What are hemodynamic monitoring indicators?

Blood is a very important part of the human body. Blood exists in various tissues and organs of the human body. The normal functioning of each tissue and organ requires blood circulation. If the blood circulation is not smooth, it will cause various diseases, such as myocardial infarction, heart failure and other diseases. Therefore, we need to take some measures to detect the blood. So let’s introduce what are the hemodynamic detection indicators?

Hemodynamic monitoring indicators are used for patients with critical illnesses such as myocardial infarction, heart failure, acute pulmonary edema, acute pulmonary embolism, shock caused by various reasons, cardiac and respiratory arrest, severe multiple injuries, multiple organ failure, and the perioperative period of major surgery, who need to closely monitor changes in circulatory system function in order to guide the use of cardiovascular active drugs.

1. Supplies and methods

1. Floating catheter method

There are two types of floating catheters currently commonly used in clinical practice:

① Ordinary catheter, with cold saline as the indicator, is injected into the right ventricle through the proximal hole of the catheter, mixed with the blood flow and heated up before flowing into the pulmonary artery. The temperature difference is sensed by the thermistor at the top of the catheter, and the cardiac output is calculated by computer. This method requires manual intermittent measurement;

②The improved Swan-Ganz catheter has a heat releaser at the proximal end of the right ventricle of the catheter. It emits energy pulses to heat up the local blood flow, mix it with the surrounding blood, cool it down and flow it into the pulmonary artery. The cardiac output is calculated by sensing it through the thermistor at the top, thereby continuously measuring the cardiac output and reducing complications such as operational errors, bacterial infections and changes in circulatory load.

2. Non-invasive hemodynamic monitoring

Commonly used clinical methods include transesophageal echocardiography, surface electrode cardiac impedance blood flow mapping and Doppler ultrasound technology. They have the advantages of being non-invasive and easy to operate, but have large absolute value errors and are meaningful as dynamic monitoring.

III. Main monitoring indicators

1. Indicators obtained by direct measurement

1. Upper limb arterial blood pressure (AP)

Normal values: systolic blood pressure 12.0~18.7kPa (90~140mmHg), diastolic blood pressure 8.0~12.0kPa (60~90mmHg).

Cardiac output, systemic vascular resistance, large artery wall elasticity, circulating volume and blood viscosity can all affect arterial blood pressure, and their relationship can be expressed by the following formula: mean arterial pressure = cardiac output × systemic vascular resistance + right atrial pressure.

2. Heart rate (HR)

Normal value: 60～100/min.

It reflects the compensatory ability of the heart pump to metabolic changes, stress response, volume changes, and changes in cardiac function. A moderate increase in heart rate can help increase cardiac output. At 160 beats/min, cardiac output will drop significantly.

3. Central venous pressure (CVP)

Normal value: 0.49～1.18kPa (5～12cmH20).

Changes in systemic blood volume, abnormal right ventricular ejection function or venous return obstruction can all cause changes in CVP. Changes in thoracic and intra-abdominal pressure can also affect CVP measurement results.

2. Indicators derived from direct measurement indicators

1. Cardiac Index (CI)

Normal value: 2.6～4.0L?min-1?m-2 (43.4～66.8ml?s-1?m-2).

After converting to body surface area, the effect of different body weight on cardiac output is eliminated, which more accurately reflects the heart's pumping function. When it is 2.4kPa (18mmHg), the possibility of cardiogenic edema is high. When it is >3.3kPa (25mmHg), cardiogenic edema is certain. 2.5L?min-1?m-2, PCWP100 times/min, systolic blood pressure>18.6kPa (140mmHg), sedatives or small doses of B-blockers may be considered.

2 . For pulmonary congestion type, CI>2.5L?min-1m-2, PCWP>2.0kPa (15mmHg). The treatment goal is to reduce PCWP. Diuretics and venodilators can be used.

3. For hypovolemic type, CI is 2.0 kPa (15 mmHg). The treatment goal is to increase CI and reduce PCWP by using vasodilators and diuretics, and positive inotropic drugs if necessary.