Short-term lorazepam infusion and concern for propylene glycol toxicity: case report and review

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.

Detection of pediatric drug-induced kidney injury signals using a hospital electronic medical record database

Background: Drug-induced kidney injury (DIKI) is one of the most common complications in clinical practice. Detection signals through post-marketing approaches are of great value in preventing DIKI in pediatric patients. This study aimed to propose a quantitative algorithm to detect DIKI signals in children using an electronic health record (EHR) database.

Methods: In this study, 12 years of medical data collected from a constructed data warehouse were analyzed, which contained 575,965 records of inpatients from 1 January 2009 to 31 December 2020. Eligible participants included inpatients aged 28 days to 18 years old. A two-stage procedure was adopted to detect DIKI signals: 1) stage 1: the suspected drugs potentially associated with DIKI were screened by calculating the crude incidence of DIKI events; and 2) stage 2: the associations between suspected drugs and DIKI were identified in the propensity score-matched retrospective cohorts. Unconditional logistic regression was used to analyze the difference in the incidence of DIKI events and to estimate the odds ratio (OR) and 95% confidence interval (CI). Potentially new signals were distinguished from already known associations concerning DIKI by manually reviewing the published literature and drug instructions.

Results: Nine suspected drugs were initially screened from a total of 652 drugs. Six drugs, including diazepam (OR = 1.61, 95%CI: 1.43–1.80), omeprazole (OR = 1.35, 95%CI: 1.17–1.54), ondansetron (OR = 1.49, 95%CI: 1.36–1.63), methotrexate (OR = 1.36, 95%CI: 1.25–1.47), creatine phosphate sodium (OR = 1.13, 95%CI: 1.05–1.22), and cytarabine (OR = 1.17, 95%CI: 1.06–1.28), were demonstrated to be associated with DIKI as positive signals. The remaining three drugs, including vitamin K1 (OR = 1.06, 95%CI: 0.89–1.27), cefamandole (OR = 1.07, 95%CI: 0.94–1.21), and ibuprofen (OR = 1.01, 95%CI: 0.94–1.09), were found not to be associated with DIKI. Of these, creatine phosphate sodium was considered to be a possible new DIKI signal as it had not been reported in both adults and children previously. Moreover, three other drugs, namely, diazepam, omeprazole, and ondansetron, were shown to be new potential signals in pediatrics.

Conclusion: A two-step quantitative procedure to actively explore DIKI signals using real-world data (RWD) was developed. Our findings highlight the potential of EHRs to complement traditional spontaneous reporting systems (SRS) for drug safety signal detection in a pediatric setting.

Taking Sleeping Pills and the Risk of Chronic Kidney Disease: A Nationwide Population-Based Retrospective Cohort Study

Background: Sleeping disorder has been associated with chronic kidney disease (CKD); however, the correlation between sleeping pills use and CKD has not been investigated in-depth yet. This study elucidated the potential association of sleeping pill use with the risk of CKD and CKD progression to end-stage renal disease (ESRD) requiring dialysis. Methods: This study was based on a population-based cohort that included 209,755 sleeping pill users among 989,753 individuals. After applying the exclusion criteria, 186,654 sleeping pill users and 373,308 nonusers were enrolled to monitor the occurrence of CKD. Using a cumulative daily dose, we analyzed the types of sleeping pills related to the risk of CKD and ESRD. Propensity score matching and analysis using Cox proportional hazards regression were performed with adjustments for sex, age, and comorbidities. Results: Sleeping pill use was related to increased CKD risk after adjusting for underlying comorbidities (adjusted hazard ratio [aHR] = 1.806, 95% confidence interval [CI]: 1.617-2.105, p < 0.001). With the exception of hyperlipidemia, most comorbidities correlated with an increased risk of CKD. Persistent use of sleeping pills after CKD diagnosis increased the risk of concurrent ESRD (aHR = 7.542; 95% CI: 4.267-10.156; p < 0.001). After the subgroup analysis for sleeping pill use, brotizolam (p = 0.046), chlordiazepoxide (p < 0.001), clonazepam (p < 0.001), diazepam (p < 0.001), dormicum (p < 0.001), estazolam (p < 0.001), fludiazepam (p < 0.001), flunitrazepam (p < 0.001), nitrazepam (p < 0.001), trazodone (p < 0.001), zolpidem (p < 0.001), and zopiclone (p < 0.001) were found to have significant correlation with increased CKD risk. Conclusion: Sleeping pill use was related to an increased risk of CKD and ESRD. Further studies are necessary to corroborate these findings.

