Propylene Glycol–Associated Renal Toxicity from Lorazepam Infusion

Quantitative Investigation on Exposure to Potentially Harmful Excipients by Injection Drug Administration in Children Under 2 Years of Age and Analysis of Association with Adverse Events: A Single-Center, Retrospective Observational Study

INTRODUCTION

Potentially harmful excipients (PHEs) for children have been reported and the need for information collection has been advocated. However, studies on the actual occurrence of adverse events are limited. This study investigated the quantitative exposure of PHEs via injection and their association with adverse events in children under 2 years of age.

MATERIALS AND METHODS

As a single-center observational study, children aged 0-23 months received injectable drugs from April 1, 2018, to March 31, 2023 were included. Information on PHE exposure and adverse events after administration were extracted from medical records. Sodium benzoate, benzyl alcohol, ethanol, glycerol, lactose, polyethylene glycol paraben, polysorbate, propylene glycol, sorbitol, sucrose, sulfite, and thimerosal were selected as PHEs.

RESULTS AND DISCUSSION

6265 cases, 333,694 prescriptions, and 368 drugs (264 ingredients) were analyzed. The median age was 0.63 years (interquartile range [IQR] 0.1-1.1). 72,133 prescriptions, 132 drugs and 99 ingredients contained PHE; 2,961 cases exposed to PHE and 1825 cases exceeding permitted daily exposure. The drug with the highest number of exposure cases was hydroxyzine, and the highest number of prescriptions was heparin (both drugs contain benzyl alcohol). In association between adverse events and PHE exposure, higher doses in cases of adverse event occurrence were found in benzyl alcohol, glycerol, polyethylene glycol, and polysorbate exposed cases. Among thimerosal-exposed cases, "developmental delay" was more frequent in exposed cases, but the causal relationship was unknown. Further investigation is needed to clarify the relationship between adverse events and PHE exposure. Additionally, more precise information on PDE for pediatrics including neonates is necessary.

Considerations for deriving a safe intake of propylene glycol

The use of propylene glycol (PG) in food and other applications is widespread, and some estimates of dietary exposure to PG approach or exceed the Acceptable Daily Intake (ADI) of 25 mg/kg bw-day. The current ADI for PG applies a cumulative uncertainty factor of 100, which includes factors of 10 for both interspecies and intraspecies differences. Available toxicology studies and human data, however, indicate a plausible mode of action (MoA) that would support a chemical-specific adjustment factor (CSAF) of 1 for interspecies toxicodynamic differences, reducing the total uncertainty factor from 100 to 40. The MoA involves an increase in serum PG concentrations after metabolic saturation, leading to serum hyperosmolarity, which can ultimately cause hemolytic changes and red blood cell damage. Therefore, the species similarities in toxicodynamic response for this critical effect could support increasing the ADI from 25 to 62.5 mg/kg bw-day, applicable to both children and adults.

Safety and Efficacy of Propylene Glycol-Free Melphalan in Patients with AL Amyloidosis Undergoing Autologous Stem Cell Transplantation: Results of a Phase II Study

Patients with systemic light chain (AL) amyloidosis undergoing treatment with high-dose melphalan and autologous stem cell transplantation (HDM/SCT) may develop renal and cardiac toxicities potentially exacerbated by the co-solvent propylene glycol in conventional melphalan formulations. We investigated the safety and efficacy of propylene glycol-free melphalan (PGF-Mel) during HDM/SCT in patients with AL amyloidosis (ClinicalTrials.gov identifier NCT02994784). The primary objective of this phase II, open-label study was evaluation for renal dysfunction, new cardiac arrhythmias, and postural hypotension related to autonomic dysfunction. Secondary objectives included time to neutrophil and platelet engraftment, treatment-related mortality (TRM), overall hematologic response, organ response, and number of peritransplantation hospitalizations. Twenty-eight patients with AL amyloidosis enrolled, of whom 27 underwent HDM/SCT. PGF-Mel at 140 to 200 mg/m2 was administered i.v. in 2 equally divided doses. Patients were monitored for up to 30 days after the last administration of PGF-Mel to assess for treatment-related toxicity. Patients were followed for 12 months from the time of treatment with HDM/SCT for evaluation of hematologic and organ responses. Kaplan-Meier analysis was used to estimate progression-free survival. Two patients (7%) developed renal dysfunction, 5 (19%) experienced new cardiac arrhythmias, and 3 (11%) developed orthostatic hypotension. All patients achieved neutrophil and platelet engraftment, at a median of 10 days and 17 days post-HDM/SCT, respectively. TRM on day +100 was 0%. Peritransplantation hospitalization was required for 23 patients (85%). The most common nonhematologic adverse events were diarrhea (93%), fatigue (82%), and nausea (74%). At 6 months post-HDM/SCT, hematologic complete response or very good partial response occurred in 66% of the patients. At 12 months post-HDM/SCT, renal response occurred in 12 of 23 (52%) patients with renal involvement, and cardiac response occurred in 3 of 11 (27%) patients with evaluable cardiac involvement. Our data indicate that PGF-Mel is safe and efficacious as a high-dose conditioning regimen for autologous SCT in patients with AL amyloidosis.

Correlation of osmolal gap with measured concentrations of acetone, ethylene glycol, isopropanol, methanol, and propylene glycol in patients at an academic medical center

The ingestion of toxic alcohols including methanol, ethylene glycol, and isopropanol remains a significant public health problem. These compounds can cause central nervous system depression and, for methanol and ethylene glycol, organ damage from toxic metabolites. The presence of these compounds in serum/plasma can often be determined and monitored by measuring the osmolal gap (OG). However, other compounds originating from endogenous or exogenous sources, such as propylene glycol and acetone, can also increase the OG. Conversion factors can be used to estimate specific concentrations of acetone and toxic alcohols from OG. In this retrospective study, data were analyzed for 260 samples originating from 158 unique patients that had determination of both OG and concentrations for toxic alcohols at an academic medical center central laboratory. Specific analysis included gas chromatography (acetone, isopropanol, methanol, ethylene glycol, propylene glycol) and/or enzymatic assay (ethylene glycol). Many samples also contained ethanol. The data was grouped by type of ingestion. The present study analyzed the relationship between the OG calculated from measured plasma/serum osmolality and the OG estimated by applying conversion factors to measured concentrations of the different compounds. The correlations tend to be linear and vary by compound, with methanol and ethylene glycol having the highest R2 values of 0.93 and 0.95, respectively, consistent with other published studies. Higher variability was seen for the data for isopropanol and acetone. For each of the data subsets, the estimated toxic alcohol concentration calculated using conversion factors from OG tends to overestimate the actual concentration of the compound. Overall, the present study demonstrates the generally linear relationship between OG determined by osmolality and the OG estimated using measured concentrations of acetone and toxic alcohols.

