Metabolic effects of beta 2-agonists

Adrenoceptor Expression and Function in the Endocrine Pancreas

The sympathetic nervous system plays an important role in the regulation of endocrine pancreatic function, most importantly insulin release. Among the nine adrenoceptor (AR) subtypes, the α2A-AR appears to be the subtype most abundantly expressed in the human pancreas. While α2- and β-AR have opposing effects, the net response to sympathetic stimulation is inhibition of insulin secretion mediated by α2-AR located in the plasma membrane of pancreatic β cells. This inhibition may be present physiologically as evidenced by increased insulin secretion in healthy and diabetic humans and animals in response to α2-AR antagonists, a finding that was confirmed in all studies. Based on such data and on an association of an α2A-AR polymorphism, that increases receptor expression levels, with an elevated risk for diabetes, increased α2A-AR signaling in the pancreatic β cells has been proposed as a risk factor for the development of type 2 diabetes. Thus, the α2A-AR was proposed as a drug target for the treatment of some forms of type 2 diabetes. Drug research and development programs leveraging this mechanism have reached the clinical stage, but none have resulted in an approved medicine due to a limited efficacy. While β-AR agonists can increase circulating insulin levels in vivo, it remains controversial whether this includes a direct effect on β cells or occurs secondary to general metabolic effects. Therefore, the regulation of endocrine pancreatic function is physiologically interesting but may be of limited therapeutic relevance.

Lactic Acidosis Induced by Excessive Use of a Long-Acting Beta Agonist

Lactic acidosis is associated with poorer clinical outcomes in critical care. The causes of this condition are divided into two groups: type A (tissue hypoxia) and type B (metabolic abnormalities). Of these, drug-induced lactic acidosis is categorized as type B and is often overlooked due to clinicians' poor awareness. We herein report a rare case of drug-induced lactic acidosis due to excessive use of a long-acting beta agonist (LABA) in a patient with asthma-chronic obstructive pulmonary disease overlap exacerbation. He initially presented with markedly elevated lactate and metabolic acidosis with unknown etiology. A detailed medical interview revealed that he had inhaled a large amount of LABA on the day of admission, which led to our final diagnosis. The patient's respiratory status and lactate levels gradually improved with the appropriate use of inhalation therapy. While there have been many recent reports of lactic acidosis caused by short-acting beta agonists, our case suggests that excessive use of LABAs may also lead to lactic acidosis. Clinicians should be aware of the possibility that LABAs can cause lactic acidosis because poor awareness of the condition may lead to inappropriate patient care.

The Role of G Protein-Coupled Receptors and Receptor Kinases in Pancreatic β-Cell Function and Diabetes

Type 2 diabetes (T2D) mellitus has emerged as a major global health concern that has accelerated in recent years due to poor diet and lifestyle. Afflicted individuals have high blood glucose levels that stem from the inability of the pancreas to make enough insulin to meet demand. Although medication can help to maintain normal blood glucose levels in individuals with chronic disease, many of these medicines are outdated, have severe side effects, and often become less efficacious over time, necessitating the need for insulin therapy. G protein-coupled receptors (GPCRs) regulate many physiologic processes, including blood glucose levels. In pancreatic β cells, GPCRs regulate β-cell growth, apoptosis, and insulin secretion, which are all critical in maintaining sufficient β-cell mass and insulin output to ensure euglycemia. In recent years, new insights into the signaling of incretin receptors and other GPCRs have underscored the potential of these receptors as desirable targets in the treatment of diabetes. The signaling of these receptors is modulated by GPCR kinases (GRKs) that phosphorylate agonist-activated GPCRs, marking the receptor for arrestin binding and internalization. Interestingly, genome-wide association studies using diabetic patient cohorts link the GRKs and arrestins with T2D. Moreover, recent reports show that GRKs and arrestins expressed in the β cell serve a critical role in the regulation of β-cell function, including β-cell growth and insulin secretion in both GPCR-dependent and -independent pathways. In this review, we describe recent insights into GPCR signaling and the importance of GRK function in modulating β-cell physiology. SIGNIFICANCE STATEMENT: Pancreatic β cells contain a diverse array of G protein-coupled receptors (GPCRs) that have been shown to improve β-cell function and survival, yet only a handful have been successfully targeted in the treatment of diabetes. This review discusses recent advances in our understanding of β-cell GPCR pharmacology and regulation by GPCR kinases while also highlighting the necessity of investigating islet-enriched GPCRs that have largely been unexplored to unveil novel treatment strategies.

Rebound hyperkalemia in a dog with albuterol toxicosis after cessation of potassium supplementation

OBJECTIVE

To describe the presentation of rebound hyperkalemia as a delayed side effect of albuterol toxicity in a dog.

CASE SUMMARY

A 3-year-old female neutered mixed-breed dog was presented for albuterol toxicosis that led to a severe hypokalemia, hyperlactatemia, and hyperglycemia. The dog also experienced sinus tachycardia and generalized weakness. Treatment was instituted with intravenous fluid therapy and potassium supplementation, and the dog was monitored with a continuous electrocardiogram. Resolution of hypokalemia was documented 12 hours after initial presentation, at which time fluid therapy and potassium supplementation were discontinued. There were no further periods of sinus tachycardia, but instead the dog developed ventricular ectopy with rapid couplets (instantaneous rates of 300/min). An echocardiogram revealed normal cardiac size and function. Twenty-four hours after presentation, the patient developed severe hyperkalemia, despite discontinuation of fluids and potassium supplementation for 12 hours. Serial venous and urinary electrolytes were performed for determination of the fractional excretion of electrolytes. These data confirmed rebound hyperkalemia (7.0 mmol/L), consistent with a markedly increased fractional excretion of potassium, and secondary to the release of potassium from inside the cells. Fluid therapy with dextrose supplementation was provided until 36 hours postpresentation. The hyperkalemia resolved, and the dog was discharged after 44 hours of hospitalization.

NEW OR UNIQUE INFORMATION PROVIDED

This case documents rebound hyperkalemia following treatment of albuterol toxicosis in a dog. This case highlights the importance of understanding the distribution of total body potassium when treating serum hypokalemia. Transcellular shifts of potassium, as in the case of albuterol toxicosis, can lead to rebound hyperkalemia even after discontinuation of potassium supplementation. This case further explores the utility of fractional excretion of electrolytes in elucidating the etiology and management of electrolyte disturbances.

