Continuous multi-channel intravascular monitoring of the effects of dopamine and dobutamine on plasma potassium in dogs

The effects of dopamine and dobutamine on plasma potassium were investigated in dogs using continuous, multi-channel, intravascular ion-selective potassium electrodes situated in the aorta and abdominal and thoracic inferior vena cavae. Doses of 10 and 30 g kg^-1 min^-1 of each drug were used, and the effects on potassium compared with isoprenaline 0.07 and 0.2 g kg^-1 min^-1. Both the drugs caused a biphasic pattern of potassium change consisting of an initial small rise in the potassium level, followed by a sustained period of hypokalaemia. The changes were greater with the higher dose of each drug compared with the lower dose, but there were no significant differences between the drugs. Comparison of the potassium changes between the three vascular sites studied suggested that the rise in potassium may be a result of release of the ion from the liver, and that the liver may also be the principle site of potassium uptake during the hypokalaemic phase.     

Dobutamine reverses the vasopressin-associated impairment in cardiac index and systemic oxygen supply in ovine endotoxemia

Introduction

Arginine vasopressin (AVP) is increasingly used to treat sepsis-related vasodilation and to decrease catecholamine requirements. However, AVP infusion may be associated with a marked decrease in systemic blood flow and oxygen transport. The purpose of the present study was to evaluate whether dobutamine may be titrated to reverse the AVP-related decrease in cardiac index (CI) and systemic oxygen delivery index (DO₂I) in an established model of ovine endotoxemia.

Methods

Twenty-four adult ewes were chronically instrumented to determine cardiopulmonary hemodynamics and global oxygen transport. All ewes received a continuous endotoxin infusion that contributed to a hypotensive-hyperdynamic circulation and death of five sheep. After 16 hours of endotoxemia, the surviving ewes (n = 19; weight 35.6 ± 1.5 kg (mean ± SEM)) were randomized to receive either AVP (0.04 Umin^-1) and dobutamine (n = 8) or the vehicle (normal saline; n = 6) and compared with a third group treated with AVP infusion alone (n = 5). Dobutamine infusion was started at an initial rate of 2 μg kg^-1min^-1 and was increased to 5 and 10 μg kg^-1 min^-1 after 30 and 60 minutes, respectively.

Results

AVP infusion increased mean arterial pressure (MAP) and systemic vascular resistance index at the expense of a markedly decreased CI (4.1 ± 0.5 versus 8.2 ± 0.3 l min^-1 m^-2), DO₂I (577 ± 68 versus 1,150 ± 50 ml min^-1 m^-2) and mixed-venous oxygen saturation (S_vO₂; 54.5 ± 1.8% versus 69.4 ± 1.0%; all p < 0.001 versus control). Dobutamine dose-dependently reversed the decrease in CI (8.8 ± 0.7 l min^-1 m^-2 versus 4.4 ± 0.5 l min^-1 m^-2), DO₂I (1323 ± 102 versus 633 ± 61 ml min^-1 m^-2) and S_vO₂ (72.2 ± 1.7% versus 56.5 ± 2.0%, all p < 0.001 at dobutamine 10 μg kg^-1 min^-1 versus AVP group) and further increased MAP.

Conclusion

This study provides evidence that dobutamine is a useful agent for reversing the AVP-associated impairment in systemic blood flow and global oxygen transport.     

Influence of nimodipine and nifedipine on intrapulmonary shunting — a comparison to other vasoactive drugs

This study was assigned to investigate the influence of calcium channel blockers (nimodipine and nifedipine) in comparison to other vasoactive drugs (nitroglycerin, dopamine) on pulmonary shunting (Qs/Qt). Fifty anesthetised patients scheduled for aortocoronary bypass operation were randomly allocated to 5 groups receiving one of the following drugs: (1) nimodipine 1.0 g·kg^-1·min^-1; (2) nifedipine 0.7 g·kg^-1·min^-1; (3) nitroglycerin (TNG) 0.5 g ·kg^-1·min^-1; (4) dopamine; (5) g·kg^-1·min^-1; (6) placebo (0.9% NaCl). Nimodipine as well as nifedipine led to a significant increase in cardiac output (+44%; +39%), pulmonary vascular resistance simultaneously decreased (-25%;-28%). PaO₂ increased significantly (+16%; +13%), too, whereas Qs/Qt remained almost unchanged. In contrast, the increase in cardiac output induced by dopamine (+27%) was accompanied by a significant increase in shunting (+34%). TNG application did not alter Qs/Qt, but pulmonary artery pressure (PAP) decreased markedly (-19%).     

