Resident Readiness General Surgery 1st Ed.

A 75-year-old Man With Postoperative Pain

Ezra N. Teitelbaum, MD

A 75-year-old, otherwise healthy man undergoes an elective right hemicolectomy for colon cancer. The case was converted from laparoscopic to open due to dense adhesions from a prior laparotomy. Six hours after the operation, you are paged by the patient’s nurse because he is complaining of 8 out of 10 abdominal pain and his next dose of “prn” morphine is not available for another 2 hours.

When you arrive at the bedside, the patient is alert and answers all questions appropriately. He complains of a sharp pain along the length of his incision that was improved from 10 out of 10 to 6 out of 10 after receiving a dose of morphine 4 hours ago. In the past hour, however, the pain has been gradually increasing and is once again 10 out of 10. He is not nauseated and has not vomited.

His vital signs are: temperature 37.2°C, heart rate 85, blood pressure 150/90, and respiratory rate 12. His abdomen is soft with localized and appropriate tenderness along the length of the midline incision dressing. He is making 100 mL/h of clear yellow urine and, except for the pain, has been recovering well.

You review his medications and find he is ordered for “morphine 2 mg IV q6h prn pain.” He has received a single dose since arriving to the surgical ward 4 hours ago.

1. Why did you have to come see the patient and not simply provide a new order over the phone?

2. How would you change the order for his pain medications?

3. Name 3 common side effects of opioids.

4. Name 2 nonopiate medications that can be used in the immediate postoperative period (ie, when the patient is NPO).

5. When and how should this patient be transitioned to oral pain medications?

POSTOPERATIVE PAIN MANAGEMENT

Answers

1. When evaluating a patient complaining of an unusual amount of pain, or pain that is persistent despite the administration of medication, your first thought should always be that the pain might be the result of a surgical complication. While the most common cause of pain in the immediate postoperative period is inadequate analgesia, this should always be considered a diagnosis of exclusion. Therefore, patients with refractory pain need to be evaluated in person, and orders to increase the dose of narcotics should never be given over the phone. On your way to evaluate this patient you should be thinking of the possibility that bleeding, an anastomotic leak, or a missed bowel injury is responsible for his pain.

Your bedside history and physical exam should therefore focus on ruling out these serious complications. The fact that the patient’s pain is localized to his incision, rather than the site of the anastomosis (likely the RUQ or RLQ) or diffusely over the entire abdomen, is reassuring, as is the fact that the pain is partially relieved by medication. The patient’s vital signs are also within normal limits except for mild hypertension. Any fever, tachycardia, hypotension, or tachypnea in the immediate postoperative period is concerning and may be the result of hypovolemia (due to bleeding) or an inflammatory response (due to infection, anastomotic leak, or another complication). Hypertension in isolation is a common result of pain itself and is not immediately concerning (see Chapter 36 on postoperative hypertension for criteria for when you should be concerned).

The abdominal exam (or other surgery site–specific exam) is an essential component to differentiating between pain from inadequate analgesia and pain secondary to a complication. Patients with poorly controlled but uncomplicated pain should still have abdomens that are soft to palpation, especially away from the area of the incision. Your exam should thus start laterally (if you are examining a patient with a midline laparotomy) and proceed medially toward the incision. If the patient has an abdominal drain, then its output should be closely examined for bile, succus, stool, or frank blood.

If you are confronted with a patient with poorly controlled pain and any of these “warning signs,” you should notify your senior resident or the attending immediately. While it’s always good to come up with a plan for investigating potential complications (eg, checking a CBC to rule out bleeding) before making that call, such a workup should never be initiated on your own without keeping everyone “in the loop” about what is going on with a potentially sick patient.

2. After you have reassured yourself that this patient’s pain is not due to a surgical complication, the next step is to look at the existing pain orders and the medication administration record (MAR) to see how you can best address the inadequate analgesia. In this case, the patient’s morphine order has too low a dose and too long an interval between doses. For treating pain in an average patient after a laparotomy or other major surgery, an order of morphine 4 mg IV q3h or q4h is a good place to start. Keep in mind that younger adult patients and patients taking opioids chronically at home will typically require higher doses of narcotics. Conversely, elderly patients or those with renal insufficiency should be started on lower doses.

