Latex Aeroallergen Pollution in the Operating Theatre: Should Latex Allergic Patients Be Scheduled First?

Editor—Latex allergy is a major problem in the operating theatre, although its incidence has been reduced by implementation of primary and secondary prevention measures.1Mertes P.M. Ebo D.G. Garcez T. et al.Comparative epidemiology of suspected perioperative hypersensitivity reactions.Br J Anaesth. 2019; 123: 16-28Abstract Full Text Full Text PDF PubMed Scopus (46) Google Scholar,2Harper N.J.N. Cook T.M. Garcez T. et al.Anaesthesia, surgery, and life-threatening allergic reactions: epidemiology and clinical features of perioperative anaphylaxis in the 6th National Audit Project (NAP6).Br J Anaesth. 2018; 121: 159-171Abstract Full Text Full Text PDF PubMed Scopus (170) Google Scholar One of these secondary prevention measures consists in scheduling latex-allergic patients first on the operating list,3Volcheck G.W. Hepner D.L. Identification and management of perioperative anaphylaxis.J Allergy Clin Immunol Pract. 2019; 7: 2134-2142Abstract Full Text Full Text PDF PubMed Scopus (24) Google Scholar although this can lead to organisational problems when the risk has not been correctly identified or in case of emergency surgery. This recommendation is based on the assumption that latex aeroallergen levels are lower at the start of the day. However, the effectiveness of this measure has never been confirmed by studying these levels. We performed airborne latex allergen measurements in two operating theatres with different air filtration levels: an International Organization for Standardization (ISO) 5 operating theatre used for thoracic surgery (133.4 m3; 30 air changes h−1) and an ISO 7 operating theatre used for urological surgery (151.2 m3; 16 air changes h−1). Operating theatre air samples were taken from a polytetrafluoroethylene (PTFE) membrane using a cassette (Merck Millipore, Molsheim, France) connected to a pump (Fisher Scientific, Illkirch, France). The PTFE membrane was placed at the patient's head position for 10 working days. The air was sampled for 2 h at different times: at the start of the operating schedule (7 a.m. to 9 a.m.), between 11 a.m. and 1 p.m., and at the end of the day between 3 p.m. and 5 p.m. Additional samples were taken before the opening of the operating theatre (5 a.m. to 7 a.m.) in the ISO 7 operating theatre. Airborne latex allergen concentrations (Hevea brasiliensis [Hev] b1, Hev b3, Hev b5, and Hev b6.02) were measured using a monoclonal assay (Fitkit®; Icosagen, Tartu, Estonia). During the study period, surgery was regularly performed in both operating theatres with a median opening of 9 [6–13] and 7 [2–8] new non-powdered gloves in the first period and 2 [0–5] and 2 [0–7] non-powdered gloves in the last period, in the ISO5 and ISO7 operating theatres, respectively. The levels of Hev b5 and Hev b6.02 were consistently below the detection range in all samples. The levels of Hev b1 and Hev b3 according to filtration level and time of day are shown in Figure 1. In the ISO 5 operating theatre, the median [inter-quartile range] levels of Hev b1 and Hev b3 were 0 [0–29] and 20 [18–24] ng m−3, respectively, and remained constant between the three periods (P=0.35 and 0.76, respectively). In the ISO 7 operating theatre, the level of Hev b1 increased significantly between the three periods from 75 [0–246] ng m−3 in the first period to 208 [0–348] ng m−3 in the last period (P=0.04). Before the start of the operating programme, Hev b1 was undetectable in seven of 10 of the samples and its median level was 0 [0–134] ng m−3 (detectable values: 92, 255, and 439 ng m−3). The concentrations of all latex allergens in latex non-powdered gloves from the same lot as those used in the ISO 7 operating theatre during the sampling period were highly variable with median levels of Hev b1, Hev b3, Hev b5, and Hev b6.02 of 0 [0–265], 228 [117–301], 320 [0–390], and 311 [253–317] ng g−1, respectively. Our study showed that despite a high level of air filtration and the standard use of non-powdered gloves, the major latex aeroallergens were still detectable regardless of the level of air filtration. Considering that the median latex allergen level was below the detection threshold before the opening of the operating theatre on most days, placing latex-allergic patients first on the operating list remains the safest strategy. The level of latex aeroallergens