Double-Checking CRI Orders for a Dog with Pancreatitis
A 10 kg, 8-year-old spayed female mixed-breed dog is hospitalized with acute pancreatitis. She has vomited six times in 24 hours, is approximately 5% dehydrated, and has a painful cranial abdomen. The veterinarian writes the following orders: '0.9% NaCl + 20 mEq KCl per liter at 60 mL/kg/day; metoclopramide CRI 2 mg/kg/day; fentanyl CRI 2 µg/kg/hr; maropitant 1 mg/kg IV q24h.' Each CRI is to be delivered by a syringe driver at a rate you select. The clinic stocks 1 L 0.9% NaCl bags, KCl 2 mEq/mL, metoclopramide 5 mg/mL, fentanyl 50 µg/mL (a CII drug), and 0.9% NaCl flushes. The dog has a cephalic catheter and is producing urine. Later in the shift a relief veterinarian writes on the treatment sheet, 'Metoclopramide 2 mg/kg IV q8h - please start.'
1. Calculate the fluid rate in mL/hr and the volume of KCl to add to a 1 L bag. State the checks you perform before that bag is hung, and calculate the potassium delivery rate in mEq/kg/hr.
Read the worked answer
Fluid rate: 60 mL/kg/day × 10 kg = 600 mL/day ÷ 24 = 25 mL/hr. (In drops with a 60 gtt/mL set, that is 25 gtt/min.)
KCl: 20 mEq per 1 L bag ÷ 2 mEq/mL = 10 mL of KCl added to the 1 L bag. Invert the bag several times - potassium chloride is denser than saline and pools at the bottom, so an unmixed bag can deliver a concentrated bolus. Label the bag with additives, total mEq, date, time, and your initials.
Potassium rate delivered: 20 mEq/L × 0.025 L/hr = 0.5 mEq/hr = 0.05 mEq/kg/hr, well under the usual ceiling of about 0.5 mEq/kg/hr for a peripheral line. That is the calculation to document, because the ceiling is a rate, not a concentration.
Checks before hanging: the dog is urinating (confirmed here - never add potassium to the fluids of an anuric patient); the catheter is patent and not perivascularly placed; the pump is programmed at 25 mL/hr with an independent double-check by a second staff member; and the bag is not a bolus. Recheck the potassium in 6-12 hours.
2. Design the metoclopramide CRI for a 24-hour syringe at 1 mL/hr. Show the total milligrams needed, the volume of stock drug, and the diluent volume. Then evaluate the relief veterinarian's additional order.
Read the worked answer
Total dose: 2 mg/kg/day × 10 kg = 20 mg/day. At 24 hours, that is 20 ÷ 24 = 0.833 mg/hr.
Concentration needed: if the syringe driver runs at 1 mL/hr, the syringe must contain 0.833 mg/mL. Over 24 hours the syringe volume is 24 mL, so total drug = 0.833 × 24 = 20 mg.
Preparation: 20 mg ÷ 5 mg/mL = 4 mL of metoclopramide stock, added to 20 mL of 0.9% NaCl = 24 mL total in a 30 mL syringe (4 + 20 = 24). Label with drug, concentration (0.833 mg/mL), total dose, rate, time, and initials, and check the pump programming against the label with a second person.
The relief order is a dose error. 'Metoclopramide 2 mg/kg IV q8h' delivers 6 mg/kg/day - three times the intended 2 mg/kg/day - and an IV push of metoclopramide can also cause extrapyramidal signs and marked behavior change. The CRI is already running, so this is not additive therapy; it is a different regimen for the same indication. The correct action is to not start it, call the relief veterinarian and the primary clinician, clarify which order stands, and document the clarification in the treatment sheet. When in doubt, ask before you administer.
3. Design the fentanyl CRI at 2 µg/kg/hr, choosing a convenient driver rate. What controlled-substance and compatibility practices apply?
Read the worked answer
Dose: 2 µg/kg/hr × 10 kg = 20 µg/hr.
Choose a rate of 2 mL/hr (an easy, standard syringe-driver rate). Concentration needed = 20 ÷ 2 = 10 µg/mL. Over 24 hours the syringe holds 48 mL, so total fentanyl = 10 × 48 = 480 µg → 480 ÷ 50 µg/mL = 9.6 mL of fentanyl stock, diluted with 38.4 mL of 0.9% NaCl to 48 mL in a 50 mL syringe (9.6 + 38.4 = 48).
Controlled-substance practice: fentanyl is schedule II. Two staff members witness and document the volume removed from the vial and the volume wasted; the syringe is labeled with drug, concentration, total dose, time prepared, preparer, and expirer; the line is labeled 'fentanyl' at both the syringe and the patient end; the pump settings are independently double-checked; and the drug is stored in the locked cabinet between uses. Use a dedicated syringe driver rather than mixing fentanyl and metoclopramide in one syringe, because there is no reason to combine them and no compatibility data to support it. If both must run through one catheter, use a Y-site with one-way valves and separate pumps.
Monitor sedation score, respiratory rate and effort, SpO2/ETCO2 if available, and pain score every 1-2 hours, and remember that fentanyl's context-sensitive half-life means the infusion should be tapered rather than stopped abruptly after prolonged use.