What are the respiratory effects of e-cigarettes?

Electronic cigarettes (e-cigarettes) are alternative, non-combustible tobacco products that generate an inhalable aerosol containing nicotine, flavors, propylene glycol, and vegetable glycerin. Vaping is now a multibillion dollar industry that appeals to current smokers, former smokers, and young people who have never smoked. E-cigarettes reached the market without either extensive preclinical toxicology testing or long term safety trials that would be required of conventional therapeutics or medical devices. Their effectiveness as a smoking cessation intervention, their impact at a population level, and whether they are less harmful than combustible tobacco products are highly controversial. Here, we review the evidence on the effects of e-cigarettes on respiratory health. Studies show measurable adverse biologic effects on organ and cellular health in humans, in animals, and in vitro. The effects of e-cigarettes have similarities to and important differences from those of cigarettes. Decades of chronic smoking are needed for development of lung diseases such as lung cancer or chronic obstructive pulmonary disease, so the population effects of e-cigarette use may not be apparent until the middle of this century. We conclude that current knowledge of these effects is insufficient to determine whether the respiratory health effects of e-cigarette are less than those of combustible tobacco products.

Iatrogenic Propylene Glycol Intoxication Due to High-Dose Pentobarbital for Refractory Intracranial Hypertension: A Case Report

Propylene glycol is a rarely reported toxicity from high-dose administration of certain intravenous drugs, including lorazepam and pentobarbital. We present a case of iatrogenic propylene glycol toxicity secondary to a high-dose pentobarbital infusion for the treatment of refractory intracranial hypertension due to cerebral venous sinus thrombosis. The patient developed metabolic acidosis and acute kidney failure secondary to propylene glycol toxicity. After initiation of continuous renal replacement therapy, the patient's acute renal failure and lactic acidosis resolved. Using the Naranjo scale, this case received a score of 5, defining it as a "probable" adverse drug event. In patients who develop lactic acidosis and acute renal failure after initiation of high-dose pentobarbital, propylene glycol toxicity should be higher up in the differential diagnosis. Monitoring the serum osmolality while on pentobarbital could help provide valuable information to prevent iatrogenic propylene glycol toxicity.

Evaluating the adverse effects of melphalan formulations

INTRODUCTION

For multiple myeloma patients who respond to primary therapy, autologous hematopoietic stem cell transplant (HSCT) is considered standard of care with high-dose melphalan for transplant candidates. There are now two different melphalan formulations available, including a propylene glycol containing (PG-MEL) product and a propylene glycol-free (PG-free MEL) product. Although considered bioequivalent, there remains limited literature directly evaluating the adverse events between the two agents. We seek to assess the tolerability and severity of side effects between the two formulations in a real-life practice setting.

METHODS

A retrospective, descriptive analysis was conducted of multiple myeloma patients who received autologous stem cell conditioning with either melphalan formulation when dosed at 100 mg/m²/dose for two consecutive doses. The primary outcome was the assessment of tolerability and severity of side effects. Tolerability was split into four major categories including hematologic toxicity, gastrointestinal toxicity, renal toxicity, and highest recorded mucositis grade.

RESULTS

There were a total of 78 patients who received a melphalan preparation during the study. The median time to myeloablation and neutrophil engraftment was five and seven days post-HSCT, respectively, for all patients. Patients who received PG-free MEL were less likely to develop mucositis, with 22 (56%) reported highest grade 0, defined by World Health Organization oral toxicity scale, compared to those who received PG-MEL (33%), p = 0.04.

CONCLUSION

There were minimal differences in tolerability or side effects observed between PG-free MEL and PG-MEL. These data may assist in better understanding the anticipated adverse effects of a high-dose melphalan conditioning therapy.

Chronic E-Cigarette Exposure Alters the Human Bronchial Epithelial Proteome

RATIONALE

E-cigarettes vaporize propylene glycol/vegetable glycerin (PG/VG), nicotine, and flavorings. However, the long-term health effects of exposing lungs to vaped e-liquids are unknown.

OBJECTIVES

To determine the effects of chronic vaping on pulmonary epithelia.

METHODS

We performed research bronchoscopies on healthy nonsmokers, cigarette smokers, and e-cigarette users (vapers) and obtained bronchial brush biopsies and lavage samples from these subjects for proteomic investigation. We further employed in vitro and murine exposure models to support our human findings.

MEASUREMENTS AND MAIN RESULTS

Visual inspection by bronchoscopy revealed that vaper airways appeared friable and erythematous. Epithelial cells from biopsy samples revealed approximately 300 proteins that were differentially expressed in smoker and vaper airways, with only 78 proteins being commonly altered in both groups and 113 uniquely altered in vapers. For example, CYP1B1 (cytochrome P450 family 1 subfamily B member 1), MUC5AC (mucin 5 AC), and MUC4 levels were increased in vapers. Aerosolized PG/VG alone significantly increased MUC5AC protein in human airway epithelial cultures and in murine nasal epithelia in vivo. We also found that e-liquids rapidly entered cells and that PG/VG reduced membrane fluidity and impaired protein diffusion.

CONCLUSIONS

We conclude that chronic vaping exerts marked biological effects on the lung and that these effects may in part be mediated by the PG/VG base. These changes are likely not harmless and may have clinical implications for the development of chronic lung disease. Further studies will be required to determine the full extent of vaping on the lung.

Repurposing Valproate, Enteral Clonidine, and Phenobarbital for Comfort in Adult ICU Patients: A Literature Review with Practical Considerations

Provision of adequate sedation is a fundamental part of caring for critically ill patients. Propofol, dexmedetomidine, and benzodiazepines are the most commonly administered sedative medications for adult patients in the intensive care unit (ICU). These agents are limited by adverse effects, need for a monitored environment for safe administration, and lack of universal effectiveness. Increased interest has recently been expressed about repurposing older pharmacologic agents for patient comfort in the ICU. Valproate, enteral clonidine, and phenobarbital are three agents with increasing evidence supporting their use. Potential benefits associated with their utilization are cost minimization and safe administration after transition out of the ICU. This literature review describes the historical context, pharmacologic characteristics, supportive data, and practical considerations associated with the administration of these agents for comfort in critically ill adult patients.

