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Biomedical subjects

D De Backer

Publications and source records attributed to D De Backer.

At least 55 records · Page 3Linked to original sources
PubMed1996

High-altitude pulmonary edema with primary pulmonary hypertension.

A 43-year-old woman had two episodes of lung edema at moderate altitudes. She had taken slimming pills containing fenfluramine hydrochloride and diethylpropion hydrochloride. At sea level, catheterization of the right side of the heart showed a mean pulmonary artery pressure of 16 mm Hg, which increased to 34 mm Hg with mild exercise in a supine position. An extensive workup failed to identify a cardiac or a pulmonary cause of pulmonary hypertension. This patient experienced mild primary pulmonary hypertension related to the intake of anorexigens, which was revealed by high-altitude pulmonary edema.

Adult↗
PubMed1996

Oxygenation improvement with nitric oxide in right-to-left shunt without significant effects on pulmonary arterial pressure.

Following surgical closure of an interventricular communication complicating an anterior myocardial infarction, a 74-year-old woman developed severe right ventricular failure and hypoxemia due to the opening of a patent foramen ovale (PFO). Mean pulmonary artery pressure was 24 mm Hg. Treatment with inhaled nitric oxide (5 ppm) increased PaO2 from 47 to 90 mm Hg (FIo(2)1). The present observation points out that nitric oxide inhalation could be useful in the management of severe hypoxemia from a right-to-left shunt due to a PFO even when there is no significant pulmonary hypertension present.

Administration, Inhalation↗
PubMed1995

Methylene blue administration in septic shock: a clinical trial.

OBJECTIVE: A release of nitric oxide has been incriminated in the cardiovascular alterations of septic shock. Since guanylate cyclase is the target enzyme in the endothelium-dependent relaxation mediated by nitric oxide, we studied the acute effects of methylene blue, a potent inhibitor of guanylate cyclase in patients with septic shock. DESIGN: Prospective clinical trial. SETTING: Medical-surgical intensive care unit in a university hospital. PATIENTS: Fourteen patients with severe septic shock requiring adrenergic therapy. INTERVENTIONS: Short-term intravenous infusion of methylene blue. MEASUREMENTS AND MAIN RESULTS: Hemodynamic measurements were obtained at baseline, and 30, 60, and 90 mins after the infusion of 2 mg/kg of methylene blue. Methylene blue administration was followed by a progressive increase in mean arterial pressure (from 61.1 +/- 7.6 to 71.7 +/- 12.0 mm Hg at 60 mins, p < .01). Pulmonary arterial pressure, cardiac filling pressures, cardiac output oxygen delivery, and oxygen consumption were not significantly affected. Left ventricular stroke work increased from 42.5 +/- 17.9 to 48.9 +/- 14.5 g.m after 60 mins (p < .05). Arterial lactate concentration decreased from 3.4 +/- 1.4 to 2.7 +/- 1.3 mmol/L (p < .05). Since these effects were transient, a second dose of methylene blue was administered 90 mins later to six patients and was followed by a similar response. No adverse effect was observed. CONCLUSIONS: In septic shock patients, the administration of methylene blue results in a transient and reproducible increase in arterial pressure, associated with an improvement in cardiac function, but does not increase cellular oxygen availability. The significant reduction in blood lactate concentration is probably related to the reductor effect of methylene blue, rather than to an improvement in tissue oxygenation.

Adult↗
PubMed1995

Models to study the relation between oxygen consumption and oxygen delivery during an acute reduction in blood flow: comparison of balloon filling in the inferior vena cava, tamponade, and hemorrhage.

