Electrocardiographic changes associated with the nasopharyngeal reflex in conscious rabbits: vago-sympathetic co-activation

doi:10.1016/S1566-0702(03)00048-1

Autonomic Neuroscience

Volume 105, Issue 2, 30 May 2003, Pages 101-104

https://doi.org/10.1016/S1566-0702(03)00048-1 Get rights and content

Abstract

Electrocardiographic responses were assessed in conscious rabbits when the nasopharyngeal reflex was elicited by inhalation of formaldehyde vapour. There was a profound fall in heart rate (224±5 to 64±4 beats per min (bpm)) associated with abnormal or absent P-waves. There were no changes in the QRS complex. The R–T interval (control value 118±4 ms) was initially shortened to 107±3 ms and then prolonged to 130±4 ms. Heart rate and P-wave changes were prevented by muscarinic cholinergic blockade with methylscopolamine. The R–T shortening was reduced by 79±4% by β-adrenergic blockade with propranolol. Methylscopolamine also unmasked small tachycardic responses (5–25 bpm) in 5/7 animals. This tachycardia was prevented by propranolol. Thus both parasympathetic vagal cardiac nerves and sympathetic cardiac nerves are activated during the nasopharyngeal reflex, with increased vagal effects in the sino-atrial node, and increased sympathetic effects in the ventricular myocardium.

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Acknowledgments

This study was supported by grant #PD02A0853 from the National Heart Foundation of Australia and by grant #187616 from the National Health and Medical Research Council of Australia. We are grateful to Ms. Melissa Blair for excellent technical assistance.

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Cited by (38)

