Replacement tunnelled dialysis catheters for haemodialysis access: Same site, new site, or exchange - a multivariate analysis and risk score.

AIM: To identify variables related to complications following tunnelled dialysis catheter (TDC) replacement and stratifying the risk to reduce morbidity in patients with end-stage renal disease. MATERIALS AND METHODS: One hundred and forty TDCs (Split Cath, medCOMP) were replaced in 140 patients over a 5 year period. Multiple variables were retrospectively collected and analysed to stratify the risk and to predict patients who were more likely to suffer from complications. Multivariate regression analysis was used to identify variables predictive of complications. RESULTS: There were six immediate complications, 42 early complications, and 37 late complications. Multivariate analysis revealed that variables significantly associated to complications were: female sex (p = 0.003; OR 2.9); previous TDC in the same anatomical position in the past (p = 0.014; OR 4.1); catheter exchange (p = 0.038; OR 3.8); haemoglobin <11 g/dl (p = 0.033; OR 3.6); albumin <30 g/l (p = 0.007; OR 4.4); prothrombin time >15 s (p = 0.002; OR 4.1); and C-reactive protein >50 mg/l (p = 0.007; OR 4.6). A high-risk score, which used the values from the multivariate analysis, predicted 100% of the immediate complications, 95% of the early complications, and 68% of the late complications. CONCLUSION: Patients can now be scored prior to TDC replacement. A patient with a high-risk score can be optimized to reduce the chance of complications. Further prospective studies to confirm that rotating the site of TDC reduces complications are warranted as this has implications for current guidelines.

Inferior vena cava filter use in pregnancy: preliminary experience.

Thromboembolism is the most common direct cause of maternal mortality in the UK. Inferior vena cava (IVC) filter placement is indicated in conditions where recurrent thromboembolism occurs despite adequate anticoagulation or when anticoagulation is contraindicated. The safety of IVC filter use in pregnancy is uncertain, as there are limited data available. In this study, we have reviewed pregnancy outcome in women with IVC filter use. Twelve pregnancies in six women, delivered in our hospital in the past 11 years, were identified from obstetric and radiology databases to have an IVC filter in situ. In four pregnancies, an IVC filter was placed during pregnancy. In eight pregnancies, an IVC filter was already in situ before pregnancy and continued for the entire duration of pregnancy. There were no antenatal complications noted due to IVC filter placement and no recurrent thromboembolism noted in pregnancies with an IVC filter in situ before conception. The mode of delivery was based on obstetric reasons in all cases. The mean birthweight was 2982 g, and all babies were born in good condition with Apgar scores within normal range. In conclusion, this case series did not identify any problems associated with IVC filter placement or continuation in pregnancy.

The rate of alveolar-capillary uptake of sevoflurane and nitrous oxide following anaesthetic induction.

The rate of anaesthetic gas uptake from the breathing system has been extensively measured, but this does not reflect the true rate of early gas uptake by pulmonary blood, which drives inhalational induction of anaesthesia. In eight patients undergoing coronary bypass surgery, we measured the rate of alveolar-capillary uptake of anaesthetic gases up to 30 min following introduction of 0.5% sevoflurane and 33% nitrous oxide using the reverse Fick method, in which blood partial pressures were measured using a headspace equilibration technique. Simultaneous measurements of gas uptake from the breathing system were made by indirect calorimetry. Measured rates of sevoflurane and nitrous oxide uptake from the breathing system agreed well with previously described formulae when adjusted for inspired concentration. The time course of alveolar-capillary gas uptake followed a characteristic rising curve peaking at 3-4 min and then exponentially declining, and for nitrous oxide was significantly higher than previously estimated.

Subsidiary class III effects of beta blockers? A comparison of atenolol, metoprolol, nadolol, oxprenolol and sotalol.

