Time course of inducible nitric oxide synthase activity following endotoxin administration in dogs

An increased production of nitric oxide (NO) via the inducible isoform of NO synthase (iNOS) has been incriminated in the pathogenesis of septic shock. Since the time course of iNOS activity is not known during endotoxic shock in dogs, we measured iNOS activity, estimated by the rate of conversion of (14)C-arginine to (14)C-citrulline in the absence of calcium, in the heart, lung, liver, kidney, and gut at 1, 2, 3, 4, and 6 h after a bolus of Escherichia coli endotoxin (2 mg/kg, iv), in the dog. This model, including generous fluid administration, is associated with typical features of human septic shock, including low systemic vascular resistance, altered myocardial function and limited oxygen extraction capability. An increase in iNOS activity was observed at 4 h in the liver (0.24 vs 0.04 mU/mg/min) and at 6 h in the heart (0.26 vs 0.09 mU/mg/min). These findings may contribute to a better delineation of the involvement of NO in endotoxic shock, and to the evaluation of the therapeutic effects of NO inhibitors.

European Society of Intensive Care Medicine 14th annual congress, 30 September-3 October 2001, Geneva, Switzerland

The European Society of Intensive Care Medicine Annual Congress offers the opportunity for basic scientists and clinicians to share recent findings. Apart from the large number of free communications, several sessions of the congress were dedicated to state-of-the-art tutorials given by established speakers. The areas of interest of the attendees were widely distributed as usual, a reflection of the large array of so-called 'critical illnesses'. The results of clinical trials and experimental findings using recently developed drugs were presented, essentially in the fields of inflammation, sepsis, and acute lung injury. The benefits of several new compounds observed experimentally need to be confirmed clinically. The European Society of Intensive Care Medicine Congress is well established as a unique opportunity to implement and to promote a collaboration between European basic scientists and clinicians.

Enteral feeding with a solution enriched with antioxidant vitamins A, C, and E enhances the resistance to oxidative stress

OBJECTIVE

To assess whether dietary supplementation with the antioxidant vitamins A, C, and E enhances parameters of oxidative stress and influences the course of critically ill patients.

DESIGN

Prospective, randomized, double-blinded, placebo-controlled study.

SETTING

Department of medicosurgical intensive care of an academic hospital.

PATIENTS

Fifty-one patients expected to require at least 7 days of enteral feeding. Thirty-seven of these patients (age, 57 +/- 7 yrs; Simplified Acute Physiology Score II, 33 +/- 6 points) completed the study.

INTERVENTIONS

Twenty patients were randomized to receive the formula supplemented with vitamins A (67 microg/dL), C (13.3 mg/ dL), and E (4.94 mg/dL), and 17 patients received an isocaloric and isonitrogenous control solution.

MEASUREMENTS AND MAIN RESULTS

Plasma levels of antioxidant vitamins, lipid peroxidation (estimated by the malonyldialdehyde assay), and low-density lipoprotein (LDL), and erythrocyte resistance to experimental oxidative stress were determined on samples drawn two consecutive days before the initiation of feeding and at the end of the 7-day period. Clinical outcome measures included documented infection and intensive care unit and 28-day survival. Administration of the supplemented solution increased significantly the concentration of plasma beta-carotene (from 0.2 +/- 0.0 microg/mL to 0.6 +/- 0.1 microg/mL; p < 0.01) and plasma and LDL-bound alpha-tocopherol (from 6.0 +/- 0.4 microg/mL and 2.9 +/- 0.9 microg/mL to 9.7 +/- 0.5 microg/mL and 4.3 +/- 1.2 microg/mL, respectively; p < 0.05), and improved LDL resistance to oxidative stress by 21 +/- 4% (p < 0.05). No such change was observed in the control group. There was no significant difference in clinical outcome between the two groups.

CONCLUSIONS

Supplemental antioxidant vitamins added to enteral feeding solutions are well absorbed. Dietary supplementation with vitamins A, C, and E is associated with an improvement in antioxidant defenses, as assessed by ex vivo tests.

