Pharmacogenetics in perioperative medicine

Precision, integrative medicine for pain management in sickle cell disease

Sickle cell disease (SCD) is a prevalent and complex inherited pain disorder that can manifest as acute vaso-occlusive crises (VOC) and/or chronic pain. Despite their known risks, opioids are often prescribed routinely and indiscriminately in managing SCD pain, because it is so often severe and debilitating. Integrative medicine strategies, particularly non-opioid therapies, hold promise in safe and effective management of SCD pain. However, the lack of evidence-based methods for managing SCD pain hinders the widespread implementation of non-opioid therapies. In this review, we acknowledge that implementing personalized pain treatment strategies in SCD, which is a guideline-recommended strategy, is currently fraught with limitations. The full implementation of pharmacological and biobehavioral pain approaches targeting mechanistic pain pathways faces challenges due to limited knowledge and limited financial and personnel support. We recommend personalized medicine, pharmacogenomics, and integrative medicine as aspirational strategies for improving pain care in SCD. As an organizing model that is a comprehensive framework for classifying pain subphenotypes and mechanisms in SCD, and for guiding selection of specific strategies, we present evidence updating pain research pioneer Richard Melzack's neuromatrix theory of pain. We advocate for using the updated neuromatrix model to subphenotype individuals with SCD, to better select personalized multimodal treatment strategies, and to identify research gaps fruitful for exploration. We present a fairly complete list of currently used pharmacologic and non-pharmacologic SCD pain therapies, classified by their mechanism of action and by their hypothesized targets in the updated neuromatrix model.

Residency Education Reform Program in Department of Anesthesiology and Critical Care: An Academic Reform Model

Background

Reform in medical education is a basic process in every academic department, especially in residency programs.

Objectives

This study was designed to assess the indices of education and research as part of the Medical Education Reform program (MERP) in the Department of Anesthesiology and Critical Care (DACC), Shahid Beheshti University of Medical Sciences (SBMU) for four years.

Methods

MERP in DACC, SBMU was designed and implemented as a modern academic reform model; different outcome measures in education and research were assessed to demonstrate the effects of the reform plan in academic improvements.

Results

there were significant improvements regarding education indices (i.e., teaching methods, passing comprehensive exams, mentorship, assessment methods, faculty development, professionalism in medical education, integration in education, and crisis management) and research indices (targeted research activities, innovation in research approaches, increasing the impact of research).

Conclusions

Based on the experiences of DACC, SBMU regarding clinical anesthesiology residency, reform could be achieved using painstaking plans and continuous efforts with tangible documented outcomes. Often, the management period is not durable, and these reforms require meticulous care to sustain.

Preventing complications in dermatologic surgery: Presurgical concerns

Cutaneous surgery has become critical to comprehensive dermatologic care, and dermatologists must therefore be equipped to manage the risks associated with surgical procedures. Complications may occur at any point along the continuum of care, and therefore assessing, managing, and preventing risk from beginning to end becomes essential. This review focuses on preventing surgical complications pre- and postoperatively as well as during the surgical procedure.

Pharmacogenomics, concepts for the future of perioperative medicine and pain management: A review

Pharmacogenomics is the study of how genetic differences between individuals affect pharmacokinetics and pharmacodynamics. These differences are apparent to clinicians when taking into account the wide range of responses to medications given in clinical practice. A review of literature involving pharmacogenomics and pain management was performed. The implementation of preoperative pharmacogenomics will allow us to better care for our patients by delivering personalized, safer medicine. This review describes the current state of pharmacogenomics as it relates to many aspects of clinical practice and how clinicians can use these tools to improve patient outcomes.

Precision Medicine in Acute Brain Injury: A Narrative Review

Over the past few years, the concept of personalized medicine has percolated into the management of different neurological conditions. Improving outcomes after acute brain injury (ABI) continues to be a major challenge. Unrecognized individual multiomic variations in addition to multiple interacting processes may explain why we fail to observe comprehensive improvements in ABI outcomes even when applied treatments appear to be beneficial logically. The provision of clinical care based on a multiomic approach may revolutionize the management of traumatic brain injury, delayed cerebral ischemia after subarachnoid hemorrhage, acute ischemic stroke, and several other neurological diseases. The challenge is to incorporate all the information obtained from genomic studies, other omic data, and individual variability into a practical tool that can be used to assist clinical decision-making. The effective execution of such strategies, which is still far away, requires the development of protocols on the basis of these complex interactions and strict adherence to management protocols. In this review, we will discuss various omics and physiological targets to guide individualized patient management after ABI.

