McKenna's Pharmacology for Nursing, 2e

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P A R T 5  Drugs acting on the autonomic nervous system

Contraindications and cautions Isoprenaline is contraindicated in the presence of allergy to the drug or any components of the drug to avert hypersensitivity reactions ; with pulmonary hyper- tension, which could be exacerbated by the effects of the drug ; during anaesthesia with halogenated hydrocarbons, which sensitise the myocardium to cat- echolamines and could cause a severe reaction ; with eclampsia, uterine haemorrhage and intrauterine death, which could be complicated by uterine relaxation or increased blood pressure ; and during pregnancy and breastfeeding because of potential effects on the fetus or neonate. Caution should be used with diabetes, thyroid disease, vasomotor problems, degenerative heart disease or history of stroke, all of which could be exacerbated by the sympathomimetic effects of the drug and with severe renal impairment, which could alter the excretion of the drug. Adverse effects People receiving isoprenaline often experience adverse effects related to the stimulation of sympathetic adrener- gic receptors. CNS effects include restlessness, anxiety, fear, tremor, fatigue and headache. Cardiovascular effects can include tachycardia, angina, myocardial infarction and palpitations. Pulmonary effects can be severe, ranging from difficulty breathing, coughing and bronchospasm to severe pulmonary oedema. GI upset, nausea, vomiting and anorexia can occur as a result of the slowing of the GI tract with SNS stimulation. Other anticipated effects can include sweating, pupil dilation, rash and muscle cramps. Prototype summary: Isoprenaline Indications: Management of bronchospasm during anaesthesia; vasopressor during shock; adjunct in the management of cardiac standstill and arrest, as well as serious ventricular arrhythmias that require increased inotropic action. Actions: Acts on beta-adrenergic receptors to produce increased heart rate, positive inotropic effect, bronchodilation and vasodilation. Pharmacokinetics: Route Onset Duration IV Immediate 1–2 mins T 1/2 : Unknown; metabolised in the tissues. Adverse effects: Restlessness, apprehension, anxiety, fear, cardiac arrhythmias, tachycardia, nausea, vomiting, heartburn, respiratory difficulties, coughing, pulmonary oedema, sweating, pallor.

Clinically important drug–drug interactions Increased sympathomimetic effects can be expected if this drug is taken with other sympathomimetic drugs. Decreased therapeutic effects can occur if this drug is combined with b -adrenergic blockers.

Care considerations for people receiving β -specific adrenergic agonists

Assessment: History and examination

■ ■ Assess for contraindications or cautions: any known allergies to any drug or any components of the drug to avoid possible hypersensitivity reactions ; pulmonary hypertension, which could be exacerbated by the effects of the drug ; anaesthesia with halogenated hydrocarbons, which sensitise the myocardium to catecholamines and could cause severe reaction ; eclampsia, uterine haemorrhage and intrauterine death, which could be complicated by uterine relaxation or increased blood pressure ; diabetes, thyroid disease, vasomotor problems, degenerative heart disease or history of stroke, all of which could be exacerbated by the sympathomimetic effects of the drugs ; severe renal impairment, which could interfere with the excretion of the drug ; and current status of pregnancy and breastfeeding. ■ ■ Perform a physical assessment to establish a baseline before beginning therapy and during therapy to determine the drug’s effectiveness and identify any potential adverse effects. ■ ■ Assess cardiovascular status, including pulse rate and blood pressure, to evaluate for any cardiovascular effects associated with SNS stimulation ; obtain an ECG to evaluate for changes indicating excessive SNS stimulation. ■ ■ Assess respiratory status and listen for adventitious sounds to monitor drug effects and assess for any adverse effects. ■ ■ Monitor urine output to evaluate renal function and kidney perfusion. ■ ■ Monitor laboratory test results, including thyroid function tests, blood glucose levels and renal function, to monitor drug effects and potential adverse effects. Implementation with rationale ■ ■ Monitor pulse and blood pressure carefully during administration to arrange to discontinue the drug at any sign of toxicity. ■ ■ Ensure that a β -adrenergic blocker is readily available when giving parenteral isoprenaline in case severe reaction occurs.