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P A R T 5
Drugs acting on the autonomic nervous system
■■
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.
KEY POINTS
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).
