Flow rate, intravenous infusion

A 1000-mL bag of intravenous solution contains 2.5 million units of ampicillin. How many units of the drug will have been infused after 6 hours with the flow rate of 1.2 mL/minute ... 

Hypercalcemia can be a medical emergency. Because loop diuretics reduce Ca2+ reabsorption significantly, they can be quite effective in promoting Ca2+ diuresis. However, loop diuretics alone can cause marked volume contraction. If this occurs, loop diuretics are ineffective (and potentially counterproductive) because Ca2+ reabsorption in the proximal tubule would be enhanced. Thus, saline must be administered simultaneously with loop diuretics if an effective Ca2+ diuresis is to be maintained. The usual approach is to infuse normal saline and furosemide (80-120 mg) intravenously. Once the diuresis begins, the rate of saline infusion can be matched with the urine flow rate to avoid volume depletion. Potassium chloride may be added to the saline infusion as needed. 

An intravenous infusion involves a continuous flow of drug into a patient at a rate defined by the infusion rate constant, Rini, with units of mass/time. Discussions of infusion normally present the infusion rate constant as inf, which may be confused with a true reaction rate constant. Therefore, this presentation of infusion uses a less ambiguous variable, Rmi, for the infusion rate constant. 

The assay of an IV formulation is performed using a liquid chromatographic method, which requires the following solutions. For solution (1), dilute a quantity of the intravenous infusion with sufficient mobile phase to produce a solution containing the equivalent of 0.05% w/v of ciprofloxacin. Solution (2) contains 0.058% w/v of ciprofloxacin hydrochloride EPCRS in mobile phase. Solution (3) contains 0.025% w/v of ciprofloxacin impurity C EPCRS (ethylenediamine compound) in solution (2). For solution (4), dilute 1 volume of solution (3) to 100 volumes with the mobile phase. The chromatographic procedure may be carried out using a stainless steel column (12.5 cm x 4 mm) packed with stationary phase C (5 mm) (Nucleosil C18 is suitable). The mobile phase is eluted at a flow rate of 1.5 mL/min, and consists of a mixture of 13 volumes of acetonitrile and 87 volumes of a 0.245% w/v solution of orthophosphoric acid (the pH of which has been adjusted to 3.0 with triethylamine). Analytes are detected on the basis of their UV absorption at 278 nm. The assay is not valid unless in the chromatogram obtained with solution (3), the resolution factor between the peaks due to ciprofloxacin and the ciprofloxacin impurity C is at least 1.5. 

Jain and Jain reported a HPLC method for the microquantification of nimodipine in intravenous infusion fluids [34]. A column (5 cm x 4.6 mm i.d.) of Shim-pack FLC-ODS was eluted with aqueous 75% methanol as the mobile phase (flow rate of 1 mL/min). Detection was effected at 238 nm. The calibration graph was linear over the range of 5-25 pg/mL, and recoveries were from 98.31 to 100.6%. 

The flow of pancreatic juice and bile was tested before and after the experiment by means of an intravenous bolus of 5 pmol/kg secretin. Before the experiment the duodenum was continuously perfused at a rate of 2 ml/min for 435 min with isotonic saline containing phenol red (10 mg/1) as a marker. After drug treatment (intravenous infusion of gastrin-releasing peptide or duodenal HC1 perfusion) pancreatic and hepatic secretions were collected in 15-min periods and the volumes determined by weighing. Duodenal effluents were collected in 15-min periods and phenol red concentrations determined spectrophotometrically. Blood sampled were withdrawn for determination of secretin by radioimmunoassay. 

Two-photon microscopy can be utilized to quantify microvascular flow rates within the kidney. Infusion of a nonfilterable intravenous fluorescent dye results in intravascular cells appearing as dark objects. Endothelial cell dysfunction within the microvasculature can be observed and quantified using the infusion of variously sized, differently colored dextrans or proteins. Movement of these molecules out of the microvasculature and accumulation within the interstitial compartment are readily observed during injury or disease. 