Pharmacokinetics of High-Dose Propylene Glycol-Free Melphalan in Multiple Myeloma Patients Undergoing Autologous Hematopoietic Cell Transplantation

High-dose melphalan followed by autologous stem cell transplant (ASCT) is standard of care for eligible patients with multiple myeloma (MM). Evomela (propylene glycol-free melphalan HCl [PG-Free Mel]; Spectrum Pharmaceuticals, Irvine, CA) was approved by the US Food and Drug Administration as conditioning therapy for ASCT in MM in 2 daily 100-mg/m² doses for a total dose of 200 mg/m². In this phase II, open-label study PG-Free Mel (Evomela) conditioning was given at single dose of 200 mg/m² on day -2 pre-ASCT to establish pharmacokinetic (PK) parameters and safety. Twenty-four patients (median age, 64 years) were enrolled between August 2016 and February 2017. Myeloablation followed by successful neutrophil engraftment occurred at a median of 10 days in all patients. Peak melphalan concentration was observed at 10 minutes after infusion, whereas there was considerable variation in the maximum plasma concentration (C_max) and area under concentration time curve (AUC). Median C_max was 7380 ng/mL (interquartile range [IQR], 6522 to 8027). Similarly, median AUC was 533,552 ng/mL∙min (IQR, 450,850 to 662,936). PG-Free Mel had an acceptable safety profile regardless of the exposure, with no mortality and an overall response rate of 96% and a very good partial response rate of 75%. In conclusion, although PG-Free Mel at a single dose of 200 mg/m² was safe, considerable PK variability was observed with the highest quartile having an ~3-fold higher AUC than the first quartile, suggesting that strategies for higher targeted exposure could be explored in future trials to optimize clinical benefit.

Evaluation of e-liquid toxicity using an open-source high-throughput screening assay

The e-liquids used in electronic cigarettes (E-cigs) consist of propylene glycol (PG), vegetable glycerin (VG), nicotine, and chemical additives for flavoring. There are currently over 7,700 e-liquid flavors available, and while some have been tested for toxicity in the laboratory, most have not. Here, we developed a 3-phase, 384-well, plate-based, high-throughput screening (HTS) assay to rapidly triage and validate the toxicity of multiple e-liquids. Our data demonstrated that the PG/VG vehicle adversely affected cell viability and that a large number of e-liquids were more toxic than PG/VG. We also performed gas chromatography-mass spectrometry (GC-MS) analysis on all tested e-liquids. Subsequent nonmetric multidimensional scaling (NMDS) analysis revealed that e-liquids are an extremely heterogeneous group. Furthermore, these data indicated that (i) the more chemicals contained in an e-liquid, the more toxic it was likely to be and (ii) the presence of vanillin was associated with higher toxicity values. Further analysis of common constituents by electron ionization revealed that the concentration of cinnamaldehyde and vanillin, but not triacetin, correlated with toxicity. We have also developed a publicly available searchable website (www.eliquidinfo.org). Given the large numbers of available e-liquids, this website will serve as a resource to facilitate dissemination of this information. Our data suggest that an HTS approach to evaluate the toxicity of multiple e-liquids is feasible. Such an approach may serve as a roadmap to enable bodies such as the Food and Drug Administration (FDA) to better regulate e-liquid composition.

Pentobarbital-induced lactic acidosis following status epilepticus barbiturate coma

We present a rare case of pentobarbital infusion causing propylene glycol-induced lactic acidosis, during refractory status epilepticus treatment in a 66-year-old man without seizure history.

Assessing Propylene Glycol Toxicity in Alcohol Withdrawal Patients Receiving Intravenous Benzodiazepines: A One-Compartment Pharmacokinetic Model

BACKGROUND AND OBJECTIVES

While some case reports indicate that high doses of propylene glycol (PG) may result in metabolic acidosis, there has been no large-scale study that evaluated the risk of metabolic acidosis in patients receiving PG-containing benzodiazepines for acute alcohol withdrawal. This study was undertaken to evaluate the potential toxicity of PG in patients with acute alcohol withdrawal treated with intermittent intravenous bolus doses of diazepam and/or lorazepam.

METHODS

This is a retrospective case study using data collected from 18 randomly selected patients receiving one or both of these medications per a modified Clinical Institute Withdrawal Assessment for Alcohol (CIWA) Class 3 protocol. Plasma levels of PG were estimated using a one-compartment pharmacokinetic model.

RESULTS

Only two patients had an elevated anion gap compared to their baseline value with one also experiencing a significant increase in serum creatinine. No increases in serum osmolarity were noted. Analysis showed that the benzodiazepine dose received was a good predictor of the estimated PG concentration (r = 0.6), but was poorly correlated with the anion gap. No significant correlation was found with the creatinine clearance or serum creatinine. Patients receiving several daily doses were at higher risk of developing an anion gap (r = 0.33), but the estimated maximum PG concentration did not correlate with the anion gap or serum concentration.

CONCLUSION

It does not appear that intermittent bolus administration of intravenous benzodiazepines for alcohol withdrawal influenced renal function or anion gap regardless of number of administered doses, amount of PG received, or the estimated PG concentration.

Phase II Study of Propylene Glycol-Free Melphalan Combined with Carmustine, Etoposide, and Cytarabine for Myeloablative Conditioning in Lymphoma Patients Undergoing Autologous Stem Cell Transplantation

The lyophilized formulation of melphalan has several limitations based on its marginal solubility, limited stability after reconstitution, and the requirement to reconstitute it in propylene glycol (PG). PG-free melphalan (Evomela; Spectrum Pharmaceuticals, Irvine CA) overcomes these limitations by using the solubilizing agent Captisol (Ligand Pharmaceuticals, Inc., LaJolla CA) to improve the stability of the reconstituted melphalan and avoid the potential toxicities of PG. This phase II study investigated the safety and efficacy of high-dose PG-free melphalan when included in the carmustine, etoposide, and cytarabine (BEAM) regimen for adult patients with non-Hodgkin lymphoma (NHL) or Hodgkin lymphoma (HL). Carmustine, etoposide, and cytarabine were given at standard doses on day -6 through day -3. PG-free melphalan, 140 mg/m², was infused over 30 minutes on day -2. The primary endpoint was toxicity. Fifty patients (33 NHL/17 HL) completed BEAM with PG-free melphalan and stem cell infusion. The most common grades 3 to 4 nonhematologic toxicities were neutropenic fever (68%), infections (36%), and electrolyte abnormalities. Forty-one patients (82%) had oral mucositis, which was mostly grades 1 to 2 (6% grade 3). Moderate or severe gastrointestinal toxicities were uncommon. There were no treatment-related deaths. Forty-nine patients (98%) had neutrophil and platelet engraftment at a median of 10 and 19 days, respectively. At response assessment at 60 to 100 days after autologous stem cell transplantation, 42 patients (82%) were in complete remission, 2 in partial remission, and 6 had progressive disease. Progression-free survival at 1 year was 70%. These results demonstrate that PG-free melphalan can be used in place of the standard, lyophilized formulation of melphalan in the BEAM regimen for lymphoma patients undergoing autologous stem cell transplantation. It has a safety profile that compares favorably with standard lyophilized melphalan, and the engraftment rate and response rates were consistent with expectations.

