Influence of intra-osseous infusion of a small volume of hyperosmotic fluid on β-adrenergic function in circulating lymphocytes from bled pigs

Abstract

The regulation of β-adrenergic function in circulating mononuclear leukocytes was evaluated during an episode of haemorrhagic shock treated by intra-osseous infusion of a small volume of hyperosmotic fluid. Two groups of piglets (n = 14) were anaesthetized with ketamine and bled to a mean arterial pressure of 40 mmHg. After 45 min the animals were randomized to receive 100 ml of either hyperosmotic (2.4 mol l⁻¹) or iso-osmotic (0.29 mol 1⁻¹) fluid (equal volumes of glucose/sodium chloride) into the tibial bone marrow. Observations of haemodynamic variables and levels of plasma catecholamines and cAMP of circulating mononuclear leukocytes were carried out for 70 min. Infusion of hyperosmotic fluid enhanced the circulatory performance and attenuated the plasma catecholamine release significantly (p<0.05) compared to the corresponding values in the animals that had iso-osmotic fluid infusion. Measurements of unstimulated and isoprenaline-stimulated cAMP levels in mononuclear lymphocytes indicated that the high plasma catecholamine levels in the iso-osmotic treatment group induced a desensitization of the β-adrenoceptors 70 min after initiation of the shock. This effect was not seen in animals that had undergone hyperosmotic infusion.

Key Words:

• β-adrenoceptors
• cAMP
• catecholamines
• haemorrhagic
• mononuclear leukocytes
• resuscitation