Inhalational Anesthetic Agents Research Articles

Pharmacoeconomics of Volatile Inhalational Anaesthetic Agents: An 11-Year Retrospective Analysis

With continuously increasing expenditure on health care resources, various cost containment strategies have been suggested in regard to controlling the cost of inhalational anaesthetic agents. We performed a cost identification analysis assessing inhalational anaesthetic agent expenditure at a tertiary level hospital, along with an evaluation of strategies to contain the cost of these agents. The number of bottles of isoflurane, sevoflurane and desflurane used during the financial years 1997 to 2007 was retrospectively determined and the acquisition costs and cumulative drug expenditure calculated. Pharmacoeconomic modelling using low fresh gas flow anaesthesia was performed to evaluate practical methods of cost reduction. The use of isoflurane decreased from 384 bottles during 1997 to 204 in 2007. In contrast, use of sevoflurane increased from 226 bottles during 1998 to 875 during 2007. Desflurane use increased from 34 bottles per year during 2002 (its year of introduction) to 163 bottles per year in 2007. While the inflation-adjusted cumulative expenditure for these inhalational agents (Australian dollars) increased from $132,000 in 1997 to over $326,000 in 2007, an increase of 168%, patient workload over the same period increased by only 11%. Pharmacoeconomic modelling demonstrated that sevoflurane at 2 l/minute costs 19 times more than isoflurane at 0.5 l/minute. For the financial years 1997 to 2007, we found a progressive shift from the cheaper isoflurane to the more expensive agents, sevoflurane and desflurane, a shift associated with marked increases in costs. Low flow anaesthesia with isoflurane is one strategy to reduce costs.

Effects of Anesthetic Regimens and Other Confounding Factors Affecting the Interpretation of Motor Evoked Potentials During Pediatric Spine Surgery

ABSTRACT.Children undergoing corrective spine surgery are at risk of serious neurologic injury. Monitoring transcranial electric motor evoked potentials (TCeMEPs) during these procedures may identify and help prevent injury to motor pathways. The difficulty in obtaining consistent motor evoked potential (MEP) responses during pediatric spine surgery can result in part to the suppression of evoked responses caused by volatile inhalational anesthetics, elevated levels of propofol, and/or physiologic variables. Data obtained from 140 pediatric patients who underwent spine surgery with MEP monitoring were retrospectively analyzed and evaluated for age and anesthetic effects on stimulation variables. MEPs acquired under inhalational anesthetic agents required greater stimulation compared to intravenous propofol anesthesia. Additionally, the responses were more variable when inhalational agents were used. These effects were more prominent in younger age patients. The number of alerts of MEP loss or reduction related to anesthetic levels or blood pressure changes was higher under inhalational agents.

Regulation of sevoflurane on immune factors

Sevoflurane is a potent non-explosive inhalational anesthetic agent which provides rapid anesthetic induction and recovery consistent with its low distribution coefficient and high efficacy. Recently, the immune responses to sevoflurane and immune regulation have attracted sufficient attention, mainly focusing on its anti-inflammatory effects, attenuation of the stress response and relief of the ischemia-reperfusion injury. This review briefly demonstrates the immune responses and the immuno-mechanism of red blood cell, lymphocyte and cytokines when exposed to sevoflurane. Since the regulation of sevoflurane is precise and complex, the diversification deserves further experimental and clinical evidences. Key words: Sevoflurane; Regulation; Immune factors

Inhalational Anesthesia: Basic Pharmacology, End Organ Effects, and Applications in the Treatment of Status Asthmaticus

The potent inhalational anesthetic agents are used on a daily basis to provide intraoperative anesthesia. Given their beneficial effects on airway tone and reactivity, they also have a role in the treatment of status asthmaticus that is refractory to standard therapy. Although generally not of clinical significance, these agents can affect various physiological functions. The potent inhalational anesthetic agents decrease mean arterial pressure and myocardial contractility. The decrease in mean arterial pressure reduces renal and hepatic blood flow. Secondary effects on end-organ function may result from the metabolism of these agents and the release of inorganic fluoride. The following article reviews the history of inhalational anesthesia, the physical structure of the inhalational anesthetic agents, their end-organ effects, reports of their use for the treatment of refractory status asthmaticus in the intensive care unit (ICU) patient, and special considerations for their administration in this setting including equipment for their delivery, scavenging, and monitoring.

