Radiation exposure of trainee anaesthetists - Wiley Online Library

Anaesthesia, 2006, 61, pages 9–14 doi:10.1111/j.1365-2044.2005.04419.x .....................................................................................................................................................................................................................

Radiation exposure of trainee anaesthetists S. Ismail,1 F. A. Khan,2 N. Sultan3 and M. Naqvi4 1 Assistant Professor, 2 Professor, 3 Resident, Department of Anaesthesia 4 Medical Physicist, Department of Radiology, Aga Khan University, Stadium Road, Karachi, Pakistan Summary

This prospective study was conducted to determine the level of radiation exposure of trainee anaesthetists working in urology, orthopaedics and radiology environments. Anaesthetists wore lithium fluoride thermoluminescent dosimeter (TLD) badges over a 6-month period. The position of badges was standardised at the collar site (TLD1) and at waist level (TLD2). Area specific dosimeters were used and exchanged between anaesthetists. Of a total of 723 procedures, anaesthetists were exposed to radiation in 33% of procedures in orthopaedics, 30% in urology and 39% in radiology. The mean (SD) exposure time to radiation per case was significantly greater in orthopaedics than in urology (9.2 (4) min vs. 4.2 (2) min). The radiation exposure per case was highest in radiology (19.2 (22) min). The net combined exposure over a 6-month period was 0.2177 mSv in urology, 0.4265 mSv in orthopaedics and 3.8457 mSv in radiology. The combined exposure was less than the 20 mSv recommended as the maximum exposure per year. Our data does not support the need for routine dosimetric monitoring of anaesthetists working in the above settings. . ......................................................................................................

Correspondence to: Dr Fauzia A. Khan E-mail: [email protected] Accepted: 26 July 2005

A number of studies have focused on the harmful effects of ionising radiation. These effects range from activation of HIV type I replications [1] and lens injuries [2] to carcinogenic effects, especially on the thyroid gland and heart [3, 4]. Cumulative data has suggested an increased incidence of these cancers in health care personnel exposed to radiation during routine work [3, 4]. McGowan et al. [5] estimated the occupational X-ray exposure of anaesthetists in an orthopaedic operating room and did not find significant exposure; however, the study period was limited to 1 month and data were extrapolated to calculate prolonged exposure. In current anaesthetic practice, anaesthetists work in several areas in addition to the operating room, which may have high radiation exposure. They are frequently involved in a number of interventional radiological procedures and are exposed to radiation whilst working in orthopaedic and urology operating rooms and in cardiac catheterisation rooms. Due to these expanded roles of anaesthetists it is important that further studies are conducted. With this in mind we designed a prospective study to determine the level of radiation exposure of trainee anaesthetists working in the high radiation risk environments of orthopaedic and urology operating 2005 Blackwell Publishing Ltd

rooms and radiology areas. A further aim was to determine whether the level of exposure fell within the limits of maximum permissible dose as published by the International Commission of Radiation Protection [6]. Methods

Our study setting was the urology and orthopaedics operating rooms and radiology departments of a university hospital. The study subjects were trainee anaesthetists providing care to patients requiring anaesthesia or monitored anaesthesia care in the above setting. The study duration was 6 months, from 1 January to 30 June 2004. Approval was obtained from the Ethical Review Committee of the University and informed written consent was obtained from all anaesthetists enrolled in the study. All those recruited in the study undertook routine protective measures as outlined in the policy documents of our institution. This included wearing a lead apron but no neck collar or eye protection. All anaesthetists working in the above three locations wore lithium fluoride thermoluminescent dosimeter (TLD) badges. Each study subject wore two TLD badges. 9

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S. Ismail et al. Radiation exposure of trainee anaesthetists Anaesthesia, 2006, 61, pages 9–14 . ....................................................................................................................................................................................................................

The positions of the badges was standardised. TLD 1 was worn externally at the collar outside the protective clothing and TLD2 was worn inside the protective lead apron at the waist level. The dosimeters used were area specific: TLD (O) were used in orthopaedics, TLD (U) in urology and TLD (R) in radiology. The dosimeters were exchanged between anaesthetists working in these rooms. The TLDs used for this study were LIF TLD 100 type (Pakland Corporation (PVT) Ltd, Karachi, Pakistan). The chips inside the batch were 0.125 · 0.12 · 0.035 inches in size and had a minimum detectable dose of 0.1 mSv. All anaesthetists wore protective lead aprons during exposure but no thyroid protection. The following data were collected: the total number of cases performed in each area, number of cases where radiation was used (both X-rays and fluoroscopy) and time duration of radiation exposure. Exposure to radiation time in seconds was read directly from the fluoroscopy machine (Shimadzu, Japan. Model WHA50S). The exposed crystals were sent to KIRAN (Karachi Institute of Radiotherapy and Nuclear Medicine) every 3 months for analysis. The data sheets were collected daily by a research fellow and checked by one of the investigators for completeness and accuracy. The time of exposure was also checked against the radiology department file. The anaesthetists did not leave the operating room during the procedures. Trainees in our institution typically spend 4 days a week in the operating room in 8 h shifts, i.e. 32 h per week or 128 h per month. Results

