Professor, Geisinger Commonwealth School of Medicine
This usually involves the small joints of the hands and feet allergy treatment machine generic 4 mg aristocort visa, the large joints of the legs allergy medicine diphenhydramine purchase aristocort 4mg line, or some combination of both allergy testing jersey channel islands discount aristocort 4 mg. Although symptoms are usually attributed to histamine release from mast cells, histamine 1 and 2 (H1 and H2) receptor antagonists are not always protective. This suggests that vasoactive substances other than histamine (such as prostaglandins) may be involved. Management of anesthesia is influenced by the possibility of intraoperative mast cell degranulation and anaphylactoid reaction. Although the intraoperative period is usually uneventful, there are reports of life-threatening anaphylactoid reactions with even minor surgical procedures, which emphasizes the need to have resuscitation drugs such as epinephrine immediately available. Preoperative administration of H1- and H2-receptor antagonists may be considered to decrease the clinical response to histamine release. However, these drugs do not interfere with the actual release of histamine from mast cells. Cromolyn sodium does inhibit mast cell degranulation and may decrease the risk of bronchospasm. Some recommend preoperative skin testing of anesthesiarelated drugs to help define which anesthetics would provoke mast cell degranulation. Monitoring serum tryptase concentration during the perioperative period may be useful for detecting the occurrence of mast cell degranulation. Episodes of profound hypotension have been observed with administration of radiocontrast media to patients with mastocytosis. Therefore, it is prudent to pretreat these patients with H1- and H2-histamine receptor antagonists and a glucocorticoid before procedures involving contrast dye. Atopic Dermatitis Atopic dermatitis is the cutaneous manifestation of the atopic state. It is characterized by dry, scaly, eczematous, pruritic patches on the face, neck, and flexor surfaces of the arms and legs. Systemic antihistamines are effective in decreasing pruritus, and corticosteroids may be indicated for short-term treatment of severe cases. Pulmonary manifestations of the atopic state, such as asthma, hay fever, otitis media, and sinusitis may influence anesthetic management. In most people, the cause cannot be determined and the lesions resolve spontaneously or after administration of antihistamines. With physical urticaria, physically stimulating the skin causes the formation of local wheals, itching, and, in some cases, angioedema. Chronic urticaria is characterized by circumscribed wheals and localized areas of edema produced by extravasation of fluid through blood vessel walls. They are usually intensely pruritic, can be found anywhere on hairless or hairy skin, and last less than 24 hours. Wheals lasting longer than 24 hours raise the possibility of other diagnoses, including urticarial vasculitis. Chronic urticaria affects approximately twice as many women as men and often follows a remitting and relapsing course, with symptoms typically increasing at night. Angioedema is urticaria involving the mucous membranes, particularly those of the mouth, pharynx, and larynx. When they are stimulated by certain nonimmunologic events or by immunologic factors (drugs, inhaled allergens), storage granules in these cells release histamine and other vasoactive substances such as bradykinin.
It is important to have patients awaken with little reaction to the presence of the endotracheal tube allergy medicine libido order discount aristocort on line. Intraoperative use of narcotics and other drugs that suppress tracheal reflexes allergy medicine japan cheap aristocort 4mg without a prescription, such as lidocaine allergy symptoms breastfed baby buy aristocort 4mg with visa, may aid in attenuating the physiologic responses to the presence of the tube and facilitate optimal timing of extubation. However, it must be appreciated that the local anesthetic lidocaine also has general anesthetic properties and can produce central nervous system depression. If consciousness was depressed preoperatively or new neurologic deficits are anticipated as a result of the surgery, it may be best to delay tracheal extubation until return of airway reflexes is confirmed and spontaneous ventilation is sufficient to prevent carbon dioxide retention. Other causes of delayed emergence from anesthesia include residual neuromuscular block, residual effects of drugs with sedative effects. Following general anesthesia, a preexisting neurologic deficit may be exacerbated by the sedative effects of anesthetic drugs, which makes a subtle preoperative deficit appear more severe. This differential awakening is thought to be due to increased sensitivity of injured neurons to the depressant effects of anesthetic agents. Often, these deficits will disappear and neurologic function will return to its baseline state with time. Any persistent new deficit that does not quickly resolve must be further investigated. Craniotomy to remove a supratentorial tumor is usually performed with the patient in the supine position with the head elevated 10 to 