Daycase laparoscopic gynaecological procedures--current trends in anaesthetic management.

Laparoscopy for gynaecological procedures is minimally invasive and is mostly performed as a daycase. The advancement of laparoscopy and minimal access surgery has greatly influenced the evolution of anaesthetic techniques. Preoperative assessment can be simplified by the use of questionnaires in pre-assessment clinics. Intraoperative intravenous fluid administration improves patient well being while airway management can be by the age-old, tried and trusted orotracheal tube or by the newer laryngeal mask airways. The use of propofol as an induction agent, a short acting non-depolarizing muscle relaxant e.g. mivacurium, an inhalational anaesthetic agent with a fast wake up time e.g. sevoflurane or desflurane, and short acting opioids e.g. fentanyl guarantees quick recovery of patients. The trend towards a multimodal approach to postoperative pain and prevention of postoperative nausea and vomiting (PONV) improves postoperative profile of day case gynaecological patients. Expertise in providing a pneumoperitoneum with carbon dioxide is desirable even as other options for lifting the abdominal wall are being investigated.

Inhalational Anesthetics in Acute Severe Asthma

Acute severe asthma is characterized by a state of airway inflammation and increased bronchiolar smooth-muscle tone that leads to increased resistance to expiration and lung hyperinflation. Despite the better knowledge of its pathophysiology, the incidence and severity of asthma in the last twenty years is increased worldwide, although with significant age and geographic variation. As a result, the number of patients requiring more intensive medical therapy has also increased. In the most severe cases, often referred to as near-fatal asthma, the institution of mechanical ventilation may be required. Volatile anesthetics have bronchodilator effects on the bronchial smooth muscle. The use of inhalational anesthetic agents for treatment of severe status asthmaticus has been documented in case reports, case series and small uncontrolled studies. Their use may be considered in any mechanically ventilated patients whose severe bronchospasm failed to respond to maximal medical treatment. In the present review article, we aim to provide a brief description of the physio-pathological and clinical features of acute severe asthma, and of the principles of treatment, focusing our attention on the use of the inhalational anesthetics in severe patients requiring mechanical ventilation and not responding to conventional therapy.

Update on inhalational anaesthetics

Inhalational anaesthetic agents are a cornerstone in modern anaesthetic practice. The currently used compounds are very effective and have a good safety profile. In addition, it has been demonstrated that they possess organ-protective properties that might provide an additional tool in the treatment or prevention of the consequences of organ ischaemia-reperfusion injury or both. The present review summarizes some of the most recent findings on this subject. The mechanisms underlying the organ-protective effects of inhalational anaesthetics continue to be further unravelled. The main challenge, however, is to determine the clinical importance of these protective effects and their potential benefits for patients. Initial observations in cardiac surgery are encouraging, and the first clinical studies on other organ systems are being published. Noble gases share these organ-protective properties and may provide an additional tool for this purpose both in situations in which anaesthesia is needed (xenon) or in cases in which anaesthesia is not necessary (helium). In the experimental setting, inhalational anaesthetics have protective effects against ischaemia-reperfusion injury. Initial perioperative data suggest that these effects may also result into clinically relevant improved organ function. However, further research will be needed to reveal whether these organ-protective properties will ultimately translate into an improved short-term and long-term postoperative outcome.

Cardiovascular responses to transvenous electrical cardioversion of atrial fibrillation in anaesthetized horses

