No matter how successful the surgery, a patient’s experience of postoperative nausea and vomiting (PONV) can contribute to patient dissatisfaction, longer PACU stays, hospital readmission and overall perioperative costs. Pupillometric assessment can serve as a simple but accurate tool to help identify patients with PONV, a study has found, which can allow physicians to offer a more optimal recovery experience.
“Pupillometry has long been used to predict the severity of intraoperative and postoperative pain, and to determine the correct administered dose of opioids,” noted Simon Lee, MD, of Emory University Hospital Midtown, in Atlanta.
A study published in Anesthesia & Analgesia (2015;120:1184-1185) evaluated the pupillary response to a light stimulus before noxious procedures as a way to test pain control throughout the procedure. This study found that in patients who were unable to communicate, variation in pupil size could guide health care providers in adjusting analgesia before procedures.
With this study in mind, Dr. Lee and his team sought to examine whether it is possible to “extend” this practice and use pupillometry as a predictive factor in the development of nausea in the PACU.
Dr. Lee and his colleagues studied 47 patients undergoing elective surgery under general anesthesia at Emory University Hospital Midtown. All patients were 18 years of age or older and had no preexisting ocular issues. Head and neck surgeries and surgeries that required monitored anesthesia care were excluded.
An infrared pupillometer (Neuroptics) was used to assess average constriction velocity, maximum constriction velocity and pupillary size. Each patient was instructed to focus on a “distant object” for five seconds, and pupil diameter was measured in response to a light stimulus. The left eye was measured unless it was contraindicated, while the contralateral eye was kept closed.
Pupillary measurements were conducted throughout the preoperative, intraoperative and postoperative periods. Patients were then questioned on nausea symptoms postoperatively at 15 and 60 minutes after admission to the PACU.
“We ultimately found that the constriction velocity at 15 minutes is a very good marker to predict nausea and vomiting,” Eric Yang noted during a presentation at the 2015 New York State Society of Anesthesiologists PostGraduate Assembly. Mr. Yang is a second-year medical student at the University of Chicago Medicine and presented his team’s results at the conference.
Patients reporting nausea at 15 minutes showed significantly lower average (P=0.01) and maximal constriction (P=0.02) velocities at that time.
In analyzing the data, the team used receiver operating characteristic (ROC) curves for both average and maximal constriction velocity at 15 minutes. A 0.75 area under the curve indicated that both average and maximal constriction velocity have a strong diagnostic capability to detect PONV.
“The high degree of sensitivity and specificity that pupillometric assessment predicted was truly surprising,” noted Dr. Lee.
The ROC curves also displayed better diagnostic value for PONV than age, postoperative opioids and duration of surgery—all of which have been shown to be predictive of PONV.
“We suspect that patients with impaired pupillary light reflex measurements may have impaired autonomic balance upon discharge, which may result in increased rates of hospital readmission associated with postoperative nausea and vomiting,” Mr. Yang noted. “But we will need to continue this study and look to add any other variables, such as timing and type of opioid in the OR [operating room].”
Dr. Lee added that while their findings are not enough to provide evidence-based changes to standard practice at the moment, pupillometry assessment could prove to be a very useful tool to help tailor an anesthetic and administration of medication for prevention of PONV down the road.
“I’m hoping this will help us better prepare the patient for recovery, rather than just treat anesthetic-induced symptoms,” Dr. Lee said. “This will ultimately make their transition from the OR to the hospital bed—and later to their home—more smooth and comfortable.”