Bubble chamber clotting during continuous renal replacement therapy: vertical versus horizontal blood flow entry.

BACKGROUND: The continuous renal replacement therapy (CRRT) bubble trap chamber is a frequent site of clotting. AIMS: To assess clot formation when comparing our standard 'vertical' blood entry chamber (BEC) with a new 'horizontal' BEC. METHODS: Adult ICU patients requiring CRRT were treated with the vertical BEC and then a similar subsequent cohort with the horizontal BEC in continuous veno-venous haemofiltration mode. RESULTS: 40 chambers were assessed for each design. Circuit life was 13.9 ± 9.5 h for the vertical and 17.7 ± 15.9 h for the horizontal BEC (p = 0.33). APTT, however, was higher for the horizontal BEC (55.7 ± 34.7 vs. 37.4 ± 9.0, p < 0.002) and no difference in circuit life was found after multivariable analysis. A clotting score ≥3 was observed in 85% of all chambers. There was no difference in chamber clotting score (vertical 3.6 ± 1.03 vs. horizontal 3.8 ± 1.0, p = 0.5). In addition, no difference was found when scores were divided into two groups using a 'likelihood' to clot analysis (p = 1.0). CONCLUSION: CRRT horizontal BEC were not associated with less clotting compared to our standard vertical BEC.

Prosthetic limb sockets from plant-based composite materials.

BACKGROUND: There is a considerable demand for lower limb prostheses globally due to vascular disease, war, conflict, land mines and natural disasters. Conventional composite materials used for prosthetic limb sockets include acrylic resins, glass and carbon fibres, which produce harmful gasses and dust in their manufacture. OBJECTIVES: To investigate the feasibility of using a renewable plant oil-based polycarbonate-polyurethane copolymer resin and plant fibre composite, instead of conventional materials, to improve safety and accessibility of prosthetic limb manufacture. STUDY DESIGN: Experimental, bench research. METHODS: Test pieces of the resin with a range of plant fibres (10.0% by volume) were prepared and tensile strengths were tested. Test sockets of both conventional composite materials and plant resin with plant fibres were constructed and tested to destruction. RESULTS: Combinations of plant resin and either banana or ramie fibres gave high tensile strengths. The conventional composite material socket and plant resin with ramie composite socket failed at a similar loading, exceeding the ISO 10328 standard. Both wall thickness and fibre-matrix adhesion played a significant role in socket strength. CONCLUSIONS: From this limited study we conclude that the plant resin and ramie fibre composite socket has the potential to replace the standard layup. Further mechanical and biocompatibility testing as well as a full economic analysis is required. CLINICAL RELEVANCE: Using readily sourced and renewable natural fibres and a low-volatile bio-resin has potential to reduce harm to those involved in the manufacture of artificial limb sockets, without compromising socket strength and benefitting clinicians working in poorer countries where safety equipment is scarce. Such composite materials will reduce environmental impact.

Understanding the continuous renal replacement therapy circuit for acute renal failure support: a quality issue in the intensive care unit.

Delivery of renal replacement therapy is now a core competency of intensive care nursing. The safe and effective delivery of this form of therapy is a quality issue for intensive care, requiring an understanding of the principles underlying therapy and the functioning of machines used. Continuous hemofiltration, first described in 1977, used a system where blood flowed from arterial to venous cannulas through a small-volume, low-resistance, and high-flux filter. Monitoring of these early systems was limited, and without a machine interface, less nursing expertise was required. Current continuous renal replacement therapy machines offer user-friendly interfaces, cassette-style circuits, and comprehensive circuit diagnostics and monitoring. Although these machines conceal complexity behind a user-friendly interface, it remains important that nurses have sufficient knowledge for their use and the ability to compare and contrast circuit setups and functions for optimal and efficient treatment.

Paracetamol induced skin blood flow and blood pressure changes in febrile intensive care patients: An observational study.

