Heart rate variability during massive hemorrhage and progressive hemorrhagic shock in dogs

Abstract

Purpose: To investigate the sequential changes in heart rate (HR), autonomic nervous activity presented by the spectral analysis of heart rate variability (HRV), hemodynamics and metabolism during massive hemorrhage and progressive hemorrhagic shock in dogs.Methods: Twelve dogs were subjected to acute massive hemorrhage until mean arterial pressure (MAP) reached 50 mmHg. Then bleeding was stopped and they were allowed to reach a plateau phase. They were divided, post hoc, into bradycardic or tachycardic groups according to their HR response to the acute massive hemorrhage. After reaching a plateau phase, the dogs were further bled to keep their MAP around 50 mmHg (progressive hemorrhagic shock). Their heart rate power spectra were quantified into low-frequency (LF) (0.04-0.15 Hz) and high-frequency (HF) (0.15-0.4 Hz) components.Results: In the bradycardic group, both LF and HF increased after massive hemorrhage, but during progressive hemorrhagic shock these components decreased while HR increased. In the tachycardic group, LF increased after massive hemorrhage, but during progressive hemorrhagic shock LF decreased with continuous suppression of HF. Conclusion:Massive hemorrhage caused two types of HR response: bradycardia and tachycardia. The HRV profile showed differential autonomic characteristics, and could be a valuable tool in assessing various degrees of hemorrhagic shock.Objectif : Examiner les changements de fréquence cardiaque (FC), l'activité nerveuse autonome selon l'analyse spectrale de la variabilité de la fréquence cardiaque (VFC), l'hémodynamie et le métabolisme pendant une hémor-ragie massive et un choc hémorragique progressif, chez des chiens.Méthode : Douze chiens ont été soumis à une hémorragie aiguë massive jusqu'à ce que la tension artérielle moyenne (TAM) atteigne 50 mmHg. Puis, on a arrêté le saignement et laissé la pression parvenir à un plateau. On a, en conséquence, réparti les animaux en groupe bradycardie ou tachycardie selon le comportement de la FC pendant l'hémorragie aiguë massive. Un plateau une fois atteint, les chiens ont subi une autre hémorragie pour amener leur TAM autour de 50 mmHg (choc hémorragique progressif). Le spectre de la puissance de la fréquence cardiaque a été quantifié en composantes de basses fréquences (BF) (0,04-0,15 Hz) et de hautes fréquences (HF) (0,15-0,4 Hz).Résultats : Dans le groupe bradycardie, les BF et HF ont augmenté après l'hémorragie massive, mais lors du choc hémorragique progressif, ces composantes ont diminué pendant que la FC augmentait. Dans le groupe tachycardie, les BF ont augmenté après l'hémorragie massive, mais lors du choc, elles ont baissé en même temps que survenait la suppression continue des HF.Conclusion : L'hémorragie massive a causé deux types de réaction de la FC : la bradycardie et la tachycardie. Le profil de VFC a affiché des caractéristiques autonomes différentielles, ce qui en fait un outil valable pour éva-luer différents degrés de choc hémorragique.

Initial bradycardia in hypotensive (hemorrhagic) patients in a prehospital setting – does it have a prognostic value?

“…Thus the reflex is possibly an explanation for bradycardia in extraabdominal bleeding! Kawase et al (6) investigated heart rate variability during massive hemorrhaging and progressive hemorrhagic shock in dogs. They concluded that massive bleeding caused two types of heart rate response: bradycardia followed by tachycardia and tachycardia only.…”

“…Oberg and Thorg (23) argued that such results are the effects of the protective role of bradycardia, which reflexively increases ventricular diastolic filling. The increased parasympathetic activity in bradycardia may be associated with better tissue perfusion attributable to peripheral vasodilatation (1,6,14). Regardless of the mechanism (vagus nerves, pelvic parasympathetic nerves, nicotine sensitive mechanoreceptors located in the left ventricle, two types of response to hemorrhage with sympathetic-parasympathetic balance or other causes), the absence of tachycardia in hemorrhagic hypotensive patients is a real phenomenon .…”

“…Recent works support such a biphasic ("form M") pattern in response to hemorrhaging suggesting that the bradycardic response is reversible and not terminal, (2)(3)(4)(5)(6)(7)(8)(9)(10)(11)(12)(13). The inability of the heart to respond to the shock with tachycardia has been described as relative bradycardia (2,15), paradoxical bradycardia (11) or the absence of tachycardia (1,12).…”

“…The inability of the heart to respond to the shock with tachycardia has been described as relative bradycardia (2,15), paradoxical bradycardia (11) or the absence of tachycardia (1,12). Some clinical studies (15,16) and animal studies (6,23) have shown that the presence of relative bradycardia in hypotension (hemorrhaging) is associated with a better prognosis than the presence of tachycardia. The aim of this study was: to investigate whether preclinically registered bradycardia in hemorrhagic shock class II-IV is a real phenomenon and has a better prognosis than tachycardia, and if so, what are the possible explanations for it.…”

Effects of Naloxone on Stress-Induced Analgesia After Hemorrhagic Shock

“…Relative or paradoxical bradycardia is not rare in acute hypotensive situations. 7 Kawase et al 8 reported that massive hemorrhage caused 2 types of heart-rate response: bradycardia and tachycardia. They speculated that the phenomenon might be derived from differential activities of the autonomic nervous systems.…”