Oxygen saturation in intraosseous sternal blood measured by CO-oximetry and evaluated non-invasively during hypovolaemia and hypoxia - a porcine experimental study.

PURPOSE: This study intended to determine, and non-invasively evaluate, sternal intraosseous oxygen saturation (SsO2) and study its variation during provoked hypoxia or hypovolaemia. Furthermore, the relation between SsO2 and arterial (SaO2) or mixed venous oxygen saturation (SvO2) was investigated. METHODS: Sixteen anaesthetised male pigs underwent exsanguination to a mean arterial pressure of 50 mmHg. After resuscitation and stabilisation, hypoxia was induced with hypoxic gas mixtures (air/N2). Repeated blood samples from sternal intraosseous cannulation were compared to arterial and pulmonary artery blood samples. Reflection spectrophotometry measurements by a non-invasive sternal probe were performed continuously. RESULTS: At baseline SaO2 was 97.0% (IQR 0.2), SsO2 73.2% (IQR 19.6) and SvO2 52.3% (IQR 12.4). During hypovolaemia, SsO2 and SvO2 decreased to 58.9% (IQR 16.9) and 38.1% (IQR 12.5), respectively, p < 0.05 for both, whereas SaO2 remained unaltered (p = 0.44). During hypoxia all saturations decreased; SaO2 71.5% (IQR 5.2), SsO2 39.0% (IQR 6.9) and SvO2 22.6% (IQR 11.4) (p < 0.01), respectively. For hypovolaemia, the sternal probe red/infrared absorption ratio (SQV) increased significantly from baseline (indicating a reduction in oxygen saturation) + 5.1% (IQR 7.4), p < 0.001 and for hypoxia + 19.9% (IQR 14.8), p = 0.001, respectively. CONCLUSION: Sternal blood has an oxygen saturation suggesting a mixture of venous and arterial blood. Changes in SsO2 relate well with changes in SvO2 during hypovolaemia or hypoxia. Further studies on the feasibility of using non-invasive measurement of changes in SsO2 to estimate changes in SvO2 are warranted.

Long-Term Follow-Up of Pediatric Patients with Severe Postoperative Pulmonary Hypertension After Correction of Congenital Heart Defects.

The surgical repair of congenital heart defects in children with preoperative pulmonary hypertension (PH) is to varying degree associated with the occurrence of postoperative PH. The objective of this study was to follow up children with severe postoperative PH (pulmonary arterial/aortic pressure ratio ≥ 1.0) to evaluate if pulmonary arterial pressure spontaneously normalized or needed PH-targeting therapy and to identify potential high-risk diagnoses for bad outcome. Twenty-five children who developed clinically significant severe PH on at least three occasions postoperatively were included in the follow-up (20-24 years). Data from chart reviews, echocardiographic investigations, and questionnaires were obtained. Three children died within the first year after surgery. Three children were lost to follow-up. The remaining 17 children normalized their pulmonary arterial pressure without the use of PH-targeting drugs at any time during the follow-up. Two children had a remaining mild PH with moderate mitral valve insufficiency. All three children with bad outcome had combined cardiac lesions causing post-capillary pulmonary hypertension. Normalization of the pulmonary arterial pressure occurred in almost all children with severe postoperative PH, without any need of supplemental PH-targeting therapies. All children with bad outcome had diagnoses conformable with post-capillary PH making the use of PH-targeting therapies relatively contraindicated. These data emphasize the need to perform randomized, blinded trials on the use of PH-targeting drugs in children with postoperative PH before accepting it as an indication for routine treatment.

Indexing haemodynamic variables in young children.

