Thoracocentesis

Equine Thoracocentesis

Introduction

Thoracocentesis is a procedure which has both diagnostic and therapeutic value.

When the findings from either thoracic auscultation or percussion suggest a pleural effusion, thoracocentesis can both confirm its presence and provide a specimen for examination. Drainage of pleural effusion via thoracocentesis is beneficial in removing large volumes of fluid from the thorax. Immediately following this drainage, some horses show increased pain, associated with loss of the ‘cushion’ of fluid in the pleural space. Removal of this fluid decreases respiratory effort and is beneficial in the resolution of an infectious process in the thorax. In horses with thoracic neoplasia and large volumes of pleural effusion, thoracocentesis and chest drainage may resolve signs of dyspnoea and respiratory distress.

Equipment

• Sedation as necessary
• Clippers and materials to perform a surgical scrub
• Ultrasonography if available
• Local anaesthetic and a 23G 3cm needle
• Sterile gloves
• Number 15 scalpel blade
• Cannula, 3-way tap and extension set
• EDTA tube, plain tube and sterile vial for culture

Procedure

The site for thoracocentesis can be identified using anatomical landmarks; 7-8th intercostal space on the left or 6-7th intercostal space on the right midway between the shoulder and the elbow. For more reliable identification of the correct position for thoracocentesis ultrasound can be used. As there are vessels and nerves running along the caudal aspect of each rib, the cannula should aim for the cranial border of the rib in order to avoid damage to these structures.

• The horse should be sedated and the area clipped and scrubbed

• Local anaesthetic should be administered into the subcutis, intercostal musculature and parietal pleura using a 23 gauge, 3 cm needle

• A stab incision using a number 15 scalpel blade should be made through the skin

• Prior to inserting the cannula, a three-way tap and extension set should be attached to it

• Using moderate pressure, the cannula should be pushed through first the intercostal muscles and secondly through the parietal pleura in order to enter the thoracic cavity. Passage of the cannula through the parietal pleura is extremely painful to the horse if the area has not been fully desensitised by the local anaesthetic

• A release in pressure should be felt when the cannula enters the thoracic cavity. The cannula can be manipulated and moved to collect as much fluid as possible

Complications

Pneumothorax

Peritoneal Fluid Analysis

Analysis of the pleural fluid may in turn help you to determine the underlying disease process and develop a therapeutic plan.

Pleural fluid from healthy horses may contain up to 10,000 nucleated cells/l and 35g/l total protein. Most horses have less than 5,000 nucleated cells/l and less than 25g/l total protein.

Small Animal Thoracocentesis

Introduction

Thoracocentesis is a procedure which has both diagnostic and therapeutic value.

When the clinical history, presenting signs and thoracic auscultation suggest a pleural effusion, thoracocentesis can both confirm its presence and provide a specimen for examination. It can be particularly useful in the emergency patient who is too unstable to undergo radiography or similar diagnostic tests as drainage of pleural fluid will both confirm its presence and improve clinical signs.

Equipment

• Clippers and materials to perform a surgical scrub
• Ultrasonography if available
• Sterile gloves
• Sterile needle (1 inch with the smallest possible gauge) with extension set or butterfly needle with incorporated extension set
• Sterile syringe
• 3-way tap - if large volumes of fluid are anticipated, as this allows for multiple syringe-fulls of fluid to be removed safely
• EDTA tube, plain tube and sterile vial for culture

Sedation is not generally required, especially in the dyspnoeic patient (however it can be used if necessary to prevent further stress to an excitable animal).

Procedure

The site for thoracocentesis is between the 7th and 8th intercostal space. If fluid is suspected in the pleural space then the needle should be inserted 2/3rds of the way down the chest. If pneumothorax is suspected then the needle should be inserted more dorsally, approximately 1/3rd down the chest. Local anaesthetic is not normally needed.

• Clip and scrub a generous area around the 7-8th rib space on both sides of the chest.

• Advance the needle slowly at a 45 degree angle in the middle of the 7th or 8th intercostal space into the pleural space.

• A small amount of negative pressure should be applied as the needle passes through the thoracic wall.

• The needle should be angled downward, parallel to the body wall. The fluid or air should then be aspirated.

Complications

Pneumothorax

Peritoneal Fluid Analysis

Analysis of the pleural fluid may in turn help you to determine the underlying disease process and develop a therapeutic plan.

References

Mair, TS & Divers, TJ (1997) Self-Assessment Colour Review Equine Internal Medicine Manson Publishing Ltd

RVC staff (2009) Respiratory System RVC Intergrated BVetMed Course, Royal Veterinary College

add electives reference and in practise reference.