Asthma and COPD: A Focus on β-Agonists - Past, Present and Future

Asthma has been recognised as a respiratory disorder for millennia and the focus of targeted drug development for the last 120 years. Asthma is one of the most common chronic non-communicable diseases worldwide. Chronic obstructive pulmonary disease (COPD), a leading cause of morbidity and mortality worldwide, is caused by exposure to tobacco smoke and other noxious particles and exerts a substantial economic and social burden. This chapter reviews the development of the treatments of asthma and COPD particularly focussing on the β-agonists, from the isolation of adrenaline, through the development of generations of short- and long-acting β-agonists. It reviews asthma death epidemics, considers the intrinsic efficacy of clinical compounds, and charts the improvement in selectivity and duration of action that has led to our current medications. Important β2-agonist compounds no longer used are considered, including some with additional properties, and how the different pharmacological properties of current β2-agonists underpin their different places in treatment guidelines. Finally, it concludes with a look forward to future developments that could improve the β-agonists still further, including extending their availability to areas of the world with less readily accessible healthcare.

Management of Children with Acute Asthma Attack: A RAND/UCLA Appropriateness Approach

Bronchial asthma is the most frequent chronic disease in children and affects up to 20% of the pediatric population, depending on the geographical area. Asthma symptoms vary over time and in intensity, and acute asthma attack can resolve spontaneously or in response to therapy. The aim of this project was to define the care pathway for pediatric patients who come to the primary care pediatrician or Emergency Room with acute asthmatic access. The project was developed in the awareness that for the management of these patients, broad coordination of interventions in the pre-hospital phase and the promotion of timely and appropriate assistance modalities with the involvement of all health professionals involved are important. Through the application of the RAND method, which obliges to discuss the statements derived from the guidelines, there was a clear increase in the concordance in the behavior on the management of acute asthma between primary care pediatricians and hospital pediatricians. The RAND method was found to be useful for the selection of good practices forming the basis of an evidence-based approach, and the results obtained form the basis for further interventions that allow optimizing the care of the child with acute asthma attack at the family and pediatric level. An important point of union between the primary care pediatrician and the specialist hospital pediatrician was the need to share spirometric data, also including the use of new technologies such as teleconsultation. Monitoring the progress of asthma through spirometry could allow the pediatrician in the area to intervene early by modifying the maintenance therapy and help the patient to achieve good control of the disease.

Pathophysiology of Drug-Induced Hypomagnesaemia

Magnesium (Mg²⁺) is the second most abundant intracellular and fourth extracellular cation found in the body and is involved in a wide range of functions in the human cell and human physiology. Its role in most of the enzyme processes (ATP-ases)-stabilisation of nucleic acids (DNA, RNA), regulation of calcium and potassium ion channels, proliferation, glucose metabolism and apoptosis-make it one of the most important cations in the cell. Three pathogenetic mechanisms are mainly implicated in the development of hypomagnesaemia: reduced food intake, decreased intestinal absorption and increased renal excretion of Mg²⁺. This review presents the function of Mg²⁺, how it is handled in the kidney and the drugs that cause hypomagnesaemia. The frequency and the number of drugs like diuretics and proton-pump inhibitors (PPIs) that are used daily in medical practice are discussed in order to prevent and treat adverse effects by providing an insight into Mg²⁺ homeostasis.

Lessons of the month 1: Salbutamol induced lactic acidosis: clinically recognised but often forgotten

We present the case of an 83-year-old woman, with known asthma, admitted with increasing dyspnoea, wheeze and a productive cough. In addition to maintenance inhaled therapy, the patient was also on long-term mirtazapine and furosemide. Following acute treatment with nebulised salbutamol she became increasingly dyspnoeic and developed a metabolic acidosis with a significantly raised blood lactate level. After cessation of ß₂-adrenergic medication, the patient's clinical condition improved with resolution of her lactic acidosis; salbutamol induced lactic acidosis was diagnosed. This clinical scenario is common but not well described. Here we discuss the mechanisms, investigation and management of raised serum lactate and lactic acidosis in the context of acute asthma and the possible interactions of polypharmacy and comorbidities in the acute medical setting.

Central dopamine D2 receptors regulate plasma glucose levels in mice through autonomic nerves

Recent evidence suggests that the central nervous system (CNS) regulates plasma glucose levels, but the underlying mechanism is unclear. The present study investigated the role of dopaminergic function in the CNS in regulation of plasma glucose levels in mice. I.c.v. injection of neither the dopamine D1 receptor agonist SKF 38393 nor the antagonist SCH 23390 influenced plasma glucose levels. In contrast, i.c.v. injection of both the dopamine D2 receptor agonist quinpirole and the antagonist l-sulpiride increased plasma glucose levels. Hyperglycemia induced by quinpirole and l-sulpiride was absent in dopamine D2 receptor knockout mice. I.c.v. injection of quinpirole and l-sulpiride each increased mRNA levels of hepatic glucose-6-phosphatase and phosphoenolpyruvate carboxykinase, which are the key enzymes for hepatic gluconeogenesis. Systemic injection of the β2 adrenoceptor antagonist ICI 118,551 inhibited hyperglycemia induced by l-sulpiride, but not by quinpirole. In contrast, hyperglycemia induced by quinpirole, but not by l-sulpiride, was inhibited by hepatic vagotomy. These results suggest that stimulation of central dopamine D2 receptors increases plasma glucose level by increasing hepatic glucose production through parasympathetic nerves, whereas inhibition of central dopamine D2 receptors increases plasma glucose level by increasing hepatic glucose production through sympathetic nerves.

Inhaled Albuterol Use and Impaired Lactate Clearance in Patients With Sepsis: A Retrospective Cohort Study

BACKGROUND

Lactate clearance has become important in the management of sepsis. However, factors unrelated to sepsis-induced hyperlactatemia, including β-2 adrenergic agonists, can interfere with lactate clearance.

OBJECTIVES

To investigate the association of inhaled albuterol with lactate clearance in patients with sepsis.

METHODS

This was a single-center retrospective cohort study. Adult patients with sepsis diagnosed in the emergency department from May 2015 to May 2016 with initial lactate levels >2 mmol/L and serial lactate measurements 2 to 6 hours apart were included. Patients were divided into 2 groups based on whether they received inhaled albuterol between lactate measurements. The primary end point was lactate clearance of 10%. Secondary end points included intensive care unit (ICU) consultation and in-hospital mortality. A multivariate logistic regression analysis was performed to assess the effect of inhaled albuterol on lactate clearance.

RESULTS

Of 269 patients included, 58 (22%) received inhaled albuterol between lactate measurements. This group had a significantly higher prevalence of pulmonary disease and a lower initial lactate compared to those who did not receive inhaled albuterol. They had a significantly lower rate of lactate clearance (45% vs 77%, P < .001); however, ICU consultation (71% vs 57%, P = .066) and in-hospital mortality (19% vs 22%, P = .64) were not significantly different. A multivariate logistic regression analysis adjusting for age, sex, chronic kidney disease, cirrhosis, cancer, septic shock or severe sepsis, and the amount of intravenous fluids received showed that inhaled albuterol was independently associated with impaired lactate clearance (adjusted odds ratio: 0.26, 95% confidence interval: 0.14-0.50, P < .001).

