Identifying and exploring factors influencing career choice, recruitment and retention of anaesthesia trainees in the UK.

BACKGROUND: Many acute hospital specialties are experiencing low recruitment and high attrition of trainees. Understanding what is important to current trainees is critical in terms of identifying and addressing factors which adversely affect recruitment and retention. OBJECTIVES: To identify and explore factors involved in anaesthetic trainees' career decision making. METHODS: This was a mixed methods study using a questionnaire survey (assessing how influential 18 different factors were when choosing anaesthetics, using a five-point Likert scale), supplemented by semi-structured interviews, carried out in August-December 2014, in Scotland, UK. RESULTS: 42/68 (62%) completed responses were received, representing over half of all core (58%) and Acute Care Common Stem (65%) trainees across Scotland. Overall, questionnaire data indicated that the following were most important in career decision making: perceived job satisfaction among those already in the specialty, structured training, the nature of the work (practical, varied, immediate outcomes). Thirteen interviews were carried out. These highlighted that prior positive exposure and experience with anaesthetists encouraged trainees into the specialty. Enthusiastic, supportive colleagues and structured training (including clear milestones, regular teaching and feedback) were considered to enhance the quality of training. Sustainable working conditions, flexibility within programme and out-of-programme opportunities were valued. Respondents reported concerns about the impact of increasing service delivery demands on training quality. CONCLUSIONS: Many of the elements important to today's anaesthetics trainees are related to positive learning and working environments. This fits with research findings from other professional groups. These findings can inform the development of programmes which cultivate trainee commitment to, and enthusiasm for, anaesthetics.

Pharmacokinetic assessment of ketanserin in the horse.

The purpose of this study was to determine the pharmacokinetics (PK) of the 5-HT(2A) receptor antagonist ketanserin in healthy adult horses, and to develop a computational model that could be used to optimize dosing. Plasma concentrations of ketanserin were determined using liquid chromatography with mass spectrometry after single and multiple intravenous administration in the horse. A two-compartment linear pharmacokinetic model described the plasma concentration-time profile of ketanserin after single and multiple doses in healthy horses; the terminal half-life was 11.5 h; steady-state volume of distribution was 10.5 L/kg; AUC was 115 ng · h/mL; and clearance was 0.87 L/h/kg. Model simulations followed by the examination in three healthy horses suggest 0.3 mg/kg q.8 h exhibited linear PK and produced consistent systemic blood concentrations of ketanserin above 3 ng/mL.

Sepsis-From human organ failure to laminar failure.

The horse with gram negative sepsis is known to be at particular risk of succumbing to laminitis. This review summarizes recent evidence indicating that similar pathologic events relating to inflammatory injury occur in laminar failure in laminitis as occur in organ injury/failure in human sepsis. The discussion also points out some important differences between the laminae and target organs in human sepsis that impact the clinical nature of the disease.

Changes in diagnosis with follow-up in an incident cohort of patients with parkinsonism.

BACKGROUND: Accurate diagnosis of the cause of parkinsonism during life can be difficult, particularly at presentation, but few studies have described changes in clinical diagnosis over time and the effect of applying strict research criteria. METHODS: Incident patients with a possible/probable diagnosis of degenerative or vascular parkinsonism had a standardised assessment at diagnosis and at yearly intervals thereafter at which the most likely clinical diagnosis was recorded without strict application of research criteria. Four years after the beginning of the incident period, formal research criteria were applied retrospectively using patient records at baseline and the latest yearly follow-up. RESULTS: Of 82 incident patients, 66 underwent at least 1 year of follow-up. After a median follow-up of 29 months, clinical diagnosis had changed in 22 (33%). Most (82%) changes occurred in the first year and were due to the development of atypical clinical features, particularly early cognitive impairment; the results of brain imaging; responsiveness to levodopa; and the rate of disease progression. Diagnosis on research criteria differed from latest clinical diagnosis in eight participants (12%). Research criteria gave a "probable" diagnosis in 71% of parkinsonian patients at follow-up but in only 15% at the initial assessment. DISCUSSION: The clinical diagnosis of the cause of parkinsonism at presentation was often incorrect, even when made by those with a special interest. In particular, Parkinson's disease was overdiagnosed. Research criteria were often unhelpful in clarifying the diagnosis, even after a median of 29 months of follow-up. Further research is required to identify factors that may be used to improve the accuracy of diagnosis at initial assessment.

