Cerebellar Grey Matter Volume in Older Persons Is Associated with Worse Cognitive Functioning.

The cerebellum is increasingly recognised for its role in modulation of cognition, behaviour, and affect. The present study examined the relation between structural cerebellar damage (grey matter volume (GMV), white matter hyperintensities (WMHs), lacunar infarcts (LIs) and microbleeds (MBs)) and measures of cognitive, psychological (i.e. symptoms of depression and apathy) and general daily functioning in a population of community-dwelling older persons with mild cognitive deficits, but without dementia. In 194 participants of the Discontinuation of Antihypertensive Treatment in Elderly People (DANTE) Study Leiden, the association between cerebellar GMV, WMHs, LIs and MBs and measures of cognitive, psychological and general daily functioning was analysed with linear regression analysis, adjusted for age, sex, education and cerebral volume. Cerebellar GMV was associated with the overall cognition score (standardised beta 0.20 [95% CI, 0.06-0.33]). Specifically, posterior cerebellar GMV was associated with executive function (standardised beta 0.18 [95% CI, 0.03-0.16]). No relation was found between vascular pathology and cognition. Also, no consistent associations were found on the cerebellar GMV and vascular pathology measures and psychological and general daily functioning. In this population of community-dwelling elderly, less posterior cerebellar GMV but not vascular pathology was associated with worse cognitive function, specifically with poorer executive function. No relation was found between cerebellar pathology and psychological and general daily functioning.

Development of a haptic feedback device to reduce syringe substitution and drug overdosage error.

Despite use of colour-coded labels, syringe substitution (syringe swap) error of anaesthetic drugs remains a frequent and potentially serious cause of iatrogenic harm. We explored the novel concept of using a simple device which can be fitted to existing syringes, and employs colour and raised elements (detents) to provide visual, haptic and auditory cues to supplement the visual cues provided by standard drug labelling, and particularly helps to differentiate, for example, syringes containing vaso-active drugs from other syringes. We produced six different embodiments of the device, and performed a randomised unblinded study with 14 volunteers to identify the functional characteristics which met with the approval of the majority of participants, and the mechanical characteristics which produced adequate haptic feedback without excessive resistance to injection. The optimal design was identified, which required the user to exert a mean (SD) force of ~20 (7) N to overcome the resistance of the detents in the syringe. The majority of volunteers felt that a device of this type would be helpful in reducing the incidence of syringe substitution error; however, further research is needed to assess the efficacy of this innovation in the clinical environment.

A study of temperature control in different designs of emergency drug transport bags.

We investigated whether low melting point phase-change waxes could be incorporated into emergency drug transport bags to attenuate the known temperature extremes their contents can be exposed to. We exposed two custom-made hollow-walled drug containers placed within a pair of drug transport bags to three day/night cycles including periods of direct radiant sunlight. The wall cavities of one contained air, whereas those of the other contained a paraffin wax (melting point of 44-46 °C) with a high latent heat of fusion (until fully melted, its temperature does not increase further). We collected 25,920 temperature datasets at six locations. We found that 97.8% and 84.7% of ampoule temperatures within the wax and air cavity containers, respectively, were within a target range of 15-40 °C over the study duration (Levene statistic W = 4279.1; Levene's test for equality of variance, p < 0.001). Ampoule temperatures in the wax cavity container only exceeded 40 °C for 1.7% of the time. Even when they did so, their temperature was attenuated to 40.3 °C, despite an ambient air temperature of > 40 °C for 6.4% of the time (peak 46.9 °C) and a bag surface temperature of > 40 °C for 17.2% of the time (peak 64.4 °C). In contrast, the ampoule temperature in the air cavity container exceeded 40 °C for 17.1% of the time (peak 54.1 °C). The latent heat of fusion of phase-change materials may be exploited in the design of drug transport bags to mitigate any temperature changes in the drugs stored within them.

Changes in hardness and resilience of i-gelTM cuffs with temperature: a benchtop study.

