Acta anaesth. scand. 1978, 22, 33-39
Operating Room Nurses’ Psychomotor and Driving Skills after Occupational Exposure to Halothane and Nitrous Oxide K. KORTTILA, P. PFAFFLI, M. LINNOILA, E. BLOMGREN, H. HANNINEN and S. HAKKINEN Department of Anaesthesia and Department of Pharmacology, University of Helsinki, and Institute of Occupational Health, Helsinki, Finland
Concentrations of halothane and nitrous oxide were assayed by gas chromatography throughout a working day in three operating theatres and in the end-tidal air of 19 nurses 15 and 60 min after leaving the theatres. Perceptual, psychomotor and driving skills were measured in these nurses and in 11 younger nurses working in the wards of the same hospital. A complicated psychomotor test battery and a driving simulator were used. End-tidal air concentrations of halothane and nitrous oxide were positively correlated with the exposure level of these gases in the operating theatres. Some of the operating room nurses had greater amounts of halothane in their end-tidal air (average 15 to 10 ppm) than student volunteers 4.5 h after 3.5 min of general anaesthesia with a combination of halothanenitrous-oxide-oxygen (10 ppm halothane). These volunteers had worse psychomotor and driving performances when measured than controls who had not been anaesthetized. N o correlations were found between the concentrations of halothane or nitrous oxide in end-tidal air and psychomotor or driving performance. Despite their higher age and exposure to the operating room environment, the driving skills of the operating room nurses were similar to those of the ward nurses. T h e results suggest that tolerance to anaesthetic gases develops among operating room personnel. No impairment of driving skills can be expected after daily exposure to halothane and nitrous oxide among long-term employees in operating theatres.
Received 7 April, accepted f o r publication 3 June 1977
BRUCE et al. (1974) showed a significant decrease in performance by healthy volunteers in tests of perception, cognition and motor skills after 4 hours of exposure to trace amounts of nitrous oxide and halothane. GAMBERALE & SVENSSON (1974) did not, however, notice any major impairment in reaction time or perceptual speed of anaesthetic nurses after exposure to halothane and nitrous oxide during their daily work. In our recent study (KORTTILA et al. 1977), the performance of young healthy subjects remained distinctly worse than in unanaesthetized controls for 5 h after 3.5 min of anaesthesia with halothane or enflurane combined with nitrous oxide and oxygen. In connection with measurements of con-
centrations of waste anaesthetic gases in operating room air in the Clinics a t Helsinki University Central Hospital in the spring of 1975, we decided to measure the end-tidal and blood concentrations of halothane and nitrous oxide in operating room nurses after their working shifts. We wanted to compare these concentrations with those found in healthy subjects after brief halothane anaesthesia. Simultaneously, we tested the psychomotor and driving skills of those nurses who had a valid driver’s licence to see whether chronic exposure to anaesthetic gases has any major effects on performance. The tests have been shown to be sensitive to the adverse effects of short halothane anaesthesia (KORTTILA et al. 1977).
34
K . KORTTILA ET AL.
MATERIAL AND METHODS Subjects and operating room Three operating rooms in the Helsinki University Central Hospital were studied. Halothane was used in two of these rooms, whereas in the third, nitrous oxide was the only anaesthetic gas used (Table 1). Two slightly different techniques were used for administration of halothane. I n room 11, children were intubated during anaesthesia, whereas in room I11 children were anaesthetized with a face mask. In both rooms the anaesthesias were induced with thiopentone and maintained with halothane (0.5 to 1.5 volume % in 4 l/min nitrous oxide and 2 l/min oxygen), which was administered through a semiopen system (Reise). In the room where intubation was used, the connection between the suction catheter for waste gases and the end of Reise’s exhaust tube was tight in order to prevent gases leaking into the air. We tested 19 operating room nurses from the three rooms. They had worked an average of 9 years in operating rooms. The distribution of nurses according to room and type of anaesthesia used is shown in Table
I . Eleven nurses from the wards of the same clinics were studied for reference. Each of the 30 subjects tested held a valid driver’s licence and drove weekly, or a t least once a month. Concentrnt ions of anaesthetics Ambient air was sampled throughout a working day in consecutive samples of 0.5- to 1-hour periods. The air was blown into plastic laminated bags using a battery-driven pump in the vicinity of the breathing zone of the anaesthetic and instrument nurses, a t a distance of approximately 1 and 3 m, respectively, from the exhaust valve of the anaesthetic machine. The sampling was started a t the beginning of the induction of the first anaesthesia and it was stopped 15 min after the end of the last anaesthesia. Blood and end-tidal air (corresponding to alveolar air) samples were taken from the subjects before the beginning of the drive with the simulator and after it; i.e. approximately 15 and 60 min after leaving the operating rooms. End-tidal air samples were blown into bags, and samples of venous blood were collected into heparinized glass tubes.
