Blunt trauma to the chest commonly results in lung contusions. Rarely, rib fractures may cause lung laceration (see Figure 14.3). Blunt chest trauma is more often associated with trauma to other organ systems or body areas.
Initial Management and Stabilisation
In cases with inadequate ventilation immediate intubation and assisted ventilation is indicated. Bite wounds to the neck may disrupt the larynx or trachea causing subcutaneous emphysema (see Figure 14.4).
Animals with marked dyspnoea caused by pneumothorax should have an immediate thoracocentesis which will usually provide substantial relief. If the pneumothorax recurs, chest drain placement and continuous drainage may be required. When a pneumothorax is secondary to an open ‘sucking’ chest wound, a chest drain should be placed through the wound and the wound covered with an occlusive dressing. The pneumothorax can then be drained. The pain associated with rib fractures and flail segments substantially limits the tidal volume; this may be relieved with carefully titrated dose of opioids or intercostal nerve blocks.
Pulmonary contusions can cause substantial ventilation–perfusion mismatch and hypoxia. This may be improved by oxygen supplementation, but in severe cases assisted ventilation using positive end expiratory pressure may be necessary. In cases without evidence of substantial haemorrhage but with indications of pulmonary damage, crystalloids should initially be limited to a bolus of 10–15 ml/kg.
Orthogonal thoracic radiographs allow further evaluation of injuries. Not all penetrating thoracic wounds show radiographic evidence of pneumothorax. Radiographs are useful for evaluating the position and track of a radiopaque projectile. Additional imaging techniques may be indicated (see Figures 14.5, 14.6 and 14.7).
Pain management is vitally important in the thoracic trauma patient, and a multi-modal approach should be utilised including epidural anaesthesia, intrapleural installation of local anaesthetic, intercostal blocks and systemic pain medication as appropriate.
Anaesthesia and surgical exploration may be needed in some cases and ideally should take place once the animal is stabilised. However, complete stabilisation may not be possible. A lateral thoracotomy provides easier access to defined unilateral lung lesions, fractured ribs and certain parts of the heart. A median sternotomy provides access to both hemithoraces, the heart and great veins and can be extended into a ventral midline laparotomy when necessary (see Figure 14.8). Before performing anaesthesia for the exploration of thoracic trauma, the nurse should prepare all equipment to carry out intermittent positive pressure ventilation (IPPV) should a thoracotomy be required.
Monitoring the Head Trauma Patient
Traumatic injuries to the head leading to brain injury and neurological dysfunction are commonly seen in practice. The trauma is often caused by road traffic accidents, but also falls, kicks, gunshot wounds and penetrating injuries (see Figure 14.9).
These injuries can often produce severe clinical signs, but if managed correctly the majority can recover enough function to return to normal life as a pet. There are few specific medical or surgical interventions that specifically improve outcome, but there is a lot of incorrect management that will definitely result in a worse outcome. Appropriate nursing and management will make the most difference. As with most trauma patients, it is essential to monitor and take care of the basics.
Primary Brain Injury
This occurs immediately post-trauma; the effects can be haemorrhage, contusion, concussion and laceration. This injury is often irreversible and we can make no difference to it.
Secondary Brain Injury
This is the delayed consequence of the primary injury, hours or days later, and relates to release of inflammatory mediators, injured axons and continued haemorrhage and oedema, and ultimately alterations in intracranial pressure. It is in the treatment of secondary brain injury (and the prevention of secondary brain injury) that our management will dictate outcome.
The brain is enclosed in a rigid box (the calvarium). The contents of that box are brain tissue (86%), cerebrospinal fluid (10%) and blood (4%); all these contents are non-compressible. If normal intracranial pressure (ICP) is to be maintained, if one of these three components increases in size, the others must decrease – this is volume buffering. Once buffering is no longer effective, ICP will rise, and small mistakes in management will lead to massive increases in ICP. Any increase in ICP leads to reduced blood perfusion pressure.
so any increase in ICP, or decrease in MAP, will lead to less blood reaching the brain.
Assessment of the head trauma patient is initially exactly the same as any trauma patient. Assess and attend to the ABC, but avoid manipulation of the head and neck, and never compress the jugular vein.
The immediate focus should not be on the patient’s neurological status. If the animal is hypoxic due to respiratory injury, or is hypovolaemic, then any depression of mentation will be increased. Assess respiratory function by ensuring the patient has a patent airway, and noting respiratory rate and pattern. Is any alteration due to brain injury, or chest trauma? Pulse oximetry and arterial blood gas analysis can objectively assess function.
MAP can be valuable, as this relates closely to cerebral blood flow, a systemic blood pressure below 50 mmHg will lead to decreased cerebral blood flow.
So, before we assume all changes in mentation are due to brain damage, we make sure that blood is being oxygenated correctly and that the circulation is capable of delivering that blood to the brain.
The examination can now move to the head. Check for the presence of haemorrhage in nasal sinuses, ear canals, nasopharyngeal area and orbit, as this often indicates skull fractures. Palpate gently for crepitus and the presence of subcutaneous emphysema.
Neurological assessment should include the level of consciousness, breathing pattern, responsiveness of the pupils, ocular position and movements, and skeletal motor responses.
A scoring system allows grading of neurological status on initial presentation, and allows comparison to measure progress and help offer prognosis. A modification of the Glasgow Coma Score (MGCS) is used, sometimes referred to as the Small Animal Coma Score (SACS) (see Table 14.1).
|Motor function activity||Normal gait, normal spinal reflexes||6|
|Hemiparesis, tetraparesis or decerebrate activity||5|
|Recumbent, intermittent extensor rigidity||4|
|Recumbent, constant extensor rigidity||3|
|Recumbent, constant extensor rigidity with opisthotonus||2|
|Recumbent, hypotonia of muscles, depressed or absent spinal reflexes||1|
|Brainstem reflexes||Normal pupillary light reflexes and oculocephalic reflexes||6|
|Slow pupillary light reflexes and normal to reduced oculocephalic reflexes||5|
|Bilateral unresponsive miosis with normal to reduced oculocephalic reflexes||4|
|Pinpoint pupils with reduced to absent oculocephalic reflexes||3|
|Unilateral, unresponsive mydriasis with reduced to absent oculocephalic reflexes||2|
|Bilateral, unresponsive mydriasis with reduced to absent oculocephalic reflexes||1|
|Level of consciousness||Occasional periods alertness and responsive to environment||6|
|Depression or delirium, capable of responding but response may be inappropriate||5|
|Semicomatose, responsive to visual stimuli||4|
|Semicomatose, responsive to auditory stimuli||3|
|Semicomatose, responsive only to repeated noxious stimuli||2|
|Comatose, unresponsive to repeated noxious stimuli||1|
Three categories are measured: