MRCS Part B (OSCE) - Online Resources

"The following structures lie posterior to the upper part of the manubrium: left brachiocephalic vein, brachiocephalic trunk, left common carotid artery, left subclavian artery. The lower manubrium overlies the arch of the aorta. "

"In adults, manubrium sternii is a secondary cartilaginous joint (symphysis). "

"The manubriosternal junction corresponds to the intervertebral disc between T4- T5. "

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The important anatomical structures at the level of the manubriosternal joint are the:

 

• SVC entering the right atrium.
• Bifurcation of the trachea.
• Bifurcation of the pulmonary trunk.
• Arch of aorta.
• End of ascending aorta and beginning of descending aorta.
• Thoracic duct crosses from the right to the left mediastinum.
• Left recurrent laryngeal nerve hooks around the arch of the aorta.

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"The apex of the heart lies posterior to the left 5th intercostal space in adults, approximately 9-10 cm (a hands breadth) from the midline plane (middle of the sternum). "

"The pleura starts above the medial third of the clavicle and runs along the sternal edge up to the 6th rib. It then runs inferiorly to the level of the 8th rib in the midclavicular line, 10th rib in the mid-axillary line and 12th rib in the posterior axillary line. "

"The horizontal fissure is marked by a transverse line drawn from starting at the lateral border of the sternum in the 4th intercostal space towards the lateral thoracic wall (where the line intersects with the oblique fissure at the level of the mid-axillary line). "

"The oblique fissures (on the right and the left side) can be marked on the posterior thoracic wall with the patient standing with their hands behind their head (i.e., 90 degrees of shoulder abduction). The T3 vertebra should be identified (three spaces below the vertebra prominence, C7 vertebra) and an imaginary line drawn from this point along the medial edge of the scapula to the 6th intercostal space at the sternal edge. "

"Injury to a great vessel, cardiac chamber or one of the coronary or pericardial vessels can cause blood to accumulate in the pericardial sac. The fibrous, restrictive nature of the sac means diastolic filling is limited. As little as 15-20 ml of blood accumulating in this space can result in cardiac compromise and cardiogenic shock. "

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Clinical signs of cardiac tamponade include:

• Beck’s triad: hypotension, distended neck veins, muffled heart sounds.
• Pulsus paradoxus: a fall of more than 10 mmHg in systolic blood pressure with inspiration.
• Kussmaul’s sign: raised JVP with inspiration.
• Progressive tachycardia and cardiac dysrhythmias.
• Widened mediastinum seen on CXR.
• Pericardial clot and collapse of the right ventricle in diastole on echocardiogram
• Equilibration of cardiac filling pressures at cardiac catheterization.

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When performing pericardiocentesis, the skin incision should be made just to the left of the xiphoid process and 1-2 cm inferiorly. With the needle at a 45 degree angle it should be advanced (cautiously) cranially, toward the tip of the left scapula.