Table 1 Concentration of halothane and nitrous oxide during an average working day in three operating rooms as well as blood and end-tidal air concentrations of nurses working in the rooms measured 15 and 60 min after leaving the opcrating room.
Anaesthesia and operating room
Conc. in room air Halothane NzO (Range PPm) Mean
-
No. of nurses
Blood conc. (a) 15 Min (b) 60 Min
End-tidal conc. (a) 15 Min (b) 60 Min
Halothane NzO (Range pg/IOO ml) Mean
Halothane NzO (Range PPm) Mean
-
I
1 Semiclosed system (Engstrom) . Nz0-02-relaxant-analgetic combination anaesthesia. Intubated patients. Ventilation: room air changes 10 times in an hour
I1 Semiopen system (Reise) Intubated children. Halothanc-NZO-02- anaesthesia. Water tap suction of waste gases; no room ventilation 111 Semiopen system (Reise) Halothane-Nz0-02- anaesthesia with face mask. Water tap suction; no room ventilation
0-0.22 470-1200 * 72 1
2455550 -397
0.54-8.1 2.02
6
14.3-43.7 1001190 4 33.4 265
* Only the first two samples contained
halothane.
t Only one sample contained halothane. 2 Six samples contained
9
halothane.
_-
(a) 0-0.853 0.29
0.42-6.1
(b) 0-0.703 0.28
-0-01 2.79 t
(a) 0.6-6.1 2.19 (b) 0.1-2.6 1.25
-
-
_
2.72 0.21-8.4
.
0.02
t
0.1-3.0 0.03-13.5 1.11 0.1-3.0 1.08
2.31 0.02-4.5 0.79
--
0.2-36.0 - 0.42-9.4 4.03 15.10
(a) 2.8-5.0 4.08 Ib) . , 2.0-3.5 2.98
0.42-3.0 2.23
0.12-29 -10.80
0.8-9.4 3.37 0.e5.1 2 .oo
-
0.5-2.8 1.02 0.24.8 1.41
0.9-3.2 1.75 1.1-2.0 1.46
OCCUPATIONAL EXPOSURE TO ANAESTHETIC CASES
35
Concentrations of halothane and nitrous oxide were assayed in the room air, as well as in the blood and endtidal air samples of the nurses, using gas chromatography with the head-space technique of PFAFFLI et al. (1972).
accident situations and performance errors (neglected instructions, driving off the road, and collisions). We have previously described the apparatus and the testing procedure in detail (LINNOILA& HAKKINEN 1974, KORTTILA et al. 1975).
Testing of psychamtor and driuing skills Each subject was tested on perceptual and psychomotor tests and on a driving simulator between 3.45 and 4.30 p.m. after a usual working day. Test equipment was located next to the hospital, and therefore testing could start within 15 rnin after work. The driving simulator was used first, after which (i.e. approximately 45 rnin later) perceptual and psychomotor tests were carried out. The operating mom nurses worked in the same operating rooms in which the concentrations of anaesthetics were measured, and on the test day they followed an operating schedule similar to the one used on the day that air concentration measurements were conducted.
StatistiGs
Because the group of operating room nurses was older than the group of ward nurses, and because age influenced many test parameters recorded, a statistical comparison of the groups was not valid. The effect of age on the parameters measured was assessed with a correlation analysis, and the effect of anaesthetic gases on psychomotor performance was studied with a partial correlation analysis between the concentration of the gasa and psychomotor skills after exclusion of the effect of age on the parameters measured.
RESULTS Perceptual speed. The Bourdon-Wiersma test of perceptual speed was used according to a modification by HANNINEN (HANNINEN1971, KORTTILA 1976a). The number of lines completed in 8 min and the number of errors when drawing lines through groups of four dots were recorded. Time variation in completing a row was also assessed.