The cellular Toll-like receptor 4 antagonist E5531 can act as an agonist in horse whole blood.

Sepsis and endotoxaemia are important causes of morbidity and mortality in humans. Research on sepsis focuses on rodent models most of which are poorly responsive to lipopolysaccharide (LPS), and thus do not mimic very well the high sensitivity of humans. Therefore, there is a need to develop more clinically relevant models. Horses suffer from a similar endotoxaemic syndrome to humans with high morbidity and mortality. LPS analogues that act as antagonists at Toll-like receptor 4 (TLR4) are being developed as novel treatments for endotoxaemia. Due to differences in recognition of ligands by TLR4 from different mammalian species, individual LPS molecules may act as agonists in some species and antagonists in others. The synthetic lipid A analogue E5531 is an antagonist at TLR4 in humans and mice, but its effects at TLR4 from other species are unknown. In the studies reported here, Escherichia coli LPS is a full agonist on equine bone marrow macrophage-like cells and its effects are antagonised by E5531. Similarly, E. coli LPS is an agonist and E5531 an antagonist on monocytes isolated from peripheral blood of healthy horses and human embryonic kidney (HEK) cells, transiently transfected to express horse TLR4 and its associated cell surface proteins MD2 and CD14. In contrast, both E. coli LPS and E5531 behave as agonists in horse whole blood by inducing production of equivalent amounts of the inflammatory mediator prostaglandin. This finding suggests that modification of E5531 may occur in whole blood, for example, deacylation, which alters its activity. This comparative study has revealed a novel pharmacological action of E5531 and emphasises the importance of extending studies of this nature beyond the normal rodent models.

Rapid infusion of a phospholipid emulsion attenuates the effects of endotoxaemia in horses.

REASONS FOR PERFORMING STUDY: Endotoxaemia currently is associated with a poor prognosis in horses. The results of recent trials in other species indicate that phospholipid emulsions reduce the deleterious effects of endotoxin (LPS). However, in a previous study in horses, a 2 h infusion of emulsion caused an unacceptable degree of haemolysis. HYPOTHESIS: Rapid administration of a lower total dose of emulsion would reduce the effects of LPS and induce less haemolysis; the emulsion would reduce inflammatory effects of LPS in vitro. METHODS: Twelve healthy horses received an i.v. infusion either of saline or a phospholipid emulsion (100 mg/kg), followed immediately by E. coli 055:B5 LPS (30 ng/kg). Clinical parameters, haematological profiles, serum tumour necrosis factor (TNF) activity, serum lipid profiles, urine analyses and severity of haemolysis were monitored before and at selected times after LPS. Monocytes were also incubated in vitro with LPS in the presence or absence of emulsion, after which TNF and tissue factor activities were determined. RESULTS: Clinical signs of endotoxaemia were reduced in horses receiving the emulsion, including clinical score, heart rate, rectal temperature, serum TNF activity, and the characteristic leucopenic response to LPS, when compared to horses not receiving the emulsion. Three horses receiving the emulsion had none, 2 had mild and one had moderate haemolysis. There were no differences in urinalysis results and creatinine concentrations, either within the groups over time or between the groups. Serum concentrations of phosphatidylcholine, bile acids and triglycerides peaked immediately after the infusion; there were no significant changes in concentrations of nonesterified fatty acids or cholesterol. Incubation of equine monocytes with emulsion prevented LPS-induced TNF and tissue factor activities. CONCLUSIONS: Rapid administration of emulsion significantly reduced inflammatory effects of LPS in vivo and caused a clinically insignificant degree of haemolysis. The results of the in vitro studies indicate that emulsion prevents not only LPS-induced synthesis of cytokines, but also expression of membrane-associated mediators (i.e. tissue factor). POTENTIAL RELEVANCE: Rapid i.v. administration of emulsions containing phospholipids that bind endotoxin may provide a clinically useful method of treating endotoxaemia in horses.

A Population Pharmacokinetic Model for Vancomycin in Adult Patients Receiving Extracorporeal Membrane Oxygenation Therapy.