The electrophysiological effects of various concentrations of atenolol, metoprolol, nadolol, D-oxprenolol, L-oxprenolol, and D, L-oxprenolol and D-sotalol, L-sotalol, and D, L-sotalol were compared in rabbit right ventricular papillary muscle studied in vitro using intracellular microelectrodes. An assessment of the relative beta blocking effects of D-sotalol and D, L-sotalol against the inotropic action of isoprenaline was made in the same preparation. Of the drugs tested, only oxprenolol and sotalol showed prolongation of action potential duration and effective refractory period (class III action), with oxprenolol showing, in addition, depression of maximal upstroke velocity and the presence of post-repolarisation refractoriness (class I action). When contrasted at clinically relevant concentrations, only sotalol retained a class III effect, without any actions on variables related to fast inward current. The effects of oxprenolol and sotalol were not found to be stereospecific. The mechanical experiments indicate that, in this preparation, D-sotalol has approximately one-fourteenth of the beta blocking potency of the racemic compound. It therefore merits further consideration as a useful alternative class III antiarrhythmic agent, which would be free from the side effects of beta receptor blocking treatment.

Ventilation-perfusion inhomogeneity increases gas uptake: theoretical modeling of gas exchange.

Ventilation-perfusion (VA/Q) inhomogeneity was modeled to measure its effect on gas exchange in the presence of inspired mixtures of two soluble gases using a two-compartment computer model. Theoretical studies involving a mixture of hypothetical gases with equal solubility in blood showed that the effect of increasing inhomogeneity of distributions of either ventilation or blood flow is to paradoxically increase uptake of the gas with the lowest overall uptake in relation to its inspired concentration. This phenomenon is explained by the concentrating effects that uptake of soluble gases exert on each other in low VA/Q compartments. Repeating this analysis for inspired mixtures of 30% O(2) and 70% nitrous oxide (N(2)O) confirmed that, during "steady-state" N(2)O anesthesia, uptake of N(2)O is predicted to paradoxically increase in the presence of worsening VA/Q inhomogeneity.

Ventilation-perfusion inhomogeneity increases gas uptake in anesthesia: computer modeling of gas exchange.

Ventilation-perfusion (VA/Q) inhomogeneity was modeled to measure its effect on overall gas exchange during maintenance-phase N(2)O anesthesia with an inspired O(2) concentration of 30%. A multialveolar compartment computer model was used based on physiological log normal distributions of VA/Q inhomogeneity. Increasing the log standard deviation of the distribution of perfusion from 0 to 1.75 paradoxically increased O(2) uptake (VO(2)) where a low mixed venous partial pressure of N(2)O [high N(2)O uptake (VN(2)O)] was specified. With rising mixed venous partial pressure of N(2)O, a threshold was observed where VO(2) began to fall, whereas VN(2)O began to rise with increasing VA/Q inhomogeneity. This phenomenon is a magnification of the concentrating effects that VO(2) and VN(2)O have on each other in low VA/Q compartments. During "steady-state" N(2)O anesthesia, VN(2)O is predicted to paradoxically increase in the presence of worsening VA/Q inhomogeneity.

Effect of ventilation-perfusion inhomogeneity and N(2)O on oxygenation: physiological modeling of gas exchange.

Ventilation-perfusion (VA/Q) inhomogeneity was modeled to measure its effect on arterial oxygenation during maintenance-phase anesthesia involving an inspired mixture of 30% O(2) and either N(2)O or N(2). A multialveolar compartment computer model was constructed based on a log normal distribution of VA/Q inhomogeneity. Increasing the log SD of the distribution of blood flow from 0 to 1.75 produced a progressive fall in arterial PO(2) (Pa(O(2))). The fall was less steep in the presence of N(2)O than when N(2) was present instead. This was due mainly to the concentrating effect of N(2)O uptake on alveolar PO(2) in moderately low VA/Q compartments. The improvement in Pa(O(2)) when N(2)O was present instead of N(2) was greatest when the degree of VA/Q inhomogeneity was in the range typically seen in anesthetized patients. Models based on distributions of expired and inspired alveolar ventilation give quantitatively different results for Pa(O(2)). In the presence of VA/Q inhomogeneity, second-gas and concentrating effects may have clinically significant effects on arterial oxygenation even at "steady-state" levels of N(2)O uptake.

