13.2 Medication Delivery Routes and Devices in Critical Illness
Key Takeaways
Medication delivery in the ICU is shaped by anatomic alterations (post-surgical anatomy, short bowel), altered GI motility, fasting status, and unreliable enteral absorption in shock; alternative routes (IV, sublingual, rectal, subcutaneous, intramuscular, inhaled) are selected per drug properties.
IV access choice (peripheral vs. central) depends on vesicant properties, pH, osmolarity, and duration; vasopressors, concentrated electrolytes, TPN, and vesicant chemotherapy require central access.
Smart infusion pumps with dose error reduction systems (DERS) and drug libraries reduce medication errors; pharmacist role includes library maintenance, hard/soft limits, and pump integration with CPOE.
Specialized delivery routes (intrathecal/epidural, intraosseous, intranasal, nebulized, intraperitoneal) each have unique considerations; intrathecal vincristine is fatal and requires explicit labeling and separation protocols.
Medication Delivery Routes and Devices in Critical Illness
Route Selection in the ICU
| Route | Indication | Considerations |
|---|---|---|
| Oral/NG/NJ | Functional GI tract | Absorption affected by gastric pH, motility, fasting, surgery; check compatibility with feeding tube |
| Sublingual | Rapid onset, first-pass avoidance | Limited drug availability (nitroglycerin, lorazepam, buprenorphine) |
| Rectal | When PO not possible | Acetaminophen, diazepam, levetiracetam available; unpredictable absorption |
| IV bolus | Immediate effect | Risk of rapid vasodilation, hypotension, arrhythmia; max rates per drug |
| IV infusion | Continuous dosing, titration | Smart pump required; central access for vesicants |
| Subcutaneous | Heparin prophylaxis, insulin | Absorption impaired in shock/edema |
| Intramuscular | Limited in ICU | Avoid in coagulopathic, edematous patients |
| Inhaled | Pulmonary delivery | Bronchodilators, corticosteroids, prostacyclin; ventilator circuit considerations |
| Epidural/intrathecal | Analgesia, chemotherapy | Strict sterility; preservative-free only |
| Intraosseous (IO) | Emergency access | Any IV medication can be given; pain on infusion |
| Topical/transdermal | Systemic or local effect | Fentanyl, nitroglycerin, clonidine; absorption affected by perfusion |
| Intraperitoneal | Peritoneal dialysis, intraperitoneal chemo | Strict sterile technique |
Anatomic Alterations and Delivery
- Post-gastrectomy, Roux-en-Y, short bowel: rapid transit, reduced absorption surface; extended-release formulations often ineffective; prefer immediate-release and IV forms.
- Ileostomy/colostomy: short colon reduces absorption of extended-release drugs.
- Whipple, esophagectomy: feeding jejunostomy for post-pyloric delivery; medications must be liquid or crushable.
- Tracheostomy: inhaled medications via trach; MDI with adapter.
- Post-esophagectomy with gastric pull-through: dumping syndrome; small frequent feeds; reduced absorption of slowly absorbed drugs.
Altered GI Physiology in Critical Illness
- Reduced gastric motility: opioids, sepsis, diabetes gastroparesis → delayed gastric emptying → erratic absorption. Use prokinetics (metoclopramide, erythromycin); convert to post-pyloric feeding.
- Reduced splanchnic perfusion: shock reduces mucosal absorption; IV preferred until stable.
- Altered gastric pH: PPIs reduce absorption of ketoconazole, atazanavir, enoxapargin; increased absorption of weak bases.
- Fasting status: food-dependent absorption (e.g., cefuroxime axetil increases with food); tube feed interactions (phenytoin binds to enteral formula).
IV Access and Drug Compatibility
Choice of IV Access
| Drug Property | Access Required |
|---|---|
| Vesicant (norepinephrine, dopamine, potassium, calcium, chemotherapy) | Central (or large-bore peripheral with careful monitoring) |
| pH <5 or >9 | Central |
| Osmolarity >600 mOsm/L | Central |
| TPN | Central (dedicated lumen) |
| Concentrated dextrose >10% | Central |
| Phlebitis-causing (amiodarone, vancomycin, potassium) | Central preferred |
Y-Site Compatibility
Compatibility charts must be checked; examples of incompatible Y-site combinations:
- Ceftriaxone + calcium-containing fluids (fatal precipitate).
