The method of determining the degree of utilization of oxygen by body tissues

 

(57) Abstract:

The invention relates to medicine, namely to methods of diagnosis and monitoring of disorders of the oxygen balance in the body. The method consists in determining the value of oxygen saturation of arterial and mixed venous blood with subsequent calculation of the coefficient of utilization of oxygen, with simultaneous measurement of oxygen saturation of arterial and mixed venous blood is performed by the method of reflective spectrophotometry, for which the catheter fiber optic sensors installed respectively at the same time in the femoral artery and pulmonary artery. The method improves the accuracy of diagnosis and to monitor the coefficient of utilization of oxygen by body tissues, which results in making timely correction of oxygen status.

The invention relates to medicine, namely anesthesiology and critical care medicine.

It is known that patients in critical conditions develop violations of the oxygen balance in the body, leading to dysfunction and damage to the systems, organs and cells of the body. Their severity depends on the nature and videoelement identify and correct correction resulting changes of the oxygen balance depends on the result of the treatment.

There is a method of measuring the percentage of oxygen saturation of the mixed venous blood [SvO2] by the method of reflective spectrophotometry. The study was conducted in vivo ["Intensive therapy", Per. s angl., M, GEOTAR Medicine, 1998, S. 118]. The method consists in the fact that the light through the catheter placed in the pulmonary artery, are sent directly into the bloodstream. Reflected from hemoglobin, it comes back. The catheter is connected to the photodetector, which measures the intensity of the reflected light beam. Using this method, you can monitor the level of oxygen saturation of the mixed venous blood [Birman H., Haq, A., Hew E., Aberman A. / Continous monitoring of mixed venous oxygen saturation in hemodinamically unstable patients. Chest 1984; No. 6; P. 753-756].

However, the task of this method is not part of the definition of the degree of utilization of oxygen by body tissues.

In addition, the method cannot be used to determine the degree of utilization of oxygen, because it provides a measurement of oxygen saturation only mixed venous blood, which does not reflect the degree of absorption of oxygen by the tissues. Thus, on the basis of changes in the oxygen saturation of the mixed venous blood is only possible to detect only the presence of narusheniiami they arose, and their severity, and it is impossible to calculate the degree of utilization of oxygen by body tissues.

As the closest analogue accepted method of determining the degree of utilization of oxygen by body tissues [Intensive care / Edited. Ed. C. D. Malysheva, M., Medicine, 2002, pp. 81-82], including the definition of saturation and oxygen tension in arterial and mixed venous blood by the method of micro-Astrup. For implementing the method disinfect the hands of the doctor and the skin of the patient at the site of the proposed puncture of the artery, and then produce a puncture artery syringe, in which a pre-typed 0.1 ml officinal solution of heparin or an appropriate amount of dry heparin. Is the fence 1.0 ml of blood. Collected in a syringe, the blood is introduced into the device working according to the method of micro-Astrup, which automatically, after a preliminary calibration counts in a sample of arterial blood oxygen tension and the degree of oxygen saturation. Similarly identifies these same indicators in a sample of mixed venous blood. From the moment of puncture of the vessel until the results of each analysis takes at least 5 minutes To obtain data about the dynamics of these indicators required repeat samples.

The disadvantage of this method is its complexity and the complexity. Requires constant re-fences blood, causing excessive trauma to the blood vessels and blood loss. At each blood sampling and subsequent research takes a lot of time, a loss which is undesirable and dangerous for these patients. Obtained using this method the results are not completely accurate. This is due to the need to add to each sample of heparin. In addition, there is a decrease of blood oxygen saturation during transport and analysis.

The objective of the invention is to provide a highly efficient and accurate method of determining the degree of utilization of oxygen by body tissues in real time.

The invention consists in that in the method of determining the degree of utilization of oxygen by body tissues, including determination of oxygen saturation of arterial and mixed venous blood, carry out simultaneous measurement of oxygen saturation of arterial and sensors installed respectively at the same time in the femoral artery and the pulmonary artery.

The use of the invention allows to obtain the following effect: using this method, you can carry out continuous monitoring of the level of saturation as arterial and mixed venous blood and the monitoring of the coefficient of utilization of oxygen by body tissues.

This gives you the opportunity to make timely correction of oxygen status. In a short time without additional trauma of vessels provides accurate results of the study. The procedure for observing the dynamics of the investigated parameters can be carried out for a long time.

The technical result is achieved due to the fact that they are carrying out simultaneous measurement of saturation of arterial and mixed venous blood oxygen by the method of reflective spectrophotometry. The authors first proposed to determine the saturation of arterial blood with oxygen by the method of reflective spectrophotometry and on the basis of simultaneous measurements of saturation of arterial and mixed venous blood oxygen by the method of reflective spectrophotometry to calculate the coefficient of utilization of oxygen by body tissues.

