Influence of the anesthetic 2,6-diisopropylphenol on the oxidative phosphorylation of isolated rat liver mitochondria

Overdose with the anesthetic propofol causes hematological cytotoxicity and immune cell alteration in an experimental ex vivo whole blood culture model

Propofol, an anesthetic characterized by its benefits of rapid induction, maintenance, and recovery times, may cause cytotoxic effects, resulting in propofol infusion syndrome (PRIS). In addition to causing dyslipidemia in PRIS, our previous works showed that propofol overdose induced phagocyte apoptosis. This study, using an experimental ex vivo model of propofol treatment, investigated the possible cytopathology in the blood. A complete blood count examination showed the deregulating effects of propofol overdose 24 h postinoculation, characterized by mononuclear cell increase (lymphocyte and monocyte subsets) and granulocyte decrease. Advanced marker-based flow cytometric analysis confirmed these findings, although there was no change in CD14+ monocytes. Blood smear staining showed the deregulating effects of propofol overdose 24 h postinoculation, characterized by cytosolic vacuolization and cytotoxicity, particularly in neutrophils. Immune cell profiling of caspase-3 activation demonstrated the induction of cell apoptosis following propofol overdose treatment, particularly in granulocytes. Using multiparameter flow cytometry, this study further analyzed the changes in the profile of immune cells, showing a notable increase in CD4 + HLA-DR-CD62L- helper T cells. These studies explored an ex vivo model of cytopathogenic propofol overdose and its special immune-deregulating effects on peripheral blood cells.

Association between first-week propofol administration and long-term outcomes of critically ill mechanically ventilated patients: A retrospective cohort study

BACKGROUND & AIM

Propofol is commonly used in ICUs, but its long-term effects have not been thoroughly studied. In vitro studies suggest it may harm mitochondrial function, potentially affecting clinical outcomes. This study aimed to investigate the association between substantial propofol sedation and clinical outcomes in critically ill patients.

METHODS

We conducted a single-centre cohort study of critically ill, mechanically ventilated (≥7 days) adults to compare patients who received a substantial dose of propofol (cumulative >500 mg) during the first week of ICU admission with those who did not. The primary outcome was the association between substantial propofol administration and 6-month mortality, adjusted for relevant covariates. Subanalyses were performed for administration in the early (day 1-3) and late (day 4-7) acute phases of critical illness due to the metabolic changes in this period. Secondary outcomes included tracheostomy need and duration, length of ICU and hospital stay (LOS), discharge destinations, ICU, hospital, and 3-month mortality.

RESULTS

A total of 839 patients were enrolled, with 73.7 % receiving substantial propofol administration (substantial propofol dose group). Six-month all-cause mortality was 32.4 %. After adjusting for relevant variables, we found no statistically significant difference in 6-month mortality between both groups. There were also no significant differences in secondary outcomes.

CONCLUSION

Our study suggests that substantial propofol administration during the first week of ICU stay in the least sick critically ill, mechanically ventilated adult patients is safe, with no significant associations found with 6-month mortality, ICU or hospital LOS, differences in discharge destinations or need for tracheostomy.

A Commentary on the Effect of Targeted Temperature Management in Patients Resuscitated from Cardiac Arrest

The members of the International Liaison Committee on Resuscitation (ILCOR) Advanced Life Support Task Force have written a comprehensive summary of trials of the effectiveness of induced hypothermia (IH) or targeted temperature management (TTM) in comatose patients after cardiac arrest (CA). However, in-depth analysis of these studies is incomplete, especially since there was no significant difference in primary outcome between hypothermia versus normothermia in the recently reported TTM2 trial. We critically appraise trials of IH/TTM versus normothermia to characterize reasons for the lack of treatment effect, based on a previously published framework for what to consider when the primary outcome fails. We found a strong biologic rationale and external clinical evidence that IH treatment is beneficial. Recent TTM trials mainly included unselected patients with a high rate of bystander cardiopulmonary resuscitation. The treatment was not applied as intended, which led to a large delay in achievement of target temperature. While receiving intensive care, sedative drugs were likely used that might have led to increased neurologic damage as were antiplatelet drugs that could be associated with increased acute stent thrombosis in hypothermic patients. It is reasonable to still use or evaluate IH treatment in patients who are comatose after CA as there are multiple plausible reasons why IH compared to normothermia did not significantly improve neurologic outcome in the TTM trials.

Therapeutic Hypothermia Following Cardiac Arrest After the TTM2 trial - More Questions Raised Than Answered

For almost 20 years, therapeutic hypothermia has been a cornerstone of modern post-cardiac arrest care lowering mortality, and improvin neurologic outcome compared to conventional therapy. This was challenged by the first TTM-trial in 2013, which did not show a benefit for hypothermia at 33°C compared to controlled normothermia at 36°C. Now, the TTM2 trial showed no benefit of hypothermia compared to fever prevention alone. While TTM1 and TTM2 suggest that hypothermia might not be helpful, a deep dive into the trials reveals that this conclusion does not hold true. Here, we focus on patient selection, suboptimal application of hypothermia, interaction of standard sedation with hypothermia, high incidence of post-arrest fever, and withdrawal of life support based on per-protocol neurologic prognostication in the TTM2-trial. Of particular interest, contemporary trials and registries using intravascular cooling in TTM-like patients repeatedly reported much lower mortality rates than those described in both TTM1 and TTM2.

Effect of noradrenaline on propofol-induced mitochondrial dysfunction in human skeletal muscle cells

Background

Mitochondrial dysfunction is a hallmark of both critical illness and propofol infusion syndrome and its severity seems to be proportional to the doses of noradrenaline, which patients are receiving. We comprehensively studied the effects of noradrenaline on cellular bioenergetics and mitochondrial biology in human skeletal muscle cells with and without propofol-induced mitochondrial dysfunction.

Methods

Human skeletal muscle cells were isolated from vastus lateralis biopsies from patients undergoing elective hip replacement surgery (n = 14) or healthy volunteers (n = 4). After long-term (96 h) exposure to propofol (10 µg/mL), noradrenaline (100 µM), or both, energy metabolism was assessed by extracellular flux analysis and substrate oxidation assays using [14C] palmitic and [14C(U)] lactic acid. Mitochondrial membrane potential, morphology and reactive oxygen species production were analysed by confocal laser scanning microscopy. Mitochondrial mass was assessed both spectrophotometrically and by confocal laser scanning microscopy.

Results

Propofol moderately reduced mitochondrial mass and induced bioenergetic dysfunction, such as a reduction of maximum electron transfer chain capacity, ATP synthesis and profound inhibition of exogenous fatty acid oxidation. Noradrenaline exposure increased mitochondrial network size and turnover in both propofol treated and untreated cells as apparent from increased co-localization with lysosomes. After adjustment to mitochondrial mass, noradrenaline did not affect mitochondrial functional parameters in naïve cells, but it significantly reduced the degree of mitochondrial dysfunction induced by propofol co-exposure. The fatty acid oxidation capacity was restored almost completely by noradrenaline co-exposure, most likely due to restoration of the capacity to transfer long-chain fatty acid to mitochondria. Both propofol and noradrenaline reduced mitochondrial membrane potential and increased reactive oxygen species production, but their effects were not additive.

Conclusions

Noradrenaline prevents rather than aggravates propofol-induced impairment of mitochondrial functions in human skeletal muscle cells. Its effects on bioenergetic dysfunctions of other origins, such as sepsis, remain to be demonstrated.

