Predictors of Post–PACU Analgesic Use In Children Following Outpatient Surgery Identified

More than one-third of children require at least one form of PACU analgesic after outpatient surgery, according to a recent study. The trial also unearthed several predictors of PACU opioid requirements, the most notable of which was a history of obstructive sleep apnea (OSA).

“The biggest challenge with respect to treating children in the ambulatory surgery center is postoperative pain, which affects as many as 60% of children,” said Olubukola O. Nafiu, MD, assistant professor of anesthesiology at the University of Michigan Health System, in Ann Arbor. “Anesthesia providers often hold back on the administration of opioids so they can get the patient out of the PACU on time or get them to breathe shortly after surgery. There’s also a misconception that since these are less invasive surgical procedures, they may not be accompanied by severe pain.

“All things considered, it would be nice to be able to predict at baseline which patients are going to require more pain medication after surgery.”

Since these factors are largely unknown, Dr. Nafiu and his colleagues set out to determine the incidence and risk factors for postoperative pain requiring treatment (i.e., PACU administration of any analgesic medication) in 558 children (mean age, 9.7±4.0 years; range, 4-17 years; 54.3% boys) undergoing elective ambulatory surgery.

“Other studies have looked at differences in pain scores as their end point,” he explained. “We felt that pain requiring treatment is a more easily measured outcome variable.” Univariate factors associated with postoperative pain requiring treatment also were assessed; the probability of postoperative pain requiring treatment was modeled using multivariable stepwise logistic regression analysis with age, sex, race, habitual snoring, surgical specialty, intraoperative morphine dose, intraoperative use of multimodal analgesia and duration of surgery as potential predictors.

As Dr. Nafiu reported at the 2016 annual meeting of the International Anesthesia Research Society (abstract S-31), 37.1% of the children received some form of analgesia in the PACU (27.8% received at least one IV opioid analgesic). Bivariable analysis revealed the following were significantly associated with PACU administration of any analgesia:

• increased arousal pain score (P<0.001);
• ear, nose and throat (ENT) or orthopedic surgery (P<0.001);
• longer surgical duration (P<0.001);
• higher intraoperative dose of morphine (P=0.005); and
• intraoperative use of multimodal analgesia (P=0.035).

“We found that patients requiring an analgesic intervention in the PACU also have longer PACU lengths of stay,” he said.

With respect to IV opioid requirement in the PACU, significant predictors were:

• habitual snoring (P=0.008);
• history of OSA (P=0.002);
• ENT or orthopedic surgery (P<0.001);
• minority ethnicity (P=0.002); and
• longer duration of surgery (P<0.001).

“Minority ethnicity is an interesting one,” Dr. Nafiu added. “It turns out there are some genetic differences in terms of response to opioids by race.”

Now That We Know, Then What?

Yet of all these, it was history of OSA (odds ratio, 4.4) that proved to be the most significant predictor of PACU opioid requirement. This, Dr. Nafiu explained, is a concern given the potential for delayed respiratory depression after these children are discharged home, and warrants efforts to personalize perioperative analgesia in these patients.

“What are you doing for your OSA patients now that you know they’re going to have more pain?” asked session moderator Meg Rosenblatt, MD, professor of anesthesiology and orthopedics at the Icahn School of Medicine at Mount Sinai and chair of anesthesiology at Mount Sinai St. Luke’s and Mount Sinai West Hospitals, in New York City. “Are they having more pain because nobody’s giving them appropriate analgesia in the OR [operating room]?”

“We’re all aware of the literature with respect to increased opioid sensitivity in patients with OSA,” Dr. Nafiu responded. “Since the typical practice is to make OSA patients ‘earn’ their opioids, we use multimodal analgesia to treat their pain from a variety of angles.”

“You also could also argue that IV opioids might be causing some hyperalgesia, thereby increasing the need for opioids postoperatively,” commented Donald M. Mathews, MD, professor of anesthesiology at the University of Vermont College of Medicine, in Burlington.