The authors assumed is, for example by transferring them in critical conditions this figure is reduced to 60-70%, up to 40%. Therefore, to measure this indicator, you can use devices intended to measure the saturation of mixed venous blood oxygen by the method of reflective spectrophotometry, operating in the range from 20 to 80%, because this measured value changes within the specified limits, as in norm and in pathology. In the scale of the instrument specified value from 0 to 100%.

For catheterization of the femoral artery, the authors make use of the catheter Opticath® designed to measure the saturation of mixed venous blood. The accuracy obtained with its use of parameters is tested by comparing them with the parameters obtained by the methods of micro-Astrup and kulonometrii device Lexo-O2-con (the latter method is currently considered the most accurate because it allows you to determine the oxygen content in the sample direct way). When comparing data obtained high correlation of the proposed method with the method of micro-Astrup (r2=0,94) and the method of kulonometrii (r2=0,97).

The method is as follows. Oxymatrine system before the introduction calibrated in vitro according to the instructions. Catheter Opticath® , the inner diameter. The patient also produce catheterization of the pulmonary artery catheter Swan-Gans fiber optic sensor. Both catheter connected to the photodetectors for measuring the intensity of the reflected beam of light, through which the catheter is directed directly into the bloodstream. On the screens of the devices are calculated oxygen saturation, respectively, arterial and mixed venous blood.

The degree of utilization of oxygen by body tissues is determined by the formula

KyO2=VO2/DO2·100%,

where Kuo2- coefficient of oxygen utilization, VO2- oxygen consumption, DO2- delivery of oxygen. Oxygen delivery is determined by the formula

DO2=CB· Sao2,

where CB is the cardiac output, and Sao2the oxygen content in the arterial blood.

Sao2=(1,3· Hb· SaO2)+(0,003· PaO2),

where Hb is the hemoglobin level of the blood, 1,3 - constant of Guerrera (1 gr. hemoglobin is able to attach 1.3 ml of oxygen), PaO2- the partial pressure (tension) of oxygen in arterial blood, 0,003 - solubility of oxygen in plasma.

The oxygen content in the venous blood (CvO2determine analogic CLASS="ptx2">While simplifying the formula to determine Kuo2the value of CB is reduced in the result of the division and receive

Kuo2=(Sao2-CvO2)/CvO2.

Given that in a single moment of time values CB and Hb is the same but the values of 0.003· RHO2and 0.003· PvO2can be neglected because of its small size and availability directly proportional relationship between the saturation of hemoglobin with oxygen and partial oxygen tension in the blood, we obtain the expression Kuo2(SaO2-SvO2)/SaO2.

Monitor the saturation of the arterial and mixed venous blood oxygen and coefficient of oxygen utilization. If necessary, make the measurement of cardiac output method thermodilution [Intensive care / Edited. Ed. C. D. Malysheva, M., Medicine, 2002, pp. 175-185].

The obtained value of the coefficient of oxygen utilization compared with normal values (0.2 and 0.3). Its deviation is outside the normal values allows to judge about the nature and severity of violations of the absorption of oxygen by the tissues and carry out the targeted correction. In addition, the simultaneous analysis of the values of the saturation of the arterial and mixed venous blood oxygen, the ratio of the ZMA. The assessment of these indicators and their relationship provides an opportunity to monitor the effect of all components of the treatment: parameters of the artificial lung ventilation, pharmacological agents that affect the value of the performance of the heart, the systemic and Central hemodynamics, peripheral hemodynamics, tissue metabolism and transfusion environments.

Example: Patient A., 37 years old, was admitted to the intensive care unit after severe concomitant injuries, which included severe traumatic brain injury - brain injury severe blunt trauma to the chest - multiple rib fractures on both sides, bilateral hemothorax, multiple fractures of the pelvis, traumatic shock 3 tbsp. After conducting antishock therapy, including artificial respiration, the patient's condition remained critical. Despite normalization of arterial pressure was maintained clinical signs of shock (pallor, oliguria, hypothermia, acrocyanosis). The patient made a catheterization of the femoral artery and pulmonary artery catheters equipped with fiber optic sensors, according to the method described above. When monitoring the coefficient of utilization of oxygen by tissues revealed assessed indicators of cardiac output -10 liters per min, saturation of arterial blood with oxygen and 90%, the saturation of mixed venous blood oxygen - 76%. Thus, the patient revealed the presence of peripheral shunting of blood. After transfusion of the patient with 800 ml of perftoran, 400 ml reopoligliukina and of heparin at a dose of 40 thousand UNITS per day increased coefficient of oxygen utilization by the tissues to 0.3, reducing the saturation of mixed venous blood to 63%. This was accompanied by the disappearance of clinical symptoms of shock.

The method of determining the degree of utilization of oxygen by body tissues, including determination of the oxygen saturation of arterial and mixed venous blood with subsequent calculation of the coefficient of utilization of oxygen, characterized in that the carry out simultaneous measurement of oxygen saturation of arterial and mixed venous blood by the method of reflective spectrophotometry, for which the catheter fiber optic sensors installed respectively at the same time in the femoral artery and the pulmonary artery.



 

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