Fentanyl-induced chest wall rigidity

A case of opioid-induced rigidity requiring naloxone administration at the time of anesthesia emergence

BACKGROUND

Opioid-induced rigidity is typically observed during rapid administration of fentanyl. Herein, we present a case in which rigidity occurred after reversal of rocuronium during emergence from anesthesia.

CASE PRESENTATION

A 73-year-old man underwent video-assisted partial lung resection. General anesthesia was induced with propofol, remimazolam, remifentanil, and rocuronium. Fentanyl was administered early during anesthesia. The surgery was completed without complications, and sugammadex sodium was administered for rocuronium reversal. The patient became agitated, but spontaneous breathing was maintained; therefore, the intratracheal tube was removed after the administration of flumazenil. The patient developed stiffness in the neck and jaw muscles along with remarkable skeletal muscle contractions. Dramatic improvement was observed immediately after administration of naloxone.

CONCLUSIONS

Even as the simulated effect site concentration of fentanyl decreases during anesthesia emergence, opioid-induced rigidity may still occur. Rapid reversal of remimazolam by flumazenil might have contributed to the rigidity in this case.

Clinical Pharmacokinetics and Pharmacodynamics of Naloxone

Naloxone is a World Health Organization (WHO)-listed essential medicine and is the first choice for treating the respiratory depression of opioids, also by lay-people witnessing an opioid overdose. Naloxone acts by competitive displacement of opioid agonists at the μ-opioid receptor (MOR). Its effect depends on pharmacological characteristics of the opioid agonist, such as dissociation rate from the MOR receptor and constitution of the victim. Aim of treatment is a balancing act between restoration of respiration (not consciousness) and avoidance of withdrawal, achieved by titration to response after initial doses of 0.4-2 mg. Naloxone is rapidly eliminated [half-life (t1/2) 60-120 min] due to high clearance. Metabolites are inactive. Major routes for administration are intravenous, intramuscular, and intranasal, the latter primarily for take-home naloxone. Nasal bioavailability is about 50%. Nasal uptake [mean time to maximum concentration (Tmax) 15-30 min] is likely slower than intramuscular, as reversal of respiration lag behind intramuscular naloxone in overdose victims. The intraindividual, interindividual and between-study variability in pharmacokinetics in volunteers are large. Variability in the target population is unknown. The duration of action of 1 mg intravenous (IV) is 2 h, possibly longer by intramuscular and intranasal administration. Initial parenteral doses of 0.4-0.8 mg are usually sufficient to restore breathing after heroin overdose. Fentanyl overdoses likely require higher doses of naloxone. Controlled clinical trials are feasible in opioid overdose but are absent in cohorts with synthetic opioids. Modeling studies provide valuable insight in pharmacotherapy but cannot replace clinical trials. Laypeople should always have access to at least two dose kits for their interim intervention.

Comparison of the effects of fentanyls and other μ opioid receptor agonists on the electrical activity of respiratory muscles in the rat

Introduction: Deaths due to overdose of fentanyls result primarily from depression of respiration. These potent opioids can also produce muscle rigidity in the diaphragm and the chest muscles, a phenomenon known as Wooden Chest Syndrome, which further limits ventilation. Methods: We have compared the depression of ventilation by fentanyl and morphine by directly measuring their ability to induce muscle rigidity using EMG recording from diaphragm and external and internal intercostal muscles, in the rat working heart-brainstem preparation. Results: At equipotent bradypnea-inducing concentrations fentanyl produced a greater increase in expiratory EMG amplitude than morphine in all three muscles examined. In order to understand whether this effect of fentanyl was a unique property of the phenylpiperidine chemical structure, or due to fentanyl's high agonist intrinsic efficacy or its lipophilicity, we compared a variety of agonists with different properties at concentrations that were equipotent at producing bradypnea. We compared carfentanil and alfentanil (phenylpiperidines with relatively high efficacy and high to medium lipophilicity, respectively), norbuprenorphine (orvinolmorphinan with high efficacy and lipophilicity) and levorphanol (morphinan with relatively low efficacy and high lipophilicity). Discussion: We observed that, agonists with higher intrinsic efficacy were more likely to increase expiratory EMG amplitude (i.e., produce chest rigidity) than agonists with lower efficacy. Whereas lipophilicity and chemical structure did not appear to correlate with the ability to induce chest rigidity.

Effects of sub-lethal doses of fentanyl on vital physiologic functions and withdrawal-like behaviors in adult goats

Synthetic opioids like fentanyl have improved the standard of care for many patients in the clinical setting, but their abuse leads to tens of thousands of overdose deaths annually. The current opioid epidemic underscores a critical need for insights into the physiological effects of fentanyl on vital functions. High doses of opioids in small mammals cause opioid-induced respiratory depression (OIRD) leading to hypoventilation, hypoxemia, and hypercapnia. In addition, opioids can also increase the alveolar to arterial oxygen (A-a) gradient and airway dysfunction. However, little is known about the physiologic effects of sub-lethal doses of opioids in large mammals. Here we report the effects of a sub-lethal dose range of fentanyl (25-125 μg/kg; IV) on vital physiologic functions over 90 min (min) and withdrawal-like behaviors over the subsequent 4 h (h) in adult female goats (n = 13). Fentanyl induced decreases in breathing frequency in the first few min post-injection, but then led to a sustained increase in tidal volume, total ventilation, and blood pressure with a reduced heart rate for ≥90 min. These ventilatory changes resulted in time-dependent arterial hypocapnia and hypoxemia and an increased alveolar to arterial oxygen gradient ∼30 min post-injection indicative of impaired gas exchange in the lung. The predominant effects of fentanyl on breathing were stimulatory, underscored by an increased rate of rise of the diaphragm muscle activity and increased activation of upper airway, intercostal and abdominal muscles. Beginning 90 min post-injection we also quantified withdrawal-like behaviors over 4 h, demonstrating dose- and time-dependent increases in locomotor, biting, itching, and pawing behaviors. We conclude that fentanyl at sublethal doses induces multiple physiologic and behavior changes that emerge along different time courses suggesting multiple independent mechanisms underlying effects of opioids.

The anomalous pharmacology of fentanyl

Fentanyl is a key therapeutic, used in anaesthesia and pain management. It is also increasingly used illicitly and is responsible for a large and growing number of opioid overdose deaths, especially in North America. A number of factors have been suggested to contribute to fentanyl's lethality, including rapid onset of action, in vivo potency, ligand bias, induction of muscle rigidity and reduced sensitivity to reversal by naloxone. Some of these factors can be considered to represent 'anomalous' pharmacological properties of fentanyl when compared with prototypical opioid agonists such as morphine. In this review, we examine the nature of fentanyl's 'anomalous' properties, to determine whether there is really a pharmacological basis to support the existence of such properties, and also discuss whether such properties are likely to contribute to overdose deaths involving fentanyls. LINKED ARTICLES: This article is part of a themed issue on Advances in Opioid Pharmacology at the Time of the Opioid Epidemic. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v180.7/issuetoc.

Fentanyl-Induced Rigid Chest Syndrome in Critically Ill Patients

BACKGROUND

Opioid induced chest wall rigidity was first described in the early 1950s during surgical anesthesia and has often been referred to as fentanyl induced rigid chest syndrome (FIRCS). It has most commonly been described in the setting of procedural sedation and bronchoscopy, characterized by pronounced abdominal and thoracic rigidity, asynchronous ventilation, and respiratory failure. FIRCS has been infrequently described in the setting of continuous analgesia in critically ill adult patients. We postulate that FIRCS can occur in this setting and is likely under recognized, leading to increased morbidity and mortality.

