Carboxyhemoglobin half-life toxicokinetic profiles during and after normobaric oxygen therapy: On a swine model

Investigations on acute carbon monoxide (CO) poisoning struggle to highlight a relevant discriminant criterion related to CO poisoning severity for predicting complications, such as delayed neurological syndromes. In this context, it remains difficult to demonstrate the superiority of one method of oxygen (O2) administration over others or to identify the optimal duration of normobaric 100% oxygen (NBO) treatment. Myoglobin, as hemoglobin, are a potential binding site for CO, which could be a source of extravascular CO storage that impacts the severity of CO poisoning. It is not possible in routine clinical practice to estimate this potential extravascular CO storage. Indirect means of doing so that are available in the first few hours of poisoning could include, for example, the carboxyhemoglobin half-life (COHbt1/2), which seems to be influenced itself by the level and duration of CO exposure affecting this store of CO within the body. However, before the elimination of CO can be assessed, the COHbt1/2 toxicokinetic model must be confirmed: research still debates whether this model mono- or bi-compartmental. The second indirect mean could be the assessment of a potential COHb rebound after COHb has returned to 5% and NBO treatment has stopped. Moreover, a COHb rebound could be considered to justify the duration of NBO treatment. On an experimental swine model exposed to moderate CO poisoning (940 ppm for ±118 min until COHb reached 30%), we first confirm that the COHb half-life follows a bi-compartmental model. Secondly, we observe for the first time a slight COHb rebound when COHb returns to 5% and oxygen therapy is stopped. On the basis of these two toxicokinetic characteristics in favor of extravascular CO storage, we recommend that COHbt1/2 is considered using the bi-compartmental model in future clinical studies that compare treatment effectiveness as a potential severity criterion to homogenize cohorts of the same severity. Moreover, from a general toxicokinetic point of view, we confirm that a treatment lasting less than 6 hours appears to be insufficient for treating moderate CO poisoning.

Long-term intensive care unit outbreak of carbapenemase-producing organisms associated with contaminated sink drains

BACKGROUND

Between 2018 and 2022, a Belgian tertiary care hospital faced a growing issue with acquiring carbapenemase-producing organisms (CPO), mainly VIM-producing P. aeruginosa (PA-VIM) and NDM-producing Enterobacterales (CPE-NDM) among hospitalized patients in the adult intensive care unit (ICU).

AIM

To investigate this ICU long-term CPO outbreak involving multiple species and a persistent environmental reservoir.

METHODS

Active case finding, environmental sampling, whole-genome sequencing (WGS) analysis of patient and environmental strains, and implemented control strategies were described in this study.

FINDINGS

From 2018 to 2022, 37 patients became colonized or infected with PA-VIM and/or CPE-NDM during their ICU stay. WGS confirmed the epidemiological link between clinical and environmental strains collected from the sink drains with clonal strain dissemination and horizontal gene transfer mediated by plasmid conjugation and/or transposon jumps. Environmental disinfection by quaternary ammonium-based disinfectant and replacement of contaminated equipment failed to eradicate environmental sources. Interestingly, efflux pump genes conferring resistance to quaternary ammonium compounds were widespread in the isolates. As removing sinks was not feasible, a combination of a foaming product degrading the biofilm and foaming disinfectant based on peracetic acid and hydrogen peroxide has been evaluated and has so far prevented recolonization of the proximal sink drain by CPO.

CONCLUSION

The persistence in the hospital environment of antibiotic- and disinfectant-resistant bacteria with the ability to transfer mobile genetic elements poses a serious threat to ICU patients with a risk of shifting towards an endemicity scenario. Innovative strategies are needed to address persistent environmental reservoirs and prevent CPO transmission.

Erratum to: 36th International Symposium on Intensive Care and Emergency Medicine: Brussels, Belgium. 15-18 March 2016

[This corrects the article DOI: 10.1186/s13054-016-1208-6.].

