N-Trivia

Fontan Procedure
Anatomical Body Landmark
Difference Between Adult and Fetal Circulation

Posted: 12 Nov 2010 06:57 PM PST

Fontan Procedure

Definition

Fontan Procedure is an open heart surgery where a passageway is created to shunt the nonoxygenated blood directly to the pulmonary artery and lungs bypassing the right ventricle. Dr. Francis Fontan first performed this operation in 1968. In 1971, Dr. Fontan and Dr. Kreutzer initially described this procedure as a surgical management for tricuspid atresia.

Indications

This operation is an open heart procedure used to treat or manage complex heart defects such as:

Tricuspid Atresia – a congenital heart defect where the tricuspid valve (valve that is located in between the right atrium and right ventricle) is closed thus preventing blood from entering the pulmonary artery and lungs.
Hypoplastic left heart syndrome
Single ventricle
Pulmonary atresia

Goals of Fontan Procedure

To improve the oxygenated blood level (by redirecting non-oxygenated blood directly to the lungs)
To decrease the workload of the heart
To retain growth potential of the child

Requirements of the procedure

Normal pulmonary vascular resistance
Healthy left ventricle to pump the blood in the systemic circulation (Good systolic and diastolic function of left ventricle)
No valve leak
Closed atrial septal defect if present
Normal mitral valve function

Fontan Circulation

Blood goes back to the heart via the superior and inferior vena cava. From these veins, blood empties in the right atrium. Normally, the tricuspid valve opens to drain the blood to the right ventricle. In cases where the tricuspid valve is absent or closed (tricuspid atresia), blood is stuck in the right atrium preventing the blood to enter the right ventricle to be pumped into the pulmonary arteries and lungs. No blood oxygenation would take place.

In a Fontan circulation, a passageway is created from the veins to the pulmonary artery directly. This bypasses the right ventricle of the heart.

Laboratory Tests before the Procedure

Chest X-ray
ECG (Electrocardiogram)
Echocardiography
Blood tests

Stages of Fontan Procedure

Blalock-Taussig Shunt

Neonates have increased pulmonary resistance; hence, fontan operation cannot be performed (see procedure requirements). For these cases, a Blalock-Taussig shunt procedure is done as the first operation. A tube graft connects one of the subclavian arteries to the pulmonary artery to ensure pulmonary blood flow and adequate oxygenation for a few months.

Bi-directional Glenn or Hemi-Fontan procedure

After a few months, when the infant outgrow the shunt, a bidirectional Glenn or hemi-fontan procedure is done. In this procedure, the superior vena cava (SVC) is anastomosed to the pulmonary artery resulting to blood flow from the SVC directly to the pulmonary artery. The Blalock Taussig shunt is removed or ligated. Usually, the operation is done in about 4-8 months of life.

Fontan Completion Operation

In this procedure, the superior and inferior vena cava are connected to the pulmonary artery.

Several cases have been reported of having good results in children as young as 1 year old. However, most patients are about 18-24 months old when this operation is performed.

Types of Fontan Operation

Atriopulmonary Connection (original and now rarely used)

In this operation, the right atrium is connected to the pulmonary artery. If atrial septal defect is present, it should be closed. Blood flows from the superior vena cava to the right atrium to the pulmonary artery and lungs.

Intracardiac total cavopulmonary connection (lateral tunnel)

A tunnel-like patch is placed inside the atrium that directs venous return to the pulmonary artery and into the lungs.

Extracardiac total cavopulmonary connection

The superior vena cava is directly connected to the pulmonary artery and the inferior vena cava (IVC) is re-routed through a synthetic tube sewn directly to the top of IVC. The tube is connected to the pulmonary artery allowing the non-oxygenated blood to enter the lungs.

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Anatomical Body Landmark

Posted: 12 Nov 2010 06:27 PM PST

Anatomical Body Landmarks

Anatomical Position

anatomical position

The first important thing in learning about anatomy and physiology is to know the anatomical position and body landmarks. To accurately describe body parts and position, initial reference point and directional terms should be used in a medical setting. The correct anatomical position is standing up (erect) with the feet parallel and the arms hanging at the sides with the palms facing forward and the thumbs pointing away from the body.

Body Landmarks

To precisely point out the chief complaint of a patient, the nurse or physician uses anatomical terms representing a certain body part. For example, a patient walks in the emergency room with a hacking wound on the posterior portion of the left lower leg. To clearly state the area of injury the nurse uses the term "sural" which means the posterior surface of the lower leg rather than writing "back area of the lower leg". Knowing these terms not only give the nurse a more accurate formulation of chief complaints but it also saves time of a good deal of description.

