Suspect SCI or myelopathy:
• New onset of weakness (both legs or all four extremities)
• Sensory deficits
• Intact cerebral function
• Sphincter dysfunction (check rectal tone and catheterize the bladder).
Trauma:
• Neurosurgery consult
• Consider MP load 30 mg/kg followed by 5.4 mg/kg/hr for 23 hr
Epidural hematoma:
• Neurosurgery consult
• Immediately reverse anticoagulation with FFP and vitamin K
Epidural abscess:
• Neurosurgery consult
• Vancomycin and ceftriaxone
• Look for source (blood cultures, CT)
Tumor or metastases:
• Neurosurgery consult
• Dexamethasone 10 mg IV, followed by 4 mg IV q6h
• Look for primary source
Demyelinating lesions:
• Neurology consult
• MP 1 g IV daily for 5 days
Spinal cord infarct:
• Neurology consult
• Consider anticoagulation (if known embolic source)
• Keep mean arterial pressure > 70–80 mm Hg
Initial stabilization:
• Immobilize patient with cervical or thoracic cord lesions
• Address airway, breathing, and circulation
Obtain proper imaging:
• CT of spine if suspect bone abnormalities (fractures)
• MRI of spine if soft tissue or cord itself may be involved (hematoma, abscess, neoplasms)
SCI,spinal cord injury; CT, computed tomography; MRI, magnetic resonance imaging; MP, methylprednisolone;
FFP, fresh-frozen plasma; IV, intravenous.
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pressure of 70 to 80 mm Hg. Atropine should be kept at bedside; transcutaneous pacing may be needed in rare cases of symptomatic refractory bradycardia.
Airway and Breathing
Endotracheal intubation is recommended for those cord trauma victims who have associated traumatic brain injury with Glasgow Coma Scale score of<8 or signs of elevated intracranial pressure. Any airway compromise due to focal edema, fractures, and/or hemorrhages of the neck may also require intubation. Only physicians with advanced airway skills should attempt intubation with an unstable spine; fiber-optic intubation is often required, as the cervical spine often cannot be extended. Measures should be taken to avoid hypotension during intubation, and succinylcholine is con- traindicated in SCI of>24 hours. Neurosurgeons should be at bedside to help with immobilization of the spine if a cervical collar must be removed.
Close respiratory monitoring in a critical care setting is necessary, as SCI victims encounter multiple pulmonary complications (neurogenic pulmonary edema, pneu- monia, atelectasis, pleural effusions, pulmonary embolism) and are prone to respiratory failure even days after the initial injury. Patients with extensive operative courses and/or prone positioning may have massive fluid shifts in the first few postoperative days and can develop rapid pulmonary edema as fluid is mobilized. In a patient with limited neck mobility, this situation is potentially dangerous. With lesions above C3 level, diaphragmatic function is lost, often resulting in apnea and respiratory arrest; most patients need mechanical ventilation. With lesions between C3 and C5, diaphragmatic function is partially preserved; however, intercoastal muscles may be compromised, leading to diminished lung volumes, poor cough, and hypoventilation.
Thromboembolism Prevention
The majority of patients with SCI eventually develop deep venous thromboses (DVTs), with the highest risk in the first 3 months after the injury; however, there is no cur- rent indication for asymptomatic inferior vena cava (IVC) filter placement. Weekly surveillance Doppler studies are optional. Pneumatic compression devices and elastic stockings should be applied as soon as possible; adding pharmacologic means of pre- vention (low-molecular-weight heparin or adjusted dose unfractionated heparin) may be delayed until surgical plans are finalized and there is no risk of bleeding. Therapeutic anticoagulation should be withheld for 3 to 7 days after surgery, which may require the placement of an IVC filter in the case of DVT or pulmonary embolism.
Gastrointestinal Management
Acute gastroparesis may require gastric suctioning and administration of prokinetic agents to avoid aspiration. Ileus and constipation commonly complicate the course in patients with SCI; bowel regimen (e.g., scheduled laxatives, suppositories every other day) should be instituted early to prevent fecal impaction. H2-antagonists or proton pump inhibitors are given for stress ulcers and gastrointestinal bleeding prophylaxis.
