The Effect of β2-Adrenoceptor Genotype on Phenylephrine Dose Administered During Spinal Anesthesia for Cesarean Delivery

Neonatal Abstinence Signs during Treatment: Trajectory, Resurgence and Heterogeneity

Neonatal abstinence syndrome (NAS) presents with a varying severity of withdrawal signs and length of treatment (LOT). We examined the course and relevance of each of the NAS withdrawal signs during treatment in a sample of 182 infants with any prenatal opioid exposure, gestational age ≥ 35 weeks, without other medical conditions, and meeting the criteria for pharmacological treatment. Infants were monitored using the Finnegan Neonatal Abstinence Scoring Tool. Daily mean Finnegan scores were estimated using linear mixed models with random subject effects to account for repeated withdrawal scores from the same subject. Daily item prevalence was estimated using generalized estimating equations with a within-subject exchangeable correlation structure. The median LOT was 12.86 days. The prevalence of withdrawal signs decreased from day one to day three of treatment. However, certain central nervous system (CNS) and gastrointestinal (GI) signs showed sporadic increases in prevalence notable around two weeks of treatment, accounting for increases in Finnegan scores that guided pharmacotherapy. We question whether the resurgence of signs with a prolonged LOT is mainly a consequence of opioid tolerance or withdrawal. Monitoring CNS and GI signs throughout treatment is crucial. Future studies directed to better understand this clinical phenomenon may lead to the refining of NAS pharmacotherapy and perhaps the discovery of treatment alternatives.

Cerebrovascular Response to Phenylephrine in Traumatic Brain Injury: A Scoping Systematic Review of the Human and Animal Literature

Intravenous phenylephrine (PE) is utilized commonly in critical care for cardiovascular support. Its impact on the cerebrovasculature is unclear and its use may have important implications during states of critical neurological illness. The aim of this study was to perform a scoping review of the literature on the cerebrovascular/cerebral blood flow (CBF) effects of PE in traumatic brain injury (TBI), evaluating both animal models and human studies. We searched MEDLINE, BIOSIS, EMBASE, Global Health, SCOPUS, and the Cochrane Library from inception to January 2020. We identified 12 studies with various animal models and 4 studies in humans with varying TBI pathology. There was a trend toward a consistent increase in mean arterial pressure (MAP) by the injection of PE systemically, and by proxy, an increase of the cerebral perfusion pressure (CPP). There was a consistent constriction of cerebral vessels by PE reported in the small number of studies documenting such a response. However, the heterogeneity of the literature on the CBF/cerebral blood volume (CBV) response makes the strength of the conclusions on PE limited. Studies were heterogeneous in design and had significant limitations, with most failing to adjust for confounding factors in cerebrovascular/CBF response. This review highlights the significant knowledge gap on the cerebrovascular/CBF effects of PE administration in TBI, calling for further study on the impact of PE on the cerebrovasculature both in vivo and in experimental settings.

Dissecting genetic factors affecting phenylephrine infusion rates during anesthesia: a genome-wide association study employing EHR data

BACKGROUND

The alpha-adrenergic agonist phenylephrine is often used to treat hypotension during anesthesia. In clinical situations, low blood pressure may require prompt intervention by intravenous bolus or infusion. Differences in responsiveness to phenylephrine treatment are commonly observed in clinical practice. Candidate gene studies indicate genetic variants may contribute to this variable response.

METHODS

Pharmacological and physiological data were retrospectively extracted from routine clinical anesthetic records. Response to phenylephrine boluses could not be reliably assessed, so infusion rates were used for analysis. Unsupervised k-means clustering was conducted on clean data containing 4130 patients based on phenylephrine infusion rate and blood pressure parameters, to identify potential phenotypic subtypes. Genome-wide association studies (GWAS) were performed against average infusion rates in two cohorts: phase I (n = 1205) and phase II (n = 329). Top genetic variants identified from the meta-analysis were further examined to see if they could differentiate subgroups identified by k-means clustering.

RESULTS

Three subgroups of patients with different response to phenylephrine were clustered and characterized: resistant (high infusion rate yet low mean systolic blood pressure (SBP)), intermediate (low infusion rate and low SBP), and sensitive (low infusion rate with high SBP). Differences among clusters were tabulated to assess for possible confounding influences. Comorbidity hierarchical clustering showed the resistant group had a higher prevalence of confounding factors than the intermediate and sensitive groups although overall prevalence is below 6%. Three loci with P < 1 × 10^-6 were associated with phenylephrine infusion rate. Only rs11572377 with P = 6.09 × 10^-7, a 3'UTR variant of EDN2, encoding a secretory vasoconstricting peptide, could significantly differentiate resistant from sensitive groups (P = 0.015 and 0.018 for phase I and phase II) or resistant from pooled sensitive and intermediate groups (P = 0.047 and 0.018).

