Are the effects of noradrenaline, adrenaline and dopamine infusions on VO2 and metabolism transient?

Considering whole-body metabolism in hyperpolarized MRI through 13 C breath analysis-An alternative way to quantification and normalization?

PURPOSE

Hyperpolarized [1-¹³ C]pyruvate MRI is an emerging clinical tool for metabolic imaging. It has the potential for absolute quantitative metabolic imaging. However, the method itself is not quantitative, limiting comparison of images across both time and between individuals. Here, we propose a simple signal normalization to the whole-body oxidative metabolism to overcome this limitation.

THEORY AND METHODS

A simple extension of the model-free ratiometric analysis of hyperpolarized [1-¹³ C]pyruvate MRI is presented, using the expired ¹³ CO₂ in breath for normalization. The proposed framework was investigated in two porcine cohorts (N = 11) subjected to local renal hypoperfusion defects and subsequent [1-¹³ C]pyruvate MRI. A breath sample was taken before the [1-¹³ C]pyruvate injection and 5 min after. The raw MR signal from both the healthy and intervened kidney in the two cohorts was normalized using the ¹³ CO₂ in the expired air.

RESULTS

¹³ CO₂ content in the expired air was significantly different between the two cohorts. Normalization to this reduced the coefficients of variance in the aerobic metabolic sensitive pathways by 25% for the alanine/pyruvate ratio, and numerical changes were observed in the bicarbonate/pyruvate ratio. The lactate/pyruvate ratio was largely unaltered (<2%).

CONCLUSION

Our results indicate that normalizing the hyperpolarized ¹³ C-signal ratios by the ¹³ CO₂ content in expired air can reduce variation as well as improve specificity of the method by normalizing the metabolic readout to the overall metabolic status of the individual. The method is a simple and cheap extension to the hyperpolarized ¹³ C exam.

Sufentanil: a risk factor for lactic acidosis in patients after heart valve surgery

Backgrounds

Hyperlactatemia is a common metabolic disorder after cardiac surgery with cardiopulmonary bypass. Epinephrine use has been identified as a potential cause of increased lactate levels after cardiac surgery. Stress can lead to an increase in catecholamines, mainly epinephrine, in the body. Exogenous epinephrine causes hyperlactatemia, whereas endogenous epinephrine released by stress may have the same effect. Opioids are the most effective anesthetics to suppress the stress response in the body. The authors sought to provide evidence through a retrospective data analysis that helps investigate the relationship between intraoperative opioid dosage and postoperative lactic acidosis after cardiac surgery.

Methods

The clinical data of 215 patients who underwent valvular heart surgery with cardiopulmonary bypass from July 2016 to July 2019 were analyzed retrospectively. Blood lactate levels were measured at 0.1 h, 2 h, 4 h, and 8 h after surgery. Patients with continuous increases in lactate levels and lactate levels exceeding 5 mmol/L at two or more time points were included in the lactic acidosis group, whereas the other patients were included in the control group. First, univariate correlation analysis was used to identify parameters that were significantly different between the two groups, and then multivariate regression analysis was conducted to elucidate the independent risk factors for lactic acidosis. Fifty-one pairs of patients were screened by propensity score matching analysis (PSM). Then, lactic acid levels at four time points in both groups were analyzed by repeated measures ANOVA.

Results

he EF (heart ejection fraction) (OR = 0.94, P = 0.003), aortic occlusion time (OR = 10.17, P < 0.001) and relative infusion rate (OR = 2.23, P = 0.01) of sufentanil was an independent risk factor for lactic acidosis after valvular heart surgery. The patients were further divided into two groups with the mean sufentanil infusion rate as the reference point. The data were filtered with PSM (Propensity Score Matching). Lactic acid values in both groups peaked at 4 h after surgery and then declined. The rate of lactic acid decline was significantly faster in the group with a higher sufentanil dosage than in the lower group. The difference was statistically significant (P < 0.05). There was also a significant difference in lactic acid levels at the four time points (0.1 h, 2 h, 4 h and 8 h after surgery) in both groups (P < 0.001).

Conclusion

The inadequate intraoperative infusion rate of sufentanil is an independent risk factor for lactic acidosis after heart valve surgery. The possibility of lactic acidosis caused by this factor after cardiac surgery should be considered, which is helpful for postoperative patient management.

Acute effects of whole body vibration exercise on post-load glucose metabolism in healthy men: a pilot randomized crossover trial

PURPOSE

Exercise on a whole body vibration (WBV) platform, namely WBV exercise (WBVE), has long-term beneficial effects on glucose metabolism, similarly to conventional moderate-intensity exercise. Conventional moderate-intensity exercise reduces post-load plasma glucose levels at the acute phase. This study aimed to reveal acute effects of WBVE on post-load glucose metabolism.

METHODS

This randomized crossover trial enrolled 18 healthy men. They completed the following three interventions in a random order: (1) a 2-hour 75-g oral glucose tolerance test (OGTT) without WBVE (OGTT-alone), (2) 20-minute WBVE before an OGTT (WBVE → OGTT), and (3) 20-minute WBVE during an OGTT (OGTT → WBVE). Post-load glucose metabolism in the WBVE → OGTT and OGTT → WBVE interventions were compared with that in the OGTT-alone intervention.

RESULTS

Plasma glucose levels in the WBVE → OGTT and OGTT → WBVE interventions were not significantly different from those in the OGTT-alone intervention at any time point except 15 min, wherein the WBVE → OGTT intervention had higher glucose levels (111 [interquartile range, 102-122] mg/dL vs 122 [111-134] mg/dL, P = 0.026). Higher plasma glucagon levels were observed at 0 min in the WBVE → OGTT intervention and at 60 min in the OGTT → WBVE intervention (P = 0.010 and 0.015). Cortisol, Growth hormone, and adrenaline levels were significantly increased after WBVE, whereas noradrenaline levels were not. Serum insulin levels in the WBVE → OGTT intervention were significantly higher than those in the OGTT-alone intervention at 0 min (P = 0.008).

