Comparison of non-invasive peripheral venous saturations with venous blood co-oximetry.

The estimation of venous oxygen saturations using photoplethysmography (PPG) may be useful as a noninvasive continuous method of detecting changes in regional oxygen supply and demand (e.g. in the splanchnic circulation). The aim of this research was to compare PPG-derived peripheral venous oxygen saturations directly with venous saturation measured from co-oximetry blood samples, to assess the feasibility of non-invasive local venous oxygen saturation. This paper comprises two similar studies: one in healthy spontaneously-breathing volunteers and one in mechanically ventilated anaesthetised patients. In both studies, PPG-derived estimates of peripheral venous oxygen saturations (SxvO2) were compared with co-oximetry samples (ScovO2) of venous blood from the dorsum of the hand. The results were analysed and correlation between the PPG-derived results and co-oximetry was tested for. In the volunteer subjects,moderate correlation (r = 0.81) was seen between SxvO2 values and co-oximetry derived venous saturations (ScovO2), with a mean (±SD) difference of +5.65 ± 14.3% observed between the two methods. In the anaesthetised patients SxvO2 values were only 3.81% lower than SpO2 and tended to underestimate venous saturation (mean difference = -2.67 ± 5.89%) while correlating weakly with ScovO2 (r = 0.10). The results suggest that significant refinement of the technique is needed to sufficiently improve accuracy to produce clinically meaningful measurement of peripheral venous oxygen saturation. In anaesthetised patients the use of the technique may be severely limited by cutaneous arteriovenous shunting.

Prevalence of chronic pain in the UK: a systematic review and meta-analysis of population studies.

OBJECTIVES: There is little consensus regarding the burden of pain in the UK. The purpose of this review was to synthesise existing data on the prevalence of various chronic pain phenotypes in order to produce accurate and contemporary national estimates. DESIGN: Major electronic databases were searched for articles published after 1990, reporting population-based prevalence estimates of chronic pain (pain lasting >3 months), chronic widespread pain, fibromyalgia and chronic neuropathic pain. Pooled prevalence estimates were calculated for chronic pain and chronic widespread pain. RESULTS: Of the 1737 articles generated through our searches, 19 studies matched our inclusion criteria, presenting data from 139 933 adult residents of the UK. The prevalence of chronic pain, derived from 7 studies, ranged from 35.0% to 51.3% (pooled estimate 43.5%, 95% CIs 38.4% to 48.6%). The prevalence of moderate-severely disabling chronic pain (Von Korff grades III/IV), based on 4 studies, ranged from 10.4% to 14.3%. 12 studies stratified chronic pain prevalence by age group, demonstrating a trend towards increasing prevalence with increasing age from 14.3% in 18-25 years old, to 62% in the over 75 age group, although the prevalence of chronic pain in young people (18-39 years old) may be as high as 30%. Reported prevalence estimates were summarised for chronic widespread pain (pooled estimate 14.2%, 95% CI 12.3% to 16.1%; 5 studies), chronic neuropathic pain (8.2% to 8.9%; 2 studies) and fibromyalgia (5.4%; 1 study). Chronic pain was more common in female than male participants, across all measured phenotypes. CONCLUSIONS: Chronic pain affects between one-third and one-half of the population of the UK, corresponding to just under 28 million adults, based on data from the best available published studies. This figure is likely to increase further in line with an ageing population.

Estimation of instantaneous venous blood saturation using the photoplethysmograph waveform.

