Chlorhexidine is widely used all over the world in many different preparations. In Denmark chlorhexidine is the standard skin disinfectant used before surgery or invasive procedures and it is widely used in the general population in mouthwash or for disinfection of minor scratches etc. The potential for developing allergy to chlorhexidine is thus great, especially in surgical patients. We have identified four patients with serious allergic reactions in connection with surgery and general anaesthesia, who on subsequent skin testing tested positive for chlorhexidine. Symptoms appeared 20-40 min into the operation and all four patients required treatment with adrenaline. All four patients had a history of minor symptoms like rashes or faints in connection with previous surgery/invasive procedures. Allergy to chlorhexidine may be more prevalent in surgical patients and cases may have been overlooked due to the nature of reactions and lack of suspicion towards this substance.
Our preliminary results appear to differ in two ways from results usually found in this field. Firstly, only one patient has tested positive for a NMBD and secondly, we have had four patients with anaphylactic shock who have tested positive for chlorhexidine. Possible reasons for these differences are discussed.
Perivascular axillary blockade was performed on 90 patients with the aid of a catheter technique. The patients were randomly allocated to receive either 40, 50 or 60 ml of 1% mepivacaine with adrenaline 1:200,000. Blood concentrations of mepivacaine were measured up to 90 min after injection in seven, eight and ten of the patients from the three groups. Sensory and motor blockade was evaluated 20, 30 and 40 min after injection. All groups showed the same temporal development of the blockade, i.e. improval of the blockade during the period from 20 to 40 min after injection, but no difference was found in the sensory or motor blockade between the three groups. However, a further analysis of the incomplete blockades showed a better quality of the sensory blockade in the groups given 50 and 60 ml than in the group given 40 ml. None of the 90 patients showed any signs of systemic toxic reactions. The mean peak values of blood concentrations were 0.5-1.0 microgram/ml higher in the groups given 50 ml and 60 ml than in the group given 40 ml. On the basis of the present and two previous investigations on the dose response in perivascular axillary blockade, a dose of 50 ml 1% mepivacaine with adrenaline or another equivalent drug with vasoconstrictor is recommended.
An informed guess is not a reliable way of determining the cause of a supposed allergic reaction during anaesthesia and may put a significant number of patients at unnecessary risk. Some patients may be labelled with a wrong allergy, leading to unnecessary warnings against harmless substances, and some patients may be put at risk of subsequent re-exposure to the real allergen. Patients with suspected allergic reactions during anaesthesia should be referred for investigation in specialist centres whenever possible.
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