[Drug-induced seizures: prevalence, risk factors, treatment and prevention]

There is a growing interest to the problem of drug-induced epileptic seizures (ES) due to their relatively high prevalence, poor prognosis, a large number of different drugs associated with the development of drug-induced ES, and low awareness among general practitioners. Drug-induced ES are most often associated with the use of antidepressants, antipsychotics, antiepileptic drugs (overdose or as a result of discontinuation), antibiotics, immunosuppressants and immunomodulators, antitumor agents, analgesics, central nervous system stimulators, anesthetics etc. The prevalence of drug-induced ES varies with different drugs. It is estimated that about 6.1% of the first occurring ES are drug-induced. Risk factors for drug-induced ES include a history of epilepsy or ES, cancer, blood-brain barrier dysfunction, several concomitant neurological diseases, mental disorders, childhood, old and very old age, fever, impaired liver metabolism in patients with liver diseases, impaired drug excretion in patients with kidney diseases, polypharmacy, pharmacokinetic properties of the drugs themselves, allowing them to penetrate the blood-brain barrier in the central nervous system (lipophilicity, transport and communication with blood plasma proteins), drug concentration in blood serum, method and frequency of drug administration, single and daily doses of drugs. No clinical guidelines for the management of patients with drug-induced ES are available. It is recommended to identify patients at risk: elderly patients, patients with impaired liver and kidney function and patients receiving drugs that can cause ES and/or lower the seizure threshold. Benzodiazepines are the first-line treatment in drug-induced status epilepticus, barbiturates and propofol are the second-line treatment. The general principles for the prevention of drug-induced ES include careful selection of the optimal dose of drugs that can cause ES, especially in patients with impaired liver and/or kidney function, monitoring of several parameters in blood serum (for example, liver enzymes, electrolytes, glucose etc.), monitoring of the blood plasma concentration of certain drugs, avoiding the simultaneous administration of several drugs that stimulate the central nervous system, and a rapid discontinuation of such drugs.

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.

Investigations into the physical and chemical stability of concentrated co-trimoxazole intravenous infusions

Objectives

High dose of intravenous sulfamethoxazole and trimethoprim (co-trimoxazole) is often used in immunocompromised patients for the treatment of Pneumocystis jiroveci pneumonia. Current manufacturer's dilution recommendation for intravenous co-trimoxazole (1:25 v/v) requires the administration of 2 L of additional fluid per day causing serious complications including pulmonary oedema. Intravenous administration of concentrated solution of co-trimoxazole may minimise the risk of fluid overload associated side effects. Therefore, the objective of the study was to investigate the physicochemical stability of concentrated intravenous co-trimoxazole solutions.

Methods

Four ampoules of intravenous co-trimoxazole were injected into an infusion bag containing either 480 (1:25 v/v), 380 (1:20 v/v), 280 (1:15 v/v) or 180 (1:10 v/v) mL of glucose 5% solution. Three bags for each dilution (total 12 bags) were prepared and stored at room temperature. An aliquot was withdrawn immediately (at 0 hour) and after 0.5, 1, 2 and 4 hours of storage for high-performance liquid-chromatography (HPLC) analysis, and additional samples were withdrawn every half an hour for microscopic examination. Each sample was analysed for the concentration of trimethoprim and sulfamethoxazole using a stability indicating HPLC method. Samples were assessed for pH, change in colour (visually) and for particle content (microscopically) immediately after preparation and on each time of analysis.

Results

Intravenous co-trimoxazole at 1:25, 1:20, 1:15 and 1:10 v/v retained more than 98% of the initial concentration of trimethoprim and sulfamethoxazole for 4 hours. There was no major change in pH at time zero and at various time points. Microscopically, no particles were detected for at least 4 hours and 2 hours when intravenous co-trimoxazole was diluted at 1:25 or 1:20 and 1:15 v/v, respectively. More than 1200 particles/mL were detected after 2.5 hours of storage when intravenous co-trimoxazole was diluted at 1:15 v/v.

Conclusions

Intravenous co-trimoxazole is stable over a period of 4 hours when diluted with 380 mL of glucose 5% solution (1:20 v/v) and for 2 hours when diluted with 280 mL glucose 5% solution (1:15 v/v).

