Cardiorespiratory Effects of Epinephrine When Used in Regional Anesthesia

The Cardiorespiratory Effects of Thoracic Epidural Anaesthesia

“…epidural anaesthesia with epinephrine) firm conclusions cannot be reached about effects from the present series. However, the increase in cardiac output did appear to relate to the amount of epinephrine administered and is in agreement with the findings reported by Bonica (8a,55,56,87).…”

“…Studies performed by Bonica and his colleagues (8,55,56,87) suggested that the procedure resulted in a faii of cardiac output (CO) by 5.4% and in mean blood pressure by 8.9%. These studies were on volunteers, using 2% plain lidocaine and the sensory level was only defined as to at least T5.…”

The Use of Epinephrine in Caudal Anesthesia Increases Stroke Volume and Cardiac Output in Children

“…25 Low concentrations of epinephrine predominantly stimulate beta-adrenergic receptors, which are sensitive to much lower concentrations of epinephrine than alpha adrenergic receptors in the arterial vessels. 26 With predominant beta-adrenergic receptor stimulation, increases in CO are offset by decreases in TPR resulting in either no change or a small decrease in MAP. 25 Prior studies have demonstrated the relationship between epidural injection of epinephrine and its systemic effects.…”

Effects of epinephrine in local anesthetics on the central and peripheral nervous systems: Neurotoxicity and neural blood flow

“…These alterations are the consequence of ␤-adrenergic effects on peripheral capacitance vessels with a resulting decrease in peripheral vascular resistance. 4,11,[46][47][48] As long as MAP does not decrease below 50 mm Hg, SCBF autoregulation is preserved. Because the hemodynamic effects of absorbed epidural epinephrine appear to be primarily ␤-adrenergic, there is no reason to expect ␣ 1 -adrenergic receptor-induced spinal vascular vasoconstriction would occur, especially in humans in whom CNS arterial ␣ 1 receptors do not exist in the vertebral, and possibly other, arteries.…”

“…Yet animal studies warn that this may not be the case when circulation is compromised or the structural integrity of the nerve is altered. Because there is a ceiling effect for prolonging block duration and also for side effects, such as tachycardia, 48 it appears reasonable to use lower doses of adjuvant epinephrine in peripheral nerve blocks. For instance, at 1:400,000 concentration (2.5 g/mL), epinephrine prolonged block slightly less than a 1:200,000 concentration 48 and actually caused a transient increase in PNBF, suggesting that ␣ 1 -ad-renergic effects on PNBF are absent at this low dose.…”