Splanchnic oxygen transport after cardiac surgery: evidence for inadequate tissue perfusion after stabilization of hemodynamics

Objective To evaluate the adequacy of visceral oxygen transport and gastric pH_i after open heart surgery in patients with stable hemodynamics.Design Nonrandomized control trial.Setting A general intensive care unit in a tertiary care center.Patients Sixteen postoperative cardiac surgery patients were studied after stabilization of systemic hemodynamics.Interventions The effect of dobutamine infusion (6 g kg^–1 min^–1) on systemic and regional oxygen transport was studied in ten patients, with six patients serving as controls. Systemic oxygen consumption was measured by indirect calorimetry and splanchnic and femoral blood flow, by continuous infusion of indocyanine green using regional catheters and gastric mucosal pH_i by gastric tonometer.Measurements and results Gastric mucosal acidosis was observed in half of the patients. Dobutamine increased cardiac output (3.2±0.6 vs 4.4±0.7l· min^–1·m^–2;P<0.05), splanchnic blood flow (0.68±0.28 vs 0.91±0.281· min^–1·m^–2;p<0.05) and femoral blood flow (0.25±0.08 vs 0.32±0.11l·min^–1·m^–2;p<0.05). Changes in splanchnic oxygen delivery and consumption were parallel in the two study groups. In response to dobutamine, gastric pH_i did not change (7.30±0.08 vs 7.31±0.06; NS), while in the control group, gastric pH_i tended to decrease (7.32±0.04 vs 7.28±0.06; NS). Systemic oxygen consumption increased in response to dobutamine (141±11 vs 149±11 ml· min^–1·m^–2;P<0.05) but did not change in the control group.Conclusions We conclude that a mismatch between splanchnic oxygen delivery and demand may be present despite stabilization of systemic hemodynamics after cardiac surgery. This is suggested by the parallel changes in splanchnic oxygen delivery and consumption. Dobutamine is likely to improve splanchnic tissue perfusion at this phase.This study was supported in part by the senior researcher's grant no. 1945/3015/92 to Dr. Takala from the Academy of Finland     

Comparison of the effects of dopamine and dobutamine during continuous positive-pressure ventilation

The depressant effects of continuous positive-pressure ventilation (CPPV) on circulatory and renal functions, and their reversal by dopamine (5 μg/kg/min), dobutamine (7.5 μg/kg/min), or a combination of the two drugs (dopamine 2.5 and dobutamine 5 μg/kg/min) were studied in 10 patients with acute respiratory distress syndrome (ARDS) requiring treatment with positive end-expiratory pressure (PEEP). In comparison with a control period of intermittent positive-pressure ventilation (IPPV), CPPV increased arterial oxygen tension (PaO₂) by 11%, but decreased the cardiac index (CI) by 21% and systemic oxygen transport (T_{O 2}) by 14%. The additional administration of catecholamines resulted in an increase both in CI — by 38% (dopamine), 33% (dobutamine), and 47% (combination) — and in T_{O 2} —by 34% (dopamine), 28% (dobutamine) and 46% (combination). The observed changes in PaO₂ were negligible. The changeover from IPPV to CPPV resulted in a marked decrease in urinary output (42%), sodium excretion (52%), and in creatinine clearance (36%). Under dopamine or the combination of dopamine and dobutamine there was a two- to threefold improvement in these parameters as compared with the CPPV figures, while under dobutamine alone, the increases were virtually of the same order as the increase in CI. It may be concluded that both dopamine and dobutamine are suitable for correcting impaired circulatory and renal functions induced by CPPV. Their beneficial effects on circulatory and respiratory parameters are virtually identical. In the presence of renal failure, the use of dopamine or a combination of the two drugs is recommended.     