Inhibition of drug-induced seizure development in both zebrafish and mouse models by a synthetic nanoreceptor

A synthetic nanoreceptor, cucurbit[7]uril (CB[7]), fully encapsulated pentylenetetrazol (PTZ), a seizure-inducing model drug. As a consequence of the encapsulation, the development of PTZ induced convulsion behaviors in both larval zebrafish and mouse models were dramatically alleviated, suggesting that CB[7] holds great neuroprotection potential against neurotoxic drugs for clinical applications.

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.

Trimethoprim/Sulfamethoxazole-Induced Severe Lactic Acidosis: A Case Report and Review of the Literature

Propylene glycol (PG) is used as a solvent in numerous medications, including trimethoprim/sulfamethoxazole (TMP/SMX) and lorazepam, and is metabolized in the liver to lactic acid. Cases of lactic acidosis related to PG toxicity have been described and always involved large doses of benzodiazepines and PG. We present the first case of severe lactic acidosis after a 3-day course of TMP/SMX alone, involving allegedly safe amounts of PG.A 31-year-old female with neurofibromatosis and pilocytic astrocytoma, receiving temozolomide and steroids, was admitted to the intensive care unit for pneumonia and acute respiratory failure requiring intubation. Her initial hemodynamic and acid-base statuses were normal. She was treated with intravenous TMP/SMX for possible Pneumocystis jirovecii pneumonia and was successfully extubated on day 2. On day 3, she developed tachypnea and arterial blood gas analysis revealed a severe metabolic acidosis (pH 7.2, PCO2 19 mm Hg, bicarbonates 8 mEq/L) with anion gap of 25 mEq/L and lactate of 12.1 mmol/L. TMP/SMX was discontinued and the lactate decreased to 2.9 mmol/L within 24 hours while her plasma bicarbonates normalized, without additional intervention. The patient never developed hypotension or severe hypoxia, and her renal and liver functions were normal. No other cause for lactic acidosis was identified and it resolved after TMP/SMX cessation alone, suggesting PG toxicity.Although PG-related lactic acidosis is well recognized after large doses of lorazepam, clinicians should bear in mind that TMP/SMX contains PG as well and should suspect PG toxicity in patients developing unexplained metabolic acidosis while receiving TMP/SMX.

Treatment of drug-induced seizures

Seizures are a common complication of drug intoxication, and up to 9% of status epilepticus cases are caused by a drug or poison. While the specific drugs associated with drug-induced seizures may vary by geography and change over time, common reported causes include antidepressants, stimulants and antihistamines. Seizures occur generally as a result of inadequate inhibitory influences (e.g., gamma aminobutyric acid, GABA) or excessive excitatory stimulation (e.g. glutamate) although many other neurotransmitters play a role. Most drug-induced seizures are self-limited. However, status epilepticus occurs in up to 10% of cases. Prolonged or recurrent seizures can lead to serious complications and require vigorous supportive care and anticonvulsant drugs. Benzodiazepines are generally accepted as the first line anticonvulsant therapy for drug-induced seizures. If benzodiazepines fail to halt seizures promptly, second line drugs include barbiturates and propofol. If isoniazid poisoning is a possibility, pyridoxine is given. Continuous infusion of one or more anticonvulsants may be required in refractory status epilepticus. There is no role for phenytoin in the treatment of drug-induced seizures. The potential role of ketamine and levetiracetam is promising but not established.

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.

Pain, agitation, delirium, and neuromuscular blockade: a review of basic pharmacology, assessment, and monitoring

Agitation, pain, and delirium are focal points for targeted pharmacologic therapy in the intensive care unit. Understanding how to treat these essential entities necessitates fundamental understanding of the pharmacology of sedation, analgesia, and antipsychotics. Monitoring the effectiveness of these medications is crucial to optimize therapeutic outcomes and minimize untoward effects. Agents used in the management of agitation include drugs that target γ-aminobutyric acid A such as benzodiazepines and propofol and those with other targets such as dexmedetomidine and ketamine. Analgesia in the intensive care unit is controlled primarily using intravenous opioids, which differ on the basis of their potencies and pharmacokinetics. The management of delirium involves preventing its occurrence, removing potential causes, and pharmacotherapy with antipsychotics. Finally, the introduction of paralysis with the use neuromuscular blockers is often necessary in critically ill patients in various situations. In addition to understanding pharmacologic principles associated with the treatment of agitation, pain, and delirium, familiarization with the plethora of assessment tools used to guide therapy in these critically ill patients is mandated. This review focuses on the pharmacology of therapeutic agents used for sedation, analgesia, delirium, and neuromuscular blockade. Significant focus is given to the various assessment tools often used in practice today.