Propylene glycol-free melphalan as conditioning regimen for autologous transplantation in myeloma

High-dose melphalan has been the drug of choice for preparative regimens for autologous stem cell transplantation in multiple myeloma. Propylene-free melphalan (Evomela™) is a newer formulation of melphalan, which incorporates Captisol^® to produce a stable product upon reconstitution. In addition to avoiding propylene glycol with its' potential side effects, this approach improves the overall stability of reconstituted melphalan and can ensure intended dose delivery. In this paper, we review the published literature regarding this formulation. We focus on its' chemistry, pharmacokinetics and clinically available data for its use in myeloma autologous stem cell transplantation setting.

Development and Evaluation of a Guideline for Monitoring Propylene Glycol Toxicity in Pediatric Intensive Care Unit Patients Receiving Continuous Infusion Lorazepam

OBJECTIVES

To develop and determine the safety of a guideline, by using osmol gap as an indicator of propylene glycol toxicity for pediatric patients receiving continuous infusion lorazepam.

METHODS

From existing adult data, a guideline was developed for the use of continuous infusion lorazepam in pediatric critical care patients with recommendations for using osmol gap as an indicator of propylene glycol toxicity. A retrospective medical chart review was performed of patients receiving continuous infusion lorazepam from February 2012 to September 2012 for whom the guideline was used.

RESULTS

Twenty-one patients received continuous infusion lorazepam for sedation in the pediatric intensive care unit during the 9-month study period for a total of 23 infusions. Eight patients (34.8%) had an osmol gap of ≥ 12 mOsm/kg during lorazepam infusion, and 7 patients (30.4%) did not have an elevated osmol gap at any point during the infusion. Two patients (8.6%) had clinical toxicity as indicated by elevated anion gap or lactate in addition to an osmol gap ≥ 12 mOsm/kg, while no patients experienced clinical toxicity with an osmol gap < 12 mOsm/kg.

CONCLUSIONS

A guideline for the use of lorazepam infusion in pediatric critical care patients was developed and evaluated for safety. Lorazepam continuous infusions appeared to be associated with minimal toxicity in pediatric intensive care unit patients when the osmol gap monitoring guideline was used.

Propylene glycol toxicity in children

Propylene glycol (PG) is a commonly used solvent for oral, intravenous, and topical pharmaceutical agents. Although PG is generally considered safe, when used in high doses or for prolonged periods, PG toxicity can occur. Reported adverse effects from PG include central nervous system (CNS) toxicity, hyperosmolarity, hemolysis, cardiac arrhythmia, seizures, agitation, and lactic acidosis. Patients at risk for toxicity include infants, those with renal or hepatic insuficiency, epilepsy, and burn patients receiving extensive dermal applications of PG containing products. Laboratory monitoring of PG levels, osmolarity, lactate, pyruvate, bicarbonate, creatinine, and anion gap can assist practitioners in making the diagnosis of PG toxicity. Numerous studies and case reports have been published on PG toxicity in adults. However, very few have been reported in pediatric patient populations. A review of the literature is presented.

Severe propylene glycol toxicity secondary to use of anti-epileptics

Propylene glycol toxicity presenting as high anion gap metabolic acidosis and osmolar gap has been extensively reported in literature, and most of them are secondary to intravenous lorazepam infusion. However, propylene glycol is used as a solvent in a number of medications that are frequently utilized in critical care setting, and hence one should be aware that the toxicity is possible from a variety of medication. Phenobarbital and phenytoin are one of those, and we hereby report a novel case of propylene glycol toxicity secondary to phenobarbital and phenytoin infusion in a patient with refractory status epilepticus. Furthermore, our patient had end-stage renal disease, which we think could have been an important precipitating factor for the toxicity. Because most of the symptoms from propylene glycol toxicity can mimic sepsis-which is very common in critical care unit patients-this life threatening scenario could be easily missed. Regular monitoring of osmolar gap is an easily available intervention in the at risk patients.

Critical care for patients with massive ischemic stroke

Malignant cerebral edema following ischemic stroke is life threatening, as it can cause inadequate blood flow and perfusion leading to irreversible tissue hypoxia and metabolic crisis. Increased intracranial pressure and brain shift can cause herniation syndrome and finally brain death. Multiple randomized clinical trials have shown that preemptive decompressive hemicraniectomy effectively reduces mortality and morbidity in patients with malignant middle cerebral artery infarction. Another life-saving decompressive surgery is suboccipital craniectomy for patients with brainstem compression by edematous cerebellar infarction. In addition to decompressive surgery, cerebrospinal fluid drainage by ventriculostomy should be considered for patients with acute hydrocephalus following stroke. Medical treatment begins with sedation, analgesia, and general measures including ventilatory support, head elevation, maintaining a neutral neck position, and avoiding conditions associated with intracranial hypertension. Optimization of cerebral perfusion pressure and reduction of intracranial pressure should always be pursued simultaneously. Osmotherapy with mannitol is the standard treatment for intracranial hypertension, but hypertonic saline is also an effective alternative. Therapeutic hypothermia may also be considered for treatment of brain edema and intracranial hypertension, but its neuroprotective effects have not been demonstrated in stroke. Barbiturate coma therapy has been used to reduce metabolic demand, but has become less popular because of its systemic adverse effects. Furthermore, general medical care is critical because of the complex interactions between the brain and other organ systems. Some challenging aspects of critical care, including ventilator support, sedation and analgesia, and performing neurological examinations in the setting of a minimal stimulation protocol, are addressed in this review.

Clinical practice guidelines for the management of pain, agitation, and delirium in adult patients in the intensive care unit

OBJECTIVE

To revise the "Clinical Practice Guidelines for the Sustained Use of Sedatives and Analgesics in the Critically Ill Adult" published in Critical Care Medicine in 2002.

