9.2 Recognizing Medication Effects & Adverse Reactions
Key Takeaways
- Intracoronary nitroglycerin (100–200 mcg) relieves epicardial spasm and aids vessel sizing; IV nitroglycerin lowers preload/BP and is contraindicated with recent PDE5 inhibitors
- Adenosine causes transient AV block and hyperemia for FFR; prolonged symptomatic bradycardia requires atropine and possible pacing support
- Iodinated contrast reactions range from urticaria to anaphylaxis—severe hypotension with bronchospasm or angioedema requires epinephrine and full resuscitation
- Sedation with midazolam/fentanyl can cause respiratory depression; flumazenil and naloxone must be immediately available with continuous SpO₂ monitoring
- Vasopressor selection matches the hemodynamic pattern: phenylephrine for vasodilatory hypotension, epinephrine for anaphylaxis and arrest
9.2 Recognizing Medication Effects & Adverse Reactions
Quick Answer: RCIS Task 13 tests whether you recognize expected therapeutic effects and adverse reactions of cath lab drugs—nitroglycerin, adenosine, atropine, vasopressors, iodinated contrast, sedatives, antiarrhythmics, and anticoagulants—then notify the operator and support stabilization within your scope.
Medication recognition is pattern matching under pressure: a 20 mmHg pressure drop after intracoronary nitroglycerin may be therapeutic; the same drop after sedation may be dangerous. The RCIS exam rewards candidates who connect drug class → expected effect → warning sign → first action without confusing unrelated complications.
Nitroglycerin (NTG)
Mechanism: Nitric oxide donor → venodilation (preload ↓) and epicardial coronary dilation (spasm relief).
| Route | Typical cath lab use | Expected effects | Adverse reactions / pitfalls |
|---|---|---|---|
| Intracoronary (IC) | 100–200 mcg for spasm and vessel sizing before PCI | Improved luminal diameter; transient BP ↓ | Headache; hypotension if hypovolemic; tachyphylaxis with repeated IC doses |
| IV infusion | Hypertensive emergency, flash pulmonary edema (physician-directed) | BP ↓, pulmonary congestion ↓ | Reflex tachycardia; hypotension; contraindicated with PDE5 inhibitors (sildenafil ≤24 h, tadalafil ≤48 h) and suspected RV infarction |
RCIS tip: IC nitroglycerin treats epicardial spasm and optimizes angiographic assessment—it is not primarily an antihypertensive for systemic hypertension (that is IV NTG). If BP falls sharply after IC dose in a volume-depleted patient, notify the operator, trend pressures, and prepare IV fluids per orders.
Adenosine
Mechanism: Activates A1 receptors → AV nodal block, coronary hyperemia (FFR), very short half-life (~10 sec).
| Use | What you should see | Adverse effects | Your response |
|---|---|---|---|
| FFR hyperemia (IV or IC) | Transient dyspnea, chest heaviness, flushing, brief AV block | Prolonged asystole/bradycardia (especially with sick sinus), bronchospasm in reactive airway disease | Monitor ECG/pressure continuously; atropine and temporary pacing available; notify operator if block outlasts drug |
| SVT termination (IV bolus 6–12 mg) | Rapid arrhythmia break | Same as above plus hypotension | Stop infusion if using pump; record ECG strip |
Contraindications/high caution: Second-/third-degree AV block without pacemaker, severe reactive airway disease, hypotension. Methylxanthines (theophylline, caffeine) blunt effect.
Atropine
Mechanism: Anticholinergic → ↑ heart rate, ↑ AV conduction.
| Indication | Dose | Expected effect | Toxicity |
|---|---|---|---|
| Symptomatic bradycardia (adenosine, carotid massage, conduction disease) | 0.5–1 mg IV, repeat to 3 mg | HR ↑, symptoms improve | Dry mouth, flushing, urinary retention; paradoxical bradycardia at low doses possible |
| Organophosphate/nerve agent (rare) | Higher doses per ACLS | Secretions ↓ | Anticholinergic delirium |
In the cath lab, atropine most often follows adenosine-induced AV block or vagal reactions during carotid sinus stimulation or temporary pacing insertion.
Vasopressors and Inotropes
When hypotension threatens coronary perfusion during PCI or after sedation/contrast reaction, operators may order push-dose pressors or infusions.
| Agent | Primary effect | Cath lab context | Key adverse effects |
|---|---|---|---|
| Epinephrine | α + β agonist | Anaphylaxis, cardiac arrest, severe hypotension | Tachyarrhythmias, hypertension, demand ischemia |
| Norepinephrine | α > β | Sepsis-like or vasodilatory shock after sedation | Peripheral ischemia at high doses, arrhythmias |
| Phenylephrine | Pure α agonist | Hypotension with reflex bradycardia acceptable | Hypertension, ↓ HR |
| Dobutamine | β1 inotrope | Low cardiac output states (caution in ischemia) | Tachycardia, ectopy |
| Vasopressin | V1 receptor | ACLS, vasodilatory shock | Ischemic gut/digital ischemia |
RCIS action pattern: Notify operator immediately, repeat blood pressure, ensure IV access, prepare ACLS drugs, document time/dose/response. Do not independently titrate infusions outside protocol.
