A nurse is reviewing laboratory results of a client who has atrial fibrillation and is taking warfarin. For which of the following results should the nurse notify the provider?

Choice A reason: Bradycardia is not an adverse effect of diphenhydramine. Bradycardia is a slow heart rate, usually below 60 beats per minute. Diphenhydramine is an antihistamine that blocks the effects of histamine, a chemical that causes allergic reactions. Diphenhydramine does not affect the heart rate, although it may cause palpitations or irregular heartbeat in some cases.

Choice B reason: Constipation is an adverse effect of diphenhydramine. Constipation is a condition in which the bowel movements are infrequent, hard, or difficult to pass. Diphenhydramine has anticholinergic properties, which means it inhibits the activity of acetylcholine, a neurotransmitter that regulates the smooth muscle contraction in the gastrointestinal tract. Diphenhydramine can reduce the intestinal motility and cause constipation, as well as dry mouth, blurred vision, and urinary retention.

Choice C reason: Hypertension is not an adverse effect of diphenhydramine. Hypertension is a condition in which the blood pressure is abnormally high, usually above 140/90 mmHg. Diphenhydramine does not affect the blood pressure, although it may cause orthostatic hypotension, which is a sudden drop in blood pressure when changing positions from lying to standing. This can cause dizziness, fainting, or falls.

Choice D reason: Sedation is an adverse effect of diphenhydramine. Sedation is a state of reduced alertness, awareness, or responsiveness. Diphenhydramine can cross the blood-brain barrier and affect the central nervous system, causing drowsiness, fatigue, impaired coordination, and reduced mental performance. Diphenhydramine can also potentiate the effects of alcohol and other sedatives, such as benzodiazepines, opioids, or barbiturates. The nurse should advise the client to avoid driving, operating machinery, or performing other tasks that require attention and concentration while taking diphenhydramine.

Choice A reason: Using IV tubing specific for heparin sodium when administering the infusion is not the correct action. Heparin sodium can be administered using any standard IV tubing, as long as it is primed with heparin solution to prevent clotting in the tubing.

Choice B reason: Administering 50,000 units of heparin by IV bolus every 12 hours is not the correct action. This is a very high dose of heparin that can cause bleeding complications. The usual dose of heparin for continuous IV infusion is 15 to 25 units/kg/hour, adjusted according to the aPTT results.

Choice C reason: Having vitamin K available on the nursing unit is not the correct action. Vitamin K is the antidote for warfarin, not heparin. Vitamin K reverses the effects of warfarin by increasing the synthesis of clotting factors in the liver.

Choice D reason: Checking the activated partial thromboplastin time (aPTT) every 4 hours is the correct action. The aPTT is a blood test that measures the time it takes for the blood to clot. It is used to monitor the effectiveness and safety of heparin therapy. The therapeutic range of aPTT for heparin is 1.5 to 2.5 times the normal value, or 60 to 80 seconds. The nurse should check the aPTT every 4 hours until it is within the therapeutic range, and then every 6 to 8 hours thereafter. The nurse should adjust the heparin infusion rate according to the aPTT results and the prescriber's orders.