Concentration of anaesthetics
Because the concentrations of the gases were similar at both sampling places (i.e. in front of both anaesthetic and instrument nurses), the results from different sampling places were not handled separately. Santa Ana &xtm$ test. Hand coordination was measThe concentration of anaesthetics varied 1971). The measured using a peg board (HKNNINEN greatly in the three operating rooms, accordtest results were recorded as the number of pegs turned in 30 s; the test was repeated twice with the ing to the anaesthetic technique, as shown in right hand, twice with the left, and once with both Table 1. The administration of the NO,-O, hands at the same time. combination anaesthesia with a respirator resulted in higher (range 470 to 1,200 ppm) Tupping speed. Holding a stopwatch-like counter in room air concentrations of nitrous oxide than one hand, the subjects were asked to tap with one finger as many times as possible in 10 s. The mean in operating rooms where water-tap suction number of taps for four 10-s periods was calculated for apparatuses were used (range 245 to 550 ppm both the right and the left hand. and 100 to 490 ppm) When halothane anaesthesias were given Reaction skills. Reaction skills were measured with with a face mask, room air concentrations of two choice-reaction tests (KORTTILA et al. 1977). halothane were distinctly higher (mean 33.4 Fimt the subjects had to react to 25 consecutive light stimuli from two different lights (program I). Then ppm) than those in the room where children they had to react to 25 stimuli from two different lights were intubated during anaesthesias and or two sounds (program 11). In both programs there where a tight join was used between the was a special light to which the subjects were told not suction catheter and the exhaust hole for lo react. With both techniques, reaction times were waste gases (2.0 ppm) (Table 1). counted as the cumulative totals, and the inaccuracy of Blood and alveolar air concentrations of responses was recorded as the incorrect responses. halothane correlated positively with the Simulated driving. Driving skills were measured on exposure to halothane in the operating & HAKa driving simulator, Sim-L-car (LINNOILA theatres (Table 1). Subjects coming from the KINEN 1974). The main features recorded during an average of 35 min of driving in densely populated and theatre with the high concentration of halorural areas where brake reaction times in simulated thane had distinctly higher end-tidal air
.
36
K. KORTTILA ET AL.
operating room nurses were older than the ward nurses (P
Operating Room Nurses’ Psychomotor and Driving Skills after Occupational Exposure to Halothane and Nitrous Oxide K. KORTTILA, P. PFAFFLI, M. LINNOILA, E. BLOMGREN, H. HANNINEN and S. HAKKINEN Department of Anaesthesia and Department of Pharmacology, University of Helsinki, and Institute of Occupational Health, Helsinki, Finland
Concentrations of halothane and nitrous oxide were assayed by gas chromatography throughout a working day in three operating theatres and in the end-tidal air of 19 nurses 15 and 60 min after leaving the theatres. Perceptual, psychomotor and driving skills were measured in these nurses and in 11 younger nurses working in the wards of the same hospital. A complicated psychomotor test battery and a driving simulator were used. End-tidal air concentrations of halothane and nitrous oxide were positively correlated with the exposure level of these gases in the operating theatres. Some of the operating room nurses had greater amounts of halothane in their end-tidal air (average 15 to 10 ppm) than student volunteers 4.5 h after 3.5 min of general anaesthesia with a combination of halothanenitrous-oxide-oxygen (10 ppm halothane). These volunteers had worse psychomotor and driving performances when measured than controls who had not been anaesthetized. N o correlations were found between the concentrations of halothane or nitrous oxide in end-tidal air and psychomotor or driving performance. Despite their higher age and exposure to the operating room environment, the driving skills of the operating room nurses were similar to those of the ward nurses. T h e results suggest that tolerance to anaesthetic gases develops among operating room personnel. No impairment of driving skills can be expected after daily exposure to halothane and nitrous oxide among long-term employees in operating theatres.