Different animal models have been used to study the relationship between oxygen consumption (VO2) and oxygen delivery (DO2) and each of them has its own specificity. The present study compared the models of balloon inflation in the inferior vena cava (BALL), tamponade (TAMP), and hemorrhage (HEM) to acutely reduce blood flow in pentobarbital-anesthetized dogs. The order of the procedures was randomized first, but HEM was irreversible so that HEM was applied as the third procedure (n = 10) or as a unique procedure (n = 4). Critical DO2 (DO2 crit) was determined as the intercept of two best fitted lines of regression of VO2 against DO2, but similar results were obtained when it was calculated from blood lactate or from arterio-venous differences in pH (AVpH) or PCO2 (VAPCO2). At DO2 crit, VO2 was 6.6 +/- .7 mL/min.kg in BALL, 6.2 +/- .6 mL/min.kg in TAMP and 6.0 +/- .7 mL/min.kg in HEM (p < .05 vs. BALL). DO2 crit was significantly greater with BALL (14.3 +/- 2.3 mL/min.kg) than with TAMP (10.2 +/- 1.7 mL/min.kg, p < .01 vs. BALL) or HEM (9.1 +/- 1.4 mL/min.kg, p < .01 vs. BALL). Also, critical oxygen extraction (EO2 crit) was significantly lower with BALL (46.5 +/- 4.8%) than with TAMP (62.1 +/- 11.5%, p < .01 vs. BALL) or HEM (66.8 +/- 11.4%, p < .01 vs. BALL, p < .05 vs. TAMP). The earlier onset of tissue hypoxia with BALL was probably related to the blood flow redistribution induced by this model.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1995

Oxygen uptake/oxygen supply dependency: fact or fiction?

More than a decade ago, observations of co-variance between VO2 and DO2 led to the identification of a condition known as pathological O2 supply dependency. This condition was subsequently observed in critically ill patients with sepsis and acute circulatory failure. More recently, other authors have challenged the existence of this condition, often citing methodologic problems or mathematical coupling to account for spurious observations in the earlier studies. Here, we review the evidence for and against pathological O2 supply dependency. We find that many of the arguments have some validity but only in specific circumstances. We conclude, therefore, that pathological O2 supply dependency is a hallmark of acute circulatory failure and that an effective therapeutic approach should be based on an evaluation of organ system function in each individual case. Parameters such as blood lactate, pHi and veno-arterial PCO2 may be useful in this respect.

Animals↗
PubMed1994

Effects of dobutamine and prostacyclin on cerebral blood flow velocity in septic patients.

PURPOSE: Both dobutamine and prostacyclin (PGI2) have been used to increase oxygen delivery in septic patients, but their effects on cerebral blood flow have not been well studied. METHODS: In 10 septic patients with altered mental status, stable hemodynamic status, and normal lactatemia, we investigated the effects of successive infusions of dobutamine at 5 micrograms/kg/min and PGI2 at 5 ng/kg/min on mean blood flow velocity in a middle cerebral artery, using transcranial Doppler flowmetry. RESULTS: Mean flow velocity increased with dobutamine (from 52 +/- 4 to 62 +/- 6 cm/s, P < .005) but not with PGI2 (from 55 +/- 5 to 57 +/- 5 cm/s, P = not significant). Each substance significantly increased cardiac index. Dobutamine increased arterial pressure from 85 +/- 6 to 91 +/- 5 mm Hg (P < .05), but PGI2 decreased it from 87 +/- 6 to 77 +/- 5 mm Hg (P < .005). With each agent, mean flow velocity was correlated with cardiac index (r = .51, P < .001) but not with arterial pressure. PGI2 reduced PaO2 from 103 +/- 10 to 82 +/- 6 mm Hg (P < .005). Cerebral oxygen delivery (estimated by the product of mean flow velocity and arterial oxygen content) increased by 19% with dobutamine but remained unchanged with PGI2. CONCLUSIONS: Dobutamine and PGI2 at the administered doses exert different effects on arterial pressure and middle cerebral artery flow velocity in septic patients. According to these data, dobutamine increases cerebral oxygen delivery more than PGI2.

Adult↗
PubMed1994

Effects of dobutamine on oxygen consumption in septic patients. Direct versus indirect determinations.

