Central Venous Pressure monitoring is a frequently done procedure in many hospitals. There are many conflicting and poorly understood principles and practices surrounding the measurement of Central Venous Pressures. This article is written by a Lecturer in Health Sciences and helps in explaining some of the "not so clear issues". This article is for the benefit of student nurses and registered nurses.
Central Venous Pressure (CVP for short) is defined as the pressure of blood in the thoracic vena cava just before it (the blood) enters the right atrium of the heart. Normal CVP is 5 to 10 cm H2O.
CVP measurements are important in clinical cardiology because the CVP is a major determinant of the filling pressure of the right ventricle of the heart. The filling pressure of the right ventricle determines the stroke volume i.e. the amount of blood pumped with each contraction of the heart.
Background: Central Venous Pressure is an accurate indicator of the amount of blood returning to the heart from the head, body and limbs via the superior and inferior vena cava. If and when there is blood loss then the CVP reading will be altered (will fall) almost immediately as the amount of blood returning to the heart will have decreased. Central Venous Pressure is also an accurate indicator of the ability of the heart (myocardial pump strength) to pump out blood to maintain normal blood pressure and tissue perfusion. Last but not least, the CVP is an accurate indicator of right ventricular end diastolic volume. In most institutions CVP is measured in cm of water (H2O). On this scale the normal value of CVP is 5 to 10 cm H2O. Some, (very few) institutions measure CVP in mm. Hg (millimetres of mercury). On this scale the normal value is approximately 4 to 8 mmHg.
Central Venous Pressure in measured using a sterile indwelling central venous catheter (CVC). One end of the CVC is attached to a manometer or an electronic transducer, computer and monitor. Ultrasound may be used to guide CVC insertion. In the facility where I used to work experienced practitioners went in blind. Usually they were successful in locating the desired blood vessels without difficulty.
Central Venous Pressure monitoring is more accurate then blood pressure monitoring because changes in circulating volume will be reflected in changes in CVP values as soon as there is blood loss. Nurses and Nursing students will already know that in the first stage of shock, following blood loss, the compensatory mechanisms "adjust the blood pressure to normal levels". Consequently, blood pressure readings will remain within the normal range after blood loss but not the CVP.
When there is overloading of the circulatory system or there is heart failure the CVP rises. However, when there is dehydration (e.g. diabetes insipidus), fluid loss due to bleeding or shifting of fluids within the body compartments (e.g. shock) then the CVP will fall. We have studied that "fluid challenges" in the early stages of shock can prevent shock and subsequent death of a patient.
Generally, when the CVP is rising to unsafe (unhealthy) levels the patient may display difficulties with breathing. Conversely, when the CVP is falling there may be a decrease in urinary output and the patient may complain of feeling excessively thirsty. To correct over hydration, as illustrated by a rising CVP the physician may choose to restrict fluids or to administer a diuretic. To deal with a falling CVP the physician might choose to give the patient more fluids or blood as the case may be.
Most institutions have Policy and Procedure manuals which state the indications for the insertion of a CVP monitoring line.
Indications for Central Venous Pressure Lines
A central venous catheter is inserted by a qualified person into one of the central or peripheral veins and then threaded to the exterior of the right atrium where the superior vena cava meets the inferior vena cava. This is only done where medically indicated and qualified nursing staff is available to care, manage, and support the patient. Reading the CVP correctly is essential for the results to be useful therapeutically. The following are some of the general indications for inserting a CVP line.
Monitoring of Central Venous Pressure in the acutely ill patient. This allows the care giver to have an insight into the fluid balance status of the patient. High CVP would indicate fluid overload or a failing heart. Low CVP would indicate a degree of dehydration or blood loss. Exact fluid status can only be evaluated by correlating Hb, Cardiac Functioning and all other lab results and clinical history of the patient.
Total Parenteral Nutrition (TPN) Administration. When an acutely ill patient's GI tract is not able to absorb nutrients then the treatment team may decide to give the patient nutrition. This is called TPN and TPN can be given safely only via a CVP line or a peripherally inserted central line (PICC). Generally TPN is administered via a central intravenous catheter which is inserted in the subclavian or jugular vein. In infants the Umbilical vein is used most frequently. The rationale for using big deep veins for the administration is the fact that TPN causes phlebitis in peripheral veins because it is contains many caustic components. Examples include Calcium Chloride and Potassium chloride.
Medication Administration. Certain medications can be given safely only via a central line. Hence a CVP may be inserted for this purpose. Drugs that are likely to cause phlebitis include Chemotherapeutic Agents used in the treatment and management of malignant conditions. Amiodarone is used extensively in the management and treatment of acute life-threatening arrhythmias as well as for the suppression of chronic arrhythmias. It is useful both for supraventricular and ventricular arrhythmias because it has a low incidence of pro-arrhythmic effects. In arrest trials amiodarone has shown to improve survival rates (when compared to placebo) in individuals who suffer a cardiac arrest.