Propylene Glycol–Related Delirium After Esmolol Infusion

Objective: Excipients used in oral or intravenous preparations may cause serious adverse events. Case Summary: We present the case of a 15-year-old boy with hypertrophic cardiomyopathy. In the pediatric intensive care unit, he received high doses of continuous intravenous esmolol (range = 20-400 µg/kg/min) for cardiac rhythm control. After a few days he developed a delirium not responding to high doses of antipsychotics or discontinuation of benzodiazepines. We eventually realized that the IV esmolol formulation contained high doses of propylene glycol and ethanol, which may accumulate after prolonged infusion and cause intoxication. Intoxication with propylene glycolcan cause neuropsychiatric symptoms. The boy’s propylene glycol plasma concentration was approximately 4 g/L, whereas clinical symptoms arise at concentrations above 1 to 1.44 g/L. Application of the Naranjo adverse drug reaction probability scale suggested a probable relationship (score 6) between the propylene glycol infusion and the delirium. After discontinuation of esmolol, the delirium disappeared spontaneously. Discussion: This is the first case describing excipient toxicity of esmolol, with an objective causality assessment revealing a probable relationship for the adverse event—namely, delirium—and esmolol. Conclusion: Although excipient toxicity is a well-known adverse drug reaction, this case stresses the importance for easily available information for and education of physicians.

Issues in the management of acute agitation: how much current guidelines consider safety?

Agitated behavior constitutes up to 10% of emergency psychiatric interventions. Pharmacological tranquilization is often used as a valid treatment for agitation but a strong evidence base does not underpin it. Available literature shows different recommendations, supported by research data, theoretical considerations, or clinical experience. Rapid tranquilization (RT) is mainly based on parenteral drug treatment and the few existing guidelines on this topic, when suggesting the use of first generation antipsychotics and benzodiazepines, include drugs with questionable tolerability profile such as chlorpromazine, haloperidol, midazolam, and lorazepam. In order to systematically evaluate safety concerns related to the adoption of such guidelines, we reviewed them independently from principal diagnosis while examining tolerability data for suggested treatments. There is a growing evidence about safety profile of second generation antipsychotics for RT but further controlled studies providing definitive data in this area are urgently needed.

Pain in the ICU: a psychiatric perspective

Pain is abundant in the intensive care unit (ICU). Successful analgesia demands a comprehensive appreciation for the etiologies of pain, vigilant clinical assessment, and personalized treatments. For the critically ill, frequent threats to mental and bodily integrity magnify the experience of pain, challenging clinicians to respond swiftly and thoughtfully. Because pain is difficult to predict and physiologic correlates are not specific, self-report remains the gold standard assessment. When communication is limited by intubation or cognitive deficits, behavioral pain scales prove useful. Patient-tailored analgesia aspires to mitigate suffering while optimizing alertness and cognitive capacity. Mindfulness of the neuropsychiatric features of pain helps the ICU clinician to clarify limits of traditional analgesia and identify alternative approaches to care. Armed with empirical data and clinical practice recommendations to better conceptualize, identify, and treat pain and its neuropsychiatric comorbidities, the authors (psychiatric consultants, by trade) reinforce holistic approaches to pain management in the ICU. After all, without attempts to understand and relieve suffering on all fronts, pain will remain undertreated.

Treating alcohol withdrawal with oral baclofen: a randomized, double-blind, placebo-controlled trial

BACKGROUND

Abrupt cessation of alcohol intake causes habituated drinkers to experience symptoms of alcohol withdrawal syndrome (AWS).

OBJECTIVE

To determine the effect of the gamma-aminobutyric acid (GABA)-B agonist baclofen on the course of acute symptomatic AWS.

DESIGN

Prospective, randomized, double-blind, placebo-controlled clinical study.

SETTING

Two tertiary-care hospitals in Duluth, Minnesota.

PATIENTS

Inpatient adults admitted for any reason (including AWS) judged to be at high risk for AWS.

INTERVENTION

Inpatients who developed symptoms of AWS received symptom-triggered benzodiazepine treatment using lorazepam by standard protocol, and were randomized to receive baclofen 10 mg or placebo, 3 times per day, orally.

MEASUREMENTS

AWS severity was assessed using the Clinical Institute Withdrawal Assessment of Alcohol Scale, Revised (CIWA-Ar); lorazepam dose was monitored.

