Post-op Pain Unaffected by IV Acetaminophen

Post-op Pain Unaffected by IV Acetaminophen After Minimally Invasive Spine Surgery – Pain Medicine News —Chase Doyle – Nov 2019

A study of perioperative IV acetaminophen in patients undergoing minimally invasive spine surgery has found no effect on postoperative pain.

However, that finding does not rule out its use for other surgeries, particularly more painful spine surgeries.

If it didn’t work for mild pain, how can they claim it would be useful for more severe pain? If opioids were studied and evaluated like this, they would be found effective for all kinds of pain. 

After thousands of years of use in all kinds of “patients” undergoing all kinds of “procedures”, opioids are simply the most effective pain relievers known to mankind. 

According to a retrospective analysis of 187 patients undergoing minimally invasive diskectomy, decompression or laminectomy at a single institution, results showed no difference in intraoperative/postoperative opioid use or pain scores in patients receiving IV acetaminophen compared with those who did not receive the analgesic agent

Since when did spinal surgery become “minimally invasive”?

“Although previous literature supports the benefit of including multimodal analgesia as part of an intraoperative pain management plan, our results failed to identify a measurable effect of perioperative acetaminophen alone on opioid requirements or pain scores,

“While intravenous acetaminophen may benefit a carefully selected subset of patients undergoing surgery, prospective carefully standardized studies need to be done to determine which patients will have the greatest benefit.”

Why do they believe this ineffective method will work for anyone, any “carefully selected subset of patients undergoing surgery”?

What makes them think some “selected” patients would get better pain relief and how would they determine the selection?

previous studies have demonstrated a rationale for the use of IV acetaminophen in multimodal analgesic regimens to reduce postoperative pain.

In order to explore its effect in spine surgery, which is often accompanied by severe pain, Dr. Ayrian and her colleagues initiated a trial to prospectively randomized patients undergoing minimally invasive spinal fusion surgery who received 24-hour IV acetaminophen versus oral acetaminophen versus no acetaminophen.

However, due to the high cost of IV acetaminophen, a shortage of remifentanil [strong opioid for use during surgery] and the disapproval of the research committee, the trial was stopped before completion.

This is extremely rare: a study stopped in the middle due to the disapproval of a research committee that must have originally approved the research. Perhaps the IV Tylenol was just too expensive for a study producing such mediocre results.

The researchers compared the total dose of opioid administered during and after surgery (24 hours) in patients receiving and not receiving IV acetaminophen.

In addition, within the IV acetaminophen group, patients who received IV acetaminophen in the first hour after surgical incision were compared with patients who had received IV acetaminophen more than one hour after surgical incision.

The researchers also compared initial, maximum and mean visual analog scale pain scores between groups.

Differences Lack Significance

Marie LeClair, MD, an anesthesiology resident at the University of Southern California, reported data that showed no significant effect of IV acetaminophen on median opioid use or pain scores.

Total intraoperative morphine milligram equivalents (MME) was

  • 20 mg in the acetaminophen group versus
  • 17.7 mg in patients not receiving acetaminophen (P=0.75).

This is strange. This study shows that acetaminophen *increases* pain because patients actually had 13% *more* pain when using IV Tylenol.

(Also, a p-value so much greater than the standard cut off of 0.05 means that all of this data is “statistically insignificant”.)

In addition, no significant difference was found with respect to initial, maximum or mean postoperative pain scores.

Also, patients receiving IV acetaminophen in the first hour of incision had statistically similar pain scores to patients receiving IV acetaminophen more than one hour after surgical incision.

No matter how hard they tried to “slice and dice” their data, they couldn’t find any pain relief provided by Tylenol. No surprise there.

The authors acknowledged several limitations with this retrospective study, including the lack of standardized analgesia.

How can a study on analgesia be done without standardized analgesia? It literally makes no sense, but in pursuit of their goal of finding Tylenol effective, they did the study despite these critical and obvious problems.

Patients With More Pain More Likely to Benefit

the most effective use of IV acetaminophen is likely in patients undergoing spine surgeries that typically have a lot of postoperative pain associated with them.