Formate kinetics in methanol poisoning

Objective: The objective is to describe the kinetics of formate, the main toxic metabolite of methanol, in a series of consecutive patients treated in the same intensive care unit for severe methanol poisoning. Methods: The charts of the patients admitted between 1987 and 2001 were reviewed. Inclusion criteria were: a history of deliberate methanol ingestion, with a blood methanol concentration greater than 20 mg/dL (6.2 mmol/L) or a high anion gap metabolic acidosis. Indications for hemodialysis were: blood methanol concentration>50 mg/dL (15.8 mmol/L), metabolic acidosis (bicarbonate < 15 mmol/L, arterial pH < 7.30), visual toxicity. Antidotal therapy included ethanol administration in 22 cases, and fomepizole in three cases. Serial blood measurements were obtained for pH, bicarbonate, methanol and formate. Endogenous and hemodialysis elimination half-lives were calculated as t1/2=0.693/Ke. Fick principle was applied for hemodialysis clearance calculation. Results: The records of 25 methanol poisoned patients were analysed. Among them, 18 patients had sufficient data to allow accurate determinations of formate kinetics. Formate half-life elimination during hemodialysis was 1.809 ± 0.78 h, which was statistically different from the values observed before or in the absence of dialysis (6.049 ± 3.26 h, P=0.004). The mean hemodialysis formate clearance rate calculated in eight cases was 1769 ± 43 mL/min. A rebound in plasma formate concentration was observed in three patients after the discontinuation of hemodialysis. Conclusions: In accordance with previous isolated case reports and in contrast with a recent case series, our data document that hemodiaysis is effective in reducing formate elimination half-life. The impact on clinical outcome is still debatable.

Pink urine

A 55-year-old man was admitted after a suspected hypnotic overdose of valerian extracts. In addition to altered consciousness, the first clinical symptoms included not only diffuse rash on the face, trunk, and limbs, but also an inspiratory dyspnea with a marked hypoxemia. A major laryngeal edema was noted during orotracheal intubation. After correction of hypoxemia, the patient became agitated and propofol was administered by continuous infusion. In addition, the patient passed pink urine staining the urine collection bag. The presence of an unidentified toxic substance was suspected.

Spontaneous pneumomediastinum and epidural pneumatosis after oral ecstasy consumption

A 19-year-old man was admitted with acute dyspnoea. Physical examination revealed subcutaneous emphysema in the cervical and thoracic area. This was further confirmed by the total body computed tomography that also demonstrated mediastinal emphysema. Epidural pneumatosis of the thoracis spine was also evident. There was no history of trauma, but well of a recent oral ecstasy consumption during a techno rave party, associated with intense dancing and jumping. Clinical course was favourable with conservative therapy.

Pregabalin-associated myoclonic encephalopathy without evidence of drug accumulation in a patient with acute renal failure

Pregabalin, used for treating partial epilepsy and neuropathic pain, is usually well tolerated. Patients with impaired renal function are at risk to develop more serious adverse events. A 64-year-old woman was admitted in the Emergency Department for altered consciousness and abnormal movements. She recently started to take pregabalin (150 mg/day) for neuropathic pain. The drug was withdrawn 36 h before hospitalization following worsening of neurological symptoms. At physical examination, myoclonus was noted as main finding in the limbs and head, with encephalopathy. Laboratory investigations revealed acute renal failure with serum creatinine at 451.3 μmol/l. Urine output was preserved. After supportive care alone, myoclonus resolved after 24 h and consciousness was normal after 48 h. Renal function was also recovered. At the time of admission, the concentration of plasma pregabalin was 3.42 μg/ml, within therapeutic range. The calculated terminal elimination half-life was 11.5 h. Pregabalin-induced myoclonus may not be strictly related to drug accumulation in acute renal failure, with the possibility of a threshold phenomenon.

Refractory hypercapnia: a simplified technique for extracorporeal CO2 removal (ECCO2R) in the presence of therapeutic limitations

Refractory hypercapnia with severe acidosis appeared in a 67-year-old man who presented with lung fibrosis and a left pneumothorax as delayed complications of bleomycin chemotherapy for advanced grade lymphoma. Due to failure of noninvasive ventilation using a high-flow nasal cannula oxygen system, the patient was mechanically ventilated with two ventilators at different settings, after intubation with a double-lumen tube. As he had a poor haematological prognosis, extracorporeal membranous oxygenation was not considered. To remove some amount of carbon dioxide, we used a simplified method based on a veno-venous hemofiltration circuit coupled to a paediatric oxygenator and an air/oxygen blender. The efficacy on carbon dioxide removal was modest, with a percentage of CO2 total extraction ranging from 10.5 to 20.4%, but the system was immediately available, well tolerated and not very expensive.

