Epinephrine plasma metabolic clearance rates and physiologic thresholds for metabolic and hemodynamic actions in man

Catecholamine-induced hypertensive crises: current insights and management

Phaeochromocytomas and paragangliomas (PPGLs) release catecholamines leading to catecholamine-induced hypertensive (CIH) crises, with blood pressure greater than or equal to 180/120 mm Hg. CIH crises can be complicated by tachyarrhythmias, hypotension, or life-threatening target organ damage while treatment remains undefined, often requiring co-management between endocrinologists and cardiologists. Furthermore, biochemical diagnosis of a PPGL as a cause of a CIH crisis can be difficult to identify or confounded by comorbid conditions, potentially resulting in misdiagnosis. Here, we combine relevant evidence, 60 years of collective clinical experience, insights derived from assessing over 2600 patients with PPGL, and supplementary outcomes from 100 patients (treated at the National Institutes of Health) with a CIH crisis to inform diagnosis and treatment of CIH crises. Recognising that disparities exist between availability, cost, and familiarity of various agents, flexible approaches are delineated allowing for customisation, given institutional availability and provider preference. A CIH crisis and its complications are readily treatable with available drugs, with effective intervention defining an avenue for mitigating consequent morbidity and mortality in patients with PPGL.

Fast Acting, Dry Powder, Needle-Free, Intranasal Epinephrine Spray: A Promising Future Treatment for Anaphylaxis

BACKGROUND

Epinephrine intramuscular (IM) autoinjector is a life-saving drug for the emergency treatment of immediate-type allergic reactions (type I). Nevertheless, it is sometimes applied incorrectly or underused because of short shelf life, high costs, fear of use, or inconvenience of carrying. FMXIN002, a nasal powder spray of epinephrine, was developed as a needle-free alternative.

OBJECTIVE

To compare epinephrine pharmacokinetics, pharmacodynamics, and safety after the administration of the FMXIN002 nasal spray versus autoinjector.

METHODS

An open-label trial was performed in 12 adults with seasonal allergic rhinitis without asthma. Epinephrine pharmacokinetics, pharmacodynamics, and safety were compared between FMXIN002 (1.6 mg and 3.2 mg) administered intranasally with/without a nasal allergen challenge and IM (0.3 mg) EpiPen.

RESULTS

FMXIN002 3.2 mg, administered after a nasal allergen challenge, displayed a shorter Tmax than EpiPen (median: 2.5 minutes vs 9.0 minutes, statistically nonsignificant [NS]) and a significantly shorter time when the measured analyte concentration is 100 pg/mL during the absorption phase pg/mL (median: 1.0 minutes vs 3.0 minutes for FMXIN002, P < .02). Moreover, FMXIN002 3.2 mg administered after the challenge test has resulted in a doubling of the maximal measured plasma analyte concentration over the sampling period (1110 vs 551 pg/mL, NS); area under the curve from 0 to 8 hours was 56% higher (672 vs 431 hours pg/mL, compared with EpiPen, NS). Pharmacodynamic response was comparable at all treatments. FMXIN002 was well tolerated, and treatment-emergent adverse events (AEs) were mild, local, and resolved spontaneously. No AEs were reported after the administration of EpiPen in our study. FMXIN002 was stable for 2 years at room temperature conditions. However, variability in the pharmacokinetics (expressed in coefficient of variation) is high. Having a prior nasal allergen challenge results in a substantial increase and speed of absorption.

CONCLUSIONS

Intranasal absorption of dry powder epinephrine is faster than EpiPen offering a clinical advantage in the short therapeutic window for the treatment of anaphylaxis. The FMXIN002 product offers a needle-free, pocket-size, safe, user-friendly, and stable alternative to epinephrine autoinjectors.

A Narrative Review of Drug Therapy in Adult and Pediatric Cardiac Arrest

Drugs are used during cardiopulmonary resuscitation (CPR) in association with chest compressions and ventilation. The main purpose of drugs during resuscitation is either to improve coronary perfusion pressure and myocardial perfusion in order to achieve return of spontaneous circulation (ROSC). The aim of this up-to-date review is to provide an overview of the main drugs used during cardiac arrest (CA), highlighting their historical context, pharmacology, and the data to support them. Epinephrine remains the only recommended vasopressor. Regardless of the controversy about optimal dosage and interval between doses in recent papers, epinephrine should be administered as early as possible to be the most effective in non-shockable rhythms. Despite inconsistent survival outcomes, amiodarone and lidocaine are the only two recommended antiarrhythmics to treat shockable rhythms after defibrillation. Beta-blockers have also been recently evaluated as antiarrhythmic drugs and show promising results but further evaluation is needed. Calcium, sodium bicarbonate, and magnesium are still widely used during resuscitation but have shown no benefit. Available data may even suggest a harmful effect and they are no longer recommended during routine CPR. In experimental studies, sodium nitroprusside showed an increase in survival and favorable neurological outcome when combined with enhanced CPR, but as of today, no clinical data is available. Finally, we review drug administration in pediatric CA. Epinephrine is recommended in pediatric CA and, although they have not shown any improvement in survival or neurological outcome, antiarrhythmic drugs have a 2b recommendation in the current guidelines for shockable rhythms.

Pharmacokinetic and pharmacodynamic comparison of epinephrine, administered intranasally and intramuscularly: An integrated analysis

BACKGROUND

Manual intramuscular epinephrine injection is the standard of care for treating severe allergic reactions and anaphylaxis. Epinephrine autoinjectors were approved on the basis of the assumption that their pharmacokinetic and pharmacodynamic profiles are equivalent to manual intramuscular injection; however, although there is emerging evidence for product-related differences in pharmacokinetic profiles, very little is known about the comparative pharmacodynamic profiles.

OBJECTIVE

To compare pharmacokinetic and pharmacodynamic profiles of epinephrine delivered through manual intramuscular injection, autoinjectors, and intranasal spray.

METHODS

This integrated analysis was based on data from 4 randomized cross-over phase 1 trials that compared the pharmacokinetics and pharmacodynamics of epinephrine using manual intramuscular epinephrine 0.3 mg injection, epinephrine 0.3 mg autoinjectors (Symjepi and EpiPen), and epinephrine 1 mg intranasal spray (neffy).

RESULTS

Data from 175 participants showed that although neffy (1.0 mg intranasal spray) resulted in a maximum concentration (258 pg/mL) that was lower than or comparable with manual epinephrine intramuscular injection (254 pg/mL), Symjepi (438 pg/mL) and EpiPen (503 pg/mL), it led to comparable increases in systolic blood pressure (maximum effect [Emax], 16.9, 10.9, 14.9, and 18.1 mm Hg, respectively). The effect of neffy on diastolic blood pressure was also markedly more pronounced than that of other products (Emax, 9.32, 5.51, 5.78, and 5.93 mm Hg, respectively).

CONCLUSION

Intranasal delivery of epinephrine using neffy increases systolic blood pressure more efficiently than do manual intramuscular injection and epinephrine autoinjectors, despite lower maximum plasma concentrations.

Effects of Diet, Lifestyle, Chrononutrition and Alternative Dietary Interventions on Postprandial Glycemia and Insulin Resistance

As years progress, we are found more often in a postprandial than a postabsorptive state. Chrononutrition is an integral part of metabolism, pancreatic function, and hormone secretion. Eating most calories and carbohydrates at lunch time and early afternoon, avoiding late evening dinner, and keeping consistent number of daily meals and relative times of eating occasions seem to play a pivotal role for postprandial glycemia and insulin sensitivity. Sequence of meals and nutrients also play a significant role, as foods of low density such as vegetables, salads, or soups consumed first, followed by protein and then by starchy foods lead to ameliorated glycemic and insulin responses. There are several dietary schemes available, such as intermittent fasting regimes, which may improve glycemic and insulin responses. Weight loss is important for the treatment of insulin resistance, and it can be achieved by many approaches, such as low-fat, low-carbohydrate, Mediterranean-style diets, etc. Lifestyle interventions with small weight loss (7-10%), 150 min of weekly moderate intensity exercise and behavioral therapy approach can be highly effective in preventing and treating type 2 diabetes. Similarly, decreasing carbohydrates in meals also improves significantly glycemic and insulin responses, but the extent of this reduction should be individualized, patient-centered, and monitored. Alternative foods or ingredients, such as vinegar, yogurt, whey protein, peanuts and tree nuts should also be considered in ameliorating postprandial hyperglycemia and insulin resistance. This review aims to describe the available evidence about the effects of diet, chrononutrition, alternative dietary interventions and exercise on postprandial glycemia and insulin resistance.

