Basis for red/pink lividity at cold temperature

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 C arbon dioxide (↑pCO 2 ) A cidosis (↓pH) 2,3 D iphosphoglycerate (DPG ) E xercise T emperature ( ↑ ) 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/