METHODS

Patients admitted to the intensive care unit with suspected FIRCS were included in this retrospective analysis. The objective of this analysis is to describe the clinical presentation and treatment strategies for FIRCS.

RESULTS

Forty-two patients exhibiting symptoms of FIRCS were included in this analysis. Twenty-two of the forty-two patients with descriptive documentation had evidence of thoracic or abdominal rigidity on examination (52.4%). Twelve of sixteen (75%) patients treated solely with naloxone had documented ventilator compliance following intervention, compared to six of eleven (55%) managed with cisatracurium alone. Nine of twelve patients who ultimately received naloxone after initial treatment with cisatracurium had documented ventilator compliance following naloxone administration (75%). Standard interventions, including sedation optimization and ventilator adjustments were attempted to rule out and treat other potential causes of dyssynchrony. In most cases, the administration of naloxone resulted in appropriate compliance with both ventilator and patient-initiated breaths, suggesting the ventilator dyssynchrony was due to fentanyl.

CONCLUSIONS

This is the largest case series to date describing FIRCS in the intensive care setting. Recognition and prompt management is necessary for improved patient outcomes. Research is needed to increase awareness and recognition, identify patient risk factors, and analyze the efficacy and safety of interventions.

Fentanyl-induced muscle rigidity in a dog during weaning from mechanical ventilation after emergency abdominal surgery: A case report

A 22.5-kg, 8.4-year-old female mixed breed dog was presented for an emergency ovariohysterectomy for pyometra. No neurological abnormalities were observed on preoperative physical examination. Surgery was completed uneventfully under fentanyl- and sevoflurane-based anaesthesia. Cardiorespiratory indices remained stable under mechanical ventilation throughout the procedure. Approximately 23 min after the discontinuation of fentanyl infusion, the investigator noticed jaw closure and stiffness and thoraco-abdominal muscle rigidity. To rule out fentanyl-induced muscle rigidity, naloxone was administered. Following administration of naloxone, there was a return of spontaneous respiratory effort, indicated by capnogram and visible chest wall excursion. Based on the clinical signs and response to naloxone administration, the dog was diagnosed with suspected fentanyl-induced muscle rigidity. Six minutes after the return of spontaneous respiration, the dog was extubated uneventfully without additional naloxone administration. During 4 days of postoperative hospitalization, no recurrent muscle rigidity was observed, and the patient was discharged safely. The total dose of fentanyl administered was 0.61 mg (27 μg kg^-1 ).

In vitro and in vivo pharmaco-dynamic study of the novel fentanyl derivatives: Acrylfentanyl, Ocfentanyl and Furanylfentanyl

Fentanyl derivatives (FENS) belongs to the class of Novel Synthetic Opioids that emerged in the illegal drug market of New Psychoactive Substances (NPS). These substances have been implicated in many cases of intoxication and death with overdose worldwide. Therefore, the aim of this study is to investigate the pharmaco-dynamic profiles of three fentanyl (FENT) analogues: Acrylfentanyl (ACRYLF), Ocfentanyl (OCF) and Furanylfentanyl (FUF). In vitro, we measured FENS opioid receptor efficacy, potency, and selectivity in calcium mobilization studies performed in cells coexpressing opioid receptors and chimeric G proteins and their capability to promote the interaction of the mu receptor with G protein and β-arrestin 2 in bioluminescence resonance energy transfer (BRET) studies. In vivo, we investigated the acute effects of the systemic administration of ACRYLF, OCF and FUF (0.01-15 mg/kg i.p.) on mechanical and thermal analgesia, motor impairment, grip strength and cardiorespiratory changes in CD-1 male mice. Opioid receptor specificity was investigated in vivo using naloxone (NLX; 6 mg/kg i.p) pre-treatment. In vitro, the three FENS were able to activate the mu opioid receptor in a concentration dependent manner with following rank order potency: FUF > FENT=OCF > ACRYLF. All compounds were able to elicit maximal effects similar to that of dermorphin, with the exception of FUF which displayed lower maximal effects thus behaving as a partial agonist. In the BRET G-protein assay, all compounds behaved as partial agonists for the β-arrestin 2 pathway in comparison with dermorphin, whereas FUF did not promote β-arrestin 2 recruitment, behaving as an antagonist. In vivo, all the compounds increased mechanical and thermal analgesia with following rank order potency ACRYLF = FENT > FUF > OCF and impaired motor and cardiorespiratory parameters. Among the substances tested, FUF showed lower potency for cardiorespiratory and motor effects. These findings reveal the risks associated with the use of FENS and the importance of studying the pharmaco-dynamic properties of these drugs to better understand possible therapeutic interventions in the case of toxicity.

Pharmacokinetic considerations for community-based dosing of nasal naloxone in opioid overdose in adults

INTRODUCTION

The administration of the opioid antagonist naloxone in the community is a measure to prevent death from opioid overdose. Approved nasal naloxone sprays deliver initial doses of 0.9 to 8 mg. The level of the initial community dose is controversial, as the scientific base is weak.In this review knowledge of the pharmacokinetics of nasal, both approved and improvised nasal sprays, and intramuscular naloxone will be utilized to evaluate dose-effect relationships in previous studies of opioid overdose outcomes.

AREAS COVERED

The aim was to present scientifically based considerations on the initial nasal naloxone doses currently available, which reasonably balances the effect and adverse outcomes, given that at least two doses are at hand. Also included in these considerations is the challenge by illicitly manufactured fentanyl and analogs.This paper is based on both peer-reviewed and grey literature identified by several searches, of such as naloxone pharmacokinetics/formulations/outcomes/emergency medical services, in PubMed and Embase.

EXPERT OPINION

There is little scientific evidence that supports the use of initial systemic dosing that exceeds 0.8 mg in the community. Higher doses increase the risk of withdrawal symptoms feared in people who use opioids. Many obstacles may reduce the potential of community-administered naloxone.

Treatment of opioid overdose: current approaches and recent advances

BACKGROUND

The USA has recently entered the third decade of the opioid epidemic. Opioid overdose deaths reached a new record of over 74,000 in a 12-month period ending April 2021. Naloxone is the primary opioid overdose reversal agent, but concern has been raised that naloxone is not efficacious against the pervasive illicit high potency opioids (i.e., fentanyl and fentanyl analogs).

METHODS

This narrative review provides a brief overview of naloxone, including its history and pharmacology, and the evidence regarding naloxone efficacy against fentanyl and fentanyl analogs. We also highlight current advances in overdose treatments and technologies that have been tested in humans.

RESULTS AND CONCLUSIONS

The argument that naloxone is not efficacious against fentanyl and fentanyl analogs rests on case studies, retrospective analyses of community outbreaks, pharmacokinetics, and pharmacodynamics. No well-controlled studies have been conducted to test this argument, and the current literature provides limited evidence to suggest that naloxone is ineffective against fentanyl or fentanyl analog overdose. Rather a central concern for treating fentanyl/fentanyl analog overdose is the rapidity of overdose onset and the narrow window for treatment. It is also difficult to determine if other non-opioid substances are contributing to a drug overdose, for which naloxone is not an effective treatment. Alternative pharmacological approaches that are currently being studied in humans include other opioid receptor antagonists (e.g., nalmefene), respiratory stimulants, and buprenorphine. None of these approaches target polysubstance overdose and only one novel approach (a wearable naloxone delivery device) would address the narrow treatment window.

