Recommendations on Effective Pain Management Approaches in the Hospital Setting

Achieving safe, effective pain control for inpatients can challenge even experienced clinicians. Components of successful pain control include avoiding pain crises while still steering clear of respiratory depression, being confident with equianalgesic calculations, and transitioning to the outpatient setting.

UC-San Diego’s Eric Roeland, MD addressed these and other issues encountered in pain control for the inpatient population on the final day of the Society for Hospital Medicine’s 2013 annual conference, held May 17-19 at the National Harbor’s Gaylord Nelson Convention Center in Ft. Washington, MD. Roeland began by drawing an analogy between insulin dosing to control blood glucose and opioid dosing to achieve pain control. In both cases, a basal level of medication, either in a long-lasting form or via continuous infusion, provides baseline control, while short-acting medication is available when spikes occur. The basic dosing strategies are the same, whether for blood glucose or pain control.

The first step to achieving pain control is to identify the etiology and perform a thorough and accurate pain assessment. Characterizing the pain as constant, constant with breakthrough pain, or intermittent will help tailor the intervention strategy. A variety of visual analog scales and nonverbal pain scales are available, and can help supplement the interview when documenting “the sixth vital sign.” Pain ratings can help guide initial opioid choice and route: for pain of 1-3, opioids are probably not necessary. With pain ratings of 4-7, consider codeine, tramadol, or combination preparations of acetaminophen with codeine, hydrocodone, or oxycodone. When pain ratings are at 7-10, consider morphine, hydromorphone, oxycodone, fentanyl, or even methadone; also be ready for aggressive titration to effect. Adjuvants can also be useful for pain at any level.

Another important component of the history is to differentiate a history of adverse effects to opioids from true allergies, which are rare. Careful questioning about any history of anaphylaxis and compromised airway is important; pruritis, while uncommon, does occur as an adverse reaction but is not an indication of allergy. Anticipating and providing prophylaxis for adverse effects can be helpful. In particular, pruritis can be treated with cetirizine, nausea with prochlorperazine or ondansetron (though ondansetron can exacerbate constipation), and constipation itself should be managed with stimulant laxatives such as bisacodyl or senna -- stool softeners alone are unlikely to be sufficient to alleviate constipation.

A few simple rules of thumb clarify opioid pharmacokinetics: For all opioids except methadone, time to peak serum concentration, or Cmax, for IV opioids is about 10 minutes, about 30 minutes for IM or subcutaneously administered opioids, and oral dosing achieves Cmax in about one hour. Serum half-life of all opioids but methadone is about four hours. Drug formulations designed to provide sustained release, whether oral or transdermal, alter drug delivery and must be taken into account; with these caveats, opioids reach steady state in four to five half-lives, or 16-20 hours. This means that checking pain control and tolerability at 24 hours will capture the steady state drug effect. Most opioids, except methadone and fentanyl, are excreted through the urine, so verifying (and documenting) adequate urine output is important in the inpatient setting.

Careful calculation with independent checking and clear documentation; verification of adequate urine output; consideration of drug-drug interactions; and monitoring for and treatment of side effects all contribute to successful and safe inpatient pain control. In determining a 24-hour opioid dose for a patient who is not opioid-naive, equianalgesic guidelines are available and should be followed closely, since dosing must account for incomplete cross-tolerance as well as adjusting for changes in route of administration. Roeland recommends using‑‑and documenting‑‑a simple ratio formula to convert from one analgesic/route of administration to another analgesic/route of administration.

When initiating patient-controlled analgesia (PCA), consider starting with a prn dose alone: “aggressive prn doses are safer than aggressive basal doses.” Remembering the principle that sedation precedes overdose and respiratory depression, clinicians should make sure all staff and family members know that only the patient should administer a PCA dose.

When initiating opioid dosing, consider rapid bedside titration. This method, which should only be used in patients with adequate urine output, involves sitting at the bedside, or within sight of the patient, and administering an opioid dose at every Cmax (every 10 minutes for IV administration). In his hospice and palliative care practice, Roeland doubles the dose at every Cmax until adequate pain control is achieved. The dose at which this happens becomes the prn opioid dose. Bedside titration allows close monitoring for respiratory depression as well as rapid pain control. Even if physicians are not comfortable with doubling the opioid dose so frequently, the bedside monitoring/rapid titration method can still be a useful method of initiating pain control via PCA. Checking on patients at Cmax and after one half-life gives useful information about analgesic effectiveness and side effects at time points which are pharmacokinetically important.

As with performing equianalgesic conversions, PCA dosing should be done by hand and checked independently by another prescriber or pharmacist, and all steps documented in the patient record. Roeland prefers not to use EMR calculators for dosing: “Automatic calculators lead to automatic thinking and automatic errors,” he says.

Finally, when tapering a patient from a PCA and preparing for home, Roeland recommends planning ahead when feasible: First, any basal PCA rate should be transitioned to a long acting oral medication, and then prn IV dosing should be transitioned to prn oral opioids. Ideally, the patient should be able to achieve steady state on the oral regime before discharge. When the taper process can occur in a stepwise fashion over a three day period, transition to an effective oral regime goes more smoothly.