OBJECTIVE: To determine the relationship between paracetamol administration and skin blood flow (skBF) and blood pressure (BP) in critically ill patients treated for fever. DESIGN: Prospective, observational study. SETTING: Intensive care units of university teaching hospital. PATIENTS: 29 adults (17 males and 12 females), aged 58±15 years treated with enteral or intravenous paracetamol for fever. APACHE II score was 17.2±8.3 and admission classifications were 41% medical (n=12), 31% surgical (n=9), and 28% neurological intervention (n=8). Thirty healthy afebrile volunteers were also studied after ingesting 1g paracetamol. MEASUREMENTS AND MAIN RESULTS: Temperature, BP and skBF (laser Doppler flowmetry perfusion units) were recorded 15 min prior to administration of paracetamol, at administration (T0) and then for every 15 min for 60 min. Cutaneous vascular conductance (CVC=skBF/mean arterial pressure) was calculated. Thirty data sets were recorded from 29 patients. Temperature at T0 was 38.7±0.6°C. BP decreased over the study period whilst skBF and CVC increased (repeated measured ANOVA, p<.05). Systolic BP decreased significantly (p<.01) at all post-administration times and was 90±13% of T0 at 60 min. CVC was 128±48% of T0 at 60 min. Systolic BP fell by a clinically significant amount (≥15%) in 17 patients (59%) and hypotension was treated during 33% (n=10) of the observation periods. BP and skBF did not change significantly in afebrile volunteers. CONCLUSIONS: Paracetamol induced increases in skBF consistent with its antipyretic action and may be associated with significant falls in BP in the critically ill.

Assessment of the clinical utility of an ultrasonic monitor of cardiac output (the USCOM) and agreement with thermodilution measurement.

OBJECTIVE: To assess the clinical utility of an ultrasonic monitor of cardiac output (USCOM), its reliability in tracking cardiac output (CO) changes and agreement with thermodilution (TD) measurements of CO. DESIGN: Prospective comparison study. SETTING AND PARTICIPANTS: 55 adults undergoing thermodilution (TD) CO monitoring in a cardiothoracic or general intensive care unit between December 2006 and December 2007. MAIN OUTCOME MEASURES: USCOM and TD measurements of CO on two occasions in each patient were compared by Bland-Altman analysis for bias and limit of agreement. A mean percentage error <30% was considered acceptable. Per cent change in cardiac index (CI) was determined by each method. Doppler profiles obtained by the USCOM were assessed against an ideal standard ("acceptable"). RESULTS: 55 patients had measurements on 110 occasions, but Doppler waveforms were not obtained on 18 of these (16%), leaving 39 patients with paired comparisons for analysis (including 27 men; mean age, 64.7 [SD, 14.5] years). Mean TD CI was 3.4 +/-1.0L/min/m(2) (range, 2.0-6.0L/min/m(2)). The bias was 0.6L/min/m(2) (95% confidence limits [CLs], 0.4-0.8 L/min/m(2)), and the mean percentage error was 56% (95% CLs, 45%-65%). Twenty-two Doppler profiles (28%) were classed as acceptable; the mean percentage error for these was 62% (95% CLs, 38%-65%). On 15/19 occasions (74%) where TD CI changed > 15%, USCOM CI also changed >15%, but three of these changes (16%) were in the opposite direction. USCOM CI changed >15% on 9/20 occasions (45%) when TD CI did not. CONCLUSIONS: Poor agreement with TD and a substantial rate of failure to obtain an USCOM measurement suggest that this device is unsuitable as a monitoring tool in intensive care.

Transition to intensive care nursing: establishing a starting point.