During the 6-month data collection period a total of 723 procedures were performed in the three specialties. In

all, 289 procedures were performed in orthopaedics, 306 in urology and 128 in the radiology department. Ionising radiation was used in 96 (33%) procedures in orthopaedics, 91 (30%) procedures in urology and 50 (39%) procedures in radiology. The number of cases where exposure occurred varied from month to month, the minimum being 13 in April (orthopaedics), 7 in May (urology) and 6 in February (radiology), and the maximum 18 in May (orthopaedics), 23 in January (urology) and 13 in March (radiology) (Table 1). Though the number of cases with radiation exposure was nearly the same in urology and orthopaedics, the mean (SD) duration of procedures was longer in orthopaedics (96.4 (65) min vs. 168.3 (79) min) and the mean exposure time to radiation per case was nearly double (4.2 (2.2) min vs. 9.2 (4.3) min). The mean duration of procedure was the least in the radiology department (75.0 (40) min) but the radiation exposure per case the highest (19.2 (22) min) compared to the other two specialties (Table 2). The dosimeter readings were reported quarterly following analysis as total exposure in mSv, for the six badges worn in the three specialties. Each specialty had a collar badge and a waist badge. Six sets of readings per quarter were obtained. The total background exposure was also reported in mSv and the net exposure in mSv that was calculated by subtracting the background from the total exposure. The net exposure per month in mSv was derived by simply dividing this figure by six. When the data was analysed and compared separately for each quarter, no difference was seen in the duration of radiation exposure per case in urology and orthopaedics. However, a significant difference was seen in radiology, with higher exposures during the second quarter (Table 3). The net exposure in mSv in each quarter is also reported.

Table 1 Radiation exposure of anaesthesia trainees working in Orthopaedic, Urology operating rooms and Radiology department.

Summary of data. Data given as number (SD). Month Specialty Urology Total no. of procedures No. of cases with radiation exposure Radiation exposure time; min Orthopaedics Total no. of procedures No. of cases with radiation exposure Radiation exposure time; min Radiology Total no. of procedures No. of cases with radiation exposure Radiation exposure time; min

10

Jan

Feb

March

April

May

June

Total

75 23 3.85

40 13 4.41

38 14 5.46

54 17 3.42

49 7 5.07

50 17 4.05

306 91 4.2 (2.2)

57 17 9.09

32 14 7.52

39 14 9.02

52 13 10.67

48 18 10.09

61 18 9.27

289 96 9.2 (4.3)

26 9 15.69

12 6 11.59

23 13 13.88

18 7 32.95

20 8 16.14

29 7 28.69

128 50 19.2 (22.0)

2005 Blackwell Publishing Ltd

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Anaesthesia, 2006, 61, pages 9–14 S. Ismail et al. Radiation exposure of trainee anaesthetists . ....................................................................................................................................................................................................................

Table 2 Mean (SD) duration of procedures and mean radiation

Table 4 Dosimeter readings. Radiation exposure in mSv.

exposure times over the study period. Quarter I

Quarter II

Specialty Specialty

No. of procedures Mean duration of procedures; min Mean duration of radiation exposure; min

Combined Combined exposure net exposure

Orthopaedics

Radiology

Urology

91 96.4 (65.4)*

96 168.3 (79.3)†

51† 75.0 (40.5)

Urology 1.426 1.214 1.121 0.818 4.579 Orthopaedics 1.754 1.312 0.807 0.807 3.680 Radiology 3.775 2.276 1.4515 0.7825 8.2850

4.2 (2.2)*§

9.2 (4.3)

19.2 (22.0)

Combined net exposure = total exposure – background exposure.

*Significant difference between urology and orthopaedics. †Significant difference between orthopaedics and radiology. §Significant difference between urology and radiology.

Table 3 Comparison of radiation exposure between different

specialties in the two quarterly time periods. First quarter Second quarter Jan – Mar Apr – Jun Urology Mean (SD) time of radiation 4.47 (1.9) exposure per case; min Cumulative dosimeter readings; mSv 2.640 Reported net exposure, dosimeter 0.0985 readings; mSv Orthopaedics Mean (SD) time of radiation 8.53 (4.7) exposure per case; min Cumulative dosimeter readings; mSv 3.066 Reported net exposure, dosimeter 0.4265 readings; mSv Radiology Mean (SD) time of radiation 14.2 (14.4) exposure per case; min Cumulative dosimeter readings mSv 6.051 Reported net exposure, dosimeter 3.3960 readings; mSv

3.96 (2.6) 1.939 0.1192

9.94 (3.7) 1.614 0.0000

25.4 (27.9)* 2.2340 0.4497

*Statistically significant difference between the two periods.

