Showing posts from July, 2022

Adverse effects of suxamethonium

    Muscle pains  Especially in patient who is ambulant soon after surgery, such as the day-case patient.  Caused by the initial fasciculations, are more common in young, healthy patients with a large muscle mass.  Occur in unusual sites, such as the diaphragm and between the scapulae, and are not relieved easily by conventional analgesics.  The incidence and severity may be reduced by the use of a small dose of a non- depolarising NMBA given immediately before administration of suxamethonium (e.g. atracurium 0.05 mg/kg). However, this technique, termed precurarisation or pretreatment, reduces the potency of suxamethonium, necessitating the administration of a larger dose to produce the same effect.  Increased intraocular pressure   Caused by the initial contraction of the external ocular muscles and internal ocular muscles after administration of suxamethonium.  It is not reduced by precurarisation.  The effect lasts for as long as the neuromuscular block Concern has been

Basic physiology of Neuromuscular junction

  Macro-anatomy of neuron ⍺ Motor neuron is surrounded by myelin sheath which is formed by the Swann cell.  Speed of conduction in ⍺ neuron is faster (50 - 100 m/s) due to myelin insulation and node of Ranvier. In the node of Ranvier, there is a high concentration of voltage-gated sodium channel causing depolarisation and saltatory movement to the next node.   The neuromuscular junction commences at the nonmyelinated nerve ending.  Extraocular, laryngeal and some facial muscles are innervated by slow conducting Ɣ neuron with multiple innervations.  Motor endplate  The axon terminal surrounded by Schwann cell cytoplasm contains mitochondria and vesicles.  The synaptic vesicles are synthesised in the anterior horn cell of the spinal cord and transported to the motor nerve terminal via the micro-tubular system.  The synaptic gap is 50 nm wide and contains a basement lamina of 20 nm consisting of mucopolysaccharides.  Ach receptors are arranged in discrete groups on the sho