Effects of dopexamine,dobutamine or dopamine on prolactin and thyreotropin serum concentrations in high-risk surgical patients

Objectives Catecholamines are often used for optimisation of cardiac index and oxygen delivery in high-risk surgical patients; however, infusions of dopamine and dopexamine are associated with dose-dependent hypophysiotropic and thyreotropic properties. The objective was to compare endocrine effects of equipotent inotropic doses of dopexamine, dobutamine and dopamine on prolactin and thyreotropin release perioperatively.Design A prospective, randomised, blinded clinical trial.Setting Adult surgical intensive care unit in a university hospital.Patients Thirty male patients (ASA III) undergoing elective major abdominal surgery.Interventions Patients were randomised to receive dopexamine (DX, n=10), dobutamine (DO, n=10) or dopamine (DA, n=10) on the first postoperative day for 8 h.Measurements and results All patients received a catecholamine infusion in doses adjusted to increase cardiac index by 35% within the first hour. Blood samples were obtained and prolactin and thyreotropin serum concentrations were determined by radioimmunoassays. Mean doses of dopexamine, dobutamine and dopamine used were 0.73±0.27, 4.06±1.95 and 5.0±1.84 µg kg^–1min^–1, respectively. Cardiac index was increased by 36% (DX group), 38% (DO group) and 38% (DA group). Alterations of oxygen delivery and oxygen consumption were not significantly different between the study groups. Dopexamine and dobutamine had no hypophysiotropic effects. In contrast, dopamine suppressed prolactin and thyreotropin secretion with a maximal effect after 4 h. After dopamine withdrawal, a rebound release of prolactin and thyreotropin was observed.Conclusions In high-risk surgical patients dopexamine or dobutamine produced fewer effects on prolactin and thyreotropin serum concentrations in comparison with DA when used in equivalent dosages.     

Prostacyclin and right ventricular function in patients with pulmonary hypertension associated with ARDS

Eight patients who developed pulmonary artery hypertension during the adult respiratory distress syndrome (ARDS) were treated with an infusion of prostacyclin (PGI₂, 12.5–35.0 ng·kg^–1·min^–1) for 45 min. We examined whether reducing the right ventricular (RV) outflow pressures by PGI₂ infusion would increase the right ventricular ejection fraction (RVEF) measured by thermodilution. PGI₂ reduced the pulmonary artery pressure (PAP) from 35.6 to 29.1 mmHg (p<0.01). The cardiac index (CI) increased from 4.2 to 5.81·min^–1·m^–2 (p<0.01) partly due to an increased stroke volume. The decreased PAP together with the increased CI resulted in a fall of the calculated pulmonary vascular resistance index (PVRI, from 5.1 to 2.5 mmHg·min·m²·1^–1,p<0.01). In the patients with subnormal baseline RVEF the increased stroke volume was associated with an increased RVEF (from 47.6% to 51.8%,p<0.05) suggesting improved RV function. This result was underscored by a significant relationship between the changes in PVRI and RVEF (r=0.789, % RVEF=–2.11·PVRI-1.45). Despite an increased venous admixture from 27.8% to 36.9% (p<0.05) the arterial PO₂ remained constant resulting in an increased oxygen delivery from 657 to 894 ml·min^–1·m^–2 (p<0.01). We conclude that short term infusions of PGI₂ increased CI concomitant to improved RV function parameters when baseline RVEF was depressed. Since improved oxygen availability should be a major goal in the management of patients with ARDS PGI₂ may be useful to lower pulmonary artery pressure in ARDS.Supported by the Deutsche Forschungsgemeinschaft (grant Fa 139/2-2)     

Comparison of the hemodynamic effects of hydroxocobalamin and cobalt edetate at equipotent cyanide antidotal doses in conscious dogs

