|
|
Many organs have a dual autonomic innervation. Therefore it is possible that an interruption of the supply from one ANS division leaves the input from the other division acting unopposed.
Unopposed action of the PaNS supply to the pupil of the eye can occur Horner's Syndrome. This condition arises when there is a lesion of the cervical sympathetic ganglion supplying the eye head and neck.
The features Horner's syndrome include: constriction of the pupil, drooping of the eyelid, slight retraction of the eyeball within the orbit, and loss of sweating on the affected side of the head and neck.
A severe lesion right at the bottom of the spinal cord in an area known as the cauda equina affects bladder and bowel function as a result of damage to the sacral parasympathetic outflow. The detrusor muscle of the bladder is affected and reflex connection no longer occurs in response to distension. The bladder wall itself has a certain amount of elasticity, and as pressure mounts the elasticity forces some urine into the urethra. However, the unopposed sympathetic supply to the sphincter muscle keeps it contracted and closed, and dribbling incontinence occurs. A similar situation arises with regard to the bowel and anal sphincter. A lesion of the spinal cord itself, in which voluntary control of the bowel and bladder is affected, but which does not affect the parasympathetic outflow leads to an automatic bladder once spinal shock has worn off. Such patients no longer have any voluntary aspect to the control of the bladder and are therefore prone to "accidents". Such lesions can affect the sympathetic innervation to the skin. Initially during spinal shock, the skin below the level of the lesion is dry, pale and cool but at a later stage profuse sweating in the affected area is common and can be provoked by stimulus of the such as stroking.
This operation is possible due to the anatomy of the sympathetic division of the ANS, since the paravertebral chain of ganglia are rendered relatively accessible for surgical intervention. There are several reasons for considering such an operation.
Hyperhidrosis or profuse and uncontrollable sweating due to a congenital disorder can be treated in this way and the benefits to the patient in terms of being able to function normally in society far outweigh any other health questions.
To improve the blood flow to peripheral areas in patients whose physiological integrity is threatened by vasospasm.
To reduce blood pressure more generally in hypertension
In chronic pain for causalgia (burning pain in the cutaneous distribution of an injured peripheral nerve)
For phantom limb pain
It is important to note that with the increased knowledge available today, this operation is carried out only as a last resort, since less drastic and non-invasive methods of opposing the action of the sympathetic nervous system are now available.
For example vascular effects of sympathetic stimulation can be opposed with drugs having very specific effects upon the blood vessels.
The adaptive (coping) nature of the sympathetic nervous response and the accompanying secretion of adrenaline and noradrenaline from the adrenal medulla can be seen by nurses in the signs and symptoms of patients in shock following accidental or surgical trauma involving blood or fluid loss. Together, the responses to sympathetic nervous activity function to maintain the Blood Pressure and hence bloodflow to the vital organs - the brain and heart. This response is crucial to survival and occurs largely through an increase in heart rate and contractility and because vasoconstriction occurs in non-vital areas such as the skin (causing pallor) and gut, diverting blood to the vital organs.
It is only if homeostasis is not restored and vasoconstriction continues that the response becomes non-adaptive and irreversible shock ensues.
Shock can be defined as a dynamic syndrome in which there is inadequate tissue and organ perfusion. This inadequate perfusion seriously reduces the delivery of oxygen and other essential substances to a level below that required for normal cellular function. Shock is associated with very severe stress. Usually, but not always, the stressor is predominantly physiological in nature, e.g. trauma.
The signs of shock include the signs of sympathetic nervous system arousal. Such arousal is part of the physiological response to a stressor which will restore homeostasis if the response is successful. If the physiological response is unsuccessful the condition becomes progressive. In the absence of effective treatment for progressive shock, irreversible shock occurs and death ensues.
Signs of shock are not identical with those of sympathetic nervous arousal but are more complex since they include signs associated with the impact of the stressor upon the body.
Therefore the signs of shock are a result of a combination of :
It is important for nurses to recognise the early signs of shock. Frequently the nurse will be very aware of the risk of shock occurring in relation to a patient who, for example, has had a road traffic accident. However, there are occasions when shock occurs in individuals not apparently at risk (e.g. after a minor operation) and it is essential for the condition to be recognised so that appropriate action can be taken.
In compensated shock the vital signs (temperature, pulse, respiration and blood pressure) may not reveal any deviation from normal and in such cases the clinical signs assume greater importance. Development of the ability to recognise the clinical signs of early shock through knowledge and experience is important in nursing. Part ot this judgement comes from understanding of the conditiom under which shock can occur it is also important to recognise that some individuals are more vulnerable than others even though the same of degree of trauma has been sustained. A person is predisposed to anxiety, the very young and the elderly all fall into the ctegory of those more at risk of succumbing to shock.
The clinical signs of early shock are as follows:
Last updated on Wednesday, 07 April 1999 11:06 +0100