Non-invasive estimation of regional venous saturation (SxvO2) using a conventional pulse oximeter could provide a means of obtaining clinically relevant information. This study was carried out in order to investigate the hypothesis that SxvO2 could be estimated by utilising the modulations created by positive pressure ventilation in the photoplethysmograph (PPG) signals. The modulations caused by the mechanical ventilator were extracted from oesophageal PPG signals obtained from 12 patients undergoing cardiothoracic surgery. The signals analysed in this work were acquired in a previous study. For the purpose of this analysis the raw PPG signal was considered to have three major components, ac PPG signal (cardiac related component), a static component or dc PPG signal (created mostly by the absorption of light by surrounding tissue) and the ventilator modulation component. These components were then used to estimate instantaneous arterial blood oxygen saturation (SpO2) and SxvO2 by utilising time-frequency analysis technique of smoothed-pseudo Wigner-Ville distribution (SPWVD). The results showed that there was no significant difference in the traditionally-derived (time-domain) arterial saturation and the instantaneous arterial saturation. However, the instantaneous venous saturation was found to be significantly lower than the estimated time-domain and instantaneous arterial saturation (P = < 0.001, n = 12).

A double-blind, randomized, placebo-controlled, parallel-group study of THC/CBD oromucosal spray in combination with the existing treatment regimen, in the relief of central neuropathic pain in patients with multiple sclerosis.

Central neuropathic pain (CNP) occurs in many multiple sclerosis (MS) patients. The provision of adequate pain relief to these patients can very difficult. Here we report the first phase III placebo-controlled study of the efficacy of the endocannabinoid system modulator delta-9-tetrahydrocannabinol (THC)/cannabidiol (CBD) oromucosal spray (USAN name, nabiximols; Sativex, GW Pharmaceuticals, Salisbury, Wiltshire, UK), to alleviate CNP. Patients who had failed to gain adequate analgesia from existing medication were treated with THC/CBD spray or placebo as an add-on treatment, in a double-blind manner, for 14 weeks to investigate the efficacy of the medication in MS-induced neuropathic pain. This parallel-group phase of the study was then followed by an 18-week randomized-withdrawal study (14-week open-label treatment period plus a double-blind 4-week randomized-withdrawal phase) to investigate time to treatment failure and show maintenance of efficacy. A total of 339 patients were randomized to phase A (167 received THC/CBD spray and 172 received placebo). Of those who completed phase A, 58 entered the randomized-withdrawal phase. The primary endpoint of responder analysis at the 30 % level at week 14 of phase A of the study was not met, with 50 % of patients on THC/CBD spray classed as responders at the 30 % level compared to 45 % of patients on placebo (p = 0.234). However, an interim analysis at week 10 showed a statistically significant treatment difference in favor of THC/CBD spray at this time point (p = 0.046). During the randomized-withdrawal phase, the primary endpoint of time to treatment failure was statistically significant in favor of THC/CBD spray, with 57 % of patients receiving placebo failing treatment versus 24 % of patients from the THC/CBD spray group (p = 0.04). The mean change from baseline in Pain Numerical Rating Scale (NRS) (p = 0.028) and sleep quality NRS (p = 0.015) scores, both secondary endpoints in phase B, were also statistically significant compared to placebo, with estimated treatment differences of -0.79 and 0.99 points, respectively, in favor of THC/CBD spray treatment. The results of the current investigation were equivocal, with conflicting findings in the two phases of the study. While there were a large proportion of responders to THC/CBD spray treatment during the phase A double-blind period, the primary endpoint was not met due to a similarly large number of placebo responders. In contrast, there was a marked effect in phase B of the study, with an increased time to treatment failure in the THC/CBD spray group compared to placebo. These findings suggest that further studies are required to explore the full potential of THC/CBD spray in these patients.

Normalization of widespread hyperesthesia and facilitated spatial summation of deep-tissue pain in knee osteoarthritis patients after knee replacement.

