JPH0554784B2 - - Google Patents

Description

[Detailed description of the invention]

(Industrial Application Field) The present invention relates to a method for preserving a sensor for measuring gas partial pressure of a body fluid such as blood. (Prior Art) Carbon dioxide partial pressure, oxygen partial pressure, and hydrogen ion concentration in blood are collectively referred to as blood gases, and are extremely important as measures of the respiratory and metabolic functions of living organisms. Conventionally, blood gas measurements have been carried out using a blood gas analyzer after blood sampling. However, this method has problems such as the time it takes from blood collection to completion of measurement, the impossibility of continuous measurement, and the loss of blood from the patient. In order to solve these problems, the present inventors disclosed a so-called infusion type blood gas measuring device in Japanese Patent Laid-Open No. 155240/1983. In this device, a gas partial pressure sensor is installed in a catheter inserted into a blood vessel or a measurement chamber connected to the catheter, the catheter or measurement chamber and an infusion reservoir are connected with a conduit, and a gas partial pressure sensor is installed in the catheter or measurement chamber. In addition to supplying an infusion containing a gas component at a certain concentration, blood is appropriately sucked into the catheter or/and the measurement chamber by the means for sucking the infusion in the catheter or the measurement chamber, and at least the detection part of the gas partial pressure sensor is A device configured to bring the blood into contact with the blood. The device has the following advantages: Since the sensor alternately contacts infusion fluid and blood, it can be calibrated using infusion fluid, and even if the sensor drifts, accurate measurements can be made.
Also, because the contact time with blood is short, blood clots are less likely to occur. Since the sensor is located outside the blood vessel, it does not need to be extremely small. Therefore, it is easy to incorporate multiple sensors that measure several components simultaneously. In order to use the infusion as a calibrator, no special sterilization of the calibrator is required. A blood pressure (arterial central pressure) measurement line is available. FIG. 1 shows an example of the device. The sensor 6 is housed in a cell 8, which has two openings, one of which is connected to an infusion bag 12 through an infusion line 10 and a roller pump 11. The other opening is connected to an indwelling needle 4 placed in the blood vessel 1. The sensitive part of the sensor is located near the latter opening, and can be brought into contact with the infusion fluid and blood by rotating the roller pump 11 in the forward or reverse direction. It is desirable that the sensors used in such devices be able to measure not only a single component but several components simultaneously. When using this device, even if it is relatively mild, it will invade the living body, so it is necessary to obtain corresponding information, and since the sensor is located outside the body, the size of the sensor may be slightly larger. That's because there isn't. In this case, oxygen, carbon dioxide gas partial pressure, and PH are important as one combination of items to be measured. These are generally called blood gas analyses, and only by integrating them can the respiratory state and acid-base balance of the whole body be analyzed. As a multi-sensor for infusion gas monitoring that can measure these three components, the present inventors filed a patent application in 1983-
In No. 225033, we proposed a sensor as shown in Figure 2. This is FETPH sensor 21, Clark type oxygen sensor 2
2 and a FET carbon dioxide gas sensor 23 are embedded in a rectangular prism-shaped resin 9, leaving a sensitive part at the tip. Then, the resin is fixed to the connector 14, and the cell 8 and the connector 14 are fixed with screws. Such multi-sensors must be stored in a sterile state for their intended use, and among these sensors, the oxygen sensor, PH sensor, reference electrode, and carbon dioxide gas sensor all have internal liquid and must be stored in a moist state. You need to save it in . (Problem to be solved by the invention) Conventionally, as these storage solutions, PH sensors were
They were stored separately in a solution suitable for storing individual sensors, such as a phosphate buffer solution containing NaCl, a sodium bicarbonate aqueous solution for carbon dioxide sensors, and physiological saline for oxygen sensors, but there is no example of a multi-sensor being created. , it is necessary to develop a storage solution suitable for any sensor. The conditions for this storage solution are: 1. The sensor will not be damaged even after autoclave sterilization. 2.No sensor drift occurs even when transferred from storage solution to measurement solution. 3. Can be stored stably for a long period of time. 4.Harmless to human body. Conditions such as allowing small amounts of contamination with blood must be met.
The purpose of the present invention is to find a method for preserving multi-sensors that satisfies these conditions. (Means for solving the problem) The PH reference electrode, carbon dioxide sensor, and oxygen sensor all contain internal liquid, so if they are stored in a dry state, electrical communication will be cut off and measurements will be impossible.
Among these, in the reference electrode, the internal liquid and the measuring liquid are connected by a liquid junction, but in other sensors, the internal liquid and the measuring liquid are separated by a gas permeable membrane, so no electrolyte movement occurs. Therefore, we investigated the cause of sensor damage when using conventional storage solutions, and found that this is mainly caused by the difference in osmotic pressure between the storage solution and the internal solution. It was also found that the main cause of drift was that when the storage solution was transferred to the measurement solution, water moved due to osmotic pressure and the concentration of the internal solution changed. Therefore, it is necessary to equalize the osmotic pressures of the storage solution, the sensor internal solution, and the measurement solution. Since the object to be measured is mainly a living body, its salt concentration is approximately equal to the concentration of physiological saline, 0.154N. Therefore, the salt concentration of the internal fluid is preferably approximately equal to the physiological saline concentration. In fact, it was confirmed that if the salt concentration of the internal solution was between 0.10 and 0.25N, no significant sensor drift or damage would occur. Regarding the reference electrode, since ions move between the internal solution and the measurement solution, it is preferable that the concentration of chlorine ions in the storage solution is equal to that of chlorine ions in blood. Actual blood chloride ion concentration is 0.096~
Although it is 0.107N, in reality, if it is between 0.05 and 0.25N, no significant drift will be observed during measurement. However, in this case, if the salt concentrations of the internal solution and the storage solution are different,
The difference in osmotic pressure causes movement of water vapor, and the internal solution tries to have the same osmotic pressure as the storage solution. Therefore, the osmotic pressures of the internal solution and storage solution become equal. The salt concentration of the internal solution is 0.1 to 0.25N, so when the chlorine concentration of the storage solution is 0.05N to 0.1N, the balance between the internal solution and osmotic pressure cannot be maintained, so the difference is compensated for by sulfates, nitrates, carbonates, etc. of salt, the total salt concentration is 0.1N ~
It is necessary to adjust it to 0.25N. Further investigation revealed that the unexplained decrease in sensitivity of carbon dioxide sensors can be suppressed by adding carbonate ions to the storage solution.
Although the mechanism of this effect is unknown, this effect
It appears by adding carbonate ions of 0.01N (5mM) or more. However, adding too many carbonate ions will affect the aforementioned osmotic pressure, and will also lead to leakage of the storage solution due to carbon dioxide pressure during autoclaving, so it is not good to have a carbonate ion concentration that is too high. The concentration of these ions is
The total salt concentration must be within the range mentioned above. In this way, by adjusting the osmotic pressure and chloride ion concentration of the storage solution, measurement solution, and sensor internal solution, it has become possible to provide a multi-gas sensor that does not drift or break even when measurements are performed immediately after taking it out of the sterilized package. (Example) Experiments were conducted using the sensors shown in FIGS. 2 and 3. FIG. 3 is an enlarged view of the sensor section in FIG. 2,
FETPH sensor 21, reference electrode 24, Clark type oxygen sensor 22, and FET carbon dioxide sensor 23
is incorporated. 22 to 24 have crosslinked hydrophilic gels 33 to 34, respectively, into which the internal liquid is absorbed. Of these individual sensors
The PH sensor and carbon dioxide sensor were measured using the methods described in Japanese Patent Application Laid-open No. 58-204363 and Japanese Utility Model Application No. 59-196212. Moreover, the oxygen sensor was obtained by the following method.
First, a cathode was prepared by embedding a 0.1 mm platinum wire into a nylon-11 catheter with an outer diameter of 0.5 mm and an inner diameter of 0.3 mm using epoxy resin. Separately, a 0.2 mm silver wire surrounded by crosslinked PVA hollow fibers with an outer diameter of 0.7 mm and an inner diameter of 0.4 mm was used as an anode. After aligning both in the axial direction and applying polyhydroxyethyl methacrylate (PHEMA) to the exposed platinum part at the tip, the inside of the PVA hollow fiber and PHEMA were replaced with the internal solution, and finally covered with a silicon tube, which is a gas permeable membrane. Obtain an oxygen sensor. This sensor was assembled into a cell as shown in Figure 2, and after filling the inside of the cell with a storage solution, the two openings of the cell were plugged with locks, and the changes in the performance of the sensor after autoclave steam sterilization and storage were measured. Measurements were made by changing the internal solution and storage solution. The results are shown in Table 1. These results show that the preservation method of the present invention (combining an internal solution with a specific salt concentration and a preservation solution) causes less damage to the sensor and less drift. (Effects of the Invention) As described above, according to the present invention, a multi-gas sensor can be stably stored in a sterile state and can be used immediately after opening.