METHODS

The American College of Critical Care Medicine assembled a 20-person, multidisciplinary, multi-institutional task force with expertise in guideline development, pain, agitation and sedation, delirium management, and associated outcomes in adult critically ill patients. The task force, divided into four subcommittees, collaborated over 6 yr in person, via teleconferences, and via electronic communication. Subcommittees were responsible for developing relevant clinical questions, using the Grading of Recommendations Assessment, Development and Evaluation method (http://www.gradeworkinggroup.org) to review, evaluate, and summarize the literature, and to develop clinical statements (descriptive) and recommendations (actionable). With the help of a professional librarian and Refworks database software, they developed a Web-based electronic database of over 19,000 references extracted from eight clinical search engines, related to pain and analgesia, agitation and sedation, delirium, and related clinical outcomes in adult ICU patients. The group also used psychometric analyses to evaluate and compare pain, agitation/sedation, and delirium assessment tools. All task force members were allowed to review the literature supporting each statement and recommendation and provided feedback to the subcommittees. Group consensus was achieved for all statements and recommendations using the nominal group technique and the modified Delphi method, with anonymous voting by all task force members using E-Survey (http://www.esurvey.com). All voting was completed in December 2010. Relevant studies published after this date and prior to publication of these guidelines were referenced in the text. The quality of evidence for each statement and recommendation was ranked as high (A), moderate (B), or low/very low (C). The strength of recommendations was ranked as strong (1) or weak (2), and either in favor of (+) or against (-) an intervention. A strong recommendation (either for or against) indicated that the intervention's desirable effects either clearly outweighed its undesirable effects (risks, burdens, and costs) or it did not. For all strong recommendations, the phrase "We recommend …" is used throughout. A weak recommendation, either for or against an intervention, indicated that the trade-off between desirable and undesirable effects was less clear. For all weak recommendations, the phrase "We suggest …" is used throughout. In the absence of sufficient evidence, or when group consensus could not be achieved, no recommendation (0) was made. Consensus based on expert opinion was not used as a substitute for a lack of evidence. A consistent method for addressing potential conflict of interest was followed if task force members were coauthors of related research. The development of this guideline was independent of any industry funding.

CONCLUSION

These guidelines provide a roadmap for developing integrated, evidence-based, and patient-centered protocols for preventing and treating pain, agitation, and delirium in critically ill patients.

Sedation for critically ill or injured adults in the intensive care unit: a shifting paradigm

As most critically ill or injured patients will require some degree of sedation, the goal of this paper was to comprehensively review the literature associated with use of sedative agents in the intensive care unit (ICU). The first and selected latter portions of this article present a narrative overview of the shifting paradigm in ICU sedation practices, indications for uninterrupted or prolonged ICU sedation, and the pharmacology of sedative agents. In the second portion, we conducted a structured, although not entirely systematic, review of the available evidence associated with use of alternative sedative agents in critically ill or injured adults. Data sources for this review were derived by searching OVID MEDLINE and PubMed from their first available date until May 2012 for relevant randomized controlled trials (RCTs), systematic reviews and/or meta-analyses and economic evaluations. Advances in the technology of mechanical ventilation have permitted clinicians to limit the use of sedation among the critically ill through daily sedative interruptions or other means. These practices have been reported to result in improved mortality, a decreased length of ICU and hospital stay and a lower risk of drug-associated delirium. However, in some cases, prolonged or uninterrupted sedation may still be indicated, such as when patients develop intracranial hypertension following traumatic brain injury. The pharmacokinetics of sedative agents have clinical importance and may be altered by critical illness or injury, co-morbid conditions and/or drug-drug interactions. Although use of validated sedation scales to monitor depth of sedation is likely to reduce adverse events, they have no utility for patients receiving neuromuscular receptor blocking agents. Depth of sedation monitoring devices such as the Bispectral Index (BIS©) also have limitations. Among existing RCTs, no sedative agent has been reported to improve the risk of mortality among the critically ill or injured. Moreover, although propofol may be associated with a shorter time to tracheal extubation and recovery from sedation than midazolam, the risk of hypertriglyceridaemia and hypotension is higher with propofol. Despite dexmedetomidine being linked with a lower risk of drug-associated delirium than alternative sedative agents, this drug increases risk of bradycardia and hypotension. Among adults with severe traumatic brain injury, there are insufficient data to suggest that any single sedative agent decreases the risk of subsequent poor neurological outcomes or mortality. The lack of examination of confounders, including the type of healthcare system in which the investigation was conducted, is a major limitation of existing pharmacoeconomic analyses, which likely limits generalizability of their results.

Propylene glycol produces excessive apoptosis in the developing mouse brain, alone and in combination with phenobarbital

INTRODUCTION

Propylene glycol (PG) is a common solvent used in medical preparations. It is generally recognized as safe at regulated concentrations; however, its apoptotic potential is unknown.

RESULTS

PG triggered widespread apoptotic neurodegeneration with the greatest damage at postnatal day 7 (P7). Significant apoptosis was observed at doses as low as 2 ml/kg. These findings have implications for the safety of drug preparations used in pediatric medicine. The anticonvulsant phenobarbital (PB), which alone produces apoptosis in the immature central nervous system (CNS) is prepared in 68% PG and 10% ethanol (EtOH). We assessed whether PG contributes to the neurotoxic potential of PB. The agents (both at subtoxic doses) produce significantly more apoptosis when used in combination.

DISCUSSION

In conclusion, finding an alternative non-apoptotic solvent that can be used as a substitute for PG may be beneficial to patients.

METHODS

C57BL/6 mice (P4-30) were exposed to PG to examine whether PG could produce apoptosis in the developing CNS.

Analytic reviews: managing the agitated patient in the ICU: sedation, analgesia, and neuromuscular blockade

Physical and psychological distress is exceedingly common among critically ill patients and manifests generically as agitation. The dangers of over- and undertreatment of agitation have been well described, and the intensive care unit (ICU) physician must strike a balance in the fast-paced, dynamic ICU environment. Identification of common reversible etiologies for distress may obviate the need for pharmacologic therapy, but most patients receive some combination of sedative, analgesic, and neuroleptic medications during the course of their critical illness. As such, understanding key pharmacologic features of commonly used agents is critical. Structured protocols and objective assessment tools can optimize drug delivery and may ultimately improve patient outcomes by reducing ventilator days, ICU length of stay, and by reducing cognitive dysfunction.

