Comparative tolerability profiles of the inhaled anaesthetics

Volatile anesthetics maintain tidal volume and minute ventilation to a greater degree than propofol under spontaneous respiration

Background

Although general anesthetics depress spontaneous respiration, the comprehensive effect of general anesthetics on respiratory function remains unclear. We aimed to investigate the effects of general anesthetics on spontaneous respiration in non-intubated mice with different types and doses of general anesthetic.

Methods

Adult C57BL/6 J mice were administered intravenous anesthetics, including propofol and etomidate, and inhalational anesthetics, including sevoflurane and isoflurane in vivo at doses of 0.5-, 1.0-, and 2.0-times the minimum alveolar concentration (MAC)/median effective dose (ED₅₀) to induce loss of the righting reflex (LORR). Whole-body plethysmography (WBP) was applied to measure parameters of respiration under unrestricted conditions without endotracheal intubation. The alteration in respiratory sensitivity to carbon dioxide (CO₂) under general anesthesia was also determined. The following respiratory parameters were continuously recorded during anesthesia or CO₂ exposure: respiratory frequency (FR), tidal volume (TV), minute ventilation (MV), expiratory time (TE), inspiratory time (TI), and inspiratory–expiratory time ratio (I/E), and peak inspiratory flow.

Results

Sub-anesthetic concentrations (0.5 MAC) of sevoflurane or isoflurane increased FR, TV, and MV. With isoflurane and sevoflurane exposure, the CO₂-evoked increases in FR, TV, and MV were decreased. Compared with inhalational anesthetics, propofol and etomidate induced respiratory suppression, affecting FR, TV, and MV. In 100% oxygen (O₂), FR in the group that received propofol 1.0-times the ED₅₀ was 69.63 ± 33.44 breaths/min compared with 155.68 ± 64.42 breaths/min in the etomidate-treated group. In the same groups, FR was 88.72 ± 34.51 breaths/min and 225.10 ± 59.82 breaths/min, respectively, in 3% CO₂ and 144.17 ± 63.25 breaths/min and 197.70 ± 41.93 breaths/min, respectively, in 5% CO₂. A higher CO₂ sensitivity was found in etomidate-treated mice compared with propofol-treated mice. In addition, propofol induced a greater decrease in FR, MV, and I/E ratio compared with etomidate, sevoflurane, and isoflurane at equivalent doses (all P < 0.05).

Conclusions

General anesthetics differentially modulate spontaneous breathing in vivo. Volatile anesthetics increase FR, TV, and MV at sub-anesthetic concentrations, while they decrease FR at higher concentrations. Propofol consistently depressed respiratory parameters to a greater degree than etomidate.

Acute liver failure after sevoflurane anesthesia in a pediatric patient

Sevoflurane is a volatile anesthetic characterized by low toxicity and is the most used in pediatric age. Unlike other halogenated anesthetic, sevoflurane is not metabolized to reactive intermediates that lead to the formation of hepatotoxic proteins. However, a few cases of hepatotoxicity have been associated with its use. We report a case of an 11-year-old boy who developed acute liver failure after neurosurgical intervention, resection of a posterior fossa mass, under sevoflurane anesthesia and other drugs. Postoperatively, he presented abdominal pain and the laboratory tests showed markedly elevated aminotransferase levels, coagulopathy and thrombocytopenia. He had no fever, hypoglycemia or evidence of encephalopathy. The clinical evolution was favorable and after 7 days, laboratory values were completely normalized. All the possible causes of acute liver failure were evaluated and the differential diagnosis is exposed.

