McKenna's Pharmacology for Nursing, 2e

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

by these drugs ; hypovolaemia, which would require fluid replacement as treatment for the associated hypotension ; general anaesthesia with halogenated hydrocarbon anaesthetics, which could lead to serious cardiac effects (similar sensitisation can occur as a result of industrial solvent exposure) ; the presence of vascular disease, which could be exacerbated with the use of these drugs ; and current status of pregnancy and breastfeeding. ■ ■ Perform a physical assessment to establish baseline status before beginning therapy and during therapy to evaluate for any potential adverse effects and to determine the effectiveness of therapy. ■ ■ Assess vital signs, especially pulse and blood pressure, to monitor for possible excess stimulation of the cardiac system ; obtain an electrocardiogram (ECG) to evaluate for possible arrhythmias. ■ ■ Note respiratory rate and auscultate lungs for adventitious sounds to evaluate effects on bronchi and respiration. ■ ■ Monitor urine output to evaluate perfusion of the kidneys and therapeutic effects. ■ ■ Monitor the results of laboratory tests, such as renal and liver function tests, to determine the need for possible dose adjustment and serum electrolyte levels to evaluate fluid loss and appropriateness of therapy. Refer to Critical thinking scenario for a full discussion of care for a person who is experiencing adrenergic agonist toxicity. Implementation with rationale ■ ■ Use extreme caution in calculating and preparing doses of these drugs because even small errors could have serious effects. Always dilute a parenteral drug before use if it is not prediluted to prevent tissue irritation on injection. ■ ■ Use proper, aseptic technique when administering ophthalmic or nasal agents to prevent infection. ■ ■ Monitor people receiving the drug ophthalmically or nasally for all of the systemic effects associated with parenteral administration to prevent potentially serious adverse effects if the drug is absorbed systemically. ■ ■ Monitor response closely (blood pressure, ECG, urine output, cardiac output) and adjust dose accordingly to ensure the most benefit with the least amount of toxicity. ■ ■ Maintain phentolamine on standby in case extravasation occurs ; infiltration of the site

with 10 mL of saline containing 5 to 10 mg of phentolamine is usually effective in saving the area. ■ ■ Provide comfort measures to help the person cope with sympathomimetic effects of the drug; monitor light exposure to prevent sensitivity to light caused by pupil dilation , encourage voiding before giving the drug to alleviate urinary retention caused by sphincter contraction , monitor bowel function and provide assistance as needed to deal with GI suppression, and offer support and relaxation measures to deal with feelings of tension and anxiety. ■ ■ Provide the following teaching to people using these drugs orally or ophthalmically. Most of these drugs are given in emergency situations and teaching will be based on the person’s condition and awareness. Teaching includes: –– Drug name, prescribed dosage and schedule for administration –– Rationale for the drug –– Proper technique for administration –– Measures to prevent or avoid adverse effects –– Need to check with prescriber before taking any OTC medication –– Warning signs that might indicate a problem –– Importance of avoiding intake of caffeine- containing products –– Need for follow-up monitoring and evaluation Evaluation ■ ■ Monitor the response to the drug (improvement in blood pressure, ocular pressure, bronchial airflow). ■ ■ Monitor for adverse effects (cardiovascular changes, decreased urine output, headache, GI upset). ■ ■ Monitor the effectiveness of comfort measures and compliance with the regimen. ■ ■ Evaluate the effectiveness of the teaching plan (person can name the drug, dosage, adverse effects to watch for and specific measures to avoid them).

KEY POINTS

■■ Adrenergic agonists (sympathomimetics) stimulate the adrenergic receptors in the SNS. ■■ a - and b -adrenergic agonists stimulate all of the adrenergic receptors in the SNS. They induce a fight-or-flight response and are frequently used to treat shock.