CONCLUSIONS

Inhaled albuterol in patients with sepsis was associated with impaired lactate clearance without an increase in ICU consultation or in-hospital mortality. Impaired lactate clearance in patients with sepsis who receive inhaled albuterol should be interpreted with caution.

Selective ß2-Adrenoceptor Agonists and Relevant Hyperlactatemia: Systematic Review and Meta-Analysis

Selective ß₂-agonists have been imputed as potential cause of l-hyperlactatemia since the 1970s. To document the prevalence of hyperlactatemia associated with selective ß₂-agonists and to investigate the predisposing factors, we searched for published articles until April 2019 pertaining to the interplay of administration of selective ß₂-agonists and circulating l-lactic acid in the Excerpta Medica, Web of Science, and the U.S. National Library of Medicine databases. Out of the 1834 initially retrieved records, 56 articles were included: 42 papers reporting individual cases, 2 observational studies, and 12 clinical trials. Forty-seven individual patients receiving a selective ß₂-agonist were found to have l-lactatemia ≥5.0 mmol/L, which decreased by ≥3.0 mmol/L or to ≤2.5 mmol/L after discontinuing (N = 24), reducing (N = 17) or without modifying the dosage of the selective ß₂-agonist (N = 6). Clinical trials found that l-lactic acid significantly increased in healthy volunteers administered a ß₂-agonist. l-lactatemia ≥5.0 mmol/L was observed in 103 (24%) out of 426 patients with asthma or preterm labor managed with a selective ß₂-agonist and was more common in patients with asthma (30%) than in premature labor (5.9%). A significant relationship was also noted between l-lactate level and intravenous albuterol dose or its circulating level. In conclusion, relevant l-hyperlactatemia is common on high dose treatment with a selective ß₂-agonist.

Acid-Base Disturbances in Patients with Asthma: A Literature Review and Comments on Their Pathophysiology

Asthma is a common illness throughout the world that affects the respiratory system function, i.e., a system whose operational adequacy determines the respiratory gases exchange. It is therefore expected that acute severe asthma will be associated with respiratory acid-base disorders. In addition, the resulting hypoxemia along with the circulatory compromise due to heart–lung interactions can reduce tissue oxygenation, with a particular impact on respiratory muscles that have increased energy needs due to the increased workload. Thus, anaerobic metabolism may ensue, leading to lactic acidosis. Additionally, chronic hypocapnia in asthma can cause a compensatory drop in plasma bicarbonate concentration, resulting in non-anion gap acidosis. Indeed, studies have shown that in acute severe asthma, metabolic acid-base disorders may occur, i.e., high anion gap or non-anion gap metabolic acidosis. This review briefly presents studies that have investigated acid-base disorders in asthma, with comments on their underlying pathophysiology.

Beware of beta! A case of salbutamol-induced lactic acidosis in severe asthma

A 22-year-old woman presented with symptoms and signs consistent with acute severe asthma. After significant doses of beta-agonist, she developed a significant lactic acidosis. Significant issues arose in this patient's history with regards to purchase of medications, compliance and follow-up with respiratory service. Beta-adrenergic receptors when stimulated have been hypothesised to increase lipolysis, producing free fatty acids, which inhibit the conversion of pyruvate to coenzyme A within the Krebs cycle. Additional pyruvate is generated through stimulation of glycolysis and glycogenolysis through simultaneous catecholamine surge. This increased pyruvate load is shunted through anaerobic glycolysis, producing increased lactate. Steroid use during an asthma attack enhances the beta-2 receptor sensitivity, further potentiating lactate production. The hyperadrenergic state in this young asthmatic likely resulted in pyruvate and therefore lactate rise and thus metabolic acidosis as mentioned before. This piece highlights a physiological phenomenon that may occur in the context of iatrogenic hyperadrenergism.

Thyrotoxic periodic paralysis triggered by β2-adrenergic bronchodilators

Hypokalemic periodic paralysis is the most common form of periodic paralysis and is characterized by attacks of muscle paralysis associated with a low serum potassium (K+) level due to an acute intracellular shifting. Thyrotoxic periodic paralysis (TPP), characterized by the triad of muscle paralysis, acute hypokalemia, and hyperthyroidism, is one cause of hypokalemic periodic paralysis. The triggering of an attack of undiagnosed TPP by β2-adrenergic bronchodilators has, to our knowledge, not been reported previously. We describe two young men who presented to the emergency department with the sudden onset of muscle paralysis after administration of inhaled β2-adrenergic bronchodilators for asthma. In both cases, the physical examination revealed an enlarged thyroid gland and symmetrical flaccid paralysis with areflexia of lower extremities. Hypokalemia with low urine K+ excretion and normal blood acid-base status was found on laboratory testing, suggestive of an intracellular shift of K+, and the patients' muscle strength recovered at serum K+ concentrations of 3.0 and 3.3 mmol/L. One patient developed hyperkalemia after a total potassium chloride supplementation of 110 mmol. Thyroid function testing was diagnostic of primary hyperthyroidism due to Graves disease in both cases. These cases illustrate that β2-adrenergic bronchodilators should be considered a potential precipitant of TPP.

Metabolic Effects of Clenbuterol and Salbutamol on Pork Meat Studied Using Internal Extractive Electrospray Ionization Mass Spectrometry

Direct mass spectrometry analysis of metabolic effects of clenbuterol and salbutamol on pork quality at the molecular level is incredibly beneficial for food regulations, public health and the development of new anti-obesity drugs. With internal extractive electrospray ionization mass spectrometry (iEESI-MS), nutrients including creatine, amino acids, L-carnitine, vitamin B₆, carnosine and phosphatidylcholines in pork tissue were identified, without sample pretreatment, using collision-induced dissociation (CID) experiments and by comparison with authentic compounds. Furthermore, normal pork samples were clearly differentiated from pork samples with clenbuterol and salbutamol via principal component analysis (PCA). Correlation analysis performed on the spectral data revealed that the above-mentioned nutrients strongly correlated with pork quality, and the absolute intensity of phosphatidylcholines in normal pork was much higher than pork contaminated by clenbuterol and salbutamol. Our findings suggested that clenbuterol and salbutamol may render effects on the activity of carnitine acyltransferase I, hence the process that L-carnitine transports long-chain fatty acids into mitochondria and the formation of phosphatidylcholines might be affected. However, the underlying metabolic mechanisms of clenbuterol and salbutamol on carnitine acyltransferase I requires more comprehensive studies in future work.

