Propofol cardioprotection for on-pump aortocoronary bypass surgery in patients with type 2 diabetes mellitus (PRO-TECT II): a phase 2 randomized-controlled trial

The Role of GABA Receptors in Anesthesia and Sedation: An Updated Review

GABA (γ-aminobutyric acid) receptors are constituents of many inhibitory synapses within the central nervous system. They are formed by 5 subunits out of 19 various subunits: α1-6, β1-3, γ1-3, δ, ε, θ, π, and ρ1-3. Two main subtypes of GABA receptors have been identified, namely GABAA and GABAB. The GABAA receptor (GABAAR) is formed by a variety of combinations of five subunits, although both α and β subunits must be included to produce a GABA-gated ion channel. Other subunits are γ, δ, ε, π, and ϴ. GABAAR has many isoforms, that dictate, among other properties, their differing affinities and conductance. Drugs acting on GABAAR form the cornerstone of anesthesia and sedation practice. Some such GABAAR agonists used in anesthesia practice are propofol, etomidate, methohexital, thiopental, isoflurane, sevoflurane, and desflurane. Ketamine, nitrous oxide, and xenon are not GABAR agonists and instead inhibit glutamate receptors-mainly NMDA receptors. Inspite of its many drawbacks such as pain in injection, quick and uncontrolled conversion from sedation to general anesthesia and dose-related cardiovascular depression, propofol remains the most popular GABAR agonist employed by anesthesia providers. In addition, being formulated in a lipid emulsion, contamination and bacterial growth is possible. Literature is rife with newer propofol formulations, aiming to address many of these drawbacks, and with some degree of success. A nonemulsion propofol formulation has been developed with cyclodextrins, which form inclusion complexes with drugs having lipophilic properties while maintaining aqueous solubility. Inhalational anesthetics are also GABA agonists. The binding sites are primarily located within α+/β- and β+/α- subunit interfaces, with residues in the α+/γ- interface. Isoflurane and sevoflurane might have slightly different binding sites providing unexpected degree of selectivity. Methoxyflurane has made a comeback in Europe for rapid provision of analgesia in the emergency departments. Penthrox (Galen, UK) is the special device designed for its administration. With better understanding of pharmacology of GABAAR agonists, newer sedative agents have been developed, which utilize "soft pharmacology," a term pertaining to agents that are rapidly metabolized into inactive metabolites after producing desired therapeutic effect(s). These newer "soft" GABAAR agonists have many properties of ideal sedative agents, as they can offer well-controlled, titratable activity and ultrashort action. Remimazolam, a modified midazolam and methoxycarbonyl-etomidate (MOC-etomidate), an ultrashort-acting etomidate analog are two such examples. Cyclopropyl methoxycarbonyl metomidate is another second-generation soft etomidate analog that has a greater potency and longer half-life than MOC-etomidate. Additionally, it might not cause adrenal axis suppression. Carboetomidate is another soft analog of etomidate with low affinity for 11β-hydroxylase and is, therefore, unlikely to have clinically significant adrenocortical suppressant effects. Alphaxalone, a GABAAR agonist, is recently formulated in combination with 7-sulfobutylether-β-cyclodextrin (SBECD), which has a low hypersensitivity profile.

Volatile Anaesthesia versus Total Intravenous Anaesthesia for Cardiac Surgery-A Narrative Review

Recent research has contested the previously accepted paradigm that volatile anaesthetics improve outcomes in cardiac surgery patients when compared to intravenous anaesthesia. In this review we summarise the mechanisms of myocardial ischaemia/reperfusion injury and cardioprotection in cardiac surgery. In addition, we make a comprehensive analysis of evidence comparing outcomes in patients undergoing cardiac surgery under volatile or intravenous anaesthesia, in terms of mortality and morbidity (cardiac, neurological, renal, pulmonary).

