• Join over 1.2 million students every month
  • Accelerate your learning by 29%
  • Unlimited access from just £6.99 per month

Neuromuscular Blocking Agents - NMBAs

Extracts from this document...

Introduction

Neuromuscular Blocking Agents - NMBAs Although most of the currently available anaesthetic agents will provide a degree of muscle relaxation, in general, most of them provide good muscle relaxation only when administrated at high concentration. These high concentrations are associated with severe cardiopulmonary depression, making theses agents unsuitable by themselves for situations where profound muscle relaxation is required during a surgical procedure. Two groups of two groups of drugs are available to increase the degree of muscular relaxation during surgery: * Centrally acting muscle relaxants: provide muscle relaxation by direct effects within the CNS, e.g. Benzodiazepines: diazepam and midazolam - can not produce as profound degree of relaxation associated with NMBAs * Neuromuscular blocking agents: acts are the neuromuscular junction (NMJ) NMBAs: Provide total abolition of muscle tone, allowing complete relaxation of all skeletal muscle groups - including the intercostal muscles (muscles between ribs) and the diaphragm. As these respiratory muscles are blocked, ventilation also stops. Therefore means of support must be available, e.g. a cuffed endotracheal tude and a suitable breathing system. Although muscle relaxants will ultimately cause paralysis of all the skeletal muscles, some groups are more resistant than others; the diaphragm is generally the last muscle to go and is the first to recover function. ...read more.

Middle

has a rapid onset time (seconds) and is short-acting (3-5 minutes in cat, 20min in dog). It is used to facilitate intubation in humans. o There are no reversal agents available for depolarising relaxants; duration depends mainly on the dose amount and concentration of circulating pseudocholinesterase. * Non-depolarising (competitive) muscle relaxants: o Compete with ACh for postjunctional binding sites and cause blockage of the motor endpate without the initial stimulation seen with depolarising agents. o Theses agents are much more used as they are reversible and "topped-up" as required. o Only administered IV o Many types of non-depolarising agents have been used in veterinary practice a lot are not used anymore: * D-Tubocurarine: seldom used these days because injection causes histamine release in dogs, resulting in vasodilation, hypotension, tachycardia and bronchial spasm. * Gallamine: unpopular because of tachycardia and hypotension after injection. * Alcuronium: long acting relaxant, only occasionally used now * Pancuronium: has a intermediate onset and long duration of action (more than 30 min), causes modest tachycardia after injection, but remains a useful agent * Vecuronium: a popular drug, derived from pancuronium, has an intermediate duration of action (20-30 min). ...read more.

Conclusion

NMBAs are good when do not have the time to wait, administered IV after the animal has first been masked down. * To reduce the amount of GA agent required: deceased muscle tone lead to decreased CNS stimulation and less anaesthetic is then required. * To assist ophthalmic procedures: commonly administered to animals undergoing cataract surgery to paralyse extra-ocular muscles and allow central positioning of the eye. * Oesophageal foreign body removal: Oesophageal foreign body removal is dogs. A relaxed oesophageal musculature allows retrieval of relatively large objects without the need for thoracotomy. * Laparotomies: Reduces the amount of traction required to produce exposure, causing less tissue trauma on the wound margins with less post-op inflammation and pain. Peripheral nerve stimulation: It is hard to determine the degree of neuromuscular blockage present in a patient, most commonly a nerve stimulator is used to help quantify the intensity of relaxation. The most common form of stimulation is train-of-four (TOF) where four electrical pulses are applied to the nerve over a 2-second period. In the non-paralysed animal, four distinct muscle twitches, each of identical strength, will occur. If a non-depolarising relaxant is then administered, the fourth twitch in the TOF will become weaker and eventually disappear, followed by the third twitch and the second and eventually the first, if sufficient relaxant is given. ...read more.

The above preview is unformatted text

This student written piece of work is one of many that can be found in our AS and A Level Anatomy & Physiology section.

Found what you're looking for?

  • Start learning 29% faster today
  • 150,000+ documents available
  • Just £6.99 a month

Not the one? Search for your essay title...
  • Join over 1.2 million students every month
  • Accelerate your learning by 29%
  • Unlimited access from just £6.99 per month

See related essaysSee related essays

Related AS and A Level Anatomy & Physiology essays

  1. Physiology Within Sport

    As this carbon dioxide increases this has the effect of reducing the PH level of the blood, and on the Dissociation Curve graph the curve shifts to the right, this produces a higher release of oxygen to the tissues, this is evident when looking at the graph below: Within the

  2. Free essay

    Body In Action

    Other examples include racquet players who have been shown to have greater bone density in their playing arms. It has even been shown that if a leg is immobilised by being placed in plaster, due to a fracture, that even after a few weeks the bone becomes decalcified from lack of mechanical stress.

  1. Skeletal System and Joints

    is actually made up of three separate bones: * the upper half (the broad "wings") is the ileum * the middle (the top half of the lower "loops") is the pubis * the bottom (the lower half of the "loops")

  2. The Structure of Skeletal Muscle.

    FT fibres, type IIAs has both good anaerobic and aerobic qualities. They have high ATPase activity like fast-glycolytic (IIB) fibres, but also a high oxidative capacity like type I fibres. Because of this, they can maintain a contraction longer than type IIBs, but contract faster (therefor developing more power)

  1. A level Project, Personal Exercise Program on Netball.

    Whether a fibre is slow or fast twitch depends on how rapidly it oxidises ATP." The Glycolytic system is also known as anaerobic glycolysis, which literally means the breakdown of glucose in the absence of oxygen. This system is more complex than the ATP-PC system and so takes longer to use ATP for energy.

  2. Movement within the Body and the Cardiovascular System

    the downward movement of a leg extension, in a quadriceps exercise. Task Two; The Cardiovascular System The Heart Chambers Right Atrium This is one of the four chambers of the heart, is found in the right side above the right ventricle.

  1. The effects of Rheumatoid Arthritis on joints.

    Rheumatoid nodules may also appear just below the elbow and sometimes on the hands and feet. These are fleshy lumps, which can easily be identified by biopsy under a microscope. Inflammation of the joints leads to a general feeling of being unwell and a fatigued state which is probably the most difficult to come to terms with.

  2. Body In Action

    Blood consists of white and red blood cells suspended in liquid called plasma. The red cells, the erythrocytes, contain haemoglobin. Other cells in the blood are leucocytes, white blood cells that fight against infection, and platelets, which are important in the process of blood clotting.

  • Over 160,000 pieces
    of student written work
  • Annotated by
    experienced teachers
  • Ideas and feedback to
    improve your own work