Experimental physiology
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Experimental physiology · Nov 2002
The effects of primary thoracic blast injury and morphine on the response to haemorrhage in the anaesthetised rat.
Primary thoracic blast injury causes a triad of bradycardia, hypotension and apnoea mediated in part via a vagal reflex. Blast casualties may also suffer blood loss, and the response to progressive simple haemorrhage is biphasic: an initial tachycardia followed by a vagally mediated reflex bradycardia which can be attenuated by micro opioid agonists. The aims of this study were to determine the effects of thoracic blast injury on the response to subsequent haemorrhage, and the effects of morphine, administered after blast, on the response to blood loss. ⋯ Mean arterial blood pressure (MBP) began to fall as soon as haemorrhage commenced and was significant after the loss of 10 % BV. Morphine (Group III) prevented the haemorrhage-induced bradycardia and delayed the significant fall in MBP until the loss of 30 % BV. It is concluded that the response to thoracic blast injury augments the depressor response to haemorrhage while morphine attenuates this response.