Let's learn the basis for red/pink lividity at cold temperature and link it with the concept of the Oxygen-hemoglobin dissociation curve

1. Physiology
behind red/pink lividity at
cold temperature

2. Introduction
• Did you ever wonder why bodies exposed at cold
temperature (drowned body, refrigerated body) have red/pink
postmortem hypostasis ?
• Well, lets go back to the basic physiology of oxyhemoglobin
dissociation curve for this.
• We all know that “CADET faces right”. You might relate it
better if you had done a march pass. If not, then no need to
worry. You might remember it as a mnemonics for factors
causing right shift of oxyhemoglobin dissociation curve.

3. Oxyhemoglobin dissociation curve

4. Oxyhemoglobin dissociation curve
So, the factors causing right shift of oxyhemoglobin
dissociation curve are
• Carbon dioxide (↑pCO2)
• Acidosis (↓pH)
• 2,3 Diphosphoglycerate (DPG)
• Exercise
• Temperature (↑)
Remember “Cadet faces right”.

5. Basis for red postmortem hypostasis at
cold temperature
• At higher temperature, there is rightward shift of
oxyhemoglobin dissociation curve.
 This indicates that hemoglobin has a decreased affinity
for oxygen, thus there is release of oxygen from
hemoglobin in the tissues.
• While lower temperature will cause a leftward shift in the
dissociation curve.
 This indicates increased hemoglobin affinity for oxygen
and decreased tendency to release oxygen.

6. Basis for red postmortem hypostasis at
cold temperature
• So, body exposed at cold temperature (like refrigerated body
or body drowned in cold water) causes left shift in
oxyhemoglobin dissociation curve.
 That means there is increased binding of hemoglobin
with oxygen which gives increased oxyhemoglobin
concentration in the blood.
 And remember the color of oxyhemoglobin which is red.
 So due to the increased oxyhemoglobin at low
temperature, there is red lividity of the body at cold
temperature.
But wait, how did the blood get oxygen even after death then ?
 Its actually a good question, isn’t it ?
 Actually this occurs by passive diffusion of oxygen
through the skin at cold temperature.

7. References
• https://www.statpearls.com/kb/viewarticle/26495
• https://pubmed.ncbi.nlm.nih.gov/21590457/