Postoperative analgesia can be a challenge to both patients and surgeons. For patients, postoperative abdominal pain can limit mobility, inspiration effort and appetite potentially leading to DVT, deconditioning, atelectasis, pneumonia and dehydration. It is clear that pain can cause significant morbidity, and it is paramount that the surgeon has knowledge of multiple treatment modalities that can be used together to avoid comorbidity while optimizing patient comfort.
Classically, opioid analgesia is a mainstay following abdominal surgery. Oral opiates are often used and can be supplemented with parenteral agents as needed if an inpatient setting is appropriate. Patient controlled analgesia, PCA, is utilized frequently as a way to avoid over use of parenteral opioid analgesia. With this approach the patient is able to control the dosing with computer driven limits to avoid over sedation and respiratory depression. In extreme cases, a basal rate of opiates can be administered with PCA in addition to the patient controlled bolus. This should only be used in cases where analgesia is difficult and the practitioner is familiar with basal rate administration.
Unfortunately, opioid analgesia has its drawbacks, especially in abdominal surgery. First, respiratory depression must be guarded against. Reversal agents should be available especially in the case of PCA use. Respiratory depression can also lead to problems like atelectasis and pneumonia; thus, respiratory hygiene is imperative while patients are using parenteral opiates. Postoperative ileus is a second problem that can be linked directly to opiate use. Abdominal surgery, open or laparoscopic, can certainly cause ileus, but this ileus can be exacerbated by opiate use. Increased inhibitory neural input, heightened inflammatory responses, decreased propulsive movements and increased fluid absorption in the gastrointestinal tract hallmark opioid-induced bowel dysfunction. Treatment of this problem is typically supportive, limiting opiate use as tolerated. There are reversal agents, however, it is difficult to induce reversal of the opioid-induced bowel dysfunction without reversal of the pain relief. Methyl naltrexone and alvimopan are recently developed opioid antagonists that are peripherally acting and have some success at reversal of opioid-induced bowel dysfunction.
With avoidance of opioid induced comorbidity in mind, there are several approaches which have been successful in limiting amount of narcotic needed in the post operative setting. Examples include: use of anti-inflammatory supplemental agents, use of continuous infusion analgesic pumps, use of epidural analgesia, and use of nerve blocks.
Supplemental anti-inflammatory medication can significantly limit opiate analgesic requirement for the postoperative patient. Intravenous acetaminophen and ketorolac are both anti-inflammatory agents that are routinely used in treatment of postoperative pain associated with abdominal surgery. Both agents significantly limit the need for opiates thus preventing the potential opiate induced- comorbidities. Intravenous acetaminophen and ketorolac both need to be monitored for their toxicities, liver and renal failure respectively. Ketorolac is especially useful in the treatment of ureteral colic both in the postoperative setting and the setting of acute ureteral obstruction. In the case of ureteral obstruction, it not only serves as an anti-inflammatory but also limits ureteral peristalsis and spasm.
Continuous infusion analgesic pumps are a popular method of treating incisional pain in laparoscopic and open abdominal procedures. These pumps continuously elaborate local anesthetic to the operative site via catheters that are left in situ for 36-72 hours. The pumps can be used in an inpatient and outpatient setting due to the ease of administration. Again, this strategy helps limit the need for narcotic analgesia thus improving outcomes by avoiding opioid-induced comorbid.
Epidural analgesia is a unique, inpatient option for regional analgesia following abdominal surgery. This technique is typically selected for a patient who is expected to spend multiple days in the hospital, or expected to have a slow return of bowel function. Either local anesthetic or narcotic can be infused into the epidural space with good efficacy. Infection is unusual. Limitations of epidural analgesia include: inability to anticoagulate, postoperative ileus, and bladder dysfunction resulting in prolonged urethral catheter use. Typically, the epidural infusion is managed by an anesthesia provider with experience in pain management.
The transversus abdominis plane block, TAP block, was first described by Rafi in 2001. This technique is performed under ultrasound guidance perioperatively. An anesthetic block is administered into the plane superficial to the transversus abdominis muscle and deep to the internal oblique. This provides excellent postoperative analgesia for both laparoscopic and open abdominal procedures. As in the examples above, the key with the TAP block is avoidance of overuse of opiates which can result in significant morbidity.
Postoperative pain management is essential in the field of surgery. While opiates are ubiquitous in this arena, multiple modalities are available to help avoid the potential associated comorbid problems. Many of these techniques not only limit opiate use but also decrease hospital stay. In turn these techniques can lead to better and more efficient outcomes as it relates to post operative recovery.
By Thomas K. Slabaugh, Jr., MD