Neuroimaging of pain in animal models: a review of recent literature

Neuroimaging of pain in animals allows us to better understand mechanisms of pain processing and modulation. In this review, we discuss recently published brain imaging studies in rats, mice, and monkeys, including functional magnetic resonance imaging (MRI), manganese-enhanced MRI, positron emission tomography, and electroencephalography. We provide an overview of innovations and limitations in neuroimaging techniques, as well as results of functional brain imaging studies of pain from January 1, 2016, to October 10, 2018. We then discuss how future investigations can address some bias and gaps in the field. Despite the limitations of neuroimaging techniques, the 28 studies reinforced that transition from acute to chronic pain entails considerable changes in brain function. Brain activations in acute pain were in areas more related to the sensory aspect of noxious stimulation, including primary somatosensory cortex, insula, cingulate cortex, thalamus, retrosplenial cortex, and periaqueductal gray. Pharmacological and nonpharmacological treatments modulated these brain regions in several pain models. On the other hand, in chronic pain models, brain activity was observed in regions commonly associated with emotion and motivation, including prefrontal cortex, anterior cingulate cortex, hippocampus, amygdala, basal ganglia, and nucleus accumbens. Neuroimaging of pain in animals holds great promise for advancing our knowledge of brain function and allowing us to expand human subject research. Additional research is needed to address effects of anesthesia, analysis approaches, sex bias and omission, and potential effects of development and aging.

Sevoflurane Impairs Insulin Secretion and Tissue-Specific Glucose Uptake In Vivo

The use of anaesthetics severely influences substrate metabolism. This poses challenges for patients in clinical settings and for the use of animals in diabetes research. Sevoflurane can affect regulation of glucose homoeostasis at several steps, but the tissue-specific response remains to be determined. The aim of the study was to investigate the pharmacological effect of sevoflurane anaesthesia on glucose homoeostasis during hyperinsulinaemic clamp conditions, the gold standard method for assessment of whole-body insulin sensitivity. Conscious mice (n = 6) and mice under sevoflurane anaesthesia (n = 8) underwent a hyperinsulinaemic clamp where constant infusion of insulin and donor blood was administered during variable glucose infusion to maintain isoglycaemia. 2-[1-¹⁴ C]-deoxy-D-glucose was infused to determine tissue-specific uptake of glucose in adipose tissue, heart, brain and skeletal muscle. Sevoflurane anaesthesia severely impaired insulin-stimulated whole-body glucose uptake demonstrated by a 50% lower glucose infusion rate (GIR). This was associated with decreased glucose uptake in brain, soleus, triceps and gastrocnemius muscles in sevoflurane-anaesthetized mice compared to conscious mice. Plasma-free fatty acids (FFA), a potent inducer of insulin resistance, increased by 42% in mice during sevoflurane anaesthesia. In addition, insulin secretion from pancreatic β-cell was lower in fasted, anaesthetized mice. Sevoflurane anaesthesia impairs insulin secretion, induces insulin resistance in mice and reduces glucose uptake in non-insulin-sensitive tissue like the brain. The underlying mechanisms may involve sevoflurane-induced mobilization of FFA.

Hepatotoxicity of halogenated inhalational anesthetics

Context:

Halogenated inhalational anesthetics are currently the most common drugs used for the induction and maintenance of general anesthesia. Postoperative hepatic injury has been reported after exposure to these agents. Based on much evidence, mechanism of liver toxicity is more likely to be immunoallergic. The objective of this review study was to assess available studies on hepatotoxicity of these anesthetics.

Evidence Acquisition:

We searched PubMed, Google Scholar, Scopus, Index Copernicus, EBSCO and the Cochrane Database using the following keywords: “inhalational Anesthetics” and “liver injury”; “inhalational anesthetics” and “hepatotoxicity”; “volatile anesthetics” and “liver injury”; “volatile anesthetics” and hepatotoxicity for the period of 1966 to 2013. Fifty two studies were included in this work.

Results:

All halogenated inhalational anesthetics are associated with liver injury. Halothane, enflurane, isoflurane and desflurane are metabolized through the metabolic pathway involving cytochrome P-450 2E1 (CYP2E1) and produce trifluoroacetylated components; some of which may be immunogenic. The severity of hepatotoxicity is associated with the degree by which they undergo hepatic metabolism by this cytochrome. However, liver toxicity is highly unlikely from sevoflurane as is not metabolized to trifluoroacetyl compounds.