The i-gelTM is a supraglottic airway with a gel-like thermoplastic cuff. It has been suggested that the seal around the larynx improves following insertion. Perhaps the most intuitive hypothesis proposed for this is that cuff softening occurs during warming from ambient to body temperature. We investigated this using a food industry texture analyser over a wide temperature range. Size 2 and 3 i-gels were secured to a platform within a temperature-controlled water bath, which was in turn mounted on a texture analyser test stand. Both water and i-gel cuff temperatures were recorded. A spherical probe was advanced 4 mm into the surface of each i-gel at a rate of 1 mm.s-1 , then retracted at the same rate while the upward pressure on the probe was recorded. Three runs made at each of the 11 temperatures (10 °C to 60 °C, 5 °C increments) gave 105,864 data points, from which values for hardness (the peak force on the probe at maximum indentation), and resilience (the rate at which the material recovers its original shape) were calculated. Over 10 to 60 °C, the smallest hardness value expressed as a proportion of the largest was 88.2% and 89.8% for size 2 and 3 i-gels, respectively, and for resilience these were 92.8% and 86.2%, respectively. Over room temperature to body temperature range (21-37.4 °C), hardness decreased by 3.15% and increased by 0.47% for i-gel sizes 2 and 3, respectively, whereas resilience values decreased by 1.85% and 2.68%, respectively. Cuff hardness and resilience did generally reduce with warming, but the effect was minimal over temperature ranges that may be encountered during clinical use.

Influence of Small Vessel Disease and Microstructural Integrity on Neurocognitive Functioning in Older Individuals: The DANTE Study Leiden.

BACKGROUND AND PURPOSE: Small vessel disease is a major cause of neurocognitive dysfunction in the elderly. Small vessel disease may manifest as white matter hyperintensities, lacunar infarcts, cerebral microbleeds, and atrophy, all of which are visible on conventional MR imaging or as microstructural changes determined by diffusion tensor imaging. This study investigated whether microstructural integrity is associated with neurocognitive dysfunction in older individuals, irrespective of the conventional features of small vessel disease. MATERIALS AND METHODS: The study included 195 participants (75 years of age or older) who underwent conventional 3T MR imaging with DTI to assess fractional anisotropy, mean diffusivity, axial diffusivity, and radial diffusivity. Cognitive tests were administered to assess cognitive domains, and the Geriatric Depression Scale-15 and Apathy Scale of Starkstein were used to assess symptoms of depression and apathy, respectively. The association between DTI measures and neurocognitive function was analyzed by using linear regression models. RESULTS: In gray matter, a lower fractional anisotropy and higher mean diffusivity, axial diffusivity, and radial diffusivity were associated with worse executive function, psychomotor speed, and overall cognition and, in white matter, also with memory. Findings were independent of white matter hyperintensities, lacunar infarcts, and cerebral microbleeds. However, after additional adjustment for normalized brain volume, only lower fractional anisotropy in white and gray matter and higher gray matter radial diffusivity remained associated with executive functioning. DTI measures were not associated with scores on the Geriatric Depression Scale-15 or the Apathy Scale of Starkstein. CONCLUSIONS: Microstructural integrity was associated with cognitive but not psychological dysfunction. Associations were independent of the conventional features of small vessel disease but attenuated after adjusting for brain volume.

The development and evaluation of a non-pressurised, chemical oxygen reaction generation vessel and breathing system providing emergency oxygen for an extended duration.

The objective was to develop a sodium percarbonate/water/catalyst chemical oxygen generator that did not require compressed gas. Existing devices utilising this reaction have a very short duration of action. Preliminary experiments with a glass reaction vessel, water bath and electronic flowmeter indicated that many factors affected oxygen production rate including reagent formulation, temperature, water volume and agitation frequency. Having undertaken full-scale experiments using a stainless steel vessel, an optimum combination of reagents was found to be 1 litre water, 0.75 g manganese dioxide catalyst, 60 g sodium percarbonate granules and 800 g of custom pressed 7.21 (0.28) g sodium percarbonate tablets. This combination of granules and slower dissolution tablets produced a rapid initial oxygen flow to 'purge' an attached low-flow breathing system allowing immediate use, followed by a constant flow meeting metabolic requirements for a minimum of 1 h duration.

