Intraoperative Cefazolin Redosing and Persistent Hypotension
A 4-year-old male Doberman pinscher (40 kg) is undergoing exploratory laparotomy for a small intestinal foreign body. Cefazolin 880 mg IV was given at 08:00, and the incision was made at 08:15. At 10:30 the surgeon is still working; estimated blood loss is 120 mL. The patient's mean arterial pressure is 55 mmHg, HR 130, ETCO2 32 mmHg, and isoflurane is at 1.5%. A crystalloid bolus of 10 mL/kg was given over 15 minutes, and MAP is now 58 mmHg. The dog is otherwise stable.
1. Is the cefazolin dose and redosing schedule appropriate? Calculate and explain.
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The dose is appropriate: 22 mg/kg x 40 kg = 880 mg IV. The problem is the redosing interval. Intraoperative cefazolin is typically redosed every 90 minutes, or sooner with major blood loss. This surgery began at 08:15 and is still ongoing at 10:30, so a redose should have been given around 09:30. Give 880 mg IV now and document the time. If surgery continues, plan the next redose about 90 minutes later. The 120-mL blood loss is not large enough by itself to require a separate immediate redose, but the elapsed interval already does.
2. Interpret the MAP and propose the next hemodynamic step.
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A MAP of 55 mmHg is below the usual intraoperative target of at least 60-65 mmHg, and it improved only from 55 to 58 mmHg after 10 mL/kg (400 mL) of crystalloid. Give a second crystalloid bolus of 10-20 mL/kg (400-800 mL) over 15-20 minutes and reassess perfusion. If anesthetic depth allows, reduce isoflurane to improve blood pressure. Check PCV/TS, lactate, and ongoing blood loss. If the dog remains hypotensive after the second bolus, consider a colloid at 3-5 mL/kg or blood products if hemorrhage is suspected. Avoid repeated large boluses without reassessment.
3. What is the risk of the missed redose, and what nursing action should be taken?
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The risk is waning antimicrobial tissue concentrations during a contaminated abdominal procedure, which increases the chance of surgical site infection. The technician should alert the surgeon or anesthetist, administer the calculated 880-mg dose now, record the administration time, and set a timer for the next 90-minute interval. The missed dose should be documented factually in the anesthesia/surgical record so the team can review the redosing protocol.