Analgesia

Analgesia: Excerpt from Nursing: Interpreting Signs and Symptoms

Analgesia, the absence of sensitivity to pain, is an important sign of central nervous system disease, commonly indicating a specific type and location of spinal cord lesion. It always occurs with loss of temperature sensation (thermanesthesia) because these sensory nerve impulses travel together in the spinal cord. It can also occur with other sensory deficits—such as paresthesia, loss of proprioception and vibratory sense, and tactile anesthesia—in various disorders involving the peripheral nerves, spinal cord, and brain. When accompanied only by thermanesthesia, analgesia points to an incomplete lesion of the spinal cord.

Analgesia can be classified as partial or total below the level of the lesion and as unilateral or bilateral, depending on the cause and level of the lesion. Its onset may be slow and progressive with a tumor or abrupt with trauma. Transient in many cases, analgesia may resolve spontaneously.

Action stat!

Suspect spinal cord injury if the patient complains of unilateral or bilateral analgesia over a large body area, accompanied by paralysis. Immobilize his spine in proper alignment, using a cervical collar and a long backboard, if possible. If a collar or backboard isn't available, position the patient in a supine position on a flat surface and place sandbags around his head, neck, and torso. Use correct technique and extreme caution when moving him to prevent exacerbating spinal injury. Continuously monitor respiratory rate and rhythm, and observe him for accessory muscle use because a complete lesion above the T6 level may cause diaphragmatic and intercostal muscle paralysis. Have an artificial airway and a handheld resuscitation bag on hand, and be prepared to initiate emergency resuscitation measures in case of respiratory failure.

History and physical examination

After you're satisfied that the patient's spine and respiratory status are stabilized—or if the analgesia isn't severe and isn't accompanied by signs of spinal cord injury—perform a physical examination and baseline neurologic evaluation. First, take the patient's vital signs and assess his level of consciousness. Then test pupillary, corneal, cough, and gag reflexes to rule out brain stem and cranial nerve involvement. If the patient is conscious, evaluate his speech, gag reflex, and ability to swallow.

If possible, observe the patient's gait and posture and assess his balance and coordination. Evaluate muscle tone and strength in all extremities. Test for other sensory deficits over all dermatomes (individual skin segments innervated by a specific spinal nerve) by applying light tactile stimulation with a tongue depressor or cotton swab. Perform a more thorough check of pain sensitivity, if necessary, using a pin. (See Testing for analgesia, pages 32 and 33.)

Test temperature sensation over all dermatomes, using two test tubes—one filled with hot water, the other with cold water. In each arm and leg, test vibration sense (using a tuning fork), proprioception, and superficial and deep tendon reflexes. Check for increased muscle tone by extending and flexing the patient's elbows and knees as he tries to relax. Focus your history taking on the onset of analgesia (sudden or gradual) and on any recent trauma—a fall, sports injury, or automobile accident. Obtain a complete medical history, noting especially any incidence of cancer in the patient or his family. Obtain a complete drug history.

Medical causes

Anterior cord syndrome.With anterior cord syndrome, analgesia and thermanesthesia occur bilaterally below the level of the lesion, along with flaccid paralysis and hypoactive deep tendon reflexes.

Central cord syndrome.Typically, analgesia and thermanesthesia occur bilaterally in several dermatomes, in many cases extending in a capelike fashion over the arms, back, and shoulders. Early weakness in the hands progresses to weakness and muscle spasms in the arms and shoulder girdle. Hyperactive deep tendon reflexes and spastic weakness of the legs may develop. If the lesion affects the lumbar spine, hypoactive deep tendon reflexes and flaccid weakness may persist in the legs.

With brain stem involvement, additional findings include facial analgesia and thermanesthesia, vertigo, nystagmus, atrophy of the tongue, and dysarthria. The patient may also have dysphagia, urine retention, anhidrosis, decreased intestinal motility, and hyperkeratosis.

Spinal cord hemisection.Contralateral analgesia and thermanesthesia occur below the level of the lesion. In addition, loss of proprioception, spastic paralysis, and hyperactive deep tendon reflexes develop ipsilaterally. The patient may also experience urine retention with overflow incontinence.

Other causes

Drugs.Analgesia may occur with use of a topical or local anesthetic, although numbness and tingling are more common.

Nursing considerations

▪ Prepare the patient for spinal X-rays and imaging studies, and maintain spinal alignment and stability during the tests.

▪ Focus your care on preventing further injury to the patient because analgesia can mask injury or developing complications.

▪ Prevent formation of pressure ulcers through meticulous skin care and frequent repositioning, especially when significant motor deficits impair the patient's mobility.

▪ Guard against scalding by testing the patient's bath water temperature before he bathes.

Patient teaching

▪ Advise the patient to test bath water temperature at home using a thermometer or a body part with intact sensation.

▪ Explain all tests and procedures.

▪ Teach the patient about the diagnosis, once established, and the treatment plan.

Pictures

Book Source Details

• Book Title: Nursing: Interpreting Signs and Symptoms
• Author(s): Springhouse
• Year of Publication: 2007
• Copyright Details: Nursing: Interpreting Signs and Symptoms, Copyright © 2007 Lippincott Williams & Wilkins.

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Copyright notice for book excerpts: Copyright © 2008 Lippincott Williams & Wilkins. All rights reserved.

More About This Book: Title: Nursing: Interpreting Signs and Symptoms Authors: Springhouse Publisher: Lippincott Williams & Wilkins Copyright: 2007 ISBN: 1-58255-668-7

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