Dobutamine has been proposed as a means of disclosing a pathologic oxygen supply (DO2) dependency in critically ill patients. Like other catecholamines, however, dobutamine might increase cellular metabolism, so that oxygen consumption (VO2) would increase regardless of the presence or absence of a supply dependency. This study investigated the effects of graded doses of dobutamine on VO2 in stable, septic patients. Since it has been suggested that the use of reverse Fick equation to determine VO2 can induce a spurious VO2/DO2 dependency owing to a mathematical coupling of data, we determined VO2 both by respiratory gas analysis (VO2DIR) and from the reverse Fick equation (VO2INDIR). In 12 adult patients with signs of sepsis but an otherwise stable hemodynamic status (normal blood lactate levels, and no change in vasoactive drugs or fluid administration for at least 2 h), a dobutamine infusion was administered at a dose of up to 10 micrograms/kg/min in increments of 2 micrograms/kg/min every 10 min. Complete hemodynamic and gas measurements were obtained at baseline, at each dose of dobutamine, and 20 min after discontinuation of the infusion. All of the measured parameters were similar at baseline and after discontinuation of the dobutamine infusion. Dobutamine induced a dose-related increase in the cardiac index (from 3.84 +/- 0.97 to 6.19 +/- 1.56 L/min/m2, p < 0.01) and DO2 (from 501 +/- 123 to 801 +/- 219 ml/min/m2, p < 0.01). Both VO2DIR and VO2INDIR increased, from 161 +/- 37 to 183 +/- 40 ml/min/m2 and from 140 +/- 29 to 168 +/- 42 ml/min/m2, respectively (p < 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1993

Relationship between oxygen uptake and oxygen delivery in septic patients: effects of prostacyclin versus dobutamine.

OBJECTIVE: To compare the effects of prostacyclin (PGI2) and dobutamine on the relationship between oxygen delivery (DO2) and oxygen uptake (VO2) in stable septic patients. DESIGN: Prospective study using a crossover design with alternate order of medications. PATIENTS: Seventeen patients with documented sepsis and a stable hemodynamic status with normal blood lactate concentrations. Eleven patients were mechanically ventilated. Eight patients eventually died. INTERVENTIONS: DO2 and VO2 were calculated before and after a 20-min infusion of 5 ng/kg/min of PGI2 followed or preceded by 5 micrograms/kg/min of dobutamine. MEASUREMENTS AND MAIN RESULTS: Both medications increased cardiac output significantly. At the dose used, PGI2 infusion reduced mean arterial pressure from 90.8 +/- 16.8 to 81.5 +/- 17.3 mm Hg (p < .01) and PaO2 from 97 +/- 25 torr to 82 +/- 22 torr (from 12.9 +/- 3.3 to 10.9 +/- 2.9 kPa) (p < .01) and increased venous admixture from 17.5 +/- 0.6% to 23.8 +/- 8.2% (p < .01). Dobutamine had no significant influence on these variables. PGI2 increased DO2 by 19% (from 470 +/- 105 to 557 +/- 117 mL/min/m2, p < .01) while dobutamine increased DO2 by 27% (from 463 +/- 103 to 589 +/- 156 mL/min/m2, p < .01). PGI2 increased VO2 by 5% (from 148 +/- 38 to 155 +/- 36 mL/min/m2) while dobutamine increased VO2 by 10% (from 146 +/- 36 to 161 +/- 41 mL/min/m2, p < .01). Accordingly, there was an identical decrease in oxygen extraction with PGI2 (from 32.4 +/- 8.2% to 28.6 +/- 7.1%, p < .01) and dobutamine (from 32.4 +/- 8.3% to 28.5 +/- 7.8%, p < .01). The responses to these medications were similar in survivors and nonsurvivors. CONCLUSIONS: PGI2 and dobutamine at the doses used have similar effects on oxygen extraction in critically ill, septic patients, but dobutamine increases DO2 more consistently and is better tolerated than prostacyclin.

Aged↗
PubMed1993

Relation between oxygen consumption and oxygen delivery in patients after cardiac surgery.

The relative contributions of oxygen delivery (DO2) and oxygen extraction (O2ER) to the increase in cellular oxygen uptake (VO2) after cardiopulmonary bypass were studied prospectively in 36 patients after coronary artery bypass grafting (n = 18), valve replacement (n = 17), and removal of a left atrial tumor (n = 1). VO2 was calculated from the Fick equation and DO2 from thermodilution cardiac output and arterial oxygen content. During the first 24 h after cardiac surgery, there was a strong relation between VO2 and DO2 (VO2 = 28 + 0.27 x DO2, r = 0.79, P < 0.0001) but not between VO2 and oxygen extraction. Mixed venous oxygen saturation (SVO2) was usually reduced when cardiac index was below 2.0 L.min-1.m-2. Patients with a prolonged intensive care unit course (> 24 h) had lower cardiac index and lower SVO2 than the other patients. Therefore, the progressive increase in VO2 after cardiac surgery is accomplished primarily by an increase in cardiac output and DO2. It is usually when cardiac function is compromised that O2ER increases and SVO2 decreases.

