Intravenous contrast

In contrast, intravenous fibrinolytic therapy is harmful without acute ST-segment elevation, a true posterior MI or a presumed new left bundle-branch block. 

Three basic approaches are used to control viral diseases vaccination, antiviral chemotherapy, and stimulation of host resistance mechanisms. Vaccination has been used successfully to prevent measles, rubella, mumps, poliomyelitis, yellow fever, smallpox, chickenpox, and hepatitis B. Unfortunately, the usefulness of vaccines appears to be limited when many stereotypes are involved (e.g., rhinoviruses, HIV). Furthermore, vaccines have little or no use once the infection has been established because they cannot prevent the spread of active infections within the host. Passive immunization with human immune globulin, equine antiserum, or antiserum from vaccinated humans can be used to assist the body s own defense mechanisms. Intramuscular preparations of immune globulin may be used to prevent infection following viral exposure and as replacement therapy in individuals with antibody deficiencies. Peak plasma concentrations of intramuscular immune globulins occur in about 2 days. In contrast, intravenously administered immune globulin provides immediate passive immunity. 

In contrast, intravenous diazepam 150 micrograms/kg did not alter the respiratory depressant effect of intravenous pethidine 1.5 mg/kg in a study in healthy subjects or in patients with chronic obstructive pulmonary disease. Moreover, in the setting of overdose (see (b) above), benzodiazepines might increase the respiratory depressant effects of opioids. 

The distribution of endosulfan and endosulfan sulfate was evaluated in the brains of cats given a single intravenous injection of 3 mg/kg endosulfan (Khanna et al. 1979). Peak concentrations of endosulfan in the brain were found at the earliest time point examined (15 minutes after administration) and then decreased. When tissue levels were expressed per gram of tissue, little differential was observed in distribution among the brain areas studied. However, if endosulfan levels were expressed per gram of tissue lipid, higher initial levels were observed in the cerebral cortex and cerebellum than in the spinal cord and brainstem. Loss of endosulfan was most rapid from those areas low in Upid. Endosulfan sulfate levels peaked in the brain at 1 hour postadministration. In contrast, endosulfan sulfate levels in liver peaked within 15 minutes postadministration. The time course of neurotoxic effects observed in the animals in this study corresponded most closely with endosulfan levels in the central nervous system tissues examined. 

Radiocontrast media (RCM) are highly concentrated solutions of triiodinated benzene derivatives used for performing diagnosis and treatment of vascular disease and enhancement of radiographic contrast [1,2]. However, adverse reactions after RCM administration are common [3]. The frequency and mechanisms of hypersensitivity reactions differ between monomeric and dimeric as well as between ionic and non-ionic types of RCM. Mild immediate reactions have been reported to occur in 3.8-12.7% of patients receiving ionic monomeric RCM and in 0.7-3.1% of patients receiving non-ionic RCM [4-6]. Severe immediate adverse reactions to ionic RCM have been reported in 0.1-0.4% of intravenous procedures, while reactions to nonionic iodinated RCM are less frequent (0.02-0.04%) [4-7]. Fatal hypersensitivity... 

Previous reactors are at high risk for a new reaction. In many cases reported, re-administration of the culprit contrast medium to patients with a previous non-immediate exanthema resulted in a repeat reaction [1]. In some (but not all) cases, a more severe reaction with subsequent RCM exposure has been described. After provocation tests, a re-appearance of the exanthemas after intravenous administration of the culprit contrast medium has been reported in patients with previous contrast medium-induced eruptions [1]. 

Palmer FJ The RACR survey of intravenous contrast media reactions. Final report. Australas Radiol 18 1988 32 426-428. 

Homogenates of MetruUum senile, possibly the world s most common large sea anemone, yield extracts that are powerfully hemolytic for washed mammalian erythrocytes (22). The active substance, metridiolysin, is a protein of molecular weight approximately 80,000. In contrast to the sphingomyelin-inhibitable toxins, metridiolysin is an acidic protein having a pi of about 5. It is thermolabile and is inactivat by proteolytic enzymes. The optimal pH for hemolysis is between 5 and 6, and at pH 8 the lysin is inactive. It can be dissociated into two subunits of unequal size. Besides being cytolytic in vitro, metridiolysin is lethal when injected intravenously into mice. As shown in Table IV erythrocytes from the horse or dog are about a hundred times as sensitive to lysis as those from the mouse, and erythrocytes from other animals tested are intermediate in sensitivity. 

FIGURE 2.6 Dynamic susceptibility contrast imaging. Axial images of the brain are acquired repeatedly, in this case every 1.5 seconds. As a bolus of intravenously injected contrast material enters the brain, first arteries, then brain parenchyma, and finally veins demonstrate a transient loss of signal intensity. In this acute stroke patient, hypoperfusion of the left middle cerebral artery territory results in delayed arrival of the contrast bolus and prolonged stasis of contrast within the tissue. 

CTP is a relatively recent development in acute stroke imaging that is already in routine clinical use in many centers. CTP and MRP are similar in that both techniques are based on rapid serial image acquisition during intravenous injection of a bolus of contrast material. In both techniques, measurements of density over time (for CTP) or signal intensity over time (for MRP) are converted to contrast agent-versus-time curves, and these are processed in similar ways to yield the same perfusion measurements (most often CBV, CBF, and MTT). Example CTP images are shown in Figure 2.12. 

Other electrolytes of importance include calcium (especially if the patient is receiving a calcium channel blocker, such as nicardipine) and magnesium, as hypomagnesemia may predispose the patient to seizures, further complicating the ICP management. If the patient received intravenous iodinated contrast as part of their stroke evaluation, then careful monitoring of the blood urea nitrogen (BUN) and creatinine levels is necessary to detect contrast nephropathy. 

In the total plasma response approach, the bioavailability of a compound is determined by measuring its plasma concentration at different times (up to weeks) after single or long-term ingestion of the compound from supplements or food sources. Generally, a plasma concentration-versus-time plot is generated, from which is determined the area-under-curve (AUC) value used as an indicator of the absorption of the componnd. Here, the term relative bioavailability is more appropriate since AUC valnes of two or more treatments are usually compared. This is in contrast to absolnte bioavailability for which the AUC value of the orally administered componnd is compared to that obtained with intravenous administration taken as a reference (100% absorption). 

Intra-arterial contrast administration may have a higher prevalence than the intravenous route... 

Aminoglycosides, amphotericin B, carboplatin, cisplatin, foscamet, and intravenous contrast dyes... 

Renal angiography (administration of intravenous contrast dye to assess the vasculature of the kidney)... 

There are several pharmacokinetic differences between loop diuretics. Fifty to sixty percent of a dose of furosemide is excreted unchanged by the kidney with the remainder undergoing glucuronide conjugation in the kidney.17 In contrast, liver metabolism accounts for 50% and 80% of the elimination of bumetanide and torsemide, respectively.17 Thus, patients with ARF may have a prolonged half-life of furosemide. The bioavailability of both torsemide and bumetanide is higher than for furosemide. The intravenous (IV) oral ratio for bumetanide and torsemide is 1 1, bioavailability of oral furosemide is approximately 50%, with a reported range of 10% to 100%.18... 

Intravenous pyelogram (IVP) will show retention of radio-contrast in the bladder if the patient has bladder outlet obstruction due to an enlarged prostate only indicated in patients with recurrent hematuria, recurrent urinary tract infection, renal insufficiency, and urolithiasis... 

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