RESULTS

Seventy-nine subjects were enrolled. The 44 subjects who developed symptoms of AWS were randomized to baclofen or placebo. Thirty-one subjects (18 baclofen, 13 placebo) completed 72 hours of assessments, either entirely as inpatients or with outpatient follow-up. The need for high doses of benzodiazepines (20 mg or more of lorazepam over 72 hours) to control AWS was less likely in the baclofen treatment group (1 of 18) than in the placebo-treated group (7 of 13) (P = 0.004).

CONCLUSIONS

We found that the use of baclofen was associated with a significant reduction in the use of high doses of benzodiazepine (lorazepam) in the management of symptomatic AWS. The use of low-dose baclofen in the management of AWS deserves further study, as reduced dependence on high-dose benzodiazepines in AWS management could improve patient safety.

Toxin-related seizures

Toxin-related seizures result from an imbalance in the brain's equilibrium of excitation-inhibition. Fortunately, most toxin-related seizures respond to standard therapy using benzodiazepines. However, a few alterations in the standard approach are recommended to ensure optimal care and expedient termination of seizure activity. If 2 doses of a benzodiazepine do not terminate the seizure activity, a therapeutic dose of pyridoxine (5 g intravenously in an adult and 70 mg/kg intravenously in a child) should be considered. Phenytoin should be avoided because it is ineffective for many toxin-induced seizures and is potentially harmful when used to treat seizures induced by theophylline or cyclic antidepressants.

Treatment of lactic acidosis: appropriate confusion

BACKGROUND

Lactic acidosis (LA) is common in hospitalized patients and is associated with poor clinical outcomes. There have been major recent advances in our understanding of lactate generation and physiology. However, treatment of LA is an area of controversy and uncertainty, and the use of agents to raise pH is not clearly beneficial.

AIM AND METHODS

We reviewed animal and human studies on the pathogenesis, impact, and treatment of LA, published in the English language and available through the PubMed/MEDLINE database. Our aim was to clarify the physiology of the generation of LA, its impact on outcomes, and the different treatment modalities available. We also examined relevant data regarding LA induced by medications commonly prescribed by hospitalists: biguanides, nucleoside analog reverse-transcriptase inhibitors (NRTIs), linezolid, and lorazepam.

RESULTS/CONCLUSIONS

Lactic acid is a marker of tissue ischemia but it also may accumulate without tissue hypoperfusion. In the latter circumstance, lactic acid accumulation may be an adaptive mechanism-a novel possibility quite in contrast to the traditional view of lactic acid as only a marker of tissue ischemia. Studies on the treatment of LA with sodium bicarbonate or other buffers fail to show consistent clinical benefit. Severe acidemia in the setting of LA is a particularly poorly studied area. In the settings of medication-induced LA, optimal treatment, apart from prompt cessation of the offending agent, is still unclear.

Exposure to the pharmaceutical excipients benzyl alcohol and propylene glycol among critically ill neonates

OBJECTIVE

To document neonatal exposures to the potentially harmful pharmaceutical excipients benzyl alcohol (BA) and propylene glycol (PG) present in parenteral medications routinely administered in the intensive care unit.

DESIGN

Retrospective, observational study.

SETTING

Neonatal and pediatric intensive care units of a tertiary care, university hospital.

PATIENTS

Randomly selected sample of 170 episodes of exposure to parenteral medications containing BA (n = 88) or PG (n = 82).

MEASUREMENTS

We identified all medication sources of BA or PG administered to study neonates during hospitalization, and calculated cumulative doses (mg/kg/day and mg/day) of BA or PG received as a result of exposure to those medications.

MAIN RESULTS

We observed a wide range in the cumulative excipient dose received by neonates. Median (range) cumulative dose was 4.5 mg/kg/day (0.6-319.5 mg/kg/day) for BA, and 204.9 mg/kg/day (17.3-9472.7 mg/kg/day) for PG. Patients who received medications via continuous infusion received significantly higher excipient doses than patients who received medications intermittently (p < 0.0001). In this subset of patients, median cumulative excipient doses (BA, 106.3 mg/kg/day and PG, 4554.5 mg/kg/day) were approximately 21 and 180 times the acceptable daily intakes of BA and PG (5 and 25 mg/kg/day), respectively, and exceeded the doses above which toxicity has been reported in infants. No significant correlation between duration of medication administration and cumulative excipient exposure was identified for BA or PG. Midazolam and lorazepam were involved in over two-thirds of BA and PG exposures, respectively.

CONCLUSIONS

Critically ill neonates, especially those receiving medications by continuous infusion, are at risk of being exposed to BA and PG at potentially toxic doses during routine medication administration. Given the serious adverse reactions known to be associated with BA and PG, future studies are warranted to determine the clinical consequences associated with this degree of excipient exposure.