Sepsis-induced cardiac dysfunction and β-adrenergic blockade therapy for sepsis

Despite recent advances in medical care, mortality due to sepsis, defined as life-threatening organ dysfunction caused by a dysregulated host response to infection, remains high. Fluid resuscitation and vasopressors are the first-line treatment for sepsis in order to optimize hemodynamic instability caused by vasodilation and increased vascular permeability. However, these therapies, aimed at maintaining blood pressure and blood flow to vital organs, could have deleterious cardiac effects, as cardiomyocyte damage occurs in the early stages of sepsis. Recent experimental and clinical studies have demonstrated that a number of factors contribute to sepsis-induced cardiac dysfunction and the degree of cardiac dysfunction is one of the major prognostic factors of sepsis. Therefore, strategies to prevent further cardiomyocyte damage could be of crucial importance in improving the outcome of sepsis. Among many factors causing sepsis-induced cardiac dysfunction, sympathetic nerve overstimulation, due to endogenous elevated catecholamine levels and exogenous catecholamine administration, is thought to play a major role. β-adrenergic blockade therapy is widely used for ischemic heart disease and chronic heart failure and in the prevention of cardiovascular events in high-risk perioperative patients undergoing major surgery. It has also been shown to restore cardiac function in experimental septic animal models. In a single-center randomized controlled trial, esmolol infusion in patients with septic shock with persistent tachycardia reduced the 28-day mortality. Furthermore, it is likely that β-adrenergic blockade therapy may result in further beneficial effects in patients with sepsis, such as the reduction of inflammatory cytokine production, suppression of hypermetabolic status, maintenance of glucose homeostasis, and improvement of coagulation disorders. Recent accumulating evidence suggests that β-adrenergic blockade could be an attractive therapy to improve the prognosis of sepsis. We await a large multicenter randomized clinical trial to confirm the beneficial effects of β-adrenergic blockade therapy in sepsis, of which mortality is still high.

Lactic acidosis following intentional overdose by inhalation of salmeterol and fluticasone

Salmeterol, a long-acting β2-adrenergic receptor agonist used for the treatment of asthma and chronic obstructive pulmonary disease, has an adverse effects profile that is similar to that of salbutamol and other β2-agonists. We report a sympathomimetic syndrome with metabolic acidosis and hyperlactatemia after intentional inhalation of salmeterol in a suicide attempt. A 16-year-old female patient was admitted to the emergency department approximately 2 hours after having inhaled 60 puffs of a combination of salmeterol xinafoate 25 μg and fluticasone propionate 50 μg. She presented in an anxious state with complaints of palpitations and chest pain. The electrocardiogram demonstrated sinus tachycardia and ST-segment depression in the inferior and anterolateral leads. Laboratory findings showed hypokalemia, hypophosphatemia, and lactic acidosis. Cardiac troponin I and creatine kinase MB remained within the normal range. Treatment was supportive and included intravenous fluids and cautious potassium supplementation. The next day, electrocardiographic and laboratory findings returned to normal. We hypothesize that stimulation of β2-adrenergic receptors by inhalation of salmeterol caused this patient's lactic acidosis. This observation is consistent with the hypothesis that the hyperlactatemia observed during asthma attacks is due in part to the administration of high doses of β2-agonists. Salmeterol overdose by inhalation appears to be sufficient to cause lactic acidosis.

Salbutamol or aminophylline for acute severe asthma: how to choose which one, when and why?

Acute, severe exacerbations of asthma present a challenge due to the significant morbidity associated with this presentation. For exacerbations that are refractory to initial treatments with inhaled and oral therapies, there is still doubt about which intravenous therapies are most likely to be helpful. β-2 agonists and aminophylline have differing mechanisms of action that also affect their adverse effects profiles and these are considered. A review of the available randomised control trials suggests that a bolus of intravenous salbutamol may reduce symptoms and hasten recovery. Aminophylline infusions may improve lung function, and in some studies have been shown to improve symptoms, but the evidence is not clear cut. Decisions about which treatment to use should include risk management considerations such as ease of prescription, preparation and administration factors and availability of high-dependency beds.

A rare case of thyrotoxic periodic paralysis precipitated by hydrocortisone

Thyrotoxic periodic paralysis (TPP) is a rare, but serious condition characterized by acute paralytic attacks and hypokalemia in association with thyrotoxicosis. Although carbohydrate rich meals, strenuous exercise, alcohol, emotional stress are known precipitants of TPP, steroid treatment has rarely been reported to induce TPP. We report a case in which a patient with previously untreated Grave's disease developed TPP following administration of Intravenous hydrocortisone for control of severe anaphylaxis, which to best of our knowledge is very rare.

Intermittent hypoxia-induced glucose intolerance is abolished by α-adrenergic blockade or adrenal medullectomy

Obstructive sleep apnea causes intermittent hypoxia (IH) during sleep and is associated with dysregulation of glucose metabolism. We developed a novel model of clinically realistic IH in mice to test the hypothesis that IH causes hyperglycemia, glucose intolerance, and insulin resistance via activation of the sympathetic nervous system. Mice were exposed to acute hypoxia of graded severity (21, 14, 10, and 7% O2) or to IH of graded frequency [oxygen desaturation index (ODI) of 0, 15, 30, or 60, SpO2 nadir 80%] for 30 min to measure levels of glucose fatty acids, glycerol, insulin, and lactate. Glucose tolerance tests and insulin tolerance tests were then performed under each hypoxia condition. Next, we examined these outcomes in mice that were administered phentolamine (α-adrenergic blockade) or propranolol (β-adrenergic blockade) or that underwent adrenal medullectomy before IH exposure. In all experiments, mice were maintained in a thermoneutral environment. Sustained and IH induced hyperglycemia, glucose intolerance, and insulin resistance in a dose-dependent fashion. Only severe hypoxia (7% O2) increased lactate, and only frequent IH (ODI 60) increased plasma fatty acids. Phentolamine or adrenal medullectomy both prevented IH-induced hyperglycemia and glucose intolerance. IH inhibited glucose-stimulated insulin secretion, and phentolamine prevented the inhibition. Propranolol had no effect on glucose metabolism but abolished IH-induced lipolysis. IH-induced insulin resistance was not affected by any intervention. Acutely hypoxia causes hyperglycemia, glucose intolerance, and insulin resistance in a dose-dependent manner. During IH, circulating catecholamines act upon α-adrenoreceptors to cause hyperglycemia and glucose intolerance.