Locked-in syndrome as an unusual complication of acute otitis media

BACKGROUND

A 32-year-old woman developed altered consciousness two days after initial symptoms of acute otitis media, with purulent discharge from the right ear. She was quadriplegic, with spontaneous eye opening, mild neck stiffness, and lacking vestibular-ocular reflexes.

METHODOLOGY

Upon admission, the patient was subjected to brain computed tomography (CT), magnetic resonance imaging (MRI), and lumbar puncture.

RESULTS

CT was consistent with pansinusitis, right middle ear otitis, mastoiditis, and sphenoiditis. No brainstem lesion was evident; brain MRI demonstrated ischemic and secondary hemorrhagic lesions in the pons and cerebral peduncles. The dura mater in the petroclival space was intensely inflamed, and likely responsible for reduced basilar arterial blood flow. Lumbar puncture yielded clear cerebrospinal fluid; gram stain examination was negative and culture remained sterile. Streptococcus pneumoniae and Haemophilus influenzae were cultured from the purulent ear discharge.

CONCLUSION

The final diagnosis was locked-in syndrome consecutive to inflammatory changes compressing the basilar artery.

Toxicokinetic interaction between quetiapine and antiretroviral therapy following quetiapine overdose

A 47-year-old woman ingested an overdose of 8000 mg quetiapine. The treatment had been initiated 3 weeks before. The current medications were lamuvidine, ritonavir, atazanavir and tenofovir for an HIV infection. The patient presented a deep coma and sustained hypotension as main complications. The toxicokinetic data revealed a markedly prolonged elimination half-life for quetiapine (62.4 hours) and the relationship with antiretroviral therapy is discussed.

Reversible splenial lesion syndrome in cerebral malaria

A 71-year-old Caucasian man living in Congo was investigated by serial magnetic resonance imaging (MRI) after having presented cerebral malaria due to Plasmodium falciparum. The clinical picture was characterized initially by coma and seizures. The patient developed multiple organ failure. There was, at 4 months follow-up only, a minimal neurological improvement consistent with minimally conscious state. The first cerebral MRI on day 17 showed a lesion of the splenium of corpus callosum with high signal intensity on DWI and FLAIR sequence and reduced ADC, and small cortical infarcts in the internal occipital regions. Follow-up MRI obtained 36 days later showed a complete resolution of splenial lesion, though without clinical improvement. Cerebral malaria should be added to the list of possible causes of reversible lesion of the splenium of corpus callosum.

Non-heart-beating donor, renewal of an old procedure: a Belgian experience

The shortage of donated organs has become a problem in transplantation throughout the world. Transplant teams are looking for other ways to increase and improve the donor pool. Non-heart-beating donation may be a source to increase the number of donors, even if some technical, logistical, and emotional problems are encountered. The results obtained by our team should stimulate other centers to implement this kind of donation in their hospitals. We describe our experience in the policy of non-heart-beating donation and encourage transplant centers to develop such a program.

An unusual cause of abdominal pain

A 36-year-old woman presented to the Emergency Room because of abdominal pain associated with hematuria and red blood blending to stool. On admission, the physical examination revealed abdominal tenderness and diffuse cutaneous hematoma. The laboratory findings showed abnormal clotting tests with high International Normalised Ratio (INR) and prolonged activated partial thromboplastin time. Hemoperitoneum and ureteral hematoma were noted on the abdomen computed tomography. The patient confessed she had ingested difenacoum for several weeks. All the symptoms resolved with fresh frozen plasma perfusion and vitamin K.

Treatment of acute methanol poisoning with fomepizole

OBJECTIVE

To assess the efficacy and safety of fomepizole, a competitive alcohol dehydrogenase inhibitor, in methanol poisoning and to test the hypothesis that fomepizole obviates the need for hemodialysis in selected patients.