Objectives The hemodynamic effects of two cyanide antidotes, hydroxocobalamin and cobalt edetate were compared.Design This experimental study was performed in chronically instrumented conscious dogs and at equipotent cyanide antidotal doses (hydroxocobalamin 70 mg·kg^–1; cobalt edetate 10.5 mg·kg^–1).Results Peak plasma cobalt concentrations did not differ in the two groups (412±183 vs 400±160 mol·1^–1). Hydroxocobalamin induced a slight increase in mean arterial pressure (+17±9%,p<0.05) and systemic resistance (+19±15%,p<0.05). In contrast, cobalt edetate induced an increase in heart rate (+78±33%,p<0.05), in cardiac output (+63±39%,p<0.05), and in maximum rise of left ventricular pressure (+33±15%,p<0.05), did not modify mean arterial pressure, and decreased systemic resistance (–36±15%,p<0.05). These hemodynamic effects were associated with an increase in plasma catecholamine concentrations (epinephrine: 2524±3025 vs. 58±37 pg·ml^–1,p<0.05; norepinephrine: 1106±609 vs. 343±146 pg·ml^–1,p<0.05), which in contrast remained unchanged after hydroxocobalamin administration. Cobalt edetate also induced an increase in blood glucose concentrations (9.9±1.9 vs. 6.1±1.2 mmol·l^–1,p<0.05) and a moderate metabolic acidosis, whereas hydroxocobalamin did not. After adrenergic (1,) and cholinergic receptor blockade, cobalt edetate did not modify heart rate and various indices of cardiac function, suggesting that it has no direct cardiac effects.Conclusion Considering its lack of hemodynamically relevant effects, these results indicate that hydroxocobalamin is potentially a safer cyanide antidote than cobalt edetate.Dr. B. Riou was supported by the Fondation pour la Recherche Médicale. This study was presented in part at the 5th International Trauma and Critical Care Society Symposium, Amsterdam, June 11–12, 1992     

Pharmacokinetics and pharmacodynamics of dopamine and norepinephrine in critically ill head-injured patients

Objective To explore the pharmacokinetics and pharmacodynamics of dopamine and norepinephrine.Design Prospective, controlled, trial.Setting Neurosciences critical care unit.Patients Eight patients with a head injury, requiring dopamine or norepinephrine infusions to support cerebral perfusion pressure (CPP).Intervention Patients received in randomised order, either dopamine or norepinephrine to achieve and maintain a CPP of 70 mmHg, and then, following a 30-min period of stable haemodynamics, a CPP of 90 mmHg. Data were then acquired using the second agent. Haemodynamic measurements were made during each period and a blood sample was obtained at the end of each study period for analysis of plasma catecholamine concentrationsMeasurements and results Plasma levels of norepinephrine and dopamine were significantly related to infusion rates but did not have a simple linear relationship to haemodynamic parameters. However, there was a significant quadratic relationship between the infusion rate of dopamine and cardiac index (r ²=0.431), and systemic vascular resistance index (r ²=0.605), with a breakpoint (at which cardiac index reduced and SVRI increased) at a dopamine plasma level of ~ 50 nM/l (corresponding to an infusion rate of ~ 15 g·kg^-1·min^-1).Conclusions Norepinephrine and dopamine have predictable pharmacokinetics; however, those of dopamine do not fit a simple first-order kinetic model. The pharmacodynamic effects of dopamine and norepinephrine show much inter-individual variability and unpredictability. Plasma levels of dopamine appear to relate to variations in adrenergic receptor effects with break points that reflect expectations from infusion-rate related pharmacodynamics.     

The effects of norepinephrine infusion on oxygen consumption in a patient with septic shock

A 65-year-old man developed postsurgical septic shock, unresponsive to plasma volume expansion and administration of dopamine and dobutamine. A continuous norepinephrine infusion was then started and the dose increased to 0.62 g·kg^–1·min^–1 until the mean arterial pressure was 70 mmHg. Prior to and during the norepinephrine infusion, oxygen consumption was continuously measured with a mass spectrometer system. There was a parallel increase in mean arterial pressure and oxygen consumption (+35%). There was also an increase in cardiac index and oxygen delivery. Systemic vascular resistance was only transiently increased. In this case with septic shock, norepinephrine infusion improved hemodynamic variables with an associated increase in oxygen consumption.     