In this patient, starting a patient-controlled analgesia (PCA) pump is an even better solution than simply increasing the dose and frequency of his morphine order. A PCA allows patients to control the administration of intravenous opioids themselves by pressing a button attached to the PCA pump. The physician indicates in the PCA order the dose that is given with each button press and a “lockout” interval that is required to elapse between presses before the pump will administer a second dose.

PCAs are ideal for pain management in the immediate postoperative period for several reasons. The patient is in control of his or her own medication administration, and thus the time between when the patient begins to experience pain and when he or she finally receives medication is greatly reduced. Second, by providing small, frequent doses, a PCA allows for better medication titration to the required level, helping to avoid the “peaks and valleys” of pain often caused when a q3h or q4h prn opioid schedule is used. Lastly, PCAs limit the risk of opioid overdose, as the patient must be alert enough to press the pump button in order to administer another dose. A good starting PCA dose for a standard patient is morphine 1 mg, with a lockout interval of 8 minutes. Hydromorphone (trade name Dilaudid) is the other most popular IV opioid and is approximately 7 times as potent as morphine. A standard PCA order would be Dilaudid 0.1 or 0.2 mg with the same lockout interval of 8 minutes.

So far we have only discussed the use of “prn” or “breakthrough” pain medication that is administered when requested by the patient (via either the patient’s nurse or a PCA). The other, complementary, dosing option is a “standing” or “basal rate” in which patients receive the medication at a set time interval or continuously, regardless of whether they are in pain. In general, opioids should not usually be ordered in such a fashion due to the risk of narcotic overdose. Likewise, a basal administration rate on a PCA (by which patients get a set dose of narcotics every hour regardless of whether they press the pump button) should not be used except in special circumstances.

3. Opioids act on the central nervous system to depress consciousness and, ultimately, respiratory drive. Other than depressed mental status, the primary finding of opioid toxicity on physical exam is pinpoint and sluggishly reactive pupils. Opioid overdose is treated with IV naloxone; however, keep in mind that any narcotic overdose resulting in unresponsiveness or respiratory depression is a life-threatening emergency. Under no circumstance should you attempt to treat it on your own and if an inpatient is found in such a condition, a medical “code” should be called so that help arrives immediately.

Opioids can also cause delirium, especially in elderly patients. This can result in paradoxical agitation, confusion, and aggressive behavior. In older inpatients these side effects are often falsely attributed to dementia, even when the patient was not previously diagnosed with this condition. This is why it is extremely important to determine what the patient’s baseline mental status was when evaluating abnormal behavior in the hospital.

Another opioid side effect of critical importance in general surgery is the slowing of bowel peristalsis, resulting in ileus and/or constipation. For this reason, the total amount of opioids used should be limited whenever possible, especially after a bowel resection. Additionally, patients who are receiving opioids and can take oral medications should be placed on a prophylactic stool softener (ie, “bowel regimen”), such as docusate (trade name Colace) 100 mg PO BID. Another option is the relatively new medication alvimopan (trade name Entereg), an opioid antagonist that acts selectively in the enteric nervous system and has been shown to reduce the length of ileus after colon resections.

4. In order to minimize the use (and consequently the risk) of opiates, adjunct analgesic medications are sometimes used. The 2 most common medications are NSAIDs and acetaminophen (Tylenol). These are most effective if written “around the clock,” that is, they can serve as basal pain control while the opiates can be used for breakthrough pain. Numerous studies have demonstrated that this type of regimen results in lower total usage of opiates.

Acetaminophen is most useful after the patient is eating, although there is a formulation that can be given per rectum (PR) if the patient tolerates this route of administration. An intravenous formulation of acetaminophen (trade name Ofirmev) was recently approved by the FDA for postoperative pain management. However, as this is a relatively new medication prevalence of usage varies between institutions, and you should check with your senior resident or attending before ordering it. Acetaminophen is usually well tolerated, although it does have the well-known risk of hepatotoxicity. Total acetaminophen dose should not exceed 4 g in 24 hours—remember that this total includes any acetaminophen given as part of a mixed formulation such as Percocet or Vicodin. Acetaminophen should also be minimized in those patients with existing hepatic disease or those who have just undergone a liver operation.