Received 7 April, accepted f o r publication 3 June 1977
BRUCE et al. (1974) showed a significant decrease in performance by healthy volunteers in tests of perception, cognition and motor skills after 4 hours of exposure to trace amounts of nitrous oxide and halothane. GAMBERALE & SVENSSON (1974) did not, however, notice any major impairment in reaction time or perceptual speed of anaesthetic nurses after exposure to halothane and nitrous oxide during their daily work. In our recent study (KORTTILA et al. 1977), the performance of young healthy subjects remained distinctly worse than in unanaesthetized controls for 5 h after 3.5 min of anaesthesia with halothane or enflurane combined with nitrous oxide and oxygen. In connection with measurements of con-
centrations of waste anaesthetic gases in operating room air in the Clinics a t Helsinki University Central Hospital in the spring of 1975, we decided to measure the end-tidal and blood concentrations of halothane and nitrous oxide in operating room nurses after their working shifts. We wanted to compare these concentrations with those found in healthy subjects after brief halothane anaesthesia. Simultaneously, we tested the psychomotor and driving skills of those nurses who had a valid driver’s licence to see whether chronic exposure to anaesthetic gases has any major effects on performance. The tests have been shown to be sensitive to the adverse effects of short halothane anaesthesia (KORTTILA et al. 1977).
34
K . KORTTILA ET AL.
MATERIAL AND METHODS Subjects and operating room Three operating rooms in the Helsinki University Central Hospital were studied. Halothane was used in two of these rooms, whereas in the third, nitrous oxide was the only anaesthetic gas used (Table 1). Two slightly different techniques were used for administration of halothane. I n room 11, children were intubated during anaesthesia, whereas in room I11 children were anaesthetized with a face mask. In both rooms the anaesthesias were induced with thiopentone and maintained with halothane (0.5 to 1.5 volume % in 4 l/min nitrous oxide and 2 l/min oxygen), which was administered through a semiopen system (Reise). In the room where intubation was used, the connection between the suction catheter for waste gases and the end of Reise’s exhaust tube was tight in order to prevent gases leaking into the air. We tested 19 operating room nurses from the three rooms. They had worked an average of 9 years in operating rooms. The distribution of nurses according to room and type of anaesthesia used is shown in Table
I . Eleven nurses from the wards of the same clinics were studied for reference. Each of the 30 subjects tested held a valid driver’s licence and drove weekly, or a t least once a month. Concentrnt ions of anaesthetics Ambient air was sampled throughout a working day in consecutive samples of 0.5- to 1-hour periods. The air was blown into plastic laminated bags using a battery-driven pump in the vicinity of the breathing zone of the anaesthetic and instrument nurses, a t a distance of approximately 1 and 3 m, respectively, from the exhaust valve of the anaesthetic machine. The sampling was started a t the beginning of the induction of the first anaesthesia and it was stopped 15 min after the end of the last anaesthesia. Blood and end-tidal air (corresponding to alveolar air) samples were taken from the subjects before the beginning of the drive with the simulator and after it; i.e. approximately 15 and 60 min after leaving the operating rooms. End-tidal air samples were blown into bags, and samples of venous blood were collected into heparinized glass tubes.
Table 1 Concentration of halothane and nitrous oxide during an average working day in three operating rooms as well as blood and end-tidal air concentrations of nurses working in the rooms measured 15 and 60 min after leaving the opcrating room.
Anaesthesia and operating room
Conc. in room air Halothane NzO (Range PPm) Mean
-
No. of nurses
Blood conc. (a) 15 Min (b) 60 Min
End-tidal conc. (a) 15 Min (b) 60 Min
Halothane NzO (Range pg/IOO ml) Mean
Halothane NzO (Range PPm) Mean
-
I
1 Semiclosed system (Engstrom) . Nz0-02-relaxant-analgetic combination anaesthesia. Intubated patients. Ventilation: room air changes 10 times in an hour
I1 Semiopen system (Reise) Intubated children. Halothanc-NZO-02- anaesthesia. Water tap suction of waste gases; no room ventilation 111 Semiopen system (Reise) Halothane-Nz0-02- anaesthesia with face mask. Water tap suction; no room ventilation
0-0.22 470-1200 * 72 1
2455550 -397
0.54-8.1 2.02
6
14.3-43.7 1001190 4 33.4 265
* Only the first two samples contained
halothane.
t Only one sample contained halothane. 2 Six samples contained
9
halothane.
_-
(a) 0-0.853 0.29
0.42-6.1
(b) 0-0.703 0.28
-0-01 2.79 t
(a) 0.6-6.1 2.19 (b) 0.1-2.6 1.25
-
-
_
2.72 0.21-8.4
.
