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A gene on chromosome Xq12-q13.1 that encodes ectodysplasin A, a type-II membrane protein of the tumour necrosis factor family, which forms a homotrimeric molecule involved in cell-cell signalling during the development of ectodermal tissue. It can be cleaved by furin, resulting in a secreted form.

Molecular pathology
EDA mutations cause anhidrotic ectodermal dysplasia (i.e., X-linked hypohidrotic ectodermal dysplasia).


(an?al-je'zh(e-)a) [Gr. analgesia, painlessness]
1. Absence of a normal sense of pain.
2. The relief of pain, e.g. with medications such as anesthetic drugs.
3. The administration of a pain reliever.

audio analgesia

See: audioanalgesia

analgesia algera

Spontaneous pain with loss of sensibility in a part.

continuous caudal analgesia

Analgesia to reduce the pain of childbirth. The anesthetic is injected continuously into the epidural space at the sacral hiatus.

electrical dental analgesia

Abbreviation: EDA
The treatment of oral pain or the administration of oral anesthesia with electrode pads applied to the cheeks or the oral mucosa.
See: audioanalgesia

epidural analgesia

A technique of managing pain in which narcotics are infused into the peridural space through an indwelling catheter. Administration may be at a continuous basal infusion rate or self-administered within programmed limits.


Epidurally administered medications diffuse across the dura mater, through the arachnoid and pia mater to provide pain relief, and are indicated to treat pain in the thoracic, lumbar, or sacral areas, e.g., in patients in labor or those undergoing thoracic surgeries, and the acute and chronic pain of chronic lumbosacral radiculopathy, cancer pain, phantom limb pain, pancreatic pain, and incisional pain. Epidural anesthesia can be used for surgeries such as cholecystectomy, coronary artery bypass grafting, hysterectomy, arthroplasty, or even abdominal aortic aneurysm repair. Epidural needles and catheters can be inserted at spinal levels C7 to T1 to treat patients with chronic pain symptoms or for surgeries of the arms and shoulders; from T4 to T5 for thoracic surgery; from T8 to T10 for upper abdominal surgery; and at L2 to L3 for lower abdominal surgery and labor and delivery. Drugs for epidural anesthesia include anesthetics such as lidocaine, analgesics such as morphine, or steroids such as methylprednisolone acetate. Epidural anesthesia is contraindicated in patients receiving systemic anticoagulation and antiplatelet therapy, e.g., aspirin products or NSAIDs, patients with abnormal or reduced concentrations of clotting factors, patients in hypovolemic shock, with abruptio placentae, and whenever there is evidence of active infection near the site of the insertion of the epidural catheter. Relative contraindications include history of headaches or backaches, chronic neurological disorders, and allergy to drugs being used.

Patient care

The anesthesia provider discusses the procedure, benefits, and risks with the patient and answers any questions. An informed consent form must be signed by the patient. The nurse may reinforce or clarify information as necessary and witness the patient’s signature on the consent form. Before the procedure the patient should have an IV line infusing lactated Ringer’s solution or 0.9% sodium chloride solution and should have supplemental oxygen via a nasal cannula or simple face mask. Blood pressure and oxygen saturation should be monitored throughout the procedure. The health care professional helps position the patient in the preferred sitting position with head down, shoulders slumped, and arms out in front to bend the back forward and open the vertebral spaces. Legs may be extended forward or hang over the side of the bed or table. If this position cannot be tolerated, the patient is positioned laterally with chin tucked against chest and knees in a fetal position. The patient is assisted to remain still and kept as comfortable as possible; reassurance and emotional support are provided. Once inserted, the epidural catheter is labeled according to the facility’s policy, and properly and prominently identified so that only epidural drugs are administered through it (these are pure, preservative-free medications, not the same formulation as for usual intravenous preparations of the same drug). The patient should then be assisted to a comfortable position or positioned for surgery. Administration of epidural medication and the removal of the catheter are determined by state nursing laws, which nurses must know. Epidural medications are usually administered by a certified registered nurse anesthetist or by an anesthesiologist and are managed by a staff nurse. Drugs given epidurally must be administered with a sterile technique. The dose is determined by the patient's response as the desired level of anesthesia is reached.

