Venous air/oxygen embolism due to H2O2 in anal fistulectomy
Hydrogen peroxide, an oxidizing agent, is frequently used in the cleansing of wound due to its germicidal properties. It is also used by surgeons in anal fistulectomy to locate the internal opening of the fistula in addition to its action in bubbling out foreign materials and debris.

Published in the Journal of Anaesthesiology Clinical Pharmacology, the authors present a case of air/oxygen embolism due to hydrogen peroxide in anal fistulectomy that was managed successfully.

A 39-year-old male ASA 1 was scheduled to undergo anal fistulectomy. Saddle block anesthesia was provided using 1.2 ml of 0.5% hyperbaric bupivacaine. After 15 minutes of saddle block, the patient was put in the lithotomy position. Per rectal examination was done by the surgeons. The external opening was at six o' clock position and the internal opening could not be felt. The external fistula opening was probed with a lubricated blunt malleable fistula probe that could be pushed up to 2 cm in intersphincteric plane.

He remained hemodynamically stable. The probe was removed and a 6 FG feeding tube was inserted through the external opening into the tract and 10 ml of 1.5% hydrogen peroxide was pushed with the aim to locate the internal opening. The internal opening could not be located and hydrogen peroxide did not return from the external opening as well.

At this time, suddenly the patient developed respiratory distress with the respiratory rate at 40/min and started coughing. He started complaining of chest pain which was crushing in character. Heart rate increased from 80/min to 140/min and blood pressure fell to 90/60 mm Hg. EtCO2 decreased from 35 to 20 mm Hg and oxygen saturation fell to 85%. Chest auscultation revealed bilateral bronchospasm. The operative procedure was deferred and the patient was put in the Trendelenburg position with 100% oxygen.

Sublingual sorbitrate was given and hydrocortisone 100 mg and deriphyllin were administered intravenously. In view of non-return of hydrogen peroxide from the fistula tract, the possibility of air/oxygen embolism was considered. Within 15 minutes, urgent transthoracic echocardiography using a portable ultrasound machine was done which revealed air in the right atrium confirming the diagnosis of embolism.

PA pressure was 56 mm Hg and the right atrium and the right ventricle were dilated. The patient was treated symptomatically. A repeat echocardiography after half an hour showed no air in the right atrium. The patient was kept under observation for 24 hours and then discharged from the hospital.

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