Small animal blood gas analysis faces unique challenges, and every step may become a potential source of error. From adjusting the animal state in the early stage to interpreting data in the later stage, researchers require meticulous attention and rigorous operation.
The following is an introduction to the influencing factors of small animal blood gas analysis:
1、 Pre collection influencing factors
Animal status and stress response: Small animals are prone to stress due to unfamiliar environments and struggles in capture, leading to the release of catecholamines, which cause accelerated and deepened breathing, resulting in increased pH, increased PO ₂, and decreased PCO ₂; Fear may also cause brief breath holding, followed by intense breathing compensation, exacerbating fluctuations in indicators. Therefore, it is necessary to allow animals to adapt to the environment in advance and operate gently to reduce stress.
Sampling site selection: Common sites include the femoral artery, saphenous vein, etc. The blood composition of different sites is affected by local circulation. Low temperature at the extremities can lead to an increase in gas solubility in the blood, resulting in a pseudo decrease in PO ₂. Therefore, priority should be given to selecting the central blood vessel and ensuring fast and accurate puncture to avoid mixing of tissue fluid.
Anticoagulants and blood collection volume: Heparin sodium is a commonly used anticoagulant, but excessive use can dilute the blood and affect ion concentration; The single blood collection volume of small animals is limited. If the blood collection volume is insufficient, it may cause bubbles to enter the syringe and introduce external oxygen to contaminate the sample. Recommend using micro blood collection tubes and strictly preparing heparin coated empty needles in proportion.
2、 Factors influencing the concentration of mining
Air isolation and mixing: Contact with air can cause a virtual increase in oxygen partial pressure, and the escape of carbon dioxide can lead to an underestimation of actual PCO ₂. After blood collection, the bubbles should be immediately expelled and the needle sealed. The blood and anticoagulant should be evenly mixed to prevent the formation of micro disturbance areas due to blood clots.
Temperature control: Small animals have a large surface area to volume ratio, and their body temperature is easily affected by the environment. Low temperature inhibits enzyme activity, delays metabolic acid production rate, and increases gas solubility; High temperature accelerates cell oxygen consumption and leads to lactate accumulation. Suggest operating while keeping warm, and indicate real-time body temperature in the report.
3、 Influencing factors in analysis
Instrument adaptability: Directly using a human blood gas analyzer on small animals may result in errors, as the latter have significant differences in hematocrit and plasma protein content. It is necessary to use specialized animal reagent kits or enable "wild animal mode". Some devices allow customization of species parameters to improve accuracy.
Execution of quality control standards: It is crucial to conduct regular quality control tests at both high and low levels, especially when conducting cross species testing. Residual rinsing solution and electrode aging are more likely to amplify errors in non standardized processes, and strict pipeline flushing procedures must be followed before and after each measurement.
4、 Special considerations
Anesthesia effect superposition: Inhaled anesthetics inhibit the respiratory center, leading to inadequate ventilation, and the use of sedatives will further complicate the acid-base balance state. When interpreting the results, it is necessary to combine anesthesia records to comprehensively determine iatrogenic interference beyond the underlying disease.
Physiological rhythm fluctuations: The diurnal metabolic rate of experimental rodents can vary to a certain extent, and blood glucose and lactate levels naturally increase during the evening active period. When establishing a self comparison, the sampling period should be fixed, and long-term monitoring should ideally cover the entire biological cycle.