Pharmacogenomics of Pain Management: The Impact of Specific Biological Polymorphisms on Drugs and Metabolism

PURPOSE OF REVIEW

Pain is multifactorial and complex, often with a genetic component. Pharmacogenomics is a relative new field, which allows for the development of a truly unique and personalized therapeutic approach in the treatment of pain.

RECENT FINDINGS

Until recently, drug mechanisms in humans were determined by testing that drug in a population and calculating response averages. However, some patients will inevitably fall outside of those averages, and it is nearly impossible to predict who those outliers might be. Pharmacogenetics considers a patient's unique genetic information and allows for anticipation of that individual's response to medication. Pharmacogenomic testing is steadily making progress in the management of pain by being able to identify individual differences in the perception of pain and susceptibility and sensitivity to drugs based on genetic markers. This has a huge potential to increase efficacy and reduce the incidence of iatrogenic drug dependence and addiction. The streamlining of relevant polymorphisms of genes encoding receptors, transporters, and drug-metabolizing enzymes influencing the pain phenotype can be an important guide to develop safe new strategies and approaches to personalized pain management. Additionally, some challenges still prevail and preclude adoption of pharmacogenomic testing universally. These include lack of knowledge about pharmacogenomic testing, inadequate standardization of the process of data handling, questionable benefits about the clinical and financial aspects of pharmacogenomic testing-guided therapy, discrepancies in clinical evidence supporting these tests, and doubtful reimbursement of the tests by health insurance agencies.

Challenges in anesthesia personalization: resolving the pharmacogenomic puzzle

Clinicians are witnessing differences in the doses required for induction and maintenance of anesthesia, as well as prolonged recovery in some patients. Predictable factors like patient characteristics, factors related to the procedure, pharmacological characteristics of anesthetics and adjunctive drugs, might explain some of the observed differences. However, the role of various polymorphisms of genes encoding for drugs’ molecular targets, transporters and metabolic enzymes can have a significant impact on anesthesia outcome, too. In the present paper, we critically discuss pharmacological characteristics of the most common drugs used in anesthesia, with a focus on the possible genetic background of unpredictable diversities in anesthesia outcomes.

Potential role of pharmacogenomics testing in the setting of enhanced recovery pathways after surgery

In 2001, a group of European academic surgeons created the Enhanced Recovery After Surgery (ERAS) study group and established the first official ERAS protocol. One of the most significant challenges during ERAS implementation is variability of drugs used throughout the perioperative period. Pharmacogenomic testing (blood or saliva) results (obtained within approximately 48 hrs) provide guidelines on how to prescribe the optimal drug with the optimal dosage to each patient based on an individual's unique genetic profile. Pharmacogenomic testing of various methods of multimodal analgesia is an essential element of ERAS protocols spanning the entire perioperative period to ultimately optimize postoperative pain control. The key goal for anesthetic management in ERAS protocols is to facilitate rapid emergence by using the shortest acting agents available, thus accelerating recovery and reducing length of stay, hospital expenses, and postoperative complications. Postoperative nausea and vomiting (PONV) is an additional challenge that should be overcome to ensure an enhanced recovery and shorter length of stay with the use of antiemetics. Postoperative ileus (POI) can result in longer hospital stay with increasing susceptibility to associated morbidities along with an increase in associated hospitalization costs. Genetics-guided pharmacotherapy and its impact on clinical outcomes should be thoroughly studied for better understanding and managing drug administration in the settings of ERAS.

Update on the pharmacogenomics of pain management

Pharmacogenomics is the study of genetic variants that impact drug effects through changes in a drug’s pharmacokinetics and pharmacodynamics. Pharmacogenomics is being integrated into clinical pain management practice because variants in individual genes can be predictive of how a patient may respond to a drug treatment. Pain is subjective and is considered challenging to treat. Furthermore, pain patients do not respond to treatments in the same way, which makes it hard to issue a consistent treatment regimen for all pain conditions. Pharmacogenomics would bring consistency to the subjective nature of pain and could revolutionize the field of pain management by providing personalized medical care tailored to each patient based on their gene variants. Additionally, pharmacogenomics offers a solution to the opioid crisis by identifying potentially opioid-vulnerable patients who could be recommended a nonopioid treatment for their pain condition. The integration of pharmacogenomics into clinical practice creates better and safer healthcare practices for patients. In this article, we provide a comprehensive history of pharmacogenomics and pain management, and focus on up to date information on the pharmacogenomics of pain management, describing genes involved in pain, genes that may reduce or guard against pain and discuss specific pain management drugs and their genetic correlations.

