The most common opioid adverse effects are postoperative nausea and vomiting (PONV), pruritus, hypotension, and sedation. Respiratory depression is less common but is the most feared of the opioid adverse effects. The adverse effects of opioids are dose dependent. Thus, the single most effective, safest, and least expensive treatment is to give the lowest effective opioid dose (Pasero, Quinn, Portenoy, McCaffery, & Rizos, 2011). Decreasing the opioid dose is facilitated by adding or increasing the dose of a nonopioid, such as an NSAID or acetaminophen, and using local anesthetics for peripheral nerve blocks or adding a local anesthetic to the epidural opioid solution to provide additional pain relief.
Consensus guidelines present a number of recommendations for the management of PONV (Gan et al., 2007, 2014). Algorithms that incorporate guideline recommendations are available (American Society of PeriAnesthesia Nurses [ASPAN], 2006; Gan et al., 2007, 2014). Key points are to identify patients at high risk for PONV (e.g., females, those with a prior history of motion sickness or PONV, nonsmokers, emetogenic surgery, and those who use postoperative opioids); reduce baseline risk factors (e.g., implement multimodal analgesic strategies); and administer PONV prophylaxis for patients with a moderate-to-high risk. Prophylactic antiemetic treatment is not recommended in low-risk patients; however, antiemetic treatment is provided in those who develop PONV and did not receive prophylaxis or in whom prophylaxis failed (Gan et al., 2007, 2014).
Pruritus (itching) is an adverse effect, not an allergic reaction to opioids (Ho & Gan, 2009). A number of treatments are used in an effort to relieve itching, and there is no consensus on which method is most effective. Although they are widely used, there is no strong evidence that antihistamines, such as diphenhydramine (Benadryl), relieve opioid-induced pruritus (Grape & Schug, 2008). Patients may report being less bothered by itching after taking an antihistamine, but this is likely the result of sedating effects (Ho & Gan, 2009). Sedation can be problematic in those already at risk for excessive sedation, such as postoperative patients, as this can lead to life-threatening respiratory depression (Anwari & Iqbal, 2003). Thus, careful monitoring of sedation levels is recommended when antihistamines are combined with opioid administration, and they should not be administered if patients are excessively sedated.
Opioid antagonists (e.g., naloxone [Narcan]) and agonist-antagonists (e.g., nalbuphine [Nubain]) are sometimes used to treat pruritus; however, this practice risks reversal of analgesia if the administered doses are too high. Pain must be monitored closely when opioid antagonists are used. Numerous studies have shown that serotonin receptor antagonists, such as ondansetron, dolasetron, and granisetron, prevent pruritus caused by intraspinal opioids (Charuluxananan, Somboonviboon, Kyokong, & Nimcharoendee, 2000; Gurkan & Toker, 2002; Henry, Tetzlaff, & Steckner, 2002; Iatrou et al., 2005; Pirat, Tuncay, Torgay, Candan, & Arslan, 2005). A common clinical observation is that postoperative patients with opioid-induced pruritus also have well-controlled pain, tolerate a small reduction in opioid dose without any loss of analgesia, and experience a significant reduction or resolution of their pruritus (Pasero, Quinn, Portenoy, McCaffery, & Rizos, 2011). This should be considered prior to or in conjunction with pharmacologic treatment.
Although the opioid doses commonly used for pain management rarely cause hypotension (Ho & Gan, 2009; Pasero, Quinn, Portenoy, McCaffery, & Rizos, 2011), when it does occur, it is more likely to be in individuals with high sympathetic tone, such as those with pain or poor cardiac function, or in patients who are hypovolemic. In fact, addressing pain is important because pain may contribute to hemodynamic instability. In other words, opioids should not be withheld for fear of causing hypotension. When hypotension is a concern, it can be minimized by administering the opioid slowly, keeping the patient supine, and optimizing intravascular volume (Harris & Kotob, 2006; Ho & Gan, 2009). Therapy can begin with a small dose while closely observing patient response. Administration of opioids via slow IV infusion may be appropriate in some patients (Harris & Kotob, 2006).