The patient should be assessed periodically according to the facility’s policy. His blood pressure, heart rate, respiratory rate, and oxygen saturation should be documented. The insertion site and dressing are examined periodically for bleeding or medication leakage. The patient is assessed for pain from the catheter or from the infusion and for breakthrough pain related to the surgery or for the painful condition being managed. Continuous infusion via a pump or patient-controlled analgesia pump also must be checked for correct functioning. Muscle weakness and sensory loss may be indicators of epidural bleeding and nerve impingement, which requires emergency surgery to prevent permanent tissue and nerve damage. Any problems encountered should be called to the attention of the anesthesia provider. Hypotension is commonly experienced. The patient’s IV fluid infusion rate may need to be increased dramatically to manage hypotension, or a vasoactive agent may be administered as prescribed. Respiratory distress will occur if the needle or catheter enters the subarachnoid space, causing high spinal anesthesia with increased loss of respiratory muscle function. The anesthesia provider and rapid response team should be notified immediately, and basic life support guidelines followed to maintain airway, breathing, and cardiovascular status.

The catheter may migrate into an epidural vein as a result of the patient's movement, causing epidural medication to enter the bloodstream and produce an overdose. Prevention of this complication involves slow, careful movement and repositioning by a caregiver team, with the patient providing minimal aid. If the dura mater is torn by the large needle or catheter during epidural insertion, a cerebrospinal fluid leak into the epidural space can occur. This complication should be suspected if the patient experiences severe and sudden headache when upright. The patient should be kept supine, the anesthesia provider notified, and the patient treated, which may involve administration of additional IV fluid, caffeine, analgesics, or an epidural blood patch. Infection is a rare complication: it is prevented by maintaining sterile technique throughout the insertion, management, and removal of the epidural device.


Excessive sedation, hypotension, respiratory depression, and coma may occur if patients receiving epidural analgesia are also given other central nervous system depressant drugs.

hypnotic analgesia

The use of hypnotic suggestion to alter a patient's perception of noxious sensations, e.g., the pain of childbirth or coronary artery disease.

infiltration analgesia

Anesthesia produced in a local area by injecting an anesthetic agent into operative sites or wounds.

interpleural analgesia

The introduction of pain-relieving drugs into the space between the visceral and parietal pleura, e.g., to relieve the pain of thoracotomy. It is also known, incorrectly, as intrapleural anesthesia.
Synonym: interpleural block; interpleural blockade

intrathecal analgesia

The injection of pain-relieving medications into the subarachnoid space. It is used to control severe pain, e.g., the pain of vertebral compression fracture or metastatic bone disease.
Synonym: intrathecal anesthesia

paretic analgesia

Complete analgesia of an upper limb in conjunction with partial paralysis.

patient-controlled analgesia

Abbreviation: PCA
A drug administration method that permits the patient to control the rate of drug delivery for the control of pain. It is usually accomplished by the use of an infusion pump.

Patient care

An adult or child who is cognitively and physically able to use the equipment and who understands that pressing a button can result in pain relief is an appropriate candidate to administer his own pain medications when they are needed. Safety is secured because opioid and opiate drugs, the analgesics most often administered by PCA, cause sedation before respiratory depression. A sedated patient will drop rather than push the PCA button, preventing delivery of more drug and respiratory concerns. This safeguard can be circumvented when some unauthorized person, well-meaning though that person may be, presses the PCA button for the patient. Health care professionals should advise patients, family members, and other visitors that the PCA should be used only by the patient. When patients are unable to use PCA appropriately, a family member or nurse may be authorized to manage the system. This primary pain manager must be taught how to assess for pain and its relief, using an appropriate method for the specific patient, and how to recognize and manage the adverse effects of opioids and opiates (nausea, vomiting, constipation, sedation, and respiratory depression). The manager also needs to know how to assess the patient’s sedation level using a sedation scale, such as the following: S = sleep, easy to arouse (awaken patient to determine arousability before administering a bolus); 1 = awake and alert (acceptable, may administer bolus); 2 = slightly drowsy, easily aroused (acceptable, may administer bolus); 3 = frequently drowsy, arousable, drifts off during conversation (unacceptable, notify primary nurse or health care provider); 4 = somnolent, minimal, or no response to physical stimulation (unacceptable, notify primary care provider immediately). In some cases, a secondary or even tertiary pain manager should be appointed for those times when the primary manager needs a respite. Nurse-activated dosing is appropriate for patients who have no family members who can manage pain and is useful in the intensive care unit, where the patient is usually critically ill. Health care agencies should develop criteria for selecting appropriate patients for PCA, family-controlled analgesia, and nurse-activated dosing. Patients, family members, and visitors should be taught about proper PCA use. If the patient’s pain appears to be unrelieved, the patient or concerned visitor should notify the patient’s primary nurse. Patients receiving PCA should be monitored at least every 2 hr for the first 24 hr, assessing vital signs, pain level, and sedation level. If sedation is at a level of 3, the opioid or opiate dose should be decreased and the basal infusion (if in use) stopped; monitoring should be increased until the sedation level is 2 or lower; and the patient’s or pain manager’s ability to manage the pain safely should be evaluated. If high sedation levels are found to be related to the inability to safely manage the pain using PCA, an alternative approach to pain management should be used.