CARDIOKIN1: Computational Assessment of Myocardial Metabolic Capability in Healthy Controls and Patients With Valve Diseases

Supplemental Digital Content is available in the text.

Background:

Many heart diseases can result in reduced pumping capacity of the heart muscle. A mismatch between ATP demand and ATP production of cardiomyocytes is one of the possible causes. Assessment of the relation between myocardial ATP production (MV_ATP) and cardiac workload is important for better understanding disease development and choice of nutritional or pharmacologic treatment strategies. Because there is no method for measuring MV_ATP in vivo, the use of physiology-based metabolic models in conjunction with protein abundance data is an attractive approach.

METHOD:

We developed a comprehensive kinetic model of cardiac energy metabolism (CARDIOKIN1) that recapitulates numerous experimental findings on cardiac metabolism obtained with isolated cardiomyocytes, perfused animal hearts, and in vivo studies with humans. We used the model to assess the energy status of the left ventricle of healthy participants and patients with aortic stenosis and mitral valve insufficiency. Maximal enzyme activities were individually scaled by means of protein abundances in left ventricle tissue samples. The energy status of the left ventricle was quantified by the ATP consumption at rest (MV_ATP[rest]), at maximal workload (MV_ATP[max]), and by the myocardial ATP production reserve, representing the span between MV_ATP(rest) and MV_ATP(max).

Results:

Compared with controls, in both groups of patients, MV_ATP(rest) was increased and MV_ATP(max) was decreased, resulting in a decreased myocardial ATP production reserve, although all patients had preserved ejection fraction. The variance of the energetic status was high, ranging from decreased to normal values. In both patient groups, the energetic status was tightly associated with mechanic energy demand. A decrease of MV_ATP(max) was associated with a decrease of the cardiac output, indicating that cardiac functionality and energetic performance of the ventricle are closely coupled.

Conclusions:

Our analysis suggests that the ATP-producing capacity of the left ventricle of patients with valvular dysfunction is generally diminished and correlates positively with mechanical energy demand and cardiac output. However, large differences exist in the energetic state of the myocardium even in patients with similar clinical or image-based markers of hypertrophy and pump function.

Registration:

URL: https://www.clinicaltrials.gov; Unique identifiers: NCT03172338 and NCT04068740.

Effects of changes in end-tidal carbon dioxide tension on oral tissue blood flow and tissue oxygen tension during remifentanil infusion in rabbits

PURPOSE

The aim of this study was to investigate the effects of end-tidal carbon dioxide tension (ETCO₂) changes during remifentanil infusion on mandibular bone marrow tissue blood flow (BBF), masseter muscle tissue blood flow (MBF), mandibular bone marrow tissue oxygen tension (PbO₂) and masseter muscle tissue oxygen tension (PmO₂) in rabbits.

METHODS

Ten male tracheotomized Japan White rabbits were anesthetized and ventilated with sevoflurane. ETCO₂ was adjusted to 30 mmHg. After baseline measurement, CO₂ was added to the inhaled air, and ETCO₂ was increased to 40 and 60 mmHg. Heart rate (HR), systolic blood pressure (SBP), diastolic blood pressure (DBP), mean arterial pressure (MAP), BBF, MBF, PbO₂, and PmO₂ were recorded with and without remifentanil infusion at 0.4 µg/kg/min.

RESULTS

Two-way repeated measures analysis of variance showed no interaction between ETCO₂ and remifentanil in all variables. Remifentanil infusion produced decreases in HR, SBP, MAP, BBF and MBF compared with those without remifentanil infusion, while it did not affect DBP, PbO₂ and PmO₂. Elevation of ETCO₂ from 30 to 60 mmHg produced decreases in HR and MBF, and increases in SBP, DBP, MAP and BBF, while it did not affect PbO₂ and PmO₂.

CONCLUSION

PbO₂ and PmO₂ remained unchanged despite changes in BBF and MBF during ETCO₂ change with or without remifentanil infusion.

Correlation Between Plasma Catecholamines, Weight, and Diabetes in Pheochromocytoma and Paraganglioma

CONTEXT

Pheochromocytomas and paragangliomas (PCC/PGL) are neuroendocrine tumors with discrete catecholamine profiles that cause incompletely understood metabolic and physiologic changes.

OBJECTIVE

The objective was to evaluate relationships between plasma catecholamines, body weight, and hemoglobin A1c (HbA1c). We hypothesized that individual catecholamines would correlate negatively with weight and glucose control.

DESIGN

A retrospective cohort study was performed (1999-2020). Wilcoxon rank-sum tests compared nonparametric, continuous variables; mixed-effect linear modeling (MEM) evaluated relationships between catecholamines and weight or HbA1c. The median study duration was 54.2 months [interquartile range (IQR) 19.0-95.1].

SETTING

Tertiary academic hospital.

PATIENTS

360 patients were identified prospectively by referral to our center for management or surveillance of PCC/PGL. The median age was 59 years (IQR 45-67) and 56.4% (n = 203) were female.

MAIN OUTCOME MEASURES

The primary and secondary outcomes were weight and HbA1c, respectively.

RESULTS

On multivariable MEM, norepinephrine (P < 0.0005) negatively correlated with weight when all catecholamines and their derivatives were tried in the model, and normetanephrine (P < 0.0005) correlated when only metanephrines were included. In the surgical cohort (n = 272), normetanephrine decreased postoperatively and was inversely associated with weight (P < 0.0005). Elevated norepinephrine or normetanephrine at the study termination, indicative of metastatic and/or recurrent disease (MRD), correlated with weight loss. Norepinephrine and normetanephrine (P < 0.0005) directly correlated with HbA1c.

CONCLUSION

Plasma norepinephrine and its metabolite directly correlate with HbA1c and inversely correlate with weight in PCC/PGL. After resection, declining normetanephrine levels correlate with improving HbA1c despite an increase in patient body weight. Persistently elevated catecholamines and decreasing weight are observed in MRD.

Pharmacokinetics of Single Dose Lidocaine and Epinephrine Following Iontophoresis of the Tympanic Membrane in a Double-Blinded Randomized Trial

OBJECTIVE

To evaluate local and systemic safety of bilateral iontophoretic administration of lidocaine with epinephrine or lidocaine alone to the tympanic membrane (TM).

STUDY DESIGN

A randomized, double-blind, two-arm study was conducted at a single center. Healthy adults were randomized to bilateral iontophoretic treatment with 2% lidocaine, 1:100,000 epinephrine, or 2% lidocaine (control). Otoscopy, cranial nerve examination, tympanometry, and audiometry safety evaluations were conducted before and 3-days post-procedure. Systemic safety was evaluated via analysis of vital signs taken before and up to 120 minutes post-iontophoresis, and blood samples collected before and up to 230 minutes post-iontophoresis.

RESULTS

Twenty-five subjects were treated with bilateral iontophoresis of either lidocaine and epinephrine (n = 15 subjects) or lidocaine alone (n = 10). Mean plasma epinephrine concentrations for both groups remained within the normal range for endogenous epinephrine. Mean plasma concentrations of lidocaine were not statistically different between groups, ranging from 0.245 to 2.28 ng/ml after administration of lidocaine with epinephrine (immediate post-iontophoresis to 230 min post-iontophoresis), compared with 1.35 to 2.14 ng/ml after administration of lidocaine alone. The presence of epinephrine slowed the systemic absorption of lidocaine. Lidocaine levels (Cmax 2.24 ng/ml) were approximately 2000-fold lower than the threshold for minor lidocaine toxicity. No device-, procedure- or drug-related adverse events were reported.

CONCLUSION

The local and systemic safety of bilateral iontophoretic delivery of 2% lidocaine, 1:100,000 epinephrine to the TM was demonstrated by low plasma levels of drug and absence of both serious and non-serious device-, procedure-, or drug-related adverse events.