OBJECTIVE: The modest association between radiographic joint damage and pain in osteoarthritis (OA) has led to the suggestion of facilitated central pain processing. This study evaluated the importance of ongoing tissue pathology in the maintenance of enhanced central pain processing. METHODS: Pain assessment was performed on 48 patients with symptomatic knee OA and 21 sex- and age-matched pain-free healthy control subjects. Twenty of the OA patients subsequently underwent total knee replacement surgery and were reassessed. Pressure-pain thresholds (PPTs) were recorded using a pressure algometer (both over and distant from the knee) and a double-chamber inflatable cuff mounted around the calf. Spatial summation was assessed by relating PPTs using the dual- and single-chamber cuff. Conditioned pain modulation (CPM) was assessed by recording the increase in PPT in response to experimental arm pain. RESULTS: PPTs at the knee and at sites away from the knee were reduced in OA patients as compared with healthy pain-free control subjects (P < 0.0001). Cuff PPTs were decreased in OA patients as compared with the healthy controls (P < 0.05), who also exhibited a greater degree of spatial summation (P < 0.05). Whereas an elevation of PPTs was noted in the healthy controls in response to experimental arm pain (P < 0.0001), no such CPM was observed in the OA patients. Following joint replacement in the OA patients, there was a reduction in the widespread mechanical hyperesthesia, along with normalization of spatial summation ratios and restoration of CPM. CONCLUSION: The widespread hyperesthesia and enhanced spatial summation observed in OA patients imply sensitized central pain mechanisms together with the loss of CPM. Normalization of the results following joint replacement implies that these central pain processes are maintained by peripheral input.

Estimation of venous oxygenation saturation using the finger Photoplethysmograph (PPG) waveform.

In this study, finger photoplethysmograph data obtained from twelve patients undergoing cardiothoracic surgery were analyzed in order to estimate the venous saturation utilizing the modulations created by the positive pressure ventilation in the AC Photoplethysmograph (PPG) signals. The PPG signals were analyzed in the time-domain using a conventional pulse oximetry algorithm to produce estimations of arterial oxygen saturation. The instantaneous arterial and venous saturations were estimated by utilizing time-frequency analysis technique of Smoothed-pseudo Wigner-Ville Distribution (SPWVD). The results showed that there was no significant difference in the traditionally-derived (time-domain) arterial saturation and the instantaneous arterial saturation. However, the instantaneous venous saturation was found to be significantly lower than the time-domain estimated and instantaneous arterial saturation (P=<0.001).

Physical and chemical characterization of dentin surface following treatment with NovaMin technology.

OBJECTIVE: The aim of this study was to characterize, in vitro, the mode of action of calcium sodium phosphosilicate (NovaMin) in occluding dentin tubules for the purpose of treating dentin hypersensitivity. METHODS: Calcium sodium phosphosilicate (CSPS) was combined with artificial saliva on surfaces of prepared dentin discs. The layer formed was initially examined by a scanning electron microscope (SEM). Focused ion beam (FIB) milling was used to make bulk cross-sections and thin film lamellae. Low kV scanning transmission electron microscopy (STEM), energy dispersive x-ray spectroscopy (EDS), and selected area electron diffraction were then used to characterize, chemically and structurally, the layer formed and the material occluding the tubules. Experiments were also performed to assess the suitability of using an environmental scanning electron microscope (ESEM) in wet mode to follow the transition from CSPS to hydroxyapatite. RESULTS: SEM imaging showed that a layer was formed on the treated dentin samples, and that this layer occluded tubules. Chemical and structural analysis of this material showed that it was hydroxyapatite-like. The wet mode ESEM experiments demonstrated that this technique has the potential to follow the transition from CSPS to the crystalline hydroxyapatite material. CONCLUSION: The use of modern imaging and analysis techniques has demonstrated, in vitro, the reaction of CSPS from an amorphous material to a crystalline hydroxyapatite-like material. These experiments confirmed an occlusion mode of action for CSPS for the treatment of dentin hypersensitivity.

Physical and chemical characterization of the surface layers formed on dentin following treatment with a fluoridated toothpaste containing NovaMin.