ObjectiveTo examine the influence of direct current shock application in anaesthetized horses with atrial fibrillation (AF) and to study the effects of cardioversion to sinus rhythm (SR). Study designProspective clinical study. AnimalsEight horses successfully treated for AF (transvenous electrical cardioversion after amiodarone pre-treatment). MethodsCardioversion catheters and a pacing catheter were placed under sedation [detomidine 10 μg kg−1 intravenously (IV)]. After additional sedation (5–10 μg kg−1 detomidine, 0.1 mg kg−1 methadone IV), anaesthesia was induced with ketamine, 2.2 mg kg−1 and midazolam, 0.06 mg kg−1 (IV) in a sling and maintained with isoflurane in oxygen. Flunixin meglumine, 1.1 mg kg−1, was administered IV. Shocks were delivered as biphasic truncated exponential waves, synchronized with the R-wave of the electrocardiogram. Monitoring included pulse oximetry, electrocardiography, capnography, inhalational anaesthetic agent concentration, arterial blood pressure, LiDCO and PulseCO cardiac index (CI) and arterial blood gases. Values before and after the first unsuccessful shock and before and after cardioversion to SR were compared. ResultsValues before the first shock were comparable to reported values in healthy, isoflurane anaesthetized horses. Reliable CI measurements could not be obtained using the PulseCO technique. Intermittent positive pressure ventilation was required in most horses (bradypnea and/or PaCO2 >8 kPa, 60 mmHg), while dobutamine was administered in two horses (0.3–0.5 μg kg−1 minute−1). After the 1st unsuccessful shock application, systolic arterial pressure (SAP) was decreased (p = 0.025), other recorded values were not influenced (CI measurements not available for this analysis). SR was associated with increases in CI (p = 0.039) and stroke index (p = 0.002) and a decrease in SAP (p = 0.030). Conclusions and clinical relevanceDespite the presence of AF, cardiovascular function was well maintained during anaesthesia and was not affected by shock application. Cardiac index and stroke index increased and SAP decreased after cardioversion.

Duchenne muscular dystrophy: how I do it? Regional or general anesthesia?

Sir—We have read with interest the correspondence sent by Driessen and Snoeck (1), titled the ‘Duchenne muscular dystrophy: which is the best anesthetic agent’. Sensitivity of patients with Duchenne muscular dystrophy (DMD) to sedative, anesthetic and neuromuscular blocking agents may result in life-threatening perioperative complications such as progressive respiratory failure, acute rhabdomyolisis, cardiac arrest, and malign hypertermia-like syndrome (2). The authors emphasize that in children with DMD are predispose to develop serious problems during surgery and anesthesia irrespective of the type of anesthetic agents used too. Anesthetic management of these patients is challenging and may cause serious problems to the anesthesiologist. Is regional anesthesia a safe and reliable alternative to general anesthesia in patients with DMD? Some cases have been reported in which regional anesthesia has been used in literature (3,4). Hereby, we report a pediatric case with DMD, who underwent successful orchidopexy operation under spinal anesthesia. A 3-year-old boy (weight 15 kg, height 95 cm) diagnosed with DMD underwent an orchidopexy operation. There is a muscle biopsy at 1 year in previous anesthetic history. He was medicated with dexametazone, and it was discontinued a week before the operation. Physical examination on cardiovascular and respiratory system was normal, and muscle tone was 5/5. In laboratory evaluation, baseline creatine kinase, alanine aminotransferase and aspartat aminotransferase levels are 36 039 IU·l−1 (normal range 25–170 IU·l−1), 241 IU·l−1 and 450 IU·l−1, respectively. Other laboratory parameters were normal. He was monitored for noninvasive blood pressure using a five-channel EKG, pulse oxymeter in the operating room. The patient was sedated with 0.05 mg·kg−1 midazolam i.v. Oxygen was administered at 2 l·min−1 by facemask. After an additional dose of 20 mg propofol, he was placed in a lateral decubitus position, and lumbar puncture was performed using a midline approach at the L5-S1 intervertebral space with a 26-gauge Atraucan pediatric spinal needle. 1.6 ml of 0.5% hyperbaric bupivacaine was given intrathecally. After the induction of spinal anesthesia, the onset of complete motor block occurred within 5 min, and the sensory block was achieved approaching T6-7 level verified by pin prick test after 5 min. The intraoperative course of patient was comfortable and uneventful throughout the 25 min of surgery. Postoperatively, he was monitored in the recovery room until regression of the sensory block, and he was transferred to the pediatric surgery ward. Sensory and motor function completely recovered 1.5 h after the surgical procedure. Duchenne muscular dystrophy is the most common and severe form of myopathy occurring in pediatric patients (2). Pediatric anesthetists are experienced more of perioperative complications and know how to avoid them during their care for children with DMD undergoing surgery. It is considered that serious problems are associated with general anesthesia (inhalational anesthetic agents or total intravenous anesthesia). The use of regional or local anesthesia seems warranted whenever possible (5). Spinal anesthesia has advantages of reduced drug dosage, avoidance of tracheal intubation and general anesthesia adverse effects, profound sensory and motor block and decreased need for opioid administration (6). In this case, good and rapid recovery and uneventful postoperative period can be achieved with spinal anesthesia. We consider that spinal anesthesia would be a safe and an alternative technique to general anesthesia in children with DMD.