CONCLUSIONS

WBVE did not decrease post-load plasma glucose levels at the acute phase. Acute effects of WBVE on post-load glucose metabolism would not be identical to those of conventional exercise. The unique trial number and the name of the registry: UMIN000036520, www.umin.ac.jp , date of registration, June 12, 2019.

Association between dose of catecholamines and markers of organ injury early after out-of-hospital cardiac arrest

BACKGROUND

Catecholamines are recommended as first-line drugs to treat hemodynamic instability after out-of-hospital cardiac arrest (OHCA). The benefit-to-risk ratio of catecholamines is dose dependent, however, their effect on metabolism and organ function early after OHCA has not been investigated.

METHODS

The Post-Cardiac Arrest Syndrome (PCAS) pilot study was a prospective, observational, multicenter study. The primary outcomes of this analysis were association between norepinephrine/cumulative catecholamines doses and neuron specific enolase (NSE)/lactate concentration over the first 72 hours after resuscitation. The association was adjusted for proven OHCA mortality predictors and verified with propensity score matching (PSM).

RESULTS

Overall 148 consecutive OHCA patients; aged 18-91 (62.9 ± 15.27), 41 (27.7%) being female, were included. Increasing norepinephrine and cumulative catecholamines doses were significantly associated with higher NSE concentration on admission (r = 0.477, p < 0.001; r = 0.418, p < 0.001) and at 24 hours after OHCA (r = 0.339, p < 0.01; r = 0.441, p < 0.001) as well as with higher lactate concentration on admission (r = 0.404, p < 0.001; r = 0.280, p < 0.01), at 24 hours (r = 0.476, p < 0.00; r = 0.487, p < 0.001) and 48 hours (r = 0.433, p < 0.01; r = 0.318, p = 0.01) after OHCA. The associations remained significant up to 48 hours in non-survivors after PSM.

CONCLUSIONS

Increasing the dose of catecholamines is associated with higher lactate and NSE concentration, which may suggest their importance for tissue oxygen delivery, anaerobic metabolism, and organ function early after OHCA.

The acute effect of dopamine infusion on lipid and cytokine concentrations in persons with a cervical spinal cord injury-a pilot study

STUDY DESIGN

Acute experimental study.

OBJECTIVES

To investigate the acute response of markers of lipid metabolism and interleukin (IL)-6 to dopamine infusion in people with a cervical spinal cord injury (CSCI).

SETTING

Laboratory of Wakayama Medical University, Japan.

METHODS

Ten participants, four with CSCI and six AB individuals, underwent 50 min of dopamine infusion. Blood samples were collected prior to, immediately after and 1 h following cessation of dopamine infusion for the determination of circulating catecholamine, lipid, ketone body and IL-6 concentrations.

RESULTS

The adrenaline concentration following dopamine infusion was increased by 59 ± 7% in CSCI (p = 0.038, Cohen's d effect size (ES): 1.47), while this was not changed in AB (p = 0.223). Triglycerides and acetoacetic acid concentration were increased in both groups, immediately after and 1 h post-infusion (triglycerides p ≤ 0.042, ES CSCI: 1.00, ES AB: 1.12; acetoacetic acid p ≤ 0.030; ES CSCI: 1.72, ES AB: 1.31). 3-Hydroxybutyric acid concentration was increased in CSCI only (48 ± 15%, p = 0.039, ES: 1.44; AB p = 0.115). Dopamine infusion did not affect plasma IL-6 concentration in either group (p ≥ 0.368).

CONCLUSIONS

Dopamine infusion induced a sustained increase in triglyceride and ketone body concentrations in persons with CSCI. In contrast, cytokine concentrations were not affected by dopamine infusion. These findings suggest that circulating catecholamines can stimulate metabolism in people with CSCI despite the presence of autonomic dysfunction.

The role of vasopressin and the vasopressin type V1a receptor agonist selepressin in septic shock

Septic shock remains one of the major causes of morbidity and mortality in the critically ill. Despite early goal therapy and administration of cathecholaminergic agents, up to 30% of patients succumb to the disease. In this manuscript, we first summarize the standard of care of patients with septic shock and current guidelines. We review the physiologic role of vasopressin and its role in septic shock management. We then review the most up-to-date evidence on the potential role of V1a receptor agonists such as Selepressin, in septic shock. Exciting new trials are being completed in order to elucidate the role of V1a receptor agonists as potential first-line vasopressor alternatives in the therapy of circulatory shock in septic patients.

Clinical significance of lactate in acute cardiac patients

Lactate, as a metabolite of easy and quick assessment, has been studied over time in critically ill patients in order to evaluate its prognostic ability. The present review is focused on the prognostic role of lactate levels in acute cardiac patients (that is with acute coronary syndrome, cardiogenic shock, cardiac arrest, non including post cardiac surgery patients). In patients with ST-elevation myocardial infarction treated with mechanical revascularization, hyperlactatemia identified a subset of patients at higher risk for early death and in-hospital complications, being strictly related mainly to hemodynamic derangement. The prognostic impact of hyperlactatemia on mortality has been documented in patients with cardiogenic shock and in those with cardiac arrest even if there is no cut-off value of lactate to be associated with worse outcome or to guide resuscitation or hemodynamic management. Therapeutic hypothermia seems to affect per se lactate values which have been shown to progressively decrease during hypothermia. The mechanism(s) accounting for lactate levels during hypothemia seem to be multiple ranging from the metabolic effects of reduced temperatures to the hemodynamic effects of hypothermia (i.e., reduced need of vasopressor agents). Serial lactate measurements over time, or lactate clearance, have been reported to be clinically more reliable than lactate absolute value also in acute cardiac patients. Despite differences in study design, timing of lactate measurements and type of acute cardiac conditions (i.e., cardiogenic shock, cardiac arrest, refractory cardiac arrest), available evidence strongly suggests that higher lactate levels can be observed on admission in non-survivors and that higher lactate clearance is associated with better outcome.