OBJECTIVE: To characterize in vitro the formation and robustness of a layer formed on dentin following treatment with a fluoridated toothpaste containing calcium sodium phosphosilicate (NovaMin) using modem imaging and analysis techniques. METHODS: Calcium sodium phosphosilicate (CSPS)-containing toothpaste was brushed on to etched dentin specimens twice daily for up to five days. In between applications the samples were stored in artificial saliva. Additionally, certain samples underwent a chemical challenge in the form of a dietary acid, whereby samples were exposed to a cola or grapefruit juice beverage for five minutes on day 4 of the five-day study. The ability of the CSPS-containing formulation to occlude tubules was assessed visually by scanning electron microscope (SEM) imaging and compared to a water control. In a second experiment, the mechanical resistance of the layer was assessed using profilometry after controlled brushing for 200 brush strokes with a wet medium-bristled toothbrush. To visualize the layer and characterize the tubule occlusion, longitudinal cross-sections were prepared using a focused ion beam scanning electron microscope (FIB SEM), and analysis performed by energy dispersive x-ray spectroscopy (EDS) and electron diffraction. Owing to the complexity of the mixed material deposited after application of the toothpaste, material from inside a dentin tubule was selectively removed after five days of treatment, and the morphologically different materials imaged and analyzed by electron diffraction in the transmission electron microscope (TEM). RESULTS: SEM inspection showed significant coverage of the dentin samples after application of CSPS toothpaste for all five days, in contrast to the water control where the majority of tubules remained open after all five days. Exposure of the NovaMin-treated samples to common dietary acids did not lead to re-exposure of the tubules. Profilometry measurements demonstrated an intact layer covering the dentin surface after one and five days. EDS analysis and electron diffraction indicated the layer and the material plugging the tubule to be a calcium phosphate material with a crystallographic structure similar to hydroxyapatite. CONCLUSION: CSPS contained in toothpaste formulations adhered to exposed dentin surfaces. The layer formed was resistant to acid and mechanical challenges. Characterization of this layer indicated it was hydroxyapatite-like in nature.

Investigation of photoplethysmographic signals and blood oxygen saturation values obtained from human splanchnic organs using a fiber optic sensor.

OBJECTIVE: A reliable, continuous method of monitoring splanchnic organ oxygen saturation could allow for the early detection of malperfusion, and may prevent the onset of multiple organ failure. Current monitoring techniques have not been widely accepted in critical care monitoring. As a preliminary to developing a continuous indwelling device, this study evaluates a new handheld fiber optic photoplethysmographic (PPG) sensor for estimating the blood oxygen saturation (SpO(2)) of splanchnic organs during surgery. METHODS: A fiber optic splanchnic PPG sensor, instrumentation system and virtual instrument were developed to facilitate PPG and SpO(2) measurement from splanchnic organs. Following Local Research Ethics Committee approval, the sensor was evaluated on seventeen ASA 1 and 2 patients undergoing open laparotomy. PPG signals were obtained from the large bowel, small bowel, liver and stomach. Simultaneous PPG signals from the finger were also obtained using an identical fiber optic sensor. RESULTS: Good quality PPG signals with high signal-to-noise (SNR) ratios were obtained from all splanchnic sites under investigation. Analysis of the ac and dc amplitudes of the red and infrared PPG signals showed there to be a statistically significant difference between PPG signals obtained from splanchnic organs with those obtained from the finger (using fiber optic sensors). Estimated SpO(2) values from the splanchnic organs show good agreement with those obtained from the finger using both a fiber optic sensor and a commercial device. Furthermore, the results of a Bland and Altman analysis indicate that fiber optic splanchnic pulse oximetry, particularly of the bowel, may provide a suitable method for monitoring splanchnic organ perfusion. CONCLUSION: The evaluation of a new fiber optic sensor on anaesthetized patients undergoing laparotomy demonstrated that good quality PPG signals and SpO(2) estimates can be obtained from splanchnic organs. Such a sensor may provide a useful tool for the intraoperative assessment of splanchnic perfusion.

A comparison of the respiratory effects of oxycodone versus morphine: a randomised, double-blind, placebo-controlled investigation.