Electroanaesthesia--from torpedo fish to TENS.

In 153 AD, the Roman physician Scribonius Largus identified that electric current had analgesic properties, instructing patients to stand on an electric ray for the treatment of gout. In 2014, transcranial magnetic stimulation was approved by the National Institute for Health and Care Excellence for the treatment of migraine. Although separated by nearly two millennia, these milestones represent the evolution of the utilisation of electric current in medical and anaesthetic practice. Significant advances have been made over the last century in particular, and during the 1960s and 1970s, tens of thousands of patients were reportedly anaesthetised for surgical interventions using electric current as the anaesthetic agent. Many medical interventions, including transcutaneous electrical nerve stimulation and deep brain stimulation, have evolved in the aftermath of investigations into electroanaesthesia; the potential for electric current to be an anaesthetic agent of the future still exists.

Utility of a low-cost wireless force platform as a potential clinical test of balance recovery after neuraxial anaesthesia.

INTRODUCTION: Recovery of balance after neuraxial anaesthesia can remain delayed after simple clinical tests have demonstrated motor recovery. Dynamic posturography tracks the small movements or sway of a person standing as still as possible on a force platform and has been investigated as an objective measure of the ability to walk following anaesthesia. These are expensive laboratory devices, limiting their clinical utility. One measured variable is path length, the cumulative distance travelled in the horizontal plane by the centre of pressure of a person standing on the platform over 1min. Path length might potentially be measured using the Nintendo® Wii-Fit Balance Board™. METHODS: The feasibility of intercepting raw wireless data from a Wii-Fit Balance Board™ using custom software to calculate path length was explored. Subsequently, path lengths were measured using both this and a laboratory platform simultaneously. In a random order 20 volunteers (a) stood for 1min, feet together, eyes open (conventional baseline test); and (b) stood for 1min, feet together, eyes closed (simulating residual anaesthesia with increased sway). For each device, the ratio b:a was calculated as an index of performance reduction when eyes were closed. RESULTS: Path lengths ranged from 58.5 to 243cm, mean bias 9cm (Wii-Fitlaboratory platform) and 95% confidence limits of 0.04 to -0.13. CONCLUSIONS: The path lengths were in close agreement and the Wii-Fit Balance Board™ may be worthy of further investigation as a tool to objectively assess readiness to ambulate following neuraxial anaesthesia.

Utility of optical facial feature and arm movement tracking systems to enable text communication in critically ill patients who cannot otherwise communicate.

PURPOSE: Patients recovering from critical illness especially those with critical illness related neuropathy, myopathy, or burns to face, arms and hands are often unable to communicate by writing, speech (due to tracheostomy) or lip reading. This may frustrate both patient and staff. Two low cost movement tracking systems based around a laptop webcam and a laser/optical gaming system sensor were utilised as control inputs for on-screen text creation software and both were evaluated as communication tools in volunteers. METHODS: Two methods were used to control an on-screen cursor to create short sentences via an on-screen keyboard: (i) webcam-based facial feature tracking, (ii) arm movement tracking by laser/camera gaming sensor and modified software. 16 volunteers with simulated tracheostomy and bandaged arms to simulate communication via gross movements of a burned limb, communicated 3 standard messages using each system (total 48 per system) in random sequence. RESULTS: Ten and 13 minor typographical errors occurred with each system respectively, however all messages were comprehensible. Speed of sentence formation ranged from 58 to 120s with the facial feature tracking system, and 60-160s with the arm movement tracking system. The average speed of sentence formation was 81s (range 58-120) and 104s (range 60-160) for facial feature and arm tracking systems respectively, (P<0.001, 2-tailed independent sample t-test). CONCLUSION: Both devices may be potentially useful communication aids in patients in general and burns critical care units who cannot communicate by conventional means, due to the nature of their injuries.