The literature on the pharmacokinetics of vancomycin in patients undergoing extracorporeal membrane oxygenation (ECMO) therapy is sparse. A population pharmacokinetic (PK) model for vancomycin in ECMO patients was developed using a nonlinear mixed effects modeling on the concentration-time profiles of 14 ECMO patients who received intravenous vancomycin. Model selection was based on log-likelihood criterion, goodness of fit plots, and scientific plausibility. Identification of covariates was done using a full covariate model approach. The pharmacokinetics of vancomycin was adequately described with a two-compartment model. Parameters included clearance of 2.83 L/hr, limited central volume of distribution 24.2 L, and low residual variability 0.67%. Findings from the analysis suggest that standard dosing recommendations for vancomycin in non-ECMO patients are adequate to achieve therapeutic trough concentrations in ECMO patients. This further shows that ECMO minimally affects the PK of vancomycin in adults including in higher-weight patients.

Resonance Raman spectroscopy reveals novel ligation properties of the porcine myoglobin double mutant H64V/V68H.

A resonance Raman spectroscopic study of the porcine myoglobin double mutant H64V/V68H has confirmed that the ferric form is bis-histidine ligated, has revealed that the bis-histidine ligation is retained on reduction to the ferrous form, and has demonstrated that CO can displace the ligated distal histidine to produce a ferrous CO form which has a low steady-state photolability, indicating that the replacement histidine blocks the CO escape route from the binding site.

A chemometric analysis of the resonance Raman spectra of mutant carbonmonoxy-myoglobins reveals the effects of polarity.

Resonance Raman spectra of 10 carbonmonoxy-myoglobins have been obtained, including sperm whale native, pig wild-type, and the mutants H64L, H64A, V68T, V68N, H64V/V68T, F43W, F46V, and L29F. This series was chosen in order to study the effect of ligand binding pocket polarity on the positions of the v(Fe-CO) and delta (Fe-C-O) bands. Spectra of both 12CO and 13CO isotopic forms have been obtained and a detailed analysis has facilitated the identification of both the ligand-specific bands and six underlying porphyrin bands which are insensitive to this isotopic substitution. Along with a band-fitting analysis of infrared spectra, these resonance Raman data provide a comprehensive evaluation of the vibrations of the FeCO unit. The band positions of the ligand-specific modes are found to depend on the structure of the ligand binding pocket, arising from the strength of back-bonding within the FeCO unit, and clear correlations exist between the v(Fe-CO), delta (Fe-C-O), and v(C-O) band positions which characterize this synergic bonding. The results are consistent with the proposal that the vibration band positions are determined primarily by the electrostatic potential at the ligand. Five discrete band sets are observed for this set of mutants, suggesting that 5 discrete conformations occur.

Thromboxane A2 receptors in equine monocytes: identification of a new subclass of TXA2 receptors.

Thromboxane (TX) A2 has been implicated as an important pathophysiologic mediator of a variety of cardiovascular diseases. Monocytes synthesize TXA2 and it modulates their function. This study sought to characterize monocyte TXA2 receptors. Radioligand binding studies were performed on membranes prepared from equine peripheral blood monocytes using [125I]BOP, a TXA2 receptor agonist. [125I]BOP bound to a single class of binding sites (Kd = 1.0 +/- 0.3 nM and Bmax = 389 +/- 191 fmol/mg protein; n = 5). Several TXA2 receptor agonists and antagonists competed for binding with [125I]BOP. I-BOP produced a concentration-dependent inhibition of endotoxin-induced tumor necrosis factor (TNF) activity (IC50 = 9.6 +/- 2.5 nM; n = 5). In contrast to its effects in platelets and vascular smooth muscle, I-BOP significantly increased cAMP formation in monocytes (EC50 = 22 +/- 3.6 nM; n = 4). The TXA2 receptor antagonists SQ29548 (5.6 microM) and L657925 (0.13 microM) significantly blocked I-BOP-stimulated cAMP formation but did not block 250 nM prostaglandin E2-stimulated cAMP formation. These data support the presence of a TXA2 receptor in equine peripheral blood monocytes. Activation of this receptor results in suppression of endotoxin-induced TNF formation and stimulation of cAMP production. Increased cAMP production after receptor activation suggests that this receptor may represent a unique subclass of TXA2 receptors.

Study of serum amyloid A concentrations as a means of achieving early diagnosis of Rhodococcus equi pneumonia.