The adrenal medulla in cardiovascular medicine: an untold story

Unlike noradrenaline, the sympathetic neurotransmitter which overflows to the circulation, adrenaline (ADR) is a secreted hormone, with a low plasma concentration, and plasma concentration for biological action a log order lower than that of noradrenaline. The venous drainage of the left adrenal medulla into the left renal vein does expose this vein to uniquely high plasma ADR concentrations and possible risk of thrombosis at high rates of ADR secretion. There is typically a different timeframe for adrenal medullary and sympathetic nervous system responses: ADR release is short term in contrast with sympathetic activation persisting for years in heart failure and hypertension. The historic view of Walter Cannon, subject to recent review, that the sympathoadrenal system is a unified biological system, was deconstructed further with demonstration of frequent mismatching of adrenal medullary and sympathetic nervous responses. Under gravity stimulation with standing, there is prompt sympathetic activation without ADR release. In many diseases, notably obesity, hypertension, heart failure and depressive illness, an activated sympathetic nervous system and silent adrenal medulla coexist. The therapeutic corollary of this is that ADR blockade is much less commonly needed clinically than pharmacological antagonism of the sympathetic nervous system.

Pharmacological Heart Failure Therapy in Children: Focus on Inotropic Support

Pediatric heart failure is a clinical syndrome, which needs to be distinctly defined and the pathophysiological consequences considered. Pharmacological treatment depends on the disease- and age-specific myocardial characteristics. Acute and chronic low cardiac output is the result of an inadequate heart rate (rhythm), myocardial contractility, preload and afterload, and also ventriculo-ventricular interaction, synchrony, atrio-ventricular and ventricular-arterial coupling. The treatment of choice is curing the cause of heart failure, if possible.Acute HF therapy is still based to the use of catecholamines and inodilators. The cornerstone of chronic HF treatment consists of blocking the endogenous, neuro-humoral axis, in particular the adrenergic and renin-angiotensin-aldosterone system.Before neprilysin inhibitors are used in young children, their potential side-effect for inducing Alzheimer disease needs to be clarified. The focus of the current review is put on the differential use of the inotropic drugs as epinephrine, norepinephrine, dopamine and dobutamine, and also the inodilators milrinone and levosimendan. Considering effects and side-effects of any cardiac stimulating treatment strategy, co-medication with ß-blockers, angiotensin converting inhibitors (ACEIs), angiotensin blockers (ARBs) and mineralocorticoid receptor antagonists (MRAs) is not a contradiction, but a senseful measure, even still during the acute inotropic treatment.Missing sophisticated clinical trials using accurate entry criteria and clinically relevant endpoints, there is especially in cardiovascular diagnosis and treatment of young children a compromise of evidence-based versus pathophysiology-based procedures. But based on the pharmacological and pathophysiological knowledge a hypothesis-driven individualized treatment is already currently possible and therefore indicated.

α2-Adrenergic Disruption of β Cell BDNF-TrkB Receptor Tyrosine Kinase Signaling

Adrenergic signaling is a well-known input into pancreatic islet function. Specifically, the insulin-secreting islet β cell expresses the Gi/o-linked α2-adrenergic receptor, which upon activation suppresses insulin secretion. The use of the adrenergic agonist epinephrine at micromolar doses may have supraphysiological effects. We found that pretreating β cells with micromolar concentrations of epinephrine differentially inhibited activation of receptor tyrosine kinases. We chose TrkB as an example because of its relative sensitivity to the effects of epinephrine and due to its potential regulatory role in the β cell. Our characterization of brain-derived neurotrophic factor (BDNF)-TrkB signaling in MIN6 β cells showed that TrkB is activated by BDNF as expected, leading to canonical TrkB autophosphorylation and subsequent downstream signaling, as well as chronic effects on β cell growth. Micromolar, but not nanomolar, concentrations of epinephrine blocked BDNF-induced TrkB autophosphorylation and downstream mitogen-activated protein kinase pathway activation, suggesting an inhibitory phenomenon at the receptor level. We determined epinephrine-mediated inhibition of TrkB activation to be Gi/o-dependent using pertussis toxin, arguing against an off-target effect of high-dose epinephrine. Published data suggested that inhibition of potassium channels or phosphoinositide-3-kinase signaling may abrogate the negative effects of epinephrine; however, these did not rescue TrkB signaling in our experiments. Taken together, these results show that (1) TrkB kinase signaling occurs in β cells and (2) use of epinephrine in studies of insulin secretion requires careful consideration of concentration-dependent effects. BDNF-TrkB signaling in β cells may underlie pro-survival or growth signaling and warrants further study.

Quantitative Assessment of Blood Lactate in Shock: Measure of Hypoxia or Beneficial Energy Source

Blood lactate concentration predicts mortality in critically ill patients and is clinically used in the diagnosis, grading of severity, and monitoring response to therapy of septic shock. This paper summarizes available quantitative data to provide the first comprehensive description and critique of the accepted concepts of the physiology of lactate in health and shock, with particular emphasis on the controversy of whether lactate release is simply a manifestation of tissue hypoxia versus a purposeful transfer ("shuttle") of lactate between tissues. Basic issues discussed include (1) effect of nonproductive lactate-pyruvate exchange that artifactually enhances flux measurements obtained with labeled lactate, (2) heterogeneous tissue oxygen partial pressure (Krogh model) and potential for unrecognized hypoxia that exists in all tissues, and (3) pathophysiology that distinguishes septic from other forms of shock. Our analysis suggests that due to exchange artifacts, the turnover rate of lactate and the lactate clearance are only about 60% of the values of 1.05 mmol/min/70 kg and 1.5 L/min/70 kg, respectively, determined from the standard tracer kinetics. Lactate turnover reflects lactate release primarily from muscle, gut, adipose, and erythrocytes and uptake by the liver and kidney, primarily for the purpose of energy production (TCA cycle) while the remainder is used for gluconeogenesis (Cori cycle). The well-studied physiology of exercise-induced hyperlactatemia demonstrates massive release from the contracting muscle accompanied by an increased lactate clearance that may occur in recovering nonexercising muscle as well as the liver. The very limited data on lactate kinetics in shock patients suggests that hyperlactatemia reflects both decreased clearance and increased production, possibly primarily in the gut. Our analysis of available data in health and shock suggests that the conventional concept of tissue hypoxia can account for most blood lactate findings and there is no need to implicate a purposeful production of lactate for export to other organs.

Counterregulatory responses to postprandial hypoglycemia after Roux-en-Y gastric bypass

BACKGROUND

Postbariatric hypoglycemia (PBH) is a potentially serious complication after Roux-en-Y gastric bypass (RYGB), and impaired counterregulatory hormone responses have been suggested to contribute to the condition.

OBJECTIVES

We evaluated counterregulatory responses during postprandial hypoglycemia in individuals with PBH who underwent RYGB.

SETTING

University hospital.

METHODS

Eleven women with documented PBH who had RYGB underwent a baseline liquid mixed meal test (MMT) followed by 5 MMTs preceded by treatment with (1) acarbose 50 mg, (2) sitagliptin 100 mg, (3) verapamil 120 mg, (4) liraglutide 1.2 mg, and (5) pasireotide 300 μg. Blood was collected at fixed time intervals. Plasma and serum were analyzed for glucose, insulin, glucagon, epinephrine, norepinephrine, pancreatic polypeptide (PP), and cortisol.

RESULTS

During the baseline MMT, participants had nadir blood glucose concentrations of 3.3 ± .2 mmol/L. At the time of nadir glucose, there was a small but significant increase in plasma glucagon. Plasma epinephrine concentrations were not increased at nadir glucose but were significantly elevated by the end of the MMT. There were no changes in norepinephrine, PP, and cortisol concentrations in response to hypoglycemia. After treatment with sitagliptin, 8 individuals had glucose nadirs <3.2 mmol/L (versus 4 individuals at baseline), and significant increases in glucagon, PP, and cortisol responses were observed.

CONCLUSIONS

In response to postprandial hypoglycemia, individuals with PBH who underwent RYGB only had minor increases in counterregulatory hormones, while larger hormone responses occurred when glucose levels were lowered during treatment with sitagliptin. The glycemic threshold for counterregulatory activation could be altered in individuals with PBH, possibly explained by recurrent hypoglycemia.