INTRODUCTION: There is a shortage of intensive care (IC) nurses. A supported transition to IC nursing has been identified as a key strategy for recruitment and retention. In 2004 a discussion document relating to transition of IC nurses was presented to the New South Wales (NSW) Chief Nursing Officer (CNO). A workshop was held with key stakeholders and a Steering Group was established to develop a state-wide transition to IC nursing program. AIMS: To survey orientation programs and educational resources and develop definitions, goals, learning objectives and clinical competencies relating to transition to IC nursing practice. METHODS: A questionnaire and a draft document of definitions, target group, goals, learning objectives and clinical competencies for IC transition was distributed to 43 NSW IC units (ICUs). An iterative process of anonymous feedback and modification was undertaken to establish agreement on content. RESULTS: Responses were received from 29 units (return rate of 67%). The survey of educational resources indicated ICUs had access to educational support and there was evidence of a lack of a common standard or definition for "orientation" or "transition". The definitions, target group, goals and competency statements from the draft document were accepted with minor editorial change. Seventeen learning objectives or psychomotor skills were modified and an additional 19 were added to the draft as a result of the process. CONCLUSION: This work has established valid definitions, goals, learning objectives and clinical competencies that describe transition to intensive care nursing.

Eyecare in the critically ill: clinical practice guideline.

OBJECTIVE: The Intensive Care Collaborative project was established with the specific aim of developing recommendations for clinical practice that are underpinned by the best available evidence to support the objective of improving the standard of care delivered in NSW Intensive Care Units. The eyecare clinical practice guideline for intensive care patients were developed as a result of this initiative. METHODS: Search: The bibliographic databases (PubMed; The Cummulative Index of Nursing and Allied Health Literature (CINAHL); Medline and The Cochrane Library) were searched. The search terms used alone and in combination were: intensive care; prevention; eye; eyecare; and guidelines. In addition, reference lists of relevant papers were assessed to identify additional studies and Google Scholar was searched using the keywords eyecare and intensive care. The search strategy was limited to the English language but was not limited by year of publication. Study selection criteria: All relevant observational and interventional studies were included, regardless of study design. Review process: Each paper was reviewed by at least two Guideline Development Network (GDN) members independently using a data extraction tool. Papers were assessed against the National Health and Medical Research Council (NHMRC) levels of evidence. Recommendations were assigned using a modified Delphi process to ensure consensus. SUMMARY OF RECOMMENDATIONS: We recommend that each patient is assessed for the risk factors of iatrogenic ophthalmologic complications; the ability to maintain eyelid closure; for iatrogenic ophthalmologic complications. It is also recommended that; the rates of iatrogenic ophthalmologic complications are monitored; referral is made in a timely manner for any suspected iatrogenic ophthalmologic complications; eyelid closure is maintained if eyelid closure cannot be maintained passively; all patients who cannot achieve eyelid closure independently should receive eye care every 2h. CONCLUSIONS: The recommendations from this clinical practice guideline were peer-reviewed and examined by ophthalmology experts. Despite the heavy reliance on only a small number of studies and low level of evidence, the recommendations have the potential to positively affect patient outcomes by encouraging clinicians to assess and monitor for ophthalmological complications and to provide appropriate preventative interventions if implemented extensively.

Assessment of the accuracy of continuous cardiac output and pulse contour cardiac output in tracking cardiac index changes induced by volume load.

OBJECTIVE: To assess the ability to track changes in cardiac index (Delta CI) induced by volume loading using continuous pulsed heat thermodilution (CCO), and pulse contour (PCCO) cardiac output (CO) with transpulmonary thermodilution (TD(tp)) CO as reference. DESIGN: Prospective observational clinical trial. SETTING: Intensive care unit. PATIENTS: Twelve ventilated and sedated post-operative cardiac surgery patients. MEASUREMENTS AND RESULTS: Each patient had a 7.5F CCO pulmonary artery catheter (Edwards Lifesciences) and a 5F, 20 cm PCCO femoral artery catheter (Pulsion Medical Systems). Forty-five data sets were taken before and after 25 volume loadings of 5 mL/kg of 4% albumin. Volume loading resulted in an increase in CI (2.84 L/(min m(2)) versus 3.12L/(min m(2)), p<.05) although only nine volume loadings changed CI (Delta CI)> or =14%. The change in CI using PCCO (Delta PCCI) was correlated with Delta CI (TD(tp)) (R(2)=.50, p<.0001), whilst Delta CI using CCO (Delta CCI) was not (R(2)=.14). The bias and limits of agreement (LOA) between Delta TD(tp)CI and Delta PCCI was 6.2% (95% CI, +/-5.8%) and 28.4% (95% CI, +/-38.2%) respectively. Delta TD(tp)CI and Delta CCI has a bias of 2.6% (95% CI, +/-8.3%) and LOA of 39.6% (95% CI, +/-63%). Both Delta PCCI and Delta CCI reliably tracked Delta CI> or =14%. CONCLUSION: In this small group of patients the continuous cardiac output methods tracked changes in CI, although, in individual cases they did not change in the same direction as the thermodilution method. Critical care nurses need to critically appraise the accuracy and clinical relevance of continuous CO data within the clinical context.