A comparison of the duration and quality of recovery from isoflurane, sevoflurane and desflurane anaesthesia in dogs undergoing magnetic resonance imaging

ObjectiveTo compare the recovery after anaesthesia with isoflurane, sevoflurane and desflurane in dogs undergoing magnetic resonance imaging (MRI) of the brain. Study designProspective, randomized clinical trial. AnimalsThirty‐eight dogs weighing 23.7 ± 12.6 kg. MethodsFollowing pre‐medication with meperidine, 3 mg kg−1 administered intramuscularly, anaesthesia was induced intravenously with propofol (mean dose 4.26 ± 1.3 mg kg−1), the trachea was intubated, and an inhalational anaesthetic agent was administered in oxygen. The dogs were randomly allocated to one of three groups: group I (n = 13) received isoflurane, group S (n = 12) received sevoflurane and group D (n = 13) received desflurane. Parameters recorded included cardiopulmonary data, body temperature, end‐tidal anaesthetic concentration, duration of anaesthesia, and recovery times and quality. Qualitative data were compared using chi‐squared and Fisher's exact tests and quantitative data with anova and Kruskal–Wallis test. Post‐hoc comparisons for quantitative data were undertaken with the Mann–Whitney U‐test. ResultsThe duration of anaesthesia [mean and standard deviation (SD)] in group I was: 105.3 (27.48) minutes, group S: 120.67 (19.4) minutes, and group D: 113.69 (26.68) minutes (p = 0.32). Times to extubation [group I: 8 minutes, (interquartile range 6–9.5), group S: 7 minutes (IQR 5–7), group D: 5 minutes (IQR 3.5–7), p = 0.017] and to sternal recumbency [group I: 11 minutes (IQR 9.5–13.5), group S: 9.5 minutes (IQR 7.25–11.75), group D: 7 minutes (range 3.5–11.5), p = 0.048] were significantly different, as were times to standing. One dog, following sevoflurane, had an unacceptable quality of recovery, but most other recoveries were calm, with no significant difference between groups. Conclusions and clinical relevanceAll three agents appeared suitable for use. Dogs’ tracheas were extubated and the dogs recovered to sternal recumbency most rapidly after desflurane. This may be advantageous for animals with some neurological diseases and for day case procedures.

Effect of inhalational anesthetic agents on muscle relaxation produced by rocuronium

Rocuronium bromide is a non-depolarizing neuromuscular blocking agent with the shortest onset time and intermediate duration of action in the clinical use at present. In clinical scenario, inhalational anesthetic agents can significantly enhance the neuromuscular blockade effect, prolong the duration of action and reduce the dosage of rocuronium. At the same time, inhalational anesthetic agents can retard the reversal of rocuronium by anticholinesterase agents. Above reason had been taken as excuses of earlier stopping or decreasing concentrations of inhalational anesthetic agents to avoid retarding recovery time of mnseular tension and reduce respiratory complieations related to postoperative residual muscular relaxant. Key words: rocuronium; inhalational anesthetic agents; neuromuscular blockade; residual relaxant; rspiratory complications

Therapeutic applications and uses of inhalational anesthesia in the pediatric intensive care unit*

To review the physical properties, end-organ effects, therapeutic applications, and delivery techniques of inhalational anesthetic agents in the pediatric intensive care unit. A computerized, bibliographic search regarding intensive care unit applications of inhalational anesthetic agents. Although the end-organ effects of inhalational anesthetic agents vary depending on the agent, general effects include a dose-related depression of ventilatory and cardiovascular function. With increasing anesthetic depth, there is a decrease in alveolar ventilation with a reduction in tidal volume and an increase in PaCO2 in spontaneously breathing patients. The potent inhalational anesthetic agents decrease mean arterial pressure and myocardial contractility. The decrease in mean arterial pressure reduces renal and hepatic blood flow. Secondary effects on end-organ function may result from the metabolism of these agents and the release of inorganic fluoride. Beneficial effects include sedation, amnesia, and anxiolysis, making these agents effective for sedation during mechanical ventilation. Bronchodilatory and anticonvulsant properties have led to their use as therapeutic agents in patients with refractory status asthmaticus and epilepticus. Issues regarding their delivery in the intensive care unit include equipment for their delivery, scavenging, and monitoring. The literature contains reports of the therapeutic use of the potent inhalational anesthetic agents in the pediatric intensive care unit. Potential applications include sedation during mechanical ventilation as well as therapeutic use for the treatment of status asthmaticus and epilepticus.

