McKenna's Pharmacology for Nursing, 2e

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C H A P T E R 2 7 General and local anaesthetic agents

should be used with caution in any individual at high risk for developing it to avoid development of malig- nant hyperthermia. Dantrolene, the preferred treatment for malignant hyperthermia, should be readily available whenever any of these drugs is used. These drugs should be avoided in pregnancy and breastfeeding unless the benefit clearly outweighs the risk to the fetus or baby because of the CNS depressive effects of the drugs. Adverse effects Desflurane is associated with a collection of respiratory reactions, including cough, increased secretions and laryngospasm. Isoflurane is associated with hypoten- sion, hypercapnoea, muscle soreness and a bad taste in the mouth, but it does not cause cardiac arrhythmias or respiratory irritation as do some other volatile liquids. Clinically important drug–drug interactions Caution should be used when any of these drugs is combined with other CNS suppressants. Prototype summary: Isoflurane Indications: Induction and maintenance of general anaesthesia. Actions: Depresses the CNS, causing anaesthesia; relaxes muscles; sensitises the myocardium to the effects of noradrenaline and adrenaline. Pharmacokinetics: Route Onset Peak Duration Inhaled Rapid Rapid End of inhalation T 1/2 : Unknown; minimally metabolised in the liver, excreted in the urine. Adverse effects: Disorientation, restlessness, bradycardia, tachycardia, hypoxia, acidosis, malignant hyperthermia, hyperkalaemia, respiratory depression, apnoea, dyspnoea, arrhythmias, hepatic injury, ileus, shivering. Volatile liquid anaesthetics can trigger malignant hyperthermia and are contra-indicated in those susceptible to malignant hyperthermia. They can increase cerebrospinal pressure and should be used with caution in those with raised intracranial pressure. They can also cause hepatotoxicity in those sensitised to halogenated anaesthetics. In children with neuromuscular disease, inhalational anaesthetics are very rarely associated with hyperkalaemia, resulting in cardiac arrhythmias and death. Cardiorespiratory depression, hypotension and arrhythmias are common adverse effects of volatile liquid anaesthetics. ■■ BOX 27.2  Adverse reactions

Care considerations for people receiving general anaesthetic agents

Assessment: History and examination

■ ■ Assess for contraindications or cautions: any known allergies to general anaesthetics to avoid hypersensitivity reactions ; impaired liver or kidney function, which might interfere with drug metabolism and excretion ; myasthenia gravis or cardiac or respiratory disease, which may be exacerbated by the depressive effects of the drug ; personal or family history of malignant hyperthermia, which may be triggered by the use of general anaesthetics. ■ ■ Perform a physical assessment, including weighing the person, to determine the appropriate dosing of the drug and to establish a baseline status before beginning therapy and evaluate for any potential adverse effects. ■ ■ Assess the person’s neurological status, including level of consciousness, affect, reflexes and pupil size and reaction, and evaluate muscle tone and response, to monitor CNS depression and provide appropriate support as needed. ■ ■ Monitor vital signs, including temperature, pulse and blood pressure, for changes, and auscultate lung and heart sounds to monitor for adverse effects of the drugs. ■ ■ Obtain an electrocardiogram (ECG) to evaluate for underlying cardiac problems that may be exacerbated by the drug. ■ ■ Assess skin colour and lesions to monitor for potential skin breakdown resulting from paralysis and immobility while under anaesthesia. ■ ■ Auscultate abdomen for bowel sounds to evaluate GI motility. ■ ■ Monitor the results of laboratory tests, including renal and liver function tests, to determine the possible need for a reduction in dose and evaluate for possible toxicity. ■ ■ Keep in mind that the drug must be administered by trained personnel (usually an anaesthetist) because of the potential risks associated with its use. ■ ■ Have emergency equipment to maintain airway and provide mechanical ventilation readily available when person is not able to maintain respiration because of CNS depression. ■ ■ Monitor temperature for prompt detection and treatment of malignant hyperthermia. Maintain dantrolene on standby. Implementation with rationale