Genomics Testing and Personalized Medicine in the Preoperative Setting

Pharmacogenomics (PGx) is the study of how individuals' personal genotypes may affect their responses to various pharmacologic agents. The application of PGx principles in perioperative medicine is fairly novel. Challenges in executing PGx programs into health care systems include physician buy-in and integration into usual clinical workflow, including the electronic health record. This article discusses the current evidence highlighting the potential of PGx with various drug categories (including opioids, nonopioid analgesics, sedatives, β-blockers, antiemetics, and anticoagulants) used in the perioperative process and the challenges of integrating PGx into a health care system and relevant workflows.

Clinical and pharmacogenetics associated with recovery time from general anesthesia

AIM

Delayed recovery from general anesthesia is a well-known complication that requires predictive tools and approaches. This study aimed to determine significant factors associated with postanesthesia recovery and to develop an algorithm for estimating recovery time from general anesthesia.

MATERIALS & METHODS

The genotypes of patients were determined by SNaPshot or ARMS-qPCR. The algorithm was developed via machine-learning and tested by the worm plot.

RESULTS

Results showed that OPRM1 rs1799971 (p = 0.006) and ABCG2 rs2231142 (p = 0.041) were significantly associated with recovery time. Ten factors after random forest and stepwise selection were associated with recovery time. Ten factors after random forest and stepwise selection were associated with recovery time. Meanwhile, seven factors were associated with delayed recovery.

CONCLUSION

This study demonstrated that both clinical and pharmacogenetic data are significantly associated with recovery from general anesthesia and provide the basis for pre-emptive prediction tools.

Codeine and opioid metabolism: implications and alternatives for pediatric pain management

PURPOSE OF REVIEW

Use of perioperative opioids for surgical pain management of children presents clinical challenges because of concerns of serious adverse effects including life-threatening respiratory depression. This is especially true for children with history of obstructive sleep apnea. This review will explore current knowledge of clinically relevant factors and genetic polymorphisms that affect opioid metabolism and postoperative outcomes in children.

RECENT FINDINGS

Within the past several years, an increasing number of case reports have illustrated clinically important respiratory depression, anoxic brain injuries and even death among children receiving appropriate weight-based dosages of codeine and other opioids for analgesia at home setting particularly following tonsillectomy. Several national and international organizations have issued advisories on use of codeine in pediatrics, based on cytochrome P450 family 2 subfamily D type 6 (CYP2D6) pharmacogenetics. We have discussed the pros and cons of alternatives to codeine for pain management.

SUMMARY

Although routine preoperative genotyping to identify children at risk and personalized opioid use for pediatric perioperative pain management is still a distant reality, current known implications of CYP2D6 pharmacogenetics on codeine use shows that pharmacogenetics has the potential to guide anesthesia providers on perioperative opioid selection and dosing to maximize efficacy and safety.

The pharmacogenetics of medications used in general anesthesia

General anesthesia is a state of unconsciousness, amnesia, analgesia and akinesia induced by drugs including opioids, hypnotic-sedative agents, muscle relaxants and antiemetics. Clinical and genetic factors are reported to influence the efficacy and side effects of these agents. Based on the evidence, clinical action is needed to improve clinical outcomes. This review summarizes the latest knowledge with regards to the pharmacogenetics of anesthetics and general anesthesia related complications.

Pharmacogenomics in Anesthesia

A significant number of commonly administered medications in anesthesia show wide clinical interpatient variability. Some of these include neuromuscular blockers, opioids, local anesthetics, and inhalation anesthetics. Individual genetic makeup may account for and predict cardiovascular outcomes after cardiac surgery. These interactions can manifest at any point in the perioperative period and may also only affect a specific system. A better understanding of pharmacogenomics will allow for more individually tailored anesthetics and may ultimately lead to better outcomes, decreased hospital stays, and improved patient satisfaction.