BACKGROUND: Haemodynamic studies in children are rare and most studies have included few subjects in the youngest age group. Haemodynamic variables need to be indexed to establish a reference of normality that is valid in all populations. The traditional way to index haemodynamic variables with body surface area (BSA) is complicated in young children due to its non-linear relationship with body weight (BW). We examined several haemodynamic variables in children by indexing them with BSA and BW. METHODS: A single-centre, observational cohort study comparing non-indexed and indexed haemodynamic variables in children undergoing heart surgery (divided into three weight groups: 1-5 kg, >5-10 kg and >10-15 kg). RESULTS: A total of 68 children were included in this study, mean age 11.1 months ± 11.1 month (range 0 to 43 months). All haemodynamic variables, cardiac output (CO), stroke volume (SV), total end-diastolic volume (TEDV), central blood volume (CBV) and active circulation volume (ACV), increased with weight without indexing (P < .05). Indexing variables with BW produced a more linear relationship for all haemodynamic variables between weight groups than BSA. The mean BSA-indexed haemodynamic values were CIBSA 3.5 ± 1.1 L/min/m2 and SVIBSA 27.3 ± 8.9 ml/min/m2 . The mean BW-indexed haemodynamic values were CIBW 180 ± 50 ml/min/kg and SVIBW 1.34 ± 0.38 ml/kg. Blood volume variables indexed with BW were TEDVBW 12.0 ± 2.8 ml/kg, CBVBW 21.3 ± 6.6 ml/kg and ACVBW 70.3 ± 15.2 ml/kg. CONCLUSIONS: Indexing haemodynamic variables with BW produces a more appropriate body size-independent scale in young children than BSA. SUMMARY STATEMENT: In this study, we studied indexing of haemodynamic variables and estimation of blood volumes in young children undergoing corrective heart surgery using an indicator dilution technology.

Broadening risk profile in familial colorectal cancer type X; increased risk for five cancer types in the national Danish cohort.

BACKGROUND: Familial colorectal cancer type X (FCCTX) is a phenotypically defined subset of hereditary colorectal cancer with unknown and potentially heterogeneous genetic aetiology. FCCTX has been characterized as a colorectal cancer-specific syndrome, which we herein challenge by estimating the risk for extra-colorectal cancer in the Danish FCCTX cohort. METHODS: Through the national hereditary non-polyposis colorectal cancer (HNPCC) register, 213 families fulfilling the Amsterdam I criteria and showing retained mismatch repair (MMR) function were identified. In here, sex and age-specific incidence rate ratios (IRR) were calculated for 30 extra-colorectal cancer types in comparison with the general Danish population. RESULTS: In total, 494 extra-colorectal cancers developed with significantly increased risks for cancers of the urinary tract, breast, stomach, pancreas, and eye tumours. The age groups at increased risks were 30-49 years for gastric cancer, 30-69 years for female breast cancer, 50-69 years for ocular melanoma and above age 70 for pancreatic cancer and urothelial cancer. CONCLUSIONS: Danish FCCTX families show an increased risk of several extra-colorectal cancer types. This observation may indicate unidentified disease-predisposing genetic variants in this phenotypically defined subset of hereditary colorectal cancer and calls for awareness during genetic counselling and follow-up.

Six commonly used empirical body surface area formulas disagreed in young children undergoing corrective heart surgery.

AIM: Formulas for empirical body surface area (BSA), which is used to estimate body size and standardise physiological parameters, may disagree in children. We compared six commonly used BSA formulas-Du Bois, Boyd, Costeff, Haycock, Meban and Mosteller-in a surgical cohort. METHODS: This retrospective single-centre cohort study comprised 68 children who had corrective heart surgery at Skåne University Children's Hospital, Lund, Sweden, from February 2010 to March 2017. RESULTS: The children (51% female) underwent surgery at a mean weight of 7.0 kilograms (range 2.7-14.1 kg) and a mean age 11 months (range 0-43 months). All the BSA formulas showed good correlation with mean BSA, but there were considerable variations between them. Mosteller's formula was exactly the same as the mean BSA (bias 0.000). The Du Bois and Boyd formulas had the largest mean BSA deviations (bias -0.012 and 0.015). Costeff's formula showed good agreement with mean BSA, Haycock's formula showed minimal overestimation and Meban's formula demonstrated a systemic error in older children. CONCLUSION: Commonly used BSA formulas did not agree in young children undergoing heart surgery, but they were all close to the overall mean of the six formulas, with the Mosteller formula producing the same value.

Indirect Calorimetry Overestimates Oxygen Consumption in Young Children: Caution is Advised Using Direct Fick Method as a Reference Method in Cardiac Output Comparison Studies.

