Synergistic electrocatalytic activity of In2O3@FMWCNTs nanocomposite for electrochemical quantification of dobutamine in clinical patient blood and in injection dosage form.

Dobutamine (DBT) is a sympathomimetic amine drug that was designed as an inotropic agent for use in congestive heart failure. Hence, there was an impetus to develop a rapid and accurate method for monitoring the concentration of DBT within clinical samples. To address this critical need, a novel In2O3 and functionalized multi-walled carbon nanotubes nanocomposite (In2O3@FMWCNTs) was successfully prepared and applied in an electrochemical sensor to detect DBT. The resulting sensor displayed electrocatalytic toward the oxidation of DBT, which attributed to the synergistic effect of In2O3 and FMWCNTs. Electrochemical impedance spectroscopy (EIS) studies revealed that the smaller charge transfer resistance value (Rct) was observed at In2O3@FMWCNTs modified glassy carbon spherical (GCS) paste electrode (PE) as compared to that of In2O3NPs/GCSPE, FMWCNTs/GCSPE and GCSPE, which authenticates its good conductivity. Furthermore, the calculated value of standard rate constant (ks) for the modified electrode demonstrates the fast electron transfer between DBT and the electrode surface. The fabricated electrochemical sensor indicated high selectivity and sensitivity for DBT determination over the oxidation of uric acid and ascorbic acid. The limit of detection of DBT at In2O3@FMWCNTs/GCSPE was found to be 1.42 × 10-10 M. The proposed sensor is effectively used for the detection of DBT in biological fluids, clinical patient blood and in injection dosage form.

Quantitative determination of dobutamine in newborn pig plasma samples by HPLC-MS/MS.

A novel gradient reverse phase high performance liquid chromatography tandem mass spectrometry (HPLC/MS-MS) was performed as a method for the determination of dobutamine hydrochloride (DOB) in newborn pig plasma samples. It was developed and validated after optimization of sample treatment and various chromatographic and mass spectrometric conditions. Trimethoxydobutamine (TMD) was used as internal standard. Heptafluorobutyric acid (HFBA) and ethyl acetate were used for the treatment of plasma samples. The separation of dobutamine and internal standard was done using a Kinetex F5 (50×2.1mm, 2.6µm, 100Å) analytical column. The mobile phase was a mixture of acetonitrile and HCOOH 0.01%. The column oven temperature was optimized at 40° C and the flow rate was 0.25mL/min. DOB and TMD were detected by multiple reaction monitoring (MRM) mode in ESI+, using a cone voltage (CV) of 25V and a collision energy (CE) of 25eV. The weighted calibration curve (1/x2) was found to be linear over the concentration range of 1-100ng/mL (r2>0.999). The limit of quantification (LLOQ) of the method was 1ng/mL. The values of selectivity, carryover, LLOQ, linearity, accuracy, precision, matrix effect, stability and recovery obtained meet the acceptable range according to European Medicines Agency (EMA) and Food and Drug Administration (FDA) guidelines. The method was efficiently applied to quantify DOB in plasma samples from a pharmacokinetic/pharmacodynamic study in a disease model of newborn piglet.

Short-term add-on therapy with angiotensin receptor blocker for end-stage inotrope-dependent heart failure patients: B-type natriuretic peptide reduction in a randomized clinical trial.

OBJECTIVE: We aimed to evaluate angiotensin receptor blocker add-on therapy in patients with low cardiac output during decompensated heart failure. METHODS: We selected patients with decompensated heart failure, low cardiac output, dobutamine dependence, and an ejection fraction <0.45 who were receiving an angiotensin-converting enzyme inhibitor. The patients were randomized to losartan or placebo and underwent invasive hemodynamic and B-type natriuretic peptide measurements at baseline and on the seventh day after intervention. ClinicalTrials.gov: NCT01857999. RESULTS: We studied 10 patients in the losartan group and 11 patients in the placebo group. The patient characteristics were as follows: age 52.7 years, ejection fraction 21.3%, dobutamine infusion 8.5 mcg/kg.min, indexed systemic vascular resistance 1918.0 dynes.sec/cm(5).m(2), cardiac index 2.8 L/min.m(2), and B-type natriuretic peptide 1,403 pg/mL. After 7 days of intervention, there was a 37.4% reduction in the B-type natriuretic peptide levels in the losartan group compared with an 11.9% increase in the placebo group (mean difference, -49.1%; 95% confidence interval: -88.1 to -9.8%, p = 0.018). No significant difference was observed in the hemodynamic measurements. CONCLUSION: Short-term add-on therapy with losartan reduced B-type natriuretic peptide levels in patients hospitalized for decompensated severe heart failure and low cardiac output with inotrope dependence.