Effects of chronic dobutamine administration on the response to acute exercise in dogs

Summary. The effects of chronic dobutamine administration on haemodynamic and metabolic responses to submaximal and maximal exercise were studied in dogs. Dobutamine was infused at a rate of 40 μg/kg min^-1, 2 h day^-1, 5 days week^-1 for a period of 6 weeks. Acute infusion of dobutamine for 1 h increased heart rate by 73 ± 30 beats min^-1 and cardiac output by 143 ± 141 ml/min kg^-1, reduced mean arterial blood pressure by 12 ± 10 mmHg and arterial-venous O₂ difference by 1.5 ± 1 vol%. Maximal oxygen consumption, heart rate, stroke volume, cardiac output and arterial-venous O₂ difference were unchanged after 6 weeks of treatment. Reductions in heart rate at rest and during submaximal exercise following chronic dobutamine treatment were small and significant only at the lowest exercise level studied. Mixed venous lactate concentrations measured at rest, during submaximal and maximal exercise and at 2 min of recovery were not different after dobutamine treatment. Chronic dobutamine infusion did not change the citrate synthase activity in the lateral gastrocnemius muscle. These results suggest that chronic dobutamine therapy in healthy dogs does not produce aerobic training responses.     

Comparison of systemic and regional effects of dobutamine and dopexamine in norepinephrine-treated septic shock

Objectives: To compare the effects of dobutamine and dopexamine on systemic hemodynamics, lactate metabolism, renal function and the intramucosal-arterial PCO₂ gap in norepinephrine-treated septic shock. Design: A prospective, interventional, randomized clinical trial. Setting: Adult medical/surgical intensive care unit in a university hospital. Patients: After volume resuscitation, 24 patients were treated with norepinephrine alone titrated to obtain a mean arterial pressure of 75 mmHg and a cardiac index greater than 3.5 l/min^-1· m^-2. Interventions: Patients were randomized to receive an infusion of dobutamine (n = 12) (5 μg/kg per min) or dopexamine (n = 12) (1 μg/kg per min). Measurements and main results: Baseline measurements included: hemodynamic parameters, renal parameters (diuresis, creatinine clearance and urinary sodium excretion), gastric mucosal-arterial PCO₂ gap, arterial and mixed venous gases and arterial lactate and pyruvate levels. These measurements were repeated after 1 (H₁), 4 (H₄) and 24 (H₂₄) h. No difference was found between dobutamine and dopexamine among H₀ and H₁, H₄ and H₂₄ values for hemodynamics. Dobutamine and dopexamine at low doses had no significant effect on mean arterial pressure, heart rate, cardiac index, oxygen delivery, oxygen consumption and pulmonary artery occlusion pressure. No patients developed arrhythmia or electrocardiographic signs of myocardial ischemia. After 4 and 24 h lactate concentration decreased in the dobutamine group from 2.4 ± 1 mmol/l to 1.7 ± 0.7 mmol/l and 1.5 ± 0.4 mmol/l, respectively, while it increased in the dopexamine group from 2.3 ± 1 mmol/l to 2.7 ± 1 mmol/l after 4 h and returned to baseline values after 24 h (2.2 ± 0.6). After 24 h the lactate/pyruvate ratio decreased in the dobutamine group from 15 ± 5 to 12 ± 3 (p < 0.05) while it was unchanged in the dopexamine group (from 16 ± 6 to 17 ± 4). Arterial pH increased in the dobutamine group from 7.35 ± 0.05 to 7.38 ± 0.07 (p < 0.05) while it was unchanged in the dopexamine group (from 7.34 ± 0.01 to 7.35 ± 0.10). The PCO₂ gap decreased after 1 and 4 h in both the dobutamine and dopexamine groups (p < 0.05 with respect to baseline). When looking at individual responses, however, patients from both groups exhibited an increased gastric PCO₂ gap. No difference was found between dobutamine and dopexamine for renal parameters. Conclusions: In norepinephrine-treated septic shock, low doses of neither dobutamine nor dopexamine caused significant effects on systemic hemodynamics and renal function and both dobutamine and dopexamine inconsistently improved the PCO₂ gap. The present results support the need for individual measurement of the effects of catecholamine on the PCO₂ gap. Received: 26 October 1998 Final revision received: 11 April 1999 Accepted: 8 June 1999     