Dynamic behaviour of lactate values during mild hypothermia in patients with cardiac arrest

BACKGROUND AND METHODS

The present investigation was aimed at assessing the dynamic behaviour of lactate values during hypothermia in 33 patients with cardiac arrest.

RESULTS

Fifteen patients died during intensive care stay (15/33, 45.5%). When compared to survivors, they were older (survivors 50.7 ± 14.7 vs. non-survivors 70.1 ± 10.4 years, p<0.001) and exhibited a significantly higher APACHE score (survivors 21.9 ± 3.9 vs. non-survivors 27.5 ± 4.6, p<0.001). A higher incidence of non-shockable rhythms was observed in non-survivors (p=0.026) who showed a longer collapse-recovery of spontaneous circulation time (p=0.01). During hypothermia, lactate values showed a progressive and significant decrease despite no significant change in mean arterial pressure and central venous pressure (i.e. independently of blood pressure values and volaemia). Lactate values when measured during hypothermia were related to in-intensive cardiac care unit (in-ICCU) death.

CONCLUSION

In our series, lactate values measured during hypothermia hold a prognostic role in these patients since they are related to in-ICCU death.

Association of serum lactate and survival outcomes in patients undergoing therapeutic hypothermia after cardiac arrest

INTRODUCTION

Recent studies have suggested that serum lactate may serve as a marker to predict mortality after resuscitation from cardiac arrest (CA). The relationship between serum lactate and CA outcomes requires further characterization, especially among patients treated with therapeutic hypothermia (TH) and aggressive post-arrest care.

METHODS

A retrospective analysis of patients resuscitated from non-traumatic CA at three urban U.S. hospitals was performed using an established internet-based post-arrest registry. Adult (≥ 18 years) patients resuscitated from CA and receiving TH treatment were included. Logistic regression analysis was used to adjust for potential confounders to survival outcomes. Survival to discharge served as the primary endpoint.

RESULTS

A total of 199 post-CA patients treated with TH between 5/2005 and 11/2011 were included in this analysis. The mean age was 56.9 ± 16.5 years, 85/199 (42.7%) patients were female, and survival to discharge was attained in 84/199 (42.2%). While lower initial post-CA serum lactate levels were not associated with increased survival to discharge, subsequent lactate measurements were significantly associated with outcomes (24-h serum lactate levels in survivors vs. non-survivors, 2.7 ± 0.5 vs. 4.2 ± 0.4 mmol/L, p<0.01). Multivariable logistic regression confirmed this relationship with survival to discharge (p<0.01).

CONCLUSION

Lower serum lactate levels at 12h and 24h, but not initially following cardiac arrest, are associated with survival to hospital discharge after resuscitation from CA and TH treatment. Prospective investigation of serum lactate as a potential prognostic tool in CA is needed.

Use of inotropes and vasopressor agents in critically ill patients

Inotropes and vasopressors are biologically and clinically important compounds that originate from different pharmacological groups and act at some of the most fundamental receptor and signal transduction systems in the body. More than 20 such agents are in common clinical use, yet few reviews of their pharmacology exist outside of physiology and pharmacology textbooks. Despite widespread use in critically ill patients, understanding of the clinical effects of these drugs in pathological states is poor. The purpose of this article is to describe the pharmacology and clinical applications of inotropic and vasopressor agents in critically ill patients.

Comparison of norepinephrine-dobutamine to epinephrine for hemodynamics, lactate metabolism, and organ function variables in cardiogenic shock. A prospective, randomized pilot study

OBJECTIVE

There is no study that has compared, in a randomized manner, which vasopressor is most suitable in optimizing both systemic and regional hemodynamics in cardiogenic shock patients. Hence, the present study was designed to compare epinephrine and norepinephrine-dobutamine in dopamine-resistant cardiogenic shock.

DESIGN

Open, randomized interventional human study.

SETTING

Medical intensive care unit in a university hospital.

PATIENTS

Thirty patients with a cardiac index of <2.2 L/min/m and a mean arterial pressure of <60 mm Hg resistant to combined dopamine-dobutamine treatment and signs of shock. Patients were not included in cases of cardiogenic shock secondary to acute ischemic events such as myocardial infarction. Noninclusion criteria also included immediate indication of mechanical assistance.

INTERVENTIONS

Patients were randomized to receive an infusion of either norepinephrine-dobutamine or epinephrine titrated to obtain a mean arterial pressure of between 65 and 70 mm Hg with a stable or increased cardiac index.

MAIN RESULTS

Both regimens increased cardiac index and oxygen-derived parameters in a similar manner. Patients in the norepinephrine-dobutamine group demonstrated heart rates lower (p<.05) than those in the epinephrine group. Epinephrine infusion was associated with new arrhythmias in three patients. When compared to baseline values, after 6 hrs, epinephrine infusion was associated with an increase in lactate level (p<.01), whereas this level decreased in the norepinephrine-dobutamine group. Tonometered PCO2 gap, a surrogate for splanchnic perfusion adequacy, increased in the epinephrine-treated group (p<.01) while decreasing in the norepinephrine group (p<.01). Diuresis increased in both groups but significantly more so in the norepinephrine-dobutamine group, whereas plasma creatinine decreased in both groups.

