The Trigeminocardiac Reflex — An Example of Reflexive Heart Rhythm Change

The trigeminocardiac reflex (TCR) is defined as the sudden onset of parasympathetic dysrhythmia, sympathetic hypotension, apnoea or gastric hyper-motility during mechanical/thermal stimulation of any of the sensory branches of the trigeminal nerve. The risk factors that are already known for increasing the prevalence of the TCR include anatomical location, hypercapnia, hypoxemia, light general anaesthesia, age (more pronounced in children), the nature of the provoking stimulus (stimulus strength and duration) and different drugs. Already different potential confounders are also identified. This discussion about risk factors has its importance because of the substantial consequences for functional outcome after intraoperative TCR occurrence. But there remains still a substantial lack of thorough understanding of the TCR, the current treatment options for patients with TCR include a mostly empirical approach: (i) risk factor identification and modification; (ii) prophylactic measures of vital signs and (iii) administration of vagolytic agents or sympathomimetics. In this context, we have now created different thinking models so that we can preoperatively plan a skull base surgery procedure safely in relation to a potential occurrence of the TCR episodes. This chapter provides an overview of this unique reflex that presents a unique interaction between heart and brain. In addition, this also illustrates the mechanism of various cardiac rhythm changes related to the TCR

Cardiac Emergencies in Neurosurgical Patients

Perioperative safety concerns are a major area of interest in recent years. Severe cardiac perturbation such as cardiac arrest is one of the most dreaded complications in the intraoperative period; however, little is known about the management of these events in the patients undergoing elective neurosurgery. This special group needs further attention, as it is often neither feasible nor appropriate to apply conventional advanced cardiac life support algorithms in patients undergoing neurosurgery. Factors such as neurosurgical procedure and positioning can also have a significant effect on the occurrence of cardiac arrest. Therefore, the aim of this paper is to describe the various causes and management of cardiac emergencies with special reference to cardiac arrest during elective neurosurgical procedures, including discussion of position-related factors and resuscitative considerations in these situations. This will help to formulate possible guidelines for management of such events

Coronary Spasm in Neurosurgical Patients and Role of Trigeminocardiac Reflex

Background. Coronary artery spasm (CAS) is a rarely reported complication in neurosurgical patients and its main causative mechanism was attributed to vagal mediated responses. However, these may be the unusual manifestations of trigeminal cardiac reflex (TCR) which is a well established brain stem reflex observed in various neurosurgical patients. Methods and Results. In this review, we have searched for the case reports/papers related to intraoperative coronary spasm in neurosurgical patients and described the role of TCR in this regard. TCR is a possible mechanism in producing CAS in most of the cases in which stimulation occurred at or near the vicinity of trigeminal nerve. It is likely that TCR mediated coronary spasm may be a physiological mechanism and not related to actual myocardial insult apparent by cardiac enzymes or echocardiography studies in most of the cases. Some common risk factors may also exist related to occurrence of CAS as well as TCR. Conclusions. In conclusion, neurosurgical procedures occurring at the vicinity of trigeminal nerve may produce CAS even in previously healthy patients and may produce catastrophic consequences. There is a need for future reports and experimental studies on the interaction of TCR and pathophysiological mechanisms related to CAS

Definition and Diagnosis of the Trigeminocardiac Reflex: A Grounded Theory Approach for an Update

BackgroundThe trigeminocardiac reflex (TCR) is defined as sudden onset of parasympathetic dysrhythmias including hemodynamic irregularities, apnea, and gastric hypermotility during stimulation of sensory branches of the trigeminal nerve. Since the first description of the TCR in 1999, there is an ongoing discussion about a more emergent clinical definition. In this work, the author worked out an approach to such an improved definition.MethodsIn this study, a grounded theory approach was used. Literature about TCR was systematically identified through PubMed (MEDLINE), EMBASE (Ovid SP), and ISI Web of Sciences databases from 1/2005 until 8/2015. TCR was defined as a drop of heart rate (HR) below 60 bpm or 20% to the baseline. A grounded theory approach was used to analyze and interpret the data through a synthesis by the researcher’s perspectives, values, and positions.ResultsOut of the included studies, the authors formed available data to an update of the understanding of changes in hemodynamic parameters (HR and blood pressure) in a TCR. According to this update, an HR deceleration should be a constant observation to identify a TCR episode while a drop in blood pressure should probably not being fixed to a certain percentage of decrease.ConclusionThe here presented working definition improves our understanding of the TCR. It leads the way to a new understanding of the TCR for a proper clinical definition