Development and in vitro validation of a device for measuring non-shunt cardiac output by nitrous oxide throughflow.

A system has been developed for measuring non-shunt cardiac output by the throughflow technique, using nitrous oxide in patients undergoing general anaesthesia. The throughflow measurement technique is a non-invasive method based on inert gas throughflow theory. In vitro validation of the measurement system was performed using a lung gas exchange simulator. The accuracy and precision of the throughflow measurement system was assessed by comparing measured and target values for five simulated values of non-shunt cardiac output, from 2.88 to 9.86 l min(-1). This showed an overall mean bias of -0.031 min(-1) (range -0.00 to -0.101 min(-1)), with a mean coefficient of variation of the difference of 1.39% (1.20-1.93%). These results indicate that the measurement system is suitable for monitoring the non-shunt cardiac output in patients undergoing general anaesthesia using nitrous oxide throughflow.

Haemostasis during carpal tunnel release under local anaesthesia: a controlled comparison of a tourniquet and adrenaline infiltration.

A randomized controlled comparison of tourniquet and local adrenaline infiltration for control of bleeding was performed in patients undergoing bilateral carpal tunnel release under local anaesthesia. Visual analogue scores for intra-operative pain were substantially greater for tourniquet (mean score 4.7) than for adrenaline (2.2). Incomplete control of bleeding was responsible for longer operating time and for the surgeons' perception of slightly greater operative difficulty with the use of adrenaline. There were no complications attributable to the use of adrenaline. The use of adrenaline-containing local anaesthesia for carpal tunnel release avoids tourniquet pain and is preferred by patients.

Problems in general anaesthesia. Emergencies and trauma.

Emergencies resulting in death of the patient are sufficient reason for insisting on only medically qualified people giving anaesthetics. Unlike in most other specialities, complications in anaesthesia usually will not await the arrival of the expert. Trauma provides the anaesthetist with some of his most testing occasions. Most problems are related, as with emergencies, to basic derangements of respiratory and circulatory physiology However, there is a steady progression with severe trauma cases that is not a common feature of the ordinary anaesthetic disaster. Respiratory problems are either of obstructive origin or due to failure to generate respiratory muscle activity. Circulatory problems, in the vast majority of cases, consist of low cardiac output because of relatively deficient circulatory blood volume. Overload of the circulation resulting in acute pulmonary oedema is often feared but uncommonly seen. Another cause of failure of output of the heart lies in the heart itself, either because heart muscle is not contracting well enough--myocardial failure, or because of disorder of rhythm.

Patterns of renal angiomyolipoma regression post embolisation on medium- to long-term follow-up.

OBJECTIVE: To assess the patterns of regression of renal angiomyolipoma (AML) post embolisation and report the outcomes related to the use of different embolic materials. METHODS: A retrospective review of all patients who underwent embolisation for renal AML at our institution between January 2004 and April 2012. RESULTS: 13 patients underwent 16 episodes of embolisation. Coils were used as the primary embolisation material in 10 episodes and microspheres in 6 episodes. The size reduction rate highly correlated on CT follow-up between the two groups, with 25.6% vs 22.7% reduction at 12 months, 27.5% vs 25.1% at 24 months, 35.0% vs 33.0% at 36 months and 35.0% vs 36.8% at 48 months. During follow-up, all tumours reduced in size with one patient requiring subsequent embolisation whose tumour reduced by only 6.5% after 1 year and subsequently exhibited regrowth after 4 years. Two patients presented with rebleeding and underwent repeat embolisation. Our overall retreatment rate (23%) is well within the literature range (up to 37%). None of the patients underwent surgery. CONCLUSION: The majority of AML shrinkage occurs within the first year following embolisation and appears to plateau after 3 years, which could have an impact on follow-up strategy. The percentage reduction at 1 year may reflect the long-term effect of embolisation with tumours demonstrating minor size reduction more likely to relapse at long-term follow-up. Embolisation of renal AML produces durable long-term results regardless of the choice of embolic agent. ADVANCES IN KNOWLEDGE: These findings provide information to guide CT follow-up of renal AML post embolisation.