CONCLUSIONS

When considering global hemodynamic effects, epinephrine is as effective as norepinephrine-dobutamine. Nevertheless, epinephrine is associated with a transient lactic acidosis, higher heart rate and arrhythmia, and inadequate gastric mucosa perfusion. Thus, the combination norepinephrine-dobutamine appears to be a more reliable and safer strategy.

Sympathetic overstimulation during critical illness: adverse effects of adrenergic stress

The term ''adrenergic'' originates from ''adrenaline'' and describes hormones or drugs whose effects are similar to those of epinephrine. Adrenergic stress is mediated by stimulation of adrenergic receptors and activation of post-receptor pathways. Critical illness is a potent stimulus of the sympathetic nervous system. It is undisputable that the adrenergic-driven ''fight-flight response'' is a physiologically meaningful reaction allowing humans to survive during evolution. However, in critical illness an overshooting stimulation of the sympathetic nervous system may well exceed in time and scope its beneficial effects. Comparable to the overwhelming immune response during sepsis, adrenergic stress in critical illness may get out of control and cause adverse effects. Several organ systems may be affected. The heart seems to be most susceptible to sympathetic overstimulation. Detrimental effects include impaired diastolic function, tachycardia and tachyarrhythmia, myocardial ischemia, stunning, apoptosis and necrosis. Adverse catecholamine effects have been observed in other organs such as the lungs (pulmonary edema, elevated pulmonary arterial pressures), the coagulation (hypercoagulability, thrombus formation), gastrointestinal (hypoperfusion, inhibition of peristalsis), endocrinologic (decreased prolactin, thyroid and growth hormone secretion) and immune systems (immunomodulation, stimulation of bacterial growth), and metabolism (increase in cell energy expenditure, hyperglycemia, catabolism, lipolysis, hyperlactatemia, electrolyte changes), bone marrow (anemia), and skeletal muscles (apoptosis). Potential therapeutic options to reduce excessive adrenergic stress comprise temperature and heart rate control, adequate use of sedative/analgesic drugs, and aiming for reasonable cardiovascular targets, adequate fluid therapy, use of levosimendan, hydrocortisone or supplementary arginine vasopressin.

Glucose metabolism and catecholamines

Until now, catecholamines were the drugs of choice to treat hypotension during shock states. Catecholamines, however, also have marked metabolic effects, particularly on glucose metabolism, and the degree of this metabolic response is directly related to the beta2-adrenoceptor activity of the individual compound used. Under physiologic conditions, infusing catecholamine is associated with enhanced rates of aerobic glycolysis (resulting in adenosine triphosphate production), glucose release (both from glycogenolysis and gluconeogenesis), and inhibition of insulin-mediated glycogenesis. Consequently, hyperglycemia and hyperlactatemia are the hallmarks of this metabolic response. Under pathophysiologic conditions, the metabolic effects of catecholamines are less predictable because of changes in receptor affinity and density and in drug kinetics and the metabolic capacity of the major gluconeogenic organs, both resulting from the disease per se and the ongoing treatment. It is also well-established that shock states are characterized by a hypermetabolic condition with insulin resistance and increased oxygen demands, which coincide with both compromised tissue microcirculatory perfusion and mitochondrial dysfunction. This, in turn, causes impaired glucose utilization and may lead to inadequate glucose supply and, ultimately, metabolic failure. Based on the landmark studies on intensive insulin use, a crucial role is currently attributed to glucose homeostasis. This article reviews the effects of the various catecholamines on glucose utilization, both under physiologic conditions, as well as during shock states. Because, to date (to our knowledge), no patient data are available, results from relevant animal experiments are discussed. In addition, potential strategies are outlined to influence the catecholamine-induced effects on glucose homeostasis.

Metabolic effects of vasoactive agents

After adequate volume resuscitation, the mainstay of therapy in critically ill patients with shock is treatment with vasoactive substances to restore haemodynamics or to improve regional perfusion. These agents include adrenoceptor agonists with inotropic combined with either vasoconstricting or vasodilating effects, and predominantly vasodilating drugs such as prostacyclin and related compounds. However, vasoactive agents not only affect the cardiovascular system, but also have profound metabolic effects. The interdependence of vasoactive drugs with metabolism may be relevant regarding adequate oxygen and substrate delivery to cover actual organ needs. Therefore, the profiles of these metabolic effects have to be considered during their therapeutic administration.

Bench-to-bedside review: Is there a place for epinephrine in septic shock?

The use of epinephrine in septic shock remains controversial. Nevertheless, epinephrine is widely used around the world and the reported morbidity and mortality rates with it are no different from those observed with other vasopressors. In volunteers, epinephrine increases heart rate, mean arterial pressure and cardiac output. Epinephrine also induces hyperglycemia and hyperlactatemia. In hyperkinetic septic shock, epinephrine consistently increases arterial pressure and cardiac output in a dose dependent manner. Epinephrine transiently increases lactate levels through an increase in aerobic glycolysis. Epinephrine has no effect on splanchnic circulation in dopamine-sensitive septic shock. On the other hand, in dopamine-resistant septic shock, epinephrine has no effect on tonometric parameters but decreases fractional splanchnic blood flow with an increase in the gradient of mixed venous oxygen saturation (SVO₂) and hepatic venous oxygen saturation (SHO₂). In conclusion, epinephrine has predictable effects on systemic hemodynamics and is as efficient as norepinephrine in correcting hemodynamic disturbances of septic shock. Moreover, epinephrine is cheaper than other commonly used catecholamine regimens in septic shock. The clinical impact of the transient hyperlactatemia and of the splanchnic effects are not established.

