Management of the Shock Trauma Patient

Harold Davis Jr., RVT, VTS (Emergency & Critical Care)

Trauma is a wound or injury occurring as a result of an animal's body striking or being struck by an object, from environmental, chemical and thermal insults, or injuries inflicted by other animals. Motor vehicle, animal interactions and trauma of unknown cause comprised 70 to 80% of all injuries in dogs and cats in one study.

These patients may have multisystemic problems, which require rapid and accurate assessment, and treatment. Emergency caregivers must be prepared, both academically and technically to meet the demands of these patients.

The team leader coordinates management of the trauma patient. The team leader performs the primary and secondary survey and directs the resuscitative endeavor. Treatment priorities are based on identifying and correcting life threatening problems. If possible, problems should be anticipated rather than reacted to. Other responsibilities are divided between the remaining team members. This may entail managing the airway and breathing; establishing vascular access; initiating patient monitoring and documentation. Following resuscitation and stabilization the patient is prepared for definitive care, which may require transport to another center.

Triage

Triage is the prioritization of treatment based upon medical need. On Initial presentation to the hospital the veterinary technician may be the first to receive the patient. It will be their responsibility to triage the patient(s). While approaching the patient, visually assess ventilation effort, pattern and any audible airway sounds; presences of blood or other foreign material about the patient; and the patients posture and level of consciousness (LOC). If time permits a basic history should be obtained.

Initial Patient Management

The initial management of the trauma patient involves primary survey and resuscitation, secondary survey, and definitive management.

Primary Survey and Resuscitation

The primary survey is the initial, brief assessment, which involves A) airway, B) breathing, C) circulation D) for dysfunction or disability of the central nervous system, and E) for examination. When a life-threatening problem is identified during the primary survey then resuscitative action should be instituted immediately.

Airway/Breathing

First, airway and adequacy of ventilation should be assessed. This is done by visualization, palpation, and auscultation. Airway patency alone does not insure adequate ventilation. Ventilation involves adequate function of lungs, chest wall and diaphragm. Life-threatening airway/breathing problems may be due to apnea, airway obstruction, open chest wounds, tension pneumothorax, and hemopneumothorax.

Signs of airway obstruction/inadequate ventilation include:

1)  Intercostal retraction

2)  Gurgling sounds

3)  Stridor

4)  Labored use of accessory muscles of respiration (face and neck)

5)  Decreased breath sounds (unilateral or bilateral)

6)  Cyanosis (late and unreliable sign)

7)  Minimal or absent chest wall motion

8)  Absence of air exchange from nose or mouth

9)  Restlessness and or anxiety

Management of life threatening airway/breathing problems might include:

1)  Airway suctioning

2)  Removal of airway obstruction

3)  Oxygen administration

4)  Intubation or tracheostomy tube placement

5)  Mechanical or manual ventilation

6)  Temporary closure of open chest wounds

7)  Thoracentesis

8)  Thoracostomy tube placement and intermittent or continuous suction /drainage

Circulation

Circulation is assessed by visualization, palpation, and auscultation. Circulatory instability may be due to hypovolemia as a result of external blood loss or concealed blood loss (loss into body cavity or limb). It may also be due to pump failure (intrinsic heart failure, arrhythmias, cardiac tamponade). The most common type of shock seen in trauma is hypovolemic shock. Shock is inadequate tissue perfusion resulting in inadequate oxygen delivery. The signs of shock are indicative of decreased tissue perfusion and sympathetic autonomic responses (Figure 1).

Figure 1  Clinical signs of shock

Pathophysiology of Hypovolemic Shock

Usually the initiating cause (in this case trauma) results in a decreased intravascular volume. As a result of the decreased intravascular volume, venous return to the heart is decreased. Decreased ventricular filling (preload) is a result of the decreased venous return. With the decreased ventricular filling we see decreased stroke volume (amount of blood ejected by the ventricle with each contraction). Cardiac output is the product of stroke volume and heart rate. Decreased stroke volume can result in decreased cardiac output. The end result is inadequate tissue perfusion and oxygenation.