Comparison of dynamic measurements of pulse contour with pulsed heat continuous cardiac output in postoperative cardiac surgical patients.

Cardiac output (CO) can be measured using bolus thermodilution via a pulmonary artery catheter (PAC) and as continuous cardiac output (CCO), using pulsed heat thermoditution. Pulse contour cardiac output (PCCO) measures continuous CO by analysis of the arterial waveform after calibration with thermodilution CO. The Pulsion Medical Systems (PiCCO system) achieves this by transpulmonary aortic thermodilution (TDtpa). There is uncertainty regarding the agreement between TDtpa, CCO, and PCCO CO measurements in situations of rapid haemodynamic changes. We studied the agreement of the measures by comparing digital recordings of cardiac index (CI) determined by PCCO and CCO (PCCI and CCI, respectively) made during periods of haemodynamic instability. After ethics committee approval we studied four post-coronary artery bypass graft patients, in the immediate postoperative period. Each patient had a 7.5F CCO catheter (Edwards Lifesciences) and a 5F, 20cm PCCO femoral artery catheter. Digital recordings were obtained for the first 12-18 postoperative hours. Six epochs of instability were identified in the first two to three postoperative hours, and at the commencement of inotropic or vasoactive drugs. Notable features, despite frequent PCCO calibrations, were the marked difference of PCCI compared to CCI. In contradistinction, they tracked very closely during a period of stability. Limitations of both methods were noted. Whilst PCCO responded to rapid change, it developed significant error during haemodynmamic instability and requires frequent recalibration. CCO on the other hand has a considerable time lag in responding to changes in CO. The way a monitor measures CO must be taken into account when using the data in clinical management.

Ultra-high-density phase-change storage and memory.

Phase-change storage is widely used in optical information technologies (DVD, CD-ROM and so on), and recently it has also been considered for non-volatile memory applications. This work reports advances in thermal data recording of phase-change materials. Specifically, we show erasable thermal phase-change recording at a storage density of 3.3 Tb inch(-2), which is three orders of magnitude denser than that currently achievable with commercial optical storage technologies. We demonstrate the concept of a thin-film nanoheater to realize ultra-small heat spots with dimensions of less than 50 nm. Finally, we show in a proof-of-concept demonstration that an individual thin-film heater can write, erase and read the phase of these storage materials at competitive speeds. This work provides important stepping stones for a very-high-density storage or memory technology based on phase-change materials.

An Australian experience with the molecular adsorbents recirculating system (Mars).

The molecular adsorbents recirculating system (MARS) is a form of artificial extracorporeal liver support which has the potential to remove substantial quantities of albumin-bound toxins postulated to contribute to the pathogenesis of liver cell damage, hemodynamic instability and multi-organ failure in patients with acute liver failure and acute-on-chronic liver failure (AoCLF). We assessed the efficacy of MARS therapy in a cohort of patients with severe liver damage unresponsive to intensive medical therapy. MARS therapy was instituted late in the clinical course of six patients with severely impaired liver function refractory to intensive medical therapy, including four with AoCLF precipitated by sepsis and two with liver dysfunction due to sepsis in the absence of pre-existing chronic liver disease. Outcome measures included markers of hemodynamic stability, renal function, serum bilirubin and bile acid levels, arterial ammonia levels, the arterial ketone body (acetoacetate/beta-hydroxybutyrate) ratio, hepatic encephalopathy grade and the plasma disappearance rate of indocyanine green. The rates of discharge from the intensive care unit and in-hospital mortality were determined. Our findings suggest that MARS treatment might be associated with some clinical efficacy even in patients with advanced multi-organ dysfunction occurring in the setting of severe liver damage and in whom treatment is instituted late in the clinical course. However, the overall survival rate (1/6; 17%) was poor. More data obtained from larger cohorts of patients enrolled in randomized controlled studies will be required in order to identify categories of liver failure patients who might benefit most from MARS treatment and to ascertain the most appropriate timing of intervention.