EFFECTS OF DOPAMINE AND NOREPINEPHRINE ON SYSTEMIC AND HEPATOSPLANCHNIC HEMODYNAMICS, OXYGEN EXCHANGE, AND ENERGY BALANCE IN VASOPLEGIC SEPTIC PATIENTS

Dopamine is widely used to improve systemic and hepatosplanchnic hemodynamics and oxygenation during sepsis. However, some studies have suggest that norepinephrine may have beneficial effects on regional blood flow and metabolism, whereas dopamine might have deleterious effects related to redistribution of blood flow away from the intestinal mucosa or by decreasing directly the cell redox state. In 12 vasoplegic septic patients, we compared the effects of norepinephrine and dopamine on systemic and hepatosplanchnic hemodynamics, oxygenation, and energy metabolism. Catecholamines were administered in a crossover randomized order to maintain mean arterial pressure (MAP) at 80 mmHg. Hepatosplanchnic blood flow (Qspl) was determined using a continuous infusion of indocyanine green dye. Despite a similar MAP, the cardiac index was higher with dopamine than with norepinephrine (6.3 [5.3-7.3] vs. 4.3 [3.8-4.9] L.min.m) (P <0.001). Qspl was similar with both catecholamines, but the ratio of Qspl to cardiac output was significantly lower with dopamine (23.9% [17.5-33.5]) than with norepinephrine (33.5% [25.8-37]) (P <0.05). Although global O2 delivery and O2 consumption were higher with dopamine (782 [707-859] vs. 553 [512-629] mL.min.m, P <0.001 and 164 [134-192] vs. 128 [111-149] mL.min.m, P <0.001, respectively), hepatosplanchnic O2 delivery and consumption were not different. Hepatic lactate uptake was lower (0.47 [0.3-0.89] vs. 1.01 [0.69-1.34] mmol.min) (P <0.01), and hepatic venous lactate-to-pyruvate ratio was higher (15.3 [7.6-21.1] vs. 11.2 [6.6-15.1], P <0.05) with dopamine than with norepinephrine. In vasoplegic septic patients, maintaining mean arterial pressure, hepatosplanchnic hemodynamics, and oxygen exchange with dopamine requires a consequent increased cardiac output, which is responsible for an increased global oxygen demand when compared with norepinephrine. In addition, dopamine impairs the hepatic energy balance. Its position as a preferential treatment compared with norepinephrine in this context may therefore be questionable.

Compared to angiotensin II, epinephrine is associated with high myocardial blood flow following return of spontaneous circulation after cardiac arrest

INTRODUCTION

Epinephrine (adrenaline) and vasopressin are used currently to improve myocardial blood flow (MBF) during cardiac arrest. Angiotensin II has also been shown to improve MBF during CPR. We explored the effects of angiotensin II or epinephrine alone, and the combination of angiotensin with epinephrine, on myocardial and cerebral blood flows in a swine model of cardiac arrest.

METHODS

Swine were instrumented for regional blood flow measurements. Ventricular fibrillation was induced and CPR begun. Angiotensin II 50 mcg/kg (ANG), epinephrine 0.02 mg/kg (EPI) or the combination (ANG+EPI) was administered. Blood flow was measured during baseline normal sinus rhythm (NSR), before (CPR) and after drug administration (CPR+DRUG), and post reperfusion return of spontaneous circulation (ROSC).

RESULTS

All groups had a significant increase in MBF during CPR following drug administration (P<0.05). [table: see text] There was a trend toward higher flows in the EPI groups. The group receiving both EPI and ANG did not have higher blood flows than the EPI or ANG alone groups. Both groups that received EPI had markedly elevated MBF following ROSC compared with angiotensin II (P<0.05).

CONCLUSIONS

The combination of ANG and EPI did not improve MBF during cardiac arrest. Epinephrine may increase MBF compared with angiotensin II post-reperfusion.

Effects of dopamine, norepinephrine, and epinephrine on the splanchnic circulation in septic shock: which is best?

OBJECTIVE

To assess the effects of different doses of dopamine, norepinephrine, and epinephrine on the splanchnic circulation in patients with septic shock.

DESIGN

Prospective, randomized, open-label study.

SETTING

A 31-bed, medicosurgical intensive care unit of a university hospital.

PATIENTS

Convenience sample of 20 patients with septic shock, separated into two groups according to whether (moderate shock group, n = 10) or not (severe shock, n = 10) dopamine alone was able maintain mean arterial pressure >65 mm Hg.

INTERVENTIONS

Dopamine was progressively withdrawn and replaced successively by norepinephrine and then epinephrine (the order of the two agents was randomly determined) to maintain mean arterial pressure constant (moderate shock) or to increase mean arterial pressure above 65 mm Hg (severe shock).

MEASUREMENTS AND MAIN RESULTS

Systemic circulation (pulmonary artery catheter) and splanchnic circulation (indocyanine green dilution and hepatic vein catheter) and gastric mucosal Pco(2) (gas tonometry) were measured during dopamine (moderate shock only), norepinephrine, and epinephrine administration (both groups). Data were analyzed with nonparametric tests and are presented as median [percentiles 25-75]. In moderate shock, cardiac index was similar to dopamine and norepinephrine (3.1 [2.7-3.8] vs. 2.9 [2.7-4.1] L/min.m2, p = nonsignificant) but greater with epinephrine (4.1 [3.5-4.4] p <.01 vs. dopamine and norepinephrine). Splanchnic blood flow was similar with the three agents (732 [413-1483] vs. 746 [470-1401] vs. 653 [476-1832] mL/min.m, p = nonsignificant). The gradient between mixed-venous and hepatic venous oxygen saturations was lower with dopamine than with norepinephrine and epinephrine, but the Pco(2) gap was similar with the three agents. In severe shock, cardiac index was higher, but splanchnic blood flow was lower, with epinephrine than with norepinephrine (4.6 [3.7-5.3] vs. 3.4 [3.0-4.1] L/min.m2, p <.01 and 860 [684-1334] vs. 977 [806-1802] mL/min.m2, p <.05, respectively). Epinephrine increased the mixed-venous and hepatic venous oxygen saturation gradient but did not alter Pco(2) gap.