Propofol Infusion Syndrome: A Rare Complication From a Common Medication

Propofol infusion syndrome (PRIS) is a multifactorial condition that, upon propofol administration, can interrupt critical cellular processes. This can lead to cellular damage that translates as multi-organ system failure that has the potential to be life-threatening. Due to the rarity of this condition, we report a case of PRIS in a 46-year-old male to help bring awareness to this severe condition caused by a relatively common medication. This patient was brought in due to unresponsiveness secondary to multi-substance abuse and respiratory disease and initially had elevated creatinine kinase levels that eventually subsided with appropriate management. However, after prolonged infusion of propofol, his creatinine kinase levels began to drastically rise, alluding to the development of propofol infusion syndrome. Once the offending agent was discontinued, the patient's creatinine kinase levels once again began to normalize.

Propofol-Related Infusion Syndrome: A Clinical Review

Propofol-related infusion syndrome (PRIS) is a lethal condition characterized by multiple organ system failures. It can occur due to prolonged administration of propofol (an anesthetic) in mechanically intubated patients. The main presenting features of this condition include cardiovascular dysfunction with particular emphasis on impairment of cardiovascular contractility, metabolic acidosis, lactic acidosis, rhabdomyolysis, hyperkalaemia, lipidaemia, hepatomegaly, acute renal failure, and eventually mortality in most cases. The significant risk factors that predispose one to PRIS are: critical illnesses, increased serum catecholamines, steroid therapy, obesity, young age (significantly below three years), depleted carbohydrate stores in the body, increased serum lipids, and most importantly, heavy or extended dosage of propofol. The primary pathophysiology behind PRIS is the disruption of the mitochondrial respiratory chain that causes inhibition of adenosine triphosphate (ATP) synthesis and cellular hypoxia. Further, excess lipolysis of adipose tissue occurs, especially in critically ill patients where the energy source is lipid breakdown instead of carbohydrates. This process generates excess free fatty acids (FFAs) that cannot undergo adequate beta-oxidation. These FFAs contribute to the clinical pathology of PRIS. It requires prompt management as it is a fatal condition. The clinicians must observe the patient's electrocardiogram (ECG), serum creatine kinase, lipase, amylase, lactate, liver enzymes, and myoglobin levels in urine, under propofol sedation. Doctors should immediately stop propofol infusion upon noticing any abnormality in these parameters. The other essentials of management of various manifestations of PRIS will be discussed in this article, along with a detailed explanation of the condition, its risk factors, diagnosis, pathophysiology, and presenting features. This article aims to make clinicians more aware of the occurrence of this syndrome so that better ways to manage and treat this condition can be formulated in the future.

Case Report: Sustained mitochondrial damage in cardiomyocytes in patients with severe propofol infusion syndrome

Introduction: Propofol infusion syndrome (PRIS) is rare but a potentially lethal adverse event. The pathophysiologic mechanism is still unknown.

Patient concerns: A 22-year-old man was admitted for the treatment of Guillain-Barré syndrome. On day six, he required mechanical ventilation due to progressive muscle weakness; propofol (3.5 mg/kg/hour) was administered for five days for sedation. On day 13, he had hypotension with abnormal electrocardiogram findings, acute kidney injury, hyperkalemia and severe rhabdomyolysis.

Diagnosis and interventions: The patient was transferred to our intensive care unit (ICU) on suspicion of PRIS. Administration of noradrenaline and renal replacement therapy and fasciotomy for compartment syndrome of lower legs due to PRIS-rhabdomyolysis were performed.

Outcomes: The patient gradually recovered and was discharged from the ICU on day 30. On day 37, he had repeated sinus bradycardia with pericardial effusion in echocardiography. Cardiac ¹⁸F-FDG PET on day 67 demonstrated heterogeneous ¹⁸F-FDG uptake in the left ventricle. Electron microscopic investigation of endomyocardial biopsy on day 75 revealed mitochondrial myelinization of the cristae, which indicated mitochondrial damage of cardiomyocytes. He was discharged without cardiac abnormality on day 192.

Conclusions: Mitochondrial damage in both morphological and functional aspects was observed in the present case. Sustained mitochondrial damage may be a therapeutic target beyond the initial therapy of discontinuing propofol administration.

L-Carnitine and Acylcarnitines: Mitochondrial Biomarkers for Precision Medicine

Biomarker discovery and implementation are at the forefront of the precision medicine movement. Modern advances in the field of metabolomics afford the opportunity to readily identify new metabolite biomarkers across a wide array of disciplines. Many of the metabolites are derived from or directly reflective of mitochondrial metabolism. L-carnitine and acylcarnitines are established mitochondrial biomarkers used to screen neonates for a series of genetic disorders affecting fatty acid oxidation, known as the inborn errors of metabolism. However, L-carnitine and acylcarnitines are not routinely measured beyond this screening, despite the growing evidence that shows their clinical utility outside of these disorders. Measurements of the carnitine pool have been used to identify the disease and prognosticate mortality among disorders such as diabetes, sepsis, cancer, and heart failure, as well as identify subjects experiencing adverse drug reactions from various medications like valproic acid, clofazimine, zidovudine, cisplatin, propofol, and cyclosporine. The aim of this review is to collect and interpret the literature evidence supporting the clinical biomarker application of L-carnitine and acylcarnitines. Further study of these metabolites could ultimately provide mechanistic insights that guide therapeutic decisions and elucidate new pharmacologic targets.

Safety of drug use in patients with a primary mitochondrial disease: An international Delphi-based consensus

Clinical guidance is often sought when prescribing drugs for patients with primary mitochondrial disease. Theoretical considerations concerning drug safety in patients with mitochondrial disease may lead to unnecessary withholding of a drug in a situation of clinical need. The aim of this study was to develop consensus on safe medication use in patients with a primary mitochondrial disease. A panel of 16 experts in mitochondrial medicine, pharmacology, and basic science from six different countries was established. A modified Delphi technique was used to allow the panellists to consider draft recommendations anonymously in two Delphi rounds with predetermined levels of agreement. This process was supported by a review of the available literature and a consensus conference that included the panellists and representatives of patient advocacy groups. A high level of consensus was reached regarding the safety of all 46 reviewed drugs, with the knowledge that the risk of adverse events is influenced both by individual patient risk factors and choice of drug or drug class. This paper details the consensus guidelines of an expert panel and provides an important update of previously established guidelines in safe medication use in patients with primary mitochondrial disease. Specific drugs, drug groups, and clinical or genetic conditions are described separately as they require special attention. It is important to emphasise that consensus-based information is useful to provide guidance, but that decisions related to drug prescribing should always be tailored to the specific needs and risks of each individual patient. We aim to present what is current knowledge and plan to update this regularly both to include new drugs and to review those currently included.

The effects of gasotransmitters inhibition on biochemical and haematological parameters and oxidative stress in propofol-anaesthetized Wistar male rats

This study aimed to investigate the effects of propofol through evaluating its interaction with nitric oxide (NO), hydrogen sulfide (H2S), and carbon monoxide (CO). Wistar male rats were divided in 4 groups: (1) bolus injection of propofol (1% 10 mg/mL, 100 mg/kg bw, i.p.); (2) Nω-nitro-l-arginine methyl ester (L-NAME; NO synthase inhibitor, 60 mg/kg bw, i.p.) + bolus injection of propofol (1% 10 mg/mL, 100 mg/kg bw, i.p.); (3) DL-propargylglycine (DL-PAG; H2S synthase inhibitor, 50 mg/kg bw, i.p.) + bolus injection of propofol (1% 10 mg/mL, 100 mg/kg bw, i.p.); (4) zinc protoporphyrin IX (ZnPPIX; CO synthase inhibitor, 50 μmol/kg bw, i.p.) + bolus injection of propofol (1% 10 mg/mL, 100 mg/kg bw, i.p.). Increased levels of albumins, low-density lipoproteins, alkaline phosphatase, amylase, high-sensitivity Troponin T, and fibrinogen were found in L-NAME + propofol group. Platelet crit, platelet count, total cholesterol, and high-density lipoproteins were elevated in ZnPPIX + propofol group. Hydrogen peroxide was increased in all groups treated with gasotransmitters inhibitors. Reduced glutathione was reduced in all groups, superoxide dismutase activity only in L-NAME + propofol. The effect of propofol on various biochemical, haematological, and oxidative stress markers may be at least in part mediated through interaction with 3 estimated gasotransmitters.

