High efficiency particulate air filters and heat & moisture exchanger filters increase positive end-expiratory pressure in helmet continuous positive airway pressure: A bench-top study

BACKGROUND

Helmet continuous positive airway pressure (CPAP) has been widely used during the COVID-19 pandemic. Specific filters (i.e. High Efficiency Particulate Air filter: HEPA; Heat & Moisture Exchanger Filter: HMEF) were used to prevent Sars-CoV2 environmental dispersion and were connected to the CPAP helmet. However, HEPA and HMEF filters may act as resistors to expiratory gas flow and increase the levels of pressure within the hood.

METHODS

In a bench-top study, we investigated the levels of airway pressure generated by different HEPA and HMEF filters connected to the CPAP helmet in the absence of a Positive End Expiratory Pressure (PEEP) valve and with two levels of PEEP (5 and 10 cmH2O). All steps were performed using 3 increasing levels of gas flow (60, 80, 100 L/min).

RESULTS

The use of 8 different commercially available filters significantly increased the pressure within the hood of the CPAP helmet with or without the use of PEEP valves. On average, the increase of pressure above the set PEEP ranged from 3 cmH2O to 10 cmH2O across gas flow rates of 60 to 100 L/min. The measure of airway pressure was highly correlated between the laboratory pressure transducer and the Helmet manometer. Bias with 95% Confidence Interval of Bias between the devices was 0.7 (-2.06; 0.66) cmH2O.

CONCLUSIONS

The use of HEPA and HMEF filters placed before the PEEP valve at the expiratory port of the CPAP helmet significantly increase the levels of airway pressure compared to the set level of PEEP. The manometer can detect accurately the airway pressure in the presence of HEPA and HMEF filters in the helmet CPAP and its use should considered.

Helmet continuous positive airway pressure for patients' transport using a single oxygen cylinder: A bench study

BACKGROUND

Continuous positive airway pressure (CPAP) is frequently used to treat patients with acute respiratory failure in out-of-hospital settings. Compared to a facemask, the helmet has many advantages for the patient but requires a minimum gas flow of 60 L/min to avoid CO2 rebreathing. The aim of the present bench study was to evaluate the performance of four Venturi devices, connected to a single oxygen cylinder, in delivering helmet-CPAP with clinically relevant gas flow, fraction of inspired oxygen (FiO2), and positive end-expiratory pressure (PEEP) values.

METHODS

Three double-inlet Venturi systems (EasyVent, Ventuplus, Compact-HAR) were connected to full 5-L oxygen cylinders using a double flowmeter, and their oxygen requirements to reach different setups (flow 60-80 L/min; FiO2 0.4-0.5-0.6, PEEP 7.5-10-12.5 cmH2O) were tested. The fourth Venturi system (O2-MAX) was directly attached to the tank, and the flow and FiO2 delivered at preset FiO2 0.3 and 0.6 were recorded. The runtime of the cylinder was assessed.

RESULTS

EasyVent, Ventuplus, and O2-MAX were able to deliver helmet-CPAP with clinically useful setups when connected to a single oxygen cylinder, while Compact-HAR did not. The runtime of the cylinders ranged between 28 and 60 minutes according to the preset flow and FiO2. The delivered gas flow decreased slowly and linearly with the drop in cylinder pressure until its exhaustion.

CONCLUSIONS

Helmet-CPAP might be provided using portable Venturi systems connected to an oxygen cylinder, but not all of them are able to deliver it. The use of a double flowmeter allows delivery of both high flow and high FiO2 when double-inlet Venturi systems are used. Due to the flow drop observed during the cylinder consumption, a flow >60 L/min should be set when helmet-CPAP is started. Considering the flow drop phenomenon, the estimated duration of the tank runtime can be used with a margin of safety when planning patient transport.

Comparison of multiple definitions for ventilator-associated pneumonia in patients requiring mechanical ventilation for non-pulmonary conditions: preliminary data from PULMIVAP, an Italian multi-centre cohort study

OBJECTIVES

To compare intensivist-diagnosed ventilator-associated pneumonia (iVAP) with four established definitions, assessing their agreement in detecting new episodes.

METHODS

A multi-centric prospective study on pulmonary microbiota was carried out in patients requiring mechanical ventilation (MV). Data collected were used to compare hypothetical VAP onset according to iVAP with the study consensus criteria, the European Centre for Disease Control and Prevention definition, and two versions of the latter adjusted for leukocyte count and fever.

