Clinical Cases - Thoracic Wall, Pleura, & Pericardium

During one of your third-year rotations you observe a resident on your service perform a thoracocentesis to obtain a sample of pleural fluid. The resident inserts the needle near the lower border of the eighth rib at the right anterior axillary line and withdraws a few milliliters of fluid. The next day, during your rounds, the patient complains of tingling and numbness of the skin of his chest from the level of the eighth rib down toward the umbilicus on the right side.

Questions to consider:

1. Why is the needle inserted in the eighth interspace?
   

   The needle needs to be inserted below the level of the lungs, in the costodiaphragmatic recess, which would be the eighth or lower interspace. Recall that at the midclavicular line, the recess is between rib spaces 6 and 8, at the midaxillary line between 8 and 10 and at the paravertebral line between 10 and 12.

2. How would you explain the presence of the parasthesia?
   

   Parasthesia is normally caused by some sort of nervous insult, i.e. impingement, cutting, or rough handling of a cutaneous nerve during a medical procedure, for instance.

3. What specific structure was likely damaged by the needle, and how does this explain the distribution of the parasthesia?
   

   8th intercostal nerve. The dermatome of the 8th intercostal nerve includes the region of the chest from about the eighth rib medially and inferiorly, towards the region just above the umbilicus.

4. What other structures are associated with the damaged structure and how are they arranged? Between what two muscle layers are these structures found?
   

   The 8th intercostal artery and vein are associated with the 8th intercostal nerve, and run along the subcostal groove of the eighth rib. The most superior structure is the vein, and the nerve is the most inferior structure. This neurovascular bundle is found between the internal and innermost intercostal muscles.

5. Where should the resident have inserted the needle to avoid damaging these structures?
   

   Needles used for thoracocentesis, or any other purpose in the region of the thorax should always be inserted near the upper border of a rib in order to avoid damage to the neurovascular bundles found below the ribs. However, in an intercostal nerve block, the needle would be inserted along the inferior margin in order to deliver the anesthetic agent to the nerve lying there.

6. For what other reasons (besides sampling pleural fluid) might a thoracocentesis be performed?
   

   Thoracocentesis may be used to drain a pleural effusion, empyema, or hemothorax, as well as to remove air from the pleural space in the case of pneumothorax.

A twenty-five year old male presents on your emergency room rotation after sustaining a single gunshot wound (GSW) to the right side of his chest. Paramedics found the patient awake and combative with a palpable pulse, systolic BP of 100 mm Hg, and respiratory rate 30/ minute. An occlusive dressing was taped over the entry site in the fifth intercostal space, midaxillary line. On arrival, the patient's vital signs were worse. You note that the patient's trachea is deviated to the left, his jugular veins are distended, he has no breathing sounds on the right side of his chest, he has palpable crepitus, and on percussion he has hyper-resonance on the right side of the chest. The resident on call determines that the patient has a tension pneumothorax and inserts a 14 gauge needle in the right midclavicular line at the second intercostal space - air is heard escaping. A chest tube is inserted at the fifth intercostal space in the midaxillary line and connected to a chest drainage device. The patient was stabilized and transferred to the Trauma Intensive Care Unit (TICU).

Questions to consider:

1. What might have created the tension pneumothorax?
   

   The nature of some injuries to the chest wall may create an opening that acts like a one-way valve. Trauma may create an inward swinging flap in the chest wall. Air is sucked into the pleural cavity during inspiration, but during expiration the chest wall closes on itself, preventing air from escaping.

2. Why did the resident insert the chest tube into the fifth intercostal space?
   

   Insertion of the chest tube at the fifth intercostal space allows the release and escape of air from the pleural space into the chest drainage device. In addition, it allows the physician to intervene immediately to remedy a potentially life threatening event while preventing further damage to a potentially injured diaphragm.

3. What structures did the chest tube pass through to enter the pleural cavity?
   

   Skin, fat, external intercostal muscle, internal intercostal muscle, innermost intercostal muscle, endothoracic fascia, and parietal pleura.

4. What is tension pneumothorax?
   

   It is the presence of air in the pleural space under pressure. The lung collapses, and a mediastinal shift interferes with the expansion of the contralateral lung and compromises venous return to the heart via the IVC. This condition is extremely dangerous and requires urgent action. Other possible injuries leading to tension pneumothorax are demonstrated.

5. What are the signs and symptoms of tension pneumothorax?
   

   Tachypnea, contralateral tracheal deviation, hyperresonance, distended neck veins, dyspnea, and hypotension.

6. What is the appropriate treatment?
   

   Needle thoracocentesis in the second intercostal space in the midclavicular line, followed by chest tube placement.

References:

Moore's Clinical Anatomy pp. 48-60.
Advanced Surgical Recall pp 326 - 339.