Aged↗
PubMed1992

[Septic syndrome: cardiocirculatory assessment].

Severe sepsis is characterized by increased oxygen demand, alteration of oxygen extraction, and a diminution of myocardial contractility. The importance of each of these three factors is directly related to the severity of the sepsis. The combination of these factors may lead to tissue hypoxia, which is the shortest route to development of multiple organ failure (MOF). The presence of tissue hypoxia should be suspected in the presence of lactic acidosis. The phenomenon of dependence on oxygen consumption (VO2) in relation to oxygen transport (DO2) is detectable where there is a rise in DO2 induced by perfusion of liquids or administration of vasoactive agents. Study of the relationship between cardiac flow and oxygen extraction is a simple means of studying the relations between VO2 and DO2 at the patient's bedside.

Cardiac Volume↗
PubMed1992

High or low dose steroid therapy for acute renal transplant rejection after prophylactic OKT3 treatment: a prospective randomized study.

In this prospective randomized study, acute renal transplant rejections occurring in patients who received prophylactic OKT3 therapy were treated with either 3 pulses of 8 mg/kg methylprednisolone (MPS) in an alternate-day regimen (total dose 25 mg/kg in 1 week, H group, n = 24) or 5 daily pulses of 3 mg/kg MPS (total dose 17 mg/kg, L group, n = 22). Acute rejection was proven by biopsy in more than 85% of cases in both groups. No difference was observed in rejection reversal (H 88%, L 91%), graft losses in the following 3 months (H 11%, L 4%) or the time evolution of the serum creatinine levels. The number (H 14, L 21) as well as the nature and severity of infections were similar in both groups. Only one death occurred in a patient who received OKT3 rescue therapy for corticoresistant rejections and developed Epstein-Barr virus (EBV)-related lymphoma. In conclusion, low dose MPS pulses appear as effective and safe as a higher dose to reverse acute rejection occurring after OKT3 prophylaxis. Thus, we favour the use of the low dose regimen in these patients.

Acute Disease↗
PubMed1991

Correction of metabolic acidosis in experimental CPR: a comparative study of sodium bicarbonate, carbicarb, and dextrose.

STUDY OBJECTIVE: Carbicarb, sodium bicarbonate, and 5% dextrose were compared for effects on resuscitability in a canine model of electromechanical dissociation after ventricular fibrillation. DESIGN/INTERVENTIONS: 21 healthy mongrel dogs were anesthetized with pentobarbital, intubated, and mechanically supported. They were instrumented to measure heart rate, arterial pressure, pulmonary artery pressure, right atrial pressure, cardiac output, and arterial and mixed venous blood gases. The dogs were then subjected to a protocol that consisted of three successive CPR episodes. During each episode they were treated with repeated injections of one of the three substances, randomly chosen. After two minutes of ventricular fibrillation and four minutes of electromechanical dissociation, CPR was started with a thumper (rate, 60; duty cycle, 50%). If recovery was not obtained after five minutes of CPR, 1 mEq/kg carbicarb or sodium bicarbonate or 5 mL D5W was injected in the right atrium. Half the dose of the same substance was injected every five minutes thereafter; 1 mg epinephrine was also injected every five minutes until recovery. Hemodynamic and gasometric evaluations were performed five and 20 minutes after recovery. This later evaluation served as baseline for the next CPR episode. MEASUREMENTS AND MAIN RESULTS: The duration and success rates of CPR are similar in the three CPR groups. Hemodynamic parameters were also similar during recovery. Bicarbicarb and sodium bicarbonate increased bicarbonate levels and corrected pH in the arterial and mixed venous blood. There was no difference in the blood gas values after carbicarb and sodium bicarbonate. CONCLUSION: In this model of cardiac arrest, carbicarb was not superior to sodium bicarbonate in the correction of metabolic acidosis during CPR.

Acidosis, Lactic↗
PubMed1990

Oxygen uptake/supply dependency. Effects of short-term dobutamine infusion.