perineural analgesia

The injection of a pain-relieving drug, such as bupivacaine or lidocaine, around or near a nerve, to induce regional anesthesia.
Synonym: perineural anesthesia; perineural block; perineural blockade

preemptive analgesia

The administration of anesthetic before surgery in an attempt to abort postoperative pain and disability.

electrical dental analgesia

Abbreviation: EDA
The treatment of oral pain or the administration of oral anesthesia with electrode pads applied to the cheeks or the oral mucosa.
See: audioanalgesia
See also: analgesia


(an?es-the'zha) [ ¹an- + esthesi- + -ia]
1. Partial or complete loss of sensation, with or without loss of consciousness, as a result of disease, injury, or administration of an anesthetic agent, usually by injection or inhalation.

Patient care

Preoperative:Before induction of anesthesia, contact lenses, hearing aids, dentures (partial plates as well as full sets), wristwatches, and jewelry are removed. The anesthesiologist or nurse-anesthetist interviews and examines the patient briefly, assessing general respiratory and cardiovascular health. The patient is questioned regarding compliance with prescribed preoperative fasting. The American Society of Anesthesiologists Guidelines recommend minimum fasting as follows: 2 hours for clear liquids, 4 hours for breast milk, 6 hours for formula, nonhuman milk, or a light meal (tea and toast), and 8 hours for a regular meal (easily remembered as “2-4-6-8”). These guidelines may be modified by individual surgeons for particular patients and their conditions. Baseline vital signs are assessed and recorded. An ECG, CBC, serum chemistries, and urinalysis are ordered for many general surgeries unless results of recent tests are available. Allergies, previous surgeries, and any untoward responses to anesthetic agents are reviewed, along with any special patient restrictions. If a menstruating female is using a tampon, it is removed and replaced with a perineal pad. Depending on the patient’s health status and the planned procedure, nasal oxygen, monitoring electrodes, and graduated compression stockings are applied. An intravenous route is established, and, after determining that the proper informed consent form has been signed, induction relaxation medication is administered.

Postoperative: During emergence from general anesthesia, the patient's airway is protected and vital signs monitored. Level of consciousness, status of protective reflexes, motor activity, and emotional state are evaluated. The patient is reoriented to person, place, and time; this information is repeated as often as necessary. For patients who have received ketamine, a quiet area with minimal stimulation is provided. Children may be disoriented, hallucinatory, or physically agitated as they emerge from general anesthesia. A security toy and the presence of parents may help them maintain orientation and composure. The temperatures of elderly patients should be monitored, heat loss prevented, and, as necessary, active rewarming provided. The mental status and level of consciousness of each patient should be carefully observed for changes. Patients' eyeglasses and hearing aids are returned to them as soon as possible. Before nerve block anesthesia, an intravenous infusion is established to ensure hydration. The patient is protected with side rails and other safety measures, and the anesthetized body part is protected from prolonged pressure. For regional anesthesia, sympathetic blockade is assessed by monitoring sensory levels along with vital signs (the block will wear off from head to toe, except for the sacrum and perineum, which wear off last). In obstetrics, maternal hypotension results in diminished placental perfusion and potential fetal compromise; therefore, hydration and vital signs must be closely monitored. Outcomes indicating returned sympathetic innervation include stable vital signs and temperature, ability to vasoconstrict, perianal pinprick sensations (“anal wink”), plantar flexion of the foot against resistance, and ability to sense whether the great toe is flexed or extended. The patient must tolerate oral fluids (unless restricted) and urinate before discharge. If the patient is at risk for postanesthesia headache, oral or intravenous hydration is administered, and the patient is encouraged to remain flat in bed. Prescribed analgesics are administered, and comfort measures, breathing exercises, abdominal support, and position changes are provided.

