Neurogenic Shock - Definition, Symptoms, Causes, Treatment
What is Neurogenic Shock?
Neurogenic shock is a type of medical shock that resulted from a disruption in the sympathetic outflow leading to unimpeded vagal tone or the control of the autonomic nervous system over vasoconstriction. Neurogenic shock occurs following a spinal cord injury, particularly involving the region of T6 and above where a disconnection occurred between the brain and the autonomic nervous system.
Shock is a medical condition characterized by a disruption in the blood flow throughout the body as a result of illness or injury. It is a life-threatening condition that requires an immediate medical attention or a medical emergency to prevent irreversible tissue damage or possibly death of the patient. There are various types of shock and neurogenic shock is regarded as the most difficult to manage often as a result of irreversible tissue damage.
Neurogenic shock primarily involves the spinal cord which is a component of the central nervous system and works together with the brain. The main function of the spinal cord is to transmit the neural signals to and from the brain and the rest of the body. The spinal cord is composed of nerves which are bundled and grouped together. Ascending tract is a bundle of nerve in the spinal cord that carries information from the rest of the body towards the brain. The Descending tract on the other hand is a bundle of nerves in the spinal cord that carries information from the brain down to the rest of the body to initiate movement and body functions.
Neurogenic shock is not to be confused with spinal shock. Spinal shock is generally temporary and which usually lasts for a day or for a couple of days in the absence of sensory and motor tone that is temporary as well. Neurogenic shock on the other hand lingers for several days to a few weeks and which can result to loss of muscle tone as a consequence of muscle disuse. Neurogenic shock may also occur with either a complete or incomplete cord lesion and the severity of the symptoms depend on the level of the spinal cord affected. The higher the level of affection, the more severe symptoms will be exhibited.
Signs and Symptoms
Neurogenic shock is characterized by hypotension and bradycardia as its primary clinical manifestation which usually occur following an injury in the spinal cord.
Hypotension or low blood pressure is the consequence of a reduced systemic vascular resistance that resulted to blood collecting within the extremities thus the deficiency in the sympathetic tone. The injury in the spinal cord may result to the inability of the blood vessels to constrict leading to a decrease in the blood pressure as a response to the alteration in the autonomic nervous system.
Bradycardia is one of the key signs of neurogenic shock. In spinal cord injury causes injury to the nerves which in turn causes the walls of the blood vessels to relax thus slowing the heart rate. Bradycardia in spinal cord injury is also found to be aggravated by hypoxia or the inadequacy in the blood supply. Bradycardia is characterized by a resting heart rate of below 60 beats per minute and which could go lower in neurogenic shock.
Hypothermia or the excessive drop in the body temperature may also occur in neurogenic shock. The injury in the spinal cord may result in the loss of the sympathetic tone which in turn can result to the inability to redirect the blood flow to the core circulation thus the excessive heat loss and a drop in body temperature. Hypothermia is characterized by warm limbs with the rest of the body cold to touch and the patient may feel very cold.
Other symptoms of shock include the following:
- A rapid and deep shallow breathing
- Difficulty breathing
- Cold and clammy skin
- Pale skin appearance
- Nausea and vomiting
- Dizziness and lightheadedness
- Rapid and weak pulse
- Weakness is experienced as a result of insufficiency in the blood supply
In severe state of neurogenic shock, the symptoms may also be accompanied with the following symptoms:
- Blank stares or the eyes staring at nothing
- Change in mental state or confusion and disorientation
- Unresponsive to stimuli
- Bluish discoloration of the lips and fingers which signify a deprivation of oxygen in the body
- Low urine output or urine may cease
- Excessive sweating
- Significant chest pain
Spinal cord injury is the primary cause of neurogenic shock. Neurogenic shock immediately follows after a spinal cord injury has occurred. The clinical manifestations are the result of a disruption in the sympathetic outflow that resulted to the unopposed vagal tone.
Spinal cord injury may occur with a complete or an incomplete cord lesion in which neurogenic shock will potentially exist. Spinal cord injury is defined as damage in any part of the spinal cord including damage to the nerves at the end of the spinal canal.
The common cause of neurogenic shock includes the following:
- Injury or trauma to the spinal cord either blunt or penetrating or which may be caused by a dislocation, rotation and over extension or flexion of the cord. Trauma to the spinal cord may also occur as a result of sport injuries, vehicular accidents, falls and accidents, stab wound and gunshot wound.
- Neurogenic shock may also occur as a result of regional anesthesia that is improperly administered.
- Drugs and medications that can affect the autonomic nervous system may also result in neurogenic shock.
Assessing the general condition of the patient is the initial step in managing neurogenic shock. The goal of treatment is to stabilize the patient and prevent any irreversible tissue damage including revival of the patient.
The patient under neurogenic shock must be carefully assessed of their general condition giving importance to airway pattern and breathing including the circulation. Neurogenic shock is potentially a life-threatening situation that requires a medical emergency to preserve the life of the patient.
Spinal immobilization is necessary to prevent further spinal cord damage. Arterial blood pressure should be given immediate attention through administration of IV fluids to restore the mean pressure. Dopamine and other inotropic agents may be infused in case of inadequate fluid resuscitation.
Severe bradycardia can be managed with IV infusion of atropine given 0.5mg to 1 mg every 5 minutes for a total dosage of 3.0 mg or a pacemaker if necessary. High dosage of methylprednisolone on the other hand may be given within 8 hours following the onset of neurogenic shock in cases where neurological deficit has already been present. Immediate transfer to the nearest hospital is necessary once the patient has been stabilized for further treatment and to further ensure the safety of the patient including life preservation.