Short-term add-on therapy with angiotensin receptor blocker for end-stage inotrope-dependent heart failure patients: B-type natriuretic peptide reduction in a randomized clinical trial

OBJECTIVE: We aimed to evaluate angiotensin receptor blocker add-on therapy in patients with low cardiac output during decompensated heart failure. METHODS: We selected patients with decompensated heart failure, low cardiac output, dobutamine dependence, and an ejection fraction <0.45 who were receiving an angiotensin-converting enzyme inhibitor. The patients were randomized to losartan or placebo and underwent invasive hemodynamic and B-type natriuretic peptide measurements at baseline and on the seventh day after intervention. ClinicalTrials.gov: NCT01857999. RESULTS: We studied 10 patients in the losartan group and 11 patients in the placebo group. The patient characteristics were as follows: age 52.7 years, ejection fraction 21.3%, dobutamine infusion 8.5 mcg/kg.min, indexed systemic vascular resistance 1918.0 dynes.sec/cm5.m2, cardiac index 2.8 L/min.m2, and B-type natriuretic peptide 1,403 pg/mL. After 7 days of intervention, there was a 37.4% reduction in the B-type natriuretic peptide levels in the losartan group compared with an 11.9% increase in the placebo group (mean difference, -49.1%; 95% confidence interval: -88.1 to -9.8%, p = 0.018). No significant difference was observed in the hemodynamic measurements. CONCLUSION: Short-term add-on therapy with losartan reduced B-type natriuretic peptide levels in patients hospitalized for decompensated severe heart failure and low cardiac output with inotrope dependence. .

Which point-of-care creatinine analyser for radiology: direct comparison of the i-Stat and StatStrip creatinine methods with different sample types.

BACKGROUND: Availability of whole blood creatinine estimation for patients scheduled to undergo radiological contrast investigations can provide information to aid patient care by reducing adverse effects and improving departmental efficiencies. METHODS: We performed imprecision studies, different patient sample type comparison in 40 participants, and a limited interference study with dopamine and dobutamine on the i-Stat and StatStrip point-of-care enzymatic analysers with the Beckman DxC800 Jaffe assay. RESULTS: Imprecision results showed that the i-Stat performed better. Patient comparison data indicated that the i-Stat provided better correlation than the StatStrip for all the different sample types with correlation coefficients (r(2)) being 0.995-0.996 and 0.918-0.995, respectively. The i-Stat results had a small positive bias of 6-9% for the three different sample types, which required different reference intervals. The StatStrip method showed greater scatter and overall small negative bias of -6% for the whole blood samples and a 10% positive bias with the plasma samples. Dopamine caused significant positive interference with the i-Stat only while dobutamine caused a small negative bias with the StatStrip method only. CONCLUSIONS: The findings indicated there are differences offered by the two systems. The StatStrip requires a very small finger prick capillary sample, calculates estimation of the glomerular filtration rate and has an adjustment option to improve correlation with the local method. The i-Stat offers better analytical imprecision and patient comparison with the laboratory method with the three sample types but showed significant interference from dopamine. A final consideration was the availability of middleware to capture patient results with the i-Stat. Based on all the study data, the i-Stat was recommended.

Pharmacokinetic-pharmacodynamic relationship of dobutamine and heart rate, stroke volume and cardiac output in healthy volunteers.

