to wean from mechanical ventilation is dependent on the transition from flaccid to spastic paralysis of the intercostal muscles. As this occurs, the chest wall regains much of its rigidity, and inspiratory function approaches preinjury levels. This means that most patients with injury below C3 are eventually able to be weaned from mechanical ventilation, but tracheostomy may need to be considered for many of these patients. Expiratory function and ability to cough, however, remain markedly diminished, and affected patients will continue to need aggressive pulmonary toilet.
急性脊髓損傷使用呼吸器的時間大概是五周,這麼久很大原因是脫離呼吸器需要等到肋間肌肉恢復才能。要等到肋間肌肉回復許多以及吸入功能達到受傷前的樣子才能考慮脫離呼吸器。對於那些受傷在第三頸椎神經的病患比較容易脫離呼吸器,但氣切還要考慮於多數的這些患者。同時吐氣功能和咳嗽能力也會持續下降很多,造成病患要持續靠輔助清潔呼吸道。

藥物治療

  • Pharmacologic agents aimed at limiting secondary injury after SCI, such as methylprednisolone and GM1 ganglioside, have been studied in human trials. Unfortunately, the results of these trials have been disappointing. In the case of GM1 ganglioside, an initial pilot study had promising results, but a subsequent larger multicenter, randomized, controlled study showed no benefit at 1 year in comparison with placebo. Methylprednisolone, evaluated in the Second National Acute Spinal Cord Injury Study (NASCIS II), purportly did show a benefit. However, there have been concerns about the design and conclusions of this study, and the AANS/CNS graded the results as level III evidence. The use of methylprednisolone does appear to be associated with increased risk of serious complications with level I evidence. The guidelines thus recommend that neither methylprednisolone nor GM1 ganglioside be used in the treatment of acute SCI.
藥物治療是為了減少脊髓受損後的二級傷害,這類藥物例如methylprednisolone以及GM1 ganglioside已經在人體試驗中進行研究。不幸的是這些研究結果都讓人失望。在GM1 ganglioside的試驗中,起始研究有很好的結果,但之後的大型多中心、隨機以及有控制組的研究都發現治療後1年跟安慰劑沒太大差別。Methylprednisolone在NASCIS II 聲稱有所幫助,但對於他們的研究設計與結論還是讓人質疑的,同時在美國神經外科協會/神經外科記者會的指引也認為這是一個透過控制組但沒有隨機試驗的結果。使用Methylprednisolone可能會造成更嚴重的併發症。而這個指引也建議在急性脊髓受損這兩種藥都不要用。

低溫治療

  • The use of hypothermia to limit secondary neurological injury has significant potential and has been shown to be beneficial in improved cerebral function after cardiac arrest. The value of hypothermia in acute SCI is unclear. The use of modest hypothermia (32°C to 34°C) in acute SCI has been reported to yield acceptable complication rates and improved neurological outcomes. The AANS/CNS Joint Section on Disorders of the Spine and Peripheral Nerves classified these findings as level IV evidence and stated that the evidence is insufficient to recommend or discourage this treatment.
使用低溫治療來減少二次神經損害被認為很有潛能,同時也被發現對心跳停止後大腦功能改善有助益。但對於低溫治療用在急性脊髓受損的好壞還未知。有研究顯示在急性脊髓受損使用中度低溫(32-34度)對神經臨床後果是有幫助的,同時併發症也是可以接受的。美國神經外科協會/神經外科記者會把這個當成良好設計的案例分析或世代研究。認為低溫治療的研究缺乏推薦或反對的證據。

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