Direct Fick method is considered a standard reference method for estimation of cardiac output. It relies on indirect calorimetry to measure oxygen consumption. This is important as only a minor measurement error in oxygen consumption can result in false estimation of cardiac output. A number of studies have shown that indirect calorimetry overestimates oxygen consumption in adults. The aim of this prospective single center observational method comparison study was to compare the determination of oxygen consumption by indirect calorimetry and reverse Fick method in pediatric patients. Forty-two children mean age 352 days (range 30 to 1303 days) and mean weight 7.1 kg (range 2.7-13.6 kg) undergoing corrective cardiac surgery were included in the study. The mean (standard deviation) oxygen consumption by reverse Fick method was 43.5 (16.2) ml/min and by indirect calorimetry 49.9 (18.8) ml/min (p < 0.001). Indirect calorimetry overestimated the reverse Fick oxygen consumption by 14.7%. Bias between methods was 6.5 (11.3) ml/min, limits of agreement (LOA) - 15.7 and 28.7 ml/min and percentage error of 47.7%. A significant bias and large percentage error indicates that the methods are not interchangeable. Indirect calorimetry and the direct Fick method should be used with caution as a reference method in cardiac output comparison studies in young children.

Measuring arterial oxygen saturation from an intraosseous photoplethysmographic signal derived from the sternum.

Photoplethysmography performed on the peripheral extremities or the earlobes cannot always provide sufficiently rapid and accurate calculation of arterial oxygen saturation. The purpose of this study was to evaluate a novel photoplethysmography prototype to be fixed over the sternum. Our hypotheses were that arterial oxygen saturation can be determined from an intraosseous photoplethysmography signal from the sternum and that such monitoring detects hypoxemia faster than pulse oximetry at standard sites. Sixteen healthy male volunteers were subjected to incremental hypoxemia using different gas mixtures with decreasing oxygen content. The sternal probe was calibrated using arterial haemoglobin CO-oximetry (SaO2%). Sternal probe readings (SRHO2%) were then compared to SaO2% at various degrees of hypoxia. The time to detect hypoxemia was compared to measurements from standard finger and ear pulse oximeters. A significant association from individual regression between SRHO2% and SaO2% was found (r2 0.97), Spearman R ranged between 0.71 and 0.92 for the different inhaled gas mixtures. Limits of agreement according to Bland-Altman plots had a increased interval with decreasing arterial oxygen saturation. The sternal probe detected hypoxemia 28.7 s faster than a finger probe (95% CI 20.0-37.4 s, p < 0.001) and 6.6 s faster than an ear probe (95% CI 5.3-8.7 s, p < 0.001). In an experimental setting, arterial oxygen saturation could be determined using the photoplethysmography signal obtained from sternal blood flow after calibration with CO-oximetry. This method detected hypoxemia significantly faster than pulse oximetry performed on the finger or the ear.

Extracorporeal Arteriovenous Ultrasound Measurement of Cardiac Output in Small Children.

BACKGROUND: Technology for cardiac output (CO) and blood volume measurements has been developed based on blood dilution with a small bolus of physiologic body temperature saline, which, after transcardiopulmonary mixing, is detected with ultrasound sensors attached to an extracorporeal arteriovenous loop using existing central venous and peripheral arterial catheters. This study aims to compare the precision and agreement of this technology to measure cardiac output with a reference method, a perivascular flow probe placed around the aorta, in young children. The null hypothesis is that the methods are equivalent in precision, and there is no bias in the cardiac output measurements. METHODS: Forty-three children scheduled for cardiac surgery were included in this prospective single-center comparison study. After corrective cardiac surgery, five consecutive repeated cardiac output measurements were performed simultaneously by both methods. RESULTS: A total of 215 cardiac output measurements were compared in 43 children. The mean age of the children was 354 days (range, 30 to 1,303 days), and the mean weight was 7.1 kg (range, 2.7 to 13.6 kg). The precision assessed as two times the coefficient of error was 3.6% for the ultrasound method and 5.0% for the flow probe. Bias (mean COultrasound 1.28 l/min - mean COflow probe 1.20 l/min) was 0.08 l/min, limits of agreement was ±0.32 l/min, and the percentage error was 26.6%. CONCLUSIONS: The technology to measure cardiac output with ultrasound detection of blood dilution after a bolus injection of saline yields comparable precision as cardiac output measurements by a periaortic flow probe. The difference in accuracy in the measured cardiac output between the methods can be explained by the coronary blood flow, which is excluded in the cardiac output measurements by the periaortic flow probe.

Unnecessary harm is avoided by reliable paediatric index of mortality2 scores without arterial gas sampling.

