Blood pressure measurement experiments in conscious rats

Summary

The experimental method was obtained from the official website of the Fourth Military Medical University

Operation method

Blood pressure measurement experiments in conscious rats

Principle

When the rat tail was pressurized above systolic pressure, the pulse disappeared, when the pressure was reduced to systolic pressure, the pulse appeared, and when the pressure was continued to be reduced to diastolic pressure, the pulse returned to the level before the pressurization, and the instantaneous pressure at the time of this change in the pulse was measured by detecting this change in the pulse, which is the value of the blood pressure.

Materials and Instruments

Rats
Tail Artery Manometry Pulse Transducer Pressurized Tail Sleeve Tail Heater Animal Immobilization Device

Move

There are some minor differences in the operating procedures of different manufacturers and models of tail artery pressure measurement systems, but the basic operating procedures are the same.(1) Fixation and warming of rats: The whole body or the tail of the rat is used for warming. Fixation is usually done with a fixator made of plexiglass.(2) Determine the starting pulse level: Place the pressurized tail sleeve and pulse transducer in the appropriate position on the rat's tail.(3) Determination of blood pressure: inflate and pressurize with a rubber ball, so that the pressure in the pressurized tailpiece rises to the point where the pulse completely disappears, and then continue to pressurize for about 20 mmHg, and then slowly deflate and depressurize to the point where the pulse signal returns to the starting level, at which time systolic blood pressure, diastolic blood pressure, average arterial pressure, and heart rate can be read from the manometer or from the recording system. Generally three consecutive measurements are taken and the average value is taken as one measurement.

Caveat

(1) As the activity of the measured awake rats is restricted, braking stress can affect the accuracy of blood pressure, in order to reduce this effect, be sure to train the rats before the formal experiments to adapt to the environment and operation of the pressure measurement, in addition to the animal heat preservation can also make the animal quiet.(2) Temperature affects the diastole of the tail artery of rats, therefore, the tail of rats should be warmed appropriately during measurement. It is generally controlled at about 34℃. The duration is appropriate for 10min.(3) In practice, it is found that the width and position of the pressurized tail sleeve affects the measurement value, and the blood pressure value measured by the pressurized tail sleeve is too small to be high, while its width is too large to be the opposite. Therefore, the appropriate width of the pressurized tail set should be selected according to the weight of the animal. For animals weighing less than 150g, the pressurized tail sleeve should be 1.5cm, for those weighing 200g, 2.0cm, and for those weighing more than 300g, 2.5~2.8cm.The farther the pressurized tail set is from the root of the rat's tail, the lower the blood pressure value is, and it is preferable to place it at the root of the rat's tail. And each measurement must be placed in the same position.(4) The speed of decompression can affect the value of blood pressure measurement, so the deflation should be at a constant speed as far as possible.

Common Problems

There are several methods for determining blood pressure in conscious rats. They are categorized as invasive or noninvasive according to whether or not surgery is performed; they are categorized as direct or indirect according to the method of measurement, and the direct method is generally invasive.

The direct method is subdivided into the catheter method and the transducer buried in the abdominal cavity telemetry method, the former inserted into the rat's artery through the transducer and the recording system has a connection, the measurement of the activities of the awake rats are subject to certain restrictions, the latter inserted into the artery of the catheter, the transducer and the recording system does not have any connection, the measurement of the rats can be free to move.

The indirect method is generally non-invasive, and there are various kinds of indirect methods, the commonly used ones are rat tail volume manometry and rat tail artery pulse manometry and so on. Currently, the blood pressure of conscious rats is measured by the rat tail artery pulsatometry method. The following is a description of the rat tail artery pulse tonometry method.

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