Case report: Intrapulmonary tidal volumes in a preterm infant with chest wall rigidity

BACKGROUND

Chest wall rigidity is a known side effect of fentanyl use, which is why fentanyl is usually combined with a muscle relaxant such as mivacurium. Verifying endotracheal intubation is difficult in case of a rigid chest wall.

CASE PRESENTATION

We present the case of a preterm infant (29 completed weeks gestation, birth weight 1,150 g) with a prolonged chest wall rigidity after fentanyl administration for intubation despite adequate doses of mivacurium. This resulted in a pronounced desaturation without any effect on heart rate. Clinically, the infant showed no chest wall movement despite intubation and common tools to verify intubation (including end-tidal carbon dioxide measurement and auscultation) were inconclusive. However, using electrical impedance tomography (EIT), we were able to demonstrate minimal tidal volumes at lung level and thereby, EIT was able to accurately show correct placement of the endotracheal tube.

CONCLUSIONS

This case may increase vigilance for fentanyl-induced chest wall rigidity in the neonatal population even when simultaneously administering mivacurium. Higher airway pressures exceeding 30 mmHg and the use of μ-receptor antagonists such as naloxone should be considered to reverse opioid-induced chest wall rigidity. Most importantly, our data may imply a relevant clinical benefit of using EIT during neonatal intubation as it may accurately show correct endotracheal tube placement.

In Vitro and In Vivo Analysis of Fentanyl and Fentalog Metabolites using Hyphenated Chromatographic Techniques: A Review

Fentanyl and fentanyl analogues (also called fentalogs) are used as medical prescriptions to treat pain for a long time. Apart from their pharmaceutical applications, they are misused immensely, causing the opioid crisis. Fentanyl and its analogues are produced in clandestine laboratories and sold over dark Web markets to different parts of the world, leading to a rise in the death rate due to drug overdose. This is because the users are unaware of the lethal effects of the newer forms of fentalogs. Unlike other drugs, these fentalogs cannot be detected easily, as very little data are available, and this is one of the major reasons for the risk of life-threatening poisoning or deaths. Hence, rigorous studies of these drugs and their possible metabolites are required. It is also necessary to develop techniques for the detection of minute traces of metabolites in biological fluids. This Review provides an overview of the application of hyphenated chromatographic techniques used to analyze multiple novel fentalogs, using in vivo and in vitro methods. The article focuses on the metabolites formed in phase I and phase II processes in biological specimens obtained in recent cases of drug abuse and overdose deaths that could be useful for the detection and differentiation of multiple fentalogs.

[Overdose from a patch]

HISTORY AND CLINICAL FINDINGS

We present the case of an 89-year-old patient with impaired consciousness for whom the emergency services were called. She was soporose and showed a pronounced generalized muscle rigidity. Due to a third-party history the incorrect use of a fentanyl patch was found out to be at cause.

TREATMENT AND CLINICAL COURSE

The antidote administration of naloxone led to restoration. The need for repetitive administration confirmed the clinical hypothesis.

CONCLUSION

The application of fentanyl via the skin in the form of transdermal therapeutic systems (TTS) has become more popular over the years. Incorrect administration causes intoxication with the leading symptoms of loss of consciousness and respiratory depression. This case report extends the spectrum of symptoms to include skeletal muscle rigidity otherwise only described in connection with intravenous administration, especially in anaesthetic settings.

Wooden Chest Syndrome: A Case Report of Fentanyl-Induced Chest Wall Rigidity

Wooden chest syndrome (WCS) describes a finding of fentanyl-induced skeletal muscle rigidity causing ventilatory failure. Known primarily to anesthesiology, pulmonary, and critical care fields, WCS is a rare complication that may affect patients of all ages if exposed to intravenous fentanyl, characterized by a patient’s inability to properly ventilate. Given the rise of synthetic opioid deaths across the United States in the past decade, an understanding of all of fentanyl’s effects on the body is necessary. In this article, we present a case of WCS in a patient with acute respiratory distress syndrome in a 61-year-old female.

Wooden Chest syndrome: The atypical pharmacology of fentanyl overdose

WHAT IS KNOWN AND OBJECTIVE

A large percentage of opioid overdose fatalities involve fentanyl or one of its legal or illegal analogs (F/FAs). Is there something about the pharmacology of these drugs that make them unusually dangerous in an overdose?

COMMENT

Some of the reasons for the dangers of overdose of F/FAs is their high potency and low cost (that leads to wide distribution). But it is rarely asked if the basic pharmacology of F/FAs differ in some fundamental way from conventional opioids such as morphine and heroin. In addition to centrally mediated respiratory depression via opioid receptors, F/FAs cause rigidity in the key respiratory muscles of the chest, upper airway and diaphragm ("wooden chest syndrome," WCS) by a non-opioid mechanism.

WHAT IS NEW AND CONCLUSION

WCS is an atypical pharmacology of F/FAs. Because of its rapid onset and non-opioid mechanism, WCS makes F/FA overdose particularly dangerous.

Current State of Analgesia and Sedation in the Pediatric Intensive Care Unit

Critically ill pediatric patients often require complex medical procedures as well as invasive testing and monitoring which tend to be painful and anxiety-provoking, necessitating the provision of analgesia and sedation to reduce stress response. Achieving the optimal combination of adequate analgesia and appropriate sedation can be quite challenging in a patient population with a wide spectrum of ages, sizes, and developmental stages. The added complexities of critical illness in the pediatric population such as evolving pathophysiology, impaired organ function, as well as altered pharmacodynamics and pharmacokinetics must be considered. Undersedation leaves patients at risk of physical and psychological stress which may have significant long term consequences. Oversedation, on the other hand, leaves the patient at risk of needing prolonged respiratory, specifically mechanical ventilator, support, prolonged ICU stay and hospital admission, and higher risk of untoward effects of analgosedative agents. Both undersedation and oversedation put critically ill pediatric patients at high risk of developing PICU-acquired complications (PACs) like delirium, withdrawal syndrome, neuromuscular atrophy and weakness, post-traumatic stress disorder, and poor rehabilitation. Optimal analgesia and sedation is dependent on continuous patient assessment with appropriately validated tools that help guide the titration of analgosedative agents to effect. Bundled interventions that emphasize minimizing benzodiazepines, screening for delirium frequently, avoiding physical and chemical restraints thereby allowing for greater mobility, and promoting adequate and proper sleep will disrupt the PICU culture of immobility and reduce the incidence of PACs.

Neuronal mechanisms underlying opioid-induced respiratory depression: our current understanding

Opioid-induced respiratory depression (OIRD) represents the primary cause of death associated with therapeutic and recreational opioid use. Within the United States, the rate of death from opioid abuse since the early 1990s has grown disproportionally, prompting the classification as a nationwide "epidemic." Since this time, we have begun to unravel many fundamental cellular and systems-level mechanisms associated with opioid-related death. However, factors such as individual vulnerability, neuromodulatory compensation, and redundancy of opioid effects across central and peripheral nervous systems have created a barrier to a concise, integrative view of OIRD. Within this review, we bring together multiple perspectives in the field of OIRD to create an overarching viewpoint of what we know, and where we view this essential topic of research going forward into the future.

Anesthesia Considerations in Neurological Emergencies

Airway obstruction and respiratory failure are common complications of neurological emergencies. Anesthesia is often employed for airway management, surgical and endovascular interventions or in the intensive care units in patients with altered mental status or those requiring burst suppression. This article provides a summary of the unique airway management and anesthesia considerations and controversies for neurologic emergencies in general, as well as for specific commonly encountered conditions: elevated intracranial pressure, neuromuscular respiratory failure, acute ischemic stroke, and acute cervical spinal cord injury.