Inhaled β-agonist therapy and respiratory muscle fatigue as under-recognised causes of lactic acidosis

A 49-year-old man with chronic obstructive pulmonary disease (COPD) presented with significant tachypnoea, fevers, productive cough and increased work of breathing for the previous 4 days. Laboratory data showed elevated lactate of 3.2 mEq/L. Continuous inhaled ipratropium and albuterol nebuliser treatments were administered. Lactate levels increased to 5.5 and 3.9 mEq/L, at 6 and 12 h, respectively. No infectious source was found and the lactic acidosis cleared as the patient improved. The lactic acidosis was determined to be secondary to respiratory muscle fatigue and inhaled β-agonist therapy, two under-recognised causes of lactic acidosis in patients presenting with respiratory distress. Lactic acidosis is commonly used as a clinical marker for sepsis and shock, but in the absence of tissue hypoperfusion and severe hypoxia, alternative aetiologies for elevated levels should be sought to avoid unnecessary and potentially harmful medical interventions.

Micronucleus induction in the bone marrow of rats by pharmacological mechanisms. II: long-acting beta-2 agonism

AZD9708 is a new chemical entity with selective and long-acting β2-agonistic properties currently being evaluated by AstraZeneca for potential use in treatment of respiratory diseases by the inhaled route. As part of the toxicological characterisation of this compound, an increased incidence of micronucleated immature erythrocytes (MIEs) was seen in the bone marrow of rats following single intravenous doses near the maximum tolerated. This effect was seen in the absence of in vitro genotoxicity in bacterial and mammalian cells and no consistent evidence of in vivo DNA damage in the the bone marrow or liver using the comet assay was observed. Because of the lack of signals for mutagenic potential, combined with the observation that MIE frequencies appeared to be increased in only some of the rats and the clearest response was seen at the intermediate dose, it was hypothesised that the effect was secondary to β2-adrenergic receptor overstimulation. Because it appears that this has not been previously described for β2-agonists and because pharmacodynamic/pharmacokinetic factors may influence the response, studies using repeated dosing were performed to investigate whether this would lead to compound-induced tachyphylaxis with tolerance induction and decreased responses indicated by β2-effect biomarkers. A series of experiments confirmed that a sequence of five escalating daily doses leading to systemic exposure corresponding to that after a single dose led to symptomatic tolerance, declining or diminished effects on plasma biomarkers of β2-effects (plasma glucose and potassium) and elimination of the micronucleus response. This suggests that the increased MIE frequencies after single doses of AZD9708 are secondary to physiological overstimulation of β2-adrenergic receptors, not a consequence of genotoxicity.

Age-related impairment in insulin release: the essential role of β(2)-adrenergic receptor

In this study, we investigated the significance of β(2)-adrenergic receptor (β(2)AR) in age-related impaired insulin secretion and glucose homeostasis. We characterized the metabolic phenotype of β(2)AR-null C57Bl/6N mice (β(2)AR(-/-)) by performing in vivo and ex vivo experiments. In vitro assays in cultured INS-1E β-cells were carried out in order to clarify the mechanism by which β(2)AR deficiency affects glucose metabolism. Adult β(2)AR(-/-) mice featured glucose intolerance, and pancreatic islets isolated from these animals displayed impaired glucose-induced insulin release, accompanied by reduced expression of peroxisome proliferator-activated receptor (PPAR)γ, pancreatic duodenal homeobox-1 (PDX-1), and GLUT2. Adenovirus-mediated gene transfer of human β(2)AR rescued these defects. Consistent effects were evoked in vitro both upon β(2)AR knockdown and pharmacologic treatment. Interestingly, with aging, wild-type (β(2)AR(+/+)) littermates developed impaired insulin secretion and glucose tolerance. Moreover, islets from 20-month-old β(2)AR(+/+) mice exhibited reduced density of β(2)AR compared with those from younger animals, paralleled by decreased levels of PPARγ, PDX-1, and GLUT2. Overexpression of β(2)AR in aged mice rescued glucose intolerance and insulin release both in vivo and ex vivo, restoring PPARγ/PDX-1/GLUT2 levels. Our data indicate that reduced β(2)AR expression contributes to the age-related decline of glucose tolerance in mice.

Take my breath away: a case of lactic acidosis in an asthma exacerbation

A 36-year-old male with a history of chronic asthma presented to an emergency department with shortness of breath consistent with an asthma exacerbation. He had persistent tachypnea following inhaled bronchodilator treatment; thus, the workup and differential diagnosis were expanded. He was found to have a mixed respiratory alkalosis and metabolic acidosis with elevated serum lactate without an obvious cause and was admitted to hospital. His case was reviewed, and the lactic acidosis was thought to be caused by inhaled β2-agonist use. Emergency physicians should be aware of the potential side effects of inhaled β2-agonists as lactic acidosis may complicate clinical assessment and management of asthma exacerbations and lead to unnecessary and potentially dangerous escalations in therapy.

Serum magnesium and stable asthma: Is there a link?

Background:

Although magnesium is used through intravenous and inhalation route in the management of asthma, actual prevalence of hypomagnesemia in asthma is not known. We conducted this study: 1) to detect the prevalence of hypomagnesemia in stable asthma and 2) to assess the significance of hypomagnesemia in these patients.

Design:

Prospective clinical study.

Setting:

Department of Respiratory Medicine, Calcutta National Medical College, Kolkata.

Period of Study:

Four months from January, 2007, to April, 2007.

Materials and Methods:

Fifty patients attending outpatients department of respiratory medicine with stable asthma were randomly selected. They were assessed clinically and their serum magnesium levels were measured. This was compared with the serum magnesium values of 45 nonasthmatic healthy controls.

Results:

Out of 50 patients, 14 had hypomagnesemia. Possible relationship of hypomagnesemia with tachycardia, tachypnoea, severity of asthma, medication use, and previous and future exacerbations were analyzed.

Conclusion:

There was statistically significant association of hypomagnesemia with tachypnoea, severe asthma, use of long-acting β-agonist, inhaled corticosteroids, theophylline, use of ≥ 3 medications, previous and future exacerbations but not with tachycardia or use of short-acting β₂ -agonist or montelukast.

Bench-to-bedside review: Beta-adrenergic modulation in sepsis

Sepsis, despite recent therapeutic progress, still carries unacceptably high mortality rates. The adrenergic system, a key modulator of organ function and cardiovascular homeostasis, could be an interesting new therapeutic target for septic shock. β-Adrenergic regulation of the immune function in sepsis is complex and is time dependent. However, β₂ activation as well as β₁ blockade seems to downregulate proinflammatory response by modulating the cytokine production profile. β₁ blockade improves cardiovascular homeostasis in septic animals, by lowering myocardial oxygen consumption without altering organ perfusion, and perhaps by restoring normal cardiovascular variability. β-Blockers could also be of interest in the systemic catabolic response to sepsis, as they oppose epinephrine which is known to promote hyperglycemia, lipid and protein catabolism. The role of β-blockers in coagulation is less clear cut. They could have a favorable role in the septic pro-coagulant state, as β₁ blockade may reduce platelet aggregation and normalize the depressed fibrinolytic status induced by adre-nergic stimulation. Therefore, β₁ blockade as well as β₂ activation improves sepsis-induced immune, cardiovascular and coagulation dysfunctions. β₂ blocking, however, seems beneficial in the metabolic field. Enough evidence has been accumulated in the literature to propose β- adrenergic modulation, β₁ blockade and β₂ activation in particular, as new promising therapeutic targets for septic dyshomeostasis, modulating favorably immune, cardiovascular, metabolic and coagulation systems.