Primary infrarenal aortic stenting with or without iliac stenting for isolated and aortoiliac stenoses: single-centre experience with long-term follow-up.

PURPOSE: The purpose of this study was to evaluate the technical success, complications, long-term clinical outcome, and patency after primary infrarenal aortic stenting for aortic and aortoiliac stenosis. Between January 1999 and January 2006, 22 consecutive patients underwent endovascular treatment because of infrarenal aortic stenosis with and without common iliac stenosis (10 men; mean age 64 ± 14 years). Eleven (11 of 22) patients had an isolated aortic stenosis, whereas 11 of 22 had aortic stenosis that extended into the common iliac arteries (CIAs). Thirteen patients were Rutherford classification type 3, and 9 patients were type 4. Statistical analysis included paired Student t test and Kaplan-Meier life table analysis; p < 0.05 was considered significant. Technical and initial clinical success was achieved in all patients. There were three (14 %) procedure-related complications, which included two access-point pseudoaneurysms and one non-flow-limiting left external iliac dissection. Patients were followed-up for a mean period of 88 months (range 60-132). Mean preprocedure ankle brachial pressure indexes (ABPI) were 0.60 ± -0.15 (right) and 0.61 ± -0.16 (left). After the procedure they were 0.86 ± -0.07 (right) and 0.90 ± -0.09 (left). The increase in ABPI was significant (p < 0.05), and this continued throughout follow-up. Four (18 %) patients had recurrence of symptoms during follow-up. These occurred at 36, 48, 48, and 50 months after the original procedure. All four patients were successfully treated with repeat angioplasty procedures. There was a significant difference in primary patency between isolated aortic stenosis (100 %) and aortoiliac stenosis (60 %) (p = 0.031). Cumulative follow-up was 1920 months yielding a reintervention rate of 0.025/events/year. CONCLUSION: Primary stenting of infrarenal stenosis is safe and successful with a low reintervention rate. It should be considered as first-line treatment for patients with infrarenal aortic stenotic disease.

Clinical outcomes following endovascular treatment of the malfunctioning autologous dialysis fistula.

BACKGROUND: There is limited long-term prospective data on the use of endovascular techniques and the use of thrombolysis in malfunctioning autologous haemodialysis fistulas. PURPOSE: Prospective assessment of clinical outcomes following angioplasty with or without low-dose thrombolysis was undertaken in patients who presented with malfunctioning autologous haemodialysis fistulas. METHODS: Consecutive patients referred to our department over a 6-month period were included. Twenty-five patients underwent percutaneous intervention by angioplasty alone (n = 14), angioplasty and stent (n = 2), thrombolysis alone (n = 2), angioplasty, thrombolysis and stent (n = 2) and angioplasty and thrombolysis (n = 5). Patients underwent clinical follow-up and were reviewed at 6, 12, 18 and 24 months to determine fistula status. Thirty-day mortality in the group was two patients. Statistical analysis was performed with Mann-Whitney, chi-squared and Kruskal-Wallis tests. Kaplan-Meier curves were constructed to compare primary and secondary patency rates. RESULTS: Technical success and initial clinical success rates were 88% and 76%, respectively. Primary and secondary clinical success rates at 6 months were 68% and 72%, at 12 months were 68% and 72%, at 18 months were 60% and 68% and at 24 months were 52% and 68%, respectively. There were no major complications following interventional procedures. There were four minor complications. After an initially successful procedure, five patients required subsequent intervention during the follow-up period. The overall fistula event rate was very low (five per 600 patient months or 0.0996 per access year) with a fistula loss rate of 0.14 per access year. CONCLUSIONS: Our results confirm that excellent clinical results can be achieved by percutaneous endovascular treatment in malfunctioning autologous fistulas, justifying their continued use as first-line management.