2. The science and practice of anesthesiology.

basal anesthesia

A level of unconsciousness just above the level of complete surgical anesthesia. The patient does not respond to verbal stimuli but does react to noxious stimuli (e.g., a pinprick). Basal anesthesia may be combined with local or regional anesthesia in some forms of surgery.

block anesthesia

A regional anesthetic injected into a nerve (intraneurally) or immediately around it (paraneurally). Synonym: conduction anesthesia; neural anesthesia

bulbar anesthesia

Anesthesia produced by a lesion of the pons.

caudal anesthesia

Anesthesia produced by insertion of a needle into the sacrococcygeal notch and injection of a local anesthetic into the epidural space.
Synonym: caudal catheter

central anesthesia

Pathological anesthesia due to a lesion of the central nervous system.

closed anesthesia

A method of inhalation anesthesia in which exhaled gases are rebreathed. This requires appropriate treatment of the exhaled gas to absorb the expired carbon dioxide and to replenish the oxygen and the anesthetic.

conduction anesthesia

Block anesthesia

crossed anesthesia

Anesthesia of the side opposite to the site of a central nervous system lesion.

dissociative anesthesia

A type of anesthesia marked by catalepsy, amnesia, and marked analgesia. The patient experiences a strong feeling of dissociation from the environment.

anesthesia dolorosa

1. Pain or reduced sensation limited to either the occipital nerve or a branch of the trigeminal nerve.
2. Pain in an anesthetized zone, as in thalamic lesions.

electric anesthesia

Anesthesia induced with electric current.

electronic dental anesthesia

Abbreviation: EDA
In dentistry, the use of low levels of electric current to block pain signals en route to the brain. The patient controls the current through a handheld control. The current creates no discomfort and, unlike local anesthesia, leaves no numbness to wear off once the dental work is completed.
See: audioanalgesia; patient-controlled analgesia

endotracheal anesthesia

Anesthesia in which gases are administered via a tube inserted into the trachea.
Enlarge picture

epidural anesthesia

Anesthesia produced by injection of a local anesthetic into the peridural space of the spinal cord. Synonym: peridural anesthesia See: illustration

ethylene anesthesia

Ethylene given as a combination of oxygen 20%, cyclopropane 10%, and ethylene 70%. Because it is a rather weak anesthetic, volatile and inflammable, it is rarely, if ever, used.

general anesthesia

Anesthesia that produces complete loss of consciousness. General anesthesia is a medically controlled coma. Patients under general anesthesia do not respond to words or touch and cannot breathe spontaneously or protect their airway.

Gwathmey's anesthesia

See: Gwathmey, James

hypotensive anesthesia

Anesthesia during which the blood pressure is lowered.

hypothermic anesthesia

General anesthesia during which the body temperature is lowered.

hysterical anesthesia

Bodily anesthesia occurring in conversion disorders.

inadequate anesthesia

Anesthesia in which the patient is not comfortably sedated or relieved of pain. Common findings are spontaneous eye opening, grimacing, swallowing, or sweating. Vital signs may reveal unexpected hypertension or tachycardia.

infiltration anesthesia

, infiltrative anesthesia
Local anesthesia produced by an injection of an anesthetic directly into the tissues.

inhalation anesthesia

General anesthesia produced by the inhalation of vapor or gaseous anesthetics, e.g., ether, nitrous oxide, and methoxyflurane.

insufflation anesthesia

Instillation of gaseous anesthetics into the inhaled air.

intrapleural anesthesia

See: interpleural analgesia

intrathecal anesthesia

Intrathecal analgesia.

