Central Venous Pressure and Central lines Big Lines for Big Problems
Challenging Knowledge Before starting this module; Answer the following questions (1) What sites are used to site a CVL? (2) What is the normal CVP? (3) What are the basic treatments for a CVP of -1cm of H 2 0 (4) What are the essential items required to measure a CVP?
Learning Outcomes By the end of this module you should (1) Be aware of factors which affect the CVP (2) Recognise normal and abnormal CVP values (3) Be able to set up the manometer system to measure a patient s CVP (4) Be able to measure a CVP and interpret the value (5) Be aware of the initial management for high and low values
Factors affecting the CVP The central venous pressure reflects the right atrial pressure (RAP) and is similar to measuring the JVP clinically The factors which affect the CVP are:- Systemic vasodilatation and hypovolaemia, which leads to reduced venous return in the vena cava and reduced RAP Right ventricular failure Tricuspid and Pulmonary valve disease Pulmonary hypertension Right ventricular dysfunction and pulmonary hypertension leads to raised right atrial pressure, as does tricuspid and pulmonary stenosis.
Central venous line (CVL) Indications for CVL Severe hypovolaemia requiring rapid infusion (although initial resuscitation may be peripheral through wide bore cannulae) Infusion of drugs which may cause peripheral problems e.g. vasoconstriction, phlebitis Measurement of central venous pressure (CVP) Confirmation of diagnosis e.g. Right heart failure Insertion of a pacing wire. Sites for insertion Internal jugular, subclavian and femoral vein; Long lines are also inserted in the brachial vein.
How to measure the CVP using a manometer system The CVP system A bag of saline or dextrose = reservoir Three way tap - connected to manometer, reservoir and patient s CVL by tubing; System is primed with fluid before starting Patient is lying supine if possible Manometer has spirit level at zero ; Zero point is aligned with right atrium using the mid axillary line / 4 th ICS Measurements should be taken with the patient in the same position each time using the spirit level; the zero point on the skin surface is marked for consistency of measurement Three way tap Patient positioned supine on the bed
How to measure the CVP using a manometer system Turn the three way tap OFF to the patient. Fill the manometer to the top from the reservoir Turn the three way tap OFF to the reservoir This means the column of fluid is supported only by the RAP / CV pressure The column will fall according to CVP The column swings with respiration - conventionally the level is taken as the mean. Three way tap OFF to the patient allowing the manometer to be filled Three way tap OFF to the reservoir allowing the CVP to be measured
Normal CVP measurements The normal CVP is between 5 10 cm of H 2 O (it increases 3 5 cm H 2 O when patient is being ventilated) In high dependency areas an electronic transducer is connected instead of the manometer system. This gives a continuous readout of CVP along with a display of the waveform. This may be measured in mmhg. (Note:10 cmh 2 0 = 7.5mmHg =1kPa)
CVP Reading Other clinical features Diagnosis Treatment Low Tachycardia Low normal or hypotension Urine output oligo or anuria Hypovolaemia Fluid challenge until CVP within normal limits and treat underlying cause Low ( may be normal or high due to venoconstriction) Tachycardia Signs of infection Pyrexia Vasodilatation is most common but severe sepsis maybe associated with constriction Sepsis Fluid resuscitation (if low) Antibiotics May require inotrope support Normal due to venoconstriction Tachycardia Urine output falling below 30ml /hr Poor capillary refill Hypovolaemia Fluid challenge and treat underlying cause High Dyspnoea with pulmonary crepitations Tachycardia with third heart sound Tender hepatomegaly Ascites Peripheral Oedema Heart failure Diuretics, GTN infusion, may require inotropes Very High Venous congestion and dilatation of face and neck; associated signs SVC obstruction Cardiac tamponade Tension pneumothorax Treat underlying cause
Case (1) How low can you go? A 32 year old woman with known alcohol associated liver disease presents with melaena. Initially she is haemodynamically stable and well perfused. She suddenly decompensates with fresh blood and clots being passed PR. Initial resuscitation with several litres of crystalloid and some colloid fails to bring her systolic BP back above 100 mm Hg. A CVP line is inserted and shows her CVP to be +1 cmh 2 O. (a) What is the likely diagnosis? (b) List your further management including investigations and medications
Case (2) CVP Pat pending A 31 year old man presents to A&E with a 3 month history of night sweats and weight loss. On examination he is unwell, pyrexial and has several large cervical lymph nodes. He is noted to have poorly palpable radial pulse, a positive Kussmaul s sign and poorly heard heart sounds. The SHO decides to site a CVP which is measured at 28 cm of H 2 O. (a) What is the likely underlying diagnosis? (b) What is the initial treatment? (c) How will you prove the diagnosis?
Case (3) A 48 year old poorly controlled Type 2 diabetic man is admitted from the Diabetes clinic with a deep, infected foot ulcer. His observations are: pulse 120bpm, BP 70/40, CVP +6 cm of H 2 0 and he is noted to be sweaty and vasodilated. Despite initial resuscitation with 3 litres of crystalloid in 4 hours, his BP and pulse fail to respond. He is electively ventilated and admitted to ITU where he is started on inotropes. (1)What is the descriptive term given to this clinical state? (2)List your further management?
Learning Outcomes At the end of this module you should (a) Be aware of the factors affecting the CVP. (b) Be able to set up a CVP manometer system. (c) Be able to measure a CVP from a patient. (d) Be able to interpret the result. (e) Be able to institute initial management based on the result.