Hemodynamic responses to successful weaning from mechanical ventilation after cardiovascular surgery

Weaning from mechanical ventilation is usually associated with an increase in oxygen consumption (VO2), which may stress the cardiovascular system. We studied relative changes in the cardiac index and oxygen extraction ratio (EO2) during successful weaning in patients after cardiac surgery (n = 52), cardiac transplantation (n = 17), or abdominal aortic surgery (n = 11). Cardiac index was determined by the thermodilution technique and arterial and mixed venous blood gases were obtained before and 30 min after the start of weaning through a T-piece. The cardiovascular changes were evaluated in 42 patients in whom VO2 (calculated by Fick's equation) increased by more than 10%. Cardiac index increased more after abdominal aortic surgery (from 3.27 +/- 0.77 to 4.44 +/- 0.581 min(-1) m(-2), p < 0.01) than after cardiac surgery (from 2.53 +/- 0.59 to 2.87 +/- 0.46 1 min(-1) m(-2), p < 0.01) or cardiac transplantation (from 2.99 +/- 0.64 to 3.33 +/- 0.741 min(-1) m(-2), p < 0.05). EO2 remained stable in patients after aortic surgery (from 25.9 +/- 7.1 to 25.2 +/- 5.6 %, NS) but increased slightly after cardiac surgery (from 33.3 +/- 6.1 to 37.3 +/- 6.4%, NS) and significantly after cardiac transplantation (from 25.8 +/- 4.1 to 28.2 +/- 4.0%, p < 0.05). Hence the cardiovascular response to weaning from mechanical ventilation may vary according to the type of surgery.

Effects of nitric oxide in septic shock

Nitric oxide (NO) is believed to play a key role in the pathogenesis of septic shock, although many aspects of NO's involvement remain poorly defined. Recent years have seen advances in our understanding of the production and effects of NO, but much of the work has been done in animal models and may not be directly relevant to the clinical situation. Differences between species and models can account for many of the apparently conflicting results obtained. Nevertheless, NO-directed strategies have been developed and tested clinically. However, NO can have both beneficial and detrimental effects on many organ systems in sepsis and attempts to nonselectively block all its actions may therefore not yield positive results on outcome. Further exploration and precision of the role of NO and development of techniques to assess the NO balance in individual patients is necessary before further progress can be made in this field.

Management of the critically ill patient with severe sepsis

Sepsis is a common cause of morbidity and mortality among the critically ill patient population. However, no anti-sepsis therapy has yet been found to be effective and treatment is thus largely supportive. Adequate fluid resuscitation must be accompanied by effective ventilation, and adrenergic agents may be needed to restore perfusion pressure and improve myocardial function. Enteral nutritional support with specialized nutrients has beneficial effects on morbidity, and should be started early. Further research will allow better definition of the septic patient according to immune status and enable more effective targeting of future anti-sepsis treatments.

Enteral nutrition in intensive care patients: a practical approach

Severe protein-calorie malnutrition is a major problem in many intensive care (ICU) patients, due to the increased catabolic state often associated with acute severe illness and the frequent presence of prior chronic wasting conditions. Nutritional support is thus an important part of these patient's management. Over the years, enteral nutrition (EN) has gained considerable popularity, due to its favorable effects on the digestive tract and its lower cost and rate of complications compared to parenteral nutrition. However, clinicians caring for ICU patients are often faced with contradictory data and difficult decision-making when having to determine the optimal timing and modalities of EN administration, estimation of patient requirements and choice of formulas. The purpose of this paper is to provide practical guidelines on these various aspects of enteral nutritional support, based on presently available evidence.

Management of nutrition in European intensive care units: results of a questionnaire. Working Group on Metabolism and Nutrition of the European Society of Intensive Care Medicine

OBJECTIVE

To describe the practical aspects of nutritional management in intensive care units (ICUs).

DESIGN

A 49-item questionnaire was sent to the physician members of the European Society for Intensive Care Medicine. The issues addressed included: medical environment, assessment of nutritional status and current practice for enteral and parenteral nutrition.

SETTING

1608 questionnaires were sent in 35 European countries.

ANALYSIS

The answers were pooled and stratified by country.

RESULTS

271 questionnaires were answered (response rate 17%). Assessment of nutritional status was generally based on clinical (99%) and biochemical (82%) parameters rather than on functional (24%), anthropometric (23%), immunological (18%) or questionnaire-based (11%) data. Two thirds of 2774 patients hospitalised in the corresponding ICUs at the time the questionnaire was answered were receiving nutritional support; 58% of those were fed by the enteral route, 23% by the parenteral route and 19% by combined enteral and parenteral. The preferred modality was enteral nutrition, instituted before the 48th h after admission, at a rate based on estimated caloric requirements. Specific and modified solutions were rarely used. Parenteral nutrition was less commonly used than enteral, although the practices differed between countries. It was mainly administered as hospital-made all-in-one solutions, at a rate based on calculated caloric requirements.