REASONS FOR PERFORMING STUDY: Prognosis of Rhodococcus equi pneumonia can be challenging because the course of the disease is often insidious and overt clinical signs are subtle. Early diagnosis is considered desirable because it may offer the chance of more successful implementation of treatment and, thereby, improved outcome. Serological tests have previously failed to be accurate for early detection or diagnosis. Measurement of serum amyloid A (SAA) prior to and at the time of clinical signs was therefore chosen in order to assess its potential clinical use. OBJECTIVE: To determine whether SAA concentrations differentiate foals affected with R. equi pneumonia from unaffected foals, either prior to the onset of disease or at the time of onset of clinical signs. HYPOTHESIS: SAA concentrations are significantly higher among foals that develop R. equi pneumonia than in foals from the same environment that remain clinically unaffected. METHODS: Serum samples were obtained from 212 foals 7-14 days and 196 foals 21-28 days post partum, and from affected foals and age-matched controls at the time of onset of signs of pneumonia. SAA concentration was determined for each sample. RESULTS: There were no significant differences between SAA concentrations of foals with R. equi and clinically unaffected foals during the 2 periods of examination or at the time of onset of clinical signs of R. equi pneumonia. CONCLUSIONS: Concentrations of SAA are variable among foals with R. equi pneumonia and cannot be used reliably either as an ancillary diagnostic tool or to screen for early detection of disease during the first month post partum. POTENTIAL RELEVANCE: Bimonthly monitoring concentration of SAA is not useful as a screening test for early detection of R. equi pneumonia and does not facilitate diagnosis of this disease when used according to the protocol of this study.

Black walnut extract-induced laminitis in horses is associated with heterogeneous dysfunction of the laminar microvasculature.

REASONS FOR PERFORMING STUDY: Equine laminitis purportedly involves haemodynamic dysfunction at the level of the laminar vasculature. However, to date, no studies have been performed characterising the function of laminar arteries and veins during the prodromal stages of equine laminitis. HYPOTHESIS: That the prodromal stages of laminitis are associated with contractile dysfunction of the equine laminar vasculature. OBJECTIVE: To assess contractile function of laminar arteries and veins to phenylephrine (PE) and 5-hydroxytryptamine (5-HT). METHODS: Horses were administered black walnut heartwood extract (BWHE) or water (control horses) via nasogastric intubation. After euthanasia, laminar vessels (100-800 microm internal diameter) were isolated and mounted on small vessel myographs to assess contractile function. RESULTS: Contractile responses to PE or 5-HT were identical in laminar arteries isolated from either control horses or those administered BWHE. In contrast, responses to PE or 5-HT were significantly reduced in laminar veins isolated from BWHE-administered horses when compared with laminar veins isolated from control horses. CONCLUSIONS AND POTENTIAL RELEVANCE: These results are consistent with the prodromal stages of laminitis being associated with selective dysfunction of laminar veins. Further studies are required to discern the precise nature of this dysfunction and its potential relevance to the pathogenesis of acute laminitis in the horse and possible therapeutic targets for treatment.

A case of pituitary adrenocorticotropin-dependent Cushing's syndrome in the horse.

In the horse, a syndrome of hirsutism, hyperglycemia, glucosuria, polydipsia, polyuria, polyphagia, and progressive debilitation has been recognized. Most often the syndrome has been associated with adenomas of the pars intermedia of the pituitary and bilateral adrenal hyperplasia or nodular hyperplasia involving primarily the zona fasciculata. Previously, the syndrome has been ascribed to compression of the hypothalamus by an expanding but functionally inactive pituitary neoplasm. In the present case, with RIA determination of plasma ACTH concentrations, the syndrome was ascribed to pituitary ACTH-dependent hyperadrenocorticism and likened to human Cushing's disease.

Dietary source of omega-3 fatty acids affects endotoxin-induced peritoneal macrophage tumor necrosis factor and eicosanoid synthesis.