CONCLUSIONS

Dopamine and norepinephrine have similar hemodynamic effects, but epinephrine can impair splanchnic circulation in severe septic shock.

Effects of epinephrine and norepinephrine on hemodynamics, oxidative metabolism, and organ energetics in endotoxemic rats

OBJECTIVE

To determine whether epinephrine increases lactate concentration in sepsis through hypoxia or through a particular thermogenic or metabolic pathway.

DESIGN

Prospective, controlled experimental study in rats.

SETTING

Experimental laboratory in a university teaching hospital.

INTERVENTIONS

Three groups of anesthetized, mechanically ventilated male Wistar rats received an intravenous infusion of 15 mg/kg Escherichia coli O127:B8 endotoxin. Rats were treated after 90 min by epinephrine ( n=14), norepinephrine ( n=14), or hydroxyethyl starch ( n=14). Three groups of six rats served as time-matched control groups and received saline, epinephrine, or norepinephrine from 90 to 180 degrees min. Mean arterial pressure, aortic, renal, mesenteric and femoral blood flow, arterial blood gases, lactate, pyruvate, and nitrate were measured at baseline and 90 and 180 min after endotoxin challenge. At the end of experiments biopsy samples were taken from the liver, heart, muscle, kidney, and small intestine for tissue adenine nucleotide and lactate/pyruvate measurements.

MEASUREMENTS AND RESULTS

Endotoxin induced a decrease in mean arterial pressure and in aortic, mesenteric, and renal blood flow. Plasmatic and tissue lactate increased with a high lactate/pyruvate (L/P) ratio. ATP decreased in liver, kidney, and heart. The ATP/ADP ratio did not change, and phosphocreatinine decreased in all organs. Epinephrine and norepinephrine increased mean arterial pressure to baseline values. Epinephrine increased aortic blood flow while renal blood low decreased with both drugs. Plasmatic lactate increased with a stable L/P ratio with epinephrine and did not change with norepinephrine compared to endotoxin values. Nevertheless epinephrine and norepinephrine when compared to endotoxin values did not change tissue L/P ratios or ATP concentration in muscle, heart, gut, or liver. In kidney both drugs decreased ATP concentration.

CONCLUSIONS

Our data demonstrate in a rat model of endotoxemia that epinephrine-induced hyperlactatemia is not related to cellular hypoxia.

Metabolic effects of norepinephrine and dobutamine in healthy volunteers

The objective of the present study was to evaluate the effects of norepinephrine (n = 9) and dobutamine (n = 7) on carbohydrate and protein metabolism in healthy volunteers in comparison with a control group (n = 9). Norepinephrine (0.1 microg/kg min), dobutamine (5 microg/kg min), or placebo was infused for 240 min. The plasma concentration of glucose, lactate, epinephrine, norepinephrine, insulin, and glucagon were determined. Glucose and urea production and leucine flux were measured using a tracer technique. Norepinephrine caused a persisting rise in plasma glucose concentration, whereas the increase in glucose production was only transient. A minor increase in plasma lactate concentration was observed, but it did not exceed the physiological range. No change in leucine flux, urea production, or plasma concentration of insulin, glucagon, or epinephrine was found. Dobutamine slightly decreased glucose production, whereas the plasma concentration of glucose and lactate did not change. The reduction in leucine flux was paralleled by a decrease in urea production. No change in the plasma concentration of insulin, glucagon, or the catecholamines was observed. In conclusion, both norepinephrine and dobutamine have only minor metabolic effects. Because glucose production is enhanced by alpha1- and beta2-adrenoceptor stimulation, we conclude that dobutamine is only a weak agonist at these adrenoceptors. These minor metabolic actions may make both compounds suitable for critically ill patients because no further increase in metabolic rate should be caused.

Effects of epinephrine on intestinal oxygen supply and mucosal tissue oxygen tension in pigs

OBJECTIVE

To study the effects of increasing dosages of epinephrine given intravenously on intestinal oxygen supply and, in particular, mucosal tissue oxygen tension in an autoperfused, innervated jejunal segment.

DESIGN

Prospective, randomized experimental study.

SETTING

Animal research laboratory.

SUBJECTS

Domestic pigs.

INTERVENTIONS

Sixteen pigs were anesthetized, paralyzed, and normoventilated. A small segment of the jejunal mucosa was exposed by midline laparotomy and antimesenteric incision. Mucosal oxygen tension was measured by using Clark-type surface oxygen electrodes. Microvascular hemoglobin oxygen saturation and microvascular blood flow (perfusion units) were determined by tissue reflectance spectrophotometry and laser-Doppler velocimetry. Systemic hemodynamics, mesenteric-venous acid-base and blood gas variables, and systemic acid-base and blood gas variables were recorded. Measurements were performed after a resting period and at 20-min intervals during infusion of increasing dosages of epinephrine (n = 8; 0.01, 0.05, 0.1, 0.5, 1, and 2 microg x kg(-1) x min(-1)) or without treatment (n = 8). In addition, arterial and mesenteric-venous lactate concentrations were measured at baseline and at 60 and 120 mins.