DESIGN AND SETTING

Retrospective clinical study in three intensive care units in university-affiliated teaching hospitals.

PATIENTS

All methanol-poisoned patients admitted to these ICUs and treated with fomepizole from 1987-1999 (n=14).

MEASUREMENTS AND RESULTS

The median plasma methanol concentration was 50 mg/dl (range 4-146), anion gap 22.1 mmol/l (11.8-42.2), arterial pH 7.34 (7.11-7.51), and bicarbonate 17.5 mmol/l (3.0-25.0). Patients received oral or intravenous fomepizole until blood methanol was undetectable. The median cumulative dose was 1250 mg (500-6000); the median number of twice daily doses was 2 (1-16). Four patients underwent hemodialysis for visual impairment present on admission. Four patients with plasma methanol concentrations of 50 mg/dl or higher and treated without hemodialysis recovered fully. Patients without pretreatment visual disturbances recovered, with no sequelae in any case. There were no deaths. Fomepizole was safe and well tolerated, even in the case of prolonged treatment. Analysis of methanol toxicokinetics in five patients demonstrated that fomepizole was effective in blocking methanol's toxic metabolism.

CONCLUSIONS

Fomepizole appears safe and effective in the treatment of methanol-poisoned patients. If our results are confirmed in prospective analyses, hemodialysis may prove unnecessary in patients presenting without visual impairment or severe acidosis.

Fomepizole (orphan medical)

Orphan Medical has developed fomepizole as a potential treatment for both ethylene glycol and methanol poisoning. The drug was launched as Antizol in January 1998 for the treatment of ethylene glycol poisoning [273949] after US marketing approval was grantedin December 1997 [271563]. It has also received US approval for methanol poisoning [393217] and UK approval for ethylene glycol poisoning [329495]. In 1999, Orphan Medical's partner, Cambridge Laboratories, intended to pursue European approval under the mutual recognition procedure [329495]. However, by September 2000, Cambridge Laboratories had discontinued their involvement with fomepizole and IDIS World Medicines had licensed the rights to distribute the drug in the UK [412142]. In February 2000, the Canadian Therapeutic Products Programme (TPP) granted fomepizole Priority Review, provided that an NDA was submitted by March 14, 2000 [354665]. In August 2000, the TPP accepted this NDA and set a target date for approval in the fourth quarter of 2000 [379474]. The TPP granted fomepizole a Notice of Compliance permitting the sale of fomepizole in Canada in December 2000. The company's marketing partner in Canada, Paladin Labs had launched fomepizole by January 2001 [396953]. In June 2000, Tucker Anthony Cleary Gull stated that the Orphan Drug status which Orphan Medical had obtained for fomepizole would provide marketing exclusivity through December 2004. The analysts also stated that fomepizole had accounted for 40% of Orphan Medical's revenue in financial year 1999, although +/- 30% of sales were estimated to be due to stockpiling [409606].

Determination of formic acid tissue and fluid concentrations in three fatalities due to methanol poisoning

Three fatalities caused by methanol ingestion are reported. Admission blood methanol concentrations ranged from 0.28 to 4.6 g/L. Two patients had been admitted after a significant delay (>20 hours), and one patient was observed within 90 minutes following ingestion. Formic acid levels were determined in blood samples at admission and ranged from 302 to 680 mg/L. The patients died 44, 55, and 82 hours after poisoning. Formic acid determinations in postmortem tissues were performed by a gas chromatograph method. The authors found great variability in formic acid distribution among the patients and among organs.

Spontaneous haemoperitoneum from surreptitious ingestion of a rodenticide

Superwarfarins have progressively replaced warfarin as rodenticides as they are more potent and have a longer anticoagulant activity. Human exposure may be complicated by spontaneous haemorrhage in various sites. We report the case of a 51-year-old woman who was admitted with spontaneous haemoperitoneum and intramural haematoma along the small intestine. After the evidence of a deficit of vitamin K1-dependent clotting factors (II, VII, IX, X), the patient admitted that she was chronically ingesting difenacoum. She was successfully treated with fresh frozen plasma and vitamin K1. Follow-up was not accepted.