Kinetic characteristics of propofol-induced inhibition of electron-transfer chain and fatty acid oxidation in human and rodent skeletal and cardiac muscles

INTRODUCTION

Propofol causes a profound inhibition of fatty acid oxidation and reduces spare electron transfer chain capacity in a range of human and rodent cells and tissues-a feature that might be related to the pathogenesis of Propofol Infusion Syndrome. We aimed to explore the mechanism of propofol-induced alteration of bioenergetic pathways by describing its kinetic characteristics.

METHODS

We obtained samples of skeletal and cardiac muscle from Wistar rat (n = 3) and human subjects: vastus lateralis from hip surgery patients (n = 11) and myocardium from brain-dead organ donors (n = 10). We assessed mitochondrial functional indices using standard SUIT protocol and high resolution respirometry in fresh tissue homogenates with or without short-term exposure to a range of propofol concentration (2.5-100 μg/ml). After finding concentrations of propofol causing partial inhibition of a particular pathways, we used that concentration to construct kinetic curves by plotting oxygen flux against substrate concentration during its stepwise titration in the presence or absence of propofol. By spectrophotometry we also measured the influence of the same propofol concentrations on the activity of isolated respiratory complexes.

RESULTS

We found that human muscle and cardiac tissues are more sensitive to propofol-mediated inhibition of bioenergetic pathways than rat's tissue. In human homogenates, palmitoyl carnitine-driven respiration was inhibited at much lower concentrations of propofol than that required for a reduction of electron transfer chain capacity, suggesting FAO inhibition mechanism different from downstream limitation or carnitine-palmitoyl transferase-1 inhibition. Inhibition of Complex I was characterised by more marked reduction of Vmax, in keeping with non-competitive nature of the inhibition and the pattern was similar to the inhibition of Complex II or electron transfer chain capacity. There was neither inhibition of Complex IV nor increased leak through inner mitochondrial membrane with up to 100 μg/ml of propofol. If measured in isolation by spectrophotometry, propofol 10 μg/ml did not affect the activity of any respiratory complexes.

CONCLUSION

In human skeletal and heart muscle homogenates, propofol in concentrations that are achieved in propofol-anaesthetized patients, causes a direct inhibition of fatty acid oxidation, in addition to inhibiting flux of electrons through inner mitochondrial membrane. The inhibition is more marked in human as compared to rodent tissues.

Effects of Propofol on Cellular Bioenergetics in Human Skeletal Muscle Cells

OBJECTIVES

Propofol may adversely affect the function of mitochondria and the clinical features of propofol infusion syndrome suggest that this may be linked to propofol-related bioenergetic failure. We aimed to assess the effect of therapeutic propofol concentrations on energy metabolism in human skeletal muscle cells.

DESIGN

In vitro study on human skeletal muscle cells.

SETTINGS

University research laboratories.

SUBJECTS

Patients undergoing hip surgery and healthy volunteers.

INTERVENTIONS

Vastus lateralis biopsies were processed to obtain cultured myotubes, which were exposed to a range of 1-10 μg/mL propofol for 96 hours.

MEASUREMENTS AND MAIN RESULTS

Extracellular flux analysis was used to measure global mitochondrial functional indices, glycolysis, fatty acid oxidation, and the functional capacities of individual complexes of electron transfer chain. In addition, we used [1-C]palmitate to measure fatty acid oxidation and spectrophotometry to assess activities of individual electron transfer chain complexes II-IV. Although cell survival and basal oxygen consumption rate were only affected by 10 μg/mL of propofol, concentrations as low as 1 μg/mL reduced spare electron transfer chain capacity. Uncoupling effects of propofol were mild, and not dependent on concentration. There was no inhibition of any respiratory complexes with low dose propofol, but we found a profound inhibition of fatty acid oxidation. Addition of extra fatty acids into the media counteracted the propofol effects on electron transfer chain, suggesting inhibition of fatty acid oxidation as the causative mechanism of reduced spare electron transfer chain capacity. Whether these metabolic in vitro changes are observable in other organs and at the whole-body level remains to be investigated.

CONCLUSIONS

Concentrations of propofol seen in plasma of sedated patients in ICU cause a significant inhibition of fatty acid oxidation in human skeletal muscle cells and reduce spare capacity of electron transfer chain in mitochondria.

Propofol improves colonic but impairs hepatic mitochondrial function in tissue homogenates from healthy rats

Evidence suggests that propofol infusion syndrome (PRIS) is caused by an altered mitochondrial function. The aim of this study was to examine the effects of propofol and the vehicle MCT on mitochondrial function in hepatic and colonic tissue. Mitochondrial oxygen consumption was determined in colon and liver homogenates after incubation with buffer (control), propofol (50, 75, 100, 500  μM) or the carrier substances DMSO and MCT. State 2 (substrate-dependent) and state 3 (ADP-dependent respiration) were assessed. RCI (respiratory control index) - an indicator for coupling between electron transport chain system (ETS) and oxidative phosphorylation (OXPHOS) and ADP/O ratio - a parameter for efficacy of OXPHOS were calculated. Data were presented as % of control. In hepatic mitochondria, 500  μM propofol reduced RCI formulation-independently (propofol/MCT 500 μM: complex I: 66.3 ± 8.7%*, complex II: 75.5 ± 9.2%*; propofol/DMSO 500 μM: complex I: 29.1 ± 8.8%*, complex II: 49.3 ± 15.5%*). 75  μM Propofol/MCT reduced ADP/O for complex I (73.5 ± 27.3%*). DMSO did not affect hepatic mitochondria whereas MCT reduced RCI for complex II (87.2 ± 9.8%*) and ADP/O for complex I (93.7 ± 31.7%*). In colon 50  μM Propofol/MCT increased RCI for complex I and II (complex I: 127.2 ± 10.7%*, complex II: 136.8 ± 33.9%*) and 100  μM Propofol/MCT for complex I (131.4 ± 18.7%*). 500  μM Propofol/DMSO increased ADP/O for complex I (139.4 ± 41.4%*). DMSO did not affect RCI but increased ADP/O for both complexes (complex I: 119.9 ± 25.8%*, complex II: 110.2 ± 14.2%*). MCT increased RCI for complex I (123.0 ± 31.6%*). In hepatic mitochondria propofol uncoupled ETS from OXPHOS formulation-independently and propofol/MCT reduced efficacy of OXPHOS. In colonic mitochondria, propofol/MCT strengthened the coupling and propofol/DMSO enhanced the efficacy of OXPHOS.