BACKGROUND AND OBJECTIVE: Dobutamine causes an increase in cardiac output (CO) by augmenting stroke volume (SV) through enhanced left ventricular contractility and by decreasing systemic vascular resistance. However, in some patients, the dominant mechanism by which dobutamine improves left ventricular performance is an increase in the subject's heart rate (HR). We therefore decided to evaluate the pharmacokinetic-pharmacodynamic relationship of dobutamine plasma concentrations and heart rate, SV and CO in healthy volunteers. METHODS: We enrolled 23 subjects who received dobutamine at a dose of 2.5, 5 and 10 microg/kg/min for three consecutive periods of 60 minutes each. Dobutamine plasma concentrations were determined from 22 blood samples drawn during each study session. Echocardiography was used to measure CO before administration of dobutamine and once during each infusion period. RESULTS: There was a clear linear relationship between dobutamine plasma concentrations and CO (r(2) = 0.628; p < 0.001). In most subjects, HR remained stable at dobutamine plasma concentrations produced by the lowest infusion rate but increased markedly thereafter so that overall there was a linear relationship between dobutamine plasma concentrations and HR (r(2) = 0.540; p < 0.001). However, SV increased significantly at the dobutamine plasma concentrations produced by the lowest infusion rate but remained mostly stable or even decreased thereafter. Although clinically slight, the overall increase in SV was statistically significant (r(2) = 0.062; p < 0.05). CONCLUSION: Low plasma concentrations of dobutamine resulted in an increase in CO almost solely due to improved left ventricular contractility. However, at higher plasma concentrations of dobutamine, SV remained stable or even decreased, and the linear increase in CO was entirely based on increased HR.

Characterization of the acute cardiovascular effects of intravenously administered insulin-like growth factor-I in conscious Sprague-Dawley rats.

1. Insulin-like growth factor (IGF)-I has acute effects on cardiovascular function, including a well-characterized vasodilator response in isolated arteries. In addition to increasing the release of nitric oxide, IGF-I also has effects on a variety of other signalling pathways that affect vascular tone, in particular interactions with the sympathetic nervous system and the renin-angiotensin-aldosterone system. We sought to characterize the effects of intravenous IGF-I on blood pressure and on responses to noradrenaline (NA), angiotensin II, acetylcholine and dobutamine. 2. Administration of IGF-I administration caused small decreases in mean arterial pressure (5.4 +/- 1.5%) and responsiveness to the prazosin-sensitive vasoconstrictor effects of NA (a 2.1 +/- 0.6-fold increase in ED(50); n = 40; P < 0.01) and both effects were maximal at 200 microg/kg IGF-I. In addition, IGF-I significantly increased pulse pressure increases induced by low doses of dobutamine (from an increase in pulse pressure of 9.9 +/- 1.2 to 13.4 +/- 1.9 mmHg; n = 39; P < 0.05). Administration of IGF-I had no significant effect on responses to AngII or ACh. 3. Intravenous administration of IGF-I receptor antisense oligonucleotides (400 microg/kg) abolished the effects of IGF-I on NA-induced vasoconstriction (n = 11; P < 0.05), whereas administration of a mismatch oligonucleotide did not. 4. These data indicate that the maximal effects of exogenously administered IGF-I include modest direct vasodilation and inhibition of constrictor responses to NA and an increase in the effect of dobutamine on pulse pressure. The magnitude of these effects was less than what previous in vitro studies and those performed in anaesthetized animals may have indicated likely. 5. The modest magnitude of the dilator effects of IGF-I observed in conscious rats in vivo in the present study suggests that IGF-I is unlikely to be a major player in regulating vascular tone in normotensive animals.

Sensitive assay for catecholamines in pharmaceutical samples and blood plasma using flow injection chemiluminescence analysis.