15 degrees to facilitate cerebral venous drainage. Infratentorial tumors have more unusual patient positioning requirements and may be performed with the patient in the lateral, prone, or sitting position. The sitting position deserves special attention since it has a variety of implications for management of anesthesia. The sitting position is often used for exploration of the posterior cranial fossa, and it may be employed to resect intracranial tumors, clip aneurysms, decompress cranial nerves, or implant electrodes for cerebellar stimulation. In addition, it may be used for surgery on the cervical spine and posterior cervical musculature. These advantages are offset by the decreases in systemic blood pressure and cardiac output produced by this position, and the potential hazard of venous air embolism. For these reasons, the lateral or prone position is often selected as an alternative. However, as long as no contraindication to the sitting position exists, such as a patent foramen ovale, the outcome of patients undergoing surgery in the sitting position is similar or superior to that of patients placed in other positions. This is generally accomplished by measuring blood pressure via an intraarterial catheter and referencing the pressure transducer to the vertical height of the external auditory meatus, which approximates the position of the circle of Willis. Lack of correction for hydrostatic pressure may put the patient at undue risk of cerebral hypoperfusion, since the measured systemic blood pressure, but not necessarily the true pressure at the level of the brain, will be greater if the transducer is referenced at the level of the heart. Venous air embolism is a potential hazard whenever the operative site is above the level of the heart, so that pressure in the exposed veins is subatmospheric. Although this complication is most often associated with neurosurgical procedures, venous air embolism may also occur during operations involving the neck, thorax, abdomen, and pelvis and during open heart surgery, repair of liver and vena cava lacerations, obstetric and gynecologic procedures, and total hip replacement. Patients undergoing intracranial surgery are at increased risk not only because the operative site is above the level of the heart but also because veins in the skull may not collapse when cut, owing to their attachment to bone or dura. Indeed, the cut edge of cranial bone, including that associated with burr holes, is a common site for the entry of air into veins.
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The standard electroencephalogram is a sensitive indicator of inadequate cerebral perfusion during carotid cross-clamping allergy shots given to cats purchase aristocort 4mg, and perioperative neurologic complications correlate with intraoperative electroencephalographic changes indicating cerebral ischemia allergy medicine non antihistamine buy generic aristocort canada. However allergy forecast oregon cheap aristocort 4mg on line, the utility of electroencephalographic monitoring during carotid endarterectomy is limited by several factors: (1) electroencephalography may not detect subcortical or small cortical infarcts, (2) false-negative results are not uncommon (patients with previous strokes or transient ischemic attacks have a high incidence of false-negative test results), and (3) the electroencephalogram can be affected not only by cerebral ischemia but also by changes in temperature, blood pressure, and depth of anesthesia. Somatosensory-evoked potential monitoring can detect specific changes produced by decreased regional cerebral blood flow, but it can be difficult to determine whether these changes are due to anesthesia, hypothermia, changes in blood pressure, or cerebral ischemia. Stump pressure (internal carotid artery back pressure) is a poor indicator of the adequacy of cerebral perfusion. Transcranial Doppler ultrasonography allows continuous monitoring for blood flow velocity and the occurrence of microembolic events. It can be used to determine the need for shunt placement, to recognize shunt malfunction, and to manage postoperative hyperperfusion. In situations in which general anesthesia is chosen and cerebral perfusion monitoring is unavailable, an alternative approach is to insert shunts in all patients, but placement of the shunt can itself predispose to an increased embolic load. Overall, awake neurologic assessment is the simplest, most cost-effective, and most reliable method of cerebral function monitoring during carotid endarterectomy. Hypertension is frequently observed during the immediately postoperative period, often in patients with co-existing essential hypertension. The increase in blood pressure often reaches a maximum 2 to 3 hours after surgery and may persist for 24 hours. Hypertension should be treated to avoid the hazards of cerebral edema, myocardial ischemia, and hematoma formation. The incidence of new neurologic deficits is increased threefold in patients who are hypertensive postoperatively. Continuous infusion of short-acting drugs such as nitroprusside, nitroglycerin, or clevidipine and the use of longer-acting drugs such as hydralazine or labetalol are options for blood pressure control. The