remained constant in the ISO 5 operating theatre and was well below the level of latex aeroallergens observed in the ISO 7 operating theatre, which increased progressively over the day. Three samples were above the detection threshold before the start of the list. As the ventilation in this operating theatre switches from a standby mode at night to a regular mode during the day during this period, turbulence may have resuspended latex particles. The amount of latex allergens needed to cause a reaction is controversial with only limited data available. Most studies have focused on the level of air pollution. Baur and colleagues4Baur X. Chen Z. Allmers H. Can a threshold limit value for natural rubber latex airborne allergens be defined?.J Allergy Clin Immunol. 1998; 101: 24-27Abstract Full Text Full Text PDF PubMed Scopus (120) Google Scholar reported that 0.6 ng m−3 of latex allergens was sufficient to cause clinical signs of latex allergy, but that a latex level of 39–311 ng m−3 was generally required to cause asthma or anaphylaxis.4Baur X. Chen Z. Allmers H. Can a threshold limit value for natural rubber latex airborne allergens be defined?.J Allergy Clin Immunol. 1998; 101: 24-27Abstract Full Text Full Text PDF PubMed Scopus (120) Google Scholar, 5Swanson M.C. Bubak M.E. Hunt L.W. Yunginger J.W. Warner M.A. Reed C.E. Quantification of occupational latex aeroallergens in a medical center.J Allergy Clin Immunol. 1994; 94: 445-451Abstract Full Text Full Text PDF PubMed Scopus (209) Google Scholar, 6Kurtz K.M. Hamilton R.G. Schaefer J.A. Adkinson Jr., N.F. A hooded exposure chamber method for semiquantitative latex aeroallergen challenge.J Allergy Clin Immunol. 2001; 107: 178-184Abstract Full Text PDF PubMed Scopus (34) Google Scholar The methodology used to define these thresholds is highly questionable, and the lack of established data makes it difficult to correctly assess the risk of airborne latex-related allergic reactions. The level of latex aeroallergens observed in the ISO 5 operating theatre could be below this trigger level, allowing patients to be scheduled at any time of day. The wide variability of our results is partly explained by the ballistic trajectory of latex particles, and therefore depends on the positions of the gloves and pump inlet. Hev b5 and Hev b6.02 are mainly present on the inner surface of latex gloves, which may explain why they were not found in our samples.7Peixinho C. Tavares P. Tomaz M.R. Taborda-Barata L. Tomaz C. Differential expression of allergens on the internal and external surfaces of latex surgical gloves.Allergol Immunopathol (Madr). 2006; 34: 206-211Crossref PubMed Scopus (13) Google Scholar Hev b3 was only found in the ISO 5 operating theatre. Hev b3 has a higher molecular weight and is more negatively charged than Hev b1.8Berthelot K. Lecomte S. Estevez Y. Peruch F. Hevea brasiliensis REF (Hev b 1) and SRPP (Hev b 3): an overview on rubber particle proteins.Biochimie. 2014; 106: 1-9Crossref PubMed Scopus (77) Google Scholar Thus, Hev b3 is less likely to be dispersed far from the source. As the ISO 5 operating theatre was used for thoracic surgery, the surgeon was closer to the patient's chest, and therefore much closer to the filter used to capture the latex particles. No other source of latex was identified in either operating theatre. The distribution of allergens in the gloves used in the ISO 7 operating theatre was variable, even when these gloves came from the same lot. The gloves in the ISO 5 operating theatre were another brand, and we were unable to analyse these gloves. Nevertheless, as reported by Peixinho and colleagues,9Peixinho C. Tavares-Ratado P. Tomas M.R. Taborda-Barata L. Tomaz C.T. Latex allergy: new insights to explain different sensitization profiles in different risk groups.Br J Dermatol. 2008; 159: 132-136Crossref PubMed Scopus (31) Google Scholar most of the sterile latex surgical gloves had the same allergen content profile as the one we observed. In conclusion, latex-allergic patients should still be placed first on the operating list whenever possible. If an emergency procedure needs to be performed on a latex-allergic patient, our results showed that the ISO 5 operating theatre offers a low and constant level of latex aeroallergens that allows surgery to be performed with minimal allergic risk, regardless of time of day. The authors declare that they have no conflicts of interest.