A rapid and sensitive chemiluminescence (CL) method using flow injection analysis was described for the determination of three catecholamines: dopamine, adrenaline and dobutamine, based on their greatly enhancing effects on the CL reaction of luminol-potassium periodate in basic solutions. Under the optimized conditions, the calibration graphs relating the increase of CL intensity to the concentration of the analytes were linear. The present method allows for the determination of dopamine, adrenaline, and dobutamine over the range of 1.0 x 10(-10) - 1.0 x 10(-7) g/ml. The relative standard deviations for measurements (n=11) of dopamine, adrenaline and dobutamine were 2.9, 2.3 and 1.8% when the concentrations of three catecholamines were at 1.0 x 10(-9) g/ml, respectively. The detection limits of the method were 2.0 x 10(-11) g/ml dopamine, 1.0 x 10(-11) g/ml adrenaline and 4.0 x 10(-11) g/ml dobutamine. The method was successfully applied to the determination of three catecholamines in pharmaceutical samples and blood plasma.

The effect of differing rates and injection sites on the amount of protamine delivered before detection of hemodynamic alterations in dogs.

OBJECTIVES: To determine the effect of the route and rate of protamine administration on the amount of protamine that could be delivered before a hemodynamic reaction occurred in dogs. STUDY DESIGN: Prospective randomized experimental study. ANIMALS: Twenty adult mixed-breed dogs weighing 25.1+/-2.5 kg. METHODS: Before vascular surgery, the dogs were heparinized to reach an activated clotting time (ACT) of 300 seconds. After completion of the vascular surgery, protamine was administered intravenously until a hemodynamic reaction was recorded. The 4 groups of dogs were given protamine at 5 mg/min (slow) or 10 mg/min (fast) via the cephalic or the jugular veins. Systemic and pulmonary arterial pressures, central venous pressure (CVP), and pulmonary arterial occlusion pressure (PAOP) were recorded before and after protamine administration. The dose of protamine was recorded when a reaction occurred, which was defined as mean arterial pressure (MAP) <60 mm Hg or mean pulmonary arterial pressure (MPAP) >20 mm Hg or more than double the baseline value. RESULTS: Significant decreases in systolic arterial pressure (SAP), MAP, and diastolic arterial pressure (DAP) and significant increases in systolic (SPAP), mean (MPAP), and diastolic (DPAP) pulmonary arterial pressures were recorded after protamine administration. The cephalic slow group had significantly fewer protamine reactions than other groups (chi-square = 8.57, P = .03, df = 3). Significantly more protamine could be delivered from the cephalic vein (52.5+/-14.5 mg) compared with the jugular vein (37.6+/-16 mg) before a reaction occurred (P = .048). CONCLUSION: The rate of administration did not have an effect on the amount of protamine delivered. Adverse reactions were minimized when protamine was administered via the cephalic vein at a slow rate. CLINICAL RELEVANCE: We would recommend delivering protamine after cardiopulmonary bypass or vascular surgery through a peripheral venous route.

Mechanisms of dopamine and dobutamine interference in biochemical tests that use peroxide and peroxidase to generate chromophore.

Dopamine and dobutamine have recently been shown to produce a negative interference in several biochemical tests that use peroxide and peroxidase to generate a chromophore. To define the chemical mechanism of this interference, we examined the effects of dopamine and dobutamine in various peroxidase-based biochemical tests. Dopamine interfered stoichiometrically with peroxidase-based tests that use 4-aminophenazone to form chromophore but interfered little in those that use other compounds to generate chromophore. Dopamine reacts with 4-aminophenazone in the presence of peroxide and peroxidase to form a novel quinone-imine dye, with a smaller absorptivity than the chromophore formed in the absence of dopamine. The smaller absorptivity of this novel chromophore results in negative interference by reducing the total absorbance at the wavelength used to measure analyte. In contrast, dobutamine interfered stoichiometrically with all peroxidase-based tests studied, regardless of whether 4-aminophenazone was used to form the chromophore. Dobutamine was rapidly oxidized by peroxide in the presence of peroxidase, thus depleting the peroxide necessary to generate chromophore. Dopamine and dobutamine demonstrate two distinct general mechanisms of interference in peroxidase-based biochemical tests.