Laboratory validation of the M-COVX metabolic module in measurement of oxygen uptake.

A practical method of breath-by-breath monitoring of metabolic gas exchange has previously been developed by GE Healthcare and can now be easily incorporated into existing anaesthetic and critical care monitoring (M-COVX). Previous research using this device has shown good accuracy and precision between the M-COVX measurements and a traditional measurement of gas uptake at the mouth and also against the reverse Fick method during cardiac surgery and critical care, but its accuracy in the paediatric situation and across a range of ventilatory settings awaits validation. We tested the M-COVX metabolic monitor in the laboratory comparing its measurement to a traditional Haldane transformation across a wide range of oxygen consumption values, from 50 ml/minute to just under 300 ml/minute, typical of those expected in anaesthetised adults and children. The M-COVX device showed acceptable accuracy with an overall mean bias of -3.3% (range -15.1 to +4.2%, P = 0.21). Excellent linearity was found, by y = 0.96x + 0.5 ml/minute, r = 0.99. The device showed acceptable robustness to ventilatory changes examined, including changes in respiratory rate, I:E ratio, FiO2 up to 75% and simulated spontaneous breathing. However any induced leak from around the simulated endotracheal tube caused a significant error in paediatric scenarios.

In vivo validation of the M-COVX metabolic monitor in patients under anaesthesia.

A practical method of breath-by-breath monitoring of metabolic gas exchange has been developed by GE Healthcare/Datex Ohmeda and incorporated into existing anaesthetic and critical care monitoring systems (M-COVXO). This device relates flow measurements made at the mouth by pneumotachograph to measurements of inspired and expired gas composition by matching the two waveforms thereby allowing continuous, breath-by-breath monitoring of an intubated patient's oxygen uptake and carbon dioxide production. Given that there is a paucity of data comparing this new device against methods more widely used clinically, we tested the device on 11 patients undergoing cardiopulmonary bypass surgery. Using a standard anaesthetic machine (Datex Ohmeda Excel 210 SE) with a semi-closed circle absorber system, oxygen uptake was measured at the mouth continuously throughout the operation at approximately six-second intervals. The data were compared against the reverse Fick method and against standard indirect calorimetry using the Haldane transformation. When compared to the calculated reverse Fick oxygen uptake, a mean difference of +16.5% was found pre-bypass and +9.9% post-bypass, consistent with uptake of oxygen by lung tissue, which is not taken into account by the reverse Fick method. Measurements made comparing the M-COVX metabolic monitor against standard Haldane showed a mean difference of +5.1% pre-bypass and -2.1% post-bypass. Given the ease with which this device can be incorporated into existing anaesthetic monitoring systems and its accuracy in measuring oxygen uptake, the M-COTVX module is an attractive addition to existing perioperative monitoring.

Persisting concentrating and second gas effects on oxygenation during N2O anaesthesia.

Theoretical modelling predicts that the concentrating effect of nitrous oxide (N2O) uptake on alveolar oxygenation is a persisting phenomenon at typical levels of ventilation - perfusion (V/Q) inhomogeneity under anaesthesia. We sought clinical confirmation of this in 20 anaesthetised patients. Arterial oxygen pressure (P(aO2)) was measured after a minimum of 30 min of relaxant general anaesthesia with an inspired oxygen (F(I O2)) of 30%. Patients were randomly allocated to two groups. The intervention group had N2O introduced following baseline blood gas measurements, and the control group continued breathing an identical F(I O2) in nitrogen (N2). The primary outcome variable was change in P(aO2). Mean (SD) in P(aO2) was increased by 1.80 (1.80) kPa after receiving a mean of 47.5 min of N2O compared with baseline conditions breathing O2/N2 (p = 0.01). This change was significantly greater (p = 0.03) than that in the control group: + 0.09 (1.37) kPa, p = 0.83 and confirms the presence of significant persisting concentrating and second gas effects.

