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

Operation method

Experimental "dual infographic" display of heart pump function

Principle

The function of the heart is to pump blood, and its functional state can be described by heart rate, pressure, flow, power, etc. In the study of heart pump function, two different mechanical characteristics are often displayed on two planes to express the state of heart pump function. In the study of heart pumping function, the information of two different mechanical characteristics is often displayed on a two-dimensional plane to express the state of the heart pumping function, which is called the "double information map" method of heart pumping function, i.e., the Lissajous map display method. In this experiment, the left ventricular pressure (LVP) is recorded and the rate of change of intraventricular pressure (dP/dt) is obtained. The program automatically determines the cardiac cycle and then plots the cardiac force loop (P-dP/dt loop) and the contraction velocity loop using the "double infographic" display method. According to the LVP, dP/dt and P-dP/dt loops, the program calculates more than ten commonly used parameters, which can be used to judge the status of the left ventricular pumping function. Table 22-1 lists the major parameters of LV internal pressure analysis and their definitions. (Figure 1) shows a graphical illustration of how the main parameters of LV internal pressure analysis are calculated. Figure 1A shows the intraventricular pressure waveform for one cycle. Figure 1B shows the cardiac force loop. With dP/dt max and -dP/dt max as the boundaries, the cardiac force ring was divided into 4 parts, and the area of each block (L1 to L4) was obtained by the trapezoidal integration method or Simpson's integration method, respectively. Figure 1C shows the shortening velocity ring of the contractile component of the myocardium, and the magnitude of the Y-axis is obtained by the formula, in which k is the shortening velocity coefficient, and in rabbits, it is generally taken as 40. In the systole of the left ventricle, Vpm can be searched for; a straight line is made to intersect the Y-axis over the two points of dP/dt max and Vpm, and the intersection point of the line is Vmax.

Materials and Instruments

Rabbit
Mammalian Surgical Instruments Biological Signal Processing Systems Long Rubber Tubes

Move

1. Animals are weighed, anesthetized and intubated.

2. The right common carotid artery sheath was separated, and the right common carotid artery was freed about 0.5 to 2 cm in length, and two wires were threaded under this artery, one ligating the artery as close to the head end as possible; the other was reserved for fixing the cardiac catheter. The common artery was clamped with an arterial clip as close as possible to the cardiac end, and then a semiagonal incision was made with ophthalmic scissors in the arterial wall about 0.3 cm below the cephalic end of the ligature in preparation for insertion of a cardiac catheter.

3. The cardiac catheter is connected to the blood pressure transducer, and the cardiac catheter is filled with heparin solution to remove air bubbles from the cardiac catheter and the blood pressure transducer.

4. Insert the cardiac catheter into the rabbit by touching the left chest to the point where the apical fluctuation is most obvious, measuring the distance from this point to the right common carotid artery incision, and marking the distance on the plastic catheter in order to grasp the maximum depth of catheter advancement.

The cardiac catheter filled with heparin solution was inserted into the arterial lumen through the right common carotid artery incision up to the arterial clip, and a loose knot was tied in the backup wire. The left thumb and forefinger were then used to pinch the artery and the catheter inserted in it, and the right hand slowly released the arterial clip. If blood flowed out of the incision, the arterial clip could be pinched again and the loose knot could be tightened slightly, and then the arterial clip could be released. Immediately after releasing the arterial clip, slowly advance the catheter into the arterial lumen. When advancing the catheter, the direction and strength of advancement should be changed according to the direction of the artery to prevent the catheter from piercing the arterial wall and causing death of the animal.

When inserting the catheter, the speed should be as slow as possible, and the force should be moderate. When the resistance to advancement is large, it can be inserted by retreating and changing the direction. During intubation, the blood pressure waveform displayed on the computer screen should be closely watched to determine the position and status of the catheter.

According to the distance mark on the plastic catheter can estimate the distance of the catheter from the left ventricle, in general, when the tip of the catheter into the entrance of the aortic valve, there is a clear sense of resistance, shaking, at this time, a little force, suddenly produce a sense of breakthrough, that is, that the catheter has entered the left ventricle, the waveform displayed on the computer screen will be obvious changes (diastolic blood pressure down to 0 mmHg above and below).

The cardiac catheter is ligated with a spare wire and secured to tissue with less proximal mobility or to the tracheal tube.

5. Connect the experimental setup and run the experimental program.

6. Record the pressure curve of the left ventricle of the rabbit in the resting state, and obtain the parameters of the heart pump function as a precontrol.

7. Inject 0.2～0.5ml of 1:10 000 epinephrine solution into the ear marginal vein, and observe the changes of heart pump function.

8. Intravenous injection of 1:10 000 norepinephrine solution 0.2～0.5 ml, observe the changes of heart pump function.

9. Observe changes in cardiac pump function during long-tube asphyxia.

10. observe changes in cardiac pump function after intravenous administration of 0.3 ml of cardiac glycosides.

Caveat

1. The hardness and diameter of the ventricular catheter should be appropriate, and the tip should not be too sharp.

2. When inserting the catheter, the direction and strength of advancement should be changed according to the direction of the artery, and the force should be moderate to prevent the catheter from piercing the arterial wall and causing the death of the animal.

3. When inserting the catheter, the blood pressure waveform displayed on the computer screen should be closely watched to judge the position and status of the catheter.

4. Between the observation items, the animal should be allowed to rest for a sufficient period of time, and make a good pre- and post-check.

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