Sulfoconjugation and renal excretion contribute to the interpatient variation of exogenous catecholamine clearance in critically ill children.

OBJECTIVE: To delineate the contributions of sulfoconjugation, renal excretion, and patient age to the wide interpatient variability in exogenous dobutamine and dopamine plasma clearance. DESIGN: Simultaneous plasma free and sulfoconjugated dobutamine and/or dopamine, respective urine free catecholamine, and serum creatinine were determined on stable critically ill children receiving unchanged continuous infusions of dobutamine and/or dopamine for at least 1 hr. Free dobutamine and dopamine clearance rates were calculated. SETTING: Pediatric and neonatal intensive care units in university settings. PATIENTS: Forty-seven stable critically ill neonates and children. INTERVENTIONS: Continuous infusions of dobutamine and/or dopamine: nine patients received dopamine only, 27 patients received dobutamine only, and 11 patients received both simultaneously. MEASUREMENTS AND MAIN RESULTS: Fractions of plasma dobutamine and dopamine sulfoconjugated were 0.73 +/- 0.05 and 0.76 +/- 0.05, respectively. Free plasma dobutamine and dopamine clearances were 102 +/- 15 mL/kg/min and 250 +/- 38 mL/kg/min, respectively. Linear regression analyses demonstrated relationships of the fraction of plasma dobutamine and dopamine sulfoconjugated to the respective free plasma clearances (r2 = .30, p < .01, and r2 = 0.29, p < .01, respectively), and, more impressively, to the natural logarithm of the respective free plasma clearances (r2 = 0.58, p < .001, and r2 = 0.39, p < .01). Patients with serum creatinine concentrations >2 mg/dL had lower free plasma dobutamine and dopamine clearance rates than those patients with serum creatinine of <2 mg/dL (6 +/- 1 vs. 107 +/- 15 mL/kg/min for dobutamine and 40 +/- 38 vs. 270 +/- 39 mL/kg/min for dopamine, respectively, p < .05 for both by Mann-Whitney U test). No relationship was noted between free catecholamine clearance and age. CONCLUSION: Sulfoconjugation and renal excretion are important determinants of the wide interpatient variability in plasma free dobutamine and dopamine clearance rates.

Hemodynamic changes, plasma catecholamine responses, and echocardiographically detected contractile reserve during two different dobutamine-infusion protocols.

We studied hemodynamic changes, catecholamine responses, and the occurrence of improved wall thickening by echocardiography during two different dobutamine-infusion protocols. Forty-three patients were studied by using a stepwise incremental dobutamine dose-infusion protocol (10-40 microg/kg/min, 3-min intervals); a subgroup of 11 patients also underwent a continuous dobutamine-infusion protocol (10 microg/kg/min for 12 min) in random order. No patient used beta-blockers. At 3-min intervals, blood pressure, heart rate, and plasma concentrations of dobutamine, epinephrine, and norepinephrine were measured. The echocardiographic improvement of wall thickening was analyzed only in paired protocols by visual assessment in left ventricular regions with normal wall motion at rest. The mean heart rate increased in the continuous and stepwise protocols from 73 to 99 and 74 to 132 beats/min. There was no significant change in blood pressure response between the two protocols. The mean plasma dobutamine concentrations during the continuous and stepwise protocols at 0, 3, 6, 9, and 12 min were 0/0; 31/38; 80/203; 106/448; and 120/692 ng/ml, respectively. In each patient, a response curve was constructed for the plasma dobutamine concentration versus heart rate. The heart rate increment and dobutamine concentration at which wall thickening was detected were similar with both protocols (14 +/- 5 vs. 12 +/- 7 beats/min) and (80 +/- 40 vs. 92 +/- 48 ng/ml; mean +/- SD). Wall thickening was noted in two of 11 patients between 0 and 3 min and 11 of 11 patients between 3 and 6 min in both protocols. Catecholamine responses during the continuous and stepwise protocols were epinephrine, 23 versus 28/28 versus 36, and norepinephrine 301 versus 323/347 versus 519. Only norepinephrine plasma concentrations increased significantly during the stepwise protocol. A 6-min dobutamine infusion was sufficient during both protocols to reach an adequate plasma dobutamine concentration, which induced a detectable increase of wall thickening in all patients. There is a significant differences between the two protocols with regard to the plasma catecholamine changes, so some of the hemodynamic effects during the stepwise dobutamine-infusion protocol may be mediated through release of endogenous catecholamines.

