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2 BioMed Research International Table 1: Cardiac emergencies in supratentorial surgery. Author Patient ( ) (age/sex) Procedure Cardiac rhythm Cause Management Outcome Chowdhury and West [3] 50 y C Awake craniotomy (frontal tumor) Bradycardia, asystole (25 s) TCR (scalp traction) Release scalp traction; cessation propofol and remifentanil infusions No neurological deficit Prabhu et al. [4] 65 y D Awake craniotomy (temporal tumor) Bradycardia and asystole (8–10 s × 2 times) TCR (dura cautery) Cessation of cautery, atropine No neurological deficit Sinha et al. [5] 18 y D Epilepsy surgery Bradycardia (2 episodes), asystole (9 s) ↑ Parasympathetic response 2 ∘ to amygdala resection; warm and cold saline irrigation Atropine; cessation of stimulus No neurological deficit Sato et al. [6] 6/42 [ 18–34 y; C = 3, D = 2 ] Epilepsy surgery Sinus bradycardia ( < 1 min) ↑ Parasympathetic tone 2 ∘ to limbic stimulation Procedure interruption; atropine No neurological deficit Tyler et al. [7] 22 y C Craniotomy (parietal tumor) Asystole Intracranial hematoma (dural closure) Hematoma evacuation No neurological deficit Wasnick et al. [8] 70 D Epidural suction drain Severe bradycardia Intracranial hypotension Release of suction No neurological deficit Alfery et al. [9] 18 C VP shunt VT, VF Intracranial hypotension Lidocaine, CPR No neurological deficit Karamchandani et al. [10] 65 C Subgaleal suction drain Multiple severe bradycardia Intracranial hypotension Release of suction, atropine No neurological deficit Bhagat et al. [11] 2 patients [ both 60 D ] Subgaleal suction drain Severe bradycardia, Asystole Intracranial hypotension Release of suction, atropine No neurological deficit C = female gender; D = male gender; TCR = trigeminocardiac reflex; no neurological deficit = postoperative deficit not mentioned. performed by two independent investigators (TC and AP), using combinations of the terms “cardiac arrest,” “cardiac asystole,” “ventricular fibrillation,” “pulseless elec- tric activity,” “elective,” “intraoperative,” “cardiac resuscita- tion,” “neurosurgery,” and “defibrillation.” Searches were per- formed with no restriction on article type (original articles, reviews, retrospective studies, and case series/reports/letters) or article language. References were also checked for includ- ing potential papers related to the filed; however, duplicate results were deleted. 3. Causes and Mechanisms of Cardiac Emergencies Intraoperative minor cardiac adverse events including brady- cardia, hypotension, hypertension, and arrhythmias in neu- rosurgical patients are commonly reported and usually tran- sient in nature; however, more serious cardiac complications including ventricular fibrillation (VF), asystole, and pulseless electrical activity (PEA) do occur in some patients and may produce catastrophic consequences if not managed promptly [7]. One must be cognizant of the causes and related mechanisms that incite these severe hemodynamic perturbations, as a good understanding of these variables forms the basis of appropriate management strategies. In this paper, we have categorized cardiac emergencies by the type of neurosurgical procedure. 3.1. Supratentorial Surgery. Severe hemodynamic distur- bances are a frequently described phenomenon in patients undergoing elective supratentorial surgery. Most often, these disturbances occur as a result of various cranial nerve reflexes and were reported in both awake and anesthetized patients (Table 1). Among various causes, trigeminocardiac reflex (TCR) is the most common. TCR is a well-established brainstem reflex that can occur with stimulation of any sen- sory branch of trigeminal nerve and produces bradycardia, asystole, hypotension, apnoea, and gastric hypermotility. The afferent limb is formed by trigeminal nerve, whereas efferent fibers are carried by vagus nerve. Small internuncial nerve fibers of the reticular formation connect the afferent to the efferent premotor neurons located primarily in the nucleus ambiguus and the dorsal motor nucleus of the vagus. The reflex pathway activates cardioinhibitory parasympathetic vagal neurons, which terminate into the myocardium, which | The Surgical Technologist | FEBRUARY 2022 62