MEASUREMENTS AND MAIN RESULTS

Epinephrine infusion led to significant tachycardia; an increase in cardiac output, systemic oxygen delivery, and oxygen consumption; and development of lactic acidosis. Epinephrine significantly increased jejunal microvascular blood flow (baseline, 267 +/- 39 perfusion units; maximum value, 443 +/- 35 perfusion units) and mucosal oxygen tension (baseline, 36 +/- 2.0 torr [4.79 +/- 0.27 kPa]; maximum value, 48 +/- 2.8 torr [6.39 +/- 0.37 kPa]) and increased hemoglobin oxygen saturation above baseline. Epinephrine increased mesenteric venous lactate concentration (baseline, 2.9 +/- 0.6 mmol x L(-1); maximum value, 5.5 +/- 0.2 mmol x L(-1)) without development of an arterial-mesenteric venous lactate concentration gradient.

CONCLUSIONS

Epinephrine increased jejunal microvascular blood flow and mucosal tissue oxygen supply at moderate to high dosages. Lactic acidosis that develops during infusion of increasing dosages of epinephrine is not related to development of gastrointestinal hypoxia.

Evolution of lactate/pyruvate and arterial ketone body ratios in the early course of catecholamine-treated septic shock

OBJECTIVES

To measure arterial lactate/pyruvate (L/P) and arterial ketone body ratios as reflection of cytoplasmic and mitochondrial redox state at different stages of catecholamine-treated septic shock and compare them with normal and pathologic values obtained in patients in shock who have decreased oxygen transport (cardiogenic shock), and to assess the relationship between the time course of lactate, L/P ratio, and mortality in septic shock.

DESIGN

Prospective, observational human study.

SETTING

A university intensive care unit.

PATIENTS

Sixty consecutive adult patients who developed septic shock and lactic acidosis requiring the administration of vasopressors. Twenty patients in the intensive care unit without shock, sepsis, and hypoxia and with normal lactate values and 10 patients with cardiogenic shock were also studied.

MEASUREMENTS

Hemodynamic measurements, arterial and mixed venous blood gases, arterial lactate and pyruvate concentrations, and arterial ketone body ratio were measured within 4 hrs after the introduction of catecholamine and 24 hrs later.

MAIN RESULTS

Fifteen patients (25%) died within the first 24 hrs of septic shock, and these early fatalities had a higher blood lactate (12.2+/-3 versus 4.6+/-1.3 mmol/L; p<.01) concentration and a higher L/P ratio (37+/-4 versus 20+/-1; p<.01) than those who died later. No difference was found for arterial ketone body ratio (0.41+/-0.1 versus 0.50+/-0.06). Forty-five patients survived >24 hrs including 25 survivors and 20 nonsurvivors. Although there was no difference between survivors and nonsurvivors in initial lactate concentration (4.1+/-0.4 and 4.6+/-0.3, respectively), L/P ratio (19+/-1 and 20+/-1, respectively), and arterial ketone body ratio (0.5+/-0.06 and 0.52+/-0.07, respectively), blood lactate and L/P ratio significantly decreased during the first 24 hrs in the survivors (2.8+/-0.4 and 14+/-1, respectively; p<.05). and were stable in the nonsurvivors (4+/-0.3 and 22+/-1, respectively) Although returning to normal values after 24 hrs in survivors and nonsurvivors, arterial ketone body ratio was higher in survivors (1.72+/-0.17 versus 1.09+/-0.15; p<.05). Lactate and L/P ratio were closely correlated (r2 = .8, p<.0001). In the cardiogenic shock group, lactate concentration was 4+/-1 mmol/L, L/P ratio was 40+/-6, and arterial ketone body ratio was 0.2+/-0.05. The mortality rate was 60%.

CONCLUSIONS

The main result of the present study is that hemodynamically unstable patients with sepsis needing catecholamine therapy had a lactic acidosis with an elevated L/P ratio and a decreased arterial ketone body ratio, suggesting a decrease in cytoplasmic and mitochondrial redox state. The duration of lactic acidosis is associated with the development of multiple organ failure and death.

Women at altitude: energy requirement at 4,300 m

To test the hypotheses that prolonged exposure to moderately high altitude increases the energy requirement of adequately fed women and that the sole cause of the increase is an elevation in basal metabolic rate (BMR), we studied 16 healthy women [21.7 +/- 0.5 (SD) yr; 167.4 +/- 1.1 cm; 62.2 +/- 1.0 kg]. Studies were conducted over 12 days at sea level (SL) and at 4,300 m [high altitude (HA)]. To test that menstrual cycle phase has an effect on energetics at HA, we monitored menstrual cycle in all women, and most women (n = 11) were studied in the same phase at SL and HA. Daily energy intake at HA was increased to respond to increases in BMR and to maintain body weight and body composition. Mean BMR for the group rose 6.9% above SL by day 3 at HA and fell to SL values by day 6. Total energy requirement remained elevated 6% at HA [ approximately 670 kJ/day (160 kcal/day) above that at SL], but the small and transient increase in BMR could not explain all of this increase, giving rise to an apparent "energy requirement excess." The transient nature of the rise in BMR may have been due to the fitness level of the subjects. The response to altitude was not affected by menstrual cycle phase. The energy requirement excess is at present unexplained.