Pulmonary extraction of dobutamine in critically ill surgical patients.

This study was conducted to assess the pulmonary extraction of dobutamine. Eleven patients admitted to the general surgical intensive care unit, with varying diagnoses requiring dobutamine as part of their therapeutic intervention, were included. A single simultaneous sample was drawn, at the clinically required rate of infusion, from the radial and pulmonary artery catheter sites. Total dobutamine clearance was determined using the pulmonary artery (pre-lung) sample. The mean +/- SD total dobutamine clearance was 82 +/- 67 mL.kg-1.min-1 a value which is larger than the average cardiac output of plasma of 56 +/- 20 mL.kg-1.min-1. The mean percent pulmonary extraction fraction of dobutamine was 3.6% +/- 22.5% (range -34-52), a value within the 9% coefficient of variability (CV) of the assay. However, five patients had pulmonary extraction greater than the CV of the assay. Of these five patients, three had "negative" extraction values, and two had "positive" extraction values. There was no relationship between the percent pulmonary extraction of dobutamine and the rate or duration of dobutamine infusion before sampling. The results show that the extraction of dobutamine by the lungs is minimal.

Variability in dobutamine pharmacokinetics in unstable critically ill surgical patients.

OBJECTIVE: To delineate the variability in the pharmacokinetics of dobutamine over time in an unstable critically ill adult surgical patient population concurrently receiving therapeutic interventions to optimize oxygen delivery and consumption variables. DESIGN: Prospective study. SETTING: University hospital adult surgical intensive care unit. PATIENTS: Sixteen hemodynamically unstable adults (aged 18 to 84 yrs) requiring dobutamine for inotropic support. INTERVENTIONS: None. MEASUREMENTS AND MAIN RESULTS: Samples for dobutamine serum concentration determination were collected at selected times during therapy, following at least 30 mins of a constant infusion rate and measured using high-performance liquid chromatography. Clearance and changes in clearance were calculated. A first-order pharmacokinetic model was validated by lack of dependence of dose on clearance and an established graphical method. Mean +/- SD infusion rate of dobutamine was 8.2 +/- 5.7 micrograms/kg/min (range 1.7 to 22.3), which resulted in a mean serum concentration of 214 +/- 183 ng/mL (range 15 to 759). The correlation between infusion rate and steady-state dobutamine concentration was r2 = .67. Variability in steady-state dobutamine concentration at various infusion rates was large. Clearance at initial pharmacokinetic analysis averaged 58.4 +/- 33.3 mL/kg/min (range 19 to 120). The percent change in calculated clearance varies from a 72% decrease to an 88% increase, with the greatest variability in clearance occurring during the first 24 hrs of therapy. There was little correlation between initial dobutamine clearance and weight (r2 = .10), net cumulative fluid balance before initiation of dobutamine (r2 < .01), age (r2 = .20), and estimated creatinine clearance (r2 = .09). CONCLUSIONS: Dobutamine pharmacokinetics in adult critically ill patients is best described by a first-order model. Pathophysiologic factors may have an effect on the pharmacokinetics of dobutamine which appears to change over time. Both inter- and intrapatient variability in infusion rate administered and resultant serum concentrations were wide, suggesting that infusion rate should be guided by clinical end points rather than by predetermined values.

Effect of intracoronary infusions of amrinone and dobutamine on segment shortening, blood flow, and oxygen consumption in in situ canine hearts.