Pain and dyspnea control during awake fiberoptic bronchoscopy in critically ill patients: safety and efficacy of remifentanil target-controlled infusion

Purpose

Flexible fiberoptic bronchoscopy is frequently used in intensive care unit, but is a source of discomfort, dyspnea and anxiety for patients. Our objective was to assess the feasibility and tolerance of a sedation using remifentanil target-controlled infusion, to perform fiberoptic bronchoscopy in awake ICU patients.

Materials, patients and methods

This monocentric, prospective observational study was conducted in awake patients requiring fiberoptic bronchoscopy. In accordance with usual practices in our center, remifentanil target-controlled infusion was used under close monitoring and adapted to the patient’s reactions. The primary objective was the rate of successful procedures without additional analgesia or anesthesia. The secondary objectives were clinical tolerance and the comfort of patients (graded from “very uncomfortable” to “very comfortable”) and operators (numeric scale from 0 to 10) during the procedure.

Results

From May 2014 to December 2015, 72 patients were included. Most of them (69%) were hypoxemic and admitted for acute respiratory failure. No additional medication was needed in 96% of the patients. No severe side-effects occurred. Seventy-eight percent of patients described the procedure as “comfortable or very comfortable”. Physicians rated their comfort with a median [IQR] score of 9 [8–10].

Conclusion

Remifentanil target-controlled infusion administered to perform awake fiberoptic bronchoscopy in critically ill patients is feasible without requirement of additional analgesics or sedative drugs. Clinical tolerance as well as patients’ and operators’ comfort were good to excellent. This technique could benefit patients’ experience.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13613-021-00832-6.

Causes, Nature and Toxicology of Fentanyl-Associated Deaths: A Systematic Review of Deaths Reported in Peer-Reviewed Literature

PURPOSE

Fentanyl poisoning has been widely reported, yet there is a lack of systematic evaluation of the nature and toxicology of associated deaths in the published literature. This article aims to systematically review the nature, causes, routes of administration and toxicology of fentanyl-associated deaths using case studies and case series in peer-reviewed published literature.

METHODS

Four electronic databases including Embase, Medline (via Ovid), Scopus and Google Scholar were searched from inception until October 2019 to identify the studies reporting fentanyl related deaths. Two independent reviewers screened and selected the titles and then evaluated the full texts. Only case studies and case series were included. A structured data extraction tool was used to extract data on the number of deaths, routes of administration, concomitant drug use and toxicological data. The Joanna Briggs Institute quality assessment tool was used to evaluate the quality of included studies. Data were synthesized narratively.

RESULTS

Of 1251 articles identified during initial search, 8 case reports and 9 case series met the inclusion criteria. A total of 1969 deaths were reported in the included studies. Deaths were concentrated in the north American region (n = 1946) and the Nordic region (n = 22). Reported causes of death included fentanyl overdose (n = 321, 56.4%), mixed drug toxicity (n = 196, 34.5%), natural (n = 28, 4.9%), other drug toxicity (n = 10, 1.8%), fentanyl and ethanol intoxication (n = 8, 1.4%), incidental (n = 5, <1%) and aspiration (n = 1). Most common routes of use were intravenous (70.5%) and transdermal routes (23.0%). Deaths came swiftly via the intravenous route. Mean level of blood fentanyl amongst all reported deaths was 0.024 µg/mL.

CONCLUSION

Literature related to fentanyl-associated deaths predominantly come from North America. Deaths are comparatively lower or not reported in peer-reviewed publications from the rest of the world. Abuse through intravenous administration, mixed drug toxicities and self-treatment of breakthrough pain are mainly responsible for majority of the reported deaths.

Sedation, Analgesia, and Paralysis in COVID-19 Patients in the Setting of Drug Shortages

The rapid spread of the severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) has led to a global pandemic. The 2019 coronavirus disease (COVID-19) presents with a spectrum of symptoms ranging from mild to critical illness requiring intensive care unit (ICU) admission. Acute respiratory distress syndrome is a major complication in patients with severe COVID-19 disease. Currently, there are no recognized pharmacological therapies for COVID-19. However, a large number of COVID-19 patients require respiratory support, with a high percentage requiring invasive ventilation. The rapid spread of the infection has led to a surge in the rate of hospitalizations and ICU admissions, which created a challenge to public health, research, and medical communities. The high demand for several therapies, including sedatives, analgesics, and paralytics, that are often utilized in the care of COVID-19 patients requiring mechanical ventilation, has created pressure on the supply chain resulting in shortages in these critical medications. This has led clinicians to develop conservation strategies and explore alternative therapies for sedation, analgesia, and paralysis in COVID-19 patients. Several of these alternative approaches have demonstrated acceptable levels of sedation, analgesia, and paralysis in different settings but they are not commonly used in the ICU. Additionally, they have unique pharmaceutical properties, limitations, and adverse effects. This narrative review summarizes the literature on alternative drug therapies for the management of sedation, analgesia, and paralysis in COVID-19 patients. Also, this document serves as a resource for clinicians in current and future respiratory illness pandemics in the setting of drug shortages.

Objective Characterization of Opiate-Induced Chest Wall Rigidity

Introduction

Opiate-induced chest wall rigidity is a syndrome that largely goes unrecognized. To date, no study has presented significant objective data to better understand this syndrome.

Objective

The aim of this study was to explore the correlation between the dosage of opiates and the incidence of chest wall rigidity, ventilatory changes, and effects of naloxone administration.

Methods

A total of eight patients were identified as having episodes of chest wall rigidity, with half of the population being females, with an average age of 54.8 ± 9 years. Physiological changes, ventilator data, vitals, and opiate dosage prior to chest wall rigidity episodes and after reversal with naloxone administration were analyzed using the Wilcoxon rank sum test for statistical significance.

Results

Significant changes were observed in dynamic wall compliance without positive end-expiratory pressure (PEEP) (pre-median=5.13; post-median=52.03; p=0.0078), dynamic wall compliance with PEEP (pre-median=6.13; post-median=72.36; p=0.0078), tidal volume (pre-median=110.5; post-median=1006; p=0.0078), and ventilator airflow (pre-median=0; post-median=75; p=0.0078). However, no statistically significant changes were detected in end tidal CO₂ (pre-median=36; post-median=37.5; p=0.4219), respiratory rate (pre-median=9; post-median=10.5; p=0.7188), or peak airway pressure (pre-median=17; post-median=21.5; p=0.4063). Additionally, there is a statistically significant correlation between morphine equivalent potency dosing within 24 hours and the change in tidal volume (r=0.8237; p=0.0439).

Conclusions

Our study is the first to demonstrate significant objective data on the ventilatory responses seen with opiate-induced chest wall rigidity. These findings may assist clinicians in better understanding the presentation and management of chest wall rigidity.

Calabadion 1 selectively reverses respiratory and central nervous system effects of fentanyl in a rat model

BACKGROUND

We hypothesised that Calabadion 1, an acyclic cucurbit[n]uril molecular container, reverses fentanyl-induced respiratory depression and dysfunction of the CNS.

METHODS

Experiments were conducted in male Sprague-Dawley rats. A constant-rate i.v. infusion of fentanyl (12.5 or 25 μg kg^-1 over 15 min) was administered followed by an i.v. bolus of Calabadion 1 (0.5-200 mg kg^-1) or placebo. The primary outcome was reversal of ventilatory and respiratory depression, assessed by pneumotachography and arterial blood gas analysis, respectively. Key secondary outcomes were effects on fentanyl-induced central nervous dysfunction quantified by righting reflex, balance beam test, and electromyography (EMG).

