Sir,
In emergent cases, awake intubation may be required. One of the methods used to perform awake endotracheal intubation is sedation with local anesthesia. For prevention of laryngospasm or bronchospasm succinylcholine can be used. This is a case report in which we used intratracheal succinylcholine injection to perform an emergent intubation in a critical patient.
A 75-year-old man was admitted for bacterial pneumonia by Pseudomonas aeruginosa. Upon presentation, the patient had 39°C fever, tachycardia, and tachypnea. On his second day of his hospitalization, he developed severe respiratory distress and lost consciousness; he required tracheal intubation. His vitals were: blood pressure 80/50 mmHg, heart rate 130 beats/min and respiratory rate 52 breaths/min. Coarse rhonchi were heard in both lungs. The patient was sedated with 100 μg of fentanyl intravenously and 100 mg of succinylcholine was injected intratracheal via crichothyroid cartilage. No respiratory pause and fasciculation were observed. During laryngoscopy, the patient did not show any reaction. The trachea was wide, and no vocal cord movement was observed. The tracheal tube was passed through his airway easily without resistance or bucking. Vital signs were stable during laryngoscopy and tracheal intubation. Electrolytes (particularly potassium) had no obvious change after tracheal intubation and the day after. After 3 days, the patient extubated himself due to restlessness. Due to further hemodynamic impairment, intravenous lidocaine was used alone for a repeat tracheal intubation. At laryngoscopy view no specific laryngotracheal injury such as edema, erythema, or lesion was observed. The larynx was active with little resistance and bucking during intubation.
Succinylcholine is used in emergency and full stomach patients for tracheal intubation. Succinylcholine is administrated intravenously commonly, but in emergent situations and pediatric laryngospasm, it can be given intramuscularly, interosseous, sublingual and subcutaneous injection can also be used.[1] The subcutaneous injection of succinylcholine has delayed onset compared with venous injection (15.6 ± 10.2 against 2.6 ± 1.7 min, respectively).
The muscarinic receptors type M1 dilate the bronchus, M3 receptor is postsynaptic and constricts bronchus, and the M2 receptor is presynaptic with negative feedback effects and also dilates the bronchus. A study by Zeng et al. showed subarachnoid succinylcholine with lidocaine on rat potentiated regional anesthesia.[2] The pathophysiology is not obvious, but Inman et al. reported muscarinic effects of succinylcholine as a probable mechanism.[3]
Inadvertent subarachnoid or subcutaneous injection of nondepolarizing muscle relaxants has been reported.[4] In a study by Iwasaki et al., peak effect of pancuronium was much faster in intravenous injection and recovery time was longer after subcutaneous injection.[5]
Due to the patient's respiratory distress while on ward, the patient was a candidate for awake tracheal intubation. With probability of laryngospasm and bronchospasm, succinylcholine was injected intratracheally via cricothyroid cartilage. No systemic complications such as apnea, fasciculation, airway reaction (e.g. gaging and bucking) were observed and also no hemodynamic derangement following intubations was created.
The muscarinic effects of succinylcholine may be associated with bronchodilation but further studies are needed. Intratracheal succinylcholine may cause obvious bronchodilation without any specific systemic and local complication and can use in urgent intubation or bronchospasm.
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