Conclusions:

Hepatotoxicity of halogenated inhalational anesthetics has been well documented in available literature. Halothane-induced liver injury was extensively acknowledged; however, the next generation halogenated anesthetics have different molecular structures and associated with less hepatotoxicity. Although anesthesia-induced hepatitis is not a common occurrence, we must consider the association between this disorder and the use of halogenated anesthetics.

Prolonged therapeutic hypothermia is more effective in attenuating brain apoptosis in a Swine cardiac arrest model

OBJECTIVES

To investigate whether 48 hours of therapeutic hypothermia is more effective to attenuate brain apoptosis than 24 hours and to determine whether the antiapoptotic effects of therapeutic hypothermia are associated with the suppressions of the cleavage of protein kinase C-δ, the cytosolic release of cytochrome c, and the cleavage of caspase 3 in a swine cardiac arrest model.

DESIGN

Prospective laboratory study.

SETTING

University laboratory.

SUBJECTS

Male domestic pigs (n = 24).

INTERVENTIONS

After 6 minutes of no-flow time that was induced by ventricular fibrillation, cardiopulmonary resuscitation was provided, and the return of spontaneous circulation was achieved. The animals were randomly assigned to the following groups: sham, normothermia, 24 hours of therapeutic hypothermia, or 48 hours of therapeutic hypothermia. Therapeutic hypothermia (core temperature, 32-34°C) was maintained for 24 or 48 hours post return of spontaneous circulation, and the animals were rewarmed for 8 hours. At 60 hours post return of spontaneous circulation, the animals were killed, and brain tissues were harvested.

MEASUREMENTS AND MAIN RESULTS

We examined cellular apoptosis and neuronal damage in the brain hippocampal cornu ammonis 1 region. We also measured the cleavage of protein kinase C-δ, the cytosolic release of cytochrome c, and the cleavage of caspase 3 in the hippocampus. The 48 hours of therapeutic hypothermia attenuated cellular apoptosis and neuronal damage when compared with normothermia. There was also a decrease in the cleavage of protein kinase C-δ, the cytosolic release of cytochrome c, and the cleavage of caspase 3. However, 24 hours of therapeutic hypothermia did not significantly attenuate cellular apoptosis or neuronal damage.

CONCLUSIONS

We found that 48 hours of therapeutic hypothermia was more effective in attenuating brain apoptosis than 24 hours of therapeutic hypothermia. We also found that the antiapoptotic effects of therapeutic hypothermia were associated with the suppressions of the cleavage of protein kinase C-δ, the cytosolic release of cytochrome c, and the cleavage of caspase 3.

Role of immune reactions in drug-induced liver injury (DILI)

Although some drugs cause drug-induced liver injury (DILI) through direct damage to hepatocytes or intereference with bile secretion, others cause delayed, often idiosyncratic, DILI with clinical features, such as mild lymphocytic infiltrate, that are reminiscent of allergic reactions involving activation of the adaptive immune system. Even in cases of direct drug-induced hepatotoxicity, infiltration of inflammatory cells into the liver is often observed, suggesting a role for the innate immune system (e.g., neutrophils, macrophages, and so on). Therefore, a variety of hypotheses for the pathogenesis of DILI center around a pathogenic role of drug- (or drug-metabolite-) specific adaptive immune cells, as well as hepatic-injury-induced innate immune responses in the development, progression, and/or resolution of DILI.

Severity of locomotor and cardiovascular derangements after experimental high-thoracic spinal cord injury is anesthesia dependent in rats