The present study explored the possibility of using a short-term dobutamine infusion to disclose oxygen uptake/supply dependency. The effects of a standard dose of 5 micrograms/kg/min of dobutamine on oxygen-derived variables were studied in 73 acutely ill patients with heart failure (n = 24) or sepsis (n = 49). In each group, patients were separated according to their blood lactate concentrations (either above or below 2 mEq/L). In all patient groups, dobutamine resulted in significant increases in cardiac output and oxygen transport. However, oxygen consumption increased significantly only in patients with elevated blood lactate levels (cardiac failure: from 108 +/- 26 to 131 +/- 25 ml/min/M2, n = 8, p less than 0.01; sepsis: from 139 +/- 44 to 167 +/- 68 ml/min/M2, n = 16, p less than 0.01) and not in the other patients (heart failure: from 121 +/- 29 to 115 +/- 31 ml/min/M2, n = 28, NS; sepsis: from 158 +/- 39 to 166 +/- 45 ml/min/M2, n = 21, NS). These data, therefore, indicate that dobutamine at the dose used does not increase oxygen consumption in critically ill patients unless there is coexistent tissue hypoxia reflected by increased blood lactate levels. A short-term dobutamine infusion can be used to disclose an oxygen uptake/supply dependency phenomenon.

Acidosis, Lactic↗
PubMed1989

Hypertonic saline solution-hetastarch for fluid resuscitation in experimental septic shock.

Hypertonic colloid solutions have been found efficacious in the resuscitation from hemorrhagic/traumatic shock. The present study investigated the hemodynamic, gasometric, and metabolic effects of hypertonic colloids in endotoxic shock in the dog. Thirty minutes after administration of 3 mg/kg normal body weight of Escherichia coli endotoxin, dogs were randomly assigned to receive 10 mL/kg hydroxyethylstarch (HES) either in 0.9% NaCl (HES, 10 dogs) or in 7.5% NaCl (HT-HES, 10 dogs) in 30 min. Thereafter, 0.9% NaCl solution was administered in volumes adequate to maintain pulmonary artery balloon-occluded pressure at baseline levels. Total fluid administered averaged 64 +/- 30 mL/kg (mean +/- SD) in the HES group and 73 +/- 34 mL/kg in the HT-HES group. As these differences were not statistically significant, total sodium load was higher in the HT-HES group. The persistent volume effect was associated with persistently lower hematocrit and protein levels in the HT-HES group. Initial fluid resuscitation with HT-HES resulted in arterial pressure, cardiac filling pressures, cardiac output, stroke volume, and rates of oxygen delivery and oxygen consumption that were greater than those with HES. Vascular resistances were similar. Analysis of left ventricular function curves also indicated an improvement in cardiac performance. However, these effects almost completely vanished during the remainder of the study. In the HT-HES group, serum sodium and osmolality levels increased to 167 +/- 4 mEq/L and 344 +/- 4 mOsm/kg H2O, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1989

Initial management of circulatory shock as prevention of MSOF.

Circulatory shock can be defined today as an imbalance between oxygen demand and oxygen supply, resulting in the development of lactic acidosis. The correction of the tissue hypoxia is usually achieved by an increase in oxygen transport following the administration of oxygen, blood, and other fluids and sometimes vasoactive agents. A reduction in the metabolic needs sometimes can contribute to correcting the oxygen deficit. The adequacy of oxygen supply can be assessed by monitoring either blood lactate levels or oxygen consumption immediately before and after an abrupt increase in oxygen transport.

Humans↗
PubMed1987

Calcium chloride in experimental electromechanical dissociation: a placebo-controlled trial in dogs.

While calcium administration has been recommended in CPR, its beneficial effects have been challenged. The effectiveness of calcium chloride was evaluated and compared with epinephrine during successive episodes of electromechanical dissociation (EMD) after ventricular fibrillation in closed-chest dogs. Each of three successive episodes of CPR was randomly and blindly treated by repeated (every 2 min) injections of 5 ml H2O plus either 500 mg of calcium chloride (CaCl2), 1 mg of epinephrine (Epi), or 5% dextrose (D5W). Of 42 CPR attempts performed on 16 dogs, 16 were reversed by only chest compression and artificial ventilation. For the 26 CPR with pharmacologic intervention, recovery was obtained after one injection in 5 of 6 Epi but only in 4 of 11 CaCl2 and 4 of 9 D5W. Only four CPR attempts were ultimately unsuccessful, all in CaCl2 group. During recovery, the Epi group showed significantly higher arterial pressures and heart rates but less severe acidemia. In this model, calcium chloride alone is ineffective during EMD.

Animals↗