Definitions of low cardiac output syndrome after cardiac surgery and their effect on the incidence of intraoperative LCOS: A literature review and cohort study

Objectives

Low cardiac output syndrome (LCOS) is a serious complication after cardiac surgery. Despite scientific interest in LCOS, there is no uniform definition used in current research and clinicians cannot properly compare different study findings. We aimed to collect the LCOS definitions used in literature and subsequently applied the definitions obtained to existing data to estimate their effect on the intraoperative LCOS incidences in adults, children and infants.

Design

This is a literature review, followed by a retrospective cohort study.

Setting

This is a single-institutional study from a university hospital in the Netherlands.

Participants

Patients from all ages undergoing cardiac surgery with cardiopulmonary bypass between June 2011 and August 2018.

Interventions

We obtained different definitions of LCOS used in the literature and applied these to data obtained from an anesthesia information management system to estimate intraoperative incidences of LCOS. We compared intraoperative incidences of LCOS in different populations based on age (infants, children and adults).

Measurements and main results

The literature search identified 262 LCOS definitions, that were applied to intraoperative data from 7,366 patients. Using the 10 most frequently published LCOS definitions, the obtained incidence estimates ranged from 0.4 to 82% in infants, from 0.6 to 56% in children and from 1.5 to 91% in adults.

Conclusion

There is an important variety in definitions used to describe LCOS. When applied to data obtained from clinical care, these different definitions resulted in large distribution of intraoperative LCOS incidence rates. We therefore advocate for standardization of the LCOS definition to improve clinical understanding and enable adequate comparison of outcomes and treatment effects both in daily care and in research.

Hyperoxia During Cardiopulmonary Bypass Is Associated With Mortality in Infants Undergoing Cardiac Surgery

OBJECTIVES

Patients undergoing cardiac surgery using cardiopulmonary bypass have variable degrees of blood oxygen tension during surgery. Hyperoxia has been associated with adverse outcomes in critical illness. Data are not available regarding the association of hyperoxia and outcomes in infants undergoing cardiopulmonary bypass. We hypothesize that among infants undergoing cardiac surgery, hyperoxia during cardiopulmonary bypass is associated with greater odds of morbidity and mortality.

DESIGN

Retrospective study.

SETTING

Single center at an academic tertiary children's hospital.

PATIENTS

All infants (< 1 yr) undergoing cardiopulmonary bypass between January 1, 2015, and December 31, 2017, excluding two patients who were initiated on extracorporeal membrane oxygenation in the operating room.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

The study included 469 infants with a median age of 97 days (interquartile range, 14-179 d), weight 4.9 kg (interquartile range, 3.4-6.4 kg), and cardiopulmonary bypass time 128 minutes (interquartile range, 91-185 min). A Pao2 of 313 mm Hg (hyperoxia) on cardiopulmonary bypass had highest sensitivity with specificity greater than 50% for association with operative mortality. Approximately, half of the population (237/469) had hyperoxia on cardiopulmonary bypass. Infants with hyperoxia were more likely to have acute kidney injury, prolonged postoperative length of stay, and mortality. They were younger, weighed less, had longer cardiopulmonary bypass times, and had higher Society of Thoracic Surgeons and the European Association for Cardio-Thoracic Surgery mortality scores. There was no difference in sex, race, preoperative creatinine, single ventricle physiology, or presence of genetic syndrome. On multivariable analysis, hyperoxia was associated with greater odds of mortality (odds ratio, 4.3; 95% CI, 1.4-13.2) but failed to identify an association with acute kidney injury or prolonged postoperative length of stay. Hyperoxia was associated with greater odds of mortality in subgroup analysis of neonatal patients.

