A Comparison of the Effects of Prolonged (>10 Hour) Low-flow Sevoflurane, High-flow Sevoflurane, and Low-flow Isoflurane Anaesthesia on Hepatorenal Function in Orthopaedic Patients

An Accessible Clinical Decision Support System to Curtail Anesthetic Greenhouse Gases in a Large Health Network: Implementation Study

BACKGROUND

Inhaled anesthetics in the operating room are potent greenhouse gases and are a key contributor to carbon emissions from health care facilities. Real-time clinical decision support (CDS) systems lower anesthetic gas waste by prompting anesthesia professionals to reduce fresh gas flow (FGF) when a set threshold is exceeded. However, previous CDS systems have relied on proprietary or highly customized anesthesia information management systems, significantly reducing other institutions' accessibility to the technology and thus limiting overall environmental benefit.

OBJECTIVE

In 2018, a CDS system that lowers anesthetic gas waste using methods that can be easily adopted by other institutions was developed at the University of California San Francisco (UCSF). This study aims to facilitate wider uptake of our CDS system and further reduce gas waste by describing the implementation of the FGF CDS toolkit at UCSF and the subsequent implementation at other medical campuses within the University of California Health network.

METHODS

We developed a noninterruptive active CDS system to alert anesthesia professionals when FGF rates exceeded 0.7 L per minute for common volatile anesthetics. The implementation process at UCSF was documented and assembled into an informational toolkit to aid in the integration of the CDS system at other health care institutions. Before implementation, presentation-based education initiatives were used to disseminate information regarding the safety of low FGF use and its relationship to environmental sustainability. Our FGF CDS toolkit consisted of 4 main components for implementation: sustainability-focused education of anesthesia professionals, hardware integration of the CDS technology, software build of the CDS system, and data reporting of measured outcomes.

RESULTS

The FGF CDS system was successfully deployed at 5 University of California Health network campuses. Four of the institutions are independent from the institution that created the CDS system. The CDS system was deployed at each facility using the FGF CDS toolkit, which describes the main components of the technology and implementation. Each campus made modifications to the CDS tool to best suit their institution, emphasizing the versatility and adoptability of the technology and implementation framework.

CONCLUSIONS

It has previously been shown that the FGF CDS system reduces anesthetic gas waste, leading to environmental and fiscal benefits. Here, we demonstrate that the CDS system can be transferred to other medical facilities using our toolkit for implementation, making the technology and associated benefits globally accessible to advance mitigation of health care-related emissions.

Hemodynamic parameters of low-flow isoflurane and low-flow sevoflurane anesthesia during controlled ventilation with laryngeal mask airway

Background:

Nowadays laryngeal mask airway (LMA) is popular as one of the best choices for airway management. Low-flow anesthesia has some advantages like lower pollution, hemodynamic stability and cost effectiveness. Volatile anesthetics are widely used for anesthesia maintenance during operations. Sevoflurane has more hemodynamic stability compared to isoflurane, but there are few studies comparing the hemodynamic stabilities of these two anesthetics during controlled low flow anesthesia with LMA.

Objectives:

The aim of this study was to compare the effects of low-flow sevoflurane and low-flow isoflurane on hemodynamic parameters of patients through LMA.

Patients and Methods:

Eighty patients, scheduled for elective ophthalmic surgery, were randomly divided into two groups. After induction, an LMA with an appropriate size was inserted in all the patients and they were randomly allocated to two groups of low-flow sevoflurane (n = 40) and low-flow isoflurane (n = 40). Hemodynamic parameters (heart rate (HR), systolic blood pressure (SBP), diastolic blood pressure (DBP) and Mean Arterial Pressure (MAP) were recorded at 5, 10, 15, 20, 25 and 30 minutes after the anesthesia induction.

Results:

The mean heart rate values were significantly less in the sevoflurane group (P value < 0.05) at 25 minutes after the surgery. The mean Blood Pressure in the isoflurane group was significantly higher compared with the sevoflurane group in 10, 20 and 30 minutes after the surgery (P values = 0.0131, 0.0373 and 0.0028, respectively). These differences were clinically unimportant because heart rate and mean blood pressure were on normal ranges.

Conclusions:

Seemingly, low-flow sevoflurane with LMA did not have any significant hemodynamic effect on clinical practice. Therefore, low-flow sevoflurane anesthesia with LMA might be considered in patients with short operations who need rapid recovery from anesthesia.