RESULTS

In our cohort of 186 adult patients, iVAPs were 36.6% (68/186, 95% confidence interval 30.0-44.0%), with an incidence rate of 4.64/100 patient-MV-days, and median MV-day at diagnosis of 6. Forty-seven percent of patients (87/186) were identified as VAP by at least one criterion, with a median MV-day at diagnosis of 5. Agreement between intensivist judgement (iVAP/no-iVAP) and the criteria was highest for the study consensus criteria (50/87, 57.4%), but still one-third of iVAP were not identified and 9% of patients were identified as VAP contrary to intensivist diagnosis. VAP proportion differed between criteria (25.2-30.1%).

CONCLUSIONS

Caution is needed when evaluating studies describing VAP incidence. Pre-agreed criteria and definitions that capture VAP's evolving nature provide greater consistency, but new clinically driven definitions are needed to align surveillance and diagnostic criteria with clinical practice.

Prone position for acute respiratory distress syndrome and the hazards of meta-analysis

BACKGROUND

Researchers have tried unsuccessfully for many years using randomized controlled trials to show the efficacy of prone ventilation in treating ARDS. These failed attempts were of use in designing the successful PROSEVA trial, published in 2013. However, the evidence provided by meta-analyses in support of prone ventilation for ARDS was too low to be conclusive. The present study shows that meta-analysis is indeed not the best approach for the assessment of evidence as to the efficacy of prone ventilation.

METHODS

We performed a cumulative meta-analysis to prove that only the PROSEVA trial, due to its strong protective effect, has substantially impacted on the outcome. We also replicated nine published meta-analyses including the PROSEVA trial. We performed leave-one-out analyses, removing one trial at a time from each meta-analysis, measuring p values for effect size, and also the Cochran's Q test for heterogeneity assessment. We represented these analyses in a scatter plot to identify outlier studies influencing heterogeneity or overall effect size. We used interaction tests to formally identify and evaluate differences with the PROSEVA trial.

RESULTS

The positive effect of the PROSEVA trial accounted for most of the heterogeneity and for the reduction of overall effect size in the meta-analyses. The interaction tests we conducted on the nine meta-analyses formally confirmed the difference in the effectiveness of prone ventilation between the PROSEVA trial the other studies.

CONCLUSIONS

The clinical lack of homogeneity between the PROSEVA trial design and the other studies should have discouraged the use of meta-analysis. Statistical considerations support this hypothesis, suggesting that the PROSEVA trial is an independent source of evidence.

A patient-specific approach for quantitative and automatic analysis of computed tomography images in lung disease: Application to COVID-19 patients

PURPOSE

Quantitative metrics in lung computed tomography (CT) images have been widely used, often without a clear connection with physiology. This work proposes a patient-independent model for the estimation of well-aerated volume of lungs in CT images (WAVE).

METHODS

A Gaussian fit, with mean (Mu.f) and width (Sigma.f) values, was applied to the lower CT histogram data points of the lung to provide the estimation of the well-aerated lung volume (WAVE.f). Independence from CT reconstruction parameters and respiratory cycle was analysed using healthy lung CT images and 4DCT acquisitions. The Gaussian metrics and first order radiomic features calculated for a third cohort of COVID-19 patients were compared with those relative to healthy lungs. Each lung was further segmented in 24 subregions and a new biomarker derived from Gaussian fit parameter Mu.f was proposed to represent the local density changes.

RESULTS

WAVE.f resulted independent from the respiratory motion in 80% of the cases. Differences of 1%, 2% and up to 14% resulted comparing a moderate iterative strength and FBP algorithm, 1 and 3 mm of slice thickness and different reconstruction kernel. Healthy subjects were significantly different from COVID-19 patients for all the metrics calculated. Graphical representation of the local biomarker provides spatial and quantitative information in a single 2D picture.

CONCLUSIONS

Unlike other metrics based on fixed histogram thresholds, this model is able to consider the inter- and intra-subject variability. In addition, it defines a local biomarker to quantify the severity of the disease, independently of the observer.

Charge Density Waves in YBa_{2}Cu_{3}O_{6.67} Probed by Resonant X-Ray Scattering under Uniaxial Compression

We report a comprehensive Cu L_{3}-edge resonant x-ray scattering (RXS) study of two- and three-dimensional (2D and 3D) incommensurate charge correlations in single crystals of the underdoped high-temperature superconductor YBa_{2}Cu_{3}O_{6.67} under uniaxial compression up to 1% along the two inequivalent Cu─O─Cu bond directions (a and b) in the CuO_{2} planes. We confirm the strong in-plane anisotropy of the 2D charge correlations and observe their symmetric response to pressure: pressure along a enhances correlations along b, and vice versa. Our results imply that the underlying order parameter is uniaxial. In contrast, 3D long-range charge order is only observed along b in response to compression along a. Spectroscopic RXS measurements show that the 3D charge order resides exclusively in the CuO_{2} planes and may thus be generic to the cuprates. We discuss implications of these results for models of electronic nematicity and for the interplay between charge order and superconductivity.