Goal of Therapy

In addition to returning the cardiovascular parameters (heart rate, blood pressure, cardiac output etc.) to normal, optimizing oxygen delivery to the tissues is a major goal. To achieve this goal shock therapy must be initiated (Figure 2).

Figure 2

Therapy

Intravenous catheter(s) are placed. The placement of a jugular catheter and the measurement of central venous pressure might be beneficial in guiding fluid resuscitation. If difficulty is encountered in placing an IV catheter, consideration should be given to placing an intraosseous catheter. Absorption of fluids via the bone marrow is rapid. In addition to fluids, some drugs may be administered via this route.

Fluid resuscitation is the cornerstone of shock therapy. Our options for fluid resuscitation include crystalloids (Lactated Ringers, Normosol R, Plasmalyte 148, and Normal Saline), and Colloids (Plasma, Dextran 70, Hetastarch, Oxyglobin^� and whole blood). Initially, crystalloids are the fluid of choice in the treatment of shock. The dose is 80 - 90 ml/kg and 50 - 55 ml/kg in the dog and cat respectively (equivalent to one blood volume). It may be necessary to use 0.5 - 1.5 times the blood volume to resuscitate the patient. 75 % of the crystalloids shift from the intravascular space into the interstitial space in about thirty minutes. Colloids are better blood volume expanders, 50 - 80% of the infused volume remains in the intravascular space. Colloids should be administered when crystalloids are not improving or maintaining blood volume restoration. In addition, the appropriate colloid is given in sufficient quantities to maintain the packed cell volume above 25% and a total protein above 4.0 mg/dl. Oxyglobin^� solution is a relatively new alternative to whole blood or packed red blood cells. Oxyglobin^� is a hemoglobin-based oxygen carrying solution. It contains 13 g/dL bovine polymerized hemoglobin in a modified Lactated Ringer's solution. Oxyglobin^� is ultra-purified and stroma-free, meaning, that there is no potential for disease transmission or antigenic reaction respectively. Due to its molecular size it exerts a colloid oncotic pressure effect, which may be beneficial. The manufacturer recommended one time dose range is 10 - 30 mL/kg not to exceed a rate of 10 mL/kg/hr. The patient's condition should be monitored and the fluid given to effect. Administration of hemoglobin (either whole blood, packed RBCs or Oxyglobin^�) improves O₂ content and ultimately oxygen delivery.

Hypertonic saline (7.0% Sodium Chloride Injection USP : Sanofi Animal Health) has been recommended for use in shock therapy in cases where it is difficult to administer large volumes of fluids rapidly enough to resuscitate the patient. Hypertonic saline causes fluid shifts from the intracellular space to the extracellular (including intravascular) space resulting in improved venous return and cardiac output. Hypertonic saline may have other beneficial cardiovascular effects as well. The recommended dose range is 4 - 6 ml/kg over five minutes. Dextran 70 has been added to hypertonic saline to potentiate and sustain vascular augmentation.

Sympathomimetics, such as dopamine and dobutamine are indicated when the patient is unresponsive to vigorous fluid therapy and arterial blood pressure, vasomotor tone, and tissue perfusion have not returned to acceptable levels. These drugs support myocardial contractility and blood pressure with minimal vasoconstriction. It is suggested that if these drugs are used blood pressure monitoring is necessary. The effects of dopamine are dose dependent. At 1 - 5 mcg/kg/minute we will get the dopaminergic effect (dilate renal, mesenteric, and coronary vascular beds). Beta 1 activity (positive inotropic) is seen at a dose range of 5 - 10 mcg/kg/minute. At doses greater than 10 mcg/kg/minute alpha receptor stimulation (vasoconstriction) occurs. Dobutamine has primarily beta activity. It has minimal effect on heart rate and peripheral vascular resistance except at higher dosages. The dose range is 5 - 15 mcg/kg/minute. Sympathomimetics should not be a substitute for adequate volume restoration.

