This experiment is from the official website of Zhejiang University Fine Courses
Operation method
Changes in blood acidity and alkalinity in rabbits and blood gas analysis experiments
Principle
Respiratory movements are a reflection of the rhythmic activity of the respiratory center. In different physiological states, the adaptive changes of respiratory movement depend on the reflex regulation of the nervous system, of which the more important ones are the respiratory center, the pulmonary stretch reflex and the reflex regulation of peripheral chemoreceptors. Thus, various stimuli, both internal and external, can affect respiratory movements either directly at the central site or reflexively through different receptors. Metabolic acidosis is characterized by a primary decrease in plasma HCO3- concentration. In this experiment, the rabbit metabolic acidosis model was replicated by intravenous injection of NaH2PO4 to increase the extracellular fluid H+ concentration, consume HCO3- and reduce the plasma HCO3- concentration. The accelerated respiration of metabolic acidosis animals is caused by the increase of H+ concentration in the blood, which stimulates the peripheral chemoreceptors of carotid and aortic bodies and the central chemoreceptors of medulla oblongata, and reflexively excites the medulla oblongata respiratory center. The deepening of respiration is accelerated, alveolar ventilation is increased, CO2 excretion is increased, and the blood H2CO3 concentration decreases, restoring the normal ratio of [NaHCO3]/[H2CO3]. This compensatory modulation can occur within minutes and peak quickly, but complete compensation is generally not easily obtained. In metabolic acidosis, the plasma HCO3- concentration is reduced in a primary manner, and the indicators reflecting metabolic factors, AB, SB, and BB, can be measured on blood gas analysis, with an increased negative value of BE, while PaCO2 can be lowered due to respiratory compensatory activity, with AB < SB. In metabolic acidosis animals with reduced plasma bicarbonate, sodium bicarbonate can be used as a preferred alkali-replenishing drug, which is directly administered intravenously, so that the extracellular fluid's [ NaHCO3]/[H2CO3] ratio back to normal. Respiratory acidosis is caused by pulmonary ventilation dysfunction and is characterized by CO2 retention in the body and a primary increase in plasma H2CO3 concentration. Respiratory acidosis can be replicated using methods that reduce pulmonary ventilation in animals. In respiratory acidosis, the respiratory system often fails to play a compensatory regulatory role, and [NaHCO3]/[H2CO3] buffering is sorry to play a role, and the buffering of extracellular fluids is so limited that it is unlikely to receive a significant regulatory effect. Blood gas analysis can be seen to reflect the respiratory factors of the indicators obvious PaCO2, AB significantly increased.
Materials and Instruments
Rabbit Ethyl carbamate Heparin sodium Epinephrine hydrochloride Norepinephrine bitartrate Isoprenaline sulfate Phentolamine propranolol hydrochloride Acetylcholine acetylcholine acetylcholine atropine sulfate Atropine; Pressure transducer Bio-signal Acquisition and Processing System Move I. Experimental system connection and parameter setting For more product details, please visit Aladdin Scientific website.
1. Rabbit respiratory movement recording device.
2. Fix the respiratory transducer on the iron pillar. Connect the output line of the respiratory transducer to the first channel of the microcomputer biological signal processing system (other channels are also available). Set the parameters of microcomputer biological signal processing system:
(1) RM6240 system: Click "Experiment" menu, select "Breathing" or "Breathing Movement" in "Customized Experiment" menu. Adjustment" in the menu of "Respiration" or "Customized Experimental Project". The system enters the signal recording state of the experiment. Instrument parameters: channel time constant is DC, filter frequency 30Hz, sensitivity 10cmH2O (or 12.5ml), sampling frequency 800Hz, scanning speed 1s/div. Continuous single stimulation mode, stimulation intensity 5~10V, stimulation waveform width 2ms, stimulation frequency 30 Hz.
(2) PcLab and MedLab system: Click "Experiment" menu, select "Common Physiology Experiments" or "File" menu. Open the "Respiration Recording" item in the "Configuration" menu. The system enters the signal recording state of the experiment. Parameters: channel amplification 1000, DC coupling (lower limit frequency DC), upper limit frequency 40Hz, sampling interval 2-5ms; stimulation wave width 2ms adjustable; stimulation intensity: 5~10V; main cycle stimulation mode, continuous pulse, pulse number 30, wave interval 33.3ms.
II. Preparation for surgery (see Chapter 4, Section 1, Basic operation of animal experiments, Section 4, Surgery of experimental animals)
1. Anesthesia fixation
After the rabbits were weighed, 200g/L urethane was anesthetized at 1g/kg body weight by intravenous injection at the ear margin. After the rabbit was anesthetized, it was fixed supine.
2. Surgery
The anterior neck coat was cut off with coarse scissors, and the skin was incised in the middle of the anterior neck for 6~8 cm, up to 1.5~2 cm above the angle of the lower jaw. Soft tissues and neck muscles were bluntly separated with hemostatic forceps to expose the trachea and the left and right vascular nerve sheaths that were parallel to the trachea, and the vagus nerves within the sheaths on both sides were carefully separated, and threads were threaded underneath the vagus nerves to be used for spare parts. The common carotid artery in the sheath on one side was separated, the distal end of the common carotid artery was ligated, and the proximal end was clamped with an arterial clip in preparation for blood extraction.
3. Tracheal intubation
Separate the trachea with hemostatic forceps and thread two thick cotton threads under the trachea for backup. About 1cm below the thyroid cartilage, make a "⊥"-shaped incision, use a cotton swab to wipe the tracheal incision and the trachea of blood and secretions, tracheal tube from the incision to the lung end of the insertion should be inserted gently, to avoid damage to the mucosa of the trachea caused by bleeding, with a thick cotton wool will be intubated to the mouth of the ligature fixed, and the other cotton wool in the incision at the head of the ligature to stop bleeding. Cover the surgical field with warm saline gauze.
4. Systemic anticoagulation was performed with 10 g/L heparin at a dose of 1 ml/kg body weight via the marginal ear vein.