Active control of slow light on a chip with photonic crystal waveguides.

It is known that light can be slowed down in dispersive materials near resonances. Dramatic reduction of the light group velocity-and even bringing light pulses to a complete halt-has been demonstrated recently in various atomic and solid state systems, where the material absorption is cancelled via quantum optical coherent effects. Exploitation of slow light phenomena has potential for applications ranging from all-optical storage to all-optical switching. Existing schemes, however, are restricted to the narrow frequency range of the material resonance, which limits the operation frequency, maximum data rate and storage capacity. Moreover, the implementation of external lasers, low pressures and/or low temperatures prevents miniaturization and hinders practical applications. Here we experimentally demonstrate an over 300-fold reduction of the group velocity on a silicon chip via an ultra-compact photonic integrated circuit using low-loss silicon photonic crystal waveguides that can support an optical mode with a submicrometre cross-section. In addition, we show fast (approximately 100 ns) and efficient (2 mW electric power) active control of the group velocity by localized heating of the photonic crystal waveguide with an integrated micro-heater.

Nitric-oxide-lowering effect of terlipressin in decompensated cirrhosis: comparison to the molecular adsorbent recirculating system and correlation with clinical status.

Systemic vasodilatation and arterial hypotension, refractory to adrenergic vasopressors, portend a poor prognosis in patients with decompensated cirrhosis. The production of large amounts of nitric oxide, consequent to endotoxin-induced tumour necrosis factor (TNF)-alpha-mediated upregulation of inducible nitric oxide synthase (iNOS), has been suggested to be central to this phenomenon. Terlipressin has recently been shown in an animal model of cirrhosis to suppress endotoxin-induced TNF-alpha-mediated upregulation of iNOS, thereby preventing overproduction of nitric oxide and restoring normal vascular tone. We present the first evidence that this effect of terlipressin may also occur clinically, in a patient with Child-Pugh class C cirrhosis, endotoxaemia, a raised circulating TNF-alpha concentration, and marked systemic vasodilatation with refractory arterial hypotension. Beneficial effects of terlipressin on circulating nitrate and nitrite concentrations, haemodynamic status, plasma renin levels and indocyanine green clearance were comparable to those of the molecular adsorbent recirculating system (MARS). Our findings suggest that terlipressin may be the vasopressor agent of choice in patients with decompensated cirrhosis and provide a rationale for combination terlipressin and MARS therapy when the therapeutic response to either treatment alone is suboptimal.

The effect of chronic pain on health related quality of life amongst intensive care survivors.

Intensive care unit (ICU) survivors report reductions in health-related quality of life (HR-QOL), whilst chronic pain is common in the general population. However, it is unknown whether there are associations between the experience of ICU and the incidence of chronic pain. A questionnaire--Pain Scale, Pain Self-Efficacy Questionnaire (PSEQ), Centre of Epidemiology Study Depression Scale (CES-D Scale) and the Short Form Health Survey (SF-36)--was sent to 99 consenting patients who had been in the ICU for >48 hours. Sixty-six and 52 questionnaires were returned at 1 and 6 months respectively. There was a general limitation in activities of daily living; younger ages (36-65 years) experienced a decease in work performance and other physical activities. Bodily pain increased, general health diminished, and engagements in social activities were severely affected. There was a decline in mental health for those 36-65 years of age. HR-QOL improved over time; 28% experienced chronic pain and had longer hospital length of stay (LOS), tended to have longer ICU LOS and were ventilated for longer. Those with chronic pain had significant reductions in physical function, bodily pain, general health and vitality. Ventilator hours and hospital LOS were associated with risk of chronic pain (OR 1.09, p=0.033 and OR 1.27, p=0.046). HR-QOL in ICU survivors declined, although there was a general improvement from 1-6 months. This decline in HR-QOL affected younger people (less than 65 years) more than older people. Chronic pain is a significant issue post ICU and is associated with poorer HR-QOL.