Anesthetics affect outcomes from central nervous system (CNS) injuries differently. This is the first study to show how two commonly used anesthetics affect continuously recorded hemodynamic parameters and locomotor recovery during a 2-week period after two levels of contusion spinal cord injury (SCI) in rats. We hypothesized that the level of cardiovascular depression and recovery of locomotor function would be dependent upon the anesthetic used during SCI. Thirty-two adult female rats were subjected to a sham, 25-mm or 50-mm SCI at T3-4 under pentobarbital or isoflurane anesthesia. Mean arterial pressure (MAP) and heart rate (HR) were telemetrically recorded before, during, and after SCI. Locomotor function recovered best in the 25-mm-injured isoflurane-anesthetized animals. There was no significant difference in locomotor recovery between the 25-mm-injured pentobarbital-anesthetized animals and the 50-mm-injured isoflurane-anesthetized animals. White matter sparing and extent of intermediolateral cell column loss appeared larger in animals anesthetized with pentobarbital, but this was not significant. There were no differential effects of anesthetics on HR and MAP before SCI, but recovery from anesthesia was significantly slower in pentobarbital-anesthetized animals. At the time of SCI, MAP was acutely elevated in the pentobarbital-anesthetized animals, whereas MAP decreased in the isoflurane-anesthetized animals. Hypotension occurred in the pentobarbital-anesthetized groups and in the 50-mm-injured isoflurane-anesthetized group. In pentobarbital-anesthetized animals, SCI resulted in acute elevation of HR, although HR remained low. Return of HR to baseline was much slower in the pentobarbital-anesthetized animals. Severe SCI at T3 produced significant chronic tachycardia that was injury severity dependent. Although some laboratories monitor blood pressure, HR, and other physiological variables during surgery for SCI, inherently few have monitored cardiovascular function during recovery. This study shows that anesthetics affect hemodynamic parameters differently, which in turn can affect functional outcome measures. This supports the need for a careful evaluation of cardiovascular and other physiological measures in experimental models of SCI. Choice of anesthetic should be an important consideration in experimental designs and data analyses.

The effects of volatile induction and maintenance of anesthesia and selective spinal anesthesia on QT interval, QT dispersion, and arrhythmia incidence

OBJECTIVE

The effects of sevoflurane general anesthesia and bupivacaine selective spinal anesthesia on QT dispersion (QTd) and corrected QT (QTc) interval were investigated.

METHODS AND MATERIALS

This prospective, randomized, double-blind study was conducted between July and September 2009 in the Urology and General Surgery operating rooms. Forty ASA I-II patients undergoing noncardiac surgery were randomized into two groups: Group R (n=20) and Group V (n=20). In Group R, 5 mg bupivacaine was administered into the spinal space. Anesthesia induction in Group V was established with sevoflurane + 0.1 mg/kg vecuronium using the maximum vital capacity technique. Anesthesia was maintained with 2-3% sevoflurane + 50% N2O/O2 inhalation. All patients were tested with a 24-hour Holter ECG device. QT, QTc, and QTd intervals were measured using 12-lead ECG records at 1 and 3 minutes during preinduction, postinduction, postincision and postextubation periods. Mean arterial pressure (MAP), heart rate and ECG records were measured simultaneously.

RESULTS

None of the patients displayed arrhythmia. There was no significant difference between the groups with regard to QTd values (p>0.05). However, QTc was longer in Group V than in Group R after the induction of anesthesia at 3 minutes, after the intubation at 1 and 3 minutes, and after the incision at 1 and 3 minutes. MAP and heart rate were generally higher in Group V (p<0.05).

CONCLUSION

Although Volatile Induction and Maintenance of Anesthesia (VIMA) with sevoflurane might prolong the QTc interval and did not result in arrhythmia, selective spinal anesthesia with bupivacaine was not associated with alterations in the QT interval or arrhythmia.

Drug-induced liver injury

Many drugs and environmental chemicals are capable of evoking some degree of liver injury. The liver represents a primary target for adverse drug reactions due to its central role in biotransformation and excretion of foreign compounds, its portal location within the circulation exposing it to a wide variety of substances, and its anatomic and physiologic structure. Drug-induced liver injury (DILI) remains the single most common adverse indication leading to drug candidate failure or withdrawal from the market. However, the absolute incidence of DILI is low, and this presents a challenge to mechanistic studies. DILI remains unpredictable making prevention very difficult. In this chapter, we focus on the current understanding of DILI. We begin with an overview regarding the significance and epidemiology of DILI and then examine the clinical presentation and susceptibility factors related to DILI. This is followed by a review of the current literature regarding the proposed pathogenesis of DILI, which involves the participation of a drug, or most often a reactive metabolite of the drug, that either directly affects cellular function or elicits an immune response. It is our hope that this chapter will shed light on the major problems associated with DILI in regards to the pharmaceutical industry, drug regulatory agencies, physicians and pharmacists, and patients.