Branched-chain Amino Acid Nitrogen Transfer to Alanine In Vivo in Dogs: DIRECT ISOTOPIC DETERMINATION WITH [15N]LEUCINE

To investigate the contribution of branched-chain amino acids as a nitrogen source for alanine in vivo, dogs were infused with l-[¹⁵N]leucine, l-[U-¹⁴C]leucine, l-[2,3,3,3-²H₄]alanine, and d-[6,6-²H₂]-glucose. ¹⁴C and ¹⁵N isotopic equilibrium in plasma leucine, and deuterium enrichment in arterial and femoral plasma glucose and alanine were achieved within 3 h of initiation of the respective isotope infusion in all animals. The average flux of leucine determined by [¹⁵N]leucine was 5.4 μmol·kg⁻¹·min⁻¹, whereas using [¹⁴C]leucine it was 3.7 μmol·kg⁻¹·min⁻¹. Turnover rates for alanine and glucose were 11.0 and 17.2 μmol·kg⁻¹·min⁻¹, respectively.     

Myocardial perfusion and glucose uptake coupling in CAD patients

Purpose: To evaluate coronary artery disease (CAD) patients regarding to their perfusion-glucose uptake relationship at rest for all myocardial regions and to determine whether this evaluation could typify patients with different positron emission tomography (PET)-pattern proportions and pathophysiological characteristics. Methods: Rest/dipyridamole H₂ ¹⁵O and ¹⁸FDG PET studies were performed in 23 patients with left ventricular dysfunction. Regional index (relative perfusion, %H₂ ¹⁵O; relative glucose uptake, %¹⁸FDG) allowed to detect perfusion-metabolism mismatch (i.e. hibernation) and dipyridamole-induced reversible stress defects (RSD). Results: The correlation (r) between %H₂ ¹⁵O and %¹⁸FDG at rest allowed definition of three groups: correlated (CORR; r > 0.7; n = 10), semicorrelated (SEMI; 0.5 < r 0.7; n = 6) and uncorrelated (UNCO; r 0.5; n = 7). In UNCO, 96% of regions had a %H₂ ¹⁵O 55% (p < 0.01 vs. 89 and 82% in SEMI and CORR) and 95% of regions had a %¹⁸FDG 55% (p < 0.01 vs. 78 and 71% in SEMI and CORR). Mismatch proportions increased from CORR to SEMI and UNCO (11, 19 and 27%; p < 0.02) and proportion of regions with RSD was higher in UNCO and SEMI (25 and 24 vs. 6% in CORR; p < 0.01). Proportion of mismatch with RSD was at least three fold higher in UNCO (17/58) (p < 0.01 vs. 3/33 and 1/16 in SEMI and CORR). Conclusions: Analysis of perfusion and glucose uptake at rest allowed to typify three categories of CAD patients with different PET-patterns proportions, distinctive ranges of perfusion and glucose uptake and distinctive hyperemic response. Our results suggest that myocardial hibernation associated with defective hyperemic response is specific of patients with preserved perfusion and glucose uptake.     

Levosimendan for resuscitating the microcirculation in patients with septic shock: a randomized controlled study

Introduction

The purpose of the present study was to investigate microcirculatory blood flow in patients with septic shock treated with levosimendan as compared to an active comparator drug (i.e. dobutamine). The primary end point was a difference of ≥ 20% in the microvascular flow index of small vessels (MFIs) among groups.

