Neuromuscular Junction Blocking Agents PDF

NEUROMUSCULAR JUNCTION BLOCKING AGENTS Florisa Borilla, RN, MD  Learning Objectives 1. Draw and label a neuromuscular junction. 2. Describe the therapeutic actions, indications, pharmacokinetics, contraindications, most common adverse reactions, and important drug–drug interact...

NEUROMUSCULAR JUNCTION BLOCKING AGENTS Florisa Borilla, RN, MD  Learning Objectives 1. Draw and label a neuromuscular junction. 2. Describe the therapeutic actions, indications, pharmacokinetics, contraindications, most common adverse reactions, and important drug–drug interactions associated with the depolarizing and nondepolarizing neuromuscular junction blockers. 3. Discuss the use of neuromuscular junction blockers across the lifespan.  Learning Objectives 4. Compare and contrast the prototype drugs pancuronium and succinylcholine with other neuromuscular junction blockers. 5. Outline the nursing considerations, including important teaching points, for patients receiving a neuromuscular junction blocker. NEUROMUSCULAR JUNCTION the point at which a motor neuron communicates with a skeletal muscle fiber à muscular contraction SARCOMERE - functional unit of muscle - made up of light and dark filaments formed by actin and myosin molecules  Nerve impulse or action potential ￬ Opening of voltage-gated calcium channels ￬ Influx of calcium ions inside the cell increases ￬ Opening/rupture of vesicle and release of acetylcholine ￬ Acetylcholine comes to the synaptic cleft ￬ Acetylcholine binds with nicotinic receptors to form the acetylcholine-receptor complex ￬ Opening of ligand-gated sodium channels ￬ Influx of sodium ions inside the cell increases ￬ Development of endplate potential ￬ Generate muscle action potential ￬ Muscle contraction takes place SLIDING FILAMENT MECHANISM OF SKELETAL MUSCLE CONTRACTION NONDEPOLARIZING NMJS - Atracurium - Cisatracurium - Pancuronium - Rocuronium - Vecoronium DEPOLARIZING NMJS - Succinylcholine  NONDEPOLARIZING NMJ ACTIONS - similar in structure to Ach and compete with Ach for the muscle Ach receptor site - occupy the muscular cholinergic receptor site à no stimulation INDICATIONS - Serve as an adjunct to general anesthetics during surgery when reflex muscle movement could interfere with the surgical procedure or the delivery of gas anesthesia  NONDEPOLARIZING NMJ INDICATIONS - Facilitate mechanical intubation - Facilitate various endoscopic diagnostic procedures - Facilitate electroconvulsive therapy  NONDEPOLARIZING NMJ PHARMACOKINETICS - effect is longer lasting - hydrophilic: don’t readily cross the BBB - metabolized in the serum, although metabolism is dependent on the liver to produce the needed plasma cholinesterases - excreted in the urine.  NONDEPOLARIZING NMJ CONTRAINDICATIONS - allergy - myasthenia gravis - renal or hepatic disease - pregnancy CAUTION - family or personal history of malignant hyperthermia - pulmonary or CV dysfunction - altered fluid and electrolyte imbalance - lactation  NONDEPOLARIZING NMJ ADVERSE EFFECTS - profound and prolonged muscle paralysis - depressed respiration, bronchospasm and apnea - respiratory obstruction with wheezing and bronchospasm - hypotension and cardiac arrhythmias - paralysis of muscles in GI tract - constipation, vomiting, regurgitation and aspiration - pressure ulcers - hyperkalemia  NONDEPOLARIZING NMJ DRUG-DRUG INTERACTIONS + Halogenated hydrocarbon anesthetics = membrane- stabilizing effect à greatly enhances the paralysis + Aminoglycoside antibiotics = leads to increased neuromuscular blockage + Calcium channel blockers = greatly increase the paralysis + Cholinesterase inhibitors = effectiveness decreased because of a buildup of ACh in the synaptic cleft + Xanthines = reversal of the neuromuscular blockage + Barbiturates = may form precipitate  DEPOLARIZING NMJ: Succinylcholine ACTIONS - attaches to the ACh receptor site on the muscle cell à causing a prolonged depolarization of the muscle. à stimulation of the muscle and muscle contraction à flaccid paralysis - rapid onset and a short duration of action because it is broken down by cholinesterase in the plasma  DEPOLARIZING NMJ: Succinylcholine INDICATIONS - an adjunct to general anesthesia - to facilitate endotracheal intubation - to induce skeletal muscle relaxation during surgery or mech vent PHARMACOKINETICS - Metabolized in serum, although metabolism is dependent on the liver to produce the needed plasma cholinesterases - Onset: 1 min; Duration: 10-12 mins - excreted in urine; crosses the placenta  DEPOLARIZING NMJ: Succinylcholine CAUTIONS - patients with fractures - narrow-angle glaucoma or penetrating eye injuries - with paraplegia or spinal cord injuries - genetic or disease-related conditions causing low plasma cholinesterase levels, such as cirrhosis, metabolic