【table】

【table】

【table】 [Brief explanation of the drawing]

FIG. 1 is a schematic diagram of an infusion type multi-monitor, FIG. 2 is a sectional view of a sensor stored by the method of the present invention, and FIG. 3 is an enlarged sectional view of the sensor section. In the figure, 1... blood vessel, 4... indwelling needle, 6...
...Sensor, 8...Cell, 9...Resin, 10...Infusion line, 11...Roller pump, 12...Infusion bag, 14...Connector, 21...FET
PH sensor, 22... Clark type oxygen sensor, 23
...FET carbon dioxide sensor, 24... Reference electrode,
32...Hydrophilic gel, 33...Hydrophilic gel, 34
...Hydrophilic gel.

Claims (1)

[Claims] 1. When storing a multi-sensor that has at least two sensors selected from the group consisting of an oxygen sensor, a carbon dioxide sensor, and a PH sensor, and is equipped with a comparison electrode, other than the PH sensor The salt concentration of the internal solution of the sensor and reference electrode was set to 0.10.
~0.25N, the chlorine ion concentration of the storage solution is 0.05~0.25N, and the total concentration of salt components is 0.10~0.25N.
A method of preserving multi-sensors characterized by setting the pressure to 0.25N. 2. Storage according to claim 1, wherein when storing a multi-sensor in which one of the sensors constituting the multi-sensor is a carbon dioxide gas sensor, the storage solution further contains 0.01N or more of CO ₃ ^-- ions. Law.