J.G. Hardman

Levobupivacaine‐induced seizures and cardiovascular collapse treated with Intralipid®

Summary Lipid emulsion has been used in the successful treatment of local anaesthetic‐induced cardiovascular collapse in animals and in two cases of cardiac arrest in humans. Previous reports of levobupivacaine toxicity in humans have been characterised by neurological signs and symptoms, without serious cardiovascular events. We present a case in which presumed intravenous injection of levobupivacaine led to neurological and cardiovascular consequences. This was treated successfully by resuscitation that included intravenous Intralipid® infusion.

Pitfalls of ultrasound guided vascular access: the use of three/four‐dimensional ultrasound

The use of ultrasound guidance for central venous access is widespread and was recommended as the technique of choice by The National Institute of Clinical Excellence in the UK in 2002. However, complications have been reported using this technique. In this article we review the technique of two‐dimensional ultrasound needle guidance and the errors that can occur. We then discuss the development of three‐ and four‐dimensional ultrasound and describe our experiences using this imaging modality in simulated and actual needle‐guidance. We discuss the potential advantages for clinicians utilising this newer form of ultrasound imaging for central venous access.

Factors determining the onset and course of hypoxemia during apnea: an investigation using physiological modelling.

We used the Nottingham Physiology Simulator to examine the onset and course of hypoxemia during apnea after pulmonary denitrogenation. The following factors, as possible determinants of the hypoxemia profile, were varied to examine their effect: functional residual capacity, oxygen consumption, respiratory quotient, hemoglobin concentration, ventilatory minute volume, duration of denitrogenation, pulmonary venous admixture, and state of the airway (closed versus open). Airway obstruction significantly reduced the time to 50% oxyhemoglobin saturation (8 vs 11 min). Provision of 100% oxygen rather than air to the open, apneic patient model greatly prolonged time to 50% oxyhemoglobin saturation (66 vs 11 min). Hemoglobin concentration, venous admixture, and respiratory quotient had small, insignificant effects on the time to desaturation. Reduced functional residual capacity, short duration of denitrogenation, hypoventilation, and increased oxygen consumption significantly shortened the time to 50% oxyhemoglobin saturation during apnea. Implications: Reduction in oxygen levels during cessation of breathing is dangerous and common in anesthetic practice. We used validated, mathematical, physiological models to reveal the impact of physiological factors on the deterioration of oxygen levels. This study could not be performed on patients and reveals important information.

Cerebral hemodynamic response to the introduction of desflurane: A comparison with sevoflurane.

Rapid increases in the inspired concentration of desflurane cause transient increases in heart rate and blood pressure. Desflurane also impairs cerebral autoregulation at clinical concentrations. Sevoflurane does not share these hemodynamic side effects. We compared the cerebral and systemic hemodynamic responses to the introduction of desflurane or sevoflurane after the induction of anesthesia with propofol. Twenty healthy adult patients scheduled for nonneurological surgery were recruited. After the induction of anesthesia with propofol, either desflurane or sevoflurane (n = 10 per group) was introduced at 7.2% or 2.2%, respectively, and increased to 10.8% or 3.3%, respectively, 2 min later. Middle cerebral artery blood flow velocity was measured continuously by using a 2-MHz transcranial Doppler ultrasound probe. Heart rate and blood pressure were recorded at 1-min intervals during the 12-min study period. Those patients receiving desflurane had significantly greater middle cerebral artery blood flow velocities, heart rates, and blood pressures than those receiving sevoflurane (P < 0.01). Implications The introduction of desflurane after the induction of anesthesia leads to significant disturbances in cerebral and systemic hemodynamics suggesting loss of cerebral autoregulation and cerebral hyperemia. This may have implications for patients undergoing anesthesia for intracranial surgery.

Pre-oxygenation and apnoea in pregnancy : changes during labour and with obstetric morbidity in a computational simulation

Using the Nottingham Physiology Simulator, we investigated the effects on pre‐oxygenation and apnoea during rapid sequence induction of labour, obesity, sepsis, pre‐eclampsia, maternal haemorrhage and multiple pregnancy in term pregnancy. Pre‐oxygenation with 100% oxygen was followed by simulated rapid sequence induction when end‐tidal nitrogen tension was less than 1 kPa, and apnoea. Labour, morbid obesity and sepsis accelerated pre‐oxygenation and de‐oxygenation during apnoea. Fastest pre‐oxygenation was in labour, with 95% of the maximum change in expired oxygen tension occurring in 47 s, compared to 97 s in a standard pregnant subject. The labouring subject with a body mass index of 50 kg.m−2 demonstrated the fastest desaturation, the time taken to fall to an arterial saturation < 90% being 98 s, compared to 292 s in a standard pregnant subject. Pre‐eclampsia prolonged pre‐oxygenation and tolerance to apnoea. Maternal haemorrhage and multiple pregnancy had minor effects. Our results inform the risk‐benefit comparison of the anaesthetic options for Caesarean section.