Anterior Body Landmarks

Abdominal – anterior body trunk inferior to ribs

Acromial – point of shoulder

Antecubital – anterior surface of elbow

Axillary – armpit

Brachial – arm

Buccal – cheek area

Carpal – wrist

Cervical – neck region

Coxal – hip

Crural – leg

Digital – fingers, toes

Femoral – thigh

Fibular – lateral part of the leg

Inguinal – area where thigh meets body part

Nasal – nose area

Oral – mouth

Orbital – eye area

Patellar – anterior knee

Pelvic – area overlying the pelvis anteriorly

Pubic – genital region

Sternal – breastbone area

Tarsal – ankle region

Thoracic – chest

Umbilical – navel

Posterior Body Landmark

Calcaneal – heel of foot

Cephalic – head

Deltoid – curve of shoulder formed by large deltoid muscle

Femoral – thigh

Gluteal – buttock

Lumbar – area of back between ribs and hips

Occipital – posterior surface of head

Olecranal – posterior surface of elbow

Popliteal – sacral

Scapular – shoulder blade region

Sural – posterior surface of the lower leg

Vertebral – area of spine

Plantar – sole of the foot

Directional Terms

To clearly explain exactly the relation of a body structure to each other, directional terms are used. For example to describe the relationship or location of the heart to the arms, we can say "the heart is located in between the arms". Using anatomical terminology, this is expressed as "the heart is medial to the arms." Hence, it is a more clear and precise statement.

Superior – above

Inferior – below

Anterior – in front of

Posterior – behind

Medial – middle

Lateral – away from the middle; at outer the sides

Intermediate – between a more medial and a more a lateral surface

Proximal – close to the body part

Distal – away from a body part

Superficial – external; at the surface

Deep – internal; away from the surface

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Difference Between Adult and Fetal Circulation

Posted: 12 Nov 2010 06:26 PM PST

Difference between Adult and Fetal Circulation

Criteria	Adult Circulation	Fetal Circulation
Artery	Carries oxygenated blood away from the heart	Carries Non-oxygenated blood away from the fetal heart
Veins	Carries non-oxygenated blood towards the heart	Carries oxygenated blood back to the heart
Exchange of Gases	Takes places in the lungs	Takes place in the placenta
Pressure	Increase pressure on the left side of the heart	Increase pressure on the right side of the heart

Adult circulation sequence

Non-oxygenated blood enters the right atrium via the inferior and superior vena cava.
Increase level of blood in the right atrium causes the tricuspid valve to open and drain the blood to the right ventricle.
Pressure of blood in the right ventricle causes the pulmonic valve to open and non-oxygenated blood is directed to the pulmonary artery then to the lungs.
Exchange of gases occurs in the lungs. Highly oxygenated blood is returned to the heart via the pulmonary vein to the left atrium.
From the left atrium the pressure of the oxygenated blood causes the mitral valve to open and drain the oxygenated blood to the left ventricle.
Left ventricle then pumps the oxygenated blood that opens the aortic valve. Blood is then directed to the ascending and descending aorta to be distributed in the systemic circulation.

Fetal Circulation Sequence

Exchange of gases occurs in the placenta. Oxygenated blood is carried by the umbilical vein towards the fetal heart.
The ductus venosus directs part of the blood flow from the umbilical vein away from the fetal liver (filtration of the blood by the liver is unnecessary during the fetal life) and directly to the inferior vena cava.
Blood from the ductus venosus enters to the inferior vena cava. Increase levels of oxygenated blood flows into the right atrium.
In adults, the increase pressure of the right atrium causes the tricuspid valve to open thus, draining the blood into the right ventricle. However, in fetal circulation most of the blood in the right atrium is directed by the foramen ovale (opening between the two atria) to the left atrium.
The blood then flows to the left atrium to the left ventricle going to the aorta. Majority of the blood in the ascending aorta goes to the brain, heart, head and upper body.
The portion of the blood that drained into the right ventricle passes to the pulmonary artery.
As blood enters the pulmonary artery (carries blood to the lungs), an opening called ductus arteriosus connects the pulmonary artery and the descending aorta. Hence, most of the blood will bypass the non-functioning fetal lungs and will be distributed to the different parts of the body. A small portion of the oxygenated blood that enters the lungs remains there for fetal lung maturity.
The umbilical arteries then carry the non-oxygenated blood away from the heart to the placenta for oxygenation.

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