Experiments on the compensatory role of humoral alterations in acute blood loss in rabbits
Experiments on the compensatory role of humoral alterations in acute blood loss in rabbits
This experiment is from the official website of Zhejiang University Fine Courses
Operation method
Experiments on the compensatory role of humoral alterations in acute blood loss in rabbits
Principle
Under physiological conditions, blood pressure in humans and other mammals is relatively stable, and this relative stability is achieved through the regulation of neurological and humoral factors, in which the carotid sinus-aortic arch pressure-sensing reflex plays an important role. This reflex can both lower the blood pressure when the blood pressure rises and raise the blood pressure when the blood pressure falls. The afferent nerves of the reflex are the aortic nerve and the sinus nerve. In rabbits, the aortic nerve is an independent nerve, also known as the decompression nerve, which is easy to separate and observe its role. In humans, dogs and other animals, the aortic nerve is mixed with the vagus nerve and cannot be separated. Reflex efferent nerves are cardiac sympathetic nerves, cardiac vagus nerves and sympathetic constrictor fibers, cardiac sympathetic nerve excitation, its endings release norepinephrine, norepinephrine binds to the b receptor on the membrane of the myocardial cell, causing a positive time-varying force-varying conduction effect of the heart, cardiac vagal excitation, the endings of the cardiac vagus nerve releases acetylcholine, acetylcholine and the myocardial cell membrane of the M receptor binds to, causing negative cardiac time-varying force-varying conduction effect. Time-varying force-varying conduction, sympathetic vasoconstrictor fiber excitation, its endings release norepinephrine, norepinephrine and vascular smooth muscle cell membrane of the a receptor binding, causing resistance vasoconstriction. The organism has the ability to compensate for a certain amount of acute blood loss. Acute blood loss decreases arterial blood pressure and decreases blood volume, and in the instant of blood loss, resistance vessels, volume vessels constrict, and cardiac activity is increased to maintain arterial blood pressure through pressure-sensing reflexes and volume-sensing reflexes. Acute blood loss causes excitation of the sympathetic-adrenomedullary system, leading to a massive secretion of catecholamines and marked vasoconstriction. The venous system is a volume vessel, holding 60% to 70% of the total blood volume. Contraction of the veins can rapidly and transiently increase the volume of return blood to the heart. Microarterioles and precapillary sphincters are more sensitive to catecholamines than microvenules, resulting in a more pronounced elevation of precapillary resistance than posterior resistance, inadequate capillary perfusion, and a decrease in hydrostatic pressure, which allows for the entry of tissue fluid into the vasculature and an increase in circulating blood volume. Increased production and secretion of antidiuretic hormone, angiotensin II, and corticosteroid are also involved in the compensation of acute blood loss. In this experiment, a hydraulic delivery system was applied to directly determine arterial blood pressure. That is, the arterial cannula, manometry tubing and pressure transducer are interconnected and filled with anticoagulant fluid, constituting a hydraulic delivery system. The arterial cannula is inserted into the artery, and the pressure and its changes in the artery can be transmitted through the closed hydraulic pressure transfer system, and the pressure changes are converted into electrical signals by the pressure transducer, and the arterial blood pressure change curve is recorded by the microcomputer bio-signal acquisition and processing system. Move I. Experimental system connection and parameter setting For more product details, please visit Aladdin Scientific website.
1. Carotid blood pressure measurement and recording device. The blood pressure transducer was fixed on an iron pillar in the same plane as the heart.
2. Install the bloodletting device so that the femoral artery cannula is connected to the bloodletting bottle (60ml of saline is pre-filled in the bottle), open the tee to discharge the air in the pipeline of the bloodletting system and fill it with saline, and then close the tee. Put 0.5 ml of heparin into the bloodletting bottle, write down the amount of liquid in the bottle, and adjust the height of the bottle so that the liquid level in the bottle is about 65 cm from the level of the neck and heart, and the blood pressure can be maintained at about 6.67 kPa (50 mmHg).
3. Connect the pressure transducer output line to the 1st or 4th channel of the microcomputer biological signal processing system.
4. Set the parameters of the microcomputerized biosignal processing system:
(1) RM6240 system: Click "Experiment" menu, select "Rabbit Arterial Blood Pressure Regulation" in "Physiological Science Experiment" menu. The system enters the signal recording state of the experiment. Instrument parameters: 1 channel time constant DC, filter frequency 100 Hz, sensitivity 12 kPa, sampling frequency 800 Hz, scanning speed: 500 ms/div. Continuous single stimulation mode, stimulation intensity 5~10V, stimulation waveform width 2 ms, stimulation frequency 30 Hz.
(2) PcLab and MedLab system: Click "Arterial Blood Pressure Recording" in "Open Configuration" of "File" menu. The system enters the signal recording state of the experiment. Instrument parameters: 1 channel with 200 magnification, direct current (DC) coupling, sampling interval of 1 ms; serial stimulation mode, wave width of 2 ms, stimulation intensity of 5~10V, time interval of 1s, frequency of 30 Hz.
5. Blood pressure transducer calibration
The instrument and blood pressure transducer system were calibrated in the laboratory and no further calibration was required. The calibration method is described in Chapter 7, Experiment 16. The calibration values cannot be changed during the experiment.
II. Preparation for Surgery (see Chapter 4, Section I. Basic Animal Experimentation, Section IV. Surgery on Laboratory Animals)
1. After the rabbits are weighed, ethyl carbamate is anesthetized by intravenous injection at the ear margin at a dose of 1g/kg body weight. Be careful not to overdose the anesthetic and the injection speed should not be too fast.
2. The animal was fixed supine and tied to the operating table, the limbs were fixed, the forelimbs were cross-fixed, the rabbit incisors were hooked with cotton rope, and the rope was tightened and tied to the iron post of the rabbit table.
3. Expose the cervical trachea, common carotid artery, jugular vein, vagus nerve and aortic nerve. The right side of the above nerves was carefully isolated with a glass split-needle, and each nerve was threaded with a different color of fine silk thread for identification. Separate the common carotid artery on both sides and the jugular vein on both sides, and thread each with two threads.
4. Give the animal an intravenous injection of heparin at a dose of 1000 U/kg body weight. Wait for 1 minute before proceeding to the next step to allow the heparin to mix well in the bloodstream of the body.
5. cannulate the left common carotid artery
The distal end of the common carotid artery was ligated, the proximal end was clamped with an arterial clip, and a V-shaped incision was cut in the arterial wall with ophthalmic scissors close to the ligature, and the arterial cannula was inserted into the common carotid artery in a cardiac direction, tied and secured.
6. The skin of the femur was tautly fixed with the left thumb and the other four fingers, and the skin was incised along the midline of the ventral surface of the femur from the lower edge of the groin to the knee for 4-5 cm. The subcutaneous tissue was separated with hemostatic forceps, and the muscles of the femur were exposed. The femoral artery was isolated with a glass parting needle, and the vessel was separated for about 2~3 cm. 2 wires were threaded underneath it to ligate the vessel at the distal end, and the proximal end was clamped with an arterial clip to close the vessel. Near the ligation line of the distal end of the vessel at 0.3 cm, 1/3 of the diameter of the vessel was cut with ophthalmic straight scissors at an angle of 45°, and the free tip of the incision was grasped and picked up with curved ophthalmic forceps, and a vascular catheter was inserted for 2~4 cm, and the vascular catheter was ligated proximally. The intubating catheter was ligated again using the ligature wire at the distal end.