The combined net exposure in the three specialties is given in Table 4. Higher exposure was seen in the collar badges in all three areas. The combined net exposure over 6 months in the three specialties was 0.2177 mSv in urology, 0.4265 mSv in orthopaedics and 3.8457 mSv in radiology. This equates to a monthly mean (SD) net exposure of 0.0362 mSv (3.62 mrem) in urology, 0.0710 mSv (7.10 mrem) in orthopaedics and 0.6409 mSv (64.09 mrem) in radiology (10 mSv = 1 rem). Discussion

Ionising radiation is defined as high energy electromagnetic waves (X-ray and gamma rays) and particulate rays 2005 Blackwell Publishing Ltd

Collar Waist Collar Waist

0.2177 0.4265 3.8457

that dissociate substances in their path into ions [7]. Free radicals are creasted and molecules ionised in tissue [8], leading to tissue damage. Ionising radiation includes the X-rays emitting from X-ray and fluoroscopy devices. Radiation exposure can cause direct damage to tissue, e.g. erythema, or may induce cancerous and genetic changes [6]. Genetic risks have been studied in animals and changes such as autosomal and x-link changes and chromosomal alterations have been well documented in mice [9, 10]. Estimates of genetic risks have been extrapolated to humans but there is no definite human data. The only available human data is from second generation survivors of Hiroshima and Nagasaki who are followed up every 4 years. Other exposed populations such as survivors of treatment for cervical cancer and radiation workers exposed in UK and Russia many years ago have also been studied [11, 12]. There are limitations in extrapolating these data from one population to another [6]. The organs that are most sensitive to the effects of ionising radiation are the gonads, bone marrow, lungs, colon and stomach. In addition, in cases of pregnant workers there is a risk of genetic effects and malformation. The risk of higher incidence of female papillary thyroid cancer from occupational and medical low level radiation exposure has been established in a group of dentists and dental assistants [1]. There have been case reports of lens injuries in radiologists [13] and ionising radiation has been hypothesised to activate the HIV 1 virus replication or gene expression [5]. In addition, evidence of a risk of radiation induced breast cancer has been studied by Doody et al. [14]. In view of the above dangers, several international regulatory bodies have produced recommendations to limit the exposure of individuals to radiation. The International Commission on Radiological Protection (ICPR) was founded in 1928. It is an international committee that works with the help of four standing multidisciplinary committees. The annual occupational exposure allowed by ICPR in its 1990 guidelines was 20 mSv limited to 20 mSv per year over 5 years. These recommendations are similar to the 1993 recommendations produced by the National Council of Radi11

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ation Protection and Measurement (NCRP) of United States which gives the annual allowable occupational exposure as 10–20 mSv limited to 50 mSv per year [6]. The nuclear regulatory commission (NRC) in USA also sets the standards and regulations for protection against occupational exposure. From the 1 April 1996 the allowable annual dose is 5 rem (5000 mrem) for total body (with 3 rem permitted within a 13-week period) and 15 000 rem for the lens of the eye [15]. The roentgen is the amount of radiation required to produce a certain measurable physical effect. It was originally defined as the amount of X-ray radiation required to ionise a volume of air but the definition now includes ionisation produced by X-rays and gamma rays [14]. The NRC also provides guidelines for exposure control methods and record keeping. The risk of radiation exposure to anaesthetists has decreased over the years due to improvements in radiographic equipment and better radiation monitoring and protection methods. However, advances in diagnostic and interventional radiology now involve anaesthetists to a greater extent. One of the earliest articles on the damaging effects of radiation exposure in anaesthetists was published in 1958 by Kincaid [16]. That article discussed the nature of radiation and its biological effects, sources of radiation for occupational exposure and practical suggestion for minimising the exposure. Subsequent studies by Henderson et al. [17] compared the radiation exposure of anaesthetists working in the general operating room with the exposure of those working in the cardiac catheterisation laboratory. They found that the operating room anaesthetists were exposed to < 10 mrem per month whereas those working in catheterisation labs were exposed to 20–180 mrem per month [6]. They recommended routine monitoring of radiation in anaesthetists working in cardiac catheterisation laboratories. Otto & Davidson studied the exposure of nurse anaesthetists during specific ureteroscopic fluoroscopy procedures in urology operating rooms [15]. They found the exposure greater than the recommended limits especially in the area of the thyroid but not for the lens. In another study [18] the exposure of anaesthetists during percutaneous nephrolithotomy and calculi extraction was comparable to that of the radiologist and greater than that of the urologist, whereas Keenan [19] found the exposure to be safe in surgeons, anaesthetists, radiologists and patients. Studies done in other specialties have produced mixed results. In one USA centre the exposure of the trauma surgeon in a level 1 trauma centre was thought to be below the safe limits [3], whereas high exposure was noted in a study performed in gastroenterologists during ERCP [20]. Exposure in orthopaedic trainees was found 12

