Fatal air embolism during sigmoidoscopy performed under spinal anesthesia.

Air embolism is an uncommon but potentially catastrophic event that occurs when air enters the vasculature. Because of a scared and friable colorectal mucosa, patients with anastomotic stricture are at an increased risk of complications associated with sigmoidoscopy such as bowel perforation and bleeding. This is a report of fatal air embolism confirmed on an immediate postmortem chest radiograph in a patient with a high colorectal anastomotic stricture undergoing sigmoidoscopy under spinal anesthesia is reported. The literature on air embolism in patients undergoing sigmoidoscopy/colonoscopy is reviewed.

INTRODUCTION

Although generally considered quite safe, sigmoidoscopy does carry the very rare possibility of tearing of the intestinal wall by the instrument, which may require immediate major surgery to repair the tear. The incidence of this complication is probably increased when sigmoidoscopy is performed in a narrowed/strictured lumen. This report describes the possibility of death due to apparent air embolism from accidental entry of insufflated air into the circulation through the severed blood vessel of the injured bowel lumen.

CASE REPORT

A 30-year-old male is known to have bronchial asthma, on Salbutamol as needed, contact dermatitis on both hands and gout. Patient underwent a low anterior resection with diverting loop ileostomy for a midrectal adenocarcinoma 4 months back and received three cycles of adjuvant chemotherapy. Complaining of bleeding per rectum was presented to the clinic. Clinical examination revealed a very tight anastomotic stricture. A trial of balloon dilatation using the flexible sigmoidscope failed even with the usage of the guide wire. Biopsy revealed ulceration with granulation tissue, but no malignancy was seen. Patient was admitted for dilatation under anesthesia. Under spinal anesthesia, strictured anastomosis was rigid and fibrotic; aggressive finger and instrumental dilatation (Higar dilators) was performed. There was a minor bleeding postdilatation. Flexible sigmoidoscopy was performed intraoperatively at the end of the procedure. Ninety min after dilatation, patient complained of sudden onset shortness of breath followed by tachyarrhythmia with oxygen desaturation reaching 78% that was followed by bradycardia. Patient was immediately intubated. In a second, tachyarrhythmia change to Bradycardia, then systole yellowish discoloration, bluish discoloration. CPR was initiated.

The patient was intubated ventilated with 100% oxygenation, atropine-given adrenaline colloid started cardiac pulmonary resuscitation initiated immediately, external cardiac massage with chest compression 100/min, location of endotracheal tube was confirmed immediately by chest auscultation there was equal air entry in both sides, 1 mg epinephrine every 5 min but not responding to CPR.

During CPR, authors searched and treat possible reversible causes of cardiac arrest-like Hypovolemia, acidosis, tension pneumothoraxsocolloid was given, chest X-rays requested ABG-showed acidosis corrected by sodium bicarbonate, no hypokalemia or hyperkalaemic, not responding to external pace maker and after aggressive resuscitation for 45 min and the patient declared dead after 45 min.

Differential diagnosis was pulmonary embolism, tumor embolism, air embolism sever intra-abdominal bleeding.

On site CXR was immediately taken after announcement of death and showed a large lucent area projecting over cardiac shadow. Most of the cardiac silhouette has been replaced by lucent shadow that is peripherally outlined by the cardiac muscle indicating the presence of significant pneumocardium.

There was no air dissecting around the major vascular structure in the neck and thymus gland is not separated from the cardiac shadow thar ruled out pneumomediastenum [Figure 1].

Figure 1

Postmortem on table (intra-operative) Chest x-ray showing a large lucent area projecting over cardiac shadow. Most of the cardiac silhouette has been replaced by the lucent shadow that is outline peripherally by the cardiac muscle

DISCUSSION

The risk of AE is well recognized in procedures in which the operative site is above the level the heart, classically with neurosurgical cases performed in the sitting position[1] or otolaryngologic surgeries[2] but could happen in various clinical settings such as laparoscopic surgery,[34] pelvic procedures,[5] endoscopic saphenous vein harvesting,[6] and orthopedic procedures.[7] AE during sigmoidoscopy or colonoscopy is a rarely reported complication.[8] A MEDLINE search of English language publications from 1966 through December 2003 identified only 17 cases. Air embolism has occurred in patients of all ages and during all types of endoscopic procedures, including EGD, colonoscopy, flexible sigmoidoscopy, EUS, and ERCP.[2]

The common underlying mechanism of venous air/gas entrainment involves subatmospheric pressure at the site of air entry and/or pressurized air or gas being forced into the venous circulation.[8] The effects of an air embolus depend on the volume and the rate at which the air is introduced. Minor air embolism occurs often but produces minimal symptoms or is clinically silent. In the canine model, the capacity of the lung to filter microbubbles from the venous circulation is exceeded at a rate greater than 0.30 mL/kg/min, after which arterial emboli may occur.[9] The exact amount of air necessary to cause significant hemodynamic disturbances or death has not been clearly defined, yet a bolus of 100 to 300 mL of air can be lethal in an adult human.[10]

In the authors’ opinion, the aggressive dilatation of the anastomotic stenosed site caused injury to the newly formed friable vessels. The pressure of insufflations produced the necessary pressure gradient allowing fast and forceful entry of the insufflated air into the severed venules and capillaries.

In this case report, we aimed to raise clinical suspicion and awareness of the possibility of AE occurrence in patient who developed sudden onset shortness of breath during endoscopic procedure. The amount of air that could be insufflated before reaching the significant pressure gradient causing AE is a subject for further studies and we recommend to keep in mind air embolism as one of causes of cardiac arrest in the previously mentioned surgical procedure and one of reversible cause of cardiac arrest such as hypoxia Hypovolemia hypothermia, tension pneumothoraxpulmonary embolism acidosis hypokalemia and hyperkalaemic and start definitive treatment with keeping patient on the left lateral position with passing catheter to right ventricle and aspirate the air.