CONCLUSIONS

European intensivists are concerned by the nutritional management of their patients. The use of nutritional support is common, essentially as early enteral feeding.

The metabolic fate of long-term inhaled nitric oxide

PURPOSE

The fate of inhaled nitric oxide (NO) has not been precisely defined in critically ill patients. This study aimed at defining the effects of long-term NO inhalation on circulating NO byproduct levels.

MATERIAL AND METHODS

During NO therapy, plasma and urine from 13 critically ill patients were sampled daily for determination of the stable byproducts of NO (nitrite [NO2-] and nitrate [NO3-]. Routine monitoring data included inhaled NO concentration, hemodynamic parameters, arterial blood gases, creatinine clearance, and C-reactive protein.

RESULTS

For the first 24 hours of NO inhalation (6.3+/-1.1 ppm), NO3- plasma concentration increased (from 13.3+/-5.4 to 52.3+/-17.6 micromol/L), but NO2- plasma concentration was not affected. The NO3- plasma concentration was correlated with the C-reactive protein level, the inhaled NO concentration. Renal excretion of NO metabolites was unaltered by NO inhalation. The NO3 concentrations returned to baseline when NO therapy was discontinued.

CONCLUSION

Long-term NO inhalation was associated with a consistent increase in the NO3- plasma concentration. NO byproducts may be implicated in the systemic effects associated with this treatment.

Enteral nutrition in intensive care patients: a practical approach. Working Group on Nutrition and Metabolism, ESICM. European Society of Intensive Care Medicine

Severe protein-calorie malnutrition is a major problem in many intensive care (ICU) patients, due to the increased catabolic state often associated with acute severe illness and the frequent presence of prior chronic wasting conditions. Nutritional support is thus an important part of the management of these patients. Over the years, enteral nutrition (EN) has gained considerable popularity, due to its favorable effects on the digestive tract and its lower cost and rate of complications compared to parenteral nutrition. However, clinicians caring for ICU patients are often faced with contradictory data and difficult decisions when having to determine the optimal timing and modalities of EN administration, estimation of patient requirements, and choice of formulas. The purpose of this paper is to provide practical guidelines on these various aspects of enteral nutritional support, based on presently available evidence.

Effects of nitric oxide on blood flow distribution and O2 extraction capabilities during endotoxic shock

The effects of the nitric oxide (NO) synthase inhibitor NG-monomethyl-L-arginine (L-NMMA) and the NO donor 3-morpholinosydnonimine (SIN-1) were tested in 18 endotoxic dogs. L-NMMA infusion (10 mg . kg-1 . h-1) increased arterial and pulmonary artery pressures and systemic and pulmonary vascular resistances but decreased cardiac index, left ventricular stroke work index, and blood flow to the hepatic, portal, mesenteric, and renal beds. SIN-1 infusion (2 microg . kg-1 . min-1) increased cardiac index; left ventricular stroke work index; and hepatic, portal, and mesenteric blood flow. It did not significantly influence arterial and pulmonary artery pressures but decreased renal blood flow. The critical O2 delivery was similar in the L-NMMA group and in the control group (13.3 +/- 1.6 vs. 12.8 +/- 3.3 ml . kg-1 . min-1) but lower in the SIN-1 group (9.1 +/- 1.8 ml . kg-1 . min-1, both P < 0.05). The critical O2 extraction ratio was also higher in the SIN-1 group than in the other groups (58.7 +/- 10.6 vs. 42.2 +/- 7.6% in controls, P < 0.05; 43.0 +/- 15.5% in L-NMMA group, P = not significant). We conclude that NO is not implicated in the alterations in O2 extraction capabilities observed early after endotoxin administration.

Intravenous nicardipine in the treatment of postoperative arterial hypertension

BACKGROUND

Calcium entry blockers are commonly used in the management of postoperative hypertension. The hemodynamic and blood gas effects of nicardipine, a dihydropyridine derivative available intravenously, were studied in patients after abdominal aortic surgery.

METHODS

Sixteen patients (66 +/- 8 years) who developed arterial hypertension (mean arterial pressure, > 90 mmHg) after abdominal aortic aneurysm reconstruction were studied. Fourteen patients had already been treated with a sodium nitroprusside infusion, the doses of which were maintained constant (mean dose: 1.42 +/- 1.04 micrograms/kg/min). Hemodynamic and blood gas data were collected at baseline, 15 minutes, and 45 minutes after a slow bolus administration of 3 to 5 mg of nicardipine.