to be well below the recommended level [21] but there was a high risk of exposure amongst cardiologists performing radiofrequency ablation procedures [22]. The majority of these studies have studied the exposure over a relatively short time period of 1–2 months, except for Otto & Davidson [15], whose study duration was similar to ours. Their study, however, focused only on exposure in urological operating rooms. In our study the average duration of radiation exposure of anaesthetic trainees working in the environment of urology, orthopaedics and radiology departments varied from month to month (range 35.5–181.6 min). The average exposure to radiation was in 30% (urology), 33% (orthopaedics) and 39% (radiology) of patients anaesthetised. The combined net exposure over a 6-month period in the three specialties, urology, orthopaedics and radiology, was 0.2177 mSv, 0.4265 mSv and 3.8457 mSv, respectively. When extrapolated to 1 year, this was much less than the 20 mSv recommended as the maximum exposure per year even when the results from the three specialties were combined together. The net exposure per month for an anaesthetist working in either urology, orthopaedics or radiology in our institution was 0.0198 mSv in urology, 0.0710 in orthopaedics and 0.6409 in radiology. The radiation exposure was higher at the collar site where anaesthetists do not usually wear protective thyroid shields. Our study has certain limitations; the protection from external radiation depends on three factors at the time of exposure: • the distance of the anaesthetists from the X-ray source; • the shielding by wearing lead aprons, neck collars and protective goggles; • the duration of fluoroscopy. We did not standardise the distance of anaesthetist from the radiation source as done in the study by Otto & Davidson [15]. However, our results reflect a more realistic exposure. Distancing from the patient may not always be possible when anaesthesia is being administered to young children and to sicker patients. Standard protection measures of wearing lead aprons were observed in our study but wearing of thyroid collars and eye goggles is not a routine even in developed countries. The situation may be worse in many centres in the developing world [23]. The duration of fluoroscopy has been found to be the most important factor in exposure [24]. This variable is not within the control of the anaesthetist. It has been recommended that orthopaedic surgeons in particular should be familiar with the technique of closed reduction and instrumentation to reduce the duration of fluoroscopy [15]. A novice surgeon may use more fluoroscopy time. The mix of cases will also affect the results. Our 2005 Blackwell Publishing Ltd

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Anaesthesia, 2006, 61, pages 9–14 S. Ismail et al. Radiation exposure of trainee anaesthetists . ....................................................................................................................................................................................................................

study included a mix of cases but they may differ between institutions and even from month to month in the same institution. There is therefore a need to quantify this exposure on a real time basis and for prolonged periods in a variety of situations. Although the current evidence suggests that radiation exposure is less than that recommended, this should not lead to complacency. Radiation induced cancer is now estimated to be three times greater than a decade ago [6]. In addition, film badges have been shown to underestimate the effective dose by half [25]. There is a need to monitor anaesthesia personnel routinely, especially in high risk environments outside the operating room. We also recommend that radiation safety should form a part of the formal education of anaesthetic and surgical residency programmes. Anaesthesia trainees should rotate through various high risk specialties so that radiation exposure is distributed equally amongst as many trainees as possible. Rotations with high exposure such as radiology and urology should be combined with low risk areas. In conclusion, data from our study support earlier work that suggested that radiation exposure of anaesthetists working in the operating room does not exceed the recommended dose limits set by the International Commission on Radiological Protection. Acknowledgements

The authors wish to thank Mr Salman Sabir for help with statistical analysis and Mr Lawrence Anthony for the secretarial support. This work was supported by a Seed Money Research Grant from the Aga Khan University. References 1 Ron E. Ionizing radiation and cancer risk; evidence from epidemiology. Radiation Research 1998; 150 (Suppl.): S 30– 41. 2 Faure E. X-ray induced secretions of cellular factor(s) that enhance(s) HIV-I promoter transcription in various non irradiated transfected cell lines. Cellular and Molecular Biology 1998; 44: 1275–92. 3 Wingren G, Hallguist A, Hardell L. Diagnostic X-ray exposure and female papillary thyroid cancer; a pooled analysis of two Swedish studies. European Journal of Cancer Prevention 1997; 6: 550–6. 4 Sont WN, Zielinski JM, Ashmore JP, et al. First analysis of cancer incidence and occupational radiation exposure based on the ‘National Dose Registry of Canada’. American Journal of Epidemiology 2001; 153: 309–18 (Abstract). 5 McGowan C, Heaton B, Stephenson RN. Occupational X ray exposure of anaesthetists. British Journal of Anaesthesia 1996; 76: 868–9.


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