Previous in vivo studies assessing the effects of amrinone on myocardial contractility used intravenous infusions, and thus were complicated by varying cardiac loading conditions. Accordingly, the present study was performed in 15 open-chest, anesthetized (fentanyl and midazolam) dogs using infusions of amrinone and dobutamine directly into the left anterior descending artery (LAD). In the LAD bed, percentage of segment shortening (%SS), an index of local myocardial contractility, was assessed with ultrasonic crystals. Coronary blood flow was measured electromagnetically and used to calculate myocardial oxygen consumption and infused drug concentrations. Amrinone and dobutamine were infused separately into the LAD at rates yielding calculated arterial blood concentrations in the clinical range (100, 150, and 200 micrograms/min, and 2.5, 5.0, and 7.5 micrograms/min, respectively). A mixture of amrinone and dobutamine was also infused into LAD and changes in %SS compared with the sum of the their individual effects. In six of the dogs, an extracorporeal system was used to maintain constant coronary blood flow during amrinone infusions. Amrinone and dobutamine caused individually increases in %SS that were comparable (range, 20%-45%). Myocardial oxygen consumption increased in parallel with %SS for both amrinone and dobutamine. For amrinone, coronary blood flow increased more than myocardial oxygen consumption, resulting in a modest (at highest dose approximately 10%) decrease in oxygen extraction; whereas for dobutamine, coronary blood flow increased in proportion to myocardial oxygen consumption, resulting in no change in oxygen extraction.(ABSTRACT TRUNCATED AT 250 WORDS)

Solid phase extraction and high performance liquid chromatographic determination of dobutamine in plasma of dialysed patients.

An isocratic reversed-phase high performance liquid chromatographic method has been developed for th e determination of dobutamine in the plasma of dialysed patients. A solid phase extraction method with a Sep-Pak C18 cartridge was used to isolate the drug and isoxsuprine (internal standard) from plasma. The separation was carried out on an ODS-Hypersil column with 0.1 M phosphate buffer:acetonitrile:methanol (72:20:8 v/v/v) as the mobile phase. The recovery of dobutamine added to plasma by the extraction procedure was 87 +/- 2.3% (mean +/- SD). The accuracy and reproducibility of the method were within acceptable limits over the concentration range 0-1000 ng/mL. Quantification was by fluorescence detection at 275 nm excitation and 310 nm emission wavelengths with a detection limit of 5 ng/mL for dobutamine. This procedure was applied to ascertain the pharmacokinetics of dobutamine infusion in nine patients with cardiogenic shock and end-stage renal disease undergoing haemodialysis.

Rapid and sensitive assay of dobutamine in plasma by high-performance liquid chromatography and electrochemical detection.

A sensitive and specific high-performance liquid chromatographic method with electrochemical detection was developed for measuring dobutamine in human plasma samples. Following an external standard method, 0.1 ml of EDTA-glutathione plasma was diluted on ice with 0.2 ml of a 5% trichloracetic acid solution. The mixture was centrifuged, filtered, and 30 microliters were injected. Assessment was done by electrochemical detection. The assay was linear from 1 to 400 ng/ml plasma. For determination of dobutamine we also used a liquid-liquid extraction method routinely applied for plasma catecholamines. Liquid-liquid extraction requires application of 100-1000 microliters of plasma. The standard curve was linear from 0.1 to 600 ng/ml. Absolute recovery of dobutamine was 90 +/- 3% with the liquid-liquid extraction procedure and 91 +/- 3% with the protein precipitation method. For both methods dobutamine was separated on Nova-Pak C18 columns. The mobile phase used was 0.1 molar phosphate buffer-acetonitrile (80:20, v/v) with 1-octanesulfonic acid and triethylamine as ion-pair reagents. The pH was adjusted to 2.7.

Dobutamine pharmacokinetics and pharmacodynamics in normal children and adolescents.