Methods

The study was designed as a prospective, randomized, double-blind clinical trial and performed in a multidisciplinary intensive care unit. After achieving normovolemia and a mean arterial pressure of at least 65 mmHg, 40 septic shock patients were randomized to receive either levosimendan 0.2 μg·kg^-1·min^-1 (n = 20) or an active comparator (dobutamine 5 μg·kg^-1·min^-1; control; n = 20) for 24 hours. Sublingual microcirculatory blood flow of small and medium vessels was assessed by sidestream dark-field imaging. Microcirculatory variables and data from right heart catheterization were obtained at baseline and 24 hours after randomization. Baseline and demographic data were compared by means of Mann-Whitney rank sum test or chi-square test, as appropriate. Microvascular and hemodynamic variables were analyzed using the Mann-Whitney rank sum test.

Results

Microcirculatory flow indices of small and medium vessels increased over time and were significantly higher in the levosimendan group as compared to the control group (24 hrs: MFIm 3.0 (3.0; 3.0) vs. 2.9 (2.8; 3.0); P =.02; MFIs 2.9 (2.9; 3.0) vs. 2.7 (2.3; 2.8); P <.001). The relative increase of perfused vessel density vs. baseline was significantly higher in the levosimendan group than in the control group (dMFIm 10 (3; 23)% vs. 0 (-1; 9)%; P =.007; dMFIs 47 (26; 83)% vs. 10 (-3; 27); P <.001). In addition, the heterogeneity index decreased only in the levosimendan group (dHI -93 (-100; -84)% vs. 0 (-78; 57)%; P <.001). There was no statistically significant correlation between systemic and microcirculatory flow variables within each group (each P >.05).

Conclusions

Compared to a standard dose of 5 μg·kg^-1·min^-1 of dobutamine, levosimendan at 0.2 μg·kg^-1·min^-1 improved sublingual microcirculatory blood flow in patients with septic shock, as reflected by changes in microcirculatory flow indices of small and medium vessels.

Trial registration

NCT00800306.     

A comparison of dopamine,dobutamine and isoproterenol in the treatment of shock

Twelve patients in shock, defined as being present if the mean arterial blood pressure was less than 60 mm Hg, pulmonary arterial occlusion pressure was 15 mm Hg or greater, urine output was 20 ml or less for 2 consecutive hours, and there was clinical evidence of poor peripheral perfusion, underwent a comparative therapeutic trial with dopamine at 200 g · min^-1 and 400 g · min^-1 (2.5–5.5 g · kg^-1 · min^-1), dobutamine 250 g · min^-1 and 500 g · min^-1 (3.5–7 g · kg^-1 · min^-1) and isoproterenol 2 g · min^-1 and 4 g · min^-1 (0.025–0.055 g · kg^-1 · min^-1). Isoproterenol at 2 g · min^-1, produced a significant increase in pulse rate, cardiac output, left ventricular stroke work index and decrease in mean pulmonary blood pressure and pulmonary arterial occlusion pressure and at 4 g · min^-1 a significant increase in stroke volume, mixed venous oxygen tension and decrease in right atrial pressure and systemic vascular resistance was also observed. Dopamine at 200 g · min^-1 produced a significant increase in cardiac output, pulmonary arterial occlusion pressure and mixed venous oxygen tension and at 400 g · min^-1 a significant increase in pulse rate, mean arterial blood pressure mean pulmonary blood pressure, right ventricular stroke work index, right atrial pressure and pulmonary arterial occlusion pressure and decrease in arterial oxygen tension was also observed. Dobutamine at 250 g · min^-1 produced a significant increase in cardiac output, and at 500 g · min^-1 a significant increase in pulse rate, mixed venous oxgen tension and decrease in pulmonary arterial occlusion pressure.All agents increased pulse rate and cardiac output, although in the dosages chosen dopamine was the only agent do so with an increase in pulmonary arterial occlusion pressure and decrease in arterial oxygen tension. In patients in shock if an inotropic agent is considered necessary its pulmonary effect should be considered along with its effect on coronary and peripheral perfusion since dopamine may reduce arterial oxygenation.     