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.

Propylene glycol-induced lactic acidosis in a patient receiving continuous infusion pentobarbital

OBJECTIVE

To report a case of probable propylene glycol (PG) toxicity in a patient receiving continuous infusion of pentobarbital for refractory status epilepticus.

CASE SUMMARY

A 59-year-old woman with a declining mental status was admitted to the intensive care unit for management of status epilepticus. After failing to achieve the therapeutic endpoint of electroencephalogram burst suppression with a continuous infusion of propofol, the sedative regimen was changed to continuous infusion of pentobarbital. The patient received a loading dose of 450 mg (5 mg/kg), and the maintenance infusion was titrated to a dose of 10 mg/kg/h to achieve burst suppression. Twelve hours after the pentobarbital infusion was started, the patient developed an anion gap metabolic acidosis, elevated serum lactate level, hyperosmolality, and increased osmolal gap. The pentobarbital infusion was discontinued, and the patient's acidosis and hyperosmolality resolved.

DISCUSSION

Pentobarbital contains 40% v/v of PG, which was thought to be a potential source of the patient's metabolic derangements. Reports of toxicity with drugs containing PG, particularly intravenous lorazepam, have been well described in the literature. What we describe, however, is one of few reports involving intravenous pentobarbital. The Naranjo probability scale supports a probable drug-related adverse event in our patient.

CONCLUSIONS

PG toxicity is a potential complication associated with intravenous pentobarbital. Practitioners should be aware of the PG content of pentobarbital and should be familiar with the signs and symptoms associated with PG toxicity.

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.

Symptom-driven lorazepam protocol for treatment of severe alcohol withdrawal delirium in the intensive care unit

STUDY OBJECTIVE

To compare outcomes of treating alcohol withdrawal delirium (AWD) with a symptom-driven benzodiazepine protocol versus nonprotocol benzodiazepine infusions in the intensive care unit (ICU).

DESIGN

Retrospective observational study of a quality improvement project.

SETTING

Medical intensive care unit at a Veterans Affairs medical center.

PATIENTS

Thirty-six patients who had 40 ICU admissions for AWD between January 1, 1994, and May 31, 2003. Sixteen episodes (15 patients [historical controls]) occurred before implementation of the symptom-driven protocol in 1998, and 24 episodes (21 patients) occurred after implementation.

MEASUREMENTS AND MAIN RESULTS

Outcomes evaluated were time to reach symptom control, total dose of benzodiazepine, amount of time receiving continuous benzodiazepine infusion, length of ICU and hospital stay, polypharmacy (use of multiple benzodiazepines), and complications of treatment. The historical control group was treated according to physician preference, which consisted of continuous-infusion midazolam without a protocol. The symptom-driven protocol used lorazepam administered initially as intermittent intravenous doses, progressing to a continuous intravenous infusion according to a locally developed symptom scale. The mean +/- SD values for the outcomes in the historical control group versus the protocol group were as follows: time to control symptoms 19.4 +/- 9.7 versus 7.7 +/- 4.9 hours (p=0.002), cumulative benzodiazepine dose in lorazepam equivalents 1677 +/- 937 versus 1044 +/- 534 mg (p=0.014), time receiving benzodiazepine continuous infusion 122.1 +/- 64.4 versus 52.0 +/- 35.1 hours (p=0.001), length of stay in the ICU 7.7 +/- 6.3 versus 5.6 +/- 1.7 days (p=0.21), and length of hospital stay 15.3 +/- 8.9 versus 11.2 +/- 3.4 days (p=0.43).

CONCLUSIONS

Use of a symptom-driven protocol was associated with significantly decreased time to symptom control, amount of sedative required, and time spent receiving benzodiazepine infusion compared with historical controls. The use of the protocol is effective but requires close monitoring to ensure protocol compliance and to avoid potential propylene glycol toxicity.

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.

UK drug analysis prints and anaesthetic adverse drug reactions

PURPOSE

Anaesthetic drugs were selected from the Medicines and Healthcare products Regulatory Agency Drug Analysis Prints in order to determine the number and types of reported reactions and associated mortality.

METHODS

The chosen drug groups were the intravenous induction agents, the neuromuscular blocking drugs and neostigmine, the inhalational anaesthetic agents and nitrous oxide, local anaesthetic agents and a selection of analgesics agents, naloxone and midazolam and its antagonist flumazenil. From each drug file, the number and type of reactions were analysed. Mortality was calculated as a percentage of the number of deaths against patient reports.