The technician should be able to calculate constant rate infusions (CRI) using the formula below (Figure 3) or a formula similar to it.

Figure 3  Formula for calculation of CRI

Dysfunction / Disability

Dysfunction/disability refers to the neurological status of the patient. This may be assessed through visualization and palpation. A cursory neuro exam is performed focusing on the patient's level of consciousness, pupillary light reflex, posture, and response to pain (superficial and/or deep).

The levels of consciousness (highest to lowest) are normal, obtunded, stupor, and comatose. These terms are used to characterize the condition of the patient but in most instances are not specific for a particular type of neural lesion. A decrease in the level of consciousness may indicate decreased cerebral oxygenation and / or perfusion or may be due to direct cerebral injury. An altered level consciousness indicates the need for immediate re-evaluation of the patient's oxygenation, ventilation and perfusion status. Pupils are normally equal in size and respond quickly to light. Progressive constriction, dilation, anisocoria with diminished pupillary light reflex in the absence of ocular trauma is indicative of neurological deterioration. It is important to differentiate between decerebrate and decerebellate rigidity. Both are characterized by extensor rigidity in all limbs and opisthotonos. However, in decerebellate rigidity the hind limbs may be flexed or extended. If decerebellate progresses to decerebrate rigidity, it indicates progression of brain stem damage. Schiff-Sherrington consist of extensor rigidity of the forelimbs an flaccid hind limbs. This posture indicates a lesion at T2-L4. It is a poor prognostic sign when a patient doesn't perceive pain. Pricking or pinching the skin tests superficial pain. Applying noxious stimuli to the toes or joint tests deep pain. In both cases the patient should show some visible discomfort.

Non-ambulatory traumatized patients should be treated as spinal trauma patients until proven otherwise. In the mean time the patient should be immobilized.

In the case of head trauma, meeting the patient's systemic needs will also help the patient neurologically. It will be necessary to avoid extremes in blood pressure (hypotension or hypertension). Hypotension has been shown to adversely effect outcome in people with head trauma. Mean arterial pressure is a major determinant in cerebral perfusion pressure (mean arterial pressure minus intercranial pressure). Maintaining a normal mean arterial pressure ensures adequate cerebral perfusion and prevents cerebral ischemia). Hypoxia can also adversely affect the head trauma patient, therefore steps should be taken to either treat or avoid hypoxia. Mannitol has been used to reduce elevated intercranial pressure and increase cerebral blood flow. Elevation of the patient's head may be helpful in reducing the intercranial pressure by enhancing venous return from the brain to the heart.

Examination

During this final phase of the primary survey a rapid whole body examination is performed. Major lacerations may be uncovered and areas of bruising noted. Areas of bruising that appear to be worsening could be indicative of active bleeding. Abdominal girth should also be noted. Abdominal distension could be due to intra-abdominal hemorrhage.

Secondary Survey

The secondary survey does not begin until the primary survey (ABCDEs) is completed, resuscitation is initiated, and the patient's ABCDEs are reassessed. The secondary survey is the timely, systematic, and directed evaluation of each body system for injury. Injuries of a lower priority are addressed following initial stabilization. A thorough head to tail physical examination and history are completed. Finally, a comprehensive plan of diagnostics and monitoring is developed and carried out.

Definitive Management

A review is made of the ancillary diagnostics that were performed (i.e. radiographs, ECG, lab data) and a management plan is developed. This plan might result in emergency surgery or temporary stabilization of fractures and continued monitoring.  

Summary

The management of a traumatized patient can be very difficult and complex. The goal is to return the patient to its owner with little or no disability. To this end an efficient and organized clinical staff is a must. The utilization of emergency protocols help to increase the teams efficiency. Prevention is the best treatment for serious trauma. When a trauma patient is presented, it is imperative to act decisively and with teamwork.