Propofol induces a metabolic switch to glycolysis and cell death in a mitochondrial electron transport chain-dependent manner

The intravenous anesthetic propofol (2,6-diisopropylphenol) has been used for the induction and maintenance of anesthesia and sedation in critical patient care. However, the rare but severe complication propofol infusion syndrome (PRIS) can occur, especially in patients receiving high doses of propofol for prolonged periods. In vivo and in vitro evidence suggests that the propofol toxicity is related to the impaired mitochondrial function. However, underlying molecular mechanisms remain unknown. Therefore, we investigated effects of propofol on cell metabolism and death using a series of established cell lines of various origins, including neurons, myocytes, and trans-mitochondrial cybrids, with defined mitochondrial DNA deficits. We demonstrated that supraclinical concentrations of propofol in not less than 50 μM disturbed the mitochondrial function and induced a metabolic switch, from oxidative phosphorylation to glycolysis, by targeting mitochondrial complexes I, II and III. This disturbance in mitochondrial electron transport caused the generation of reactive oxygen species, resulting in apoptosis. We also found that a predisposition to mitochondrial dysfunction, caused by a genetic mutation or pharmacological suppression of the electron transport chain by biguanides such as metformin and phenformin, promoted propofol-induced caspase activation and cell death induced by clinical relevant concentrations of propofol in not more than 25 μM. With further experiments with appropriate in vivo model, it is possible that the processes to constitute the molecular basis of PRIS are identified.

Encephalopathy associated with propofol infusion syndrome: A case report

INTRODUCTION

Propofol infusion syndrome (PRIS) is a rare but potentially fatal complication of propofol infusion. It is clinically characterized by metabolic acidosis, refractory bradycardia, rhabdomyolysis, renal failure, hyperlipidemia, and hepatomegaly. Brain lesion was only reported once in a pediatric patient. We present the 1st adult case with colon polyp and cancer who was diagnosed with PRIS. Her brain magnetic resonance imaging (MRI) and computed tomography (CT) scans reveal prominent bilateral brain lesions, matching with the proposed pathophysiologic mechanism of the syndrome. The patient received prompt acidosis correction and cardiorespiratory support. At last, she died from refractory circulatory failure.

CONCLUSION

It may be necessary to order a prompt neuroimaging examination in patients suspected with PRIS to judge whether brain lesions exist or not.

Propofol Is Mitochondrion-Toxic and May Unmask a Mitochondrial Disorder

There are indications that preexisting mitochondrial disorders or beta-oxidation defects predispose for propofol infusion syndrome. This review aimed at investigating if propofol infusion syndrome occurs exclusively in patients with mitochondrial disorder and if propofol can unmask a mitochondrial disorder. Propofol infusion syndrome has been reported in genetically confirmed mitochondrial disorder patients. In addition, muscle biopsy of patients with propofol infusion syndrome revealed complex IV or complex II deficiency. In animal studies propofol disrupted the electron flow along the respiratory chain and decreased complex I, complex II, and complex III of the respiratory chain. In addition, propofol disrupted the permeability transition pore and reduced the mitochondrial membrane potential. In conclusion, propofol is mitochondrion-toxic and mitochondrial disorder patients should not receive propofol in high dosages over a prolonged period of time. Short-term application of propofol should be safe even in mitochondrial disorder patients. Not only does propofol infusion syndrome occur in mitochondrial disorder patients, but mitochondrial disorder patients are likely at higher risk to develop propofol infusion syndrome. Patients who develop propofol infusion syndrome should be screened for mitochondrial disorder. Propofol infusion syndrome is preventable if risk factors are thoroughly assessed, and if long-term propofol is avoided in patients at risk for propofol infusion syndrome.

In vivo study of hepatic oxidative stress and mitochondrial function in rabbits with severe hypotension after propofol prolonged infusion

In humans, prolonged sedations with propofol or using high doses have been associated with propofol infusion syndrome. The main objective of this study was to evaluate the effects of prolonged high-dose administration of a specific propofol emulsion (Propofol Lipuro) and an improved lipid formulation (SMOFlipid) in liver mitochondrial bioenergetics and oxidative stress of rabbits, comparatively to a saline control. Twenty-one male New Zealand white rabbits were randomly allocated in three groups that were continuously treated for 20 h. Each group of seven animals received separately: NaCl 0.9 % (saline), SMOFlipid (lipid-based emulsion without propofol) and Lipuro 2 % (propofol lipid emulsion). An intravenous propofol bolus of 20 mg kg⁻¹ was given to the propofol Lipuro group to allow blind orotracheal intubation and mechanical ventilation. Anesthesia was maintained using infusion rates of: 20, 30, 40, 50 and 60 mg kg⁻¹ h⁻¹, according to the clinical scale of anesthetic depth and the index of consciousness values. The SMOFlipid and saline groups received the same infusion rate as the propofol Lipuro group, which were infused during 20 consecutive hours. At the end, the animals were euthanized, livers collected and mitochondria isolated by standard differential centrifugation. Mitochondrial respiration, membrane potential, swelling and oxidative stress were evaluated. Data were processed using one-way ANOVA (p < 0.05). The animals revealed a significant decrease in cardiovascular parameters showing bradycardia and severe hypotension. No statistical differences were observed when using pyruvate as substrate, however, when using succinate as respiratory substrate, significant decrease in ADP-stimulated respiration rate was observed for SMOFlipid group (p = 0.002). Lipid peroxides (p < 0.01) and protein carbonyls (p = 0.01) showed a statistically significant difference between propofol Lipuro and the SMOFlipid groups. These results suggest that lipid-based emulsions can be involved in the regulation of different pathways that ultimately lead to a decrease of state 3 mitochondrial respiration rate. The infusion of propofol Lipuro during prolonged periods, in addition to marked hypotension and hypoperfusion, also showed to have higher anti-oxidant activity and lower impairment of the mitochondrial function comparatively to the improved lipid formulation, SMOFlipid, using the rabbit as animal model.

Ischemia reperfusion injury as a modifiable therapeutic target for cardioprotection or neuroprotection in patients undergoing cardiopulmonary resuscitation

AIMS

We sought to review cellular changes that occur with reperfusion to try to understand whether ischemia-reperfusion injury (RI) is a potentially modifiable therapeutic target for cardioprotection or neuroprotection in patients undergoing cardiopulmonary resuscitation.

DATA SOURCES

Articles written in English and published in PubMed.

RESULTS

Remote ischemic conditioning (RIC) involves brief episodes of non-lethal ischemia and reperfusion applied to an organ or limb distal to the heart and brain. Induction of hypothermia involves cooling an ischemic organ or body. Both have pluripotent effects that reduce the potential harm associated with RI in the heart and brain by reduced opening of the mitochondrial permeability transition pore. Recent trials of RIC and induced hypothermia did not demonstrate these treatments to be effective. Assessment of the effect of these interventions in humans to date may have been modified by use of concurrent medications including propofol.

CONCLUSIONS

Ongoing research is necessary to assess whether reduction of RI improves patient outcomes.

Propofol infusion syndrome: a structured review of experimental studies and 153 published case reports

INTRODUCTION

Propofol infusion syndrome (PRIS) is a rare, but potentially lethal adverse effect of a commonly used drug. We aimed to review and correlate experimental and clinical data about this syndrome.

METHODS

We searched for all case reports published between 1990 and 2014 and for all experimental studies on PRIS pathophysiology. We analysed the relationship between signs of PRIS and the rate and duration of propofol infusion causing PRIS. By multivariate logistic regression we looked at the risk factors for mortality.