Pharmacokinetic and pharmacodynamic data on adrenergic agents in children have revealed wide ranges of plasma clearance rates and hemodynamic responses in patients with critical illnesses or myocardial dysfunction. In order to more clearly elucidate the underlying pharmacologic processes, graded i.v. dobutamine infusions of 0.5, 2.5 and 5.0 micrograms/kg/min were sequentially administered to healthy children and adolescents. Plasma dobutamine concentrations and hemodynamic responses, including echocardiographic measures of systolic and diastolic function, were determined at each infusion rate. Pharmacodynamic data were evaluated by both threshold modeling and mean hemodynamic responses to each infusion rate. Mean plasma dobutamine clearance was 115 +/- 63 ml/kg/min, with an intersubject variability greater than 5-fold. These data establish that the previously published wide variability in dobutamine clearance is not due simply to underlying disease states. Dobutamine clearance was linear over the dosage range evaluated. Dobutamine improved systolic function even at plasma concentrations attained with infusion rates as low as 1 to 2 micrograms/kg/min. The improved systolic function was at least partially due to inotropic effects. In addition, dobutamine improved diastolic function and reduced afterload. Chronotropic effects were observed in only two subjects and only at higher plasma concentrations than the other hemodynamic effects. Individualized threshold modeling effectively described the log-linear relationship between plasma dobutamine concentration and hemodynamic response beyond the threshold concentration.

Dobutamine infusions in stable, critically ill children: pharmacokinetics and hemodynamic actions.

OBJECTIVE: To delineate dobutamine pharmacokinetics and hemodynamic responses in children. DESIGN: Prospective, pharmacokinetic study using sequential, graded dosing of drug. INTERVENTIONS: Graded intravenous dobutamine infusions of 0.5, 2.5, 5, 10, and 20 micrograms/kg/min were sequentially administered for 25 mins each. Plasma dobutamine concentrations and echocardiographically determined hemodynamic data were obtained at baseline and at 15 and 25 mins during each infusion rate. Hemodynamic responses were evaluated by paired t-test and by computerized evaluation of individual dose-response curves. SETTING: Pediatric intensive care unit in a university setting. PATIENTS: Eleven stable, critically ill children previously requiring inotropic support with dobutamine. Seven patients were postcardiac surgical patients; four patients had acute cardiac dysfunction with septic shock and/or adult respiratory distress syndrome. MEASUREMENTS AND MAIN RESULTS: Mean cardiac index increased from 3.8 to 5.2 L/min/m2 (p < .05). Increasing the infusion rate from 10 to 20 micrograms/kg/min increased cardiac index by 16% (p < .05). Cardiac index increased by > 10% in four of seven patients at a dobutamine infusion rate of 0.5 microgram/kg/min (mean 21%). The relationship of plasma dobutamine concentration to cardiac index, systolic blood pressure, and heart rate fit a threshold model with a log-linear relationship after the threshold in seven of nine, seven of 11, and eight of 11 patients, respectively. As anticipated, in the patients who responded, there were linear increases in hemodynamic responses with exponential increases in plasma dobutamine concentrations. Mean plasma clearance rate was 82 +/- 3 mL/min/kg. First-order kinetics were demonstrated by the direct linear relationship of plasma dobutamine concentration to infusion rate (mean r2 = .95; p < .01 for each patient) and by independence of clearance from dose and duration of each infusion. CONCLUSIONS: Dobutamine effectively improves systolic function in critically ill children. Hemodynamic responses to dobutamine generally follow a predicted log-linear dose-response model. Dobutamine clearance in this study was consistent with first-order kinetics. The wide variability in hemodynamic responses and clearance kinetics indicate that dobutamine infusions must be titrated individually.

Simultaneous determination of catecholamines and dobutamine in human plasma and urine by high-performance liquid chromatography with fluorimetric detection.

We report a reliable fluorimetric assay for the simultaneous determination of norepinephrine, epinephrine, dopamine and dobutamine in human plasma and urine, based on liquid-liquid extraction and derivatization with the fluorogenic agent 1,2-diphenylethylenediamine prior to chromatography. The method is sensitive (detection limit 0.3-0.8 pg injected) and reproducible (coefficients of variation 1-10%), and shows good accuracy (93-98%). The method should also be used when one only wants to measure the concentrations of the natural catecholamines, in order to avoid interference by metabolites of dobutamine and by the late-eluting dobutamine itself.