CONCLUSIONS

Hyperoxia occurred in a substantial portion of infants undergoing cardiopulmonary bypass for cardiac surgery. Hyperoxia during cardiopulmonary bypass was an independent risk factor for mortality and may be a modifiable risk factor. Furthermore, hyperoxia during cardiopulmonary bypass was associated with four-fold greater odds of mortality within 30 days of surgery. Hyperoxia failed to identify an association with development of acute kidney injury or prolonged postoperative length of stay when controlling for covariables. Validation of our data among other populations is necessary to better understand and elucidate potential mechanisms underlying the association between excess oxygen delivery during cardiopulmonary bypass and outcome.

Cardioprotective Effect of Anesthetics: Translating Science to Practice

Cardiovascular diseases are the number one cause of mortality in the world, particularly among the aging population. Major adverse cardiac events are also a major contributor to perioperative complications, affecting 2.6% of noncardiac surgeries and up to 18% of cardiac surgeries. Cardioprotective effects of volatile anesthetics and certain intravenous anesthetics have been well-documented in preclinical studies; however, their clinical application has yielded conflicting results in terms of their efficacy. Therefore, better understanding of the underlying mechanisms and developing effective ways to translate these insights into clinical practice remain significant challenges and unmet needs in the area. Several recent reviews have focused on mechanistic dissection of anesthetic-mediated cardioprotection. The present review focuses on recent clinical trials investigating the cardioprotective effects of anesthetics in the past five years. In addition to highlighting the main outcomes of these trials, the authors provide their perspectives about the current gap in the field and potential directions for future investigations.

Preconditioning in cardiac anesthesia…… where are we?

Preconditioning, a milestone concept in the cardiovascular sciences introduced 32 years back by Murry. This concept opened a new era in the field of organ protection. To start with extensive studies done on ischemic preconditioning for myocardial protection, ischemic preconditioning is an endogenous science of cellular kinetics. Several components in signal transduction cascade have been identified but still some mechanisms not yet revealed. Anesthetic preconditioning also contributed a lot for myocardial protection and concreted the concept of preconditioning. We, with an inquisitive brain meticulously persuing newer methods of cardioprotection. Remote ischemic preconditioning (RIPC) is a brilliant example of it. RIPC can be future of cardioprotection, clinical trials and studies proved the benefits but yet to conclude the superiority of RIPC over myocardial ischemic cardioprotection. This review is an attempt to reveal this extraordinary concept with its basic cellular kinetics, methods, and recent trends.

Mitochondrial Dysfunction in Cardiac Surgery

Mitochondria are key to the cellular response to energetic demand, but are also vital to reactive oxygen species signaling, calcium hemostasis, and regulation of cell death. Cardiac surgical patients with diabetes, heart failure, advanced age, or cardiomyopathies may have underlying mitochondrial dysfunction or be more sensitive to perioperative mitochondrial injury. Mitochondrial dysfunction, due to ischemia/reperfusion injury and an increased systemic inflammatory response due to exposure to cardiopulmonary bypass and surgical tissue trauma, impacts myocardial contractility and predisposes to arrhythmias. Strategies for perioperative mitochondrial protection and recovery include both well-established cardioprotective protocols and targeted therapies that remain under investigation.

Remote ischaemic preconditioning for renal and cardiac protection in adult patients undergoing cardiac surgery with cardiopulmonary bypass: systematic review and meta-analysis of randomized controlled trials

Background

The main aim of this systematic review was to assess whether remote ischaemic preconditioning (RIPC) protects kidneys and the heart in cardiac surgery with cardiopulmonary bypass (CPB) and to investigate a possible role of anaesthetic agents.

Methods

Randomized clinical trials (RCTs) on the effects of RIPC through limb ischaemia in adult patients undergoing cardiac surgery with CPB were searched (1965-October 2016) in PubMed, Cochrane Library and article reference lists. A random effects model on standardized mean difference (SMD) for continuous outcomes and the Peto odds ratio (OR) for dichotomous outcomes were used to meta-analyse data. Subgroup analyses to evaluate the effects of different anaesthetic regimens were pre-planned.

