CURRENT Essentials of Critical Care.pdf

106 Current Essentials of Critical Care■■■Respiratory Failure from Neuromuscular DisordersEssentials of Diagnosis• Weakness of respiratory muscles or dysfunction of ventilatorycontrol from neuromuscular or neurological disease• PaCO 2 50 mm Hg, usually with additional hypoxemia• If weakness, vital capacity (VC) 1500 mL associated with hypercapnia• Disorders of ventilatory control due to sedative or opioid overdose,head trauma, brain stem stroke, hypothyroidism, poliomyelitis• Respiratory muscle weakness due to spinal cord disease (trauma,cancer, paraspinous abscess, amyotrophic lateral sclerosis); neuropathicdisease (myasthenia gravis, botulism, Guillain-Barrésyndrome, tick paralysis, drugs, peripheral neuropathy); primarymuscle disease (polymyositis, endocrinopathies, hypophosphatemia,hypokalemia); ICU patients (critical illness polyneuropathyor polymyopathy); extremity strength may not reflectstrength of respiratory musclesDifferential Diagnosis• Primary lung disease with acquired neuromuscular weakness(critical illness polyneuropathy)• Chest wall deformity or abnormalityTreatment• Treat underlying disease• Oxygen for hypoxemia due to atelectasis or pneumonia• Consider endotracheal intubation and mechanical ventilationwhen VC15 mL/kg or 1200 mL in adults, especially if worsening• Patients with weakness have disproportionate atelectasis, inabilityto clear secretions and pneumonia, pulmonary thromboembolicdisease■ PearlSuspect acquired neuromuscular weakness due to critical illnesspolyneuropathy or myopathy in a patient who fails to wean from mechanicalventilation.ReferenceRabinstein AA et al: Warning signs of imminent respiratory failure in neurologicalpatients. Semin Neurol 2003;23:97. [PMID: 12870111]