Metabolic acidosis as an underlying mechanism of respiratory distress in children with severe acute asthma

OBJECTIVE

1) To alert the clinician that increasing rate and depth of breathing during treatment of acute asthma may be a manifestation of metabolic acidosis with hyperventilation rather than worsening airway obstruction; and 2) to describe the frequency of metabolic acidosis with hyperventilation in children with severe acute asthma admitted to our pediatric intensive care unit.

DESIGN

Retrospective medical record review.

SETTING

University-affiliated children's hospital.

PATIENTS

All patients admitted to the pediatric intensive care unit with a diagnosis of asthma between January 1, 2005, and December 31, 2005.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

Fifty-three patients with asthma (median age 7.8 yrs, range 0.7-17.9 yrs; 35 [66%] male; 46 [87%] black and 7 [13%] white) were admitted to the pediatric intensive care unit during the study period. Fifteen (28%) patients developed metabolic acidosis with hyperventilation (pH <7.35, Pco2 <35 torr [4.6 kPa], and base excess < or = -7 mmol/L) during their hospital course. Of these, lactic acid was assessed in four patients and was elevated in each; all had hyperglycemia (blood glucose >120 mg/dL [6.7 mmol/L]). Patients who developed metabolic acidosis with hyperventilation received asthma therapy similar to that received by patients who did not develop the disorder. Metabolic acidosis resolved contemporaneously with tapering of beta2-adrenergic agonists and administration of supportive care. All patients survived.

CONCLUSIONS

Metabolic acidosis with hyperventilation manifesting as respiratory distress can occur in children with severe acute asthma. A pathophysiologic rationale exists for the contribution of beta2-adrenergic agents to the development of this acid-base disorder. Failure to recognize metabolic acidosis as the underlying mechanism of respiratory distress may lead to inappropriate intensification of bronchodilator therapy. Supportive care and tapering of beta2-adrenergic agents are recommended to resolve this condition.

Metabolism modulators in sepsis: Propranolol

Sepsis is accompanied by an enormous increase in catecholamine expression, leading to metabolism of lipids and glucose, changes in cardiovascular output, immunomodulatory effects, and changes in protein metabolism, all of which push the body into a catabolic state. Deleterious beta-adrenoceptor controlled responses to stress and sepsis are well documented; therefore, it would seem appropriate to use propranolol under such circumstances. There are arguments both for and against the use of beta-adrenoceptor blockade during episodes of stress and infection. The definition of sepsis itself is a clinical one in most cases. There are guidelines concerning the diagnosis of sepsis (systemic inflammatory response syndrome [SIRS] in the presence of significant infection). However, when the cause of SIRS is not infection, for example, in burn patients, is it not possible, and indeed preferable, to tackle the stress response in a more aggressive fashion? The effects of SIRS on the body are myriad and have been defined and illustrated in many fine reviews. The effects of sepsis on the body, as well, have been discussed in the world literature and are beyond the scope of this article. In this article we attempt to demonstrate the effects of sepsis (SIRS plus infection) on whole body metabolism, outline the mediators of these changes, and then show the ability of propranolol to attenuate the changes seen.

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.

Grave acidosis after severe anaphylactic bronchospasm: friend or foe?

In a 20-year-old woman with known asthma, anaphylactic bronchospasm induced a grave combined respiratory and metabolic acidosis (pH(a) 6.66) with marked hypoxaemia (S(a)O(2) 45%). The beneficial effects of the rightward shift of the oxyhaemoglobin dissociation curve on tissue O(2) unloading at such pH was more than offset by the negative effect on S(a)O(2) at the reduced P(a)O(2) (7.0 kPa) found in this patient. This case illustrates the detrimental effect of grave acidosis on arterial blood oxygen content at subnormal P(a)O(2) values, the beneficial effect of a supranormal P(a)O(2) on the S(a)O(2) in such patients, and the rapid remission rate of life-threatening acidosis and blood lactate after adequate ventilation and tissue oxygenation were secured. The initial treatment of the patient and clinically relevant considerations are discussed.

[Metabolic acidosis in a context of acute severe asthma]

In a context of asthma, lactic acidosis may occur during beta2-agonist therapy. Several cases have been reported during its administration by intravenous and/or inhaled route. This side-effect seems rather unknown and the mechanism for compensation of metabolic acidosis by hyperventilation may worsen dyspnoea and mislead clinicians. Other causes of lactic acidosis such as a major hypoxemia, a cardiovascular collapse or sepsis may also be experienced in this context and must be ruled out before attributing the lactic acidosis to beta2-agonist treatment. We report the case of a 50-year-old man hospitalized for an acute major asthma, who received a salbutamol continuous infusion associated with inhaled terbutaline. A serum lactate level of 13 mmol/l was noted eight hours after the introduction of the bronchodilator treatment. After reducing doses of beta2-agonists, the evolution was favourable, regarding both respiratory and metabolic aspects, with a rapid decrease of the serum lactate level, which finally returned to normal level after 32 hours of hospitalization.

Mechanisms by which systemic salbutamol increases ventilation

BACKGROUND AND OBJECTIVE

Salbutamol (SAL) has systemic effects that may adversely influence ventilation in asthmatic patients. The authors sought to determine the magnitude of this effect and mechanisms by which i.v. SAL affects ventilation.

METHODS

A prospective study of nine healthy subjects (eight men, one woman; age 23 +/- 1.4 years (SD)) was undertaken. Each subject received i.v. SAL at 5, 10 and 20 microg/min each for 30 min at each dose and was observed for 1 h post infusion. Minute ventilation ((VE)), oxygen consumption (VO(2)), CO(2) production (VCO(2)), occlusion pressure (P(0.1)), heart rate, blood pressure, respiratory rate, glucose, arterial blood gases, lactate and potassium (K(+)) were recorded at baseline and at 30-min intervals. The effect of 100% oxygen on (VE) and P(0.1) during SAL infusion at 20 microg/min was observed. Results are expressed as mean +/- SEM.