Dynamical charge density fluctuations pervading the phase diagram of a Cu-based high-T c superconductor

Charge density modulations have been observed in all families of high-critical temperature (T _c) superconducting cuprates. Although they are consistently found in the underdoped region of the phase diagram and at relatively low temperatures, it is still unclear to what extent they influence the unusual properties of these systems. Using resonant x-ray scattering, we carefully determined the temperature dependence of charge density modulations in YBa₂Cu₃O_7-δ and Nd_{1+ x} Ba_{2- x} Cu₃O_7-δ for several doping levels. We isolated short-range dynamical charge density fluctuations in addition to the previously known quasi-critical charge density waves. They persist up to well above the pseudogap temperature T*, are characterized by energies of a few milli-electron volts, and pervade a large area of the phase diagram.

Three-dimensional collective charge excitations in electron-doped copper oxide superconductors

High-temperature copper oxide superconductors consist of stacked CuO₂ planes, with electronic band structures and magnetic excitations that are primarily two-dimensional^1,2, but with superconducting coherence that is three-dimensional. This dichotomy highlights the importance of out-of-plane charge dynamics, which has been found to be incoherent in the normal state^3,4 within the limited range of momenta accessible by optics. Here we use resonant inelastic X-ray scattering to explore the charge dynamics across all three dimensions of the Brillouin zone. Polarization analysis of recently discovered collective excitations (modes) in electron-doped copper oxides^5-7 reveals their charge origin, that is, without mixing with magnetic components^5-7. The excitations disperse along both the in-plane and out-of-plane directions, revealing its three-dimensional nature. The periodicity of the out-of-plane dispersion corresponds to the distance between neighbouring CuO₂ planes rather than to the crystallographic c-axis lattice constant, suggesting that the interplane Coulomb interaction is responsible for the coherent out-of-plane charge dynamics. The observed properties are hallmarks of the long-sought 'acoustic plasmon', which is a branch of distinct charge collective modes predicted for layered systems^8-12 and argued to play a substantial part in mediating high-temperature superconductivity^10-12.

Re-entrant charge order in overdoped (Bi,Pb)2.12Sr1.88CuO6+δ outside the pseudogap regime

In the underdoped regime, the cuprate high-temperature superconductors exhibit a host of unusual collective phenomena, including unconventional spin and charge density modulations, Fermi surface reconstructions, and a pseudogap in various physical observables. Conversely, overdoped cuprates are generally regarded as conventional Fermi liquids possessing no collective electronic order. In partial contradiction to this widely held picture, we report resonant X-ray scattering measurements revealing incommensurate charge order reflections for overdoped (Bi,Pb)_2.12Sr_1.88CuO_6+δ (Bi2201), with correlation lengths of 40-60 lattice units, that persist up to temperatures of at least 250 K. The value of the charge order wavevector decreases with doping, in line with the extrapolation of the trend previously observed in underdoped Bi2201. In overdoped materials, however, charge order coexists with a single, unreconstructed Fermi surface without nesting or pseudogap features. The discovery of re-entrant charge order in Bi2201 thus calls for investigations in other cuprate families and for a reconsideration of theories that posit an essential relationship between these phenomena.

Small Pore Size Microporous Membrane Oxygenator Reduces Plasma Leakage during Prolonged Extracorporeal Circulation: A Case Report

Plasma leakage has been regarded as the main technical problem during prolonged extracorporeal circulation (ECC) with microporous membrane oxygenators (MMOs). We report the case of a 15 year old male who underwent long term ECC for ARDS and in whom, by using new MMOs with reduced pore size, we were able to achieve prolonged artificial gas exchange efficiency with minimal plasma leakage. We conclude that reduced pore size MMOs might represent a valuable technical advance in extracorporeal oxygenation therapy.

Percutaneous Bridge to Heart Transplantation by Venoarterial ECMO and Transaortic Left Ventricular Venting

We report a case in which life support for cardiogenic shock was achieved by a nonpulsatile venoarterial bypass, and left ventricular decompression was obtained by a catheter placed percutaneously through the aortic valve into the left ventricle. The blood drained from the left ventricle was pumped into the femoral artery. The normalization of left heart filling pressures allowed the resolution of pulmonary edema, and the patient underwent a successful heart transplantation following 7 days of mechanical cardiocirculatory support.