Oxycodone's respiratory profile (particularly the extent of respiratory depression in comparison to morphine) remains to be fully characterised in the peri-operative period. We randomly assigned ASA 1-2 adults for elective surgery under general anaesthesia to receive saline, morphine 0.1 mg.kg⁻¹, or oxycodone 0.05 mg.kg⁻¹, 0.1 mg.kg⁻¹, or 0.2 mg.kg(-1) . Results were obtained from six patients in the saline group, 12 patients in the groups receiving morphine 0.1 mg.kg⁻¹, oxycodone 0.05 mg.kg⁻¹ and 0.1 mg.kg⁻¹, and from 10 patients who received oxycodone 0.2 mg.kg⁻¹. Patients were breathing spontaneously and minute ventilation monitored with a wet wedge spirometer for 30 min. All active groups demonstrated significant respiratory depression compared to saline (p < 0.0001 for all groups). The mean (SD) reduction in minute volume from baseline was 22.6% (10.4%) for the morphine 0.1 group and 53.3% (27.2%), 74.4% (12.9%) and 88.6% (13.5%) for the oxycodone 0.05, 0.1 and 0.2 groups, respectively, with significant dose dependent differences between oxycodone groups (p = 0.0007). The extent and speed of onset of oxycodone induced respiratory depression was dose dependent and greater than an equivalent dose of morphine.

Investigation of dentinal tubule occlusion using FIB-SEM milling and EDX.

OBJECTIVE: The aim of this study was to evaluate in vitro the dentin tubule occluding effect of an 8% strontium acetate dentifrice (Sensodyne Rapid Relief) compared to patent dentin tubules using modern sample preparation, imaging, and analysis techniques. METHODS: Etched dentin discs, either untreated or treated with the dentifrice, were analyzed by preparing cross-sections using focused ion beam scanning electron microscopy (FIB-SEM) milling, and the strontium presence mapped using energy dispersive X-ray spectroscopy (EDX). RESULTS: Surface imaging showed the dentifrice had coated the treated sample. Sub-surface information gained by preparing longitudinal cross-sections of the treated samples showed the tubule openings to be plugged, and EDX mapping of the cross-section confirmed enhanced strontium levels within the tubules several microns below the treatment surface. CONCLUSION: The combination of modern sample preparation, imaging, and analysis techniques employed in this study has shown that the 8% strontium acetate dentifrice occludes dentin tubules. EDX analysis has shown the presence of strontium within the dentin tubules, with elemental maps illustrating how the strontium has been incorporated into the dentin.

Pain assessment and management in medical wards: an area of unmet need.

BACKGROUND: Acute Pain Services (APS) were introduced primarily to improve postoperative pain management. Although pain is similar in prevalence and severity in medical and surgical wards, its assessment and management in non-surgical patients often receives less attention and resources. OBJECTIVE: To investigate the extent of APS involvement on medical wards and obtain perceptions of deficiencies. METHOD: A questionnaire was mailed to APS leads in 287 UK NHS hospitals; 229 questionnaires were returned (79.8% response). RESULTS: Only 36 (16%) of the 225 hospitals with medical wards reported routine APS involvement. Pain scores were not recorded in 75 (33%) hospitals, 11 (5%) denied knowledge about assessments being conducted, and 185 (82.2%) respondents felt that pain management on medical wards was inadequate. CONCLUSIONS: Perceived lack of training and awareness of healthcare staff were highly ranked contributing factors, and this was attributed to inadequate funding. This study highlights the scope for improvement of pain control in medical patients, with benefits from reduced morbidity and faster recovery.

Cerebral arterial oxygen saturation measurements using a fiber-optic pulse oximeter.

BACKGROUND: A pilot investigation was undertaken to assess the performance of a novel fiber-optic cerebral pulse oximetry system. A fiber-optic probe designed to pass through the lumen of a cranial bolt of the type used to make intracranial pressure measurements was used to obtain optical reflectance signals directly from brain tissue. METHODS: Short-duration measurements were made in six patients undergoing neurosurgery. These were followed by a longer duration measurement in a patient recovering from an intracerebral hematoma. Estimations of cerebral arterial oxygen saturation derived from a frequency domain-based algorithm are compared with simultaneous pulse oximetry (SpO2) and hemoximeter (SaO2) blood samples. RESULTS: The short-duration measurements showed that reliable photoplethysmographic signals could be obtained from the brain tissue. In the long-duration study, the mean (±SD) difference between cerebral oxygen saturation (ScaO2) and finger SpO2 (in saturation units) was -7.47(±3.4)%. The mean (±SD) difference between ScaO2 and blood SaO2 was -7.37(±2.8)%. CONCLUSIONS: This pilot study demonstrated that arterial oxygen saturation may be estimated from brain tissue via a fiber-optic pulse oximeter used in conjunction with a cranial bolt. Further studies are needed to confirm the clinical utility of the technique.