Prospective observational pharmacogenetic study of side effects induced by intravenous morphine for postoperative analgesia

Nausea and vomiting are probably the most unpleasant side effects that occur when morphine used. A number of studies have investigated the effect on pain relief of single nucleotide polymorphisms (SNPs) in genes involved in morphine's metabolism, distribution, binding, and cellular action. The mechanism through which morphine causes nausea and vomiting has not been elucidated clearly. We examined all the reported SNPs which are associated with the complications of morphine, including SNPs in genes for phase I and phase II metabolic enzymes, ABC binding cassette drug transporters, κ and δ opioid receptors, and ion channels implicated in the postreceptor action of morphine.A prospective, observational study in 129 female patients was conducted to investigate the effect of 14 SNPs on nausea or vomiting induced by intravenous patient-controlled analgesia (IVPCA) with morphine after gynecology surgery. Clinical phenotype, subjective complaints, and objective observations were recorded. DNA from blood samples was used to record the SNPs. Eleven SNPs were then analyzed further.No significant association with the presence of phenotype (nausea or vomiting) versus genotype was observed (all P > .05). No significant association with severity of phenotype versus genotype of the 11 SNPs was observed except for unadjusted data for rs2737703.There was no significant difference between severity or incidence of IVPCA morphine-induced nausea and vomiting and genotype (11 SNPs). Further study should perhaps be focused on mRNA and proteinomics rather than SNPs.

CYP2D6 pharmacogenetic and oxycodone pharmacokinetic association study in pediatric surgical patients

AIM

Oxycodone is partly metabolized to the active metabolite oxymorphone by hepatic CYP2D6 in the liver. Significant genetic variability in CYP2D6 activity affects oxymorphone formation. This study aimed to associate CYP2D6 genotype and oxycodone's metabolism.

METHODS

30 children were administered oral oxycodone postoperatively. Plasma levels of oxycodone and oxymorphone, and CYP2D6 genotype were analyzed. CYP2D6 genotype and oxycodone metabolism phenotype were determined based on CYP2D6 total activity score (TAS) and metabolism phenotype: poor metabolizer (PM), intermediate metabolizer (IM), extensive metabolizer (EM) or ultrarapid metabolizer (UM).

RESULTS

Compared with PM/IM subjects, significantly greater oxymorphone exposure was seen in EM subjects (p = 0.02 for C_max, p = 0.016 for AUC_0-6 and p = 0.026 for AUC_0-24). Similarly, higher TAS value was found to be associated with greater oxymorphone exposure. Higher conversion of oxycodone to oxymorphone was observed in EM subjects compared with PM/IM subjects (p = 0.0007 for C_max, p = 0.001 for AUC_0-6 and p = 0.004 for AUC_0-24).

CONCLUSION

CYP2D6 phenotypes explain metabolism of oxycodone in children, and oxymorphone exposure is higher in CYP2D6 EM phenotype. Further studies are needed to predict the occurrence of adverse event and tailor oxycodone dose for a specific CYP2D6 phenotype.

The pharmacogenomics of pain management: prospects for personalized medicine

Pain is a common symptom that can be complex to treat. Analgesic medications are the mainstay treatment, but there is wide interindividual variability in analgesic response and adverse effects. Pharmacogenomics is the study of inherited genetic traits that result in these individual responses to drugs. This narrative review will attempt to cover the current understanding of the pharmacogenomics of pain, examining common genes affecting metabolism of analgesic medications, their distribution throughout the body, and end organ effects.

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.

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

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

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

Considerations when using pharmacokinetic/pharmacodynamic modeling to determine the effectiveness of simple analgesics in children

INTRODUCTION

Assessment of analgesic drugs includes comparative studies to other analgesics and local anesthesia blockade, number needed to treat estimates and opioid sparing descriptions. An additional methodology is to define the concentration-response relationship using pharmacokinetic/pharmacodynamic (PK/PD) modeling.

AREAS COVERED

A concentration-response relationship allows analgesic effect comparison between drugs for different acute pain types. Covariates such as size, age and organ function impact greatly on PK in children. The cumulative effect of confounding factors (e.g., pharmacogenetics, placebo and changes in baseline pain over time) complicates PD. Other factors (outcome measures, method of measurement, failure to account for study attrition) impact on outcome. Population PK/PD modeling approaches allow us to account for these various factors to some extent.