Pheochromocytoma With Adrenergic Biochemical Phenotype Shows Decreased GLP-1 Secretion and Impaired Glucose Tolerance

CONTEXT

Impaired glucose homeostasis is a common finding in pheochromocytoma (PHEO), especially with adrenergic phenotype. The possible contribution of incretin dysfunction to dysglycemia in PHEO patients has not been studied.

OBJECTIVE

To compare changes in pancreatic endocrine function and gut hormones' production during a liquid meal test before and 1 year after adrenalectomy.

METHODS

In a prospective study, we included 18 patients with PHEO (13 females) with adrenergic biochemical phenotype. A liquid meal test with predefined isocaloric enteral nutrition was performed to evaluate dynamic changes in pancreatic hormones and incretins.

RESULTS

During the meal test, insulin levels were significantly lower before adrenalectomy only in the early phase of insulin secretion, but changes in area under the curve (AUC) did not reach statistical significance (AUC = 0.07). Plasma glucagon (AUC < 0.01) and pancreatic polypeptide levels (AUC < 0.01) were suppressed in comparison with the postoperative state. Impaired response to the meal was found preoperatively for glucagon-like peptide-1 (GLP-1; AUC P < 0.05), but not glucose-dependent insulinotropic polypepide (GIP; AUC P = 0.21). No significant changes in insulin resistance indices were found, except for the homeostatic model assessment-beta index, an indicator of the function of islet β cells, which negatively correlated with plasma metanephrine (R = -0.66, P < 0.01).

CONCLUSIONS

Our study shows suppression of pancreatic α and β cell function and impaired GLP-1 secretion during a dynamic meal test in patients with PHEO, which is improved after its surgical treatment. These data demonstrate a novel and potentially significant interconnection between excessive catecholamine production and the secretion of glucoregulatory hormones.

Comparison of two vasoconstrictors on glycemic levels in diabetic patients

OBJECTIVES

The aim of this study was to evaluate glycemic levels in diabetic patients before, during, and after extractions using 2% lidocaine with 1:100,000 epinephrine (Lido/Epi) and 3% prilocaine with 0.03 IU/mL felypressin (Prilo/Fely).

MATERIALS AND METHODS

A double-blind, randomized clinical trial was conducted to evaluate changes in body parameters and glycemic levels in diabetic patients undergoing two anesthetic protocols during dental extractions. During surgery, we evaluated blood pressure (BP), heart rate (HR), saturation (SpO2), and capillary glycemic levels (Gly). These parameters were measured at the following surgical moments: basal, 30 min after medication, incision, tooth removal, suture, and 30 and 60 min after anesthesia.

RESULTS

Data analysis showed no differences between the groups considering age, weight, and time spent in surgery. Increased systolic BP and decreased diastolic BP were observed in the lido/epi group. No difference was observed in the prilo/fely group among the surgical moments or between the groups regarding BP. No difference was observed in HR and SpO2 between the groups at any surgical moment. However, differences were found when compared the differences in glycemic and basal levels in both groups with greater decreases in blood glucose values for the lido/epi group. In anxiety level evaluation, there was no difference between the different surgical moments.

CONCLUSION

Thus, both lido/epi and prilo/fely (maximum 3.6 mL) can be safely used in controlled diabetic patients CLINICAL RELEVANCE: The use of lidocaine associated with epinephrine did not increase glycemic levels but leads to decrease over time when associated with an anxiety reduction protocol, offering some advantage over prilocaine plus felypressin for diabetic patients.

Composite Pheochromocytoma Presenting as Severe Lactic Acidosis and Back Pain: A Case Report

Pheochromocytoma is a rare, catecholamine secreting tumor arising from chromaffin cells. Presentation of this tumor is highly variable, the most common being hypertension, tachycardia, sweating, and headache. Lactic acidosis and back pain are rare complications of this tumor. We report a 51-year-old gentleman with composite pheochromocytoma, which is rarer than pheochromocytoma, presenting as severe back pain and lactic acidosis.

Nutrition delivery, workload and performance in a model-based ICU glycaemic control system

BACKGROUND AND OBJECTIVE

Hyperglycaemia is commonplace in the adult intensive care unit (ICU), and has been associated with increased morbidity and mortality. Effective glycaemic control (GC) can reduce morbidity and mortality, but has proven difficult. STAR is a model-based GC protocol that uniquely maintains normoglycaemia by changing both insulin and nutrition interventions, and has been proven effective in controlling blood glucose (BG) in the ICU. However, most ICU GC protocols only change insulin interventions, making the variable nutrition aspect of STAR less clinically desirable. This paper compares the performance of STAR modulating only insulin, with three simpler alternative nutrition protocols in clinically evaluated virtual trials.

METHODS

Alternative nutrition protocols are fixed nutrition rate (100% caloric goal), CB (Cahill et al. best) stepped nutrition rate (60%, 80% and 100% caloric goal for the first 3 days of GC, and 100% thereafter) and SLQ (STAR lower quartile) stepped nutrition rate (65%, 75% and 85% caloric goal for the first 3 days of GC, and 85% thereafter). Each nutrition protocol is simulated with the STAR insulin protocol on a 221 patient virtual cohort, and GC performance, safety and total intervention workload are assessed.

RESULTS

All alternative nutrition protocols considerably reduced total intervention workload (14.6-19.8%) due to reduced numbers of nutrition changes. However, only the stepped nutrition protocols achieved similar GC performance to the current variable nutrition protocol. Of the two stepped nutrition protocols, the SLQ nutrition protocol also improved GC safety, almost halving the number of severe hypoglycaemic cases (5 vs. 9, P = 0.42).

CONCLUSIONS

Overall, the SLQ nutrition protocol was the best alternative to the current variable nutrition protocol, but either stepped nutrition protocol could be adapted by STAR to reduce workload and make it more clinically acceptable, while maintaining its proven performance and safety.

Developmental venous anomalies and brainstem cavernous malformations: a proposed physiological mechanism for haemorrhage

The incidental diagnosis of both developmental venous anomalies (DVAs) and cavernous malformations (CMs) in the central nervous system is increasing with improved imaging techniques. While classically silent diseases, these cerebrovascular pathologies can follow an aggressive course, particularly when present in the brainstem. In the last decade, substantial research has focussed on KRIT1-mediated tight junction gene expression and their role in CM development. However, our understanding of the physiologic conditions precipitating symptomatic CM development or CM haemorrhage with and without concomitant DVAs, remains lacking. The only established risk factor for CM haemorrhage is a previous history of haemorrhage, and literature currently reports trauma as the only precipitant for symptomatic events. While plausible, this occurs in a minority, with many patients experiencing occult events. This manuscript presents a hypothesis for symptomatic CM events by first discussing the anatomical pathways for intracranial venous outflow via the internal jugular veins (IJV) and vertebral venous plexus (VVP), then exploring the role of venous flow diversion away from the IJVs under physiologic stress during dynamic postural shift. The resultant increase in intracranial venous pressure can exacerbate normal and pre-existing structural DVA pathologies, with repeated exposure causing symptomatic or CM-inducing events. This pathophysiological model is considered in the context of the role of the autonomic nervous system (ANS) in postural intracranial venous outflow diversion, and how this may increase the risk of DVA or CM events. It is hoped that this hypothesis invokes further investigation into precipitants for DVA or CM events and their sequela and, also, furthers the current knowledge on pathophysiological development of DVAs and CMs.

Exercise performance after salbutamol inhalation in non-asthmatic, non-athlete individuals: a randomised, controlled, cross-over trial

Background

Asthma is a frequent diagnosis in competitive sports, and inhaled β₂-agonists are commonly used by athletes. Although inhaled β₂-agonists do not seem to improve performance in athletes, it has remained uncertain whether they can increase exercise performance in non-athletes.

Objective

To investigate the effect of inhaled β₂-agonists on exercise performance in healthy non-athlete individuals.

Methods

In a double-blinded, placebo-controlled, cross-over trial, healthy, non-asthmatic, non-athlete individuals were randomised to inhalation of either 900 µg of salbutamol or placebo. Cardiopulmonary exercise testing, dynamic spirometry and impulse oscillometry were performed. The primary outcome was the effect from salbutamol on peak oxygen uptake, whereas secondary outcomes were breathing reserve and ventilation efficiency, and workload, heart rate, breath rate and minute ventilation at peak exercise under influence of salbutamol.