Skin
As quadriparesis and paraparesis obviously limit motion, this patient population is prone to pressure ulcers. Frequent alteration of position to allow pressure relief and meticulous care of wounds is necessary. Low-air-loss suspension beds and automatically rotating beds may diminish the incidence of decubitus ulcers and facilitate healing of existing ulcers.
Neurologic Disorders rAcute Spinal Cord Disorders 4 6 9
Other Issues
Spasticity and contractures become a major problem for these patients within weeks after the injury. Early physical and occupational therapy should be initiated; baclofen, diazepam, and dantrolene are useful agents for spasticity. Pulmonary, urinary tract, and cutaneous infections are common. Universal precautions for ventilator-associated pneumonia should be instituted. Urinary retention is seen commonly and may require self-catheterization or in-dwelling catheters. Pain and depression are seen in most patients and should be addressed promptly. A pain management specialist is often helpful, and psychological support systems are essential.
N O N T R A U M A T I C M Y E L O P A T H Y
Most patients with nontraumatic SCI do not require an ICU admission, unless the upper cord is involved. It is important to identify those at risk for respiratory failure or hemodynamic instability and treat them with the same supportive care as earlier.
Furthermore, the nontraumatic causes of myelopathy may have other interventions such as resection of abscess, endovascular therapy for vascular malformations, and steroids or intravenous immunoglobulin for inflammatory disorders.
S U G G E S T E D R E A D I N G S
Early acute management in adults with spinal cord injury: a clinical practice guideline for health- care professionals.J Spinal Cord Med.2008;31:403–479.
Guidelines from the Consortium for Spinal Cord Medicine
Stevens RD, Bhardwaj A, Kirsch JR, et al. Critical care and perioperative management in traumatic spinal cord injury.J Neurosurg Anesthesiol.2003;15:215–229.
An excellent evidence-based review on multifaceted approach to patients with traumatic spinal cord injury.
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59 Neuromuscular Disorders in the Critically Ill
Rajat Dhar
The neuromuscular system encompasses the connections between the motor neurons in the spinal anterior horn and the effector muscles that allow us to move and breathe.
Disorders of this system usually lead to generalized weakness and may be best divided into those with onset prior to hospital admission and those developing in patients admitted to the hospital/intensive care unit (ICU) for another illness. They are also classified on the basis of neurologic localization (Table 59.1). Occasionally a disorder with onset prior to admission may not be recognized till a patient is admitted for another problem (e.g., aspiration pneumonia) or develop as a secondary feature of a multisystem disorder (e.g., vasculitis, porphyria).
N E U R O M U S C U L A R R E S P I R A T O R Y F A I L U R E
Respiratory muscles may be affected in almost any of the acute neuromuscular dis- orders, but most commonly in Guillain–Barr´e syndrome (GBS), myasthenia gravis (MG), and amyotrophic lateral sclerosis (ALS). In fact, some patients with ALS present with isolated or predominant respiratory involvement without much extremity weak- ness, which can make the diagnosis challenging. Weakness of the respiratory system (diaphragm as well as intercostal muscles of the chest wall) leads to impaired ventila- tion as well reduced cough and clearance of secretions. Accessory muscles, including the sternocleidomastoid and scalenes, may compensate in part, but hypercapnic res- piratory failure will result from progressive weakness. Hypoxemia may develop due to atelectasis and airway plugging from retained secretions. However, it is critical not to rely on arterial blood gas (ABG) evidence of hypercapnia or hypoxemia (or oxygen desaturation) as markers of imminent neuromuscular respiratory failure (NMRF), as these will occur late in the course as severe decompensation is imminent. There are a number of clinical markers that occur much earlier, and should be closely tracked in patients with acute quadriparesis with suggestion of respiratory involvement (Table 59.2). Observing the patients breathe (especially when lying flat), speak, lift their head, and cough can provide important information.