Minimum alveolar concentration (MAC) for sevoflurane and xenon at normothermia and hypothermia in newborn pigs.

BACKGROUND: Neuroprotection from therapeutic hypothermia increases when combined with the anaesthetic gas xenon in animal studies. A clinical feasibility study of the combined treatment has been successfully undertaken in asphyxiated human term newborns. It is unknown whether xenon alone would be sufficient for sedation during hypothermia eliminating or reducing the need for other sedative or analgesic infusions in ventilated sick infants. Minimum alveolar concentration (MAC) of xenon is unknown in any neonatal species. METHODS: Eight newborn pigs were anaesthetised with sevoflurane alone and then sevoflurane plus xenon at two temperatures. Pigs were randomised to start at either 38.5°C or 33.5°C. MAC for sevoflurane was determined using the claw clamp technique at the preset body temperature. For xenon MAC determination, a background of 0.5 MAC sevoflurane was used, and 60% xenon added to the gas mixture. The relationship between sevoflurane and xenon MAC is assumed to be additive. Xenon concentrations were changed in 5% steps until a positive clamp reaction was noted. Pigs' temperature was changed to the second target, and two MAC determinations for sevoflurane and 0.5 MAC sevoflurane plus xenon were repeated. RESULTS: MAC for sevoflurane was 4.1% [95% confidence interval (CI): 3.65-4.50] at 38.5°C and 3.05% (CI: 2.63-3.48) at 33.5°C, a significant reduction. MAC for xenon was 120% at 38.5°C and 116% at 33.5°C, not different. CONCLUSION: In newborn swine sevoflurane, MAC was temperature dependent, while xenon MAC was independent of temperature. There was large individual variability in xenon MAC, from 60% to 120%.

Contamination of laryngoscope handles.

Despite use of sterile or disposable laryngoscope blades for each patient, disinfection of laryngoscope handles does not routinely occur, and these devices present a potential route of transmission of pathogens between patients and staff. A total of 192 specimens from 64 laryngoscope handles deemed 'ready for patient use' in the anaesthetic rooms of 32 operating theatres were semiquantitatively assessed for bacterial contamination. A further 116 specimens from 58 of the handles were tested for occult blood contamination. One or more species of bacteria were isolated from 55 (86%) of the handles, and included organisms such as enterococci, meticillin-susceptible Staphylococcus aureus, Klebsiella and acinetobacter. Cultures did not yield any anaerobes, fungi, meticillin-resistant Staphylococcus aureus, vancomycin-resistant enterococci or multiply-resistant Gram-negative bacilli. No occult blood contamination was demonstrated. Although the majority of organisms isolated were not pathogenic, their presence indicates the potential for transmission of pathogens from laryngoscope handles. Strategies to address contamination of handles include revision of procedures for disinfection and storage prior to use, introduction of disposable handles or sheaths, and re-design of handles to eliminate knurled surfaces and contact points.

A low oxygen consumption pneumatic ventilator for emergency construction during a respiratory failure pandemic.

The UK influenza pandemic plan predicts up to 750,000 additional deaths with hospitals prioritising patients against inadequate resources. We investigated three prototype low-cost, gas-efficient, pneumatic ventilators in a test lung model at different compliance and rate settings. Mean (SD) oxygen consumption was 0.913 (0.198) and 1.119 (0.267) l.min(-1) at tidal volumes of 500 ml and 700 ml respectively. Values of F(I)o(2) increased marginally as lung compliance reduced, reflecting the increased ventilator workload and consequent increased enrichment of breathing gas by waste oxygen from the pneumatic mechanism. We also demonstrated that a stable nitric oxide concentration could be delivered by this design following volumetric principles. It is possible to make a gas-efficient ventilator costing less than 200 pounds from industrial components for use where oxygen is available at 2-4 bar, with no pressurised air or electrical requirements. Such a device could be mass-produced for crises characterised by an overwhelming demand for mechanical ventilation and a limited oxygen supply.