RESULTS

Knowledge about PRIS keeps evolving. Compared to earlier case reports in the literature, recently published cases describe older patients developing PRIS at lower doses of propofol, in whom arrhythmia, hypertriglyceridaemia and fever are less frequently seen, with survival more likely. We found that propofol infusion rate and duration, the presence of traumatic brain injury and fever are factors independently associated with mortality in reported cases of PRIS (area under receiver operator curve = 0.85). Similar patterns of exposure to propofol (in terms of time and concentration) are reported in clinical cases and experimental models of PRIS. Cardiac failure and metabolic acidosis occur early in a dose-dependent manner, while arrhythmia, other electrocardiographic changes and rhabdomyolysis appear more frequently after prolonged propofol infusions, irrespective of dose.

CONCLUSION

PRIS can develop with propofol infusion <4 mg/kg per hour and its diagnosis may be challenging as some of its typical features (hypertriglyceridaemia, fever, hepatomegaly, heart failure) are often (>95 %) missing and others (arrhythmia, electrocardiographic changes) occur late.

Anesthetic propofol overdose causes vascular hyperpermeability by reducing endothelial glycocalyx and ATP production

Prolonged treatment with a large dose of propofol may cause diffuse cellular cytotoxicity; however, the detailed underlying mechanism remains unclear, particularly in vascular endothelial cells. Previous studies showed that a propofol overdose induces endothelial injury and vascular barrier dysfunction. Regarding the important role of endothelial glycocalyx on the maintenance of vascular barrier integrity, we therefore hypothesized that a propofol overdose-induced endothelial barrier dysfunction is caused by impaired endothelial glycocalyx. In vivo, we intraperitoneally injected ICR mice with overdosed propofol, and the results showed that a propofol overdose significantly induced systemic vascular hyperpermeability and reduced the expression of endothelial glycocalyx, syndecan-1, syndecan-4, perlecan mRNA and heparan sulfate (HS) in the vessels of multiple organs. In vitro, a propofol overdose reduced the expression of syndecan-1, syndecan-4, perlecan, glypican-1 mRNA and HS and induced significant decreases in the nicotinamide adenine dinucleotide (NAD+)/NADH ratio and ATP concentrations in human microvascular endothelial cells (HMEC-1). Oligomycin treatment also induced significant decreases in the NAD+/NADH ratio, in ATP concentrations and in syndecan-4, perlecan and glypican-1 mRNA expression in HMEC-1 cells. These results demonstrate that a propofol overdose induces a partially ATP-dependent reduction of endothelial glycocalyx expression and consequently leads to vascular hyperpermeability due to the loss of endothelial barrier functions.

Propofol infusion syndrome in adults: a clinical update

Propofol infusion syndrome is a rare but extremely dangerous complication of propofol administration. Certain risk factors for the development of propofol infusion syndrome are described, such as appropriate propofol doses and durations of administration, carbohydrate depletion, severe illness, and concomitant administration of catecholamines and glucocorticosteroids. The pathophysiology of this condition includes impairment of mitochondrial beta-oxidation of fatty acids, disruption of the electron transport chain, and blockage of beta-adrenoreceptors and cardiac calcium channels. The disease commonly presents as an otherwise unexplained high anion gap metabolic acidosis, rhabdomyolysis, hyperkalemia, acute kidney injury, elevated liver enzymes, and cardiac dysfunction. Management of overt propofol infusion syndrome requires immediate discontinuation of propofol infusion and supportive management, including hemodialysis, hemodynamic support, and extracorporeal membrane oxygenation in refractory cases. However, we must emphasize that given the high mortality of propofol infusion syndrome, the best management is prevention. Clinicians should consider alternative sedative regimes to prolonged propofol infusions and remain within recommended maximal dose limits.

Protective Effects of Propofol Against Methamphetamine-induced Neurotoxicity

CONTEXT

Methamphetamine (METH) is widely abused in worldwide. METH use could damage the dopaminergic system and induce neurotoxicity via oxidative stress and mitochondrial dysfunction. Propofol, a sedative-hypnotic agent, is known for its antioxidant properties. In this study, we used propofol for attenuating of METH-induced neurotoxicity in rats.

SUBJECTS AND METHODS

We used Wistar rats that the groups (six rats each group) were as follows: Control, METH (5 mg/kg IP), and propofol (5, 10 and 20 mg/kg, IP) was administered 30 min before METH. After 24 h, animals were killed, brain tissue was separated and the mitochondrial fraction was isolated, and oxidative stress markers were measured.

RESULTS

Our results showed that METH significantly increased oxidative stress markers such as lipid peroxidation, reactive oxygen species formation and glutathione oxidation in the brain, and isolated mitochondria. Propofol significantly inhibited METH-induced oxidative stress in the brain and isolated mitochondria. Mitochondrial function decreased dramatically after METH administration that propofol pretreatment significantly improved mitochondrial function. Mitochondrial swelling and catalase activity also increased after METH exposure but was significantly decreased with propofol pretreatment.

CONCLUSIONS

These results suggest that propofol prevented METH-induced oxidative stress and mitochondrial dysfunction and subsequently METH-induced neurotoxicity. Therefore, the effectiveness of this antioxidant should be evaluated for the treatment of METH toxicity and neurodegenerative disease.

Attenuation of cisplathin-induced toxic oxidative stress by propofol

Background:

Antioxidant effects of propofol (2, 6-diisopropylphenol) were evaluated against cisplatin-i‎nduced oxidative stress in rat.

Objectives:

In this experimental study, 20 male rats were equally divided into 4 groups (5 rats each), and were treated by propofol (10 mg/kg/day, IP), or cisplatin (7 mg /kg/day, IP), or both.

Materials and Methods:

G‎roup one was control, while group 2 was given cisplatin (7 mg /kg/day, IP). Animals of the third group received only propofol (10 mg/kg/day, IP). Group 4 was given propofol with cisplatin once per day for 7 days. After treatment, blood urea nitrogen, creatinine levels, and oxidative stress m‎arkers such as total thiol groups (TTG), lipid peroxidation (LPO), and total antioxidant ‎capacity (TAC) were measured.

Results:

Oxidative stress induced by cisplatin, was evident by a significant increase in LPO and decrease in TTG and TAC. Propofol recovered ‎cisplatin -induced changes in TAC, TTG and LPO in blood.

Conclusions:

It is concluded that oxidative ‎damage is the mechanism of cisplatin toxicity, which can be recovered by propofol.‎

Potential non-hypoxic/ischemic causes of increased cerebral interstitial fluid lactate/pyruvate ratio: a review of available literature

Microdialysis, an in vivo technique that permits collection and analysis of small molecular weight substances from the interstitial space, was developed more than 30 years ago and introduced into the clinical neurosciences in the 1990s. Today cerebral microdialysis is an established, commercially available clinical tool that is focused primarily on markers of cerebral energy metabolism (glucose, lactate, and pyruvate) and cell damage (glycerol), and neurotransmitters (glutamate). Although the brain comprises only 2% of body weight, it consumes 20% of total body energy. Consequently, the ability to monitor cerebral metabolism can provide significant insights during clinical care. Measurements of lactate, pyruvate, and glucose give information about the comparative contributions of aerobic and anaerobic metabolisms to brain energy. The lactate/pyruvate ratio reflects cytoplasmic redox state and thus provides information about tissue oxygenation. An elevated lactate pyruvate ratio (>40) frequently is interpreted as a sign of cerebral hypoxia or ischemia. However, several other factors may contribute to an elevated LPR. This article reviews potential non-hypoxic/ischemic causes of an increased LPR.

Propofol ameliorates doxorubicin-induced oxidative stress and cellular apoptosis in rat cardiomyocytes

BACKGROUND

Propofol is an anesthetic with pluripotent cytoprotective properties against various extrinsic insults. This study was designed to examine whether this agent could also ameliorate the infamous toxicity of doxorubicin, a widely-used chemotherapeutic agent against a variety of cancer diseases, on myocardial cells.