Hunting down a double gap metabolic acidosis

Double gap metabolic acidosis occurs in the setting of unmeasured active osmoles in the serum (osmolal gap) and anion gap (AG) metabolic acidosis. We describe a 67-year-old woman with acute respiratory failure on mechanical ventilator from pneumonia and anuric acute on chronic renal failure (urea nitrogen 21.4 mmol/L, creatinine 530.4 μmol/L) requiring haemodialysis (HD). On hospital day 5, she was found to have progressive metabolic acidosis (serum pH 7.16, PCO2 4.38 kPa, HCO3− 12.1 mmol/L and AG 21 mmol/L). There was no evidence of hypoxaemia, hypoperfusion or haemodynamic instability. Normal serum ketone and l-lactate but high serum osmolal gap (89.4 mmol/kg) was detected. A search for toxic alcohols revealed a high serum propylene glycol (PG 32.9 mmol/L), a stabilizing solvent for intravenous formulations of lorazepam, which was being used as sedation for mechanical ventilation. Unexpectedly, serum l- and d-lactate as metabolites of PG were not elevated. Although extended HD for eight hours completely removed serum PG and the osmolal gap, the predialysis high AG metabolic acidosis persisted, potentially related to hypercatabolism and anuric renal failure. PG should be in the differential diagnosis of the disorders with high osmolar gap and may not always be associated with l- or d-lactic acidosis.

Care of the intubated emergency department patient

BACKGROUND

Emergency physicians perform tracheal intubation and initiate mechanical ventilation for critically ill patients on a daily basis. With the current national challenges of intensive care unit bed availability, intubated patients now often remain in the emergency department (ED) for exceedingly long periods of time. As a result, care of the intubated patient falls to the emergency physician (EP). Given the potential for significant morbidity and mortality, it is crucial for the EP to possess the most current, up-to-date information pertaining to the care of intubated patients.

DISCUSSION

This article discusses critical aspects in the ED management of intubated and mechanically ventilated patients. Specifically, emphasis is placed on providing adequate sedation and analgesia, limiting the use of neuromuscular blocking agents, correctly setting and adjusting the mechanical ventilator, utilizing appropriate monitoring modalities, and providing key supportive measures. Despite these measures, inevitably, some patients deteriorate while receiving mechanical ventilation. The article concludes with a discussion outlining a step-wise approach to evaluating the intubated patient who develops respiratory distress or circulatory compromise. With this information, the EP can more effectively care for ventilated patients while minimizing morbidity, and ultimately, improving outcome.

CONCLUSION

Essential components of the care of intubated ED patients includes administering adequate sedative and analgesic medications, using lung-protective ventilator settings with attention to minimizing ventilator-induced lung injury, elevating the head of the bed in the absence of contraindications, early placement of an orogastric tube, and providing prophylaxis for stress-related mucosal injury and deep venous thrombosis when indicated.

Propylene glycol accumulation in critically ill patients receiving continuous intravenous lorazepam infusions

BACKGROUND

Lorazepam is recommended by the Society of Critical Care Medicine as the preferred agent for sedation of critically ill patients. Intravenous lorazepam contains propylene glycol, which has been associated with toxicity when high doses of lorazepam are administered.

OBJECTIVE

To evaluate the accumulation of propylene glycol in critically ill patients receiving lorazepam by continuous infusion and determine factors associated with propylene glycol concentration.

METHODS

A 6-month, retrospective, safety assessment was conducted of adults admitted to the medical intensive care unit who were receiving lorazepam by continuous infusion for 12 hours or more. Propylene glycol serum concentrations were obtained 24-48 hours after continuous-infusion lorazepam was initiated and every 3-5 days thereafter. Propylene glycol accumulation was defined as concentrations of 25 mg/dL or more. Groups with and without propylene glycol accumulation were compared and factors associated with propylene glycol concentration were determined using multivariate correlation regression analyses.

RESULTS

Forty-eight propylene glycol serum samples were obtained from 33 patients. Fourteen (42%) patients had propylene glycol accumulation, representing 23 (48%) serum samples. Univariate analyses showed the following factors were related to propylene glycol accumulation: baseline renal dysfunction, presence of alcohol withdrawal, sex, age, Acute Physiology and Chronic Health Evaluation (APACHE II) score, rate of lorazepam continuous infusion, and 24-hour lorazepam dose. Multivariate linear regression modeling demonstrated that propylene glycol concentration was strongly associated with the continuous infusion rate and 24-hour dose (adjusted r(2) > or = 0.77; p < 0.001). Independent correlation analyses showed that these 2 variables were so strongly associated with propylene glycol concentration (r(2) > or = 0.71; p < 0.001) that they alone predicted propylene glycol concentration. Seven (21%) patients developed renal dysfunction after continuous-infusion lorazepam was initiated, but associated causes were indeterminable. Other possible propylene glycol-associated adverse effects were not observed.

CONCLUSIONS

The continuous infusion rate and cumulative 24-hour lorazepam dose are strongly associated with and independently predict propylene glycol concentrations. Despite the absence of confirmed propylene glycol-associated adverse effects, clinicians should be aware that propylene glycol accumulation may occur with continuous-infusion lorazepam.

Sedation management in the mechanically ventilated critically ill patient

Sedation management in the mechanically ventilated critically ill patient is a topic of continuing interest in the critical care literature. The wide variety of clinical practices described in the literature with regard to sedation management has limited the implementation of evidence-based practice guidelines. Common themes for a coherent sedation management strategy include articulation of indications for sedation, initial and daily evaluation of sedation goals, sedation-level assessment, appropriate sedative selection, effective sedation management strategy, and efficient sedation weaning strategy. We provide a summary of the literature on key aspects of sedation in clinical practice. Evidence-based recommendations are provided for clinicians involved in the management of sedation in mechanically ventilated patients.

Hyperosmolar, increased-anion-gap metabolic acidosis and hyperglycemia after etomidate infusion

Hyperosmolar increased-anion-gap metabolic acidosis without hyperglycemia has been reported after infusions of etomidate and other medications containing propylene glycol. We report a case of this biochemical abnormality with severe hyperglycemia. Cessation of the etomidate infusion along with other supportive measures resulted in prompt resolution of the metabolic acidosis and hyperglycemia.