RESULTS

Calabadion 1 reversed fentanyl-induced respiratory depression across the endpoints minute ventilation, pH, and Paco₂ (P=0.001). Compared with placebo, Calabadion 1 dose dependently (P for trend <0.001) reversed fentanyl-induced hypoventilation {81.9 [5.1] (mean [standard error of the mean]) vs 45.5 [12.4] ml min^-1; P<0.001}, acidosis (pH 7.43 [0.01] vs 7.28 [0.04]; P=0.005), and hypercarbia (Paco₂ 43.4 [1.6] vs 63.4 [8.1] mm Hg; P=0.018). The effective Calabadion 1 doses required to reverse respiratory depression by 50% and 90% (ED50_Res and ED90_Res) were 1.7 and 15.6 mg kg^-1, respectively. Higher effective doses were needed for recovery of righting reflex (ED50_CNS: 9.6 mg kg^-1; ED90_CNS: 86.1 mg kg^-1), which was accelerated by Calabadion 1 (4.6 [0.3] vs 9.0 [0.7] min; P<0.001). Calabadion 1 also significantly accelerated recovery of full functional mobility and reversal of muscle rigidity.

CONCLUSIONS

Calabadion 1 selectively and dose dependently reversed the respiratory system and CNS side-effects of fentanyl.

Take-Home Naloxone for the Emergency Interim Management of Opioid Overdose: The Public Health Application of an Emergency Medicine

Naloxone is a well-established essential medicine for the treatment of life-threatening heroin/opioid overdose in emergency medicine. Over two decades, the concept of 'take-home naloxone' has evolved, comprising pre-provision of an emergency supply to laypersons likely to witness an opioid overdose (e.g. peers and family members of people who use opioids as well as non-medical personnel), with the recommendation to administer the naloxone to the overdose victim as interim care while awaiting an ambulance. There is an urgent need for more widespread naloxone access considering the growing problem of opioid overdose deaths, accounting for more than 100,000 deaths worldwide annually. Rises in mortality are particularly sharp in North America, where the ongoing prescription opioid problem is now overlaid with a rapid growth in overdose deaths from heroin and illicit fentanyl. Using opioids alone is dangerous, and the mortality risk is clustered at certain times and contexts, including on prison release and discharge from hospital and residential care. The provision of take-home naloxone has required the introduction of new legislation and new naloxone products. These include pre-filled syringes and auto-injectors and, crucially, new concentrated nasal sprays (four formulations recently approved in different countries) with speed of onset comparable to intramuscular naloxone and relative bioavailability of approximately 40-50%. Choosing the right naloxone dose in the fentanyl era is a matter of ongoing debate, but the safety margin of the approved nasal sprays is superior to improvised nasal kits. New legislation in different countries permits over-the-counter sales or other prescription-free methods of provision. However, access remains uneven with take-home naloxone still not provided in many countries and communities, and with ongoing barriers contributing to implementation inertia. Take-home naloxone is an important component of the response to the global overdose problem, but greater commitment to implementation will be essential, alongside improved affordable products, if a greater impact is to be achieved.

Kölliker-Fuse/Parabrachial complex mu opioid receptors contribute to fentanyl-induced apnea and respiratory rate depression

Overdoses caused by the opioid agonist fentanyl have increased exponentially in recent years. Identifying mechanisms to counter progression to fatal respiratory apnea during opioid overdose is desirable, but difficult to study in vivo. The pontine Kölliker-Fuse/Parabrachial complex (KF/PB) provides respiratory drive and contains opioid-sensitive neurons. The contribution of the KF/PB complex to fentanyl-induced apnea was investigated using the in situ arterially perfused preparation of rat. Systemic application of fentanyl resulted in concentration-dependent respiratory disturbances. At low concentrations, respiratory rate slowed and subsequently transitioned to an apneustic-like, 2-phase pattern. Higher concentrations caused prolonged apnea, interrupted by occasional apneustic-like bursts. Application of CTAP, a selective mu opioid receptor antagonist, directly into the KF/PB complex reversed and prevented fentanyl-induced apnea by increasing the frequency of apneustic-like bursting. These results demonstrate that countering opioid effects in the KF/PB complex is sufficient to restore phasic respiratory output at a rate similar to pre-fentanyl conditions, which could be beneficial in opioid overdose.

Noradrenergic Mechanisms in Fentanyl-Mediated Rapid Death Explain Failure of Naloxone in the Opioid Crisis

In December 2018, the Centers for Disease Control declared fentanyl the deadliest drug in America. Opioid overdose is the single greatest cause of death in the United States adult population (ages 18-50), and fentanyl and its analogs [fentanyl/fentanyl analogs (F/FAs)] are currently involved in >50% of these deaths. Anesthesiologists in the United States were introduced to fentanyl in the early 1970s when it revolutionized surgical anesthesia by combining profound analgesia with hemodynamic stability. However, they quickly had to master its unique side effect. F/FAs can produce profound rigidity in the diaphragm, chest wall and upper airway within an extremely narrow dosing range. This clinical effect was called wooden chest syndrome (WCS) by anesthesiologists and is not commonly known outside of anesthesiology or to clinicians or researchers in addiction research/medicine. WCS is almost routinely fatal without expert airway management. This review provides relevant clinical human pharmacology and animal data demonstrating that the significant increase in the number of F/FA-induced deaths may involve α-adrenergic and cholinergic receptor-mediated mechanical failure of the respiratory and cardiovascular systems with rapid development of rigidity and airway closure. Although morphine and its prodrug, heroin, can cause mild rigidity in abdominal muscles at high doses, neither presents with the distinct and rapid respiratory failure seen with F/FA-induced WCS, separating F/FA overdose from the slower onset of respiratory depression caused by morphine-derived alkaloids. This distinction has significant consequences for the design and implementation of new pharmacologic strategies to effectively prevent F/FA-induced death. SIGNIFICANCE STATEMENT: Deaths from fentanyl and F/FAs are increasing in spite of availability and awareness of the opioid reversal drug naloxone. This article reviews literature suggesting that naloxone may be ineffective against centrally mediated noradrenergic and cholinergic effects of F/FAs, which clinically manifest as severe muscle rigidity and airway compromise (e.g., wooden chest syndrome) that is rapid and distinct from respiratory depression seen with morphine-derived alkaloids. A physiologic model is proposed and implications for new drug development and treatment are discussed.