Preliminary evaluation of a new fibre-optic cerebral oximetry system.

A new system for measuring the oxygen saturation of blood within tissue has been developed, for a variety of patient monitoring applications. A particular unmet need is in the central nervous system, and this project aims to devise a means for measuring blood oxygen saturation in the brain tissue of patients recovering from neurosurgery or head injury. Coupling light sources and a photodetector to optical fibres results in a probe small enough to pass through a cranial bolt of the type already in use for intra-cranial pressure monitoring. The development and evaluation of a two-wavelength fibre-optic reflectance photoplethysmography (PPG) system are described. It was found that good quality red and near-infrared PPG signals could be obtained from the finger using a fibre-optic probe. Experiments were conducted to find the inter-fibre spacings that yield signals most suitable for calculating oxygen saturation. Reliable signals could be obtained for inter-fibre spacings between 2 mm and 5 mm, the latter being the size of the maximum aperture in the cranial bolt. A preliminary measurement from human brain tissue is also presented.

In situ lift-out: steps to improve yield and a comparison with other FIB TEM sample preparation techniques.

Steps to improve the success yield of the in situ lift-out technique are presented. These include tapping the plinth of the system and monitoring the grounding current to check the lift-out needle is fixed to the material being removed. In addition, the relative success yields and the time to prepare a TEM lamella for the three main FIB methods are discussed and compared.

Intravenous parecoxib rapidly leads to COX-2 inhibitory concentration of valdecoxib in the central nervous system.

Evidence in animal studies supports widespread induction of cyclooxygenase-2 (COX-2) in the central nervous system (CNS) following tissue injury, probably mediated by cytokines, transducing the signal across the blood-brain barrier. CNS COX-2 blockade is a possible therapeutic target for drugs that are able to reach adequate CNS levels and abolish the prostaglandin E2-induced central sensitization. This human pharmacokinetic study investigated valdecoxib cerebrospinal fluid (CSF) and plasma concentrations over time in 37 patients following 40 mg of single-dose intravenous parecoxib. High-performance liquid chromatography/tandem mass spectrometry analysis was performed. Valdecoxib was first detectable in the CSF at 15 min postdosing, increased rapidly until 50 min, and thereafter remained between 6 and 14 ng/ml. This is the first human study demonstrating CNS COX-2 inhibitor penetration as early as 15 min. CSF valdecoxib concentration rapidly reached in vitro IC50 (inhibitory concentration 50) (1.57 ng/ml) by 17 min and remained consistently higher thereafter.

Current practices for postoperative pain management in Europe and the potential role of the fentanyl HCl iontophoretic transdermal system.

Survey results continue to reveal that postoperative pain is insufficiently managed throughout Europe and the rest of the world. However, the efficient use of existing resources, as well as the introduction of novel technologies, may aid in its improvement. Use of an acute pain service has the potential to improve pain management through specialized patient care and utilization of effective analgesic techniques. Multimodal analgesic techniques, which include adjuvant non-opioids and/or regional analgesic techniques, can provide effective analgesia and reduce the amount of systemic opioids (or obviate the need) for postoperative pain management. Patient-controlled analgesia modalities may also offer improvements to pain management, as in practice they provide pain relief superior to the intermittent administration of bolus doses of opioids. A novel patient-controlled analgesia modality that has been approved by the European Medicines Evaluation Agency (EMEA) for the treatment of acute, moderate-to-severe pain is the needle-free, pre-programmed fentanyl HCl iontophoretic transdermal system. This system was shown in a recent US clinical trial to be comparable in efficacy to a standard regimen of morphine intravenous patient-controlled analgesia. Adverse events associated with the use of the fentanyl iontophoretic transdermal system are generally similar to those experienced by patients using intravenous morphine patient-controlled analgesia. Considerations regarding the selection of patients for treatment with the fentanyl iontophoretic transdermal system are similar to those with other patient-controlled analgesia modalities; sufficient upper limb mobility and alertness are required to operate the system. Utilization of the fentanyl iontophoretic transdermal system, together with the guidance of an effective acute pain service, may lead to improvements in postoperative pain management.

