Absence of reflex vascular responses from the intrapulmonary circulation in anaesthetised dogs

McMahon, Nicholas C.; Drinkhill, Mark J.; Myers, David S.; Hainsworth, R.

doi:10.1017/s0958067000019461

Cited by 2 publications

(1 citation statement)

References 15 publications

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“…Furthermore, abrupt unloading of these receptors causes only transient falls in systemic pressure (McMahon et al 2000a). Stimulation of intra-pulmonary baroreceptors produces only small, transient cardiovascular changes (McMahon et al 2000b) but also causes attenuation of respiration (McMahon, et al 2000b). …”

Section: Discussionmentioning

confidence: 99%

Reflex Nature of the Cardiorespiratory Response to Primary Thoracic Blast Injury in the Anaesthetised Rat

Ohnishi¹,

Kirkman²,

Guy

et al. 2001

Experimental Physiology

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Blast injuries represent a problem for civilian and military populations. Primary thoracic blast injury causes a triad of bradycardia, hypotension and apnoea. The objective of this study was to investigate the reflex nature of this response and its modulation by vagotomy or administration of atropine. The study was conducted on terminally anaesthetised (alphadolone/alphaxalone, 18‐24 mg kg h−1, I.V.) male Wistar rats randomly allocated to the groups indicated below. Blast injuries were produced with compressed air while sham blast involved the sound of a blast only. Primary blast injury to the thorax resulted in a bradycardia (measured as an increase in the interval between beats, or heart period (HP) to 489 ± 37 ms from 133 ± 3 ms with a latency of onset of 4.3 ± 0.3 s, mean ± S.E.M.), hypotension (fall in mean arterial blood pressure (MBP) from 128.1 ± 3.7 mmHg to 34.8 ± 4.1 mmHg, latency of onset 2.0 ± 0.1 s) and apnoea lasting 28.3 ± 2.3 s. Sham blast had no effect. The bradycardia and apnoea following thoracic blast were abolished by cervical vagotomy while the hypotension was attenuated. Atropine (0.3 mg kg−1, I.V.) caused a significant reduction in the bradycardia (HP increasing from 124 ± 3 ms to 142 ± 4 ms) but did not modulate either the hypotension or apnoea. It is concluded that a reflex involving the vagus nerve mediates the bradycardia, apnoea and a component of the hypotension associated with thoracic blast. The pattern of this response is similar to effects that follow stimulation of the pulmonary afferent C‐fibres.

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Section: Discussionmentioning

confidence: 99%