Results

Thirty-three RCTs (5999 participants) were included. In the whole group, RIPC did not significantly reduce the incidence of acute kidney injury (AKI), acute myocardial infarction, atrial fibrillation, mortality or length of intensive care unit (ICU) and hospital stays. On the contrary, RIPC significantly reduced the area under the curve for myocardial injury biomarkers (MIBs) {SMD -0.37 [95% confidence interval (CI) -0.53 to - 0.21]} and the composite endpoint incidence [OR 0.85 (95% CI 0.74-0.97)]. In the volatile anaesthetic group, RIPC significantly reduced AKI incidence [OR 0.57 (95% CI 0.41-0.79)] and marginally reduced ICU stay. Conversely, except for MIBs, RIPC had fewer non-significant effects under propofol with or without volatile anaesthetics.

Conclusions

RIPC did not consistently reduce morbidity and mortality in adults undergoing cardiac surgery with CPB. In the subgroup on volatile anaesthetics only, RIPC markedly and significantly reduced the incidence of AKI and composite endpoint as well as myocardial injury.

Effects of propofol on wound closure and barrier function of cultured endothelial cells: An in vitro experimental study

BACKGROUND

Propofol is widely used in routine clinical practice for the induction and maintenance of anaesthesia. Although propofol is regarded as a well tolerated anaesthetic, its effect on intact or damaged endothelial cells has not yet been elucidated.

OBJECTIVE

The aim of this study was to investigate the effects of different concentrations of propofol on cell damage, metabolic activity, barrier function and wound healing capacity of human endothelial cells.

DESIGN

An in vitro investigation.

SETTING

Research Laboratory of the Department of Anaesthesiology and Intensive Care Medicine, University Hospital Schleswig-Holstein, Kiel, Germany.

MATERIALS

In vitro cultures of primary human umbilical vein endothelial cells (HUVECs).

INTERVENTIONS

Intact HUVEC or wounded HUVEC monolayers were incubated with or without different concentrations of propofol (10, 30 and 100 μmol l).

MAIN OUTCOME MEASURES

Cell damage, metabolic activity, monolayer permeability, wound healing capacity, protein phosphorylation.

RESULTS

Propofol did not alter the morphology, induce cell damage or influence metabolic activity of intact HUVEC cells. Permeability of a HUVEC monolayer was increased by propofol 100 μmol l (P < 0.05). Wound closure was inhibited by the addition of propofol 30 and 100 μmol l (P < 0.05 and P < 0.01). This effect was associated with increased phosphorylation of extracellular signal regulated kinases (Erk) 1/2 (30 and 100 μmol l; both P < 0.05) and decreased phosphorylation of Rho kinase (Rock) (100 μmol l; P < 0.05).

CONCLUSION

Propofol does not damage intact endothelial cells, but increases permeability of an endothelial cell monolayer at high concentrations and inhibits wound closure in vitro. Further experimental and clinical in vivo research should be performed to clarify the influence of propofol on endothelial wound healing.

Remote ischemic preconditioning for cardioprotection in elective inpatient abdominal surgery - a randomized controlled trial

Background

Perioperative myocardial injury (PMI) is common in elective inpatient abdominal surgery and correlates with mortality risk. Simple measures for reducing PMI in this cohort are needed. This study evaluated whether remote ischemic preconditioning (RIPC) could reduce PMI in elective inpatient abdominal surgery.

Methods

This was a double-blind, sham-controlled trial with 1:1 parallel randomization. PMI was defined as any post-operative serum troponin T (hs-TNT) > 14 ng/L. Eighty-four participants were randomized to receiving RIPC (5 min of upper arm ischemia followed by 5 min reperfusion, for three cycles) or a sham-treatment immediately prior to surgery. The primary outcome was mean peak post-operative troponin in patients with PMI, and secondary outcomes included mean hs-TnT at individual timepoints, post-operative hs-TnT area under the curve (AUC), cardiovascular events and mortality. Predictors of PMI were also collected. Follow up was to 1 year.