0.02
t
0.1-3.0 0.03-13.5 1.11 0.1-3.0 1.08
2.31 0.02-4.5 0.79
--
0.2-36.0 - 0.42-9.4 4.03 15.10
(a) 2.8-5.0 4.08 Ib) . , 2.0-3.5 2.98
0.42-3.0 2.23
0.12-29 -10.80
0.8-9.4 3.37 0.e5.1 2 .oo
-
0.5-2.8 1.02 0.24.8 1.41
0.9-3.2 1.75 1.1-2.0 1.46
OCCUPATIONAL EXPOSURE TO ANAESTHETIC CASES
35
Concentrations of halothane and nitrous oxide were assayed in the room air, as well as in the blood and endtidal air samples of the nurses, using gas chromatography with the head-space technique of PFAFFLI et al. (1972).
accident situations and performance errors (neglected instructions, driving off the road, and collisions). We have previously described the apparatus and the testing procedure in detail (LINNOILA& HAKKINEN 1974, KORTTILA et al. 1975).
Testing of psychamtor and driuing skills Each subject was tested on perceptual and psychomotor tests and on a driving simulator between 3.45 and 4.30 p.m. after a usual working day. Test equipment was located next to the hospital, and therefore testing could start within 15 rnin after work. The driving simulator was used first, after which (i.e. approximately 45 rnin later) perceptual and psychomotor tests were carried out. The operating mom nurses worked in the same operating rooms in which the concentrations of anaesthetics were measured, and on the test day they followed an operating schedule similar to the one used on the day that air concentration measurements were conducted.
StatistiGs
Because the group of operating room nurses was older than the group of ward nurses, and because age influenced many test parameters recorded, a statistical comparison of the groups was not valid. The effect of age on the parameters measured was assessed with a correlation analysis, and the effect of anaesthetic gases on psychomotor performance was studied with a partial correlation analysis between the concentration of the gasa and psychomotor skills after exclusion of the effect of age on the parameters measured.
RESULTS Perceptual speed. The Bourdon-Wiersma test of perceptual speed was used according to a modification by HANNINEN (HANNINEN1971, KORTTILA 1976a). The number of lines completed in 8 min and the number of errors when drawing lines through groups of four dots were recorded. Time variation in completing a row was also assessed.
Concentration of anaesthetics
Because the concentrations of the gases were similar at both sampling places (i.e. in front of both anaesthetic and instrument nurses), the results from different sampling places were not handled separately. Santa Ana &xtm$ test. Hand coordination was measThe concentration of anaesthetics varied 1971). The measured using a peg board (HKNNINEN greatly in the three operating rooms, accordtest results were recorded as the number of pegs turned in 30 s; the test was repeated twice with the ing to the anaesthetic technique, as shown in right hand, twice with the left, and once with both Table 1. The administration of the NO,-O, hands at the same time. combination anaesthesia with a respirator resulted in higher (range 470 to 1,200 ppm) Tupping speed. Holding a stopwatch-like counter in room air concentrations of nitrous oxide than one hand, the subjects were asked to tap with one finger as many times as possible in 10 s. The mean in operating rooms where water-tap suction number of taps for four 10-s periods was calculated for apparatuses were used (range 245 to 550 ppm both the right and the left hand. and 100 to 490 ppm) When halothane anaesthesias were given Reaction skills. Reaction skills were measured with with a face mask, room air concentrations of two choice-reaction tests (KORTTILA et al. 1977). halothane were distinctly higher (mean 33.4 Fimt the subjects had to react to 25 consecutive light stimuli from two different lights (program I). Then ppm) than those in the room where children they had to react to 25 stimuli from two different lights were intubated during anaesthesias and or two sounds (program 11). In both programs there where a tight join was used between the was a special light to which the subjects were told not suction catheter and the exhaust hole for lo react. With both techniques, reaction times were waste gases (2.0 ppm) (Table 1). counted as the cumulative totals, and the inaccuracy of Blood and alveolar air concentrations of responses was recorded as the incorrect responses. halothane correlated positively with the Simulated driving. Driving skills were measured on exposure to halothane in the operating & HAKa driving simulator, Sim-L-car (LINNOILA theatres (Table 1). Subjects coming from the KINEN 1974). The main features recorded during an average of 35 min of driving in densely populated and theatre with the high concentration of halorural areas where brake reaction times in simulated thane had distinctly higher end-tidal air
.
36
K. KORTTILA ET AL.
operating room nurses were older than the ward nurses (P