Fatal subacute liver failure after repeated administration of sevoflurane anaesthesia

Sevoflurane is a widely used halogenated inhalation anaesthetic. In comparison with other similar anaesthetics, it is not metabolized to potentially hepatotoxic trifluoroacetylated proteins. In this case report, we present a 66-year-old woman with breast carcinoma, who underwent sevoflurane general anaesthesia twice in 25 days. Soon after the second elective surgical procedure, jaundice and marked elevations in serum transaminases developed. The patient died 66 days thereafter. Autopsy results denied evidence of major cardiovascular abnormality, and histological examination confirmed massive liver cell necrosis with no feature of chronic liver injury. Sevoflurane anaesthesia was imputed as the cause after exclusion of other possible aetiological agents. Besides, coexistent malignant tumours found in the patient could have modulated the immunological response to the applied anaesthetic followed by fatal consequences.

Inhaled anesthetic agents

PURPOSE

The pharmacology, bioavailability and pharmacokinetics, indications, clinical efficacy, adverse effects and toxicities, and dosage and administration of the inhaled anesthetics are reviewed.

SUMMARY

The inhaled anesthetics include desflurane, enflurane, halothane, isoflurane, and sevoflurane and are thought to enhance inhibitory postsynaptic channel activity and inhibit excitatory synaptic activity. The mechanism of action of inhaled anesthetics has not been completely defined. A number of factors can influence the pharmacokinetics of inhaled anesthetics, including solubility in blood, cardiac output, tissue equilibration, extent of tissue perfusion, metabolism, and age. All of the available inhaled anesthetics are effective for inducing or maintaining anesthesia or both. Most clinical trials of inhaled anesthetics have evaluated differences in induction and emergence from anesthesia by comparing (1) times to loss of reflex, extubation, and response to verbal commands; orientation to time and place; and ability to sit up without assistance, (2) need for post-surgical analgesia, and (3) time to discharge as measures of efficacy. Adverse effects and toxicities of the inhaled anesthetics include nephrotoxicity, hepatotoxicity, cardiac arrhythmias, neurotoxicity, postoperative nausea and vomiting, respiratory depression and irritation, malignant hyperthermia, and postanesthesia agitation. Safety issues surrounding these gases include occupational exposure and intraoperative fires within the delivery systems used with inhaled anesthetics. Drugs used for anesthesia during surgery can account for 5-13% of a hospital's drug budget.

CONCLUSION

The inhaled anesthetics have been shown to be both safe and effective in inducing and maintaining anesthesia. These agents differ in potency, adverse-effect profile, and cost. Newer anesthetic gases, such as sevoflurane and desflurane, appear to have more favorable physico-chemical properties. These factors, as well as patient characteristics and duration and type of procedure, must be considered when selecting an inhaled anesthetic.

Stability and compatibility assessment techniques for total parenteral nutrition admixtures: setting the bar according to pharmacopeial standards

PURPOSE OF REVIEW

The stability and compatibility of total parenteral nutrition mixtures compounded for patients requiring nutritional support is paramount to their safety on intravenous infusion. The most significant pharmaceutical issues associated with mixing total parenteral nutrition formulations affecting their safety involve the stability of lipid-injectable emulsions and the compatibility of calcium and phosphate salts. Methods of analysis for stability and compatibility have varied, and the assessments have mostly been largely qualitative.

