To the Editor:—
We would like to report an unusual observation of green breast milk after propofol administration. A 33-yr old woman underwent emergency laparoscopic removal of an ectopic pregnancy under general anesthesia with 474 mg propofol as a target-controlled infusion, fentanyl, remifentanil, mivacurium, and metamizole.
Preoperative medication included dimenhydrinate, metamizole, and piritramide, with additional metamizole, butylscopolamine, and metoclopramide postoperatively.
About 8 h after surgery, the patient reported that the first breast milk pumped showed a bluish green color, which changed to green during the course of the day, and which resolved 48 h postoperatively. Urine color was not monitored. Metabolites of phenoles like propofol (2, 6-diisopropylphenol) are a known cause of green urine.1The exact chromophoric compound responsible is not known. As propofol is also excreted into the breast milk,2it was suspected as a cause in this case.
A breast milk sample obtained 30 h after the initial color change was evaluated for possible propofol conjugated metabolite content. The sample was acid hydrolyzed, extracted with ethyl acetate, and analyzed by gas chromatography/mass spectroscopy, but there was no significant difference in the free propofol concentration (24 ng/ml) as compared with an unhydrolyzed sample, and thus no evidence for conjugated propofol metabolites.3Metoclopramide, which can cause green urine,4could not be detected in the breast milk sample. Green breast milk is described after iron intake. Also, low casein and lactose content might cause green breast milk.5
In conclusion, a still unknown chromophoric substance, presumably derived from propofol, caused a green coloration of the breast milk in this patient. Risks to a nursed infant are unknown. The mechanism of propofol coloration of breast milk remains unknown.
*University Hospital Erlangen, Erlangen, Germany. email@example.com