1. Rinsing
MP6 – Dialysis fluid 2 – not ultrafiltered
All lines and stations are rinsed with RO water of conductivity MP7 – RO fluid inlet of the machine.
<
10 µS/cm over 20 minutes.
From each MP 100 ml fluid was sampled in sterile and
endotoxin free bottles for either bacteriological or endotoxin
tests. 1-5 litres of fluid was wasted before sampling. Disinfec-
2. Disinfection process
The goal is to establish and maintain equal concentration of tion of tapes and connectors was done by heat or alcohol 70%
the disinfectant in all RO water and concentrate lines. Loss of (Hansen connectors receive a routine disinfection treatment
concentrate begins when disinfectant is wasted slowly through after each dialysis). Storage and transport was done at < 4 °C.
the bicarbonate lines and stations.
Culture media used was Trypton Glucose Extract Agar (TGEA).
Temperature for cultivation was 22 °C ± 2 °C general / 37 °C
only dialysis fluid. Evaluation was carried out after 3 and
•
•
•
The waste valve of the RO is closed.
The dialysis stations are switched off.
RO water and peracetic acid 3.5% are mixed stepwise over 7 days. Endotoxin tests were performed by GEL-Clott or
the soft water tank and circled in closed loop through RO turbimetric method.
and RO fluid system.
•
The bicarbonate delivery system is filled with the disin-
fectant.
Results
Study time
28 months
59
The dialysis stations are switched on. The disinfectant moves System disinfection processes
slowly through the bicarbonate delivery system and through the Time spent per disinfection –
dialysis stations, while the disinfectant continues to circle in a
closed loop through the RO and RO fluid system.
mean value (MV)
Disinfectant used peracetic acid – MV 4.12 litres
Conductivity 30 minutes past start
4.2 hours
Total contact time, temperature and concentration were:
of disinfection time – MV
316 µS/cm (225-442)
RO fluid system
Bicarbonate loop
Dialysis stations
Temperature
> 60 min
> 45 min
> 30 min
14–17 °C (measured)
0.15–0.22% (calculated)
Bacteriological tests (59) from MP1 – 6 on the 11th day (MV
min 5 / max 13) following the disinfection process. 7 test runs
were done during the observation period. The MV was 0.2
CFU/ml. In 4 of 59 tests 1-3 CFU/ml were detected.
Concentration
Endotoxin tests (26) from MP 1–6 on the 11th day (MV)
following the disinfection process. 5 test runs were done during
3. Rinsing
All lines and stations are rinsed with RO water of conductivity the observation period.
10 µS/cm over 60 minutes.
<
Measure points Bacteria CFU/ml Endotoxin test
1. RO fluid at outlet
4. Testing for disinfectant
The testing at all tapes and end valves is done per checklist, a
special indicator paper for peracetic acid is used.
0 (n = 5) 3 (n = 1) < 0.05 (< 0.05-0.005)
2. RO fluid end of loop
0
(n = 5) 2 (n = 1) < 0.325 (< 0.325-0.008)
5
. Disinfection of the bicarbonate production unit
3. Bicarbonate concentrate hub
0 (n = 6)
Bicarbonate Mixing System (the RO supply line and distribu-
< 0.10 (< 0.10-0.25)
tion system is already included in the chemical disinfection) is 4. Bicarbonate tap in the loop
disinfected by Hot Water Disinfection
Contact temperature and time: > 90 °C for 15 minutes
Total disinfection time: 1.40 hours
0 (n = 5) 1 (n = 1) < 0.10 (< 0.10-0.25)
5. Dialysis fluid 1 not ultrafiltered
0 (n = 6)
6. Dialysis fluid 2 not ultrafiltered
(n = 5) 1 (n = 1) < 0.25 (< 0.25-0.005)
< 0.25 (< 0.25-0,005)
Change of Ultrafilter: every 14 days
0
7. RO fluid inlet of the machine
Microbial quality
not tested
< 0.125 (only 1 test)
The monitoring of microbial quality was performed in general
every 3 months under practice conditions. The sampling, stor-
Discussion
age, transport and testing were mostly performed according to The study was conducted under certain conditions. It could
the ‘Guidelines of German Taskforce for applied hygiene’ (5).
Measurement points (MP) were:
MP1 – RO fluid at outlet
be questioned whether the results are compromised by the
methods used not always being clean. During the observation
period, we did not sample the total number of probes as
planned for bacterial and endotoxin tests.
MP2 – RO fluid end of loop
MP3 – Bicarbonate concentrate hub
MP4 – Bicarbonate tap in the loop
MP5 – Dialysis fluid 1 – not ultrafiltered
We chose to disinfect every 14 days according to the study
from Ebben et al (4). The conditions of the Ebben study were
different to ours; nevertheless, the expected result was not
132
EDTNA|ERCA JOURNAL 2002 XXVIII 3