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  • Writer's pictureTracy Harrison

Everything to Know About Pre-operative Use of Acetaminophen for Pain

Updated: Jan 15, 2023

The proper management of acute pain after a surgical procedure, physical trauma, or in those with an acute painful medical condition is imperative. Many believe we are in the midst of a public health crisis when a systematic approach to pain management is not held to the position of the 'gold standard' of care. While some institutions and individuals do pay attention to the variety of medications and strategies available for optimal pain management, there remains a great opportunity to improve quality of life, patient-provider communication, and functionality with a more widespread attention to acute pain management.

The World Health Organization (WHO) principles suggest that safer, non-opioid medications should be the first-line agents for all types of pain: mild, moderate, or intense. As such, many providers consider acetaminophen as the foundation of a pain management plan while taking into consideration the need for other agents as the expected intensity of pain increase as associated with various surgical procedures.

Learn more about the WHO Pain Relief Ladder here.

Here, I will review the evidence for the use of acetaminophen in the pre-operative period, specifically using acetaminophen in a proactive (rather than reactive) manner.

The first paper I will discuss is titled

published in JAMA in 2017. Dr Wick describes many different multimodal techniques as part of the enhanced recovery after surgery pathway (ERAS). However, this post will focus on the use of acetaminophen only. This is an excellent paper and the interested reader should read the entirety of the journal article (check it out here). Rather than using this strategy (ERAS) for individuals undergoing a select procedure, I believe this philosophy should be considered for all surgical patients, using the strategies appropriately weighing the risks and the benefits, based on the expected intensity associated with the procedure or medical condition.

Some Procedures are Known to be Associated with Mild, Moderate, or Severe Pain.

It Is Predictable.

Use Acetaminophen on a Scheduled rather than PRN (as needed) Basis

Wick advocates for the use of acetaminophen on a scheduled rather than on a PRN (as needed) basis. Perhaps if an individual is having a procedure associated with only mild pain, it might be reasonable to offer acetaminophen on a PRN basis. However, instrumental to good pain management is being proactive and anticipating potential increases in pain, and this is were the PRN dosing can fall short. Particularly when an individual is expected to increase their functioning a day after a surgical procedure, maintaining adequate pain management is an important component of healing. Acetaminophen can be an effective pain reliever and, when added to opioids, produces superior analgesia and can have an opioid-sparing effect. This in turn may result in fewer side effects commonly experienced with opioids, including nausea, vomiting, or sedation.

Acetaminophen is Synergistic with NSAIDS (Makes Them Work Better)

Acetaminophen can also be co-administered with a non-steroidal anti-inflammatory drug (NSAID) for even greater efficacy. Depending upon the perceived burden an individual experiences with taking medications, one can administer acetaminophen and NSAIDs at the same time or consider administration at different times. If providing both medications on a scheduled basis, the blood stream concentration will stay relatively stable. The maximum dosage of acetaminophen should not exceed 3 - 4 grams / day for any patient.

The second article I will discuss is titled 'Intravenous acetaminophen reduces postoperative nausea and vomiting: A systematic review and meta-analysis' by Christian Apfel et al published in the journal Pain (check it out here).

Be Proactive about Nausea /Vomiting

Acetaminophen Can Help!

Addressing nausea and vomiting associated with pain or anesthetic technique is imperative when considering the patient experience and recovery after a surgical procedure. While it is known that acetaminophen reduces opioid requirements, data is now becoming available to suggest that nausea and vomiting may be reduced as an additional benefit.

Prophylactic IV acetaminophen reduced postoperative nausea and vomiting (PONV) and was most effective when given before surgery and intraoperatively, but not when treatment was initiated after onset of pain. The reduction of PONV correlated with the reported reduction of pain, but not postoperative opioid consumption. In addition, it was determined that a single dose of prophylactic IV acetaminophen is at least as effective as repeated doses or as antiemetics.

Do not exceed 3000 mg in 24 hour period for adult-sized individual (>50 kg)

Dosing Considerations

Dosing for acetaminophen is as follows:

Children: 10 mg / kg IV / PO q 4 hours (max dose 650 mg)

15 mg / kg IV / PO q 6 hours (max dose 1000 mg)

Adults: 650 mg IV / PO q 4 hours

1000 mg IV / PO q 6 hours

How To Decide Frequency of Dosing?

Generally we need to acknowledge the burden of taking oral medication. Particularly in children and those individuals who might find it difficult and traumatic to receive medication, dosing acetaminophen every six hours would seem reasonable. Alternatively, there could be a benefit for some individuals of knowing they are receiving medication more frequently, thus every four hour dosing would seem reasonable. This represents a placebo response, which is powerful and cannot be ignored.

Regarding the scheduled versus as-needed dosing for acetaminophen, I am a strong advocate for scheduled dosing for those patients undergoing procedures associated with moderate or intense pain, especially if they receive concurrent opioid medications for pain. Those patients with mild pain can receive as-needed acetaminophen; scheduled acetaminophen should be considered if pain is ongoing and continuous, rather than intermittent and predictable. It is reasonable to reassess the pain management plan on a regular basis, at least once daily if not more frequently. If the medication is administered on a scheduled basis, the plasma level will be relatively the same regardless of receiving the medication every four or six hours.

Contraindications to acetaminophen include allergy to acetaminophen, elevated liver function tests, or concurrent administration of other acetaminophen-containing medications. You'll find this information in the PreEmpt Pain smartphone app.

Take Away Points

- Administer acetaminophen as a first-line agent based on the expected intensity of pain

- mild expected pain

- scheduled or as-needed (PRN) acetaminophen

- moderate expected pain

- scheduled acetaminophen ( + non-pharm strategies +/- opioids)

- intense expected pain

- scheduled acetaminophen ( + non-pharm strategies +/- opioids)

- Administer in the preoperative area or prior to the onset of the pain stimulus if possible

- Administer acetaminophen along with an NSAID (such as ibuprofen) if no contraindications for improved efficacy

- Do not exceed 3 g / day total dose of acetaminophen

- Be proactive about nausea and vomiting. Preemptive IV acetaminophen can be helpful to decrease the incidence of nausea and vomiting; administer in preop area or during anesthesia. Effect is minimized when administered after the onset of pain

- Reassess efficacy at least once daily

A Public Health Crisis Exists Without a Systematic Approach to Pain Management As 'The Gold Standard' of Care

First-Line agents such as acetaminophen are only the beginning of the pain plan. Stay tuned to this space for release of the PreEmpt Pain smartphone app. Want the opportunity to have input in this pain management tool designed for YOU? Leave a comment or ask a question below.

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