The effect of 8 weeks of feeding diets enriched with corn oil, linseed oil, or menhaden oil on endotoxin- and calcium ionophore (A23187)-induced tumor necrosis factor (TNF) and eicosanoid synthesis by rat peritoneal macrophages was determined. The fatty acid composition of macrophage phospholipids and TNF activity and eicosanoid synthesis in response to endotoxin and A23187 were determined. The ratio of omega-6/omega-3 fatty acids in macrophages from linseed oil or menhaden oil-fed rats decreased approximately 24- and 55-fold, respectively. Basal and endotoxin-induced synthesis of TNF was increased by ingestion of the menhaden oil diet but not by the linseed oil diet. Ingestion of the menhaden oil and linseed oil diets significantly reduced basal, endotoxin-, and A23187-induced synthesis of eicosanoids compared with the corn oil group. Ingestion of the menhaden oil diet resulted in a greater decrease in eicosanoid synthesis than the linseed oil diet.

Increased phospholipid mass with decreased arachidonoyl molecular species is associated with decreased eicosanoid synthesis and increased tumor necrosis factor synthesis by thioglycollate-elicited rat peritoneal macrophages.

Because the activation state of macrophages may alter their response to endotoxin, we compared phospholipid arachidonic acid content, and synthesis of eicosanoids and tumor necrosis factor by resident and thioglycollate-elicited rat peritoneal macrophages. Thioglycollate elicitation increased macrophage phospholipid mass twofold, increased the relative percentages of 16:0-20:4 diacylglycerophosphocholine (PtdCho) and 18:0-20:4 diacylglycerophosphoethanolamine (PtdEtn), and decreased the relative percentages of 18:0-20:4 alkenylacylglycerophosphoethanolamine (PlsEtn) and 18:0-20:4 alkylacylglycerophosphocholine (PakCho) compared with resident peritoneal macrophages. Thioglycollate-elicited macrophages synthesized significantly less thromboxane B2, 6-keto-prostaglandin F1 alpha, and prostaglandin E2 and more tumor necrosis factor (TNF) activity in response to both endotoxin and A23187 than did resident macrophages. These results suggest that thioglycollate elicitation decreases specific arachidonic acid-containing molecular species in PlsEtn and PakCho, which may, in part, explain the decrease in eicosanoid and increase in TNF synthesis by thioglycollate-elicited macrophages. The differences between resident and thioglycollate-elicited macrophages in the synthesis of the eicosanoids and TNF activity was not altered by increasing either the concentration of either stimulus or the incubation time.

Effect of intravenous infusion of omega-3 and omega-6 lipid emulsions on equine monocyte fatty acid composition and inflammatory mediator production in vitro.

The effect of intravenous administration of lipid emulsions enriched with omega-3 (n3) and omega-6 (n6) fatty acids on equine monocyte phospholipid fatty acid composition and the synthesis of inflammatory mediators in vitro was evaluated. In a randomized crossover design, horses were infused intravenously with 20% lipid emulsions containing n3 or n6 fatty acids. Monocytes were isolated from the horses before and 0 h, 8 h, 24 h, and 7 days after lipid infusion. Monocyte fatty acid analysis demonstrated incorporation of the parenteral n3 and n6 fatty acids in monocyte phospholipids immediately after infusion, with changes in the fatty acid composition persisting for up to 7 days after infusion. In vitro production of the inflammatory mediators thromboxane B2/thromboxane B3 (TXB(2/3)) and tumor necrosis factor-alpha (TNFalpha) by peripheral blood monocytes was diminished by n3 lipid infusion and was unchanged or increased by n6 lipid infusion. The results of this study demonstrate that short-term infusions of n3 and n6 fatty acid-enriched lipid emulsions alter the fatty acid composition of equine monocyte phospholipids and modify the inflammatory response of these cells in vitro. These results also support further investigation into the use of parenteral n3 fatty acids as part of the supportive therapy of patients with multiple organ dysfunction (MODS) or systemic inflammatory response syndrome (SIRS).

Genomic characterization of equine interleukin-4 receptor alpha-chain (IL4R).

Three overlapping fragments of the equine interleukin-4 receptor alpha chain gene (IL4R) were cloned and sequenced. The resulting 3553 bp cDNA sequence exhibited homology to human, murine and bovine IL4R. The equine IL4R exhibits many conserved features when compared to other species, including intron-exon boundary positions and amino acid sequence motifs characteristic of type I cytokine receptors. The IL4R gene was localized to horse chromosome ECA13 by synteny mapping on a somatic cell hybrid panel. Evidence for an alternative splice variant of IL4R was found in the genomic sequence and subsequently verified using RT-PCR on equine monocyte RNA. A polymorphism screen of the largest exon, homologous to exon 12 of the human IL4R gene, was performed using DNA from 60 horses of various breeds which yielded 11 coding-region single nucleotide polymorphisms (SNPs), 7 synonymous and 4 non-synonymous. Three of the four non-synonymous SNPs occur at high frequencies and are found very near a conserved tyrosine residue.

