Why Invasive Blood Pressure Monitoring Is Needed

Blood pressure is the force exerted by circulating blood on the walls of the blood vessels. It facilitates the flow of blood throughout the body and can be categorized into arterial, capillary, and venous pressures, with the commonly referred to blood pressure being arterial blood pressure within the systemic circulation.

The maintenance of blood pressure is heavily influenced by the circulating blood volume and the vascular volume, which collectively determine the mean filling pressure of the circulatory system. This mean filling pressure is contingent on the balance between blood volume and circulatory system volume. An increase in blood volume or a decrease in vascular volume results in an increase in mean filling pressure, while a decrease in blood volume or an increase in vascular volume leads to a decrease in mean filling pressure. 

Consequently, significant blood loss or extensive small vessel dilation can cause a drop in blood pressure.

In essence, blood pressure is a vital aspect of cardiovascular function, ensuring the continuous circulation of blood throughout the body.

In life, blood is constantly flowing, the heart is the initial force of blood flow, and is another basic factor in the formation of blood pressure. When the ventricular myocardium contracts, blood enters the blood vessels, forms lateral pressure to the vascular wall, and dilates the vascular wall. This is, systolic blood pressure and systolic blood pressure mainly depend on the stroke volume of the heart, which is related to the contractile capacity of the heart (left ventricle), heart rate and the amount of blood volume. During the comfort phase, large arteries undergo elastic recoil to maintain intravascular pressure, which is the diastolic pressure. The level of diastolic blood pressure mainly depends on peripheral resistance, which is closely related to vascular elasticity and right ventricular function. Because the heart is intermittent, arterial blood pressure changes periodically during the cardiac cycle.

Non-invasive arterial blood pressure monitoring such as traditional cuff manometry is relatively simple, non-invasive and repeatable; it is relatively easy to master; and it has a wide range of indications. However, its disadvantages are obvious: ① it cannot be continuously monitored, it cannot reflect the blood pressure of each cardiac cycle, and it cannot display the arterial waveform; ② it affects the measurement results during peripheral vasoconstriction, hypovolemia and hypotension during hypothermia.

Therefore, invasive arterial pressure monitoring is required in many cases. Invasive blood pressure monitoring is complicated and a method for direct measurement of intra-arterial blood pressure by placing an arterial catheter in the artery. However, this method can reflect the blood pressure changes in each cardiac cycle and can directly display systolic blood pressure, diastolic blood pressure and mean arterial pressure, which are accurate and real-time. It is mostly used in the following cases: ① There is or may be circulatory instability. Such as: shock, fluid loss, hypotension, severe cardiovascular disease, valvular disease, diabetes, etc.; ② cardiovascular direct vision anesthesia surgery; intracranial anesthesia surgery and other life-threatening major surgery intraoperative and postoperative monitoring ③ other conditions, such as ICU patient monitoring.

Most studies suggest that the routine use of disposable sensors can be safely used for four days. However, after long-term use, such as more than 8 days, the bacterial contamination rate of the catheter is significantly increased. Most of the contaminating bacteria were gram-negative bacteria, and more than half were from the patient's own flora. The change of sensor is related to the occurrence of bacteremia, so it is not necessary to change the sensor frequently.

The CDC (U.S. Centers for Disease Control and Prevention) made the following recommendations on the use of pressure sensors in the 2017 Intravascular Catheter Anti-infective Guidelines: 

1. Use disposable rather than reusable sensor components whenever possible. 

2, disposable or reusable sensors were replaced every 96 hours. When replacing the sensor, replace other parts of the system (including tubing, continuous flush devices, and flushing solutions). 

3, minimizing the number of operations on the pressure monitoring system and its ports. Use a closed flush system (i.e., continuous flush) rather than an open flush system (i.e., use a syringe and stopcock) to maintain patency of the pressure monitoring system. 

4, do not infuse glucose-containing solutions or parenteral nutrition solutions through the pressure monitoring system. 

5, routine systemic prophylactic use of antimicrobial agents in order to prevent bacterial infections is not advocated.