intratracheal anesthesia

Anesthesia administered through a catheter advanced through the upper airway and vocal cords into the trachea.

local anesthesia

The pharmacological inhibition of nerve impulses in a body part. It is typically used to facilitate treatment of a small lesion or laceration or to perform minor surgery. Commonly used agents include lidocaine, bupivacaine, or novocaine. All local anesthetic agents work by decreasing the flow of sodium ions into nerve cells, blocking the action potential of the cells.
See: block anesthesia; infiltration anesthesia

mixed anesthesia

General anesthesia produced by more than one drug, such as propofol for induction, followed by an inhaled drug for maintenance of anesthesia.

neural anesthesia

Block anesthesia.

neuraxial anesthesia

Caudal, epidural, or spinal anesthesia.

open anesthesia

Application, usually by dropping, of a volatile anesthetic agent onto gauze held over the nose and mouth.

paravertebral anesthesia

Injection of a local anesthetic at the roots of spinal nerves.

peridural anesthesia

Epidural anesthesia.

perineural anesthesia

Perineural analgesia.

peripheral anesthesia

Local anesthesia produced when a nerve is blocked with an appropriate agent.

primary anesthesia

The first stage of general anesthesia, before unconsciousness.

pudendal anesthesia

Local anesthesia used primarily in obstetrics (e.g., to facilitate pelvic surgery or childbirth). The pudendal nerve on each side, near the spinous process of the ischium, is blocked.

rectal anesthesia

General anesthesia produced by introduction of an anesthetic agent into the rectum, used esp. in managing pediatric patients.

refrigeration anesthesia

An obsolete synonym for cryoanesthesia.

regional anesthesia

Nerve or field blocking, causing loss of sensation in a dermatome innervated by a specific nerve.
See: block anesthesia; infiltration anesthesia

saddle block anesthesia

Anesthesia produced by introducing the anesthetic agent into the fourth lumbar interspace to anesthetize the perineum and the buttocks.

segmental anesthesia

Anesthesia due to a pathological or surgically induced lesion of a nerve root.

sexual anesthesia

Loss of genital sensation, with accompanying secondary sexual dysfunction.
Enlarge picture

spinal anesthesia

1. Anesthesia resulting from disease or injury to conduction pathways of the spinal cord.
2. Anesthesia produced by injection of anesthetic into the subarachnoid space of the spinal cord.

Side effects

Common adverse reactions to spinal anesthesia include backache, bradycardia, headache, lowered blood pressure, and urinary retention.

Synonym: subarachnoid block See: illustration

splanchnic anesthesia

Anesthesia produced by injection of an anesthetic into the splanchnic ganglion.

stages of anesthesia

The distinct series of steps through which anesthesia progresses. The first stage of pharmacologically induced general anesthesia includes preliminary excitement until voluntary control is lost. Because hearing is the last sense to be lost, the conversation of operating room staff should be guarded during this stage. The second stage consists of loss of voluntary control. In the third stage there is entire relaxation, no muscular rigidity, and deep regular breathing.

surgical anesthesia

Depth of anesthesia at which relaxation of muscles and loss of sensation and consciousness are adequate for the performance of surgery.

tactile anesthesia

Loss of sense of touch.

topical anesthesia

Local anesthesia induced by application of an anesthetic directly onto the surface of the area to be anesthetized.

total intravenous anesthesia

Abbreviation: TIVA
The sole use of intravenous drugs without any inhalational agents for operative or procedural anesthesia.

traumatic anesthesia

Loss of sensation resulting from nerve injury.

tumescent anesthesia

The injection of large volumes of diluted lidocaine, bicarbonate, and epinephrine subcutaneously for use in local anesthesia. This procedure is most often used before liposuction to limit blood loss and pain.

twilight anesthesia

State of light anesthesia.
See: twilight sleep

electronic dental anesthesia

Abbreviation: EDA
In dentistry, the use of low levels of electric current to block pain signals en route to the brain. The patient controls the current through a handheld control. The current creates no discomfort and, unlike local anesthesia, leaves no numbness to wear off once the dental work is completed.
See: audioanalgesia; patient-controlled analgesia
See also: anesthesia
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