disorders, carcinoma, burns, dehydration, malnutrition, hyperpyrexia, thyrotoxicosis, collagen diseases, and exposure to neurotoxic insecticides  DEPOLARIZING NMJ: Succinylcholine ADVERSE EFFECTS - Muscle pain à prior: nondepolarizing NMJ blocker à after: Aspirin - Malignant Hyperthermia à massive muscle contraction, sharply elevated body temperature, severe acidosis, and if uncontrolled death à treatment: DANTROLENE  Nursing Considerations: ASSESSMENT (History & Examination) Any known allergies to Impaired liver or kidney function Myasthenia gravis Impaired cardiac or respiratory function Personal or family history of malignant hyperthermia Fractures, Narrow-angle glaucoma Paraplegia Current status of pregnancy or lactation  Nursing Considerations: ASSESSMENT (History & Examination) level of orientation, affect, reflexes, pupil size and reactivity, and muscle tone and response Monitor respiratory rate and auscultate lung sounds for evidence of adventitious sounds Temperature, pulse rate, and blood pressure Auscultate the abdomen for evidence of bowel sounds Inspect the skin for color and evidence of pressure areas or breakdown Monitor the results of laboratory tests, liver function tests  Nursing Considerations: NURSING DIAGNOSES Impaired gas exchange related to depressed respirations Impaired skin integrity related to immobility from prolonged drug effects Impaired verbal communication related to effects on muscle activity Fear related to paralysis Risk of injury related to loss of muscle control Pain related to prolonged muscle contraction with succinylcholine use Deficient knowledge regarding drug therapy  Nursing Considerations: PLANNING The patient will receive the best therapeutic effect from the drug therapy. The patient will have limited adverse effects to the drug therapy. The patient will have an understanding of the drug therapy, adverse effects to anticipate, and measures to relieve discomfort and improve safety.  Nursing Considerations: IMPLEMENTATION Be aware that administration of the drug should be performed by trained personnel (usually an anesthesiologist) à because of the potential for serious adverse effects and the need for immediate ventilatory support. Ensure that emergency supplies and equipment are readily available à to maintain airway and provide mechanical ventilation.  Nursing Considerations: IMPLEMENTATION Do not mix the drug with any alkaline solutions such as barbiturates à because a precipitate may form, making it inappropriate for use. Test patient response and recovery periodically if the drug is being given over a long period to maintain mechanical ventilation à Discontinue the drug if response does not occur or is greatly delayed. Monitor patient temperature à for prompt detection and treatment of malignant hyperthermia; have dantrolene readily available à for treatment of malignant hyperthermia  Nursing Considerations: IMPLEMENTATION Arrange for a small dose of a nondepolarizing NMJ blocker before the use of succinylcholine à to reduce the adverse effects associated with muscle contraction. Ensure that a cholinesterase inhibitor is readily available à to overcome excessive neuromuscular blockade caused by nondepolarizing NMJ blockers. Have a peripheral nerve stimulator on standby à to assess the degree of neuromuscular blockade, if appropriate.  Nursing Considerations: IMPLEMENTATION Provide comfort measures à to help the patient tolerate drug effects, such as pain relief as appropriate; reassurance, support, and orientation à for conscious patients unable to move or communicate; skin care and turning to prevent skin breakdown; and supportive care à for emergencies such as hypotension and bronchospasm. Monitor patient response closely (blood pressure, temperature, pulse, respiration, reflexes) to determine effectiveness; expect dose adjustment à to ensure the greatest therapeutic effect with minimal risk of toxicity.  Nursing Considerations: IMPLEMENTATION Provide thorough patient preoperative teaching about this drug à because most patients who receive the drug will be receiving teaching about a particular procedure and will be unconscious when the drug is given. Teaching includes drug to be given, method for administration, effects of the drug (i.e., what to expect), and safety precautions. Offer support and encouragement to help the patient to cope with drug effects.  Nursing Considerations: EVALUATION Monitor patient response to the drug (adequate muscle paralysis). Monitor for adverse effects (respiratory depression, hypotension, bronchospasm, GI slowdown, skin breakdown, fear related to helplessness and inability to communicate). Evaluate effectiveness of the teaching plan (the patient can relate anticipated effects of the drug and the recovery process). Monitor the effectiveness of comfort measures and compliance with the regimen. THANK YOU SO MUCH