Effects Of Anaesthesia On Regional Coronary Control Mechanisms

Cottee, David; Quail, Anthony W.; Porges, W. L.; Moore, P. G.; White, Saxon William

doi:10.1046/j.1440-1681.2000.03372.x

Cited by 2 publications

(1 citation statement)

References 22 publications

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“…A second is preservation of resting and reflex neurohumoral transmission against the physiological confounding effects of anesthetic agents; e.g., barbiturates block autonomic activity, both centrally (29) and peripherally (13,17), whereas chloralose (6) and fentanyl (26) enhance sympathetic and parasympathetic autonomic activity, respectively. Moreover, halothane and related halogenated ethers uncouple smooth muscle endothelial electrotonic transmission in vascular beds to an unknown extent in anesthetized experimental animals (2,3,12). Thus in the absence of these modifying factors, at rest, the smooth muscle of both airway wall and its vascular supply is tonically constricted by cholinoceptor activity, in agreement with previous studies in awake animals (15,23).…”

Section: Discussionsupporting

confidence: 89%

Differential effects of inhaled methacholine on circumferential wall and vascular smooth muscle of third-generation airways in awake sheep

McLeod

Parsons

Gunther

et al. 2012

Journal of Applied Physiology

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Evolution and natural selection ensure that specific mechanisms exist for selective airway absorption of inhaled atmospheric molecules. Indeed, nebulized cholinoceptor agonists used in asthma-challenge tests may or may not enter the systemic circulation. We examined the hypothesis that inhaled cholinoceptor agonists have selective access. Six sheep were instrumented under general anesthesia (propofol 5 mg/kg iv, 2-3% isoflurane-oxygen), each with pulsed-Doppler blood flow transducers mounted on the single bronchial artery and sonomicrometer probes mounted on the intrapulmonary third-generation lingula lobe bronchus. Continuous measurements were made of bronchial blood flow (Q(br)), Q(br) conductance (C(br)), bronchial hemicircumference (CIRC(br)), and bronchial wall thickness (WALL TH(br)) in recovered, standing, awake sheep. Methacholine (MCh; 0.125-2.0 μg/kg iv), at the highest dose, caused a 233% rise in Q(br) (P < 0.05) and a 286% rise in C(br) (P < 0.05). CIRC(br) fell to 90% (P < 0.05); WALL TH(br) did not change. In contrast, nebulized MCh (1-32 mg/ml), inhaled through a mask at the highest dose, caused a rise in ventilation and a rise in Q(br) proportional to aortic pressure without change in C(br). CIRC(br) fell to 91% (P < 0.01), and WALL TH(br) did not change. Thus inhaled MCh has access to cholinoceptors of bronchial circumferential smooth muscle to cause airway lumen narrowing but effectively not to those of the systemic bronchovascular circulation. It is speculated that the mechanism is selective neuroparacrine inhibition of muscarinic acetylcholine receptors (M3 bronchovascular cholinoceptors) by prostanoids released by intense MCh activation of epithelial and mucosal cells lining the airway.

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