Results

PMI was observed in 21% of participants. RIPC did not significantly influence the mean peak post-operative hs-TnT concentration in these patients (RIPC 25.65 ng/L [SD 9.33], sham-RIPC 23.91 [SD 13.2], mean difference 1.73 ng/L, 95% confidence interval − 9.7 to 13.1 ng/L, P = 0.753). The treatment did not influence any secondary outcome with the pre-determined definition of PMI. Redefining PMI as > 5 ng/L in line with recent data revealed a non-significant lower incidence in the RIPC cohort (68% vs 81%, P = 0.211), and significantly lower early hs-TnT release (12 h time-point, RIPC 5.5 ng/L [SD 5.5] vs sham 9.1 ng/L [SD 8.2], P = 0.03).

Conclusions

RIPC did not at reduce the incidence or severity of PMI in these general surgical patients using pre-determined definitions. PMI is nonetheless common and effective cardioprotective strategies are required.

Trial registration

This trial was registered with Clinicaltrials.gov, NCT01850927, 5th July 2013.

Electronic supplementary material

The online version of this article (10.1186/s12871-018-0524-6) contains supplementary material, which is available to authorized users.

Propofol Protects Rat Cardiomyocytes from Anthracycline-Induced Apoptosis by Regulating MicroRNA-181a In Vitro and In Vivo

We aimed to evaluate the cardioprotective effect and mechanism of propofol in anthracycline-induced cardiomyocyte apoptosis. We selected the rat myocardial cell line, H9c2, and primary cardiomyocytes for in vitro study. The cardiomyocytes were treated with vehicle, Adriamycin® (ADM), propofol, or a combination of ADM and propofol. The proportion of apoptotic cells and the expression of miR-181a were detected by flow cytometry and real-time PCR, respectively. Luciferase assays were performed to explore the direct target gene of miR-181a. In vivo assay, rats were randomly divided into different treatment groups. The apoptosis index was determined by TUNEL staining, and the expression of miR-181a and STAT3 in heart tissue was detected. The antiproliferative effect of ADM alone was significantly greater than that of ADM plus propofol. A significantly greater decrease in the proportion of apoptotic cells and in miR-181a expression was observed in the combination treatment group compared with that in the ADM groups in vitro and in vivo. The loss-of-function of miR-181a in H9c2 of ADM treatment resulted in increased Bcl-2 and decreased Bax. MiR-181a suppressed Bcl-2 expression through direct targeting of the Bcl-2 transcript. Propofol reduced anthracycline-induced apoptosis in cardiomyocytes via targeting miR-181a/Bcl-2, and a negative correlation between miR-181a and Bcl-2 was observed.

The Role of GABA Receptor Agonists in Anesthesia and Sedation

GABA (γ-aminobutyric acid) receptors, of which there are two types, are involved in inhibitory synapses within the central nervous system. The GABA_A receptor (GABAAR) has a central role in modern anesthesia and sedation practice, which is evident from the high proportion of agents that target the GABAAR. Many GABAAR agonists are used in anesthesia practice and sedation, including propofol, etomidate, methohexital, thiopental, isoflurane, sevoflurane, and desflurane. There are advantages and disadvantages to each GABAAR agonist currently in clinical use. With increasing knowledge regarding the pharmacology of GABAAR agonists, however, newer sedative agents have been developed which employ 'soft pharmacology', a term used to describe the pharmacology of agents whereby their chemical configuration allows rapid metabolism into inactive metabolites after the desired therapeutic effect(s) has occurred. These newer 'soft' GABAAR agonists may well approach ideal sedative agents, as they can offer well-controlled, titratable activity and ultrashort action. This review provides an overview of the role that GABAAR agonists currently play in sedation and anesthesia, in addition to discussing the future role of novel GABAAR agonists in anesthesia and sedation.