EXPERT OPINION

Nonlinear mixed effects models help interpret analgesic data and their use is increasing. The PK is relatively well understood. The next investigative step will involve investigation into covariate effects for PD. Mathematical functions for both placebo models and dropout models are well described and should be incorporated into analgesic effectiveness studies that investigate a range of doses. Improvements in pain assessment tools and a greater understanding of pharmacogenomics factors will help individualize analgesic therapy.

ABCC3 and OCT1 genotypes influence pharmacokinetics of morphine in children

AIM

Large interindividual variability in morphine pharmacokinetics could contribute to variability in morphine analgesia and adverse events.

METHODS

Influence of weight, genetic polymorphisms, race and sex on morphine clearance and metabolite formation from 220 children undergoing outpatient adenotonsillectomy was studied. A nonlinear mixed effects model was developed in NONMEM to describe morphine and morphine glucuronide pharmacokinetics.

RESULTS

Children with ABCC3 -211C>T polymorphism C/C genotype had significantly higher levels of morphine-6-glucuronide and morphine-3-glucuronide formation (∼40%) than C/T+T/T genotypes (p < 0.05). In this extended cohort similar to our earlier report, OCT1 homozygous genotypes (n = 13, OCT1*2-*5/*2-*5) had lower morphine clearance (14%; p = 0.06), and in addition complementing lower metabolite formation (∼39%) was observed. ABCB1 3435C>T TT genotype children had lower levels of morphine-3-glucuronide formation though no effect was observed on morphine and morphine-6-glucuronide pharmacokinetics.

CONCLUSION

Our data suggest that besides bodyweight, OCT1 and ABCC3 genotypes play a significant role in the pharmacokinetics of intravenous morphine and its metabolites in children.

Additives to local anesthetics for peripheral nerve blocks or local anesthesia: a review of the literature

SUMMARY 

A multitude of studies have focused on individual additives to local anesthetics and their effect on quality, onset, duration, spread and selectivity, as well as the potential toxic effects of their use. This review aims to give a broad overview of the current evidence in this developing field, based on beneficial and adverse effects of these drugs. We discuss the limitations of the available data and hope to convey implications and future perspectives for clinicians and researchers alike.

Future of pediatric tonsillectomy and perioperative outcomes

OBJECTIVE

Although commonly performed, pediatric tonsillectomy is not necessarily a low risk procedure due to potentially life threatening perioperative complications. There is paucity of literature on lethal anesthesia and surgical complications of tonsillectomy. In this article, we have reviewed both minor and serious complications following tonsillectomy. Hemorrhage, burn injuries, respiratory complications, postoperative nausea and vomiting, and pain management are discussed. We have highlighted our practice of pain management at Cincinnati Children's Hospital after tonsillectomy recent warning about codeine by the FDA on children undergoing tonsillectomy. We describe post-tonsillectomy outcomes including postanesthesia care unit stay, post discharge maladaptive behavioral outcomes and finally effective ways to identify children at risk for anesthesia and a few preventive strategies.

METHODS

In addition to literature review, the LexisNexis "MEGA™ Jury Verdicts and Settlements" database was reviewed from 1984 through 2010 for deaths and complications during and following tonsillectomy. Data including year of case, cause of death, surgical, anesthetic and postoperative opioid related complications, injury, case result, and judgment awarded were collected and analyzed.

RESULTS

The results of this analysis are presented with an emphasis on hemorrhage and on anesthesia and opioid related claims and their characteristics. Two hundred and thirty-three claim reports were reviewed. There were 96 deaths (41%) and 137 perioperative injuries (59%). Deaths were primarily related to surgery (n=46, 48%) with post-tonsillectomy bleed the most frequent cause (n=38, 40%) followed by opioid toxicity (n=17, 18%) and anesthesia complications (n=9, 9%). Non-fatal injuries included, postoperative bleeding (n=59, 25%), impaired function (n=29, 12%), anoxic events (n=20, 9%) and postoperative opioid toxicity (n=20, 8.6%). Anoxic event was noted to have the highest monetary award with a mean award at $9,017,379. Injuries (including anoxia) had higher mean monetary awards than deaths.

CONCLUSION

Tonsillectomy in children carries a high risk of perioperative complications and malpractice claims. Though postoperative bleeding is the most common complication associated with malpractice claims, anoxia related to anesthesia and opioids had the greatest overall risk from a monetary standpoint.