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IV Acetaminophen Reduces Need for Opioids in Burn Patients

Small study finds IV acetaminophen could be included in the initial and perioperative pain control protocol of burn patients based on its analgesic effect, safety profile, stable pharmacodynamics, limited adverse events, and easy accessibility.
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Inadequate pain management of burn patients can lead to post-traumatic stress disorder, depression, and other psychiatric disorders.

Poor pain management of burn patients has long-lasting effects, even after the burn itself is healed. Several studies have established an association between inadequate burn pain control and subsequent development of psychiatric disorders, such as post-traumatic stress disorder, delirium, maladaptive behaviors, and depression.1,2 In addition, poorly managed pain, combined with a catabolic state in burn patients, contributes to immune system impairment, which increases the risk of infection.

The pain associated with burns, which involves both nociceptive and mechanical pain pathways, is one of the most challenging forms of acute pain to treat. The tissue damage secondary to burns causes intense activation of nociceptors via chemical mediators, and the surgical protocol for burn injuries usually worsens the severity of the pain due to secondary mechanical injury. Finally, the cycle of compounding pain in itself will restrict and interfere with the patient’s ability to participate in physical therapy and functional restoration, increasing the length of the hospital stay and, thus, promoting further complications.

A multimodal pain management approach is warranted, and medication selection may vary according to the extent of injury and system involvement. Traditionally, opioids are the first line in the analgesic management algorithm of burn pain, and due to the severity of the pain, patients commonly will use larger than usual doses and, thus, will have more pronounced adverse events (AEs).

The aim of this prospective study was to determine the role of intravenous (IV) acetaminophen in reducing the amount of opioids burn patients require.

Study Methods

After institutional review board (IRB) approval, all patients admitted to the burn service were selected for participation in this study. Written consents were obtained.

The inclusion criteria consisted of voluntary participation, with patients older than age 18 and younger than 75 included. In addition, to be included patients had to have avoided nonsteroidal anti-inflammatory drug (NSAID)- or acetaminophen-containing products the day of the surgery, had to have an American Society of Anesthesiologist (ASA) health status of 1 or 2, and had to have an injury involving less than 20% of their body surface area (BSA) from any type of burn.

Between May 2013 and May 2016, patients admitted to the burn intensive care unit, burn service step-down unit, and surgical floor were surveyed. The patients were then assigned to receive 1 of 2 pharmacologic treatments after a burn-related surgery: the intervention group received 4 doses of 1,000 mg of IV acetaminophen plus IV opioids (morphine or hydromorphone) and patient-controlled analgesia (PCA); the control group received PCA morphine or hydromorphone.

The surgical procedure performed in all patients was a split thickness skin graft (STSG) that consisted of debridement of the epidermis of the affected area followed by a repair with an autologous skin graft, usually collected from the thigh.

The medication administration protocol for the intervention group involved an initial dose of 1,000 mg IV acetaminophen prior to surgical incision, with subsequent administration every 6 hours for a total of 4 doses over 24 hours.  

Opioid administration to both groups was performed via PCA for at least 24 hours. It was discontinued only after the patients were able to tolerate oral medications and their pain was controlled with these medications. The total use of opioids for 24 hours was recorded.

We surveyed the patients’ pain control with a questionnaire that included a numerical scale assessing pain at preoperative, immediate postoperative, overnight, and interview time points. Additionally, we used a 1- to 5-point scale, with 1 point signifying complete dissatisfaction and 5 points signifying complete satisfaction with the pain control methods used. Finally, we added 2 questions and used the same 1- to 5-point scale to assess the patients’ knowledge of AEs and whether pain control was the patients’ main priority.

The study’s primary objective was to establish whether there was any difference in opioid consumption between the 2 study groups, expressed in IV morphine equivalents (IVMEs). Secondary objectives included the evaluation of any difference in pain scores between the groups, reduction in the baseline pain score, the total amount of opioid used, and patient satisfaction with the pain control measures.

For the primary objective, we used independent t-tests to compare the groups with respect to pain scores and morphine-equivalent consumption.

Study Results

A total of 61 patients met our inclusion criteria. The patients’ mean age was 43.3 years, and there was no age difference between the 2 groups.  

Out of 29 patients in the intervention group, all received 1 IV acetaminophen dose (1,000 mg) during the procedure, but only 25 (86%) received the complete protocol of 4 doses (4,000 mg). Of the 4 patients who did not complete the whole IV protocol, 2 received 2 doses (2,000 mg), were managed with PCA opioids, and were dropped from the study. The remaining 2 patients were dropped due to the use of spinal anesthesia during the procedure.

Of the 32 control patients, 9 were dropped from the study: 2 patients due to the use of spinal anesthesia, 2 received IV NSAIDs or oral hydrocodone in the recovery unit, 3 did not get a PCA, and 2 were discharged home the same day.

Based on the patients who were eligible and completed the survey, the average rating of preoperative pain score was 6.72 in the intervention group and 6.13 in the control group (P=0.37). The average postoperative pain rates were 7.04 and 7.34, respectively (P<0.78), whereas the overnight score rating was 4.8 in the intervention group compared with 5.56 in the control group (P<0.34). Finally, pain scores at the time of the interview were 4.6 and 4.73, respectively (P<0.48). These results indicate that there was no statistical difference in pain scores between the 2 groups.

The 24-hour PCA usage was monitored after the arrival to the recovery unit. The morphine PCA settings were standardized to 1 mg every 8 minutes with an 8 mg/hour limit. The hydromorphone settings were left to provider preference, and the total dose conversion of hydromorphone to morphine was 7:1; both groups had similar numbers of hydromorphone users.  

When comparing the total amount of opioids used, the average amount of IVMEs was 35.6 mg in the intervention group vs 52.3 mg in the control group (Figure 1). There was a statistically significant difference between the control and intervention groups, showing 30% more opioid consumption in the control group (P<0.041).

In regard to patient satisfaction with the method used, the majority of the control group (75%) was completely satisfied with the method used, and the remaining patients (25%) were mostly satisfied. In the intervention group, only half (52%) were completely satisfied with the method used, 32% were mostly satisfied, and 16% were partially satisfied.

Last updated on: December 12, 2016
First published on: December 1, 2016
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