RESULTS

A total of 11,199 reactions were analysed from 6603 patients of whom 620 (9%) died. Few drug records reported reactions from multiple constituent formulations. The majority of reactions were not allergic. The highest mortality was in the inhalational anaesthetic group. Although the greatest number of fatal events was associated with halothane, this drug is no longer used. Nevertheless the percentage remains high because cardiovascular mortality is still being reported. Local anaesthetic use was associated with the smallest percentage mortality (3%). The highest reported number of reactions was associated with the intravenous induction agents and idiosyncratic neurological and peripheral vascular reactions were linked with the use of etomidate.

CONCLUSIONS

The reporting of allergic reactions was low. The data demonstrate that induction of anaesthesia presents the highest risk of adverse drug reaction; there is also mortality from newer drugs for example, desflurane, remifentanil as well as from drugs for which there is no alternative, for example, suxamethonium.

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.

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.

Propylene Glycol Toxicity: A Severe Iatrogenic Illness in ICU Patients Receiving IV Benzodiazepines

STUDY OBJECTIVES

Benzodiazepines are commonly administered to medical ICU (MICU) patients. Propylene glycol (1,2-propanediol) is the solvent used to deliver lorazepam and diazepam IV. Although propylene glycol toxicity is increasingly recognized and reported, its incidence is unknown. Herein, we describe five MICU patients who acquired severe propylene glycol toxicity due to IV lorazepam or diazepam administration. Additionally, we evaluate the incidence of propylene glycol toxicity in MICU patients receiving IV lorazepam or diazepam.

DESIGN

Case series and prospective, observational study.

SETTING

Eighteen-bed MICU in a 550-bed urban academic hospital.

PATIENTS AND METHODS

MICU patients administered IV benzodiazepines during a 3-month period were enrolled. Patients were categorized according to the IV benzodiazepine that they received. Laboratory data and highlights of their clinical course were recorded daily. The incidence of propylene glycol toxicity was determined and the groups compared.

RESULTS

Forty-four patients were enrolled. Twenty-one patients received a benzodiazepine delivered in propylene glycol (lorazepam or diazepam), and 23 patients received a benzodiazepine delivered in an alternative solvent (midazolam). We found that four patients (19%) who received IV lorazepam or diazepam had metabolic evidence of propylene glycol toxicity. None of the patients had clinical deterioration. Neither metabolic abnormality nor clinical deterioration suggestive of propylene glycol toxicity were identified in subjects receiving IV midazolam.

CONCLUSION

Propylene glycol toxicity is a potentially life-threatening iatrogenic complication that is common and preventable. It should be considered whenever a patient has an unexplained anion gap, unexplained metabolic acidosis, hyperosmolality, and/or clinical deterioration. Close monitoring of all patients receiving IV lorazepam or diazepam for early evidence of propylene glycol toxicity is warranted.

Relationship of continuous infusion lorazepam to serum propylene glycol concentration in critically ill adults*

OBJECTIVES

The primary objective was to evaluate the relationship between high-dose lorazepam and serum propylene glycol concentrations. Secondary objectives were a) to document the occurrence of propylene glycol accumulation associated with continuous high-dose lorazepam infusion; b) to assess the relationship between lorazepam dose, serum propylene glycol concentrations, and propylene glycol accumulation; and c) to assess the relationship between the osmol gap and serum propylene glycol concentrations.

DESIGN

Prospective, observational study.

SETTING

Tertiary care, medical intensive care unit.

PATIENTS

Nine critically ill adults receiving high-dose lorazepam (> or =10 mg/hr) infusion.

INTERVENTIONS

Cumulative lorazepam dose (mg/kg) and the rate of infusion (mg.kg(-1).hr(-1)) were monitored from initiation of lorazepam infusion until 24 hrs after discontinuation of the high-dose lorazepam infusion. Serum osmolarity was collected at 48 hrs into the high-dose lorazepam infusion and daily thereafter. Serum propylene glycol concentrations were drawn at 48 hrs into the high-dose lorazepam infusion, and the presence of propylene glycol accumulation, as evidenced by a high anion gap (> or =15 mmol/L) metabolic acidosis with elevated osmol gap (> or =10 mOsm/L), was assessed at that time.