Measured pulmonary oxygen consumption: difference between systemic oxygen uptake measured by the reverse Fick method and indirect calorimetry in cardiac surgery.

Measurement of oxygen uptake by indirect calorimetry was compared with the reverse Fick method in a series of patients undergoing cardiac surgery. Oxygen uptake measurements for indirect calorimetry were made using a calibrated measurement system utilizing the Haldane transformation in a simple semiclosed breathing system based upon a modified Bain circuit. Pulmonary blood flow for the reverse Fick method was measured using bolus thermodilution. The results were (mean [standard deviation]): indirect calorimetry 167[26] ml.min(-1), and reverse Fick 148[27] ml.min(-1). Indirect calorimetry overestimated the reverse Fick value by 11.3% (p < 0.001). These results are consistent with the findings of previous studies in similar patient groups and are explained by lung tissue oxygen consumption.

Characteristics of posthospitalization recovery following hysterectomy.

A study to determine the characteristics of posthospitalization recovery after hysterectomy was designed and implemented. Explicit consideration was given to women's feelings of sexuality and the fears and myths which precede and follow the surgery. Retrospective and current self-report data on four major areas were obtained: a) physical changes, b) emotional changes, c) changes in sexuality, and d) fears or beliefs. The results identify some common posthysterectomy physical and emotional experiences. The data challenge the belief that hysterectomy is usually a blow to a woman's concept of self and indicate that most women do not harbor unrealistic fears of physical, emotional, and sexual sequelae. The study findings have implications for nursing care of hysterectomy patients.

Mapping the active sites of 3-phosphoglycerate kinase and glycerol kinase with monoammine chromium(III) ATP.

The 12 isomers of monoammine chromium(III) ATP have been used to probe the ATP binding sites of yeast 3-phosphoglycerate kinase and glycerol kinase from Candida mycoderma. Inhibition studies of 3-phosphoglycerate kinase show a dramatic decrease in isomer binding only when the ammonia is in the Delta axial facial anti position. This suggests an open site architecture with only one strong contact point between the coordination sphere and the enzyme surface. These results agree well with the computer modeling studies of bidentate chromium ATP into the nucleotide site determined by X-ray crystallography [McPhillips, T., et al. (1996) Biochemistry 35, 4118-4127]. Both methods describe an open site strongly supporting the validity of the inhibition studies. Inhibition studies of glycerol kinase show significant decreases in binding for all the tested ammonia positions, suggesting a closed site architecture with many contacts between the coordination sphere and the surface of the enzyme. This is in good agreement with X-ray studies [Hurley, T., et al. (1993) Science 259, 673-677] on the Escherichia coli glycerol kinase. Inhibition studies of hexokinase previously reported [Rawlings, J., et al. (1993) Biochemistry 32, 11204-11210] more closely resemble those of 3-phosphoglycerate kinase, suggesting the surprising result that however closely hexokinase and glycerol kinase are related structurally the site around the coordination sphere in hexokinase is functionally open like that of 3-phosphoglycerate kinase.

Endotracheal intubation following thyroidectomy.

Thirty-five patients requiring tracheostomy or endotracheal intubation, following thyroidectomy are reviewed. Conditions included 30 patients with multinodular goitre, three patients with Graves's disease and two patients with carcinoma of the thyroid. Early in the series, emergency tracheostomy was performed in three patients with airway obstruction following thyroidectomy. Ten patients were deemed at extremely high risk of developing airway obstruction and underwent prophylactic tracheostomy. Endotracheal intubation has been used in preference to tracheostomy in the latter part of the series. Emergency endoctracheal intubation was performed on one patient and prophylactic intubation was carried out in 20 patients. The morbidity and length of hospital stay in this latter group was considerably less than those requiring tracheostomy. It is concluded that patients with potential airway obstruction following thyroidectomy should have prophylactic endotracheal intubation, in preference to tracheostomy.