Hepatotoxicity after Desflurane Anesthesia in a 15-month-old Child with Mobius Syndrome after Previous Exposure to Isoflurane

HALOGENATED anesthetic agents have been associated with perioperative liver dysfunction and injury. Most cases of hepatotoxicity reported involve halothane exposure. Halothane produces two types of hepatotoxicity. A mild, transient syndrome with modest increases in transaminase enzymes occurs in 20% of patients given halothane. 1 A more severe and fulminant hepatitis with marked liver dysfunction, jaundice, encephalopathy, and even death is observed in 1 in 20,000 anesthetic exposures to halothane. 2 Halothane toxicity occurs in children as well as in adults.3'4 Cross-sensitization between halothane and other volatile agents has been previously reported with isoflurane,5 enflurane, 6-8 and desflurane. 9 ' 10 To date, only four cases of hepatotoxicity in adults were related to desflurane exposure. 9-12 We report the case of a young child who developed acute hepatotoxicity after desflurane anesthesia in the context of two previous isoflurane exposures.

Inhalational anesthetics as preconditioning agents in ischemic brain

While many pharmacological agents have been shown to protect the brain from cerebral ischemia in animal models, none have translated successfully to human patients. One potential clinical neuroprotective strategy in humans may involve increasing the brain's tolerance to ischemia by preischemic conditioning (preconditioning). There are many methods to induce tolerance via preconditioning such as ischemia itself, pharmacological, hypoxia, endotoxin, and others. Inhalational anesthetic agents have also been shown to result in brain preconditioning. Mechanisms responsible for brain preconditioning are many, complex, and unclear and may involve Akt activation, ATP-sensitive potassium channels, and nitric oxide, amongst many others. Anesthetics, however, may play an important and unique role as preconditioning agents, particularly during the perioperative period.

Sevoflurane or halothane with target-controlled sufentanil infusions for coronary artery bypass surgery

Objectives Comparison of hemodynamics, circulatory efficiency, myocardial ischemia and recall during and after sevoflurane or halothane (0.6 MAC {Minimum Alveolar Concentration} inspired) combined with a target-controlled sufentanil infusion (2 ng.ml 1 ) for coronary artery bypass grafting. Methods Prospective randomised non-blinded study in a university teaching hospital of 45 patients undergoing on-pump surgery. Inhalation anesthetic agent was delivered before, during and after cardiopulmonary bypass. Results Intraoperative hemodynamics were maintained within predetermined limits using vasoactive and cardioactive drugs. Heart rate was unchanged from baseline, however the sevoflurane-sufentanil group required more glycopyrrollate, indicating a tendency towards a slower heart rate. In both groups, similar low incidences of myocardial ischemia were detected. After induction of anesthesia, as well as intraoperatively, oxygen consumption decreased by up to 36.6% compared with the awake values in both groups. Oxygen delivery remained unchanged during all measuring periods. Mixed venous oxygen tensions rose after induction, even in patients with cardiac indices below 2.2 L.min 1 .m 2 , indicating maintenance of an effective circulation when utilising these techniques. Twelve hours postoperatively, oxygen consumption exceeded awake values by 31%. No explicit recall was reported by any patient on enquiry on the third postoperative day. Conclusions Low concentrations of sevoflurane or halothane, supplementing target-controlled sufentanil infusions, were both suitable for providing anesthesia for coronary bypass surgery.

Duchenne muscular dystrophy: an old anesthesia problem revisited

Patients with Duchenne and Becker muscular dystrophy suffer from a progressive deterioration in muscle secondary to a defect in the dystrophin gene. As such, they are susceptible to perioperative respiratory, cardiac and other complications, such as rhabdomyolysis. Inhalational anesthetic agents have been implicated as a cause of acute rhabdomyolysis that can resemble malignant hyperthermia (MH). This article reviews perioperative 'MH-like' reactions reported in muscular dystrophy patients and groups them into three categories according to clinical presentation. The etiology and underlying pathophysiological process responsible for these reactions is discussed and recommendations are proposed for the safe anesthetic management of these patients.