RESULTS

After the nicardipine administration, mean arterial pressure decreased from 101 +/- 11 to 83 +/- 11 mmHg (p < 0.001), and the cardiac index acutely increased from 3.96 +/- 0.74 to 4.57 +/- 0.83 L/min/m2 (p < 0.05). Systemic vascular resistance significantly decreased. There were no significant changes in heart rate, stroke volume, cardiac filling pressures, pulmonary artery pressures, pulmonary vascular resistance, left ventricular stroke work, or right ventricular stroke work. One patient developed acute pulmonary edema, associated with a dramatic increase in cardiac filling pressures, and electrocardiographic signs of myocardial ischemia. Nicardipine administration was also associated with an acute reduction in Pao2 from 85.0 +/- 12.1 mmHg to 70.3 +/- 9.2 mmHg (p < 0.001), associated with an increase in venous admixture from 21.7% +/- 3.2% to 28.0% +/- 5.2% (p < 0.01). Oxygen delivery increased moderately and oxygen extraction decreased, but oxygen consumption was unchanged.

CONCLUSION

This study confirms the excellent efficacy of nicardipine in the management of postoperative hypertension, but underlines the risk of poor cardiac tolerance in patients after major surgery. Although oxygen delivery to the cells is usually well preserved, nicardipine can also significantly after blood oxygenation by increasing ventilation/perfusion mismatch.

Effects of nitric oxide donor SIN-1 on oxygen availability and regional blood flow during endotoxic shock

BACKGROUND

An excessive release of nitric oxide (NO) has been incriminated in the circulatory disturbances of septic shock.

OBJECTIVE

To study the effects of an NO donor, 3-morpholinosydnonimine (SIN-1), an oxygen availability and regional blood flow during endotoxic shock to see if a beneficial effect of NO synthase inhibitors in septic shock could be conclusively demonstrated.

MATERIALS AND METHODS

In 14 anesthetized and mechanically ventilated dogs, global invasive hemodynamic monitoring was completed and ultrasonic flow probes were placed around the superior mesenteric, left renal, and left femoral arteries for simultaneous measurements of regional blood flow. All dogs received Escherichia coli endotoxin, 2 mg/kg. A control group (n = 7) was administered saline at 20 mL/kg per hour, and a SIN-1 group (n = 7) was given a combination of saline with SIN-1 at successive doses of 1, 2, and 4 micrograms/kg per minute.

RESULTS

Neither systemic nor pulmonary arterial pressures were influenced by SIN-1. Cardiac index, stroke index, and left ventricular stroke work index did increase at low to moderate doses of SIN-1 but tended to decrease at the highest dose. Systemic and pulmonary vascular resistances decreased. Fractional blood flow increased in the mesenteric bed at all doses used, was not influenced in the renal bed, but decreased in the femoral bed at the highest dose. Oxygen-derived variables were similar in the 2 groups. Blood lactate and plasma concentrations of tumor necrosis factor were not significantly influenced. At the end of the SIN-1 infusion, the administration of 5 mg/kg of methylene blue increased arterial pressure, pulmonary arterial pressure, and systemic and pulmonary vascular resistances but decreased cardiac index and regional blood flow.

CONCLUSIONS

The administration of low to moderate doses of the NO donor SIN-1 can significantly increase cardiac index and superior mesenteric blood flow without deleterious effects on arterial pressure in this model of endotoxic shock. These findings support the hypothesis that NO is essential to maintain organ blood flow even during endotoxic shock.

Nitric oxide production is increased in patients after burn injury

OBJECTIVE

Human burn injury is associated with an inflammatory response and related hyperdynamic cardiovascular profile. Increased production of nitric oxide (NO), a potent endogenous vasodilator, has been reported in patients with inflammatory states, including sepsis, but not after trauma other than burns. We studied whether plasma levels of the stable byproducts of NO, nitrite (NO2-) and nitrate (NO3-), are increased in burn patients.

DESIGN

Prospective controlled study.

PATIENTS AND METHODS

In consecutive patients admitted to the intensive care unit of the burn center at the Queen Astrid Military Hospital in Brussels, plasma was drawn daily from day 1 to day 5 postadmission for determination of NO2-/NO3- levels (Griess' reaction). In a control group of nonseptic inpatients from the department of neurology in Erasme University Hospital who were matched for nutrition (30 to 40 kcal/kg/day of a standard enteral solution), plasma was drawn once for NO2-/NO3- determination.

