Intracranial relatives

Isoflurane is a respiratory depressant (71). At concentrations which are associated with surgical levels of anesthesia, there is Htde or no depression of myocardial function. In experimental animals, isoflurane is the safest of the oral clinical agents (72). Cardiac output is maintained despite a decrease in stroke volume. This is usually because of an increase in heart rate. The decrease in blood pressure can be used to produce "deHberate hypotension" necessary for some intracranial procedures (73). This agent produces less sensitization of the human heart to epinephrine relative to the other inhaled anesthetics. Isoflurane potentiates the action of neuromuscular blockers and when used alone can produce sufficient muscle relaxation (74). Of all the inhaled agents currently in use, isoflurane is metabolized to the least extent (75). Unlike halothane, isoflurane does not appear to produce Hver injury and unlike methoxyflurane, isoflurane is not associated with renal toxicity. 

The contraindications to the use of thrombolytic drugs are similar to those for the anticoagulant drugs. Absolute contraindications include active bleeding, cardiopulmonary resuscitation (trauma to thorax is possible), intracranial trauma, vascular disease, and cancer. Relative contraindications include uncontrolled hypertension, earlier central nervous system surgery, and any known bleeding risk. 

I11 the therapy of deep venous thrombosis, heparin is commonly administered. This drug takes effect immediately to prevent further thrombus formation. However, heparin is regarded as a hazardous drug and possibly may be tlie leading cause of drug-related deaths 111 hospitalized patients who are relatively well. Usually administered intravenously, preferably by pump-dnven infusion at a constant rate rather than by intermittent injections, it sometimes may cause major bleeding, which is particularly hazardous if it is intracranial. The action of heparin can be terminated almost immediately by intravenous injection of protamine sulfate, but where there may be less urgency, vitamin Ki may be used. The vitamin preparation may be administered intravenously, intramuscularly, or subcutaneously. 

One of the distinguishing characteristics of uncomplicated neurogenic hypertension is its dramatic response to sympathectomy or to chemical blockade of the sympathetic nervous system. Complete sympathectomy results in an immediate reduction in the blood pressure to normal or to subnormal levels with a gradual return to normotensive or slightly higher levels over a period of 1 to 2 months (41, 48, 4)- Moderator nerve section or increased intracranial pressure usually fails to increase the blood pressure in completely sympathectomized animals and if a rise is elicited it is relatively slight and develops slowly (5, 27, 41) ... 

In the diagnosis of intracranial stenosis, TOF-MRA is definitely superior to PC-MRA protocols. Oelerich et al. (1998) found a sensitivity of 87% for 3D TOF-MRA in intracranial stenoses. The correlation with DSA was 78%, and other authors found a correlation with MRA up to 88% (Dagirmanjian et al. 1995). While sensitivity is relatively high, false negative findings are rare, so that with sufficient examination quality, a good negative prediction is reached. 

Embolization of plaque debris or thrombus may block a more distal vessel. Emboli are usually the cause of obstruction of the anterior circulation intracranial vessels (Lhermitte et al. 1970 Ogata et al. 1994), at least in white males in whom intracranial disease is relatively rare. Since emboli follow the prevailing direction of flow in a vessel, most emboli... 

Cerebral edema occurs in response to a wide variety of insults, including ischemia, hypoxia, infection, and noninfectious inflammation. Shifts in brain water, which is the basis of the cellular swelling, are due to osmotic forces, and result in increases in intra- and extracellular spaces. A reasonable amount of tissue swelling can be tolerated in most parts of the body, however, the restrictions imposed by the rigid tentorium and bony skull cause life-threatening herniation with relatively small increases in the brain compartments. Two early anatomists, Monroe (1733-1817) and Kellie (1758-1829), recognized that increased intracranial pressure due to swelling in the cerebrospinal fluid (CSF), blood, or brain tissue compartments could increase intracranial pressure the concept of limited expansion capacity of the intracranial contents is called the Monroe-Kellie doctrine. 

MS), which is a demyelinating disorder. When optic neuritis occurs without disc swelling, the condition is called retrobulbar neuritis. When disc swelling is associated with optic neuritis, the condition is called papillitis. Papilledema is bilateral disc edema associated with increased intracranial pressure OCP). Optic atrophy, the end stage of many optic neuropathies, is characterized by a pale disc and associated with a relative afferent pupillary defect (RAPD) and possible loss of visual acuity, color vision, and visual field. One example of disc atrophy occurs in cases of Leber s hereditary optic neuropathy... 

Less invasive methods of delivering nonviral vectors to the CNS would be more desirable. Despite the minimal inflammatory profile of intracranial delivery of DNA-lipid complexes, the potential exists for surgery-induced adverse events, while the relatively limited volume of cUstribution obtained from stereo tac tic infusion makes the approach rather infeasible when attempting to treat cUseases that involve expansive regions of the brain. To that end, methodologies have been developed to enable the injection of mocUfied... 

In patients with reduced respiratory reserve, such as those with emphysema, severe obesity, cor pulmonale, and kyphoscoliosis, opioids must be used with caution. The relative benefits and harms of using opioids in patients taking monoamine oxidase inhibitors, those with a history of drug abuse, asthma, hepatic impairment, hypotension, raised intracranial pressure, or head injury, and during pregnancy or breast feeding, should be carefully considered. Dextropropoxyphene, pethidine, and methadone should be used with caution (SEDA-21, 85). 

Suxamethonium-induced fasciculation or increased muscle tone can be dangerous in patients with fractures or dislocations (especially vertebral, when the drug is relatively contraindicated), in patients with open-eye injuries or after the eyeball is opened surgically, when an increase in abdominal pressure must be avoided (pheochromocytoma, aortic aneurysm, full stomach, ileus), and in patients in whom a rise in arterial pressure may be catastrophic (cerebral aneurysm, raised intracranial pressure). Prolonged paralysis, occasionally lasting hours, is a risk if the patient is, or has been, taking certain drugs. 

The benzodiazepine antagonist flumazenil is available for the complete reversal of benzodiazepine effects however, because of the mild degree of effects, the relative safety of benzodiazepines and the potential to produce excitability, the reversal of benzodiazepines is rarely indicated. Flumazenil is contraindicated in head trauma because it may elevate intracranial pressure (ICP). 

Contraindications. Contraindications include hypersensitivity to opioids, head trauma or increased intracranial pressure, severe respiratory depression or compromised respiratory function, and potentially, liver or renal insufficiency (46). Whether morphine or other opioids are used depends on the severity of the contraindication, and the potential benefits must be weighed relative to the risk. Anaphylactoid reactions have been reported after morphine or codeine administered i.v., although the reactions are rare (23). Morphine... 

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