Anaesthesia for non-cardiac surgery in a patient with Beckerʼs muscular dystrophy supported with a left ventricular assist device

The Section and Board of Anaesthesiology of the European Union of Medical Specialists aims (EUMS/UEMS) at harmonization of training of anaesthesiologists and at improvement of patient care throughout Europe. Pain medicine is considered to be an area of expertise in anaesthesiology although exclusivity is not claimed. The Section and Board has approved both a core syllabus for pain medicine to be part of the specialist training in anaesthesiology and an additional qualification in pain medicine following the completion of a 5 yr basic specialty training in anaesthesiology. These proposals were prepared by the Working Party on Pain Medicine of the Section and Board. It considers a multidisciplinary approach to pain to contribute to quality in care and has taken the initiative to set up a Multidisciplinary Joint Committee on Pain Medicine within the EUMS/UEMS, for which these guidelines define the area of expertise of anaesthesiology.

Equi-MAC Concentrations of Halothane and Isoflurane Do Not Produce Similar Bispectral Index Values

Minimum alveolar concentration (MAC) has been traditionally used to measure the potency of an inhalational anesthetic agent. Recently, bispectral index (BIS) derived from the frontal cortical electroencephalogram has been used frequently for quantifying the hypnotic component of anesthesia. The present study was designed to examine the BIS values produced by equi-MAC concentrations of halothane and isoflurane. In 34 patients undergoing spinal surgery, BIS and spectral edge frequency (SEF95) were recorded at 3 different concentrations of halothane and isoflurane--namely 0.5, 0.75, and 1.0 MAC. The measurements were made both during wash-in and wash-out phases of the anesthetic agent. Eighteen patients received halothane and 16 received isoflurane. Heart rate, mean arterial pressure, oxygen saturation, and end tidal carbon dioxide pressure values were not different between the 2 groups at various MAC concentrations of the anesthetic agents. BIS and SEF95 values decreased significantly with increasing concentrations of both the anesthetic agents (P<0.001). At any given MAC concentration of the anesthetic, BIS and SEF(95) values were significantly lower under isoflurane compared with halothane anesthesia both during wash-in and wash-out phases (P<0.001). For a given anesthetic agent, BIS values were comparable at equi-MAC concentrations during wash-in and wash-out phases. In conclusion, BIS values are significantly lower under isoflurane compared with halothane anesthesia at similar MAC concentrations. For a given anesthetic agent and a given MAC concentration, the BIS values are similar during wash-in and wash-out phases of anesthesia.

New sensing technology for detection of the common inhalational anesthetic agent sevoflurane using conducting polypyrrole films

A new type of gas sensor to measure resistance was developed to detect sevoflurane concentrations at room temperature. The measured FTIR spectrum of sevoflurane vapor was given. The sensing material polypyrrole was synthesized in situ by UV-photopolymerization. The relative resistance variation was 3.9 for a sevoflurane concentration of 1.2%. The sensor response time (60 s) and recovery time (20 s) were very short. Molecular dynamic calculations made for sevoflurane adsorption on polypyrrole revealed formation of a new bond, N–H–F. The bond length was predicted to be in the range of 0.2–0.4 nm. The bond energy was about 7.2 kcal/mol. Sensor responses to the concentrations 0.1–10% were 1.57–5.9, respectively.

Anesthesia for thoracic surgery in morbidly obese patients

This review considers the anesthetic management of obese patients undergoing thoracic surgery. Extremely or morbidly obese patients differ from patients of normal weight in several ways. Obese patients have altered anatomy and physiology, and usually have associated comorbid medical conditions that may complicate their operative course and increase their risks for postoperative complications. During anesthetic induction and laryngoscopy for tracheal intubation the morbidly obese patient should be in the reverse Trendelenburg position with the head and neck elevated above the table. Placement of a double-lumen tube should be no more difficult in an obese patient than in a normal-weight patient. There are no clear advantages for any of the commonly available inhalational anesthetic agents and each can be used for general anesthesia. With proper attention to their special needs, the morbidly obese patient can safely undergo thoracic surgery and one-lung ventilation.