Succinylcholine is structurally related to acetylcholine and produces muscle relaxation by first activating muscle fibres, then preventing a further response. As a result, muscle fasciculation is seen in many patients soon after succinylcholine administration. Succinylcholine has a short duration of action as it is metabolized in the plasma by pseudocholinesterase. There are several contraindications to the use of succinylcholine.
Remember that these conditions may also be triggered by using succinylcholine for the first time.
Denervation injury
The initial depolarization, caused by
succinylcholine, is reversed by a repolarization that involves potassium
moving down its concentration gradient into the extracellular
environment. This usually results in a 0.5 mM rise in the plasma
concentration of potassium, which is of little clinical significance.
However, where there are extrajunctional receptors, as is seen
after denervation injury, the efflux of potassium is much greater and may
cause a clinically significant rise in potassium concentration, resulting
in ventricular fibrillation followed by asystole.
Eye injury
Contraction of the extra-ocular muscles following the
use of succinylcholine result in a significant rise in intraocular
pressure so that the contents of the eyeball may be compromised where
there is an open eye injury.