RECENT FINDINGS

Although pharmacopeial standards have been primarily applicable to pharmaceutical manufacturers, recent efforts by the United States Pharmacopeia have been directed at standardizing pharmacy practices involved in the safe mixing of compounded sterile preparations. The adoption of chapter 797 entitled 'Pharmaceutical compounding - sterile preparations' on 1 January 2004 has had a dramatic impact on pharmacy practice in the United States. More recently, the United States Pharmacopeia has also proposed a new chapter 729 entitled 'Globule size distribution in lipid-injectable emulsions', setting specific limits on the sizes and concentrations of lipid droplets in the formulation, which may have implications for all-in-one mixtures. Finally, new efforts are under way to establish limits on the level of acceptable amounts of particulates intrinsically introduced by the manufacturer, and thus may have ramifications for particulates extrinsically introduced or initiated during compounding by the pharmacist.

SUMMARY

With careful monitoring and the development of appropriate pharmacopeial-based specifications that limit the size and concentration of large-diameter fat globules and eliminate the possibility of dibasic calcium phosphate precipitates, improved patient outcomes may be achieved.

Paracetamol-induced hepatotoxicity at recommended dosage

In patients who develop liver damage following moderate paracetamol overdose in the order of 5-10 g daily, recent fasting and nutritional impairment have been identified as key precipitants. Hepatotoxicity caused by paracetamol at recommended dosage, in the absence of exposure to enzyme-inducing drugs, has recently been described as an idiosyncratic phenomenon. The possible importance of fasting and malnutrition in this setting is uncertain. We report a severely malnourished 53-year-old woman who developed severe hepatotoxicity whilst receiving paracetamol at recommended dosage (4 g daily) following a period of fasting, in the absence of enzyme-inducing agents. Subsequent paracetamol exposure up to 2.6 g daily thrice weekly, in the setting of ongoing malnutrition and fasting as before, did not lead to recurrent liver damage. These findings indicate that paracetamol-related liver damage occurring within recommended dosage guidelines can be a dose-dependent rather than necessarily idiosyncratic phenomenon, at least in the setting of recent fasting and severe malnutrition.

Effects of Propofol-Sevoflurane Anesthesia on the Maternal and Fetal Hemodynamics Blood Gases, and Uterine Activity in Pregnant Goats

To determine the effects of propofol and sevoflurane on hemodynamics, acid-base balance and uterine activity in pregnant animals, a prospective experimental study was designed by use of ten pregnant goats. Propofol was intravenously administered at a bolus dose of 5 mg/kg and then infused a rate of 0.3 mg/kg/min for 5 min. Following the induction, the animals were incrementally inhaled 2.7 and 4.1% of end-tidal concentration of sevoflurane each for 30 min, and then recovered. The maternal and fetal heart rate (HR), arterial blood pressure (BP) and acid-base balance, the intrauterine pressure (IUP), and the uterine blood flow (UBF) were measured. Following the pre-anesthetic data, the parameters were measured 7 times throughout the anesthetic and recovering periods. The propofol infusion induced 1.37 times of HR increase and produced decrease in PO(2) and a relevant metabolic acidemia in the mother, with no effect in the fetus. Sevoflurane reduced BP in the fetus from 30 (2.7%) to 60 (4.1%) min of inhalation. The uterine contractions disappeared throughout sevoflurane inhalation, and then recurred within 15 min after the cessation of sevoflurane. Propofol injection increases HR, and induces a moderate hypoxemia and metabolic acidemia associated with the suppressed ventilation for pregnant goats, with less effect on the fetal hemodinamics. Sevoflurane causes minimal change in maternal hemodynamics, but induces significant hypotension in the fetus and reduction of uterine activity. These data may be useful in making anesthetic choices combined with analgesia for Caesarian section in goats.

Remifentanil in emergency caesarean section in pre-eclampsia complicated by thrombocytopenia and abnormal liver function

We describe the use of remifentanil in a woman with severe pre-eclampsia who presented for emergency caesarean section. Remifentanil was effective in obtunding the hypertensive response to laryngoscopy and intubation. Previous studies have found no significant adverse effects of remifentanil on the neonate. With its short duration of action, the use of this new opioid has several potential advantages in the above setting. Further studies are required to explore the use of remifentanil as an adjunct to obstetric general anaesthesia.