MEASUREMENTS AND MAIN RESULTS

The mean cumulative high-dose lorazepam received and mean high-dose lorazepam infusion rate were 8.1 mg/kg (range, 5.1-11.7) and 0.16 mg.kg(-1).hr (-1)(range, 0.11-0.22), respectively. A significant correlation between high-dose lorazepam infusion rate and serum propylene glycol concentrations was observed (r =.557, p =.021). Osmol gap was the strongest predictor of serum propylene glycol concentrations (r =.804, p =.001). Propylene glycol accumulation was observed in six of nine patients at 48 hrs. No significant correlation between duration of lorazepam infusion and serum propylene glycol concentrations was observed (p =.637).

CONCLUSION

Propylene glycol accumulation, as reflected by a hyperosmolar anion gap metabolic acidosis, was observed in critically ill adults receiving continuous high-dose lorazepam infusion for > or =48 hrs. Study findings suggest that in critically ill adults with normal renal function, serum propylene glycol concentrations may be predicted by the high-dose lorazepam infusion rate and osmol gap.

Propylene Glycol–Associated Renal Toxicity from Lorazepam Infusion

OBJECTIVES

Using data from patients who developed elevations in serum creatinine concentrations while receiving continuous-infusion lorazepam, we sought to determine the correlations between the magnitude of serum creatinine concentration rise and each of the following variables: serum propylene glycol level, cumulative lorazepam dose, and duration of lorazepam administration. An additional objective was to identify clinical markers for propylene glycol toxicity.

DESIGN

Retrospective chart review.

SETTING

Medical-surgical intensive care unit and burn unit at a university hospital.

PATIENTS

Eight patients who developed elevations in serum creatinine concentrations while receiving continuous-infusion lorazepam (range 2-28 mg/hr).

MEASUREMENTS AND MAIN RESULTS

The mean cumulative dose of lorazepam was 4305 mg (range 1200-10,920 mg), and the mean propylene glycol level determined at the time of peak serum creatinine concentration was 1103 microg/ml (range 186-3450 microg/ml). Serum creatinine concentrations increased in all eight patients during lorazepam infusion and decreased in seven within 3 days after stopping infusion. A weak-to-moderate correlation existed between the magnitude of the rise in serum creatinine concentration and propylene glycol level (r=0.53). A weak-to-moderate correlation also was identified between cumulative lorazepam dose and magnitude of serum creatinine concentration rise (r=0.43), and a strong-to-moderate correlation was found between duration of lorazepam infusion and magnitude of serum creatinine concentration rise (r=0.60). Propylene glycol levels were strongly correlated with both serum osmolality and osmol gap.

CONCLUSION

The patients' increased serum creatinine concentrations are likely to have resulted from exposure to propylene glycol as a result of lorazepam infusion. Serum osmolality and osmol gap may be useful markers for propylene glycol toxicity.

An Unusual Case of Poisoning

The case of a 49-year-old alcoholic man with obtundation is presented. The patient was presumptively diagnosed with methanol intoxication due to the presence of metabolic acidosis with high anion and osmolar gaps. Laboratory testing revealed toxic levels of propylene glycol instead. An exercise in estimating the concentration of toxic alcohols and glycols is given, and the literature on poisoning with this unusual but commonly encountered intoxicant is briefly reviewed.

Acute Tubular Necrosis Associated with Propylene Glycol from Concomitant Administration of Intravenous Lorazepam and Trimethoprim-Sulfamethoxazole

A 46-year-old morbidly obese man was admitted to the medical intensive care unit with respiratory failure. He required pressure-control ventilation and high levels of sedation with continuous-infusion lorazepam. He developed Stenotrophomonas maltophilia pneumonia; treatment included scheduled intravenous trimethoprim-sulfamethoxazole. Each of these drugs contain several hundred milligrams/milliliter of propylene glycol. On day 17 of his hospital course, 3 days after starting the trimethoprim-sulfamethoxazole, the patient developed acute renal failure consistent with acute tubular necrosis. Propylene glycol toxicity was suspected; therefore, all drugs containing propylene glycol were discontinued, and laboratory data were collected. A marked osmol gap, metabolic acidosis, and renal toxicity were attributed to both continuous and large intermittent doses of intravenous propylene glycol. Particular attention should be paid to the total amount of propylene glycol provided to patients from administered drugs. Patients in the intensive care setting who require high doses of intravenous lorazepam for sedation, as well as antimicrobial therapy with trimethoprim-sulfamethoxazole for treatment of either Stenotrophomonas maltophilia or Pneumocystis carinii pneumonia, may be at increased risk for propylene glycol toxicity and should be monitored closely.