A prospective evaluation of propylene glycol clearance and accumulation during continuous-infusion lorazepam in critically ill patients

Propylene glycol is a commonly used diluent in several pharmaceutical preparations, including the sedative lorazepam. Fifty critically ill patients receiving continuous-infusion lorazepam for a minimum of 36 hours were prospectively evaluated to determine the extent of propylene glycol accumulation over time, characterize propylene glycol clearance in the presence of critical illness, and develop a pharmacokinetic model that would predict clearance based on patient-specific clinical, laboratory, and demographic factors. In this cohort, the median lorazepam infusion rate was 2.1 mg/h (0.5-18). Propylene glycol concentration correlated poorly with osmolality, osmol gap, and lactate. In all, 8 patients (16%) had significant propylene glycol accumulation (>25mg/dL). When propylene glycol concentrations were >25 mg/dL, the median lorazepam infusion rate before sample collection was higher, 6.4 (1.9-11.3) versus 2.0 (0.5-7.4) mg/h (P =.0003). A linear first-order model with interoccasion variability on clearance adjusted for total body weight and Acute Physiology and Chronic Health Evaluation II score predicted propylene glycol concentration.

Metabolic acidosis in the critically ill: part 2. Causes and treatment

The correct identification of the cause, and ideally the individual acid, responsible for metabolic acidosis in the critically ill ensures rational management. In Part 2 of this review, we examine the elevated (corrected) anion gap acidoses (lactic, ketones, uraemic and toxin ingestion) and contrast them with nonelevated conditions (bicarbonate wasting, renal tubular acidoses and iatrogenic hyperchloraemia) using readily available base excess and anion gap techniques. The potentially erroneous interpretation of elevated lactate signifying cell ischaemia is highlighted. We provide diagnostic and therapeutic guidance when faced with a high anion gap acidosis, for example pyroglutamate, in the common clinical scenario 'I can't identify the acid--but I know it's there'. The evidence that metabolic acidosis affects outcomes and thus warrants correction is considered and we provide management guidance including extracorporeal removal and fomepizole therapy.

The effects of pharmaceutical excipients on drug disposition

Many new chemical entities are poorly soluble, requiring the use of co-solvents or excipients to produce suitable intravenous formulations for early pre-clinical development studies. There is some evidence in the literature that these formulation components can have significant physiological and physicochemical effects which may alter the distribution and elimination of co-administered drugs. Such effects have the potential to influence the results of pre-clinical pharmacokinetic studies, giving a false impression of a compound's intrinsic pharmacokinetics and frustrating attempts to predict the drug's ultimate clinical pharmacokinetics. This review describes the reported effects of commonly used co-solvents and excipients on drug pharmacokinetics and on physiological systems which are likely to influence drug disposition. Such information will be useful in study design and evaluating data from pharmacokinetic experiments, so that the potential influence of formulation components can be minimised.

Acute kidney injury, hyperosmolality and metabolic acidosis associated with lorazepam

BACKGROUND

A 54-year-old male with a history of multiple admissions for alcohol intoxication was admitted to hospital with right flank pain. He received a high-dose lorazepam infusion for alcohol withdrawal during hospitalization and developed severe hyperosmolality, high anion gap metabolic acidosis, and acute kidney injury on his eighth day of hospitalization.

INVESTIGATIONS

Serum chemistries, arterial blood gas analysis, and measurement of serum propylene glycol, ethylene glycol and methanol levels.

DIAGNOSIS

Propylene glycol toxicity.

MANAGEMENT

Discontinuation of lorazepam infusion, administration of fomepizole, hemodialysis for five consecutive days, hemodynamic support, and follow-up of serum osmolality as a measure of propylene glycol decay.

Recognition, treatment, and prevention of propylene glycol toxicity

Propylene glycol is a commonly used solvent for oral, intravenous, and topical pharmaceutical preparations. Although it is considered safe, large intravenous doses given over a short period of time can be toxic. Underlying renal insufficiency and hepatic dysfunction raise risk for toxicity. Toxic effects include hyperosmolality, increased anion gap metabolic acidosis (due to lactic acidosis), acute kidney injury, and sepsis-like syndrome. Treatment of toxicity includes hemodialysis to effectively remove propylene glycol. Prevention is best achieved by limiting the dose of propylene glycol infused.

Sedation and analgesia in the intensive care unit: evaluating the role of dexmedetomidine

PURPOSE

A review highlighting the application of sedatives and analgesics in the intensive care unit (ICU) setting, with a focus on the use of dexmedetomidine, is presented.

SUMMARY

Relevant and applicable clinical trials that resulted from a search of the literature from 1966 to July 2006 using key search terms such as dexmedetomidine, intensive care unit, sedation, delirium, and analgesia were evaluated. Many agents have been evaluated in the search of the optimal regimen for sedation and analgesia in the ICU, including opioids, benzodiazepines, propofol, and antipsychotic agents. Dexmedetomidine has demonstrated efficacy as a sedative analgesic on the basis of its ability to lower opioid, benzodiazepine, and propofol requirements in clinical trials. The role of dexmedetomidine in ICU clinical practice is limited because of a lack of mortality and other morbidity endpoints, such as ICU length of stay, hospital length of stay, time to extubation, long-term complications after discharge from the ICU, and delirium. The most commonly reported adverse effects of dexmedetomidine are secondary to its effects as an alpha(2)-receptor agonist and are cardiac in nature. A detailed cost analysis may be warranted to justify the relatively high acquisition cost of dexmedetomidine.

CONCLUSION

Dexmedetomidine may be an effective agent for ICU sedation and analgesia. However, the lack of clinically relevant endpoints in trials, the concern about adverse cardiovascular effects, and the relatively high acquisition cost of this drug limit its use to a select number of patients who may benefit from its distinguished mechanism of action.

CRITICAL CARE ISSUES FOR THE NEPHROLOGIST: Acid-base Disturbances in the Intensive Care Unit: Metabolic Acidosis

This article will discuss metabolic acidosis and, to a lesser extent, metabolic alkalosis in the ICU setting. A classification and clinical approach will be the focus.

Economic evaluation of sustained sedation/analgesia in the intensive care unit

Lorazepam, midazolam, propofol and opioids are the primary agents that are used for sustained sedation and analgesia of critically ill patients. The choice of agent depends on safety profiles, expected outcomes, cost, patient characteristics and clinical experience. Few studies have comparatively evaluated the sedatives in terms of cost. Many factors, aside from drug costs, influence the total cost of sedation in the intensive care unit. This article reviews the cost parameters of intensive care unit sedation that are specific to the characteristics of commonly used sedatives and analgesics, evaluates economic studies and cost models, summarises alternative methods of sedation and analgesia, and provides practical recommendations for methods of cost containment, including daily sedation interruption, sedation monitoring and protocol implementation.