AIM: To investigate whether unnecessary harm could be avoided in children admitted to paediatric intensive care (PICU), we analysed the impact of arterial blood gas on the paediatric index of mortality score2 (PIM2) and the derived predicted death rate (PDR). METHODS: From January 1, 2008 to December 31, 2010, 1793 consecutive admissions, newborn infants to 16 years of age (median 0.71 years) from a single, tertiary PICU in Gothenburg Sweden, were collected. Admission information on arterial oxygen tension (PaO2 ) and fraction of inspired oxygen (FiO2 ) was extracted from 990 admissions. RESULTS: There was close agreement between PIM2 score and PDR regardless of whether the PaO2 /FiO2 ratio was omitted or not. In the subgroup of admissions with a respiratory admission diagnosis, the inclusion of the PaO2 /FiO2 ratio increased the accuracy of the PIM2 score as well as the PDR. The standard mortality ratio was slightly but not significantly overestimated by excluding the PaO2 /FiO2 ratio. CONCLUSION: To avoid unnecessary harm to children admitted to PICU, an arterial blood gas analysis should only be performed if clinically indicated or if the child has a respiratory admission diagnosis. Estimation of the PIM2 score and PDR will not be less accurate by this approach.

Outcome of 24†years national surveillance in different hereditary colorectal cancer subgroups leading to more individualised surveillance.

BACKGROUND: Individuals with hereditary non-polyposis colorectal cancer (HNPCC) have a high risk of colorectal cancer (CRC). The benefits of colonic surveillance in Lynch syndrome and Amsterdam-positive (familial CRC type X familial colorectal cancer type X (FCCTX)) families are clear; only the interval between colonoscopies is debated. The potential benefits for families not fulfilling the Amsterdam criteria are uncertain. The aim of this study was to compare the outcome of colonic surveillance in different hereditary subgroups and to evaluate the surveillance programmes. METHODS: A prospective, observational study on the outcome of colonic surveillance in different hereditary subgroups based on 24 years of surveillance data from the national Danish HNPCC register. RESULTS: We analysed 13 444 surveillance sessions, including 8768 incidence sessions and 20 450 years of follow-up. CRC was more incident in the Lynch subgroup (2.0%) than in any other subgroup (0.0-0.4%, p<0.0001), but the incidence of advanced adenoma did not differ between the Lynch (3.6%) and non-Lynch (2.3-3.9%, p=0.28) subgroups. Non-Lynch Amsterdam-positive and Amsterdam-negative families were similar in their CRC (0.1-0.4%, p=0.072), advanced adenoma (2.3-3.3%, p=0.32) and simple adenoma (8.4-9.9%, p=0.43) incidence. In moderate-risk families, no CRC and only one advanced adenoma was found. CONCLUSIONS: The risk of CRC in Lynch families is considerable, despite biannual surveillance. We suggest less frequent and more individualised surveillance in non-Lynch families. Individuals from families with a strong history of CRC could be offered 5-year surveillance colonoscopies (unless findings at the preceding surveillance session indicate shorter interval) and individuals from moderate-risk families could be handled with the population-based screening programme for CRC after an initial surveillance colonoscopy.

Towards gene- and gender-based risk estimates in Lynch syndrome; age-specific incidences for 13 extra-colorectal cancer types.

BACKGROUND: In Lynch syndrome, inherited mismatch repair (MMR) defects predispose to colorectal cancer and to a wide spectrum of extra-colorectal tumours. Utilising a cohort study design, we aimed to determine the risk of extra-colorectal cancer and to identify yet unrecognised tumour types. METHODS: Data from 1624 Lynch syndrome mutation carriers in the Danish hereditary non-polyposis colorectal cancer register were used to estimate the sex- and age-specific incidence rate ratios (IRRs) for 30 extra-colorectal malignancies with comparison to the general population. RESULTS: Significantly increased IRRs were identified for 13 cancer types with differences related to gender, age and disease-predisposing gene. The different cancer types showed variable peak age incidence rates (IRs) with the highest IRs for ovarian cancer at age 30-49 years, for endometrial cancer, breast cancer, renal cell cancer and brain tumours at age 50-69 years, and for urothelial cancer, small bowel cancer, gastric cancer, pancreatic cancer and skin tumours after age 70. CONCLUSIONS: The broad spectrum of tumour types that develop at an increased incidence defines Lynch syndrome as a multi-tumour syndrome. The variable incidences in relation to age, gender and gene suggest a need for individualised surveillance.