MEASUREMENTS AND MAIN RESULTS

The burn group included 16 patients (age 35 +/- 18 years, total burn surface area (TBSA) 37 +/- 19%) and the control group included six patients (age 64 +/- 18 years). For each comparison between the groups, NO2-/NO3- plasma levels were higher in those patients with burns than in the control group. In the burn group, there was no correlation between NO2-/NO3- plasma levels and TBSA, age, TBSA x age, blood pressure or time. However, in a subgroup of five burned patients who became septic during the study period, NO2-/NO3- plasma levels were slightly higher than in the non-infected patients (177 +/- 131 vs. 83 +/- 48 micromoles/L, NS).

CONCLUSION

Human burn injury is associated with an increase in NO production. In this small-size study, NO production was not proportional to burn area, and seemed to be further enhanced in septic patients.

Hypoglycemia associated with phenytoin intoxication

BACKGROUND

Diphenylhydantoin, a widely used antiepileptic agent, can alter carbohydrate tolerance, and acute intoxication with diphenylhydantoin can be associated with hyperglycemia.

CASE REPORT

We describe a patient who experienced a prolonged episode of hypoglycemia secondary to an acute voluntary intoxication with diphenylhydantoin 20 g and zopiclone 225 mg. This hypoglycemic episode was presumptively attributed to diphenylhydantoin and might be due either to an escape from the inhibitory effects of diphenylhydantoin on insulin secretion or an increased sensitivity of the tissues to insulin. Zopiclone was considered less likely since zopiclone overdoses have been only exceptionally associated with hyperglycemia.

Effects of methylene blue on oxygen availability and regional blood flow during endotoxic shock

OBJECTIVE

We hypothesized that methylene blue, by inhibiting the activation of soluble guanylate cyclase mediated by nitric oxide, may reverse systemic hypotension, enhance myocardial function, and improve peripheral distribution of blood flow during endotoxic shock.

DESIGN

Randomized, controlled, acute intervention study.

SETTING

University intensive care laboratory.

SUBJECTS

Twenty-one healthy, anesthetized, mongrel dogs, weighing 26 +/- 4 kg.

INTERVENTIONS

Groups 1 (n = 7) and 2 (n = 7) received endotoxin (2 mg/kg iv) alone combined with increasing doses of 2.5, 5, 10, and 20 mg/kg iv of methylene blue. Each dose was administrated for 30 mins with a free interval of 30 mins. Group 3 (n = 7) served as a control group, receiving the same doses of methylene blue in the absence of endotoxin. All animals were given normal saline to keep cardiac filling pressures constant. Blood flow probes were placed around the superior mesenteric, renal, and femoral arteries to measure regional blood flow by ultrasonic technique. Data were collected every 30 mins during the study.

MEASUREMENTS AND MAIN RESULTS

After endotoxemia, methylene blue increased systemic and pulmonary arterial pressure and vascular resistances in a dose-dependent manner up to 10 mg/kg, but had no effect on cardiac index. At the highest dose, methylene blue decreased arterial pressure and systemic vascular resistance. At doses of methylene blue of < or = 10 mg/kg, mesenteric and femoral blood artery flow increased. At the highest dose of 20 mg/kg, femoral artery blood flow further increased, but mesenteric blood flow decreased. Renal artery blood flow was unaffected by methylene blue. In the absence of endotoxin, methylene blue at doses of 2.5 or 5 mg/kg did not alter mean arterial pressure, but reduced cardiac index, indicating an increase in systemic vascular resistance. In contrast, the higher doses of 10 or 20 mg/kg of methylene blue decreased mean arterial pressure and systemic vascular resistance. However, pulmonary arterial pressure and pulmonary vascular resistance increased in a dose-dependent manner. Mesenteric and renal artery blood flow decreased but femoral blood flow increased. As in the presence of endotoxin, methylene blue induced dose-related increases in oxygen uptake and oxygen extraction ratio, but did not alter oxygen delivery. Methylene blue largely attenuated the endotoxin-induced increase in plasma nitrite concentrations.

CONCLUSIONS

Low and moderate doses of methylene blue can significantly increase arterial blood pressure but not cardiac index during endotoxic shock. Methylene blue infusion may selectively increase mesenteric blood flow. High doses of methylene blue can worsen systemic hypotension, myocardial depression, and pulmonary hypertension after endotoxemia.

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.

Is endotoxin-induced hypotension related to nitric oxide formation?