Ancillary testing involves bedside spirometry to measure negative inspiratory force (NIF) and forced vital capacity (FVC). NIF is the maximal inspiratory pressure generated after forceful exhalation, as measured with a mouthpiece attached to a pressure gauge; it is normally –50 to –70 cm H2O. Values below –30 suggest significant
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TABLE 59.1 Causes of Neuromuscular Respiratory Failure by Localization Localization of
disorder
Onset prior to ICU
admission ICU-acquired weakness
Muscle Inflammatory myopathies Acid maltase deficiency Mitochondrial myopathies Myotonic dystrophy Periodic paralysis
Critical illness myopathy Acute necrotizing myopathy Rhabdomyolysis (incl. drugs) Electrolytes (↓PO4,↓K) Neuromuscular
junction
Myasthenia gravis Lambert–Eaton syndrome Botulism, Tick paralysis Organophosphate toxicity
Prolonged neuromuscular blockade
Hypermagnesemia Peripheral nerve/
root
Guillain–Barr ´e syndrome Multifocal motor neuropathy Porphyria, Vasculitis, CMT Heavy metals and toxins HIV, Diphtheria, Lyme
disease Paraproteinemia,
Paraneoplastic
Critical illness polyneuropathy Phrenic nerve injury
Anterior horn cell Amyotrophic lateral sclerosis Poliomyelitis (West Nile
virus) Central (Spinal
cord/brain)
Acute myelopathy (ischemic, compressive, inflammatory)
Brainstem infarction
Spinal cord ischemia (e.g., postoperative), epidural abscess
Central pontine myelinolysis ICU, intensive care unit; CMT, Charcot–Marie Tooth (inherited neuropathy); HIV, human immunodeficiency virus.
weakness. FVC measures the amount of air exhaled and normally exceeds 3 to 4 L.
Values less than 30 mL/kg require close monitoring. A consistent downward trend or values less than 20 mL/kg may signal impending respiratory failure and warrant evaluation for preemptive intubation and ventilation. Spirometry can be performed at regular intervals (one to four times per day) in patients with progressive weakness, but not too frequently as to induce fatigue. Facial weakness may prevent the patient forming a tight seal around the mouthpiece, making results artifactually low; a facemask pressed tightly against the lips may overcome this limitation. The trend and overall clinical evaluation should guide decision making and not any isolated FVC or NIF values.
Intubation of patients with NMRF should be performed prior to acute decom- pensation and ideally before hypercapnia, significant atelectasis, or aspiration develop.
Neuromuscular blocking agents (NMBs) should be avoided if possible; succinylcholine can precipitate lethal hyperkalemia in patients with denervation and nondepolariz- ing NMBs can cause prolonged paralysis in MG. A trial of noninvasive ventilation
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TABLE 59.2 Signs of Impending Neuromuscular Respiratory Failure
Sign Red flag
Clinical
Progressive weakness Bulbar involvement Weak cough
Quadriplegia, inability to lift head off bed Dysphagia, weak voice, bifacial weakness Trouble expelling secretions, “wet” voice Respiratory complaints
Dyspnea Tachypnea Orthopnea
Accessory muscle use Abdominal paradox
Complains of respiratory fatigue
Unable to speak in full sentences, count to 20 Nocturnal desaturations, prefers to sit up Using neck & abdominal muscles Inward motion of abdomen with inspiration Signs of distress
Tachycardia Diaphoresis
Restless Staccato speech Monitoring
Vital capacity (VC) testing (bedside)
Arterial oxygen saturation Arterial blood gas: PaCO2 Chest radiographs
VC<15–20 mL/kg, falling, drop by 30%
Desaturation (late sign)
Hypercapnia=hypoventilation (late sign) Atelectasis, Pneumonia
(i.e., bilevel positive airway pressure [BiPAP]) may be considered in select patients with NMRF as long as mental status and airway reflexes are preserved. Some patients with neuromuscular failure may not have diaphragmatic weakness requiring ventilatory support but enough bulbar weakness to necessitate intubation for airway protection.
