Unstable hemoglobin caused by the 42 Phe to Ser mutation of the  β chain of hemoglobin. 

This mutation causes:

-         instability of the heme (Hb precipitates in red blood cells and generates Heinz bodies) with chronic hemolysis: subjaundice, vesicular lithiasis, splenomegaly

-         a  660nm absorption spectrum similar to that of the normal deoxyHb; this distorts pulse oximetry measurements.

Anesthetic implications: 

complete blood count; falsely low pulse oximetry values with small response to FiO2 increase; if in doubt, make a measurement of blood gases to measure the PaO2.

References : 

-          Lang SA, Chang PC, Laxdal VA, Huisman THJ. 
Haemoglobin Hammersmith precludes monitoring with conventional pulse oximetry. 
Can J Anaesth 1994; 41: 965-8.

Updated: March 2019