mechanism of this postoperative hypertension may be related to altered activity of the carotid sinus or loss of carotid sinus function resulting from denervation during surgery. Hypotension is also commonly observed during the period immediately after surgery. The carotid sinus, previously shielded by atheromatous plaque, is now able to perceive blood pressure oscillations more clearly and goes through a period of hyperresponsiveness to these stimuli. Hypotension resulting from carotid sinus hypersensitivity is usually treated with vasopressors such as phenylephrine. Nerve dysfunction is possible after carotid endarterectomy, but most injuries are transient. Patients should be examined for evidence of hypoglossal, recurrent laryngeal, or superior laryngeal nerve injury. Such injury may produce difficulty swallowing or protecting the airway and could result in aspiration. Carotid body denervation can also occur after carotid artery surgery and impair the cardiac and ventilatory responses to hypoxemia. This can be clinically significant after bilateral carotid endarterectomy or with administration of narcotics. Endovascular Treatment of Carotid Disease the technique of carotid artery stenting continues to evolve as an alternative to carotid endarterectomy. The major complication of carotid stenting is stroke as a result of microembolization of atherosclerotic material into the cerebral circulation during the procedure. Embolic protection devices for use during carotid stenting have been developed, but the technology has so far failed to reduce endovascular stroke risk to that seen with the surgical approach. Nevertheless, endovascular approaches carry a lower risk of myocardial infarction, and if embolic protection devices are improved, stenting may one day reemerge as a more widespread alternative to surgery.
Some anesthesiologists administer only one half to two thirds of the morning dose preceding surgery to address similar concerns allergy treatment for adults discount aristocort 4mg with amex. Some surgeons request its discontinuation 48 hours preoperatively so that they can use hypertensive episodes intraoperatively as cues in localizing areas of metastasis allergy forecast dallas today purchase 4 mg aristocort with visa. Prazosin and doxazosin food allergy treatment 2013 order aristocort 4mg on line, pure 1-competitive blockers, are alternatives to phenoxybenzamine. They are shorter acting, cause less tachycardia, and are easier to titrate to a desired end point than phenoxybenzamine. A nonselective -blocker should never be administered before -blockade, because blockade of vasodilatory 2-receptors results in unopposed -agonism, leading to vasoconstriction and hypertensive crises. Propranolol, a nonselective -blocker with a half-life longer than 4 hours, is most frequently used. A patient with a pheochromocytoma secreting solely epinephrine and with coronary artery disease may benefit greatly from the 1selective antagonist esmolol. Esmolol has a fast onset and short elimination half-life and can be administered intravenously in the period immediately before surgery. In combination with phenoxybenzamine, it has been shown to facilitate intraoperative hemodynamic management. Side effects, including extrapyramidal reactions and crystalluria, have limited its application. Calcium is a trigger for catecholamine release from the tumor, and excess calcium entry into myocardial cells contributes to a catecholaminemediated cardiomyopathy. Nifedipine, diltiazem, and verapamil have all been used to control preoperative hypertension, as has captopril. An 1-blocker plus a calcium channel blocker is an effective combination in treatment-resistant cases. Intraoperative goals include avoidance of drugs or maneuvers that may provoke catecholamine release or potentiate catecholamine actions, and maintenance of cardiovascular stability, preferably with shortacting drugs. Hypertension frequently occurs during pneumoperitoneum as well as during tumor manipulation. Intraoperative monitoring should include standard plus invasive monitoring methods. An arterial catheter enables monitoring of blood pressure on a beat-to-beat basis. A central venous pressure catheter is usually sufficient for patients without cardiac symptoms or other clinical evidence of cardiac involvement. A pulmonary artery catheter or transesophageal echocardiography may be necessary to manage the large fluid requirements, major volume shifts, and possible underlying myocardial dysfunction in patients with very active tumors. A large positive fluid balance is usually required to manage hypotension and keep intravascular volumes within a normal range. Intraoperative ultrasonography can be used to localize small, functional tumors and to perform adrenal-sparing procedures or partial adrenalectomies. Adrenal-sparing procedures are particularly valuable when bilateral adrenal pheochromocytomas must be removed. Laparoscopy can be used for tumors smaller than 4 to 5 cm and is becoming the surgical approach of choice for many endocrine surgeons. Although all anesthetic drugs have been used with some degree of success, certain drugs should theoretically be avoided to prevent possible adverse hemodynamic responses.