METHODS

Cultured neonatal rat cardiomyocytes were administrated with vehicle, doxorubicin (1μM), propofol (1μM), or propofol plus doxorubicin (given 1h post propofol). After 24h, cells were harvested and specific analyses regarding oxidative/nitrative stress and cellular apoptosis were conducted.

RESULTS

Trypan blue exclusion and MTT assays disclosed that viability of cardiomyocytes was significantly reduced by doxorubicin. Contents of reactive oxygen and nitrogen species were increased and antioxidant enzymes SOD1, SOD2, and GPx were decreased in these doxorubicin-treated cells. Mitochondrial dehydrogenase activity and membrane potential were also depressed, along with activation of key effectors downstream of mitochondrion-dependent apoptotic signaling. Besides, abundance of p53 was elevated and cleavage of PKC-δ was induced in these myocardial cells. In contrast, all of the above oxidative, nitrative and pro-apoptotic events could be suppressed by propofol pretreatment.

CONCLUSIONS

Propofol could extensively counteract oxidative/nitrative and multiple apoptotic effects of doxorubicin in the heart; hence, this anesthetic may serve as an adjuvant agent to assuage the untoward cardiac effects of doxorubicin in clinical application.

Analytic Reviews: Propofol Infusion Syndrome in the ICU

Propofol is an alkylphenol derivative named 2, 6, diisopropylphenol and is a potent intravenous short-acting hypnotic agent. It is commonly used as sedation, as well as an anesthetic agent in both pediatric and adult patient populations. There have been numerous case reports describing a constellation of findings including metabolic derangements and organ system failures known collectively as propofol infusion syndrome (PRIS). Although there is a high mortality associated with PRIS, the precise mechanism of action has yet to be determined. The best preventive measure for this syndrome is awareness and avoidance of clinical scenarios associated with development of PRIS. There is no established treatment for PRIS; care is primarily supportive in nature and may include the full array of advanced cardiopulmonary support, including extracorporeal membrane oxygenation (ECMO). This article reviews the reported cases of PRIS and describes the current understanding of the underlying pathophysiology and treatment options.

A Rare Case of Propofol-Induced Acute Liver Failure and Literature Review

The incidence of drug-induced acute liver failure is increasing. A number of drugs can inhibit mitochondrial functions, alter β-oxidation and cause accumulation of free fatty acids within the hepatocytes. This may result in hepatic steatosis, cell death and liver injury. In our case, propofol, an anesthetic drug commonly used in adults and children, is suspected to have induced disturbance of the mitochondrial respiratory chain, which in consequence led to insufficient energy supply and finally liver failure. We report the case of a 35-year-old Caucasian woman with acute liver failure after anesthesia for stripping of varicose veins. Liver histology, imaging and laboratory data indicate drug-induced acute liver failure, presumably due to propofol. Hepatocyte death and microvesicular fatty degeneration of 90% of the liver parenchyma were observed before treatment with steroids. Six months later, a second biopsy was performed, which revealed only minimal steatosis and minimal periportal hepatitis. We suggest that propofol led to impaired fatty acid oxidation possibly due to a genetic susceptibility. This caused free fatty acid accumulation within hepatocytes, which presented as hepatocellular fatty degeneration and cell death. Large scale hepatocyte death was followed by impaired liver function and, consecutively, progressed to acute liver failure.

Brugada-like EKG pattern and myocardial effects in a chronic propofol abuser

INTRODUCTION

Cases of death are reported due to medical use of propofol, whereas deaths due to recreational purpose are unusual.

CASE REPORT

A 26-year-old Caucasian man, physician trainee in anesthesiology, was referred to an intensive care unit. The man was found unconscious in his bed with a butterfly-needle canalized into the vein of the left forearm and connected to an empty syringe. Transferred to the local hospital, the patient was monitored, and EKG showed typical Brugada features in V1-V3. Profound hypotension and metabolic acidosis were registered. Half an hour after admission, the patient developed prolonged QT interval, idioventricular rhythm, and ventricular fibrillation. Strong positive reaction for tumor necrosis factor alpha in cardiac myocytes and a diffuse apoptotic process in the heart specimens were observed. The multiple needle marks on the hands and forearms, and the propofol concentration in the hair examined (0.73 microg/g), led us to believe that the young man was a long-term propofol abuser.

DISCUSSION

Development of the EKG pattern of ST-segment elevation in leads V1-V3 may be the first indicator of electrical instability and high risk for imminent sudden death. Whether this finding applies to other patients poisoned with propofol is unclear, but the association of sudden death and the acquired EKG pattern has been observed in other disease states.

CONCLUSION

This article describes a fatal propofol-related death case because of recreational purpose; the EKG pattern, the cardiac morphology, and the expression of tumor necrosis factor alpha and apoptosis in cardiac tissue specimens are discussed to elucidate the mechanism of death.

GABAergic mechanism of propofol toxicity in immature neurons

Certain anesthetics exhibit neurotoxicity in the brains of immature but not mature animals. Gamma-aminobutyric acid (GABA), the primary inhibitory neurotransmitter in the adult brain, is excitatory on immature neurons via its action at the GABAA receptor, due to a reversed transmembrane chloride gradient. GABAA receptor activation in immature neurons is sufficient to open L-type voltage-gated calcium channels. As propofol is a GABAA agonist, we hypothesized that it and more specific GABAA modulators would increase intracellular free calcium ([Ca2+]i), resulting in the death of neonatal rat hippocampal neurons. Neuronal [Ca2+]i was monitored using Fura2-AM fluorescence imaging. Cell death was assessed by double staining with propidium iodide and Hoechst 33258 at 1 hour (acute) and 48 hours (delayed) after 5 hours exposure of neurons to propofol or the GABAA receptor agonist, muscimol, in the presence and absence of the GABA receptor antagonist, bicuculline, or the L-type Ca2+ channel blocker, nifedipine. Fluorescent measurements of caspase-3,-7 activities were performed at 1 hour after exposure. Both muscimol and propofol induced a rapid increase in [Ca2+]i in days in vitro (DIV) 4, but not in DIV 8 neurons, that was inhibited by nifedipine and bicuculline. Caspase-3,-7 activities and cell death increased significantly in DIV 4 but not DIV 8 hippocampal neuronal cultures 1 hour after 5 hours exposure to propofol, but not muscimol, and were inhibited by the presence of bicuculline or nifedipine. We conclude that an increase in [Ca2+]i, due to activation of GABAA receptors and opening of L-type calcium channels, is necessary for propofol-induced death of immature rat hippocampal neurons but that additional mechanisms not elicited by GABAA activation alone also contribute to cell death.

Propofol-related infusion syndrome in intensive care patients

The Institute of Medicine has identified adverse drug events as factors that significantly contribute to increased patient morbidity and mortality. As critically ill patients receive numerous drugs to treat a multitude of complicated health problems, they are at high risk for adverse drug events. Sedation is often a key requirement for the optimal management of critical illness, and propofol, a common sedative, has many desirable characteristics that make it the ideal agent in numerous circumstances. However, over the last decade, increasing numbers of reports have described a potentially fatal adverse effect called propofol-related infusion syndrome. Whether this adverse drug event is preventable is unclear, but recommendations have been proposed to minimize the potential for development of this syndrome. Research is under way to collect data on the use of propofol in intensive care units and on its prevalence.