Results

A total of 36 healthy subjects with a mean age of 26±5 years were included. Salbutamol had no effect on peak oxygen uptake compared with placebo, 46.8±1.3 mL/kg/min versus 46.6±1.2 mL/kg/min, p=0.64. Salbutamol had no effect on workload, p=0.20, heart rate, p=0.23, breath rate, p=0.10, or minute ventilation, p=0.26, at peak exercise compared with placebo. Salbutamol lowered oxygen uptake, p=0.04, and workload, p=0.04, at anaerobic threshold compared with placebo. Forced expiratory volume in 1 s, 116%±13% of predicted, and peak expiratory flow, 122%±16% of predicted, increased after inhalation of salbutamol compared with placebo; 109%±13% and 117%±17%, respectively, p<0.01. Breathing reserve was found to be higher, 22%±2%, after salbutamol inhalation than after placebo, 16%±2%, p<0.01.

Conclusion

Inhaled salbutamol did not improve peak oxygen uptake in healthy, non-asthmatic, non-athlete individuals compared with placebo.

Trial registration number

NCT02914652.

Nutrition delivery of a model-based ICU glycaemic control system

BACKGROUND

Hyperglycaemia is commonplace in the adult intensive care unit (ICU), associated with increased morbidity and mortality. Effective glycaemic control (GC) can reduce morbidity and mortality, but has proven difficult. STAR is a proven, effective model-based ICU GC protocol that uniquely maintains normo-glycaemia by changing both insulin and nutrition interventions to maximise nutrition in the context of GC in the 4.4-8.0 mmol/L range. Hence, the level of nutrition it provides is a time-varying estimate of the patient-specific ability to take up glucose.

METHODS

First, the clinical provision of nutrition by STAR in Christchurch Hospital, New Zealand (N = 221 Patients) is evaluated versus other ICUs, based on the Cahill et al. survey of 158 ICUs. Second, the inter- and intra- patient variation of nutrition delivery with STAR is analysed. Nutrition rates are in terms of percentage of caloric goal achieved.

RESULTS

Mean nutrition rates clinically achieved by STAR were significantly higher than the mean and best ICU surveyed, for the first 3 days of ICU stay. There was large inter-patient variation in nutrition rates achieved per day, which reduced overtime as patient-specific metabolic state stabilised. Median intra-patient variation was 12.9%; however, the interquartile range of the mean per-patient nutrition rates achieved was 74.3-98.2%, suggesting patients do not deviate much from their mean patient-specific nutrition rate. Thus, the ability to tolerate glucose intake varies significantly between, rather than within, patients.

CONCLUSIONS

Overall, STAR's protocol-driven changes in nutrition rate provide higher nutrition rates to hyperglycaemic patients than those of 158 ICUs from 20 countries. There is significant inter-patient variability between patients to tolerate and uptake glucose, where intra-patient variability over stay is much lower. Thus, a best nutrition rate is likely patient specific for patients requiring GC. More importantly, these overall outcomes show high nutrition delivery and safe, effective GC are not exclusive and that restricting nutrition for GC does not limit overall nutritional intake compared to other ICUs.

Lactate metabolism: historical context, prior misinterpretations, and current understanding

Lactate (La^-) has long been at the center of controversy in research, clinical, and athletic settings. Since its discovery in 1780, La^- has often been erroneously viewed as simply a hypoxic waste product with multiple deleterious effects. Not until the 1980s, with the introduction of the cell-to-cell lactate shuttle did a paradigm shift in our understanding of the role of La^- in metabolism begin. The evidence for La^- as a major player in the coordination of whole-body metabolism has since grown rapidly. La^- is a readily combusted fuel that is shuttled throughout the body, and it is a potent signal for angiogenesis irrespective of oxygen tension. Despite this, many fundamental discoveries about La^- are still working their way into mainstream research, clinical care, and practice. The purpose of this review is to synthesize current understanding of La^- metabolism via an appraisal of its robust experimental history, particularly in exercise physiology. That La^- production increases during dysoxia is beyond debate, but this condition is the exception rather than the rule. Fluctuations in blood [La^-] in health and disease are not typically due to low oxygen tension, a principle first demonstrated with exercise and now understood to varying degrees across disciplines. From its role in coordinating whole-body metabolism as a fuel to its role as a signaling molecule in tumors, the study of La^- metabolism continues to expand and holds potential for multiple clinical applications. This review highlights La^-'s central role in metabolism and amplifies our understanding of past research.

THE EFFECT OF SALBUTAMOL ON PGC-1 α AND GLUT4 mRNA EXPRESSION IN THE LIVER AND MUSCLE OF ELDERLY DIABETIC MICE

Background

Peroxisome proliferator-activated receptor gamma coactivator 1-alpha (PGC-1α) plays an important role in the regulation of cellular energy metabolism, and it is involved in obesity and type 2 diabetes mellitus (T2DM). Its expression is elevated in the liver of T2DM mouse models. Literature reports show that chronic β2 stimulation improved insulin sensitivity in T2DM.

Objectives

We aimed to test the hypotheses that chronic β2 stimulation-induced improvement in insulin sensitivity involves changes in the expression of PGC-1α and glucose transporter 4 (GLUT4).

Animals and Methods

We fed a locally inbred, 8 months old mice, a high fat diet (HFD) to induce diabetes. These mice gained weight and became insulin resistant. The β2 agonist salbutamol had a beneficial effect on both glucose tolerance and insulin sensitivity after 4 weeks.

Results

Salbutamol beneficial effect persisted after 4 weeks of its discontinuation. HFD caused an up regulation of the hepatic PGC-1 α expression by 5.23 folds (P< 0.041) and salbutamol reversed this effect and caused a down regulation by 30.3 folds (P< 0.0001). PGC-1 α and GLUT4 expression in the muscle was not affected by salbutamol (P> 0.05).

Conclusion

Down regulation of the liver's PGC-1 α contributes to the beneficial effect of the chronic β2 stimulation on glucose tolerance and insulin sensitivity in T2DM mice.

Strategies for Reducing Fatal Complications in Liposuction

BACKGROUND

Liposuction has become one of the most common cosmetic surgical procedures, and severe complications secondary to this procedure have also increased significantly. That is why we carry out a research work to know the most frequent severe complications reported in the scientific literature to indicate criteria for prevention.

METHODS

English-language scientific publications about liposuction and its complications were analyzed using the PubMed.gov, from the beginning of PubMed's history through June 10, 2017. Five terms were used to define liposuction and its complications: "liposuction," "liposuction AND complications," liposuction AND major complications," "liposuction AND complications AND death," and "liposuction AND death." The quantities of results for the 5 phrases were analyzed, along with their contents.

RESULTS

One thousand sixty-three results were obtained from 1973 through June 10, 2017 for the phrase "Liposuction and Complications" in humans; for "Liposuction and Major Complications," 153 articles were found; for "Liposuction and Deaths," 89 articles were found; and 42 articles were obtained with the terms "Liposuction and Major Complications and Deaths." After final depuration, all those that were not specific to severe liposuction complications were eliminated, leaving a total of 39 articles that were included in our study. Five problems proved to be the most serious complications when performing liposuction: Thromboembolic disease, fat embolism, pulmonary edema, lidocaine intoxication, and intraabdominal visceral lesion.

CONCLUSIONS

The 5 most important complications that can cause death in liposuction are easily preventable using simple measures and proper safety protocols that are described in this work.

Brain-heart interactions: physiology and clinical implications

The brain controls the heart directly through the sympathetic and parasympathetic branches of the autonomic nervous system, which consists of multi-synaptic pathways from myocardial cells back to peripheral ganglionic neurons and further to central preganglionic and premotor neurons. Cardiac function can be profoundly altered by the reflex activation of cardiac autonomic nerves in response to inputs from baro-, chemo-, nasopharyngeal and other receptors as well as by central autonomic commands, including those associated with stress, physical activity, arousal and sleep. In the clinical setting, slowly progressive autonomic failure frequently results from neurodegenerative disorders, whereas autonomic hyperactivity may result from vascular, inflammatory or traumatic lesions of the autonomic nervous system, adverse effects of drugs and chronic neurological disorders. Both acute and chronic manifestations of an imbalanced brain-heart interaction have a negative impact on health. Simple, widely available and reliable cardiovascular markers of the sympathetic tone and of the sympathetic-parasympathetic balance are lacking. A deeper understanding of the connections between autonomic cardiac control and brain dynamics through advanced signal and neuroimage processing may lead to invaluable tools for the early detection and treatment of pathological changes in the brain-heart interaction.