CT and Chest Radiography in the Evaluation of Adult Respiratory Distress Syndrome

CT is seldom employed in adult respiratory distress syndrome (ARDS), mostly due to problems in transporting and monitoring these severely ill patients. We reviewed the findings of 74 ARDS patients who underwent chest CT. Lung opacities were bilateral in almost all patients and dependent in most cases (86%). The opacities were patchy (42%), homogeneous (23%), ground glass (8%) or mixed (27%). Opacities prevailed in basal regions (68%) compared to hilar and apical ones. Air bronchograms were frequently seen in areas of consolidation (89%). In contrast with previous reports, pleural effusion was a frequent finding (50%) that did not worsen prognosis. Often loculated pneumothorax (32%) was mostly anteromedial. Ineffective position of thoracostomy tubes was detected at CT in 13/20 patients. Pulmonary air cysts (30%>), always multiple and mostly bilateral, were associated with a higher mortality (55%) than that of the whole study group (35%). Compared to chest radiographs, CT often yielded additional information (66%), with direct influence on patient treatment in 22% of cases.

Rescue therapy with polymyxin B hemoperfusion in high-dose vasopressor therapy refractory septic shock

BACKGROUND

Refractory septic shock (RSS) requiring major vasopressor support is associated with high mortality, especially in Gram-negative infections. The study aim was to describe hemodynamics, organ failure, and clinical outcomes in high-dose vasopressor therapy (HDVT) RSS patients treated with Polymyxin B hemoperfusion (PMX-HP) as rescue therapy.

METHODS

We retrospectively analyzed 52 patients, unresponsive to conventional therapy, treated with two sessions of PMX-HP requiring HDVT (norepinephrine and/or epinephrine requirement (NEP+EP) ≥ 0.5 µg/kg/min), ≥ 2 organ failures, and suspected/confirmed Gram-negative infection from any source.

RESULTS

At baseline, mean arterial pressure (MAP) was 80 ± 13 mmHg and NEP + EP requirement was 1.11 ± 0.56 µg/kg/min. After two PMX-HP sessions, at 72 h, MAP significantly increased and NEP + EP requirement decreased respectively by 12% and 76%. Pulmonary and renal function also improved significantly. Thirty patients (58%) showed a ≥ 50% reduction in NEP + EP dose within only 24 h after the first PMX-HP session (early responders), and 22 did not or died from irreversible shock in the same time frame (early non-responders). The 30-day hospital mortality was 29%; it was 16% in early responders and 45% in early non-responders. On multivariate analysis, SAPS II score, vasopressin, and central venous pressure significantly affected 30-day hospital mortality.

CONCLUSION

This is the first study describing the use of PMX-HP as a rescue therapy in RSS patients with HDVT and MOF. Our results suggest a possible role for PMX-HP in improving hemodynamics, organ function, and mortality in RSS, with a 30-day survival of up to 70%.

Intraperitoneal nebulization of ropivacaine for pain control after laparoscopic cholecystectomy: a double-blind, randomized, placebo-controlled trial

BACKGROUND

Intraperitoneal local anaesthetic nebulization is a relatively novel approach to pain management after laparoscopic surgery. This randomized, double-blind, placebo-controlled trial evaluated the effects of intraperitoneal ropivacaine nebulization on pain control after laparoscopic cholecystectomy.

METHODS

Patients undergoing laparoscopic cholecystectomy were randomized to receive intraperitoneal nebulization of ropivacaine 1% (3 ml) before surgical dissection and normal saline 3 ml at the end of surgery (preoperative nebulization group); intraperitoneal nebulization of normal saline 3 ml before surgical dissection and ropivacaine 1% (3 ml) at the end of surgery (postoperative nebulization group); or intraperitoneal nebulization of normal saline 3 ml before surgical dissection and at the end of surgery (placebo group). Intraperitoneal nebulization of ropivacaine or saline was performed using the Aeroneb Pro(®) device. Anaesthetic and surgical techniques were standardized. The degree of pain on deep breath or movement, incidence of shoulder pain, morphine consumption, and postoperative nausea and vomiting were collected in the post-anaesthesia care unit and at 6, 24, and 48 h after surgery.

RESULTS

Compared with placebo, ropivacaine nebulization significantly reduced postoperative pain (-33%; Cohen's d 0.64), referred shoulder pain (absolute reduction -98%), morphine requirements (-41% to -56% Cohen's d 1.16), and time to unassisted walking (up to -44% Cohen's d 0.9) (P<0.01). There were no differences in pain scores between ropivacaine nebulization groups.