Fentanyl-Induced Chest Wall Rigidity as a Cause of Acute Respiratory Failure in the Intensive Care Unit

We aim to report a case of chest wall rigidity induced by high-dose fentanyl infusion sedation and analgesia in the intensive care unit (ICU) for management of pneumonia and asthma. The patient is an 80-year-old woman, who presented to the hospital with complaints of fever and productive cough with yellowish expectoration of 2 days duration. She also had lethargy over the same time period and had sick contacts in the form of two daughters who both had recently recovered from a “flu-like” illness. She was known to have bronchial asthma treated with seretide 25/250 two puffs ON + PO monteleukast 10 mg ON, hypertension treated with PO losartan 50 mg BD, type 2 diabetes mellitus controlled with PO linagliptin 5 mg OM and a previous right thalamic ischemic stroke 5 years ago for which she was on PO clopidogrel 75 mg OM and PO simvastatin. She developed severe ventilator desynchrony characterized by dramatic sudden onset of severe hypercarbia, severely decreased pulmonary compliance and episodic breath holding. She was empirically treated for asthma exacerbation and treated with steroids, bronchodilators and manual ventilation but despite doing so during this episode the patient failed to respond. The patient was clinically evaluated and dynamic hyperinflation was excluded as a cause of the respiratory failure. There was no evidence of pneumothorax and worsening pneumonia. Considerations of insufficient sedation and analgesia led to deepening sedation and analgesia without good response. Ventilation was dramatically improved after small doses of neuromuscular relaxation. This cycle was repeated many times. The patient was kept on high-dose propofol and fentanyl, but there were repeated cycles of sudden persistent severe hypercarbia, severely decreased pulmonary compliance and episodic breath holding. Eventually a suspicion of fentanyl-induced chest wall rigidity was made after excluding causes of airway resistance and reduction in pulmonary compliance. Gradual reduction in fentanyl infusion was associated with a reduction of episodes of reduced lung compliance and improvement in ventilation. Fentanyl is often used for analgesia and sedation in the ICU. It has a good side effect profile but it is not without harm. High doses of fentanyl can lead to dramatic worsening of respiratory mechanics that may be life threatening. Fentanyl-induced chest wall rigidity is an important side effect that needs to be considered in the differential diagnosis of respiratory failure in the ICU.

Effect of Tramadol Pretreatment on Sufentanil-Induced Cough

PURPOSE

To investigate the effect of tramadol pretreatment on the incidence and severity of sufentanil-induced cough.

DESIGN

Randomized controlled trial.

METHODS

Adults of both genders (N = 304; 18 to 65 years old, American Society of Anesthesiologists physical status I to II), scheduled for elective surgery, were randomized into two groups (n = 152): intravenous administration of tramadol 1 mg/kg (group T) or normal saline (group C). Then sufentanil bolus 0.3 mcg/kg was administered intravenously in 5 seconds. The incidence and severity of cough were observed for 1 minute. Mean arterial pressure, heart rate, nausea, vomiting, and truncal rigidity during induction were also recorded.

FINDINGS

Patient characteristics were similar between the two groups. The incidence of cough was significantly lower in group T when compared with group C (7.9% vs 18.4%, P < .05); there were nine patients coughing severely in group C, whereas no severe cough occurred in group T (P < .05). The mean arterial pressure, heart rate, and incidences of other side effects were comparable between the two groups.

CONCLUSIONS

Pretreatment of intravenous tramadol 1 mg/kg could be a clinically effective intervention for attenuating sufentanil-induced cough.

Suspected involvement of fentanyl in prior overdoses and engagement in harm reduction practices among young adults who use drugs

Background: From 2011 to 2016, the United States has experienced a 55% increase in overall overdose deaths and a 260% increase in fatal fentanyl-related overdoses. Increasing engagement in harm reduction practices is essential to reducing the rate of fentanyl-related overdoses. This study sought to examine the uptake of harm reduction practices among young adults who reported recent drug use and who were recruited for a study to assess the utility and acceptability of rapid fentanyl test strips. Methods: Between May and October 2017, 93 young adults who reported drug use in the past 30 days were recruited through word of mouth, Internet advertising, and public canvasing. Participants completed an interviewer-administered survey that assessed participants' sociodemographic and behavioral characteristics, suspected fentanyl exposure, and overdose history. We assessed harm reduction practices and other correlates associated with experiencing a suspected fentanyl-related overdose. Results: Of 93 eligible participants, 36% (n = 34) reported ever having experienced an overdose, among whom 53% (n = 18) suspected having experienced a fentanyl-related overdose. Participants who had ever experienced a fentanyl-related overdose were more likely to keep naloxone nearby when using drugs compared with those who had never experienced an overdose and those who had experienced an overdose that they did not suspect was related to fentanyl (P < .001). Additionally, experiencing a suspected fentanyl-related overdose was associated with having previously administered naloxone to someone else experiencing an overdose (P < .001). Conclusion: Those who had experienced a suspected fentanyl-related overdose were more likely to carry and administer naloxone. Future overdose prevention interventions should involve persons who have experienced a suspected fentanyl overdose and/or responded to an overdose in order to develop harm reduction programs that meet the needs of those at risk of an overdose.

The effect of two doses of fentanyl on chest wall rigidity at equipotent doses of isoflurane in dogs

OBJECTIVE

To evaluate the effect of two doses of fentanyl upon chest wall rigidity of dogs anesthetized at equipotent doses of isoflurane [1.3 minimum alveolar concentration (MACISO) of each dose of fentanyl].

STUDY DESIGN

Prospective crossover randomized study.

ANIMALS

A group of eight male Beagle dogs, approximately 1 year old and weighing 12.1 ± 1.6 kg (mean ± standard deviation).

METHODS

The dogs were anesthetized with isoflurane and instrumented for the measurement of esophageal pressure (PESO), flow (V˙) and volume (V). Chest wall elastance (ECW) was estimated by multiple linear regression of the model. PESO(t) = V˙(t) × RCW + V(t) × ECW + EEPESO where t is time, RCW is chest wall resistance and EEPESO is end-expiratory PESO. Chest wall compliance (CCW) was calculated as 1/ECW and normalized to the body weight of each dog (mL cmH2O-1 kg-1). Anesthesia was maintained at 1.3 MACISO for at least 15 minutes and CCW recorded (CCW-ISO). The dogs were randomly assigned to the lower fentanyl dose [loading dose (33 μg kg-1) and infusion (0.2 μg kg-1 minute-1)] or the higher fentanyl dose [loading dose (102 μg kg-1) and infusion (0.8 μg kg-1 minute-1)]. After 60 minutes of fentanyl infusion, CCW was recorded for each dose (CCW-FENT). During fentanyl infusion, the dogs were maintained at equipotent doses of isoflurane (1.3 MACISO for each fentanyl dose). A two-way analysis of variance followed by a Bonferroni test was used to compare CCW-ISO and CCW-FENT in both treatments and CCW-FENT between treatments. A p value <0.05 was considered significant.

RESULTS

Neither of the fentanyl doses decreased CCW and there was no difference in CCW-FENT between doses.

CONCLUSIONS AND CLINICAL RELEVANCE

Fentanyl at the studied doses did not result in chest wall rigidity in dogs anesthetized with equipotent doses of isoflurane (1.3 MACISO).

Changing risk and presentation of overdose associated with consumption of street drugs at a supervised injection site in Vancouver, Canada

BACKGROUND

British Columbia is experiencing a public health emergency due to overdoses resulting from consumption of street drugs contaminated with fentanyl. While the risk of overdoses appears to be increasing, the overdose rate and severity of overdose presentations have yet to be quantified.

METHODS

Insite is a supervised injection site in Vancouver. Data from Insite's client database from January 2010 to June 2017 were used to calculate overdose rates as well as the proportion of overdoses involving rigidity and naloxone administration over time in order to estimate changes in the risk and severity of overdose resulting from changes in the local drug supply.

RESULTS

The overdose rate increased significantly for all drug categories. Heroin used alone or with other drugs continues to be associated with the highest overdose rate. The overdose rate associated with heroin increased from 2.7/1000 visits to 13/1000 visits over the study period, meaning that clients were 4.8 times more likely to overdose in the most recent period as in the baseline period. The proportion of overdose events involving rigidity, a known complication of intravenous fentanyl use, increased significantly from 10.4% to 18.9%. The proportion of overdoses requiring naloxone administration increased significantly from 48.4% to 57.1% and is now similar across all drug categories.

CONCLUSIONS

The risk and severity of overdoses at Insite have increased since the emergence of illicit fentanyl. This information derived from supervised injection site data can be used to inform local harm reduction efforts and the response to the overdose emergency.

