Advanced Atrio-Ventricular Blocks in a Foal Undergoing Surgical Bladder Repair: First Step to Cardiac Arrest?

Abstract

A 3-day-old Swiss Warmblood colt was diagnosed with uroabdomen after urinary bladder rupture. The foal had classical electrolyte abnormalities (hyponatremia, hypochloremia and hyperkalemia) on presentation. The foal was supported prior to surgery with intravenous fluids and the electrolyte abnormalities were treated with physiologic saline, glucose and insulin. Urine could not be drained from the abdomen prior to surgery because the omentum was continuously occluding the drainage cannula and due to progressive abdominal distension, it was decided to pursue surgery without further correction of electrolyte abnormalities. After induction of anaesthesia, signs of hypoxemia were present. Controlled mandatory ventilation using a pressure-controlled ventilation mode with positive end-expiratory pressure was initiated. Urine was drained from the abdomen by free flow. Atrio-ventricular (AV) blocks unresponsive to intravenous antimuscarinic drugs developed. After low dose of epinephrine and cardiac massage, sinus rhythm was restored. Surgery was completed successfully and the foal recovered from anaesthesia. The postoperative period was uneventful and the foal was discharged from the hospital three days later. Based on a clinical case, the purpose of the manuscript is to provide the clinician with potential causes, prevention and treatment of this already known but rarely observed dysrhythmia which could lead to fatal consequences. Definitions of cardiac arrest and asystole are reappraised. We discuss the fact that advanced AV-blocks should be treated as a cardiovascular emergency with advanced life support. The early recognition of advanced AV blocks is the first step to reduce perioperative mortality and morbidity of foal suffering from uroabdomen.

Hypoxaemia and bradyarrhythmia in a foal undergoing surgical bladder repair

“…The heart rate fell significantly and atrial standstill was diagnosed on the ECG. Other bradyarrhythmias, including second degree atrioventricular block, have been reported during abdominal decompression and it has been suggested that the decrease in venous return associated with decompression may trigger a vasovagal reflex 5–21 . We speculate that the rapid abdominal decompression, could have been the trigger of the atrial standstill.…”

“…The lack of coordination between the anaesthetist and surgeon resulted in rapid decompression when the abdomen was opened. A sudden decrease of intraabdominal pressure when urine is drained too fast may induce vasovagal reflex for the mechanism reported above 21 . A slow and controlled drainage should have been attempted, ideally prior to anaesthesia.…”

“…Other bradyarrhythmias, including second degree atrioventricular block, have been reported during abdominal decompression and it has been suggested that the decrease in venous return associated with decompression may trigger a vasovagal reflex. [5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20][21] We speculate that the rapid abdominal decompression, could have been the trigger of the atrial standstill. This type of bradyarrhythmia can progress to cardiac arrest and the administration of an antimuscarinic to increase HR, should have been considered.…”

Mortality and morbidity in equine anaesthesia

“…Dysrhythmias associated with cardiac arrest included second-degree atrioventricular block unresponsive to atropine (Bidwell et al 2007;Marolf et al 2018), ventricular tachycardia in a horse in recovery (Bidwell et al 2007) and in a foal leading to ventricular fibrillation (Coudry et al 2007). Vasovagal reflex in association with manipulation of the eye or structures near the vagal trunk itself may cause bradycardia or cardiac arrest (Short and Rebhun 1980;Raffe et al 1986;Parviainen and Trim 2000;Taylor and Clarke 2007).…”

“…Dysrhythmias are reported to occur in 5.3% of cases (Parviainen and Trim 2000) but often are self-limiting and therefore seldomly reported. Occasional reports describe, mainly with halothane, ventricular dysrhythmias (Cornick et al 1990;Bright 1994), second-or third-degree atrioventricular block (Whitton and Trim 1985;Marolf et al 2018) and accelerated idioventricular rhythm during dobutamine blood pressure support (Karrasch et al 2013).…”