CONCLUSIONS

Ropivacaine nebulization before or after surgery reduced postoperative pain and referred shoulder pain after laparoscopic cholecystectomy. Furthermore, ropivacaine nebulization reduced morphine requirements and allowed earlier mobility.

Sigh improves gas exchange and respiratory mechanics in children undergoing pressure support after major surgery

BACKGROUND

Children undergoing major surgery can develop lung de-recruitment and gas exchange impairment in the postoperative period. The aim of this study was to assess the effect of periodic sigh breaths (Sighs) during pressure support ventilation (PSV) on gas exchange and respiratory pattern in children after major surgery.

METHODS

Twenty children were enrolled and received PSV alone and with Sighs in a randomized order. Sighs were administered once per minute by adding to baseline pressure support a pressure controlled breath set at 30 cm H2O of peak airway pressure. At the end of each study period air flow, pressure traces, and compliance of respiratory system, together with hemodynamic parameters and venous and arterial blood gas tensions, were recorded.

RESULTS

PaO2/FiO2 improved from baseline to Sigh group (312.6 ± 137.4 vs. 394.2 ± 127.0; P<0.01) and PaCO2 decreased from baseline to Sigh group (39.3 ± 3.3 vs. 34.3 ± 4.6 mmHg; P<0.001), without any change in minute expiratory volume. Indexed to body weight compliance of respiratory system improved from baseline to Sigh group (0.85 ± 0.35 vs. 1.01 ± 0.30 mL/kg/cm H2O; P<0.01). There were no significant differences between the two groups for the hemodynamic parameters.

CONCLUSION

The addition of one Sigh per minute during PSV in the post-operative period of children that underwent major surgery improved gas exchange and decreased respiratory drive without producing major short-term complications. Further long-term studies are necessary to evaluate the efficacy and safety of Sigh in pediatric patients.

Management of acute respiratory complications from influenza A (H1N1) infection: experience of a tertiary-level Intensive Care Unit

BACKGROUND

The novel influenza A (H1N1) pandemic was associated with an epidemic of critical illness.

METHODS

We describe the clinical profiles of critically ill patients with severe complications due to microbiologically confirmed pandemic influenza A (H1N1) infection admitted to a medical ICU in Monza, Italy, over a 6-month period.

RESULTS

From August 2009 to January 2010, 19 patients (13 adults and 6 children) required ICU admission. Nine subjects were referred to our hospital from other ICUs. In all patients, with the exception of a case of severe septic shock, the cause of ICU admission was acute respiratory failure. Other nonpulmonary organ failures were common. A trial of non-invasive ventilation was attempted in 13 cases and was successful in four of them. The majority of the patients required invasive mechanical ventilation. In the 7 most severely hypoxemic patients, we applied veno-venous ECLS, with a very high rate of success. The median ICU stay was 9 days (range 1-78 days). Sixteen out of 19 (84%) patients survived.

CONCLUSION

In the majority of our patients, critical illness caused by pandemic influenza A (H1N1) was associated with severe hypoxemia, multiple organ failure, requirement for mechanical ventilation and frequent use of rescue therapies and ECLS support.

Early detection of the graft failure after pediatric liver transplantation: a Bergamo experience

BACKGROUND

Effective indicators of the early graft failure after pediatric liver transplantation are currently a crucial question. The aim of this study was to analyze retrospectively laboratory parameters that may help anticipate an early graft loss (GL).

METHODS

The 131 pediatric liver transplantations, performed in our hospital from January 2002 to December 2005, were reviewed. Post-operative laboratory parameters, collected in the first 36 h of the Paediatric Intensive Care Unit (PICU) stay, were analyzed for children with both graft survival and GL. Receiver operating characteristics analysis was used to identify the optimal cut-off for the laboratory parameters. Multivariate logistic regression analysis was used to calculate the adjusted risk of GL for the prognostic parameters identified.

RESULTS

The mean age at transplant was 1.1 years. The two groups were comparable for all recipient and donor variables considered. Children with GL showed significantly higher levels of ammonia and transaminase at the admission to the PICU and higher levels of prothrombin time, creatinine, lactate and a lower level of platelets at the 36 h of PICU. The laboratory parameters over the cut-off value by the multivariate logistic regression identified all early thromboses earlier than Doppler ultrasound.

CONCLUSIONS

This study suggests that routine blood tests may help to anticipate an early loss of liver grafts in children after transplantation and may improve our diagnostic investigation in the case of thrombosis suspicion. Further validation by a prospective study is needed to carefully assess the sensitivity and specificity of the identified criteria.