The Influence of Trigeminocardiac Reflex on Postoperative Cardiac Adverse Events in Patients Undergoing Cerebellopontine Angle Tumor Resections: A Case-Control Study
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To assess the potential impact of the trigeminocardiac reflex (TCR) on postoperative adverse cardiac events and to identify predictors of the TCR in cerebellopontine angle surgery.
Patients undergoing elective cerebellopontine angle surgery from October 1, 2015, to September 30, 2020, were recruited consecutively for this retrospective case-control study. The TCR was evaluated by reviewing electronic anesthesia records and defined as a drop in heart rate was >20%. Controls were identified from the same retrospective cohort and matched by age, sex, and similar (±5 days) surgery date in the ratio of 1:2.
Of 2446 patients, 68 (2.78%) experienced TCR episodes. A total of 97 TCR episodes occurred among the 68 patients. In 2 TCR episodes, severe cardiac complications developed after surgery—myocardial injury in one case and cardiac arrest in the other case. The prevalence of adverse cardiovascular events was higher in the TCR group (60.3% vs. 36.0%, P = 0.001) than in the control group. The independent risk factor for the TCR in the multivariate condition logistic regression was tumor compression of the brainstem (odds ratio = 2.36, 95% confidence interval 1.40–3.95; P = 0.001).
Intraoperative TCR episodes seemed to be associated with postoperative adverse cardiac events in patients undergoing cerebellopontine angle surgery. Moreover, tumor compression of the brainstem might be a risk factor for TCR episodes.
The Trigeminal Nerve: Anatomical Pathways. Trigeminocardiac Reflex Trigger Points
2015, Trigeminocardiac Reflex
The trigeminocardiac reflex (TCR) is gaining increasing importance and interest in various fields of surgery, including skull base, neurovascular, ophthalmological, maxillofacial, and dental procedures. It has been shown that this reflex not only represents an important intraoperative phenomenon, but also may have influence on the postoperative functional outcome (preservation of hearing and elimination or reduction of tinnitus in some of the patients operated on for vestibular schwannoma). The recent past has seen substantial advances in the understanding of the anatomical pathways related to different subtypes (i.e., central versus peripheral) of the TCR. In addition, in-depth knowledge of particular patterns of the trigeminal nerve innervations has an important role in elucidating the occurrence of the TCR and in defining particular trigger points as well. In this chapter, we summarize the current anatomical knowledge of this unique reflex, with special emphasis on the definition of TCR trigger points.
History of the Trigeminocardiac Reflex: An Odyssey
2015, Trigeminocardiac Reflex
Rome ne s’est pas faite en un jour,¹ and neither was our current understanding of the trigeminocardiac reflex. This understanding is based on a series of meticulous observations and experiments over the past two centuries, but predominantly in the last two decades. The journey extends from the initial explanation of the respiration reflexes in the mid-nineteenth century to the clinical and physiological definitions of the phenomenon in the twenty-first century. The history of the trigeminocardiac reflex sheds light on the importance of this phenomenon for everyone involved in the treatment of patients by means of neurosurgery, craniomaxillofacial surgery, facial plastic surgery, and ophthalmology. This chapter presents an in-depth treatment of the history of the trigeminocardiac reflex.
The Trigeminocardiac Reflex in Interventional Neuroradiology
2015, Trigeminocardiac Reflex
In contrast to the well-developed neurosurgical and ophthalmological literature, the literature on manifestations of the trigeminocardiac reflex (TCR) during neurointerventions has been reported in a total of only 16 cases. All of the cases involved the use of Onyx® as the embolic agent, with its solvent, dimethyl sulfoxide (DMSO), the likely responsible ingredient. These reports involved the embolization of arteriovenous fistulae or nasal tumors, with injection of the internal maxillary artery, the middle meningeal artery, the inferior petrosal sinus, or the cavernous sinus. Although there has been no clear demonstration that DMSO can act as a trigeminal excitatory agonist, clinical experience, as well as the chemical similarity of DMSO to organic vaporous solvents which are known to act that way, suggests that this is the likely mechanism.
All cases of the TCR discussed in the neurointerventional literature responded immediately to atropine, with no permanent sequelae. It is recommended that both neurointerventionalists and anesthesiologists performing the aforementioned procedures be prepared for the possibility of episodes of the TCR.
The Trigeminal Nerve and the Heart
2015, Trigeminocardiac Reflex
Stimulation of the trigeminal nerve initiates complex autonomic responses that profoundly alter cardiovascular function. Protective stimuli, such as the diving reflex and the nasopharyngeal reflex, trigger a sympathetic–parasympathetic coactivation that induces bradycardia, hypertension, and apnea. Conversely, adaptive stimuli, such as are observed in neurosurgical procedures, trigger the trigeminocardiac reflex, in which the reciprocal activation of both divisions of the autonomic system induces bradycardia, hypotension, apnea, and gastric hypermotility. Trigeminal reflexes tend to be powerful airway protectors and, by their cardiorespiratory modifications, adopt the characteristics of true oxygen-conserving reflexes. However, the association of trigeminal reflexes with several cardiac complications has been demonstrated. An increase in parasympathetic outflow and changes in sympathetic outflow may disturb the autonomic–cardiac balance and induce arrhythmias and, sometimes, severe coronary complications.
Comparison of the effects of atropine and labetalol on trigeminocardiac reflex-induced hemodynamic alterations during percutaneous microballoon compression of the trigeminal ganglion
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Citation Excerpt :
It is also plausible to hypothesize that coactivation of the autonomic systems provides a simply observed but difficult to explain hemodynamic effect in terms of trigeminal stimulation and related treatment. This hypothesis can be at least supported by a famous animal study in which TCR-induced coactivation of both the sympathetic and parasympathetic outflow was observed in a decerebrate rabbit model.25 Methods that prevent the trigeminal depressor response have had mixed results.
A significant abrupt drop in heart rate is the most frequent complication during percutaneous microballoon compression of the trigeminal ganglion. It is suggested that co-activation of the sympathetic and parasympathetic nervous systems plays an important role in this occurrence. We hypothesized that not only atropine, but also labetalol might be effective in preventing this cardiovascular reflex during percutaneous microballoon compression of the trigeminal ganglion.
Patients who underwent percutaneous microballoon compression for trigeminal neuralgia between September 2007 and December 2009 were prospectively evaluated. The relationship between the hemodynamic changes and intraoperative use of atropine (0.01 mg/kg) or labetalol (0.05 mg/kg) was compared. One-way analysis of variance with Bartlett's and Tukey's post-tests was used, and a value of p < 0.05 was considered statistically significant.
In total, 119 patients who received percutaneous microballoon compression for trigeminal neuralgia were studied, of whom 38 received atropine before ganglion compression, 36 received labetalol, and 45 received normal saline as a control. Of the patients who received normal saline, 31.3% had moderate bradycardia (heart rate < 50 beats/min), 13.3% had severe bradycardia (heart rate < 40 beats/min), and 7% had arrhythmia. Of the patients who received atropine, 7.8% had moderate bradycardia, 7.8% had arrhythmia, and 5.3% had postcompression tachycardia by the end of ganglion compression. Of the patients who received labetalol, 16.7% had moderate bradycardia, 5.6% had severe bradycardia, and 2.8% had arrhythmia. Systemic blood pressure was markedly elevated straight after compression in all groups and tended to normalize 3 minutes afterwards.
Both atropine and labetalol were able to lower the frequency of bradycardia. Neither of them could abolish episodes of bradycardia during the procedure. Patients receiving labetalol before microballoon compression were subject to a smaller change in hemodynamics. Our findings verified that the sympathetic and parasympathetic nervous systems may be involved in the complex interneuronal interaction of the trigeminocardiac reflex.

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Electrocardiographic changes associated with the nasopharyngeal reflex in conscious rabbits: vago-sympathetic co-activation

Abstract

Section snippets

Acknowledgments

J. Neurosci. Methods

J. Auton. Nerv. Syst.

Br. J. Anaesth.

J. Auton. Nerv. Syst.

Physiological adaptations in diving vertebrates

Physiol. Rev.

The effect of alertering mean pressure, pulse pressure, and pulse frequency on the impulse activity in baroreceptor fibres from the aortic arch and the right subclavian artery in the rabbit

J. Physiol.