In vitro studies with gentamicin and aminophylline have shown that the delivery of these drugs may be delayed substantially depending on the flow rate and injection site. These observations were confirmed with infusion of chloramphenicol succinate and tobramycin. These studies clearly have demonstrated that the variables of intravenous drug infusion systems (e.g., flow rate. 

The IV flow rate is the number of drops of the IV fluid that the patient receives in a minute. The intravenous order directs the nurse to administer a specific volume of fluid to the patient over a specific time period. It is the nurse s responsibility to calculate the number of drops per minute that is necessary to infuse the IV fluid into the patient over the prescribed time period. 

Qh hepatic plasma flow Ql the infusion rate of a loading intravenous infusion... 

Mechanical flow regulators comprise the largest segment of intravenous infusion systems, providing the simplest means of operation. Patient transport is simple, since these devices require no electric power. Mechanical flow regulators are most useful where the patient is not fluid restricted and the acceptable therapeutic rate range of the drug is relatively wide with minimal risk of serious adverse sequelae. The most common use for these systems is the administration of fluids and electrolytes. 

Aronski et al. (45 ) studied systolic time intervals and peripheral blood flow in 12 patients after induction of anaesthesia with 0.05 ml/kg body weight Althesin and concluded that the drug has a definite cardio-depressive action. In another series of 220 patients (46 ) tachycardia and hypotension were seen in 35 and 25% of cases respectively. The respiratory depressant effect of the drug was related to the speed of injection. Muscle tremors were absent when Althesin was given by intravenous infusion. Even convulsions after Althesin have been described, immediately after the injection (4 C) or, in the case of less rapid injection, after some delay (48C). The slow injection of Althesin can indeed reduce the incidence of aU its side effects, as was shown in a comparison between 2 groups of 30 patients in which differing rates of administration were employed (49C). 

Chen and Gross [48] derived equations to calculate partition coefficients for blood flow-limited compartments from either constant rate infusion (i.e., steady-state conditions) or intravenous bolus regimens. For a noneliminating organ under steady-state conditions,... 

Figure 2.18. Determination of the inuhn clearance. Inuhn is injected intravenously (ideally by way of continuous infusion), and its concentrations in blood and urine are determined. The ratio of these concentrations will be inversely proportional to the urine volume reduction after glomerular filtration multiplied by the urine flow, it thus provides an estimate of the glomerular flltration rate.

Procedure An intravenous infiision of 3% saline is begun at a minimum rate to maintain flow two baseline blood specimens are drawn 15 minutes apart for plasma osmolality and ADH determination. The rate of saline infusion is then adjusted to 0.1 mL/kg/min and maintained with an infusion pump for 2 hours. Blood specimens are collected for plasma osmolality and ADH measurement every 15 minutes during this 2-hour period. 

Nearly all bile acids are choleretic agents that is, they increase bile flow when infused intravenously into various animal species. In all vertebrtae species examined, there is a close relationship between bile flow and the hepatic excretion rate of bile acids (B24). Acute interruption of the enterohepatic circulation of bile acids in man by diversion of bile flow causes the rate of bile secretion to decrease by about 50% (TIO). Thus, the excretion of bile acids from the liver is the major determinant of bile water and solute excretion, predominantly because of the osmotic activity of bile acids in bile. Some interesting studies in dogs have been performed with the bile salt taurodehydrocholate (taurine conjugate of 3,7,12-triketo-5fl-cholan-24-oic acid), which, for stereochemical reasons, cannot form micelles and should therefore have greater osmotic activity than other bile acids. At the same... 

The ability of tubules to reabsorb or secrete a substance is variable. The maximum amount of a substance that the tubules can either reabsorb or secrete in 1 minute is called the Tm for that substance. ( T refers to the tubule and m stands for maximal). This parameter can be calculated by infusing the substance of interest intravenously until the capacity of the tubules to reabsorb or secrete that substance is exceeded. The reabsorptive capacity of the tubules (Tm) can be calculated by knowing the concentration of the substance of interest in both urine and plasma (Ps and U5, respectively), the rate of urine flow per minute (V), and the glomerular filtration rate (GFR). The formula for calculation of reabsorptive Tm for a substance is... 

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