Distribution of potassium levels on admission for CPR--severe hypokalaemia with dysmorphophobic eating disorders

Aim

To evaluate the prevalence and cause of severe hypokalaemia in patients administered for cardiopulmonary resuscitation (CPR) for non-traumatic cardiac arrest.

Methods

We conducted a retrospective database review in the setting of a University hospital on 281 consecutive adult patients admitted to emergency admission, cardiac catheterization laboratory or intensive care units for resuscitation from non-traumatic cardiac arrest. The first available potassium value was evaluated.

Results

The mean potassium level was 3.9 ± 0.9 mmol/l and thus within the reference range of 3.5-5.0 mmol/l, but the overall prevalence of hypokalaemia was high (31.0%). Moderate rather than severe hypokalaemia was typically observed, with 95% of patients exhibiting potassium levels above 2.7 mmol/l. Among those six patients with extreme hypokalaemia defined as a potassium levels below the 2.5 percentile, two adult females were identified to suffer from previously untreated body scheme disorder with furosemide abuse (potassium 1.1 and 1.4 mmol/l). Another patient (potassium 2.1 mmol/l) suffered from poorly controlled bulimia nervosa and acute diarrhoea due to GI infection and one (potassium 2.4 mmol/l) from untreated bulimic anorexia.

Conclusions

In contrast to moderately reduced potassium which is a frequent finding in adult patients at the time of admission for non-traumatic cardiac arrest, severe hypokalaemia is uncommon. The high prevalence of patients with body dysmorphophobic eating disorders in this group underscores accidental self-induced hypokalaemia may evolve as an important differential diagnosis in cardiac arrest in young female patients.     

Clonidine as a sedative adjunct in intensive care

A 63-year-old man underwent distal oesophagectomy and proximal gastrectomy. Postoperatively, controlled ventilation was necessary for 53 days because of anastomotic leakage. Multiple sedative regimens proved to be inadequate. By contrast, a fentanyl-midazolam combination with continuous supplementation of clonidine 0.014 g kg^–1 min^–1 (1.44 mg 70 kg^–1 24h^–1) was very effective in terms of sedation and pain relief. During combined fentanyl-midazolam and clonidine infusion, cardiovascular depression gradually developed over several days necessitating the institution of a dobutamine infusion (dose: 8–12 g kg^–1 min^–1). Four attempts of abrupt clonidine withdrawal were followed by sympathetic overshoot reactions consisting of tachycardia, hypertension, agitation, and sweating. Discontinuation of clonidine was finally possible after a 12-day weaning period.     

Effects of two inotropic drugs,dopamine and dobutamine,on pulmonary gas exchange in artificially ventilated patients

The inotropic agents, dopamine (DP) and dobutamine (DB), both decrease PaO₂, probably by a resistribution of the ratio. The aim of this study was to assess the effect of both drugs on the ratio, using the multiple inert gas elimination method. Ten artificially ventilated patients (eight males), aged 45–74 years were investigated. Blood gases, cardiac output and concentrations of inert gases were measured before and 30 min after infusion of DB or DP. DP and DB were administered alternatively at a rate of 5 g·k^-1 min^-1. The decrease in PaO₂ was significantly greater with DP (12±9 torr) than with DB (7±9 torr) (P< 0.01) Both drugs similarly increased cardiac ouput: +2.6l·min^-1±1.4 for DP and 2.2l·min^-1±1.5 for DB. Both DP and DB significantly (P< 0.01) increased the perfusion of alveoli with (+4±7% for DP and +3±7% for DB) and (+11±8.5% for DP and +5.5±10.5% for DB) (no significant difference between the drugs). When shunt and shunt-like effect are considered together, there was a significantly greater increase in the amout of blood going to alveoli with a low ratio with DP compared to DB. Both drugs decreased the perfusion of alveoli with , but the decrease was significantly less for DB than for DP (-15±6.5% for DP and-8.5±7% for DB,p< 0.01). We conclude that dopamine induces a greater degree of hypoxaemia compared to dobutamine due to a larger increase in shunt and/or maldistribution of the ratio.