Vasopressor requirement during targeted temperature management for out-of-hospital cardiac arrest caused by acute myocardial infarction without cardiogenic shock

Objective

We investigated whether patients with out-of-hospital cardiac arrest (OHCA) due to an acute myocardial infarction without cardiogenic shock required higher doses of vasopressors with low targeted temperature management (TTM) after return of spontaneous circulation.

Methods

We included consecutive comatose patients resuscitated from OHCA between January 2011 and December 2013. Patients with return of spontaneous circulation, regional wall motion abnormality on echocardiography, and coronary artery stenosis of ≥70% on percutaneous coronary artery angiography were enrolled. These patients received 36°C TTM or 33°C TTM following approval of TTM by patients’ next-of-kin (36°C and 33°C TTM groups, respectively). The cumulative vasopressor index was compared between groups.

Results

During induction phase, dose of vasopressors did not differ between groups. In the maintenance phase, the norepinephrine dose was 0.37±0.57 and 0.26±0.91 µg·kg^-1·min^-1 in the 33°C and 36°C TTM groups, respectively (P<0.01). During the rewarming phase, the norepinephrine and dopamine doses were 0.49±0.60 and 9.67±9.60 mcg·kg^-1·min^-1 in the 33°C TTM group and 0.14±0.46 and 3.13±7.19 mcg·kg^-1·min^-1 in the 36°C TTM group, respectively (P<0.01). The median cumulative vasopressor index was 8 (interquartile range, 3 to 8) and 4 (interquartile range, 0 to 8) in the 33°C and 36°C TTM groups, respectively (P=0.03).

Conclusion

In this study, patients with OHCA due to acute myocardial infarction without cardiogenic shock had an elevated vasopressor requirement with 33°C TTM compared to 36°C TTM during the maintenance and rewarming phases.

Opioid Facilitation of β-Adrenergic Blockade: A New Pharmacological Condition?

Recently, propranolol was suggested to prevent hyperlactatemia in a child with hypovolemic shock through β-adrenergic blockade. Though it is a known inhibitor of glycolysis, propranolol, outside this observation, has never been reported to fully protect against lactate overproduction. On the other hand, literature evidence exists for a cross-talk between β-adrenergic receptors (protein targets of propranolol) and δ-opioid receptor. In this literature context, it is hypothesized here that anti-diarrheic racecadotril (a pro-drug of thiorphan, an inhibitor of enkephalinases), which, in the cited observation, was co-administered with propranolol, might have facilitated the β-blocker-driven inhibition of glycolysis and resulting lactate production. The opioid-facilitated β-adrenergic blockade would be essentially additivity or even synergism putatively existing between antagonism of β-adrenergic receptors and agonism of δ-opioid receptor in lowering cellular cAMP and dependent functions.

Plasma free metanephrine, normetanephrine, and 3-methoxytyramine for the diagnosis of pheochromocytoma/paraganglioma

BACKGROUND

Pheochromocytomas (PHEO) and paragangliomas (PGL) are derived from paraganglia of the sympathetic and parasympathetic nervous system. Most of the sympathetic PHEO/PGL secrete either catecholamine or their metabolites, metanephrines, whereas parasympathetic PHEO/PGL are nonsecretory. We assessed the utility of plasma free 3-methoxytyramine (3MT), normetanephrine (NM), and metanephrine (MN) for the diagnosis of PHEO/PGL.

MATERIALS AND METHODS

Sixty-five patients referred to endocrine/ENT clinics were enrolled. Twelve patients with von Hippel-Lindau (VHL), neurofibromatosis type 1 (NF1) and multiple endocrine neoplasia type 2 (MEN2) syndromes were excluded. Remaining 53 patients (39 patients with adrenal, abdominal, cervical and thoracic PHEO/PGL and 14 patients with head and neck PGL (HNPGL) were taken for this study. Sixty-five age- and sex-matched subjects were taken as controls. Plasma levels 3MT, NM, and MN were measured using high-performance liquid chromatography. Receivers operating characteristics was plotted and cut-off levels were established.

RESULTS

When compared with controls, there was a 36-, 8.7- and 9.5-fold increase in levels of NM, 3MT and MN in the patients with PHEO/PGL and 7.2- and 2.7-fold increase in 3MT and NM, in the patients with HNPGL, respectively. In malignant PHEO/PGL, there was a 99-, 16- and 20-fold increase and in benign PHEO/PGL, there was 19-, 6.8- and 6.4-fold increase in levels of NM, 3MT, and MN, respectively. NM in combination with MN was high in 97% of the patients with PHEO/PGL. All three metabolites in combination were high in 83% of patients with HNPGL. In malignant PHEO/PGL, 50% subjects had increased levels of both NM and 3MT.

CONCLUSIONS

Measurement of plasma-free NM along with 3MT and MN provides a better tool for the diagnosis of PHEO/PGL as well as HNPGL. Further, NM in combination with 3MT can be used for the diagnosis of malignant PHEO/PGL.

Population pharmacokinetic and pharmacodynamic modeling of epinephrine administered using a mobile inhaler

Inhaled epinephrine is a potential alternative to self-administered intramuscular epinephrine in imminent anaphylactic reactions. The objective was to develop a pharmacokinetic-pharmacodynamic model describing exposure and effects on heart rate of inhaled epinephrine. Data from a 4-phase cross-over clinical trial in 9 healthy volunteers including 0.3 mg intramuscular epinephrine, two doses of inhaled epinephrine (4 mg/mL solution administered during [mean] 18 and 25 min, respectively) using a mobile pocket inhaler, and an inhaled placebo were analyzed using mixed-effects modeling. Inhaled epinephrine was available almost immediately and more rapidly than via the intramuscular route (absorption half-live 29 min). Epinephrine plasma concentrations declined rapidly after terminating inhalation (elimination half-life 4.1 min) offering the option to stop exposure in case of adverse events. While the expected maximum concentration was higher for inhaled epinephrine, this was not associated with safety concerns due to only moderate additional hemodynamic effects compared to intramuscular administration. Bioavailability after inhalation (4.7%) was subject to high interindividual and interoccasional variability highlighting that training of inhalation would be essential for patients. The proposed model suggests that the use of a highly concentrated epinephrine solution via inhalation may offer an effective treatment option in anaphylaxis, while efficacy in patients remains to be shown.

Exercise and the Regulation of Adipose Tissue Metabolism

Adipose tissue is a major regulator of metabolism in health and disease. The prominent roles of adipose tissue are to sequester fatty acids in times of energy excess and to release fatty acids via the process of lipolysis during times of high-energy demand, such as exercise. The fatty acids released during lipolysis are utilized by skeletal muscle to produce adenosine triphosphate to prevent fatigue during prolonged exercise. Lipolysis is controlled by a complex interplay between neuro-humoral regulators, intracellular signaling networks, phosphorylation events involving protein kinase A, translocation of proteins within the cell, and protein-protein interactions. Herein, we describe in detail the cellular and molecular regulation of lipolysis and how these processes are altered by acute exercise. We also explore the processes that underpin adipocyte adaptation to endurance exercise training, with particular focus on epigenetic modifications, control by microRNAs and mitochondrial adaptations. Finally, we examine recent literature describing how exercise might influence the conversion of traditional white adipose tissue to high energy-consuming "brown-like" adipocytes and the implications that this has on whole-body energy balance.

The value of adrenaline in the induction of supraventricular tachycardia in the electrophysiological laboratory

AIMS

The most commonly used drug for the facilitation of supraventricular tachycardia (SVT) induction in the electrophysiological (EP) laboratory is isoprenaline. Despite isoprenaline's apparent indispensability, availability has been problematic in some European countries. Alternative sympatomimethic drugs such as adrenaline have therefore been tried. However, no studies have determined the sensitivity and specificity of adrenaline for the induction of SVT. The objective of this study was to determine the sensitivity and specificity of adrenaline for the induction of SVT.