RESULTS

V(E) was significantly increased at 20 microg/min SAL (37.8 +/- 12.1%, P = 0.01), as were VO(2) (22.5 +/- 5.1%, P < 0.01) and VCO(2) (40.9 +/- 10.6%, P < 0.01). Ventilation was in excess of metabolic needs as demonstrated by a rise in the respiratory exchange ratio (0.87 +/- 0.03 to 0.99 +/- 0.04, P < 0.05). Serum lactate rose by 124 +/- 30.4% from baseline to 20 microg/min (1.1 +/- 0.1 to 2.3 +/- 0.25 mmol/L, P < 0.01) and base excess decreased (0.89 +/- 0.56 to vs. -1.75 +/- 0.52 mmol/L, P < 0.01) consistent with a lactic acidosis contributing to the excess ventilation. There was no significant differences in (VE) or P(0.1) with F(I)O(2) = 1.0, suggesting peripheral chemoreceptor stimulation was not responsible for the rise in (VE). At 20 microg/min SAL, K(+) fell significantly from baseline (3.8 +/- 0.06 to 2.8 +/- 0.09 mmol/L, P < 0.001).

CONCLUSION

Systemic SAL imposes ventilatory demands by increasing metabolic rate and serum lactate. This may adversely affect patients with severe asthma with limited ventilatory reserve.

Vasopressors and intestinal mucosal perfusion after cardiac surgery: Norepinephrine vs. phenylephrine

OBJECTIVES

To evaluate the potential differential effects of norepinephrine, an alpha1-, beta1-, and beta2-receptor agonist, to the alpha1-agonist phenylephrine on jejunal mucosal perfusion, gastric-arterial PCO2 gradient, and the global splanchnic oxygen demand-supply relationship after cardiac surgery.

DESIGN

A randomized, prospective, interventional crossover study.

SETTING

A university cardiothoracic intensive care unit.

PATIENTS

Ten patients were studied during propofol sedation and mechanical ventilation after uncomplicated coronary artery bypass surgery.

INTERVENTIONS

Each patient received randomly and sequentially norepinephrine (0.052+/-0.009 microg/kg/min) and phenylephrine (0.50+/-0.22 microg/kg/min) to increase mean arterial blood pressure by 30%.

MEASUREMENTS AND MAIN RESULTS

Data on jejunal mucosal perfusion, jejunal mucosal hematocrit, and red blood cell velocity (laser Doppler flowmetry) as well as gastric-arterial Pco2 gradient (tonometry) and splanchnic oxygen extraction were obtained before (control) and during a 30-min drug infusion period after the target mean arterial blood pressure was reached. The procedure was sequentially repeated for the second vasopressor. Both drugs induced a 40-46% increase in systemic vascular resistance with no change in cardiac index. Neither jejunal mucosal perfusion, jejunal mucosal hematocrit, red blood cell velocity, nor gastric-arterial Pco2 gradient was affected by any of the vasopressors. Splanchnic oxygen extraction increased from 38.2% to 43.1% (p<.001) with norepinephrine and from 39.3% to 47.5% (p<.001) with phenylephrine. This increase was significantly more pronounced with phenylephrine compared with norepinephrine (p<.05). Mixed venous-hepatic vein oxygen saturation gradient increased with both drugs (p<.01), and the increase was more pronounced with phenylephrine (p<.05). Splanchnic lactate extraction was not significantly affected by any of the vasopressors.

CONCLUSIONS

Phenylephrine induced a more pronounced global alpha1-mediated splanchnic vasoconstriction compared with norepinephrine. Neither of the vasoconstrictors impaired perfusion of the gastrointestinal mucosa in postcardiac surgery patients. The lack of norepinephrine-induced, alpha1-mediated impairment of gastrointestinal perfusion is not explained by a beta2-mediated counteractive vasodilation but instead by possible mucosal autoregulatory escape.

Systemic inflammatory response to exhaustive exercise in patients with chronic obstructive pulmonary disease

Systemic inflammation may be present in patients with chronic obstructive pulmonary disease (COPD). Exercise is known to elicit an inflammatory response. We hypothesized that the systemic inflammatory response to exercise might be exaggerated in COPD patients compared to healthy subjects. Sixteen COPD patients and 11 healthy subjects performed a maximal incremental bicycle test. Before and at maximal exercise arterial blood samples were taken to determine circulating catecholamines, (subsets of) leukocytes, acute phase proteins, creatine kinase and myoglobin. At rest, increased levels of norepinephrine and systemic inflammation were present in COPD. The response of catecholamines to exercise was lower in COPD patients (P<0.01), which in part was due to the lower maximal exercise capacity of these patients (P<0.01). Exercise-induced leukocytosis showed similar responses in both groups, but occurred at higher levels in COPD. Although patients had increased levels of CRP at rest (P<0.001), exercise did not affect acute phase proteins. No systemic signs of muscle damage were found. The present study shows that COPD patients are exposed to systemic inflammation that is intensified by exhaustive exercise. The inflammatory response in COPD is not exaggerated compared to healthy subjects but occurs at a higher level and is observed at lower external workload.

Elevated plasma lactate level associated with high dose inhaled albuterol therapy in acute severe asthma

BACKGROUND

Lactic acidosis is a recognised event in adult patients with status asthmaticus, particularly in the setting of intensive care. However, it has been infrequently studied in patients attending the emergency departments (ED).

METHODS

We conducted a prospective and descriptive study to assess levels of lactate and effects on bronchodilator response in adult patients with acute severe asthma treated with high doses of albuterol in the ED. In total, 18 subjects (mean (SD) age 42.9 (2.7) years, FEV1 = 32.2 (10.9)% of predicted) who presented to an emergency department were enrolled in the study. All patients were treated with albuterol; four puffs (100 microg/puff) at 10 minute intervals, delivered by a pressurised metered dose inhaler into a spacer device over a 2 hour period.

RESULTS

At the end of treatment, mean (SD) plasma lactate level (2.94 (2.1) mmol/l) was significantly higher (p = 0.001) than baseline. Of the 18 patients, nine (50%) showed lactate levels > or = 2.5 mmol/l (four patients presented values > 4 mmol/l); these patients had a shorter duration of attack prior to ED presentation (p = 0.01), a higher pretreatment heart rate (p = 0.005), a lower pretreatment SpO2 (p = 0.03), a lower pretreatment PO2 (p = 0.009), a higher pretreatment PCO2, and a lower pretreatment serum potassium (p = 0.005). However, there were no significant differences in the airway response between groups.

CONCLUSIONS

This study confirmed previous observations that high lactate concentrations can develop during the first hours of inhaled beta agonist treatment. The presence of a previous hyperadrenergic state may predispose to the development of this condition. A significant improvement in lung function was associated with elevated lactate levels.

Respiratory medications and the risk of cardiac arrhythmias

BACKGROUND

Medications used to treat respiratory diseases include beta-adrenoceptors, antimuscarinics, inhaled and oral corticosteroids, and theophyllines. Most of these drugs have been associated indirectly with cardiac rhythm disorders, but epidemiologic evidence is limited.