- Phenytoin + dextrose (crystallizes; use NS only).
- Amiodarone + heparin (precipitate).
- Pantoprazole + iron (precipitate).
Smart Infusion Pumps and DERS
Dose Error Reduction Systems
- Hard limits: cannot be overridden without pharmacy approval (e.g., heparin >2x upper limit).
- Soft limits: can be overridden with documented reason (e.g., norepinephrine titration above protocol max).
- Drug library: per clinical area (ICU, OR, ED, general floor).
- Smart pump interoperability: integration with CPOE and MAR to auto-populate infusion parameters reduces 50% of pump programming errors.
Pharmacist Role
- Quarterly drug library review and update.
- Set hard/soft limits per institutional protocol.
- Review intercepted errors and adjust limits.
- Education on pump library selection at shift change.
Inhaled Medication Delivery in Mechanically Ventilated Patients
- MDI with chamber adapter: 4-10x recommended dose due to deposition in circuit; preferred for ventilated patients.
- Nebulizer: continuous output; interrupts ventilator circuit (infection risk).
- Particle size: 1-5 microns reaches lower airway.
- Bronchodilators, corticosteroids, antibiotics (tobramycin, colistin), prostacyclin, heparin (inhalation injury).
Intrathecal and Epidural Delivery
- Intrathecal: baclofen for spasticity, methotrexate/cytarabine for CNS leukemia, bupivacaine/opioid for analgesia.
- Epidural: bupivacaine, fentanyl, hydromorphone for post-op analgesia.
- NEVER give vincristine intrathecally — universally fatal within days. Tall man lettering (VINCRISTine) and dedicated preparation areas required.
Intraosseous (IO) Access
- Emergency access when IV cannot be established within 90 seconds.
- Any IV medication, including blood products and vasopressors, can be given IO.
- Sites: proximal humerus, proximal tibia, distal tibia, sternum.
- Bolus with 10 mL NS to clear marrow; rapid infusion may cause pain.
- Replace with IV as soon as possible.
Special Delivery Devices
- Patient-controlled analgesia (PCA): with dosing limits; pharmacist-programmed.
- Patient-controlled analgesia with basal infusion: high-risk for opioid naive; avoid.
- Ambulatory elastomeric pumps: home antibiotic infusions.
- Implantable pumps: intrathecal baclofen, intrathecal pumps for pain/spasticity.
- Closed-loop systems: artificial pancreas, automated anesthesia delivery; emerging.
Clinical Scenario
A patient with septic shock on four vasopressors via peripheral IVs develops norepinephrine extravasation at a peripheral site. The forearm is pale, cold, and painful. What is the appropriate intervention?
Answer: Stop the infusion immediately. Leave cannula in place and aspirate. Administer phentolamine 5-10 mg in 10 mL NS subcutaneously around the extravasation site using a 25-gauge needle, infiltrating in a circular pattern (alpha-blockade reverses ischemia). Apply warm compresses (alpha-agonist extravasation). Avoid cold compresses (worsen vasoconstriction). Document the event, monitor for necrosis, surgical consult if no improvement within 12-24h. Convert all other vasopressors to central access urgently.
Which medication must NEVER be administered intrathecally due to fatal neurotoxicity, and what safeguards are required to prevent this error?
Methotrexate — separate storage and yellow labeling
Vincristine — dispensed only in IV minibags (never syringes), tall man lettering VINCRISTine, dedicated prep area separate from intrathecal drugs
Cytarabine — limited to once-weekly dosing
Baclofen — required bolus test dose
A mechanically ventilated patient requires inhaled bronchodilator therapy. Which delivery approach provides the highest lung deposition in intubated patients?
MDI without chamber
Nebulizer placed in inspiratory limb
MDI with chamber adapter at the Y-piece, multiple actuations
Inline MDI placed at the humidifier
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