Iodinated Contrast Media
Contrast reactions span mild (nausea, urticaria) to life-threatening anaphylaxis.
| Reaction severity | Findings | First-line support (with operator) |
|---|---|---|
| Mild | Rash, pruritus, isolated hives | Antihistamine, monitor |
| Moderate | Bronchospasm, diffuse urticaria, facial edema | Oxygen, H1/H2 blockers, steroids, albuterol if wheezing |
| Severe / anaphylaxis | Hypotension, angioedema, stridor, shock | Epinephrine IM/IV, fluids, airway assessment, call for help |
Contrast-induced nephropathy (CIN) is a subacute effect (creatinine rise 48–72 h), not immediate wheezing. Recognize risk factors: CKD, diabetes, heart failure, large contrast volume, hypotension during case.
Extravasation of contrast (not allergy) causes local swelling/pain—elevate limb, monitor pulses, notify operator, document; do not confuse with anaphylaxis.
Sedation: Midazolam, Fentanyl, Propofol
| Agent | Therapeutic effect | Warning signs | Reversal / support |
|---|---|---|---|
| Midazolam | Anxiolysis, amnesia | Respiratory depression, hypotension | Flumazenil (caution: seizures if chronic benzo use) |
| Fentanyl | Analgesia | Respiratory depression, chest wall rigidity (rare rapid push) | Naloxone (may reverse analgesia) |
| Propofol | Deep sedation (where credentialed) | Apnea, hypotension | Airway support, vasopressors, stop infusion |
Monitor SpO₂, respiratory rate, blood pressure, and level of consciousness per institutional sedation policy. RCIS items may ask what to do when EtCO₂ rises and SpO₂ falls after fentanyl—answer: notify operator, assist ventilation, prepare naloxone.
Antiarrhythmics in the Lab
| Drug | Use | Effect to recognize | Toxicity |
|---|---|---|---|
| Amiodarone | VT/VF, hemodynamically unstable VT | Rate ↓, BP may ↓ (slow infusion) | Hypotension (rapid bolus), QT prolongation (chronic) |
| Lidocaine | VT (alternative) | CNS sedation at high levels | Seizures, asystole overdose |
| Procainamide | Stable VT (less common now) | QRS widens | Hypotension, proarrhythmia |
During PCI-related VT, your priority is recognition + notification + preparation while the operator directs cardioversion/defibrillation and drug bolus.
Anticoagulation Effects (Intraprocedural)
| Agent | Therapeutic marker | Bleeding signal | Thrombosis signal |
|---|---|---|---|
| UFH | ACT in target range | Hematoma, groin bleed, ACT too high | ACT subtherapeutic, clot in sheath |
| Bivalirudin | ACT (partially) + time from dose | Less bleeding than heparin + IIb/IIIa in trials | Acute stent thrombosis if stopped early—follow protocol |
| GP IIb/IIIa | Clinical bleeding | Thrombocytopenia, mucosal bleeding | Used less routinely now |
Protamine reverses UFH but can cause hypotension, bradycardia, and anaphylactoid reactions—recognize sudden BP drop after protamine as drug effect, not just vagal.
Pattern Recognition Scenarios for RCIS
- Sudden hypotension + flush after IC nitroglycerin in spasm → expected; continue monitoring unless symptomatic or extreme.
- Pause >6 sec on ECG after adenosine → usually self-limited; atropine if symptomatic or prolonged.
- Wheezing + hypotension after contrast → anaphylaxis pathway, not "mild allergy."
- Somnolence + RR 6/min after midazolam/fentanyl → respiratory depression; airway first.
- Groin expanding hematoma with ACT 320 → over-anticoagulation/bleeding; notify operator, hold further anticoagulation, prepare reversal per orders.
Documentation and Escalation
Every adverse reaction requires:
- Time of drug and time of symptom onset
- Vital signs, ECG rhythm, ACT if relevant
- Interventions given and patient response
- Operator notification documented
Recognizing medication effects is the safety net behind anticipation—CCI expects you to differentiate therapeutic hypotension from shock, adenosine pause from complete heart block needing pacing, and contrast allergy from extravasation without delaying escalation when the patient is unstable.
Thirty seconds after an intravenous adenosine bolus for SVT, the patient remains in sinus rhythm but is hypotensive (BP 78/50) with ongoing dyspnea and 8-second pauses on the monitor. What is the most appropriate RCIS action?
Five minutes after iodinated contrast injection, the patient develops diffuse urticaria, wheezing, and BP 82/48 mmHg. Which recognition-and-response pairing is correct?
Which findings are commonly expected therapeutic or benign effects of intracoronary nitroglycerin during diagnostic angiography? (Select all that apply.)
Select all that apply