“It is not surprising that IV acetaminophen did not show a benefit for patients undergoing minimally invasive diskectomy, decompression or laminectomy,” said Dr. Sardar, who noted that these surgeries are often performed as outpatient surgeries where patients stay less than 24 hours in the hospital after the procedure.

“Since these patients tend to have low levels of pain, they end up using minimal amounts of opioid pain medications after the surgery. Therefore, adding additional pain medications such as IV acetaminophen doesn’t show an impact after these minor surgeries.

They say the patients weren’t in enough pain for Tylenol to make a difference. If a pain reliever is going to work, does it ever matter how much pain you’re in?

If you’re not in much pain, it should relieve 100% of it and if you’re in a lot of pain it might only relieve 20% of it.

But I’ve never heard of a pain reliever that only works for severe pain, but not mild pain. Is this just a new way to make Tylenol seem like a serious pain reliever instead of the lightweight it is?

“On the other hand, patients undergoing more extensive surgeries such as spinal fusions or correction of spinal deformity/scoliosis suffer from significant pain in the postoperative period,” Dr. Sardar added. “This subset of patients undergoing more extensive surgery are the more likely candidates to benefit from the use of IV acetaminophen.”

A.N. Shamie, MD underscored the differences in the specific surgeries selected for analysis that may have accounted for the study’s negative outcomes.

When they are studying opioids to show them as ineffective, they don’t try to find excuses or insist they would work better in other patients having other procedures.

Also, when a study is designed to show opioids are ineffective for one use, they generalize and claim they’d be ineffective for any other use as well.

“These are all very different patients,” said Dr. Shamie, who noted that a better definition of “minimally invasive” could have been provided, as well as the patients’ opioid needs before surgery. “Nevertheless, this study raises important questions in the field of pain management.”

First, they say that a different surgery might show Tylenol effective, now they say different patients might find it more effective.

Additionally, they point out the flaws in the study, which are the same flaws of all the opioids studies: there’s no mention of patients’ opioid use before surgery and the types of surgery are all mixed together.

About opioids, they never consider any other information and no one even asks about it, but when Tylenol is found ineffective they look for all the reasons the study might not have captured the reality they are so sure of, that Tylenol is a good pain reliever, whether the studies prove it or not.

“Helping patients use less opioids is a valuable area of research,” Dr. Shamie concluded. “IV acetaminophen needs to be studied prospectively in a randomized, placebo-controlled trial, but we should limit the study patients to smaller surgeries and bigger surgeries and see if acetaminophen has a different effect on microdiskectomy versus laminectomy.”

They keep making excuses for why Tylenol didn’t work and then insist that it would work in some hypothetical “different” situation with “different” patients. Yet opioids are considered ineffective regardless of who is taking them and what for. Such inconsistencies are pure hypocrisy.

I am always looking for ways to use fewer opioids, but Tylenol is NOT effective in me, not for a little pain and not for a lot.

5 thoughts on “Post-op Pain Unaffected by IV Acetaminophen

  1. Kathy C

    They have very likely done a lot more of these “studies,” and because they did not have the expected outcome, we will never hear about them. These physicians effectively tortured patients, allowing them to experience excruciating pain, while gas lighting them or pretending to treat the pain. If there had been the slightest misleading way to spin these negative outcomes, they would have trumpeted them across all media.

    Liked by 1 person

    1. Zyp Czyk Post author

      …and it’s darn dangerous! I’ll soon be posting an article about the “harms” from it, which nobody pays much attention to.

      In their zeal to substitute handfuls of ineffective OTC meds for opioids, they ignore any flaws in non-opioid pain relievers and ignore any positives about opioids. (I have to admit that I sometimes do a little of the same, just from the opposite end.)

      Liked by 1 person

  2. GZB

    I can’t begin to phrase how absurd this study was. I can unequivocally say that pain relief should be agreed to before anyone allows surgery to be done!

    Liked by 1 person

    1. Zyp Czyk Post author

      Absolutely! I wouldn’t dare go under the knife voluntarily these days without an agreement for post-op pain relief. I would need a different kind of “opioid contract” than what we have to sign theses days, with guaranteed access to opioids afterward.

      Liked by 1 person


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