Lack of peripheral access. In some acutely ill patients, when there is no peripheral venous access, then a CVP line may be inserted. This is usually done for the purposes of rehydration, medication administration, administration of blood and blood products.
A Great article! You need to consider writing a book.
#2 by Ika, Apr 5, 2008
Thank u, and I'm waiting for the next article
#3 by Shergill, Apr 8, 2008
Good Day Ika,
Thank you for reading and commenting on my article.
I am currently working on two articles on Pain Management. One is a short three to five page article on essential principles of pain management. The other article is about everything a nurse should know about pain management.
Thank You for your comments. They are appreciated. It is nice to know that there are real people out there.
Lastly, do you have any topic you will like me to write on?
Shergill.
#4 by Yanee, Apr 17, 2008
Ei, Good Day, I'm a nursing student and last night i have been exposed with a patient with a CVP line for the first time. I don't know what CVP means or the nature and purpose of it. Glad that i have come across with your article. Simple and very easy to understand. Thank you!
By the way, I'm from the Philippines, just wanna let you know that you have a fan in this part of the world.
#5 by Shergill, Apr 23, 2008
Thank You for your comments. I am so pleased to hear that my article was able to help you. Remember, this is just the beginning. Nursing is a very challenging profession.
Good News: Lots of jobs everywhere. Even outside conventional hospital jobs.
Feel free to communicate with me. Use the latest articles only because I have published alot, I do not follow the comments on my older articles.
Good Luck with you career. Always care for your patient. He/She deserves all that we as nurses can give.
#6 by Jean, May 19, 2008
Can you tell me a specific situation where a CVP would be helpful in determining patient care?
#7 by Shergill, May 25, 2008
Good Day Jean,
There are many situations where the patients CVP would be very helpful when caring for a Patient.
a. All patients with internal bleeding disorders will benefit from CVP readings. The CVP will drop before peripherally measured blood pressure change becomes noticeable. Earlier intervention will result in a more favourable outcome for the patient.
b. All patients with renal failure will benefit from CVP readings. In these situations the CVP readings will rise due to circulatory overload. Appropriate intervention to correct the fluid overload will prevent the patient from becoming SOB or from dying.
c. All patients with CHF will benefit from CVP readings because circulatory overload can be detected early and treated early.
d. All patients receiving blood transfusions will benefit from CVP readings because blood transfusion rate can be titrated to the patients needs.
e. All patients benefit from this procedure during major surgery where it is necessary to maintain an accurate balance between blood loss and blood replacement.
f. All patients on dialysis benefit from this procedure.
g. All patients who are on large doses of diuretics benefit from this procedure.
I hope this answers your question. Otherwise feel free to communicate again.
#8 by Shergill, Jul 5, 2008
Hello YANEE. My Fan! GREAT TO HEAR FROM YOU!
Please drop me a line. I do check all my postings on a regular basis.
Shergill!
#9 by Barbara Pope, MSN, RN, CCRN, CCNS, Jul 31, 2008
A colleague and me were looking for an article on CVP measurement for our new critical care nurses. After doing a traditional literature search, I did an online ("Googe") search and found this. It is just what our nurses need. Thank you very much.
Barbara Pope
popeb@einstein.edu
#10 by Shergill, Aug 2, 2008
Good Day Barbara,
I appreciate the fact that you have taken the trouble to contact me. Triond wrote to me too and I did say to them that they could give you my email address.
Barbara, I am a Nurse Educator in Australia and my students read my work frequently. I am fortunate in that my articles are read extensively. With your qualifications you could be writing and publishing here. Our global students will be able to benefit from our efforts.
Sometimes I feel that we as nurses are not doing enough to educate the general public. You just need to look around at some to the lies that are published.
I write on political issues, nursing issues, male infant circumcision and much more.
When you read my profile you will be able to locate me. I lecture at a University in Darwin, Australia.
#11 by el, Aug 9, 2008
thanx a lot....youp article help me a lot in my assignment
#12 by Shergill, Aug 12, 2008
Good Day el,
Thank you for reading my article and "communicating with me".
I am glad my article helped you. If there is a specific topic you need me to write on please let me know. Please write to me on my latest article(s) for prompt response.
#13 by Jennifer Cruz, Aug 29, 2008
i enjoyed your article; it was very informative. but can you please shed some light on my query?
if you happen to know what are whats of the different ports of the Central Venous Pressure -- the three way lumen specifically for this matter-- the distal, medial and proximal ports. i mean where are do you extract blood from, where do you push the medications and stuffs like those.
A Great article! You need to consider writing a book.