Pressure-induced vasodilation and reactive hyperemia at different depths in sacral tissue under clinically relevant conditions.

OBJECTIVE: To characterize PIV and RH at different sacral tissue depths in different populations under clinically relevant pressure exposure. METHODS: Forty-two subjects (<65 years), 38 subjects (≥65 years), and 35 patients (≥65 years) participated. Interface pressure, skin temperature, and blood flow at tissue depths of 1, 2, and 10 mm (using LDF and PPG) were measured in the sacral tissue before, during, and after load in a supine position. RESULTS: Pressure-induced vasodilation and RH were observed at three tissue depths. At 10 mm depth, the proportion of subjects with a lack of PIV was higher compared to superficial depths. The patients had higher interface pressure during load than the healthy individuals, but there were no significant differences in blood flow. Twenty-nine subjects in all three study groups were identified with a lack of PIV and RH. CONCLUSIONS: Pressure-induced vasodilation and RH can be observed at different tissue depths. A lack of these responses was found in healthy individuals as well as in patients indicating an innate susceptibility in some individuals, and are potential important factors to evaluate in order to better understand the etiology of pressure ulcers.

Validation of an ultrasound dilution technology for cardiac output measurement and shunt detection in infants and children.

OBJECTIVE: To validate cardiac output measurements by ultrasound dilution technology (COstatus monitor) against those obtained by a transit-time ultrasound technology with a perivascular flow probe and to investigate ultrasound dilution ability to estimate pulmonary to systemic blood flow ratio in children. DESIGN: Prospective observational clinical trial. SETTING: Pediatric cardiac operating theater in a university hospital. MATERIAL AND METHODS: In 21 children (6.1 ± 2.6 kg, mean ± SD) undergoing heart surgery, cardiac output was simultaneously recorded by ultrasound dilution (extracorporeal arteriovenous loop connected to existing arterial and central venous catheters) and a transit-time ultrasound probe applied to the ascending aorta, and when possible, the main pulmonary artery. The pulmonary to systemic blood flow ratio estimated from ultrasound dilution curve analysis was compared with that estimated from transit-time ultrasound technology. RESULTS: Bland-Altman analysis of the whole cohort (90 pairs, before and after surgery) showed a bias between transit-time ultrasound (1.01 ± 0.47 L/min) and ultrasound dilution technology (1.03 ± 0.51 L/min) of -0.02 L/min, limits of agreement -0.3 to 0.3 L/min, and percentage error of 31%. In children with no residual shunts, the bias was -0.04 L/min, limits of agreement -0.28 to 0.2 L/min, and percentage error 19%. The pooled co efficient of variation was for the whole cohort 3.5% (transit-time ultrasound) and 6.3% (ultrasound dilution), and in children without shunt, it was 2.9% (transit-time ultrasound) and 4% (ultrasound dilution), respectively. Ultrasound dilution identified the presence of shunts (pulmonary to systemic blood flow ≠ 1) with a sensitivity of 100% and a specificity of 92%. Mean pulmonary to systemic blood flow ratio by transit-time ultrasound was 2.6 ± 1.0 and by ultrasound dilution 2.2 ± 0.7 (not significant). CONCLUSION: The COstatus monitor is a reliable technique to measure cardiac output in children with high sensitivity and specificity for detecting the presence of shunts.

Reliability of muscle blood flow measurements in orbicularis oculi.

PURPOSE: Orbicularis oculi muscle tension and muscle blood flow have been shown to be objective measures of eyestrain during visually demanding activities, such as computer work. In line with this, positive associations between eye-related pain and muscle blood flow in orbicularis oculi have been observed. A hypothesis regarding work situations with cognitive tasks and low-level muscle activity, such as computer work, proposes that muscle pain originates from the blood vessel-nociceptor interactions of the connective tissue of the muscle. Noninvasive muscle blood flow measurements in the orbicularis oculi muscle are preferable to using an invasive technique. The aim of this study was to test reproducibility and stability of muscle blood recordings in orbicularis oculi using photoplethysmography. METHODS: In the reproducibility tests, 12 subjects were tested twice within 1 to 5 weeks. To study the stability of the method, six of the subjects were randomly selected and tested four more times within 2 to 6 weeks. Test subjects were doing identical visually demanding computer work for 10 minutes in each test. RESULTS: The short-term repeatability of muscle blood flow measurements was considered good, but the stability of blood flow recordings over time in orbicularis oculi was low because of a greater within-subject maximum variability compared with between-subject average variability. CONCLUSIONS: Investigators should be aware of the effect of time, possibly attributed to confounding factors such as environmental changes and mental stress, when comparing photoplethysmography muscle blood flow recordings.