Propofol and barbiturates for the anesthesia of refractory convulsive status epilepticus: pros and cons

OBJECTIVE

To discuss mainly the use of propofol and barbiturates in the anesthesia of refractory status epilepticus (RSE).

METHODS

Review of literature.

RESULTS

There are no prospective, randomized works comparing the effects of anesthetics in the treatment of RSE. Recently, the use of propofol has increased in the treatment of RSE. Propofol terminates both clinical and electric seizures quickly, but the maintenance of burst-suppression EEG pattern requires repetitive titration of doses. Relapses of seizures have occurred in 19-33% of patients, especially when tapering of dose. The advantages of barbiturates are lower frequency of short-term treatment failures, breakthrough seizures and changes to a different anesthetic agent. On the other hand, prolonged recovery leads to prolonged duration of mechanical ventilation, intensive care and hospital stay.

DISCUSSION

The use of propofol, barbiturates or midazolam in the anesthesia of RSE can be justified. When using propofol, the duration of high doses should be limited to 48 hours and the risk of propofol infusion syndrome should be kept in mind. High doses of barbiturates terminate effectively seizures but recovery from anesthesia prolongs ventilator treatment and intensive care.

[Mitochondria in anaesthesia and intensive care]

OBJECTIVE

Mitochondria play a key role in energy metabolism within the cell through the oxidative phosphorylation. They are also involved in many cellular processes like apoptosis, calcium signaling or reactive oxygen species production. The objectives of this review are to understand the interactions between mitochondrial metabolism and anaesthetics or different stress situations observed in ICU and to know the clinical implications.

DATA SOURCES

References were obtained from PubMed data bank (http://www.ncbi.nlm.nih.gov/entrez/query.fcgi) using the following keywords: mitochondria, anaesthesia, anaesthetics, sepsis, preconditioning, ischaemia, hypoxia.

DATA SYNTHESIS

Mitochondria act as a pharmacological target for the anaesthetic agents. The effects can be toxic like in the case of the local anaesthetics-induced myotoxicity. On the other hand, beneficial effects are observed in the anaesthetic-induced myocardial preconditioning. Mitochondrial metabolism could be disturbed in many critical situations (sepsis, chronic hypoxia, ischaemia-reperfusion injury). The study of the underlying mechanisms should allow to propose in the future new specific therapeutics.

Continuous renal replacement therapy in patients following traumatic injury

In critically injured patients, the incidence of acute renal failure has been reported to occur in as many as 31% of patients. The use of CRRT modalities for patients following traumatic injuries is becoming more common, albeit slowly, and this therapy may impact upon long-term recovery of renal function and mortality. Historical studies investigating the early use of intermittent dialysis reported significant improvement in survival in patients who were dialyzed earlier and more vigorously than in control subjects. Early trauma patients also showed improved survival following war injuries when dialyzed prophylactically. Although there is a growing acceptance in favor of earlier renal replacement therapy, the published consensus and the practice in many centers has been to dialyze/filter relatively ill rather than relatively healthy patients. The R Adams Cowley Shock Trauma Center (STC) in Baltimore, Maryland, USA, admits over 8,000 trauma patients each year. Within the STC, a program of continuous renal replacement therapy was established in the early 1980's. We review both historical and current literature on the use of renal replacement therapies after traumatic injury, and suggest some future areas of investigation and indications for these modalities.

Electrocardiographic changes predicting sudden death in propofol-related infusion syndrome

BACKGROUND

The occurrence of metabolic acidosis, rhabdomyolysis, hyperkalemia, and sudden cardiac death after long-term, high-dose propofol infusion has been referred to as propofol infusion syndrome (PRIS).

OBJECTIVES

The purpose of this study was to explore the ECG abnormalities observed in a patient with PRIS in order to identify possible pathophysiologic mechanisms of the syndrome.

METHODS

ECG changes in the index case were characterized by down-sloping ST-segment elevation in precordial leads V1 to V3 (Brugada-like ECG pattern). We subsequently assessed the relationship between this ECG pattern and the propofol infusion rate, the development of arrhythmias, and the occurrence of sudden death in a previously described cohort of 67 head-injured patients, seven of whom had been identified as having PRIS.

RESULTS

Six of the PRIS patients developed the ECG pattern of ST-segment elevation in leads V1 to V3 and died within hours of irrecoverable electrical storm. This ECG pattern was the first aberration recorded hours before the death of these patients. ECGs that were available for 30 of 60 unaffected patients exhibited a normal pattern. None of the 60 patients developed ventricular arrhythmias.

CONCLUSION

Our findings indicate that development of an acquired Brugada-like ECG pattern in severely head-injured patients is a sign of cardiac electrical instability that predicts imminent cardiac death. Future studies will determine whether such an ECG pattern also predicts imminent cardiac arrhythmia in other patient populations.

Propofol infusion syndrome: an unusual cause of renal failure

Propofol infusion syndrome has been increasingly recognized as a syndrome of unexplained myocardial failure, metabolic acidosis, and rhabdomyolysis with renal failure. It has been described only with acute neurologic injury or acute inflammatory diseases complicated by severe infections or sepsis. It appears to develop in the context of high-dose, prolonged propofol (100 microg/kg/min) treatment in combination with catecholamines and/or steroids. This was first noted in children but is increasingly recognized in adults. This is a case report of 2 patients (a 42-year-old man and a 17-year-old girl) who had acute renal failure associated with use of propofol in the appropriate clinical setting. It examines the pathophysiology and the possible mechanisms of this condition and illustrates the need to consider it as the cause of rhabdomyolysis and acute renal failure in critically ill patients.

Metabolic effects of propofol in the isolated perfused rat liver

Inhibitory effects of the intravenous anaesthetic propofol on mitochondrial energy metabolism have been reported by several authors. Impairment of energy metabolism is usually coupled to reduction in ATP production, which in turn is expected to lead to several alterations in cell metabolism such as stimulation of glycolysis and inhibition of gluconeogenesis. The present work aimed at finding an answer to the question of how propofol affects energy metabolism-linked parameters in the isolated perfused rat liver. In the fed state, propofol increased glycogenolysis (glucose release), glycolysis (lactate and pyruvate production) and oxygen uptake in the range between 10 and 500 microM. In the liver of fasted rats, propofol up to 100 microM increased oxygen uptake but decreased gluconeogenesis from three different substrates: lactate, alanine and glycerol. When lactate was the substrate 50% inhibition occurred at a propofol concentration of 50 microM. Propofol (100 microM) decreased the ATP content of the liver (-33.3%), increased the AMP content (+25%) and decreased the ATP/ADP and ATP/AMP ratios (49 and 45%, respectively). Most effects of propofol are probably due to impairment of oxidative phosphorylation. Particularly, the combined differential action on oxygen uptake (stimulation) and gluconeogenesis (inhibition) is strongly suggestive of an uncoupling action also under the conditions of the intact cell. This effect, in turn, is consistent with the reported high affinity of the cellular hepatic structure, especially membranes, for propofol.

Propofol-Infusionssyndrom

Propofol infusion syndrome has not only been observed in patients undergoing long-term sedation with propofol, but also during propofol anesthesia lasting 5 h. It has been assumed that the pathophysiologic cause is propofol's impairment of oxidation of fatty acid chains and inhibition of oxidative phosphorylation in the mitochondria, leading to lactate acidosis and muscular necrosis. It has been postulated that propofol might act as a trigger substrate in the presence of priming factors. Severe diseases in which the patient has been exposed to high catecholamine and cortisol levels have been identified as trigger substrates. Once the development of propofol infusion syndrome is suspected, propofol infusion has to be stopped immediately and specific therapeutic measures initiated, including cardiocirculatory stabilization and correction of metabolic acidosis. To increase elimination of propofol and its potential toxic metabolites, hemodialysis or hemofiltration are recommended. Due to its possible fatal side effects, the use of propofol for long-term sedation in critically ill patients should be reconsidered. In cases of unexplained lactate acidosis occurring during continuous propofol infusion, propofol infusion syndrome must be taken into consideration.