Etiology of respiratory failure is related to mortality in critically ill patients affected by a hematological malignancy: a retrospective study

AIM

The outcomes of patients affected by hematologic malignancies (HM) admitted to Intensive Care Units (ICUs) because of life-threatening complications are still considered to be poor. The aim of this study was to assess the incidence and impact of cardiac dysfunction on the outcome of these patients.

METHODS

We retrospectively reviewed the records of the 48 patients (both adult and pediatric) with HM admitted in our ICU over the last four years, collecting data on admission diagnosis, type of HM, laboratory values and organ failure.

RESULTS

All patients were admitted with respiratory failure. The overall mortality rate was 50% and the mortality rates were similar among patients with different types of HM. Septic shock and multiple organ failure were the leading causes of death. The overall incidence of cardiac dysfunction was high (31%). Interestingly, the ICU mortality of this subgroup was 27%, while the mortality of the rest of the population was 61% (p<0.05).

CONCLUSIONS

ICU patients with HM have high mortality. Respiratory failure caused by cardiac dysfunction seems to be associated with a lower risk of death.

Which drugs for the control of fever in critical patients

It has been estimated that nosocomial fever occurs in approximately one-third of hospitalized patients. The incidence is even higher in critically-ill patients in whom both infectious and noninfectious etiologies of fever are common. Polypeptide cytokines (endogenous pyrogens) such as interleukin-1b (IL-1b), tumor necrosis factor (TNF) and interleukin-6 (IL-6) act directly on the hypothalamus to effect a fever response by promoting an increase in heat generation and a decrease in heat loss. There is widespread acceptance that in most if not all critically ill neurologic patients fever should be treated but still it is not clear if fever per se in nonneurologic critically ill patients should be treated too. We review physical and pharmacological methods presently utilized to treat fever in critically ill patients.

Can routine surveillance samples from tracheal aspirate predict bacterial flora in cases of ventilator-associated pneumonia?

AIM

The aim of this study was to investigate the hypothesis that periodical sampling of the tracheo-bronchial tree in the absence of clinical suspicion of pneumonia is useful to identify bacteria responsible for subsequent late ventilator associated pneumonia (VAP). This was a retrospective observational human study carried out in two medical-surgical intensive care units of two different hospitals. From January 1999 to December 2000, 559 patients, who received invasive respiratory support for more than 48 hours, were screened.

METHODS

Tracheal aspiration (TA) was performed once or twice weekly in all mechanically ventilated patients. The microbiological findings from TA surveillance cultures done in the eight days before suspicion of VAP were compared to those isolated from the positive diagnostic samples done for late onset VAP (after more than four days of mechanical ventilation). The sensitivity, specificity, and positive/negative predictive values of the ability of the surveillance sample to anticipate the VAP pathogen were calculated.

RESULTS

Among the microorganisms isolated from TA, 68% were retrieved from diagnostic samples. All VAP pathogens previously isolated were from 43% of the TA samples. If TA was collected 2-4 days before the clinical diagnosis of VAP, pathogens were detected in 58% of samples. In contrast, only 27% were collected more than four days earlier (P<0.05). The positive predictive values for Pseudomonas aeruginosa and methicillin resistant Staphylococcus aureus from routine TA samples were 92% and 90%, respectively. The negative predictive values for Pseudomonas aeruginosa and methicillin resistant Staphylococcus aureus from routine TA samples were 75% and 89%, respectively.

CONCLUSIONS

TA cultures in ventilated patients may help to predict pathogens. Early detection may lead to earlier treatment in long term ventilated patients when VAP is suspected.

Correlation between pre-operative metabolic syndrome and persistent blood glucose elevation during cardiac surgery in non-diabetic patients

BACKGROUND

Cardiopulmonary-bypass (CPB) induces hyperglycemia. There is growing evidence that perioperative maintenance of blood glucose within the physiological range improves patients' outcome. Nevertheless, perioperative normoglycemia is often difficult to achieve during surgery with CPB and the response to insulin infusion is characterized by a considerable variability. The aim of this study was to determine to what extent the presence of pre-operative metabolic syndrome (MS) influences the blood glucose and insulin response during cardiac surgery.

METHODS

Forty-five patients scheduled for elective cardiac surgery were screened for the presence of MS according to the International Diabetes Federation definition. Patients were then assigned to two groups: those with metabolic syndrome (MSP) and those without (control). During surgery, blood glucose levels were measured in all patients and hyperglycemia was treated with a standard protocol of continuous insulin infusion.