METHODS

To evaluate the association between respiratory drugs and the occurrence of rhythm disorders among patients with asthma and those with chronic obstructive pulmonary disease, we conducted a case-control study nested in a population-based cohort of individuals 10-79 years of age and registered in the U.K. General Practice Research Database after 1 January 1994. The analysis included 710 confirmed cases and 5000 controls frequency-matched to cases by age (interval of 1 year) and sex.

RESULTS

No increased risk of arrhythmias overall was found among users of inhaled steroids (relative risk = 1.0; 95% confidence interval = 0.8-1.3). Short-term use of theophylline was weakly associated with arrhythmia (1.8; 1.0-3.3). An increased risk was found among users of oral steroids, and the relative risk was greater at the beginning of therapy (2.6; 2.0-3.5). The risk of atrial fibrillation was increased, especially for short-term use of oral steroids (2.7; 1.9-3.8), and a weak association was seen for theophyllines, especially short-term use (1.8; 0.9-3.7). Supraventricular tachycardia was associated with long-term use of oral steroids (2.1; 0.8-5.7), long-term use of antimuscarinics (1.7; 0.7-4.1), and short-term use of theophylline (4.0; 0.9-18.1). Ventricular arrhythmias were associated with oral steroids (3.2; 0.8-13.3) and beta-adrenoceptors (7.1; 0.8-65.9).

CONCLUSIONS

Oral steroids and theophylline were the therapeutic groups associated with risk of developing atrial fibrillation, especially with new courses of therapy. Results from this study also are consistent with certain suspected dysrhythmic effects of theophyllines, with supraventricular tachycardia associated with antimuscarinics, and with ventricular arrhythmias associated with beta-adrenoceptors.

Cardiovascular safety of beta(2)-adrenoceptor agonist use in patients with obstructive airway disease: a systematic review

BACKGROUND

beta(2)-Adrenoceptor agonists have been used as bronchodilators in the management of asthma and chronic obstructive pulmonary disease (COPD); however, there is evidence suggesting that beta(2)-adrenoceptor agonist use may increase morbidity and mortality.

METHODS

A systematic review of case-control studies and randomised controlled trials was performed to evaluate the cardiovascular safety of beta(2)-adrenoceptor agonist use in patients with obstructive airway disease, defined as asthma or COPD.

RESULTS

Case-control studies have shown that beta(2)-adrenoceptor agonist use is associated with an increased risk of myocardial infarction, congestive heart failure, cardiac arrest and sudden cardiac death. The degree of risk appears to be dose-dependent, and may be highest for new users and those with concomitant cardiac conditions. Pooled data from randomised placebo-controlled trials indicate that beta(2)-adrenoceptor agonist use increases the risk of adverse cardiovascular events by more than 2-fold compared with placebo, thus providing evidence that the association seen in case-control studies is a causal one. Single doses of beta(2)-adrenoceptor agonists significantly increase heart rate and decrease potassium concentrations compared with placebo.

CONCLUSIONS

Initiation of beta(2)-adrenoceptor agonist treatment increases heart rate and decreases potassium concentrations, while continued use may increase the risk of adverse cardiovascular events. It could be through these effects of beta-adrenergic stimulation that beta(2)-adrenoceptor agonists may induce ischaemia, congestive heart failure, arrhythmias and sudden cardiac death. In addition to increasing adverse cardiovascular events, beta(2)-adrenoceptor agonist use may induce respiratory tolerance and increase the risk of asthma attacks. It is not clear whether beta(2)-adrenoceptor agonists should be used regularly in the treatment of obstructive airway disease, with or without concomitant cardiovascular disease.

Cardiovascular Effects of β-Agonists in Patients With Asthma and COPD

BACKGROUND

beta-Adrenergic agonists exert physiologic effects that are the opposite of those of beta-blockers. beta-Blockers are known to reduce morbidity and mortality in patients with cardiac disease. beta(2)-Agonist use in patients with obstructive airway disease has been associated with an increased risk for myocardial infarction, congestive heart failure, cardiac arrest, and acute cardiac death.

OBJECTIVES

To assess the cardiovascular safety of beta(2)-agonist use in patients with obstructive airway disease, defined as asthma or COPD.

METHODS

A meta-analysis of randomized placebo-controlled trials of beta(2)-agonist treatment in patients with obstructive airway disease was performed, to evaluate the short-term effect on heart rate and potassium concentrations, and the long-term effect on adverse cardiovascular events. Longer duration trials were included in the analysis if they reported at least one adverse event. Adverse events included sinus and ventricular tachycardia, syncope, atrial fibrillation, congestive heart failure, myocardial infarction, cardiac arrest, or sudden death.

RESULTS

Thirteen single-dose trials and 20 longer duration trials were included in the study. A single dose of beta(2)-agonist increased the heart rate by 9.12 beats/min (95% confidence interval [CI], 5.32 to 12.92) and reduced the potassium concentration by 0.36 mmol/L (95% CI, 0.18 to 0.54), compared to placebo. For trials lasting from 3 days to 1 year, beta(2)-agonist treatment significantly increased the risk for a cardiovascular event (relative risk [RR], 2.54; 95% CI, 1.59 to 4.05) compared to placebo. The RR for sinus tachycardia alone was 3.06 (95% CI, 1.70 to 5.50), and for all other events it was 1.66 (95% CI, 0.76 to 3.6).

CONCLUSION

beta(2)-Agonist use in patients with obstructive airway disease increases the risk for adverse cardiovascular events. The initiation of treatment increases heart rate and reduces potassium concentrations compared to placebo. It could be through these mechanisms, and other effects of beta-adrenergic stimulation, that beta(2)-agonists may precipitate ischemia, congestive heart failure, arrhythmias, and sudden death.

Metabolic alterations in sepsis and vasoactive drug-related metabolic effects

The main clinical characteristics of sepsis and septic shock are derangements of cardiocirculatory and respiratory function. Additionally, profound alterations in metabolic pathways occur leading to hypermetabolism, enhanced energy expenditure, and insulin resistance. The clinical hallmarks are hyperglycemia, hyperlactatemia, and enhanced protein catabolism. These metabolic alterations are even more pronounced during sepsis as a result of cytokine release and subsequent induction of inflammatory pathways. Increased oxygen demands from mitochondrial oxygen utilization and oxygen consumption related to oxygen radical formation may contribute to hypermetabolism. In addition, mitochondrial dysfunction with impaired cellular respiration may be present. Mainstay therapeutic interventions for hemodynamic stabilization are adequate volume resuscitation and vasoactive agents, which, however, have additional impact on metabolic activity. Therefore, beyond hemodynamic effects, specific drug-related metabolic alterations need to be considered for optimal treatment during sepsis. This review gives an overview of the typical metabolic alterations during sepsis and septic shock and highlights the impact of vasoactive therapy on metabolism.