Three-Dimensional, Multiplanar, Ultrasound-Guided, Radial Nerve Block

Objective: We describe the use of 3-dimensional, multiplanar ultrasound imaging for peripheral nerve block. Case Report: To illustrate the potential usefulness of the technique, we present a case in which real-time 3-dimensional, multiplanar ultrasound was used to assist in the performance of a radial nerve block. Conclusions: Three-dimensional, multiplanar ultrasound in real-time has the potential to improve nerve identification and accuracy of needle placement in regional anesthesia.

Hypoxaemia during open‐airway apnoea: a computational modelling analysis

Hypoxaemia during open‐airway apnoea, e.g. during brainstem death testing, may cause organ damage. The effect of ambient oxygen fraction on the extent of hypoxaemia has not been established. We validated the Nottingham Physiology Simulator in this context by reproducing the methodologies and results of four published clinical studies. We then used the simulator to examine the effects of different ambient oxygen fractions (0.21–1.0) and shunt fractions (1–30% of cardiac output) during apnoea. Increasing ambient oxygen fraction from 0.9 to 1.0 more than doubled the time to haemoglobin desaturation at all shunt fractions, and extended apnoea longer than when the ambient oxygen fraction was increased from 0.21 to 0.9. When ambient oxygen fraction and shunt fraction were large, arterial oxygen tension transiently increased during apnoea. A very high ambient oxygen fraction and a patent airway are likely to delay dangerous hypoxaemia during apnoea.

Bibliometrics of anaesthesia researchers in the UK

BACKGROUND Bibliometrics provide surrogate measures of the quality and quantity of research undertaken by departments and individuals. Previous reports have suggested that academic anaesthesia research in the UK is in decline. We wished to provide a comprehensive description of current and historical published output of UK anaesthesia researchers. METHODS Bibliometric indices (Web of Science(®)) were calculated for anaesthesia researchers in the UK for the whole period covered by the database, and for 2004-8. A parallel search was made using the Scholarometer™ tool, which parses output from Google Scholar™. Calculated indices included total number of publications; total number of citations; citations per paper; h-index; g-index; and modified impact index. RESULTS One hundred and four individuals and 23 academic departments were identified. Median values (inter-quartile range) for the indices were: total papers 57 (24-95) (individuals for the whole period), 11 (6-20) (individuals 2004-8), 50 (30-70) (departments 2004-8); total number of citations 571 (175-1328), 93 (38-207), 383 (239-845); h-index 13 (8-20), 6 (3-8), 11 (9-14). Four departments were ranked in the top 5 for all indices. CONCLUSIONS The general distribution of bibliometric data is similar to that seen in other specialities in Europe and North America. Four departments contribute to more than 50% of published anaesthesia research output in this data set. These data provide useful comparative tools for individuals, departments, and national bodies.

Real-time Three-dimensional Ultrasound-guided Central Venous Catheter Placement

We present the first description of real-time 3-dimensional ultrasound for insertion of a central venous catheter in a surgical patient. An HD11 XE™ ultrasound machine with a V8-4 transducer (Philips Medical Systems, Bothell, WA) was used throughout. Three-dimensional multiplanar and volume-rendered views allowed us to simultaneously view the neck anatomy in 3 orthogonal planes. Needle entry into the vein and subsequent catheter placement were also visualized. We were able to rotate the views in real time, thereby enabling visualization of the catheter within the lumen of the vein. The ability to see simultaneous real-time short- and long-axis views along with volume perspective without altering transducer position is an exciting development with the potential to confer a safety benefit to the patient. Although the operator is required to assimilate more information, the limitations we encountered were mainly related to processing power and transducer size, which we expect will be overcome with advancing technology.

Responsiveness of the EQ-5D health-related quality-of-life instrument in assessing low back pain.

OBJECTIVE To compare the responsiveness of the EuroQol five-dimensional questionnaire (EQ-5D) generic quality-of-life instrument with that of specific instruments-the Brief Pain Inventory (BPI) and the Oswestry Disability Index (ODI)-in assessing low back pain. METHODS Data were obtained from a group of patients receiving epidural steroid injections. We assessed responsiveness by using correlation, by estimating standardized response means, by receiver operating characteristic curve analysis, and by comparing the minimum clinically important differences peculiar to each of the instruments. RESULTS ODI, BPI, and EQ-5D index scores, and changes in scores, were found to be correlated. Estimated standardized response means and receiver operating characteristic curve analysis suggested lower responsiveness for the EQ-5D index score. Clinically significant categories of mild, moderate, and severe BPI pain intensity translated into progressively and significantly lower mean EQ-5D index scores. An increase or a decrease in severity level reported on any of the five EQ-5D dimensions was associated with significant changes (with appropriate signs) in the condition-specific scores. No change in severity in any EQ-5D dimension was associated with no change in the specific scores. Significant changes in the EQ-5D index scores were associated with clinically important changes in the ODI and BPI scores. Correlation between index scores and responses on EQ-5Ds visual analogue scale was only moderate. CONCLUSIONS The EQ-5D index is less responsive than instruments specific to pain measurement, although it is capable of indicating clinically important changes. The lower responsiveness arises from EQ-5Ds more limited gradation of severity and its multidimensionality.