Utilizing the Laboratory in the Poisoned Patient

This article examines the role of common laboratory tests in the evaluation of a poisoned patient. Numerous laboratory tests maybe useful to clinicians caring for poisoned patients. Clinicians should not order a broad range of tests indiscriminately, but rather thoughtfully consider appropriate tests. The results of the tests should be reviewed in the context of the clinical scenario.

Osmol Gap as a Surrogate Marker for Serum Propylene Glycol Concentrations in Patients Receiving Lorazepam for Sedation

STUDY OBJECTIVES

To correlate serum propylene glycol concentration with osmol gap, serum lactate concentration, and amount of propylene glycol administered to mechanically ventilated patients receiving continuous infusions of lorazepam (80% propylene glycol by weight), and to characterize the prevalence of hyperosmolality and range of serum propylene glycol concentrations in this patient population.

DESIGN

Prospective, controlled, observational study.

SETTING

Adult surgical and cardiothoracic intensive care units (ICUs) of a 1200-bed, urban, tertiary care, teaching hospital.

PATIENTS

Sixty-four consecutively enrolled intensive care patients requiring mechanical ventilation and pharmacologic sedation.

INTERVENTION

Thirteen patients received continuous infusions of high-dose lorazepam (> or = 6 mg/hr) for a minimum of 36 hours, and 26 received continuous infusions of low-dose lorazepam (2-5.99 mg/hr) for 36 hours. Twenty-five control patients received sedatives that did not contain propylene glycol.

MEASUREMENTS AND MAIN RESULTS

Serum propylene glycol and lactate concentrations, osmolality, and basic metabolic profiles were obtained 72-108 hours after ICU admission. Clinical data, drug administration, and severity of illness scores were recorded. Osmol gap and the amount of propylene glycol administered before serum sampling predicted propylene glycol concentrations (r(2)=0.692, p<0.05). Osmol gap alone also predicted serum propylene glycol concentrations (r(2)=0.532, p<0.05). Serum lactate concentrations did not correlate with serum propylene glycol concentrations. Unlike the low-dose and control patients, eight (62%) of 13 high-dose patients had osmol gaps above 10. All 13 high-dose patients had serum propylene glycol concentrations previously associated with toxicity.

CONCLUSION

Osmol gap can be used as a surrogate marker for serum propylene glycol concentration. In critically ill patients receiving lorazepam for sedation, an osmol gap above 10 was associated with concentrations previously reported to cause toxicity.

Utilizing diagnostic investigations in the poisoned patient

Numerous diagnostic tests may be useful to clinicians caring for poisoned patients. Clinicians should not order a broad range of tests indiscriminately,but rather thoughtfully consider appropriate tests. The results'of the tests should be reviewed in the context of the clinical scenario.

Pharmacoeconomic Modeling of Lorazepam, Midazolam, and Propofol for Continuous Sedation in Critically Ill Patients

STUDY OBJECTIVE

To compare the expected costs of short-, intermediate-, and long-term sedation (< 24, 24-72, and > 72 hrs, respectively) with propofol, lorazepam, and midazolam in an intensive care unit.

METHODS

Decision-analysis models were constructed for each sedative and each duration by using institutional costs associated with drug administration and adverse events (including personnel time). Costs were expressed in 2002 U.S. dollars. Adverse events were agitation, hypertriglyceridemia and/or pancreatitis, hypotension, nutritional changes, ventilator-associated pneumonia, and prolonged awakening and/or extubation. MEDLINE and EMBASE databases were searched to obtain durations of sedation, the incidence of outcomes, and cost estimates of outcomes. The ability to maintain specific levels of sedation was assumed equivalent among the sedatives. Univariate sensitivity analyses were conducted to determine the cost-driving variables, and probabilistic sensitivity analyses were conducted by using second-order Monte Carlo simulations.

RESULTS

Weighted mean durations of sedation from 50 studies were 13.46 (short term), 45.27 (intermediate term), and 119.78 (long term) hours. Expected costs for sedation with lorazepam, midazolam, and propofol, respectively, were 497 dollars, 294 dollars, and 272 dollars short term; 932 dollars, 587 dollars, and 674 dollars intermediate term; and 1604 dollars, 1737 dollars, and 2033 dollars long term. Propofol was least costly in 86% of the short-term simulations, midazolam was least costly in 97.5% of the intermediate-term simulations, and lorazepam was least costly in 84% of the long-term simulations. The most important cost-driver for all sedatives was drug cost. Prolonged extubation after sedation was an important cost-driver for lorazepam and midazolam, especially as sedation was lengthened.

CONCLUSION

Propofol, midazolam, and lorazepam had the lowest expected costs for short-, intermediate-, and long-term sedation, respectively. Many factors aside from drug costs influenced the cost of sedation.

Propylene Glycol–Induced Lactic Acidosis in a Patient with Normal Renal Function: A Proposed Mechanism and Monitoring Recommendations

OBJECTIVE:

To report a case of severe propylene glycol–induced lactic acidosis not attributable to renal dysfunction that was secondary to administration of high-dose intravenous lorazepam.

CASE SUMMARY:

A 24-year-old female with community-acquired pneumonia presented with severe acute respiratory distress syndrome. To maintain adequate sedation and ventilation and reduce airway pressure, several relaxation strategies were used including high-dose intravenous lorazepam, fentanyl, and cisatracurium. After 18 days of high-dose continuous infusion of lorazepam (maximum dose 50 mg/h), the patient developed severe lactic acidosis secondary to propylene glycol toxicity, the main diluent of lorazepam. The acidosis temporarily resolved with bicarbonate administration and discontinuation of lorazepam. Her renal function remained stable for a time (serum creatinine 0.5 mg/dL, blood urea nitrogen 10 mg/dL, urine output 100–200 mL/h). However, after several more days, the patient's condition deteriorated, and she ultimately died.

DISCUSSION:

Previous cases of propylene glycol toxicity secondary to high-dose lorazepam infusion have occurred in patients with compromised renal function. Our patient's renal function remained stable throughout the hospital course, which caused us to look further for an explanation for the propylene glycol–induced lactic acidosis. Based on the Naranjo probability scale, propylene glycol was determined to be the probable cause of lactic acidosis. Since this case occurred, our intensive care unit has instituted recommendations for the prevention of lorazepam-associated propylene glycol toxicity.

CONCLUSIONS:

Our case highlights the development of propylene glycol–induced lactic acidosis secondary to high-dose lorazepam infusion not associated with renal dysfunction.