Anatomy
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Thorax
A 45 year old man presents to ED complaining of severe retrosternal pain that is worse on coughing, and relieved by sitting forwards. The pain radiates to his left shoulder. On examination a pericardial rub is heard, and acute pericarditis is diagnosed. Which of the following nerves is responsible for the radiating pain to the shoulder:
Answer:
The fibrous pericardium is innervated by the phrenic nerve (C3 - C5). Irritation of the pericardium in pericarditis will result in pain being referred to the supraclavicular region of the shoulder and the C3 - C5 dermatomes in the neck region.Pericardium
Anatomy / Thorax / Heart and Pericardium
Last Updated: 11th April 2019
The pericardium is a fibroserous sac surrounding the heart and the roots of the great vessels in the middle mediastinum. It is composed of two main layers; the fibrous pericardium and the serous pericardium.
Pericardium. (Image by OpenStax College [CC BY 3.0 , via Wikimedia Commons)
Serous pericardium
The serous pericardium itself is divided into two parts which are continuous at the roots of the great vessels; the parietal layer which lines the inner surface of the fibrous pericardium and the visceral layer which lines the heart itself.
The parietal and visceral layer of serous pericardium are separated by the pericardial cavity which normally contains a small amount of lubricating serous fluid which reduces friction during normal movement of the heart.
Fibrous pericardium
The fibrous pericardium is a tough, inelastic sheath which fixes the heart in position (through its attachments to the central tendon of the diaphragm, the sternum and the tunica adventitia of the great vessels) and prevents sudden overfilling and distension of the heart.
Cardiac tamponade is acute compression of the heart caused by rapid accumulation of fluid or blood in the pericardial cavity from trauma (to the heart, great vessels or pericardial vessels) or pericardial effusion. The inflexibility of the fibrous pericardium results in increased intrapericardial pressure, with subsequent compression of venous return and reduced cardiac output.
Innervation
The pericardium receives its nerve supply from the vagus nerve, the sympathetic trunks and the phrenic nerves.
Somatic sensation from the parietal pericardium is carried by somatic afferent fibres in the phrenic nerves (C3 - C5); it is for this reason that pain related to a pericardial problem may be referred to the supraclavicular region of the shoulder or the lateral neck area dermatomes for spinal cord segments C3 - C5.
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- Biochemistry
- Blood Gases
- Haematology
| Biochemistry | Normal Value |
|---|---|
| Sodium | 135 – 145 mmol/l |
| Potassium | 3.0 – 4.5 mmol/l |
| Urea | 2.5 – 7.5 mmol/l |
| Glucose | 3.5 – 5.0 mmol/l |
| Creatinine | 35 – 135 μmol/l |
| Alanine Aminotransferase (ALT) | 5 – 35 U/l |
| Gamma-glutamyl Transferase (GGT) | < 65 U/l |
| Alkaline Phosphatase (ALP) | 30 – 135 U/l |
| Aspartate Aminotransferase (AST) | < 40 U/l |
| Total Protein | 60 – 80 g/l |
| Albumin | 35 – 50 g/l |
| Globulin | 2.4 – 3.5 g/dl |
| Amylase | < 70 U/l |
| Total Bilirubin | 3 – 17 μmol/l |
| Calcium | 2.1 – 2.5 mmol/l |
| Chloride | 95 – 105 mmol/l |
| Phosphate | 0.8 – 1.4 mmol/l |
| Haematology | Normal Value |
|---|---|
| Haemoglobin | 11.5 – 16.6 g/dl |
| White Blood Cells | 4.0 – 11.0 x 109/l |
| Platelets | 150 – 450 x 109/l |
| MCV | 80 – 96 fl |
| MCHC | 32 – 36 g/dl |
| Neutrophils | 2.0 – 7.5 x 109/l |
| Lymphocytes | 1.5 – 4.0 x 109/l |
| Monocytes | 0.3 – 1.0 x 109/l |
| Eosinophils | 0.1 – 0.5 x 109/l |
| Basophils | < 0.2 x 109/l |
| Reticulocytes | < 2% |
| Haematocrit | 0.35 – 0.49 |
| Red Cell Distribution Width | 11 – 15% |
| Blood Gases | Normal Value |
|---|---|
| pH | 7.35 – 7.45 |
| pO2 | 11 – 14 kPa |
| pCO2 | 4.5 – 6.0 kPa |
| Base Excess | -2 – +2 mmol/l |
| Bicarbonate | 24 – 30 mmol/l |
| Lactate | < 2 mmol/l |