METHODS AND RESULTS

Between February 2010 and July 2013, 336 patients underwent an EP study for prior documented SVT. In 66 patients, adrenaline was infused because tachycardia was not induced under basal conditions. This group was compared with 30 control subjects with no history of SVT. Programmed atrial stimulation was carried out during baseline state and repeated after an infusion of adrenaline (dose ranging from 0.05 mcg/kgc to 0.3 mcg/kgc). The endpoint was the induction of SVT. Among 66 patients with a history of SVT but no induction under basal conditions, adrenaline facilitated induction in 54 patients (82%, P < 0.001). Among the 30 control subjects, SVT was not induced in any patient (0%) after infusion. Adrenaline was generally well tolerated, except for two patients (3.0%), where it had to be discontinued due to headache and high blood pressure or lumbar pain.

CONCLUSION

Adrenaline infusion has a high sensitivity (82%) and specificity (100%) for the induction of SVT in patients with prior documented SVT. Therefore, it could serve as an acceptable alternative to isoprenaline, when the latter is not available.

Effect of β2-adrenergic receptor polymorphisms on epinephrine and exercise-stimulated lipolysis in humans

The β₂‐adrenergic system is an important regulator of human adipose tissue lipolysis. Polymorphisms that result in amino acid substitutions in the β₂‐adrenergic receptor have been reported to alter lipolysis. We hypothesized that variations in the amino acid at position 16 of the β₂‐adrenergic receptor would result in different lipolytic responses to intravenous epinephrine and exercise. 17 volunteers homozygous for glycine at position 16 (Gly/Gly, nine female) and 16 volunteers homozygous for arginine at position 16 (Arg/Arg, eight female) of the β₂‐adrenergic receptor participated in this study. On one study day participants received infusions of epinephrine at submaximal (5 ng kg⁻¹ min⁻¹) and maximal (40 ng kg⁻¹ min⁻¹) lipolytic doses. The other study day volunteers bicycled for 90 min at 50–60% of maximum oxygen consumption (VO₂max). [9,10‐³H] Palmitate was infused both days to measure free fatty acid – palmitate kinetics. Oxygen consumption was measured using indirect calorimetry. Palmitate release rates in response to epinephrine and exercise were not different in the Gly/Gly and Arg/Arg participants. The only statistically significant difference we observed was a lesser ΔVO₂ in Arg/Arg volunteers in response to the submaximal epinephrine infusion. The polymorphisms resulting in Arg/Arg and Gly/Gly at position 16 of the β₂‐adrenergic receptor do not result in clinically meaningful differences in lipolysis responses to epinephrine or submaximal exercise.

e12017

Some studies suggest the polymorphism in the β₂‐adrenergic receptor have effects on fatty acid mobilization from adipose tissue. We measure lipolysis using tracer kinetics in volunteers selected for different genotypes at position 16 of the β₂‐adrenergic receptor. We found that polymorphisms resulting in Arg/Arg and Gly/Gly at position 16 of the β₂‐adrenergic receptor do not result in clinically meaningful differences in lipolysis responses to epinephrine or submaximal exercise.

Pharmacokinetics, hemodynamic and metabolic effects of epinephrine to prevent post-operative low cardiac output syndrome in children

Introduction

The response to exogenous epinephrine (Ep) is difficult to predict given the multitude of factors involved such as broad pharmacokinetic and pharmacodynamic between-subject variabilities, which may be more pronounced in children. We investigated the pharmacokinetics and pharmacodynamics of Ep, co-administered with milrinone, in children who underwent open heart surgical repair for congenital defects following cardiopulmonary bypass, including associated variability factors.

Methods

Thirty-nine children with a high risk of low cardiac output syndrome were prospectively enrolled. Ep pharmacokinetics, hemodynamic and metabolic effects were analyzed using the non-linear mixed effects modeling software MONOLIX. According to the final model, an Ep dosing simulation was suggested.

Results

Ep dosing infusions ranged from 0.01 to 0.23 μg.kg^-1.min^-1 in children whose weight ranged from 2.5 to 58 kg. A one-compartment open model with linear elimination adequately described the Ep concentration-time courses. Bodyweight (BW) was the main covariate influencing clearance (CL) and endogenous Ep production rate (q0) via an allometric relationship: CL(BWi) = θ_CL x (BWi)^3/4 and q0(BWi) = θ_q0 x (BWi )^3/4. The increase in heart rate (HR) and mean arterial pressure (MAP) as a function of Ep concentration were well described using an Emax model. The effect of age was significant on HR and MAP basal level parameters. Assuming that Ep stimulated the production rate of plasma glucose, the increases in plasma glucose and lactate levels were well described by turnover models without any significant effect of age, BW or exogenous glucose supply.

Conclusions

According to this population analysis, the developmental effects of BW and age explained a part of the pharmacokinetic and pharmacodynamics between-subject variabilities of Ep administration in critically ill children. This approach ultimately leads to a valuable Ep dosing simulation which should help clinicians to determine an appropriate a priori dosing regimen.

Characterizing vasopressin and other vasoactive mediators released during resuscitation of trauma patients

BACKGROUND

We sought to perform the first characterization of vasopressin and other vasoactive mediators released during resuscitation of hypotensive trauma patients.

METHODS

This institutional review board-approved study was conducted under waiver of consent. Adults with clinical evidence of acute traumatic injury and systolic blood pressure less than or equal to 90 mm Hg within 1 hour of arrival were evaluated at our Level I trauma center. Two hundred three patients were screened with 50 enrolled from February 2010 to February 2011. Demographic information was also collected. Blood samples were obtained at 0, 30, 60, 90, 120, and 240 minutes after arrival, and assays were performed for vasopressin, angiotensin II, epinephrine, and cortisol. We assessed the significance of variation in these vasoactive mediators with injury and transfusion of more than 600 mL, with adjustment for time using repeated-measures linear models in log units.

RESULTS

We found that vasopressin (p = 0.005) and epinephrine (p = 0.01) increased significantly with injury, while angiotensin (p = 0.60) and cortisol (p = 0.46) did not and that vasopressin (p < 0.001) and epinephrine (p = 0.004) increased significantly in patients requiring transfusion of more than 600 mL but angiotensin II (p = 0.11) and cortisol (p = 0.90) did not. Relatively low levels of vasopressin (<30 pg/mL) were observed at least once during the first 2 hours in 88% of trauma patients, and abnormally low epinephrine levels (<100 pg/mL) were observed at least once during the first 2 hours in 18% of trauma patients.

CONCLUSION

This is the first clinical trial to serially evaluate vasopressin and other vasoactive mediators following trauma during the resuscitation phase. Vasopressin, in particular, and epinephrine seem to be the key mediators produced in the human response to severe injury. A deficiency of vasopressin may contribute to intractable shock after trauma.

LEVEL OF EVIDENCE

Prognostic/epidemiologic study, level III.

High concentrations of drug in target tissues following local controlled release are utilized for both drug distribution and biologic effect: an example with epicardial inotropic drug delivery

Local drug delivery preferentially loads target tissues with a concentration gradient from the surface or point of release that tapers down to more distant sites. Drug that diffuses down this gradient must be in unbound form, but such drug can only elicit a biologic effect through receptor interactions. Drug excess loads tissues, increasing gradients and driving penetration, but with limited added biological response. We examined the hypothesis that local application reduces dramatically systemic circulating drug levels but leads to significantly higher tissue drug concentration than might be needed with systemic infusion in a rat model of local epicardial inotropic therapy. Epinephrine was infused systemically or released locally to the anterior wall of the heart using a novel polymeric platform that provides steady, sustained release over a range of precise doses. Epinephrine tissue concentration, upregulation of cAMP, and global left ventricular response were measured at equivalent doses and at doses equally effective in raising indices of contractility. The contractile stimulation by epinephrine was linked to drug tissue levels and commensurate cAMP upregulation for IV systemic infusion, but not with local epicardial delivery. Though cAMP was a powerful predictor of contractility with local application, tissue epinephrine levels were high and variable--only a small fraction of the deposited epinephrine was utilized in second messenger signaling and biologic effect. The remainder of deposited drug was likely used in diffusive transport and distribution. Systemic side effects were far more profound with IV infusion which, though it increased contractility, also induced tachycardia and loss of systemic vascular resistance, which were not seen with local application. Local epicardial inotropic delivery illustrates then a paradigm of how target tissues differentially handle and utilize drug compared to systemic infusion.