Carfentanil: a narrative review of its pharmacology and public health concerns

Carfentanil is a synthetic fentanyl analogue approved for veterinary use. It is a mu-opioid receptor agonist with an estimated analgesic potency approximately 10,000 times that of morphine and 20-30 times that of fentanyl, based on animal studies. Since 2016, an increasing number of reports describe detection of carfentanil in the illicit drug supply. Little is known about the pharmacology of carfentanil in humans. Its high potency and presumed high lipophilicity, large volume of distribution, and potential active metabolites have raised concerns about the management of people exposed to carfentanil as well as the safety of first responders. Exposed individuals exhibit features of an opioid toxidrome and respond to opioid antagonists such as naloxone, although empiric dose requirements are unknown and very high doses may be required. Rare reports of suspected accidental poisoning of first responders have not been analytically confirmed and are unlikely to represent true poisoning. General occupational hygiene measures, including regular decontamination with soap and water, basic personal protective equipment (nitrile gloves, N95 mask, and eye goggles), and ready access to naloxone are generally sufficient in most circumstances.

Understanding Symptoms of Muscle Tightness, Weakness, and Rigidity From a Nursing Perspective

PURPOSE

This study examined the nature of muscle tightness from nurses' perspectives and explored how the symptoms of muscle tightness are communicated, managed, and differentiated from other conditions, such as muscle rigidity and muscle weakness.

DESIGN

An exploratory, descriptive qualitative design was used.

METHODS

Eight rehabilitation nurses described lexicons, care strategies, and communication for muscle tightness, weakness, and rigidity.

FINDINGS

Nurses used conflicting terms to describe muscle tightness, weakness, and rigidity. They identified medications and range of motion as the best strategies to manage muscle conditions. Nurses approach care holistically and do not differentiate care strategies that are based only on a symptoms lens.

CONCLUSIONS

Nurses were unable to clearly differentiate between muscle tightness and rigidity.

CLINICAL RELEVANCE

Nurses influence patients' choice of vocabulary; therefore, they must use simple but precise terminologies to educate their patients. Miscommunication between nurses and patients can lead to errors, which can have negative consequences.

Rigidity, dyskinesia and other atypical overdose presentations observed at a supervised injection site, Vancouver, Canada

Objective

In midst of the overdose crisis, the clinical features of opioid overdoses seem to be changing. Understanding of the adverse effects of synthetic opioids such as fentanyl is currently limited to clinical settings. Insite, a supervised injection site in Vancouver, Canada, provides an opportunity to better understand illicit drug overdose presentations.

Methods

A review of clinical records at Insite for October 2016 to April 2017 was undertaken to quantify atypical overdose presentations. Overdose reports were reviewed for the number of atypical opioid overdose presentations, temporal trends over the study period, concurrent symptoms, and interventions employed by staff.

Results

Insite staff responded to 1581 overdoses during the study period, including 497 (31.4%) that did not fit a typical presentation for opioid overdoses. Of these, 485 fit into five categories of atypical features: muscle rigidity, dyskinesia, slow or irregular heart rate, confusion, and anisocoria. Muscle rigidity was the most common atypical presentation, observed in 240 (15.2%) of the overdose cases, followed by dyskinesia, observed in 150 (9.2%). Slow or irregular heart rate was observed in 69 (4.4%) cases, confusion in 24 (1.5%), and anisocoria in 2 (0.1%) of overall overdose cases.

Discussion

The similarity of atypical overdose cases at Insite with anesthesiology case reports supports the understanding that the illicit drug supply is contaminated by fentanyl and other synthetic opioids. Atypical overdose presentations can affect clinical overdose response. The experience at Insite highlights the potential for supervised consumption sites to be innovative spaces for community learning and knowledge translation.

Positive Pressure Ventilation in the Cardiac Intensive Care Unit

Contemporary cardiac intensive care units (CICUs) provide care for an aging and increasingly complex patient population. The medical complexity of this population is partly driven by an increased proportion of patients with respiratory failure needing noninvasive or invasive positive pressure ventilation (PPV). PPV often plays an important role in the management of patients with cardiogenic pulmonary edema, cardiogenic shock, or cardiac arrest, and those undergoing mechanical circulatory support. Noninvasive PPV, when appropriately applied to selected patients, may reduce the need for invasive mechanical PPV and improve survival. Invasive PPV can be lifesaving, but has both favorable and unfavorable interactions with left and right ventricular physiology and carries a risk of complications that influence CICU mortality. Effective implementation of PPV requires an understanding of the underlying cardiac and pulmonary pathophysiology. Cardiologists who practice in the CICU should be proficient with the indications, appropriate selection, potential cardiopulmonary interactions, and complications of PPV.

Premedication for Endotracheal Intubation in the Neonate

Endotracheal intubation, a common procedure in neonatal intensive care, results in distress and disturbs physiologic homeostasis in the newborn. Analgesics, sedatives, vagolytics, and/or muscle relaxants have the potential to blunt these adverse effects, reduce the duration of the procedure, and minimize the number of attempts necessary to intubate the neonate. The medical care team must understand efficacy, safety, and pharmacokinetic data for individual medications to select the optimal cocktail for each clinical situation. Although many units utilize morphine for analgesia, remifentanil has a superior pharmacokinetic profile and efficacy data. Because of hypotensive effects in preterm neonates, sedation with midazolam should be restricted to near-term and term neonates. A vagolytic, generally atropine, blunts bradycardia induced by vagal stimulation. A muscle relaxant improves procedural success when utilized by experienced practitioners; succinylcholine has an optimal pharmacokinetic profile, but potentially concerning adverse effects; rocuronium may be the agent of choice based on more robust safety data despite a relatively prolonged duration of action. In the absence of an absolute contraindication, neonates should receive analgesia with consideration of sedation, a vagolytic, and a muscle relaxant before endotracheal intubation. Neonatal units must develop protocols for premedication and optimize logistics to ensure safe and timely administration of appropriate agents.

Anaesthetic management of a patient with a unique combination of anti-N-methyl-D-aspartate receptor encephalitis and stiff-person syndrome

Stiff-person syndrome (SPS) and anti-N-methyl-D-aspartate receptor (NMDAR) encephalitis are rare paraneoplastic syndromes caused by antibodies that target the central nervous system. Here, we describe a 26-year-old woman who presented with psychosis, amnesia, rigidity and fever. After extensive diagnostic and laboratory workup, she was diagnosed with an ovarian teratoma which was causing the symptoms of anti-NMDAR encephalitis and SPS. The patient was successfully treated with laparoscopic removal of the ovarian tumour under general anaesthesia. She was placed on immunosuppressant medications preoperatively and postoperatively, and her symptoms gradually resolved. Although there are case reports regarding the anaesthetic management of SPS and anti-NMDAR encephalitis, our study is the first report of a patient afflicted with both conditions.

