The trigeminocardiac reflex: Does the activation pathway of its efferent arc affect the intensity of the hemodynamic drop during the management of maxillofacial fractures?

The study aimed to correlate between the stimulated nerve, intensity of trigeminovagal reflex (TVR), and neuropathophysiological pathway by which the efferent arc is activated. Material and methods: A retrospective study included patients who developed TVR during the surgical management of mandibular, midface, and orbital fractures. The reflex was divided into type I, II, III, and IV-TVR according to the following nerves: ophthalmic, maxillary, mandibular, and non-trigeminal nerves, respectively. The magnitude of hemodynamic drops was identified at the intraoperative baseline, during reflex, and postoperatively. The needed time to elicit the reflex, frequency and duration, need for medical intervention, and sequence of the drop were also recorded. P - values < 0.05 was considered significant. Out of 260 patients' files were reviewed, the TVR was observed in only 30 (11.55 %) patients. The ophthalmic nerve activation significantly caused the greatest intensity and magnitude of hemodynamic drop, followed by maxillary nerve, then mandibular division, and the lowest one was non-trigeminal nerves. The highest mean of drops in the mean arterial blood pressure (MABP) was 62.92 ± 2.39 with the type ITVR, whereas those of the type II, III, and IV were 75.5 ±3.98, 81.02±1.31, and 82.22±1.85, respectively. Also, the type I-TVR led to the greatest decrease in the heart rate (HR) with the mean equaled to 52.31± 3.91. The drop percentage in the MABP was -30.5, -17.5, -12, -10.08 for type I, II, III, and IV, whereas those of the HR were - 33.9, -27.13, -26.6, and -25 with type I, II, III, and IV, respectively. All results showed highly significant differences with p-values less than 0.001 when comparing between the baseline and intraoperative values of each TVR type. There is a positive correlation between the activated pathway of the TVR and the intensity of its efferent arc response due to the neural pathway of each division in the brainstem circuitry. Understanding of the pathophysiology and mechanism of the TVR, together with the rapid recognition and treatment could prevent serious negative outcomes, especially when the ophthalmic nerve is stimulated. 1Introduction.