National Experiences from 30 Years of Provider-Mediated Cascade Testing in Lynch Syndrome Families-The Danish Model.

Cascade genetic testing and surveillance reduce morbidity and mortality in Lynch syndrome. However, barriers to conveying information about genetic disorders within families result in low uptake of genetic testing. Provider-mediated interventions may increase uptake but raise legal and ethical concerns. We describe 30 years of national experience with cascade genetic testing combining family- and provider-mediated contact in Lynch syndrome families in the Danish Hereditary Non-Polyposis Colorectal Cancer (HNPCC) Register. We aimed to estimate the added value of information letters to family members in Lynch syndrome families (provider-mediated contact) compared to family members not receiving such letters and thus relying on family-mediated contact. National clinical practice for cascade genetic testing, encompassing infrastructure, legislation, acceptance, and management of the information letters, is also discussed. Cascade genetic testing resulted in 7.3 additional tests per family. Uptake of genetic testing was 54.4% after family-mediated and 64.9% after provider-mediated contact, corresponding to an odds ratio of 1.8 (p < 0.001). The uptake of genetic testing was highest in the first year after diagnosis of Lynch syndrome in the family, with 72.5% tested after provider-mediated contact. In conclusion, the Danish model combining family- and provider-mediated contact can increase the effect of cascade genetic testing.

Different lying positions and their effects on tissue blood flow and skin temperature in older adult patients.

AIM: To report a study to compare the effects of different lying positions on tissue blood flow and skin temperature in older adult patients. This article reports the evaluation of study design and procedures. BACKGROUND: To reduce risk of pressure ulcers, repositioning of immobile patients is a standard nursing practice; however, research into how different lying positions effect tissue microcirculation is limited. DESIGN: Descriptive comparative design. METHODS: From March-October 2010, 20 inpatients, aged 65 years or older, were included in the study. Tissue blood flow and skin temperature were measured over bony prominences and in gluteus muscle in four supine and two lateral positions. RESULTS: The blood flow over the bony prominence areas was most influenced in the superficial skin and especially in the 30° lateral position, where the blood flow decreased significantly in comparison with the supine positions. There were significant individual differences in blood flow responses, but no common trend was identified among the patients considered at risk for pressure ulcer development. The study procedure worked well and was feasible to perform in an inpatient population. CONCLUSION: The lying positions seem to influence the tissue blood flow over the bony prominences in different ways in older adult inpatients, but further study is needed to confirm the results and to make recommendations to clinical practice. The study procedure worked well, although some minor adjustments with regard to heat accumulation will be made in future studies.

New photoplethysmographic signal analysis algorithm for arterial stiffness estimation.

The ability to identify premature arterial stiffening is of considerable value in the prevention of cardiovascular diseases. The "ageing index" (AGI), which is calculated from the second derivative photoplethysmographic (SDPPG) waveform, has been used as one method for arterial stiffness estimation and the evaluation of cardiovascular ageing. In this study, the new SDPPG analysis algorithm is proposed with optimal filtering and signal normalization in time. The filter parameters were optimized in order to achieve the minimal standard deviation of AGI, which gives more effective differentiation between the levels of arterial stiffness. As a result, the optimal low-pass filter edge frequency of 6 Hz and transitionband of 1 Hz were found, which facilitates AGI calculation with a standard deviation of 0.06. The study was carried out on 21 healthy subjects and 20 diabetes patients. The linear relationship (r = 0.91) between each subject's age and AGI was found, and a linear model with regression line was constructed. For diabetes patients, the mean AGI value difference from the proposed model y AGI was found to be 0.359. The difference was found between healthy and diabetes patients groups with significance level of P < 0.0005.

Eye-related pain induced by visually demanding computer work.