RESULTS

The mean blood glucose levels during CPB increased only in the MSP group (P<0.001). Mean blood glucose in control patients did not increase during CPB (P=0.4). Patients with MS received 13.3+/-8.4 IU of insulin during CPB, while the control group did not require insulin treatment (P<0.001). Forty percent of patients in the control group and 100% of those in the MSP group developed post-operative insulin resistance. C-reactive protein was higher in the MSP group before, during and at 48 h after surgery.

CONCLUSIONS

The mean blood glucose levels during CPB increased only in patients with MS, while they remained unchanged in patients in the control group.

Risk factors for treatment failure in patients with severe acute cardiogenic pulmonary oedema

Intubation is necessary in 7 to 20% of patients with severe acute cardiogenic pulmonary oedema despite optimal treatment. This study evaluated the usefulness of parameters largely available in clinical practice to predict the need for intubation in a population of acute cardiogenic pulmonary oedema patients treated with medical therapy and continuous positive airway pressure. The present retrospective cohort study involved 142 patients with severe acute cardiogenic pulmonary oedema who were admitted to coronary care or the intensive care unit of a university hospital and were treated by an in-hospital protocol. Physiological measurements and blood gas samples were evaluated at 'baseline' (just after admission), 'early' (one to three hours after beginning treatment) and 'late' (eight to 10 hours after beginning treatment). Twenty-two patients (15.5%) required intubation. A systolic blood pressure at admission lower than 140 mmHg was significantly associated with a higher risk for intubation, while hypercapnic patients or those with a reduced left ventricular ejection fraction at admission did not show a worse prognosis. A simple score based on largely available parameters (1 point for each: age >78 years, systolic blood pressure <140 mmHg at admission, arterial blood gas acidosis and heart rate >95 bpm at early time) is proposed. The rate of intubation according to this score ranged from 0% (score of 0) to 90% (score of 3). Our study found that simple parameters available in clinical practice are significantly associated with the need for intubation in acute cardiogenic pulmonary oedema patients treated with continuous positive airway pressure and medical therapy. A simple score to evaluate the need for endotracheal intubation is proposed.

Randomized controlled trial of duration of analgesia following intravenous or rectal acetaminophen after adenotonsillectomy in children

BACKGROUND

Doses of acetaminophen 40 mg kg(-1) rectally and 15 mg kg(-1) i.v. produce similar effect-site concentrations. However, the clinical effectiveness of these routes has not been compared. The aim of this study was to compare duration and efficacy of analgesia in children following adenotonsillectomy after acetaminophen either 40 mg kg(-1) rectally or 15 mg kg(-1) i.v.

METHODS

Fifty children aged between 2 and 5 yr were recruited. They received a standardized anaesthetic, including 2 microg kg(-1) of fentanyl. Children were randomized to receive either rectal or i.v. acetaminophen. Postoperative pain was assessed regularly with the Children and Infants Postoperative Pain Scale score and rescue analgesia provided if scores were 4 or greater. The primary outcome measure was time to first analgesia. Results were plotted with a Kaplan-Meier analysis and median time to rescue analgesia compared between the groups.

RESULTS

The protocol was successfully completed in 46 children. Forty-five children required rescue medication. The time to first rescue analgesia was longer in children receiving rectal acetaminophen (median 10 h, inter-quartile range 9-11 h) compared with those receiving i.v. acetaminophen (7, 6-10 h) with a P-value of 0.01 by log-rank test for equality in survivor function. Few children in either group required rescue analgesia within the first 6 h with differences between the groups being most prominent in the period from 6 to 10 h.

CONCLUSIONS

Rectal acetaminophen 40 mg kg(-1) provides longer analgesia for moderately painful procedures when compared with 15 mg kg(-1) acetaminophen i.v.

Epidural analgesia in children: planning, organization and development of a new program

BACKGROUND

The goal of the present work is to describe the development and results of the pediatric epidural analgesia program at the ''Hospital Nacional de Pediatria Prof. Dr. J. P. Garrahan'' in Argentina.

METHODS

Patients with thoracotomy, abdominal surgery, osteotomy, amputations or severe trauma were included in the program. The program provided training to the entire staff, control and record of pain treatment and its consequences, 24 h a day availability of anesthesia staff and standard polices and procedures.

RESULTS

One hundred fifty children under 16 years of age (median age 11 years, median weight 35 kg) were included in the program during the first 18 months. The median of maximum pain reported during activity was 1 (interquartile range 1 to 4 points) using the Visual Analogue Scale (VAS) or Objective Pain Scale (OPS). Eighty seven children (CI 95% 50% to 67%) presented with postoperative nausea and vomiting, urinary retention, itching, motor blockade or sedation. No patient presented with respiratory depression, hypotension, local anaesthetic toxicity, epidural catheter related infection or death during the program evaluation. The postoperative care program enabled a 98-day reduction in treatment in the intensive care unit.