Like acetaminophen, NSAIDs are also commonly added to a patient’s medical regimen in order to minimize opiate usage. The only commonly used IV NSAID is ketorolac (trade name Toradol), which is dosed at 15 or 30 mg IV q6h. As discussed above, it is usually ordered in a scheduled (rather than prn) fashion. While effective, Toradol does, however, have several important side effects. Toradol (as well as the other NSAIDs) is a mild anticoagulant, and for this reason you should never initiate its use postoperatively without first discussing it with the senior resident or attending. Second, NSAIDs can reduce renal perfusion and should be avoided in patients with impaired renal function. Patients on Toradol should have a daily chemistry ordered to check for an increase in their creatinine levels. NSAIDs also inhibit bone growth and are generally avoided in patients with fractures.

5. Generally, patients should be transitioned to an oral pain regimen as soon as they are started on a diet. Some surgeons will start their patients on PO pain medication when they are advanced to liquids; however, others will wait until patients are taking a regular diet, so you should always check before making this change. The most commonly used postoperative oral pain medications are combinations of acetaminophen and an opioid. These include Percocet (acetaminophen and oxycodone), Vicodin (acetaminophen and hydrocodone), and Tylenol #3 (acetaminophen and codeine). Morphine and Dilaudid can also be prescribed in oral form, but these are generally reserved for patients with chronic opioid usage (and thus tolerance) and are not used in standard postoperative situations. Oral NSAIDs, most commonly ibuprofen at 400 mg PO q6h, can be given in addition to the above medications, again in an effort to reduce the total opioid usage.

All opioids have different analgesic strengths per milligram and you should be generally familiar with the conversion factors between them. Table 23-1 shows a chart of standard pain medication doses and their relative strengths.

Table 23-1. Standard Pain Medications and Their Relative Strengths

Image

Although oral opioids have less severe side effects than those given IV, they still cause constipation. Patients should be placed on a bowel regimen when receiving them and be given a prescription for Colace (or another stool softener) on discharge.

TIPS TO REMEMBER

Image Assume that patients with an unusually high level of pain after an operation have a surgical complication. Inadequate analgesia is a diagnosis of exclusion.

Image PCAs are an effective delivery method for IV opioids in the immediate postoperative period. In general, PCAs should not be ordered with a basal rate (ie, a continuous infusion).

Image All pain medications have side effects. Opioids can cause depression of consciousness and respiratory drive, and delirium in the elderly, and can cause or prolong ileus. NSAIDs can increase the risk of bleeding and can be nephrotoxic.

Image When a patient’s diet is advanced after surgery, he or she should be transitioned to oral pain medications as soon as possible.

Image A prophylactic bowel regimen should be ordered for all patients receiving opioids and who are able to take PO medications.

COMPREHENSION QUESTIONS

1. In which of the following patient populations should ketorolac (brand name Toradol) not be used? (Choose all that apply.)

A. Trauma patients with subdural hematomas

B. Patients with type II diabetes

C. Patients with chronic renal insufficiency

D. Patients with dementia

2. Which of the following is an appropriate PCA order for a patient immediately after a laparotomy?

A. Morphine 3 mg per dose, with a lockout interval of 2 minutes

B. Dilaudid 1 mg per dose, with a lockout interval of 8 minutes

C. Morphine 1 mg per dose, with a lockout interval of 8 minutes

D. Dilaudid 0.2 mg per dose, with a lockout interval of 2 minutes

3. On postoperative day 1 after a laparoscopic gastric bypass, a patient is complaining of what you think is unusually intense epigastric pain. What other finding would make you most concerned for an anastomotic leak?

A. Heart rate of 120

B. White blood cell (WBC) count of 10.5

C. Urine output of 75 mL/h

D. Blood pressure of 160/80

4. What dose of Dilaudid IV is equivalent to the amount of oxycodone in a single Percocet tablet?

A. 0.1 mg

B. 0.33 mg

C. 0.5 mg

D. 1 mg

Answers

1. Both A and C. Toradol is an anticoagulant and can be nephrotoxic, so it should be avoided in patients with (or at risk for) bleeding or impaired renal function.

2. C. All of the other choices have either too high a dose (morphine 3 mg or Dilaudid 1 mg) or too short a lockout interval (2 minutes).

3. A. Tachycardia along with an abnormal amount of pain should alert you that a complication may have occurred.

4. B. Each Percocet tablet contains 5 mg of oxycodone, which is equivalent to 0.33 mg of IV Dilaudid.