PACU and Post-Op

1. What are the advantages of IV PCA over intermittent IV or IM administration?

Studies have shown IV PCA offers slightly better analgesic efficacy as well as superior patient satisfaction. IV PCA may also reduce post-operative pulmonary complications. It is also believed that IV PCA lowers the incidence of respiratory depression (as patients will fall asleep before they reach overdose thresholds).

2. When generating a patient's PCA order set, what does the lockout interval mean?

To prevent overdosage by continual demand, all PCA devices use a lockout interval (or delay), which is the length of time after a successful patient demand during which the device will not administer another demand dose (even if the patient pushes the demand button).

3. Is neuraxial morphine or fentanyl more likely to cause delayed ventilation depression? Why?

Neuraxial opioids depress respiratory centers in the brainstem via direct methods( vascular uptake from CSF and circulation to brainstem) or indirect methods (rostral migration of opioids to the brainstem via CSF).

A hydrophilic opioid such as morphine crosses the blood brain barrier slowly, and has slow plasma reuptake, maintaining concentrations in the CSF higher and for longer. As a result, morphine has extensive and prolonged rostral spread, resulting in delayed respiratory depression (6-12 h).

In contrast, lipophilic opioids (like fentanyl) distribute rapidly into the plasma and is responsible for early respiratory depression (20-30 min) via direct circulation to the brainstem.

4. How is ventilatory depression from neuraxial opioids monitored?

Monitoring ventilation (respiratory rate, depth of respiration via capnography), oxygenation (via pulse ox) and for clinical signs of respiratory depression (level of consciousness, labored breathing, cyanosis) should be performed for at least 2 hours after spinal fentanyl administration, and for 48 hours after spinal morphine administration.

5. How does DVT Prophylaxis with SQ Heparin affect the placement and removal of an epidural catheter for post-op analgesia?

Unfractionated Subcutaneous Heparin Alone (5000 u q8h):

• Catheter can be inserted any time after the dose, but ideally should be inserted > 8 hours after dose.
• Prophylactic dose should be avoided while the epidural is in place.
• Prophylactic dose can be given >2 hours after epidural is removed.

Unfractionated Subcutaneous Heparin + SCD (5000 units q12h):

• Catheter can be inserted any time after the dose, but ideally should be inserted > 8 hours after dose.
• Prophylactic dose should can be administered >2 hours after placement of catheter.
• Epidural catheter can be removed >4 hours after last heparin dose.
• Prophylactic dose can be given >2 hours after epidural is removed.

6. What are the signs and symptoms of an epidural hematoma? How is this diagnosis confirmed and treated?

• Most reliable (and sensitive) sign is developing motor block.
• Confirmation test: MRI.

7. Clinical Case

60 y/o, 90kg man is in the PACU recovering from an open cholecystectomy. He has a history of hypertension and MI. He is in a great deal of pain, especially with deep breathing.