Skip to main content

Rigor Mortis

Question# 766

My question pertains to obvious signs of death, and specifically with respect to rigor mortis of the smaller muscles of the face.

I recognize the standard for obvious signs of death as documented by the RPPEO is "gross rigor mortis" ie stiffening of the limbs/body.

However, given that the onset of rigor to the muscles of the face occurs at about 2 hours post mortem is there any reason this cannot be used as an obvious sign of death?? Is it excluded due to the possibility of "instantaneous rigor" or an immediate post mortem "trismus" if you will?

If the timeline provided for a VSA patient is significant enough to suggest that rigor to the face may be present would beginning resuscitative efforts not be considered futile and project a false hope?

This is something that I have certainly seen many times, and I would be interested in the RPPEO's position on this.

Answer:

As soon as the heart stops, there’s a plethora of physiological processes at play within the body. Gravity takes over, and tissues and cells begin to die off. Depending on the type of cell, their death occurs at different rates of cessation of circulation. For example, cerebral cortex cells die very quickly, within a couple of minutes, while connective tissue and muscle cells generally take several hours.

At the time of death, ATP is no longer able to be resynthesized and is progressively destroyed. As a result of decreased ATP synthesis, the actin-myosin filaments begin to lock, and we start to see the process of post-mortem contraction of muscles – also known as rigor mortis.

Rigor mortis normally starts with generalized muscle flaccidity that’s usually followed by a period of partial or total rigidity which passes as decomposition appears (also known as secondary flaccidity). This is why patients that have been deceased for prolonged periods no longer have rigor mortis.

When it comes to the onset of rigor mortis, there are many factors that impact the rate of onset and progression.

For example, the ambient weather (temperature, humidity, air movement) will impact the onset time of rigor. If it’s hot outside, metabolism is faster, and rigor will occur quicker. The converse is also true for cold. The patient’s clothing or coverings at the time of death will also impact the rate of rigor. As will the patient’s body habitus (emaciated or obese).

The pre-death activity of the patient will also impact the rate of rigor. For example, if the patient was exercising, or running a marathon and collapsed at the finish line, rigor can rapidly occur.

Their underling medical history is also relevant. Just prior to their death, if they were septic, their metabolism is faster and thus tissue breakdown is also faster. If they just had a large preceding sympathetic response (i.e. cocaine use, ++ stress, etc.) rigor can occur quicker. If they have a neuromuscular issue (i.e. ALS), rigidity won’t be evident. Likewise, if they have baseline spasticity issues (i.e. cerebral palsy, stroke, etc.) you may rapidly see rigidity, but that’s not rigor mortis.

The ability to estimate time of death has been scientifically difficult to accurately determine, as we’ve seen, there are many factors that influence rigor. It’s important not to put a “rule” in place, but rather we need to take everything in it’s totality.

In an “ideal scenario”, if there’s no rigor yet, the patient hasn’t been deceased very long. Rigor is first detected in the face, generally in the first 1-4 hours since death. This is a good site to check for rigor, as in the absence of major pathologies, there’s very little that would prevent jaw movement. It’s postulated that rigor occurs first in the face due to the smaller muscles (vs the quads).

Over the next 4-6 hours, rigor will begin to set-in in the limbs. Over the next 6-12 hours, the strength of the rigor will increase, and it will remain static until decomposition sets in over the next 24-50 hours.

As discussed, we need to consider the totality of the information. If the clinical situation fits (unwitnessed arrest, cool skin, asystolic) and the patient has small joint rigor mortis, then the resuscitation is likely futile and there may be benefits to withholding resuscitation. The RPPEO would be supportive.

As a corollary, if the paramedic only considers small joint rigor, they run the risk of premature determination of futility.

Having said that, there are other considerations at play. As you mentioned, the BLS PCS has strict criteria in how it defines rigor mortis. If the paramedic deviates from this definition, they open themselves to risk. Thus, we encourage you to engage with your Service to determine their thoughts on deviations from the BLS PCS.

The safest way to avoid these risks is if there is uncertainty and not clear obvious death, err on the side of resuscitation. Paramedics can always patch early to a BHP in these types of circumstances.

If you’d like to learn more, please check out an elective CME podcast with the Regional Supervising Coroner for Eastern Ontario, Dr. Louise McNaughton-FIlion (https://criticallevels.ca/2020/07/08/episode7/)

References

BLS PCS - Deceased Patient Standard

https://criticallevels.ca/2020/07/08/episode7/

Published

25 January 2024

ALSPCS Version

5.2

Views

408

Please reference the MOST RECENT ALS PCS for updates and changes to these directives.