Xenon measurement in breathing systems: a comparison of ultrasonic and thermal conductivity methods.

Xenon is an anaesthetic and possibly neuroprotective gas that is impossible to measure using conventional anaesthetic gas analysers. We compared the performance of two commissioned xenon analysers using ultrasonic and thermal conductivity principles against a reference method of laser refractometry. An experimental gas circuit was constructed and xenon concentrations compared over a range of 0-100% in oxygen. Eighty-two paired measurements were made comparing the experimental methods with laser refractometry. The ultrasonic method displayed good agreement with laser refractometry, with a mean difference of - 0.74% and two standard deviation limits of agreement of + 1.08% to - 2.56%. The agreement between laser refractometry and thermal conductivity was poor, the mean difference being - 5.37%, with two standard deviation limits of agreement of + 0.6% to - 11.3%. The ultrasonic method for measuring xenon concentrations can be used in breathing circuits. The thermal conductivity instrument may need further development.

Effect of catheter design on tracheal pressures during tracheal gas insufflation.

BACKGROUND AND OBJECTIVE: This study investigated the distribution of pressures within a model trachea, produced by five different tracheal gas insufflation devices. The aim was to suggest a suitable design of a tracheal gas insufflation device for clinical use. METHODS: Each device was tested using insufflation flow rates of 5 and 10 L min(-1). For each flow rate, the pressure within the tracheal model was measured at 33 fixed points. RESULTS: The Boussignac tracheal tube produced the most even pressure distribution, while a reverse-flow catheter produced pressure changes of the smallest magnitude. CONCLUSIONS: We suggest that catheters producing the lowest pressure changes are likely to be safer for clinical use.

Exploration of xenon as a potential cardiostable sedative: a comparison with propofol after cardiac surgery.

Xenon anaesthesia is thought to have minimal haemodynamic side-effects. It is, however, expensive and requires special delivery systems for economic use. In this randomised cross-over study, we: (i) investigated the haemodynamic profile and recovery characteristics of xenon compared with propofol sedation in postoperative cardiac surgery patients, and (ii) evaluated a fully closed breathing system to minimise xenon consumption. We demonstrated a significantly faster recovery from xenon (3 min 11 s) than propofol sedation (25 min 23 s). Relative to propofol, xenon sedation produced no change in heart rate or mean arterial pressure and there were significantly higher mean values for central venous pressure (10.6 vs. 8.9 mmHg), pulmonary artery occlusion pressure (11.2 vs. 9.5 mmHg), mean pulmonary artery pressure (20.1 vs. 18.3 mmHg) and systemic vascular resistance index (2170 vs. 1896 dyn.s.cm-5.m-2). The haemodynamic profile seen with propofol reflected its known vasodilator effects. This was supported by the almost identical left ventricular stroke work indexes seen with both methods of sedation.

Tracheal gas insufflation apparatus. Performance of a novel phase-specific device.

Tracheal gas insufflation is a technique in which gas is injected intratracheally during positive pressure ventilation. The fresh gas rinses expired gas from the tracheal tube and anatomical dead space, aiding carbon dioxide elimination. This reduces ventilatory volume and pressure, helping to reduce ventilator-induced lung damage. Complications of tracheal gas insufflation include interference with ventilator function, tracheal damage and barotrauma. Expiratory washout is a variation of tracheal gas insufflation. We designed and constructed an original expiratory washout system and evaluated its safety and performance in lung and animal models. We found that expiratory limb and tracheal tube occlusion tests caused the device to disable itself at acceptable intratracheal pressures. We also demonstrated up to 31% reduction in tidal volume compared with conventional ventilation, supporting the possibility of using this device clinically to lessen volutrauma. We concluded that aspects of this design might alleviate many of the safety concerns of using tracheal gas insufflation.