Hemodynamic response to norepinephrine with and without inhibition of nitric oxide synthase in porcine endotoxemia

The objective of this study was to determine the circuit and cardiac effects of norepinephrine (NE) with and without endotoxin, and how these responses are modified by the inhibition of nitric oxide synthase (NOS). We anesthetized eight pigs and instrumented them for measurements of cardiac output (Q), arterial pressure (Part), and mean pulmonary arterial pressure (Ppa). We also placed a 40-ml balloon in the right atrium for transient obstruction of flow and measurement of the mean circulatory filling pressure (MCFP) and resistance to venous return (RVR). After baseline measurements, animals were treated with 10 microg/kg/h of Escherichia coli endotoxin. At 105 min the measurements were repeated. We then infused 12.5 mg/kg of N(G)-nitro-L-arginine methyl ester (L-NAME) for 10 min and repeated the measurements. At baseline, at the end of endotoxin infusion, and after L-NAME infusion we infused 3, 9, and 27 microg/min of NE for 10 min each, and recorded hemodynamic measurements at each dose. NE shifted the venous return curve (i.e., increased MCFP) to the right without changing RVR, and increased cardiac output (CO) both at baseline and after endotoxin. Endotoxemia markedly flattened the dose-response curves for the change in Part, Ppa, CO, and heart rate with NE. The peak response of Part to NE after endotoxemia was restored with L-NAME, but the other dose-response curves were not affected. NE also did not shift the venous return curve after L-NAME. Furthermore, the increase in Part with NE was of shorter duration after L-NAME than in the baseline condition. In conclusion, NE shifts the venous return curve to the right and improves CO in endotoxic and nonendotoxic conditions. Endotoxemia decreases the arterial responsiveness to NE. L-NAME partly restored this loss of responsiveness in arteries but not in the venous circulation.

Impact of exogenous beta-adrenergic receptor stimulation on hepatosplanchnic oxygen kinetics and metabolic activity in septic shock

OBJECTIVE

To investigate the impact of exogenous beta-adrenergic receptor stimulation on splanchnic blood flow, oxygen kinetics, glucose-precursor flux, and liver metabolism in septic shock.

DESIGN

Prospective trial.

SETTING

University hospital intensive care unit.

PATIENTS

Six patients with hyperdynamic (cardiac index >4.0 L/min/m2) septic shock, all requiring norepinephrine to maintain blood pressure >65 mm Hg.

INTERVENTIONS

We compared norepinephrine and phenylephrine titrated to achieve similar systemic hemodynamics and gas exchange. Splanchnic hemodynamics, oxygen kinetics, and metabolic parameters were measured before, during, and after replacing norepinephrine with phenylephrine.

MEASUREMENTS AND MAIN RESULTS

Splanchnic blood flow and oxygen kinetics were derived from the steady-state indocyanine-green clearance based on hepatic dye extraction and arterial and hepatic venous blood gases. Endogenous glucose production rate was derived from the plasma appearance rate of stable-isotope-labeled glucose using a primed-constant infusion. Splanchnic lactate, alanine (high-performance liquid chromatography) uptake, and hepatic monoethylglycinexylidide (MEGX) (fluorescence polarization immunoassay) formation rates were calculated from splanchnic blood flow and arterial-hepatic venous concentration differences. Replacing norepinephrine with phenylephrine induced no change in systemic hemodynamics or gas exchange. While splanchnic oxygen consumption and alanine uptake rate remained unaffected, splanchnic blood flow, oxygen delivery, and lactate uptake rate were significantly decreased. Glucose production rate also decreased significantly. A return to norepinephrine restored splanchnic blood flow, oxygen delivery, and lactate uptake rate to baseline values, while glucose production rate remained depressed. Hepatic MEGX formation rate was not influenced during the investigation.

CONCLUSIONS

Exogenous beta-adrenergic receptor stimulation determines splanchnic blood flow, oxygen delivery, and glucose precursor flux but not splanchnic oxygen utilization in septic shock. Gluconeogenesis is not directly affiliated to hepatosplanchnic oxygen kinetics. The different response of glucose and MEGX production rates, metabolic pathways of the periportal and perivenous region, may document intrahepatic heterogeneity associated with hepatocellular metabolic compartmentation.

The effects of bronchodilators on spontaneous ventilation and oxygen consumption in rhesus monkeys

The effects of breathing normal saline, salmeterol, fenoterol, ipratropium bromide, or formoterol, and of i.v. infusion of theophylline on oxygen consumption (VO2), carbon dioxide production (VCO2), minute ventilation (VE), heart and respiratory rates, and end-tidal carbon dioxide tension (P(ET)CO2) have been defined in 10 anesthetized, intubated rhesus monkeys (mean age 7.0 y, weight 10.2 kg). VO2 increased over control by + 17.1% after salmeterol (p < 0.001), +33.3% after fenoterol (p < 0.001), +23.7% after formoterol (p < 0.001), +3.9% after theophylline (p < 0.01), but did not change after ipratropium bromide and normal saline. VE increased by 63.0% after fenoterol (p < 0.001), 49.8% after formoterol (p < 0.001), 31.7% after salmeterol (p < 0.01), and 29.7% after theophylline (p < 0.001), but not after ipratropium bromide or normal saline. Heart rate response was greatest after fenoterol, formoterol, and salmeterol, respectively. P(ET)CO2 dropped dramatically after theophylline (-15.7%, p < 0.001), but not at all with any of the inhaled beta2-adrenoceptor agonists. In seven animals, salbutamol (albuterol) caused an increase in V(E) and VO2 of 50.1% and 45.9%, respectively, whereas in the presence of a beta2-adrenoceptor antagonist [racemic or (+/-)-propranolol (0.1 mg/kg i.v.)], inhaled salbutamol (2.5 mg/mL for 10 min) could not increase V(E) (+6.2%, p > 0.05) and VO2 (+1.6%, p > 0.05). The increase in VO2 and V(E) after administration of beta2-agonists may be partly the result of direct stimulation of the respiratory center and partly a response to increased metabolic rate. The dramatic increase in VO2 and V(E) after salbutamol was suppressed in the presence of propranolol, which is consistent with a beta-receptor-mediated mechanism.