The Management of Status Epilepticus

Status epilepticus is a major medical emergency associated with significant morbidity and mortality. Status epilepticus is best defined as a continuous, generalized, convulsive seizure lasting > 5 min, or two or more seizures during which the patient does not return to baseline consciousness. Lorazepam in a dose of 0.1 mg/kg is the drug of first choice for terminating status epilepticus. Patients who continue to have clinical or EEG evidence of seizure activity after treatment with lorazepam should be considered to have refractory status epileptics and should be treated with a continuous infusion of propofol or midazolam. This article reviews current information regarding the management of status epilepticus in adults.

The pathophysiology of propofol infusion syndrome: a simple name for a complex syndrome

Propofol infusion syndrome (PRIS) is a rare and often fatal syndrome described in critically ill children undergoing long-term propofol infusion at high doses. Recently several cases have been reported in adults, too. The main features of the syndrome consist of cardiac failure, rhabdomyolysis, severe metabolic acidosis and renal failure. To date 21 paediatric cases and 14 adult cases have been described. These latter were mostly patients with acute neurological illnesses or acute inflammatory diseases complicated by severe infections or even sepsis, and receiving catecholamines and/or steroids in addition to propofol. Central nervous system activation with production of catecholamines and glucocorticoids, and systemic inflammation with cytokine production are priming factors for cardiac and peripheral muscle dysfunction. High-dose propofol, but also supportive treatments with catecholamines and corticosteroids, act as triggering factors. At the subcellular level, propofol impairs free fatty acid utilisation and mitochondrial activity. Imbalance between energy demand and utilisation is a key pathogenetic mechanism, which may lead to cardiac and peripheral muscle necrosis. Propofol infusion syndrome is multifactorial, and propofol, particularly when combined with catecholamines and/or steroids, acts as a triggering factor. The syndrome can be lethal and we suggest caution when using prolonged (>48 h) propofol sedation at doses higher than 5 mg/kg per h, particularly in patients with acute neurological or inflammatory illnesses. In these cases, alternative sedative agents should be considered. If unsuitable, strict monitoring of signs of myocytolysis is advisable.

Effects of nitrosopropofol on mitochondrial energy-converting system

Nitrosopropofol (NOPR) is a relatively stable compound obtained from the reaction between the general anesthetic 2,6 diisopropylphenol (propofol) and nitrosoglutathione (GSNO) and bearing a more acidic phenol group than propofol. It interfered with mitochondrial energetic metabolism in a concentration-dependent manner. Concentrations as high as 100 or 200 microM disrupted both oxidative phosphorylation and electron transport. Low concentrations of NOPR (50 microM) markedly slowed down the electron transport rate which was insensitive both to ADP and uncoupler stimulation and spontaneously gradually stopped. Consequently, both the transmembrane potential production and the ATP synthesis system were affected. In the presence of 10 or 20 microM NOPR, mitochondria respired but showed a worsening of the respiratory control and produced a transmembrane potential useful to respond to a phosphorylation pulse, but were not able to restore it. These results were consistent with ATP synthesis and swelling experiments. NOPR was effective at concentrations lower than those required by the combination of propofol and GSNO, suggesting that mitochondria might be able to catalyze the reaction between GSNO and propofol and that the resulting metabolite was more active on mitochondrial membrane structure than the parent compounds. Although the details of the process are yet unknown, the mechanism presented may be of potential relevance to rationalize the pathophysiological effects of propofol.

Different effects of propofol and nitrosopropofol on DMPC multilamellar liposomes

The mechanisms of reaction of propofol with nitrosoglutathione lead to the formation of an active species which was identified, and then synthesised, as 2,6-diisopropyl-4-nitrosophenol. In the present work, we demonstrate the in vitro formation of 2,6-diisopropyl-4-nitrosophenol, then we discuss the interaction of propofol and 2,6-diisopropyl-4-nitrosophenol with dimyristoylphosphatidylcholine and egg yolk phosphatidylcholine multilamellar liposomes using differential scanning calorimetry and spin labelling techniques. It was demonstrated that both molecules are highly lipophylic and absorb almost entirely in the lipid phase. The thermotropic profiles showed that these molecules affect the temperature and the co-operativity of the gel-to-fluid state transition of the liposomes differently: the effects of 2,6-diisopropylphenol on the lipid organisation are quite similar to phenol and coherently interpretable in terms of the disorder produced in the membrane by a bulky group; 2,6-diisopropyl-4-nitrosophenol is a stronger perturbing agent, and ESR spectra suggest that this is due to a relative accumulation of the molecule into the interfacial region of the bilayer.

Combined effect of propofol and GSNO on oxidative phosphorylation of isolated rat liver mitochondria

Isolated rat liver mitochondria have been treated with the general anaesthetic propofol (2,6-diisopropylphenol, 200 microM) and the physiological NO donor nitrosoglutathione (GSNO, 200 or 250 microM). The efficiency of the oxidative phosphorylation has been evaluated by measuring the respiration and ATP synthesis rates and the behavior of transmembrane electrical potential. In mitochondria energized by succinate, the simultaneous presence of both propofol and GSNO gives rise to a synergic action in affecting the resting and the ADP-stimulated respiration, the respiratory control ratio, the ATP synthesis, and the formation and utilization of the electrochemical transmembrane potential.

Propofol impairment of mitochondrial respiration in isolated perfused guinea pig hearts determined by reflectance spectroscopy

OBJECTIVE

To simultaneously determine the effect of propofol on myocardial oxygenation, mitochondrial function, and whole organ function in an isolated heart model, using optical reflectance spectroscopy.

DESIGN

Controlled laboratory investigation.

SETTING

Research laboratory.

SUBJECTS

Twenty adult guinea pigs.

INTERVENTIONS

Isolated hearts were perfused alternately with a modified oxygenated Krebs-Henseleit buffer and with buffer containing varied concentrations of propofol. Ninety seconds of ischemia were produced during perfusion with each solution studied.

MEASUREMENTS AND MAIN RESULTS

Myoglobin oxygen saturation, cytochrome c and cytochrome a/a3 redox state, and ventricular pressure were continuously measured from isolated guinea pig hearts during a 2-hr period. Myoglobin oxygen saturation increased and both cytochromes became more oxidized in the presence of propofol. During ischemia, myoglobin desaturation and cytochrome reduction were delayed and less complete in the presence of propofol. The mean ischemic time to 50% myoglobin desaturation was, on average, 14.3 secs with buffer perfusion, and increased to 24.5, 27.9, and 41.8 secs, with 50, 100, and 200 microM propofol perfusion, respectively. Ventricular function decreased linearly with increasing propofol concentration. From baseline buffer perfusion, maximal dP/dt per cardiac cycle decreased on average by 30.4%, 40.9%, and 69.4%, with 50, 100, and 200 microM propofol perfusion, respectively.

CONCLUSIONS

Propofol impairs either oxygen utilization or inhibits electron flow along the mitochondrial electron transport chain in the guinea pig cardiomyocyte. Propofol also significantly decreases ventricular performance in the isolated perfused heart. These effects are linearly correlated with propofol concentration in the range studied.