Anesthesia: in chest trauma

Introduction

• Avoid general anesthesia for 48 hours following trauma unless it is absolutely vital ’, eg continuing internal hemorrhage.
• Pulmonary lesions following chest trauma tend to worsen for 24-36 hours after injury.
• Pleural effusion or pneumothorax must be drained under local or regional (intercostal nerve block) anesthesia before sedation or general anesthesia.
• Myocardial contusion may result in ventricular dysrhythmias . These tend to resolve within a few days.
• Cardiac tamponade following traumatic pericardial effusion results in jugular vein distension, muffled heart sounds, tachycardia, hypotension and a weak pulse. Pericardiocentesis is essential prior to sedation or anesthesia.
• Shock , defined as inadequate tissue perfusion, may occur following severe trauma. Hypovolemic shock occurs rapidly and causes signs of pallor, tachycardia, cold extremities, disorientation, dysrhythmias, hypotension, cardiac output failure, oliguria and developing metabolic acidosis. Blood transfusion is essential to restore oxygen carrying capacity before general anesthesia.
• Neurogenic shock, caused by widespread vasodilation and relative hypovolemia may occur following severe trauma. Rapid infusion of crystalloid fluids is needed to prevent deterioration to irreversible shock.
• Untreated shock results in inadequate tissue perfusion, loss of cell membrane integrity, multiple organ failure, and death.

• Assess Airway, Breathing and Circulation and provide emergency first aid treatment as needed.
• Perform an external examination of the chest to check for penetrating injuries.
• Conscious thoracic radiography (dorso-ventral view) is essential ’ assess for pneumothorax, pleural effusions, lung contusion, cardiac tamponade, broken ribs, etc.
• Pre-anesthetic examination:
  • Respiratory rate and effort.
  • Pulse rate and quality; arterial blood pressure if equipment available.
  • Capillary refill time.
  • CNS assessment ’ alert, responsive, stuporous, comatose?

Pre-operative treatment

• For a successful outcome, stabilise the patient as much as possible before general anesthesia is attempted.
• Oxygen supplementation via an intranasal tube or by using an oxygen-enriched cage will improve hemoglobin saturation and oxygen delivery to the tissues.
• Fluid therapy will counteract the effects of shock. Crystalloids such as Hartmanns solution can be given at rates of up to 90 ml/kg/h in cases of acute hypovolemic or hypotensive collapse. Even animals that appear to have a reasonable circulation following trauma may benefit from crystalloid infusion of 20-40 ml/kg before induction of anesthesia. This is because the vasodilation caused by many anesthetic agents may unmask significant hypovolemia that has been compensated for by active vasoconstriction. This can avoid sudden cardiovascular collapse at induction of anesthesia.
• Thoracocentesis or pericardiocentesis if appropriate.

Analgesia

• Analgesia must be provided, especially if general anesthesia is being postponed.
• Clinical doses of pure agonist opioids such as pethidine or morphine will not cause significant respiratory depression. In fact ventilation becomes more efficient because pain and anxiety is decreased and tidal volume is improved.
• Non-steroidal anti-inflammatory drugs are best avoided in hypovolemic or shocked dogs because side-effects such as gastrointestinal ulceration and renal tubular necrosis are more likely to occur in these patients. Carprofen is the exception to this. It does not inhibit the production of protective prostaglandins to the same extent as other NSAIDs, and so is safer to use in hypovolemic patients. However, it is still essential to provide sufficient circulating volume replacement to reduce the risk of side-effects.
• Treat cardiac dysrhythmias. Ventricular premature contractions and ventricular tachycardia can be controlled with a lignocaine infusion of 0.02-0.08 mg/kg/min.

Sources

Publications

Other sources of information

• Martin D D (1996) Trauma patients. In: Lumb and Jones' Veterinary Anaesthesia.Eds J C Thurmon, W J Tranquilli and Benson G J. Williams & Wilkins. pp 829-844. ISBN 0 683 08238 8.