Question

Hemodynamics monitoring

Explain each:

-what is A line: where does it used, what are complications and factors

-CVP: what is it and what does low and high cvp represents, how does it interact

-Swans: relation between preload, afterload and contractility

-leveling

-zeroing

-why is it done

-how does it impact readings

Answer 1

1) A line means- arterial line: it is a type of cannula or invasive line which inserts in any artery to obtain blood sample for blood gas or other investigations and to monitor accurate BP. Mainly A line is using in Operation theatre and Intensive Care Unit.

2) Abbrevation of CVP is Central Venous Pressure. It is the blood pressure in the superior venae cavae, near the right atrium of the heart. CVP reflects the amount of blood returning to the heart and the ability of the heart to pump the blood back into the arterial system.

Central venous pressure is used to assess adequacy of blood volume. A long catheter is advanced via the jugular vein into the cranial vena cava. The pressure is measured by venous manometers, fluid-filled tubing, and a ruler or an electrical pressure transducer. The zero reference level is the right atrium, which is approximated by the sternal manubrium.Central venous pressure is usually reported as fluid level of the body.Normal central venous pressureranges from 0 to 5 cm H₂O. Pressures above 12 cm H₂O might indicate hypervolemia or cardiac failure. Below 5 is considered as hypovolemia and it leads to hypovolemic shock.

3) Swan-Ganz catheterization(swans) is the passing of a catheter into the right side of the heart and the arteries leading to the lungs. It is to monitor the heart's function and blood flow and pressures in and around the heart.

Afterload refers to the tension developed by the myocardium during ventricular systolic ejection. More commonly, afterload is described as the resistance, impedance, or pressure that the ventricles must overcome to eject their blood volumes. Afterload has an inverse relationship to ventricular function.

Preload refers to the amount of myocardial fiber stretch at the end of diastole, it also refers to the amount of volume in the ventricle at the end of this phase. It is clinically acceptable to measure the pressure required to fill the ventricles as an indirect assessment of ventricular preload.

4)All these lines are attached with a transducer and connect to cardiac monitor through a pressure monitoring cable.It must be 'zeroed' at the level of the right atrium. This is usually taken to be the level of the 4th intercostal space in the mid-axillary line while the patient is lying supine.

5)Zeroing is designed to negate the influence of external pressures, such as atmospheric pressure, on the monitoring system. Zeroing these invasive lines ensure that only the actual pressures from the patient will be measured by the transducer, thus providing accurate data on which to base treatment decisions.

6) Leveling and zeroing must be done because it provides accurate value.

7) Without zeroing and leveling, the monitor might show the default value.