CONCLUSIONS

Retrospective analysis of electronic anesthetic records data coupled with the genetic data identified genetic variants contributing to variable sensitivity to phenylephrine infusion during anesthesia. Although the identified top gene, EDN2, has robust biological relevance to vasoconstriction by binding to endothelin type A (ET_A) receptors on arterial smooth muscle cells, further functional as well as replication studies are necessary to confirm this association.

The pharmacogenetics of natural products: A pharmacokinetic and pharmacodynamic perspective

Natural products have represented attractive alternatives for disease prevention and treatment over the course of human history and have contributed to the development of modern drugs. These natural products possess beneficial efficacies as well as adverse efffects, which vary largely among individuals because of genetic variations in their pharmacokinetics and pharmacodynamics. As with other synthetic chemical drugs, the dosing of natural products can be optimized to improve efficacy and reduce toxicity according to the pharmacogenetic properties. With the emergence and development of pharmacogenomics, it is possible to discover and identify the targets/mechanisms of pharmacological effects and therapeutic responses of natural products effectively and efficiently on the whole genome level. This review covers the effects of genetic variations in drug metabolizing enzymes, drug transporters, and direct and indirect interactions with the pharmacological targets/pathways on the individual response to natural products, and provides suggestions on dosing regimen adjustments of natural products based on their pharmacokinetic and pharmacogenetic paratmeters. Finally, we provide our viewpoints on the importance and necessity of pharmacogenetic and pharmacogenomic research of natural products in natural medicine's rational development and clinical application of precision medicine.

Endogenous Opiates and Behavior: 2016

This paper is the thirty-ninth consecutive installment of the annual review of research concerning the endogenous opioid system. It summarizes papers published during 2016 that studied the behavioral effects of molecular, pharmacological and genetic manipulation of opioid peptides, opioid receptors, opioid agonists and opioid antagonists. The particular topics that continue to be covered include the molecular-biochemical effects and neurochemical localization studies of endogenous opioids and their receptors related to behavior, and the roles of these opioid peptides and receptors in pain and analgesia, stress and social status, tolerance and dependence, learning and memory, eating and drinking, drug abuse and alcohol, sexual activity and hormones, pregnancy, development and endocrinology, mental illness and mood, seizures and neurologic disorders, electrical-related activity and neurophysiology, general activity and locomotion, gastrointestinal, renal and hepatic functions, cardiovascular responses, respiration and thermoregulation, and immunological responses.

Pharmacogenetics in obstetric anesthesia

The 21st century has been billed as the era of "precision/personalized medicine." Genetic investigation of clinical syndromes may guide therapy as well as reveal previously unknown biological or pharmacological pathways that may result in novel drug therapies. Several clinical issues in obstetrics and obstetric anesthesiology have been targets for genetic investigations. These include evaluation of the genetic effects on preterm labor and the progression of labor, spinal anesthesia-induced hypotension and the response to medications used to treat hypotension, and the effect of gene variants on pain and analgesic responses. Most studies have examined specific single nucleotide polymorphisms. Findings have revealed modest effects of genetic variation without tangible impact on current clinical practice. Over the next decade, increased availability of whole exome and genome sequencing, epigenetics, large genetic databases, computational biology and other information technology, and more rapid methods of real-time genotyping may increase the impact of genetics in the clinical arena of obstetrics and obstetric anesthesia.

Pharmacogenetics and anaesthetic drugs: Implications for perioperative practice

Pharmacogenetics seeks to elucidate the variations in individual's genetic sequences in order to better understand the differences seen in pharmacokinetics, drug metabolism, and efficacy between patients. This area of research is rapidly accelerating, aided by the use of novel and more economical molecular technologies. A substantial evidence base is being generated with the hopes that in the future it may be used to generate personalised treatment regimens in order to improve patient comfort and safety and reduce incidences of morbidity and mortality. Anaesthetics is an area of particular interest in this field, with previous research leading to better informed practice, specifically with regards to pseudocholinesterase deficiency and malignant hyperthermia. In this review, recent pharmacogenetic data pertaining to anaesthetic drugs will be presented and possible future applications and implications for practice will be discussed.

•

Pharmacogenetic variations in anaesthetic drugs affect enzymes, transport proteins and drug receptors.

•

Genotyping may provide more clues as to aetiology of conditions related to usage of anaesthetic drugs e.g. propofol infusion syndrome.

•

Improved and more economical molecular technology will lead to increase in quantity of pharmacogenetic data.