Effects of a specific thromboxane synthetase inhibitor in equine endotoxaemia.

Thromboxane A2 may play a major role in circulatory shock. In some species, thromboxane synthetase inhibitors have a beneficial effect on shock induced by endotoxin, trauma, sepsis and administration of arachidonate. In some shock models, however, results with thromboxane synthetase inhibitors have been conflicting. The effect of UK-38,485, a selective thromboxane inhibitor, was evaluated in ponies injected with endotoxin intraperitoneally. Four groups of ponies were used to compare the effects of endotoxin alone, UK-38,485 alone, treatment with UK-38,485 before endotoxin challenge and treatment with UK-38,485 after endotoxin challenge. Haematological, metabolic, eicosanoid and clinical responses in each group were evaluated. The results indicated that UK-38,485 is an effective inhibitor of thromboxane A2 generation following endotoxin challenge. Prostacyclin values were elevated compared with baseline in ponies administered UK-38,485 and endotoxin. However, prostacyclin values were not significantly different from those of ponies receiving endotoxin alone. Furthermore, UK-38,485 failed to attenuate the haematological, metabolic and clinical manifestations commonly seen in the pony after endotoxin challenge.

Effects of flunixin meglumine, phenylbutazone and a selective thromboxane synthetase inhibitor (UK-38,485) on thromboxane and prostacyclin production in healthy horses.

The efficacy of three agents which alter the metabolism of arachidonic acid was investigated in normal, conscious horses. A dose response evaluation was made of flunixin meglumine and phenylbutazone, two cyclo-oxygenase inhibitors, and of a selective thromboxane synthetase inhibitor, UK-38,485. Radioimmunoassay of thromboxane B2 (TxB2) and 6-keto prostaglandin F1 alpha (PGF1 alpha) was used to assess the concentrations of thromboxane A2 (TxA2) and prostacyclin (PGI2) respectively, in serum. Flunixin was the most potent inhibitor of serum TxB2 and 6-keto PGF1 alpha production. UK-38,485 also decreased serum TxB2 generation while significantly increasing serum 6-keto PGF1 alpha levels, thus confirming its selectivity as a thromboxane synthetase inhibitor.

Effects of an infusion of dopamine on the cardiopulmonary effects of Escherichia coli endotoxin in anaesthetised horses.

Horses with colic may be endotoxaemic and subsequently develop hypotension during anaesthesia for surgical operation. The aim of this study was to evaluate the efficacy of dopamine as a means to improve cardiovascular function in anaesthetised endotoxaemic horses. Nine horses (five in group 1 and four in group 2) were anaesthetised with thiopentone and guaifenesin and anaesthesia was maintained with halothane. After approximately one hour, facial artery pressure, heart rate, pulmonary artery pressure, cardiac output, temperature, pHa, PaCO2, PaO2, base excess, packed cell volume, plasma protein concentration and white cell count were measured (time 0). Escherichia coli endotoxin was infused intravenously over 15 minutes in both groups. Group 2 horses were given an intravenous infusion of dopamine (5 micrograms kg-1 min-1) starting five minutes after the start of the endotoxin infusion and continuing for 60 minutes. Measurements were made at 15 minute intervals for 120 minutes. In group 1, one horse died during the endotoxin infusion and in two other horses mean facial artery pressures decreased to 50 mm Hg. Total pulmonary vascular resistance and packed cell volume were significantly increased. Cardiac output, cardiac index and change in mean arterial pressure were significantly greater in group 2 horses than in group 1 horses. Conversely, diastolic pulmonary artery pressure, total vascular resistance and total pulmonary resistance were significantly less in group 2 than in group 1. PaO2, base excess and white blood cell count were significantly decreased in both groups. It was concluded that dopamine improved cardiovascular function in the presence of endotoxaemia and attenuated the rate of haemoconcentration, but had no effect on the development of decreased PaO2 or metabolic acidosis.