Large-dose epinephrine reduces skeletal muscle blood flow under general anesthesia in rabbits

The goal of this study was to investigate the effect of an epinephrine continuous infusion on muscle blood flow in rabbits. Sixteen male Japan White rabbits were randomly allocated to 1 of 2 groups: epinephrine continuous infusion at 0.01 μg/kg/min (Ep-0.01 group, n = 8) and at 0.1 μg/kg/ min (Ep-0.1 group, n = 8). The observed variables were heart rate, femoral artery blood pressure, common carotid artery blood flow (CCBF), masseter muscle blood flow (MBF), and quadriceps muscle blood flow (QBF). In the Ep-0.01 group, CCBF, MBF, and QBF were increased by 14, 22, and 21% from respective control values. In contrast, in the Ep-0.1 group, CCBF, MBF and QBF were decreased by 10, 30, and 27% from respective control values. There were no differences in the percentage change between MBF and QBF during epinephrine continuous infusion. Positive correlations were observed between CCBF and MBF and between CCBF and QBF. In conclusion, skeletal muscle blood flow was increased during the small-dose epinephrine infusion, whereas it was decreased during large-dose infusion.

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.

Oral mucosal injection of a local anesthetic solution containing epinephrine enhances muscle relaxant effects of rocuronium

The purpose of this study was to examine how submucosal injection of a clinically relevant dose of a lidocaine hydrochloride solution containing epinephrine affects the muscle relaxant effects of rocuronium bromide. Sixteen patients scheduled for orthognathic surgery participated in this study. All patients were induced with fentanyl citrate, a target-controlled infusion of propofol and rocuronium bromide. Anesthesia was maintained by total intravenous anesthesia. After nasotracheal intubation, an infusion of rocuronium bromide was started at 7 µg/kg/min, and the infusion rate was then adjusted to maintain a train of four (TOF) ratio at 10 to 15%. The TOF ratio just prior to oral mucosal injection of a 1% lidocaine hydrochloride solution containing 10 µg/mL epinephrine (LE) was taken as the baseline. TOF ratio was observed for 20 minutes, with 1-minute intervals following the start of injection. Mean epinephrine dose was 85.6 ± 18.6 µg and mean infusion rate of rocuronium bromide was 6.3 ± 1.6 µg/kg/min. TOF ratio began to decrease 2 minutes after the injection of LE, reached the minimum value at 3.1 ± 3.6% 12 minutes after the injection, and then began to recover. We conclude that oral mucosal injection of LE enhances the muscle relaxant effects of rocuronium bromide.

Chronic β2 adrenergic agonist, but not exercise, improves glucose handling in older type 2 diabetic mice

Insulin resistant type 2 diabetes mellitus in the obese elderly has become a worldwide epidemic. While exercise can prevent the onset of diabetes in young subjects its role in older diabetic people is less clear. Exercise stimulates the release of the β(2)-agonist epinephrine more in the young. Although epinephrine and β(2)-agonist drugs cause acute insulin resistance, their chronic effect on insulin sensitivity is unclear. We fed C57BL/6 mice a high fat diet to induce diabetes. These overweight animals became very insulin resistant. Exhaustive treadmill exercise 5 days a week for 8 weeks had no effect on their diabetes, nor did the β(2)-blocking drug ICI 118551. In contrast, exercise combined with the β(2)-agonist salbutamol (albuterol) had a beneficial effect on both glucose tolerance and insulin sensitivity after 4 and 8 weeks of exercise. The effect was durable and persisted 5 weeks after exercise and β(2)-agonist had stopped. To test whether β(2)-agonist alone was effective, the animals that had received β(2)-blockade were then given β(2)-agonist. Their response to a glucose challenge improved but their response to insulin was not significantly altered. The β(2)-agonists are commonly used to treat asthma and asthmatics have an increased incidence of obesity and type 2 diabetes. Although β(2)-agonists cause acute hyperglycemia, chronic treatment improves insulin sensitivity, probably by improving muscle glucose uptake.

Frequency and Outcomes of Hyperlactatemia After Neurosurgery

Objectives. The aim of this study was to evaluate the incidence and significance of elevated serum lactate and its impact on outcome in postoperative neurosurgical patients admitted to neurosurgical intensive care unit (NSICU). Design. This study’s design is a retrospective analysis in a 13-bed NSICU in a tertiary care hospital. A total of 673 patients were screened and 328 patients were included in the study. Methods. Patients were divided into neurosurgery versus nonneurosurgical admissions. Neurosurgical patients were further grouped as brain surgery, spinal surgery, or intracranial vascular surgery. Reason for admission, length of stay, serum lactate levels, and survival were analyzed. Results. The incidence of hyperlactatemia (lactate level ≥2.0 mmol/L) ranged from 67% in the brain tumor group to 33% in the nonneurosurgery group. Mean serum lactates were significantly higher in the brain tumor (3.17 ± 1.99) and spinal surgery groups (2.79 ± 1.51) than in the nonneurosurgery group (1.86 ± 1.10), P < .05, but not in the intracranial vascular surgery group (2.28 ± 1.71), P > .05. The serum lactate level was not significantly associated with survival. Conclusion. Postoperative hyperlactatemia occurs frequently in neurosurgery patients but appears benign.

Association of plasma epinephrine level with insulin sensitivity in metabolically healthy but obese individuals

In the present study, we explored the association of catecholamines with insulin sensitivity in "metabolically healthy but obese" (MHO) individuals, by examining the metabolic characteristics and plasma catecholamine levels in 100 obese, sedentary postmenopausal women. Subjects were classified as MHO (n=25) or at-risk (n=25) based on the upper and lower quartiles of insulin sensitivity as measured by the hyperinsulinemic-euglycemic clamp technique. The MHO group presented a significantly higher range of plasma epinephrine levels (73 ± 21 pg/mL) than the at-risk group (39 ± 20 pg/mL) (P<0.05), though both within the normal basal range of plasma epinephrine (56 ± 30 pg/mL). Multivariate regression analysis showed that high-sensitivity C-reactive protein, plasma epinephrine, triglycerides and lean body mass index were independent predictors of glucose disposal. The plasma epinephrine level was positively correlated with the glucose disposal rate, insulin sensitivity and the HDL-cholesterol level, and negatively correlated with the triglycerides level (P<0.05). In conclusion, this study for the first time demonstrates a positive association between plasma epinephrine level and insulin sensitivity in MHO individuals.

Lactate and acid base as a hemodynamic monitor and markers of cellular perfusion

BACKGROUND

: The intra- and postoperative monitoring of lactate and acid-base has been advocated in pediatric cardiac critical care as surrogate markers of cardiac output, oxygen delivery, and cellular perfusion. Many clinicians use lactate and base excess routinely as markers of tissue perfusion and to assess the effectiveness of their intervention. This review discusses the strengths and weaknesses of using these measurements in pediatric cardiac critical care.

METHODOLOGY

: A search of MEDLINE, EMBASE, PubMed, and the Cochrane Database was conducted to find controlled trials of lactate and base excess. Adult and pediatric data were considered. Guidelines published by the Society of Critical Care Medicine, the American Heart Association, the American Academy of Pediatrics, and the International Liaison Committee on Resuscitation were reviewed including further review of references cited.

RESULTS AND CONCLUSIONS

: Many factors other than tissue hypoxia may contribute to hyperlactemia in critical illness. Although the presence of hyperlactemia on admission appears to be associated with intensive care unit mortality and morbidity in some retrospective analyses, significant overlap between survivors and nonsurvivors means that nonsurvivors cannot be predicted from admission lactate measurement. Persistently elevated postoperative lactate is associated with increased morbidity and mortality in the pediatric cardiac population. To date there is no randomized control trial of goal-directed therapy in adult or pediatric cardiac care that includes normalization of lactate as a target. Overall equivalent time measurements of base excess, anion gap, and pH have a low predictive value for morbidity and mortality in children after cardiac surgery. Lactate is one of a cluster of markers of cellular perfusion and oxygen delivery. Alone, as a single measurement, it has minimal predictive value and is nondiscriminatory for survival.