PURPOSE: Eye strain during visually demanding computer work may include glare and increased squinting. The latter may be related to elevated tension in the orbicularis oculi muscle and development of muscle pain. The aim of the study was to investigate the development of discomfort symptoms in relation to muscle activity and muscle blood flow in the orbicularis oculi muscle during computer work with visual strain. METHODS: A group of healthy young adults with normal vision was randomly selected. Eye-related symptoms were recorded during a 2-h working session on a laptop. The participants were exposed to visual stressors such as glare and small font. Muscle load and blood flow were measured by electromyography and photoplethysmography, respectively. RESULTS: During 2 h of visually demanding computer work, there was a significant increase in the following symptoms: eye-related pain and tiredness, blurred vision, itchiness, gritty eyes, photophobia, dry eyes, and tearing eyes. Muscle load in orbicularis oculi was significantly increased above baseline and stable at 1 to 1.5% maximal voluntary contraction during the working sessions. Orbicularis oculi muscle blood flow increased significantly during the first part of the working sessions before returning to baseline. There were significant positive correlations between eye-related tiredness and orbicularis oculi muscle load and eye-related pain and muscle blood flow. Subjects who developed eye-related pain showed elevated orbicularis oculi muscle blood flow during computer work, but no differences in muscle load, compared with subjects with minimal pain symptoms. CONCLUSIONS: Eyestrain during visually demanding computer work is related to the orbicularis oculi muscle. Muscle pain development during demanding, low-force exercise is associated with increased muscle blood flow, possible secondary to different muscle activity pattern, and/or increased mental stress level in subjects experiencing pain compared with subjects with minimal pain.

The use of propofol sedation in a paediatric intensive care unit.

BACKGROUND: The aim of this study was to prospectively evaluate and report the experience of the use of continuous intravenous propofol sedation in a paediatric intensive care unit (PICU). METHODS: All children younger than 16 years who were admitted to the PICU at a University Hospital for slightly more than a year and received propofol infusion were included prospectively and data were recorded before and within 6 h after completion of the propofol infusion. RESULTS: A total of 174 out of 955 children (18·2%) received propofol infusion for sedation. The median age was 2 years 10 months (range: 2 months to 16 years), duration of propofol infusion 13 h (range: 1·6-179 h) and dose of propofol 2·9 mg/kg/h (range: 0·3-6·5 mg/kg/h). No one developed signs of the propofol infusion syndrome (PRIS). Neither dose >3 mg/kg/h, duration of infusion >48 h nor both were found to be related to adverse metabolic derangements or circulatory failure. Eight children increased their lactate concentration ≥1·8 mmol/L during propofol infusion. All had a favourable outcome. One child who had received propofol infusion for 10 h died, but this occurred 14 h after the infusion ceased and was without doubt attributed to a multiple organ failure not related to the propofol infusion. CONCLUSION: Propofol infusion was used in this population at low risk of PRIS with no metabolic or circulatory adverse effects. These findings indicate that the occurrence of adverse effects may not be directly related to dose or duration of infusion, but emphasizes the risk that sporadic factors may be involved, such as genetic mutations. Guidelines are presented.

The advantages of standardizing exhaled breath-alcohol concentration to a reference respiratory gas-water vapor.

Measuring the concentration of alcohol (ethanol) in exhaled breath (BrAC) provides a rapid and non-invasive way to determine the co-existing concentration in arterial blood (A-BAC). The results of breath-alcohol testing are used worldwide as evidence of excessive drinking, such as when traffic offenders are prosecuted. Two types of breath-alcohol analyzer are in common use; hand-held instruments used as preliminary screening tests of sobriety and more sophisticated evidential instruments, the results of which are accepted as evidence for prosecution of drunken drivers. Most evidential breath-alcohol analyzers are designed to capture the last portion of a prolonged exhalation, which is thought to reflect the alcohol concentration in substantially alveolar air. The basic premise of breath-alcohol analysis is that there is a physiological relationship between A-BAC and BrAC and close agreement between the two analytical methods. This article reviews the principles and practice of breath-alcohol analysis and introduces the concept of standardizing the results to a secondary physiological gas (water vapor), which therefore serves as an internal standard. The measured BrAC is thus adjusted to an alveolar air water content of 43.95 mg l-1at 37 °C. This has several advantages, and means that a sample of breath can be captured without the person having to blow directly into the instrument. Adjusting the breath-alcohol concentration to water vapor concentration also compensates for variations in temperature of the expired air. The contact-free method of sampling breath means that a mouthpiece is unnecessary and the test subject does not need to make a continuous end exhalation.