Establishing the relationship between FGF/MV and FI/FD, and determining the saturation state of sevoflurane anaesthesia during the induction phase and factors affecting nonrespiratory tract ejection volume

OBJECTIVES

To investigate (i) the relationship between the ratio of fresh gas flow to min volume (FGF/MV) and the ratio of the fraction of inspired sevoflurane to the delivered concentration of sevoflurane (FI/FD); (ii) to establish the saturation state of sevoflurane anaesthesia and factors affecting the volume of ejected sevoflurane through the nonrespiratory tract route (nVERT) during the saturation state.

METHODS

Two studies were undertaken in patients with cancer, scheduled to undergo surgery. All patients received tracheal intubation and inhaled sevoflurane. In study 1, anaesthesia parameters were fixed, the initial FD of sevoflurane was 2.2% vol and the FGF/MV was set to 0.2, 0.3, 0.4 and 1.0 in groups A, B, C and D, respectively. In study 2, FGF = MV and the initial FD of sevoflurane was 2.2% vol, but the tidal volume (TV) was set to 6, 8 or 10 ml/kg in groups I, II and III, respectively.

RESULTS

Study 1 (n = 60) showed a positive relationship between FI/FD and FGF/MV. In study 2 (n = 60), when TV was fixed, nVERT increased during the saturation state as FD increased; when FD was fixed, nVERT remained stable, despite increased TV.

CONCLUSIONS

FI/FD is positively associated with FGF/MV; nVERT is affected by FD but not TV.

Minimum alveolar concentration of sevoflurane in rabbits with liver fibrosis

BACKGROUND

Sevoflurane is widely used in patients undergoing surgical procedures, which could affect both the liver function and hepatic blood flow. However, the effects of liver fibrosis on minimum alveolar concentration (MAC) of sevoflurane are still unclear. Therefore, we designed this study to determine the MAC of sevoflurane in rabbits with liver fibrosis.

METHODS

Thirty male New Zealand white rabbits weighing approximately 2.5 kg were divided randomly into 2 groups: fibrosis (n = 20) and normal control group (n = 10). The rabbits in the fibrosis group were treated with 50% carbon tetrachloride for 12 weeks to induce liver fibrosis. The serum concentration of total protein, albumin, globulin, total bile acids, alanine aminotransferase, aspartame aminotransferase, alkaline phosphatase, γ-glutamyl transpeptidase, total bilirubin, direct bilirubin, and indirect bilirubin were measured before anesthesia. The anesthesia for animals that survived in both groups was induced and maintained with sevoflurane. A standard tail-clamp technique was used to determine the MAC of sevoflurane in spontaneously breathing rabbits. After anesthesia, animals were killed for liver pathologic examination.

RESULTS

Twelve weeks after 50% carbon tetrachloride administration, 14 of 20 rabbits survived in the fibrosis group, and 9 of 10 survived in the control group. All surviving animals in the fibrosis group had developed moderate to severe liver fibrosis. Three rabbits that survived after the fibrosis challenge were excluded for other diseases or no response to pain stimulation. The levels of globulin, aspartame aminotransferase, and γ-glutamyl transpeptidase significantly increased in fibrosis animals compared with controls. However, the albumin and alkaline phosphatase levels were significantly lower in the fibrosis group than in the control group. Mean arterial blood pressure, heart rate, end-tidal CO(2), and temperature were stable in both groups during sevoflurane anesthesia. The MAC of sevoflurane was significantly less in the fibrosis group than in the control group (3.52% vs 4.10%, P = 0.018).

CONCLUSION

The MAC of sevoflurane decreased significantly in rabbits with liver fibrosis.

Analysis of the composition of 'original' and generic sevoflurane in routine use

BACKGROUND

Original sevoflurane (Sevofrane) contains a small amount of water, which can inhibit the production of hydrofluoric acid. Hydrofluoric acid is highly pungent, and sevoflurane that contains a high concentration of hydrofluoric acid is not suitable for volatile induction of anaesthesia. Recently, generic sevoflurane (Sevoness) has become available in some countries. The generic product is produced by a different method and kept in a different kind of bottle. We questioned whether the original and generic sevoflurane differed in their composition and thus might differ in their resistance to degradation.