Memories of intensive care and experiences of survivors of a critical illness: an interview study.

Recovery from a critical illness can be a complex and protracted process. It is known that for some, health-related quality of life (HRQOL) does not return to pre-illness levels for many months, and in some disease processes this may be longer. This study was undertaken as part of a larger project examining the pain and health status of survivors of a critical illness. The aims of the qualitative aspect of the study were to examine the participants' memories of intensive care and hospitalisation at 6 months post-discharge, and to explore the impact of the critical illness experience on their recovery. Purposive sampling was used to enable rich descriptions of the experience of recovery from those patients best able to articulate their experiences. Three common themes were found with our six participants: recollections, responses, and comfort/discomfort. Recovery from their critical illness continued to affect the participants and carers, some profoundly so. Better integration of services and continued support is required for survivors of a critical illness up to and beyond 6 months.

Equipment review: the molecular adsorbents recirculating system (MARS).

The molecular adsorbents recirculating system (MARS) is a form of artificial liver support that has the potential to remove substantial quantities of albumin-bound toxins that have been postulated to contribute to the pathogenesis of liver cell damage, haemodynamic instability and multi-organ failure in patients with acute liver failure (ALF) and acute-on-chronic liver failure (AoCLF). These toxins include fatty acids, bile acids, tryptophan, bilirubin, aromatic amino acids and nitric oxide. Data from controlled clinical trials are limited so far. One of two studies performed on small numbers of patients with AoCLF suggest a survival benefit, but no controlled data are available in the ALF setting. Our preliminary experience with MARS therapy, instituted late in the clinical course of five patients with severely impaired liver function, including three with AoCLF precipitated by sepsis and two with liver dysfunction due to sepsis in the absence of pre-existing chronic liver disease, indicates some clinical efficacy. However, the overall survival rate (1 of 5; 20%) remained poor. More data obtained from larger cohorts of patients enrolled in randomised controlled studies will be required in both the AoCLF and ALF settings to identify categories of liver failure patients who might benefit most from MARS treatment, to ascertain the most appropriate timing of intervention and to determine the overall impact on outcome, including cost-effectiveness.

The use of activated protein C (drotrecogin alfa (activated)) in the treatment of severe sepsis.

Advances in intensive care have allowed many critically ill patients to survive their initial insult. These patients may later demonstrate multiple organ dysfunction and failure, the genesis of which appears to be the body's reaction to critical illness, manifested by an imbalance and failure of inflammatory and immune system homeostasis. The manifestation of multiple organ dysfunction in the critically ill has been termed multiple organ dysfunction syndrome (MODS). MODS mortality is high and remains a leading cause of death in intensive care units (ICUs). The understanding of the pathophysiology of severe sepsis and MODS has moved from a focus on inflammation to include an understanding of the associated anti-inflammatory responses. Loss of homeostasis can manifest as malignant inflammation or immune paralysis. Increased emphasis is emerging on the role of loss of immune homeostasis and disordered coagulation as a cause of organ injury and dysfunction. Treatment of severe sepsis is based upon aggressive resuscitation, source control and support for failing organs. Novel therapies directed at the modifying the inflammatory response have, up to now, not proven beneficial. However, a new agent, drotrecogin alfa (activated) has been shown, in a phase III randomised controlled trial, to be of benefit in the treatment of severe sepsis. This new agent affects both the inflammatory and coagulation dimensions of severe sepsis. The developing concepts of the pathophysiology of sepsis and the emergence of a new therapy increases the complexity of the already complex demands of providing nursing care for the patient with severe sepsis and MODS. This article reviews pathophysiological processes in sepsis, reviews clinical data on activated protein C and illustrates the utility of this therapy in a case study.