General Articles: Case Report
Laryngeal mask airway (LMA) is being increasingly used for maintenance of airway. Blind insertion techniques and the ability to provide similar airway control as with an endotracheal tube make it a popular choice. However, blind insertion of an airway carries the potential risk of causing airway obstruction by foreign bodies not being detected.
A 29-yr-old man with midpenile hypospadias was scheduled to undergo elective urethroplasty with suprapubic cystostomy under regional anesthesia. He had no significant medical history and physical examination was normal. Airway examination revealed a normal unobstructed airway with normal head extension, mouth opening, sublaxation of mandible, mentohyoid, and thyromental distance. All screening laboratory investigations were essentially normal. Diazepam 10 mg was given the night before and 60 min before surgery. In the operating room, baseline variables—noninvasive blood pressure, oxygen saturation (Spo2), and electrocardiogram—were recorded. After administration of lactated Ringer’s solution 1000 mL, the subarachnoid space was identified in the left lateral position with a 25-gauge Quincke tip spinal needle. Once free flow of cerebrospinal fluid was obtained, 2.9 mL of 0.5% heavy bupivacaine was injected after gentle aspiration. The patient was placed in the supine position to evaluate the level of the sensory block. Despite waiting for 10 min, the height of the sensory block remained at L2 dermatome. Because the height of the block was inadequate for surgery, general anesthesia was induced. After administration of IV meperidine (25 mg), anesthesia was induced with 250 mg of thiopental. Succinylcholine (80 mg) was administered to facilitate LMA insertion. Bag and mask ventilation was initiated with 100% oxygen through Bain’s circuit yielding a normal end-tidal carbon dioxide (Etco2) trace. There was no difficulty in ventilation and the lung compliance was normal. Once the fasciculations from succinylcholine subsided, LMA (size 4) insertion was accomplished without difficulty using the standard Brain’s technique. Auscultation of bilateral equal air entry, presence of a normal capnograph, and absence of gastric insufflation confirmed the position of the LMA. Halothane (1%) in 66% nitrous oxide and 33% oxygen was commenced to maintain anesthesia. After initial successful manual ventilations, subsequent ventilation of the lungs became increasingly difficult after 3 min. An attempt was made to reposition the LMA but without success, and a progressive decrease in Spo2 to 40% was accompanied by a gradual disappearance of capnograph trace and a transient decrease in heart rate to 40 bpm. The LMA was immediately removed after cuff deflation. Bag and mask ventilation was initiated with 100% oxygen. Satisfactory chest expansion was achieved and improvement in the Spo2 was evident. The capnograph trace was recordable with an Etco2 tension of 60 mm Hg. Ventilation showed remarkable improvement in the subsequent 3 min. On inspection of the removed LMA, an adult Ascaris was seen coiled up in the vertical bars of the LMA (Fig. 1). Once the Spo2 stabilized on 100%, oxygen concentration was reduced gradually to 33% and 1% halothane in 66% nitrous oxide was resumed. Tracheal intubation was accomplished by repeating suxamethonium (75 mg). Thereafter, the entire intraoperative course was satisfactory and the postoperative recovery uneventful.
Ascaris lumbricoides is one of the largest and most common parasites found in humans and it is estimated that 25% of the world’s population is infected with this nematode (1). Common causes of upper airway obstruction are foreign bodies or inflammation. Upper airway obstruction with a nematode has been reported after tracheal extubation and the presence of a worm at the glottis was detected after direct laryngoscopy (2). However, with increasing use of LMA during general anesthesia, the likelihood of such an obstruction going unnoticed for a while is more likely. Airway obstruction is a life-threatening emergency and identification of the cause can be extremely distressing for the anesthesiologist during adverse conditions.
Adult Ascaris lumbricoides worms may migrate up to the esophagus and enter the air passages, especially when they are irritated by certain drugs or anesthetics (2). Migration is likely to be assisted by relaxation of the lower esophageal sphincter caused by anesthetic induction giving an opening to the worm to escape from rising intragastric pressure after succinylcholine administration. Because bag and mask ventilation was possible in our patient and obstruction was noticed after LMA insertion, it is likely that the migrated worm was scooped up by the LMA. Extraintestinal larval forms of the nematode exist but it is generally the adult worm that has been implicated with significant signs and symptoms of respiratory obstruction.
In another patient, the worm was aspirated during the course of bag and mask ventilation before endotracheal intubation. Intraoperatively, the patient had high peak airway pressures (28 cm H2O), low normal Spo2 (91%), and bilateral rhonchi not responding to conventional bronchodilators. After completion of the surgery, tracheal extubation was uneventful but the patient had persistent cough postoperatively for 2 days after he coughed out the worm. All symptoms subsided subsequently.
Acute laryngeal obstruction or obstruction of the airway device as a result of Ascaris worm, despite its rarity, should be considered, especially in patients returning from or living in areas of endemic parasitic infestation.
1. Ortega R. An unusual cause of nasogastric tube obstruction. Anesth Analg 1992;75:147.
2. Faraj JH. Upper airway obstruction by Ascaris
worm. Can J Anaesth 1993;40:471.