METHODS

Sevoflurane from groups of three bottles of Sevofrane and three bottles of Sevoness was kept in the bottle at 24-37 degrees C for 2 weeks or in two kinds of vaporizer for 3 days, and the resulting contents measured by gas chromatography.

RESULTS

Both products contained sevoflurane concentrations exceeding 99.998%. Fluoride ion concentration did not differ between the products (0.043 ppm). The original sevoflurane contained more (0.07% w/v) water than the generic anaesthetic (0.003% w/v). Original sevoflurane contained 5 ppm compound A, 10 ppm sevomethylether, and 5 ppm of unknown materials. Generic sevoflurane contained 32 ppm hexafluoroisopropanol and 12 ppm of unknown materials. While stored in a vaporizer for 3 days, the water content in the original sevoflurane decreased by two-thirds but the water in the generic sevoflurane increased by a factor of three-fold.

CONCLUSIONS

Generic sevoflurane contains high-quality sevoflurane and only a small amount of fluoride ions, making it comparable with the original sevoflurane product.

Inhalational or intravenous anesthetics for craniotomies? Pro inhalational

PURPOSE OF REVIEW

In neurosurgery, anesthesiologists and surgeons focus on the same target - the brain. The nature of anesthetics is to interact with brain physiology, leading to favorable and adverse effects. Research in neuroanesthesia over the last three decades has been dedicated to identifying the optimal anesthetic agent to maintain coupling between cerebral blood flow and metabolism, keep cerebrovascular autoregulation intact, and not increase cerebral blood volume and intracranial pressure.

RECENT FINDINGS

Sevoflurane is less vasoactive than halothane, enflurane, isoflurane, or desflurane. The context sensitive half-life is short and similar to that of desflurane, which translates into fast on and offset. Compared with propofol, sevoflurane decreases cerebral blood flow to a lesser extent, while cerebral metabolism is suppressed to the same degree. Sevoflurane does not increase intracranial pressure, while propofol decreases intracranial pressure.

SUMMARY

In neurosurgical patients with normal intracranial pressure, sevoflurane might be a good alternative to propofol. In patients with reduced intracranial elastance, caused by space occupying lesions, with elevated intracranial pressure or complex surgical approaches, propofol should remain first choice.

Gene expression profiling of nephrotoxicity from the sevoflurane degradation product fluoromethyl-2,2-difluoro-1-(trifluoromethyl)vinyl ether ("compound A") in rats

The major degradation product of the volatile anesthetic sevoflurane, the haloalkene fluoromethyl-2,2-difluoro-1-(trifluoromethyl)vinyl ether (FDVE or "compound A"), is nephrotoxic in rats. FDVE undergoes complex metabolism and bioactivation, which mediates the nephrotoxicity. Nevertheless, the molecular and cellular mechanisms of FDVE toxification are unknown. This investigation evaluated the gene expression profile of kidneys in rats administered a nephrotoxic dose of FDVE. Male Fischer 344 rats (five per group) received 0.25 mmol/kg intraperitoneal FDVE or corn oil (controls) and were sacrificed after 24 or 72 h. Urine output and kidney histological changes were quantified. Kidney RNA was extracted for microarray analysis using Affymetrix GeneChip Rat Expression Array 230A arrays. Quantitative real-time PCR confirmed the modulation of several genes. FDVE caused significant diuresis and necrosis at 24 h, with normal urine output and evidence of tubular regeneration at 72 h. There were 517 informative genes that were differentially expressed >1.5-fold (p < 0.05) versus control at 24 h, of which 283 and 234 were upregulated and downregulated, respectively. Major classes of upregulated genes included those involved in apoptosis, oxidative stress, and inflammatory response (mostly at 24 h), and regeneration and repair; downregulated genes were generally associated with transporters and intermediary metabolism. Among the quantitatively most upregulated genes were kidney injury molecule, osteopontin, clusterin, tissue inhibitor of metalloproteinase 1, and TNF receptor 12, which have been associated with other forms of nephrotoxicity, and angiopoietin-like protein 4, glycoprotein nmb, ubiquitin hydrolase, and HSP70. Microarray results were confirmed by quantitative real-time PCR. FDVE causes rapid and brisk changes in gene expression, providing potential insights into the mechanism of FDVE toxification, and potential biomarkers for FDVE nephrotoxicity which are more sensitive than conventional measures of renal function.