Nitric oxide (NO), an endothelium-derived relaxing factor (EDRF), is released by different types of cells under the influence of endotoxin and various cytokines: a causative role of endothelium-derived NO in the endotoxin-induced hypotension has thus been suggested. To test the hypothesis that NO may be involved in the acute hypotension following endotoxin challenge, we administered a competitive inhibitor of NO synthase, L-N-monomethylarginine (L-NMMA) to anesthetized dogs in the presence and absence of endotoxin. Dogs were randomly allocated to three groups. Group 1 (n = 3) was given Escherichia coli endotoxin (3 mg/kg, i.v.), group 2 (n = 3) was given L-NMMA (5 mg/kg, i.v. bolus) 15 min after endotoxin and group 3 (n = 3) was given L-NMMA only. One additional dog was given L-arginine (100 mg/kg, i.v. bolus) after L-NMMA and endotoxin to reverse the inhibition of NO synthase. In each animal, saline was infused intravenously throughout the experiment to restore and maintain pulmonary artery occluded pressure at baseline level. After L-NMMA, the increases in mean arterial pressure were similar in group 2 (from 55 +/- 18 to 75 +/- 15 mm Hg, p < 0.01) and in group 3 (from 107 +/- 27 to 128 +/- 24 mm Hg, p < 0.01). Systemic vascular resistance increased from 2,994 +/- 72 to 3,658 +/- 673 dyn.s.cm-5 (p < 0.01) in group 3. Group 1 had lower plasma lactate levels than group 2 (3.5 +/- 2.3 +/- vs. 2.0 +/- 1.6 mEq/l, p < 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

[Should bicarbonates still be administered in lactic acidosis?]

Bicarbonate administration during lactic acidosis seems logical in view of the myocardial depression associated with the decrease in intracellular pH. This treatment has been recently challenged on the basis of observations showing an increase in the veno-arterial gradient for CO2 during acute circulatory failure. The partial transformation of bicarbonate in CO2 carries the risk of aggravating the phenomenon and thereby decreasing intracellular pH. Alternatives to sodium bicarbonate--carbicarb, THAM and dichloroacetate--are discussed.

Inotropic agents

When fluid administration is not sufficient to restore hemodynamic stability, inotropic agents may be given to restore the tissue perfusion pressure and to increase oxygen delivery (DO2) to the cells. Dopamine remains the drug of choice in the resuscitation of septic shock but norepinephrine can also have a place in the treatment of profound cardiovascular collapse or severe right ventricular failure. Dobutamine has become the inotropic agent of choice to increase DO2 to the tissues. Unfortunately, the beneficial effects of these agents on the extraction capabilities of the tissues are questionable. The potential of other adrenergic agents (such as dopexamine) or nonadrenergic agents (such as phosphodiesterase inhibitors) is also discussed in this article. Inotropic therapy should be guided not only by measurements of systemic BP but also by repeated assessments of the metabolic function of organs.

Addition of alinidine, a specific bradycardic agent, to dobutamine in a canine model of endotoxic shock

BACKGROUND AND METHODS

Alinidine is a recently developed antiarrhythmic medication that acts directly on the cardiac pacemaker cells to reduce heart rate (HR). At effective doses, alinidine might have cardiodepressant actions that could be hazardous in the presence of hemodynamic instability. On the other hand, one limitation of the use of catecholamines is tachycardia, and alinidine could be beneficial in situations such as septic shock, where adrenergic agents are commonly required. The present study explored the hemodynamic and gasometric effects of alinidine during dobutamine administration in a canine model of septic shock induced by endotoxin administration. In ten pentobarbital-anesthetized, mechanically ventilated dogs (weight 28 +/- 4 kg), Escherichia coli endotoxin (3 mg/kg) injection was followed 30 mins later by saline infusion to restore and maintain pulmonary artery occlusion pressure at the baseline value. Sixty minutes after the endotoxin administration, a dobutamine infusion was started at a rate of 10 micrograms/kg/min. Thirty minutes later, alinidine was administered as a bolus dosage of 1 mg/kg in five dogs; the other five dogs served as a control group.

RESULTS

Alinidine administration resulted in a decrease in HR from 157 +/- 20 to 138 +/- 27 beats/min (p less than .01) and a nonsignificant increase in cardiac output from 5.2 +/- 3.0 to 6.8 +/- 2.8 L/min, as a consequence of increases in stroke volume from 31.9 +/- 15.3 to 49.2 +/- 13.9 mL (p less than .01) and in left ventricular stroke work from 32.1 +/- 20.0 to 57.4 +/- 32.1 g.m (p less than .05).

CONCLUSIONS

During experimental septic shock, alinidine administration can reverse dobutamine-induced tachycardia and simultaneously improve ventricular function.