EVALUATION OF BLOOD GAS VALUES IN ANESTHETIZED SOUTHERN WHITE RHINOCEROS ( CERATOTHERIUM SIMUM) VENTILATED WITH A NOVEL DEMAND VENTILATOR IN A ZOOLOGICAL PARK SETTING

Rhinoceros conservation efforts are essential to the survival of the species. One such effort is focused on using advanced reproductive technologies to produce viable northern white rhinoceros ( Ceratotherium simum cottoni) embryos for implantation into southern white rhinoceros ( Ceratotherium simum simum) surrogates. Anesthesia may be required to facilitate necessary procedures in these surrogate rhinoceros, but commonly reported side effects including hypercapnia and hypoxemia limit anesthetic recumbency time due to animal safety concerns. Although many interventions have been attempted, success in improving these physiologic parameters to date is mixed. The objective of this report is to describe arterial pH (pHa), blood gas (PaO₂ and PaCO₂), bicarbonate, base excess, lactate, and cardiovascular (heart rate, direct arterial blood pressure) values recorded in seven intubated and ventilated female southern white rhinoceros anesthetized for reproductive examinations in a zoological park setting. Anesthetic induction was accomplished using etorphine, medetomidine, butorphanol, and midazolam. The primary hypotheses were that PaO₂ and PaCO₂ would improve after intubation and mechanical ventilation. Induction and recovery observations were also summarized. Physiologic and laboratory data were analyzed using a mixed linear regression model using ranks. Statistical significance was set at P < 0.05. The PaO₂ increased significantly ( P < 0.001) following ventilation from a median value of 58 (range, 38-67) to 123 (range, 42-184) mm Hg. The PaCO₂ significantly ( P = 0.003) decreased from 63 (range, 55-73) to 52 (range, 30-75) mm Hg, with a corresponding improvement ( P = 0.068) in pHa from 7.33 (7.25-7.34) to 7.37 (7.24-7.58) units. Intubation and ventilation improve respiratory parameters and may facilitate safe prolongation of anesthetic duration in white rhinoceros.

Sold as Heroin: Perceptions and Use of an Evolving Drug in Baltimore, MD

Since 2001, heroin-related overdose deaths in the United States have risen six-fold, a rise unaccounted for by the expanding user population. Has heroin become a more dangerous drug? Reports of fentanyl and its analogs, often concealed in or sold as heroin, have also increased sharply. This article investigates heroin injectors' perceptions and experiences of changes in the heroin supply in the East Coast city of Baltimore, Maryland, currently facing an epidemic in heroin- and fentanyl-related overdose deaths. Unusually, Baltimore's heroin market is divided between two types: "Raw," believed to be Colombian in origin and relatively pure, and the more adulterated "Scramble" (raw heroin traditionally blended with quinine and lactose). Users reported that Scramble heroin, while gaining market share, has become a highly unstable product, varying dramatically in appearance, intensity of onset, duration of action, and effect. Some considered that Scramble was no longer "heroin," but was heavily adulterated or even replaced, mentioning fentanyl, benzodiazepines, and crushed opioid pills as additives. There was intense awareness of overdose as a present danger in users' lives, which they linked to the recent adulteration of the heroin supply. Responses to this perceived adulteration varied, including information gathering, attraction, avoidance, taking precautions, and acceptance.

Hydromorphone Hydrochloride Use During Various Interventional Radiology Procedures-Pain Control and Adverse Events: A Case Series Audit Analysis

Introduction

This project studied pain control and the development of adverse events before, during, and after the administration of hydromorphone hydrochloride for various interventional radiology (IR) procedures.

Methods

We performed a retrospective analysis of 100 patients (men = 58; women = 42) sedated with peri-procedural intravenous (IV) hydromorphone in association with various IR procedures. We stratified the procedures as follows: abscess drainages (M = 8; F = 8), arteriograms (M = 1; F = 0), biliary interventions (M = 3; F = 2), bone biopsies (M = 2; F = 2), non-bone biopsies (M = 26; F = 19), non-tunneled venous catheters (M = 1; F = 1), tunneled venous catheters (M = 7; F = 5), embolization (M = 4; F = 0), IVC filter placement (M = 1; F = 1), nephrostomy tube placement (M = 1; F = 4), and percutaneous nephrolithotomy tube placements (M = 4; F = 0). We recorded the pre-, intra-, and post-procedure pain scores [numeric rating scale (NRS) with 0 = no pain to 10 = most pain] for each of the stratifications. We also recorded the total dose of hydromorphone and midazolam hydrochloride received by each gender, as well as whether any men or women received either naloxone hydrochloride or any antiemetic. Lastly, the investigators recorded the development of hypotension following hydromorphone administration and/or hypoxia as well as the need for opioid-induced intensive care unit (ICU) admission. The investigators used unpaired, two-tailed t tests, and either Yates-corrected Chi-squares or two-tailed Fisher’s exact tests for continuous and categorical variables, respectively. The difference was statistically significant if p < 0.05.

Results

There was no significant difference between men and women for either mean age (M = 50 years; F = 53.4 years) or mean pre-procedural pain scores (M = 1.31; F = 0.55). There was no statistically significant difference in numbers of men or women for each procedure stratification. The highest mean pre-procedure pain score was in men undergoing percutaneous nephrostomy tube placement (mean 5, SD 0). The highest mean intra-procedure pain score was in men undergoing abscess drainages (mean 2, SD 2.3). The highest mean post-procedure pain score was in men undergoing abscess drainages (mean 1.5, SD 3.5). The only mean scores that were significantly different between men and women were in pre- (M = 2.5; F = 0.6; p = 0.006) and intra-procedural (M = 2; F = 0.5; p = 0.0001) pain scores for abscess drainages. There was no statistically significant difference in the dose of either hydromorphone (M = 1.3; F = 1.3) or midazolam (M = 1.3; F = 1.3) administered. There was no statistically significant difference in opioid-induced nausea (M = 1; F = 3). One female experienced hypotension and one male experienced hypoxia within 6 h of hydromorphone administration. There were neither opioid-related ICU admissions nor naloxone administrations.

Conclusions

This preliminary study indicates that IV hydromorphone ± midazolam may be a safe and effective analgesic and sedative combination for adult patients undergoing IR procedures.

Electronic supplementary material

The online version of this article (doi:10.1007/s40122-017-0083-4) contains supplementary material, which is available to authorized users.

Heroin uncertainties: Exploring users' perceptions of fentanyl-adulterated and -substituted 'heroin'

BACKGROUND

The US is experiencing an unprecedented opioid overdose epidemic fostered in recent years by regional contamination of the heroin supply with the fentanyl family of synthetic opioids. Since 2011 opioid-related overdose deaths in the East Coast state of Massachusetts have more than tripled, with 75% of the 1374 deaths with an available toxicology positive for fentanyl. Fentanyl is 30-50X more potent than heroin and its presence makes heroin use more unpredictable. A rapid ethnographic assessment was undertaken to understand the perceptions and experiences of people who inject drugs sold as 'heroin' and to observe the drugs and their use.

METHODS

A team of ethnographers conducted research in northeast Massachusetts and Nashua, New Hampshire in June 2016, performing (n=38) qualitative interviews with persons who use heroin.

RESULTS

(1) The composition and appearance of heroin changed in the last four years; (2) heroin is cheaper and more widely available than before; and (3) heroin 'types' have proliferated with several products being sold as 'heroin'. These consisted of two types of heroin (alone), fentanyl (alone), and heroin-fentanyl combinations. In the absence of available toxicological information on retail-level heroin, our research noted a hierarchy of fentanyl discernment methods, with embodied effects considered most reliable in determining fentanyl's presence, followed by taste, solution appearance and powder color. This paper presents a new 'heroin' typology based on users' reports.

CONCLUSION

Massachusetts' heroin has new appearances and is widely adulterated by fentanyl. Persons who use heroin are trying to discern the substances sold as heroin and their preferences for each form vary. The heroin typology presented is inexact but can be validated by correlating users' discernment with drug toxicological testing. If validated, this typology would be a valuable harm reduction tool. Further research on adaptations to heroin adulteration could reduce risks of using heroin and synthetic opioid combinations.