Such patients, of course, will not benefit from BiPAP and will also not require much ventilator support once intubated. The use of BiPAP in GBS may be unsuccessful par- tially for this reason (i.e., failure of airway protection) and also because these patients usually progress rapidly beyond the support that non-invasive positive pressure venti- lation (NIPPV) is able to easily provide. Overventilation (to fully normalize PCO2) should be avoided in those with chronic retention, otherwise alkalemia will develop, impairing subsequent weaning. Decisions about tracheostomy should be deferred in GBS and MG patients till after immunomodulatory treatment (with plasmapharesis or intravenous immunoglobulin [IVIG]) is completed, as rapid improvement can be seen. Decisions on tracheostomy and weaning can also be facilitated by daily measure- ments of FVC and NIF on the ventilator (FVC>7–10 mL/kg and NIF<–20 cm H2O). It is advisable to wait for 24 hours of spontaneous breathing (with an ABG to exclude CO2retention) in patients recovering from NMRF prior to extubation as delayed fatigue can occur.
G U I L L A I N – B A R R ´E S Y N D R O M E
GBS is an acute inflammatory demyelinating polyneuropathy that is the most common cause of flaccid paralysis worldwide. It is a monophasic autoimmune process often
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triggered by an upper respiratory or gastrointestinal infection. Clinical hallmarks include symmetric proximal and distal muscle weakness in the legs and arms asso- ciated with areflexia and frequent bulbar, facial, and respiratory muscle involvement.
Dysautonomiais seen in more than half of the patients with GBS and may manifest as wide fluctuations in blood pressure, tachycardia and/or bradycardia (sometimes lead- ing to cardiac arrest), and gastrointestinal symptoms including ileus. Cautious should be exercised in treating blood pressure due to potential lability and atropine may be kept at the bedside as suctioning may induce bradycardia. Sensory complaints and back pain are common in GBS, although patients with acute para- or quadriparesis and sensory dysfunction (especially a “sensory level”) should be evaluated for spinal cord compression or other causes of myelopathy. The diagnosis of GBS is supported by finding elevated protein levels in cerebrospinal fluid (CSF) without pleocytosis.
Nerve conduction studies (NCS) and electromyography (EMG) may be obtained to assist with diagnosis and prognosis, but may be relatively normal if performed early in the course. The incidence of NMRF requiring intubation is 30% and almost half of these patients require tracheostomy for prolonged ventilation. Treatment is with IVIG (total dose 2 g/kg over 2 to 5 days) or plasmapharesis, and although it may be delayed, recovery is the rule. ICU stay is most prolonged in those with complete quadriplegia and axonal changes (e.g., reduced motor amplitudes) on EMG/NCS.
M Y A S T H E N I A G R A V I S
MG is an autoimmune disease where antibodies are directed against the acetylcholine receptor (Ach-R) at the neuromuscular junction. This impairment of neuromuscu- lar synaptic transmission leads to fatigable weakness with predominant ocular (pto- sis, restriction of ocular movements with diplopia) and bulbar involvement. NMRF occurs with diaphragmatic involvement and is the hallmark ofmyasthenic crisis,which occurs in 20% of patients with MG. There is often an identifiable precipitant such as intercurrent infection, surgery (including thymectomy), or medications (commonly antibiotics, see Table 59.3). Worsening of MG is seen in a subset of patients shortly after initiating corticosteroid therapy (especially at doses more than 20 mg/day) and may pre- cipitate crisis. The diagnosis of MG is primarily clinical, confirmed either by presence of Ach-R antibodies in the serum or the finding of “decrement” (of motor amplitudes) on repetitive nerve stimulation. Treatment of MG consists of cholinesterase inhibitors (pyridostigmine) and immunosuppression (including corticosteroids). Crises are usu- ally treated with IVIG or plasmapharesis (as in GBS). Recovery is usually more rapid
TABLE 59.3 Medications that can Aggravate Weakness in Myasthenia Gravis
Antibiotics Aminoglycosides, ciprofloxacin, clindamycin, erythromycin, azithromycin, tetracyclines, polymixin B, colistin
Antiarrhythmics Quinidine, procainamide, lidocaine,β-blockers, calcium channel blockers
Hormones Corticosteroids Neuromuscular
blockers
Succinylcholine, vecuronium, pancuronium, etc.
Other Lithium, phenytoin, quinine, statins
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