Fabrication of nickel nanocontacts using nanostencils and electron beam assisted SiO2 deposition.

Nickel nanocontacts for studying ballistic magnetoresistance have been fabricated by sputtering through FIB prepared nanostencil masks and by using electron beam assisted deposition of SiO2 to reduce the size of FIB milled pores through silicon nitride membranes. These two methods are discussed in terms of the nanocontact sizes, fabrication, and yield. The smallest size of the nanocontacts prepared using the nanostencil method was 40 nm and by the filling method was 1-2 nm. The maximum magnetoresistance measured was 1% and no evidence of a large ballistic magnetoresistance was observed.

Filtering techniques for the removal of ventilator artefact in oesophageal pulse oximetry.

The oesophagus has been shown to be a reliable site for monitoring blood oxygen saturation (SpO(2)). However, the photoplethysmographic (PPG) signals from the lower oesophagus are frequently contaminated by a ventilator artefact making the estimation of SpO(2) impossible. A 776th order finite impulse response (FIR) filter and a 695th order interpolated finite impulse response (IFIR) filter were implemented to suppress the artefact. Both filters attenuated the ventilator artefact satisfactorily without distorting the morphology of the PPG when processing recorded data from ten cardiopulmonary bypass patients. The IFIR filter was the better since it conformed more closely to the desired filter specifications and allowed real-time processing. The average improvements in signal-to-noise ratio (SNR) achieved by the FIR and IFIR filters for the fundamental component of the red PPG signals with respect to the fundamental component of the artefact were 57.96 and 60.60 dB, respectively. The corresponding average improvements achieved by the FIR and IFIR filters for the infrared PPG signals were 54.83 and 60.96 dB, respectively. Both filters were also compared with their equivalent tenth order Butterworth filters. The average SNR improvements for the FIR and IFIR filters were significantly higher than those for the Butterworth filters.

Selective cyclooxygenase inhibition: its role in pain and anaesthesia.

Cyclooxygenase inhibitors reduce inflammation and hyperalgesia by decreasing prostaglandin E2 production. Traditional NSAIDs (inhibiting both COX-1 and 2) though ubiquitous in peri-operative pain practice, have well-known gastrointestinal (GI), cardiovascular and other risks. This article systematically addresses the main efficacy and safety issues pertaining to NSAID and selective COX-2 inhibitors (coxibs) use, focusing on the acute pain context, particularly post-operative pain management. NSAIDs and coxibs are of proven analgesic efficacy in post-operative pain control, and their opioid-sparing role in multimodal analgesia, leads to significantly reduced opioid related side effects. Although GI risk is regarded as less of an issue in short-term therapy, in patients with a past history of peptic ulceration who are denied NSAIDs, coxibs may be considered a suitable alternative. In the peri-operative setting, coxibs confer an additional advantage over NSAIDs by preserving the platelet thromboxane production and clotting. Cardiovascular safety has been assessed for the parenteral parecoxib and its active moiety valdecoxib, and was found to be satisfactory in major non-cardiac surgery, but increased thromboembolic complications occurred in coronary artery bypass surgery leading to contra-indication for this type of surgery. Coxibs and NSAIDs have similar renal effects and caution or avoidance is required with renal disease or reduced peri-operative renal perfusion. Coxibs may be safer in aspirin-sensitive asthmatics. Bone healing effects remain controversial, but only a few days therapy appears to be safe.