CONCLUSION

The safe use of pediatric epidural analgesia in general wards may require the careful selection of patients, systematic assessment by trained personnel, training of medical and nursing personnel, clear distribution of responsibilities, use of printed indications, systematic record of pain, sedation and complications, information and education of patients and parents, supply of systems for airway resuscitation and management and continuous quality control and revision of the methods.

Bupivacaine caudal epidural anesthesia: assessing the effect of general anesthetic technique on block onset

BACKGROUND

The primary objective of this prospective, randomized trial was to compare the effect of propofol and sevoflurane on effectiveness of regional anesthesia. As a secondary objective, we aimed at evaluating the influence of age on neuraxial block profile.

METHODS

One hundred and thirteen healthy children aged <10 years, scheduled for general or urological surgical procedures were randomly allocated to receive either propofol or sevoflurane induction and maintenance. Children received caudal or lumbar epidural block depending on their weight and expected surgery. Time to onset of surgical anesthesia, intraoperative analgesic effectiveness, residual motor blockade, postoperative pain, and adverse effects were evaluated. To assess the influence of age on these measures children were further divided into three age groups: 0-24, 25-60 and >60 months.

RESULTS

The mean time to onset of surgical anesthesia was significantly shorter in the sevoflurane group than the propofol group (3.1 vs 4.7 min, P < 0.01), independent of the type of regional technique employed. Distress on arousal in recovery was increased in children receiving sevoflurane (P = 0.03). There was no significant difference in residual motor blockade between the groups but children between 0 and 24 months receiving sevoflurane had a higher incidence of residual motor blockade 3 h after local anesthetic injection (P = 0.01).

CONCLUSIONS

This study has demonstrated that general anesthesia with sevoflurane decreases the time to onset of surgical anesthesia relative to propofol anesthesia. This effect was most marked when sevoflurane anesthesia preceded caudal epidural blockade. The basis for this effect is most likely to be related to differential binding of the two anesthetic agents to receptors in the spinal cord that mediate immobility in response to surgical stimuli.

Interactions between general and regional anesthesia

Neuraxial blockade is commonly used to abolish sensations elicited by noxious stimuli during surgical procedures. Proven advantages of combined anesthesia include early recovery from general anesthesia and postoperative analgesia, together with likely decreases in blood loss, cardiac dysrhythmias, or ischemic events and postoperative deep vein thrombosis. The side effects of the technique are related to the dose or site of local anesthetic administration and to light general anesthesia, which can result in awareness during surgery. Varying degrees of synergistic interactions have been reported among the drugs used to achieve the anesthetic state. Spinal anaesthesia appears to have sedative effects, and local anesthetics used for neuraxial blockade have been found to reduce the induction and maintenance dosage of midazolam, thiopental, propofol and inhaled anesthetics. The growing interest in combining local and general anesthesia has led to studies investigating possible interactions between general anesthesia and local anesthetics administered via spinal or epidural routes. Neuraxial blockade reduces sedative and anesthetic requirements by decreasing ascending sensory input into the brain. This has important clinical implications, as anesthetists should expect to reduce anesthetic and sedative drug doses during neuraxial blockade, unless the blockade involves lower dermatomes alone. Clinical practice of anesthesia is a polypharmacy, wherein the anesthetic state is the net result of the action of different drugs and their interaction in the presence of a surgical stimulus.

Hemodynamic monitoring in ICU

Oxygen supply to all tissues is possible only in a condition of adequate blood circulation. Oxygen demand is the driving force that is responsive of hemodynamic adjustment. The human body acts on four modulators (intravascular volume, inotropy, vasoactivity, chrono-tropy) in order to adjust the hemodynamic state. Hemodynamic monitoring consists of techniques able to assess the hemodynamic status and to understand the mechanism of patient decompensation; its goal is to maintain adequate tissue perfusion through appropriate therapeutic interventions. An early diagnosis of hemodynamic alteration is crucial for an early treatment; several reports have explored the effectiveness of hemodynamic manipulations and results are conflicting: too many variables can, in fact, modify the results: timing and lenght of the treatment, drugs used, etc. However, at least, in some specific settings, as sepsis, early intervention has a positive impact on mortality. In this presentation it will be briefly analyzed the most common parameters used in the ICU. Arterial pressure, central venous pressure, pulmonary artery catheter derived parameters, SvO2 and their relation with organ perfusion are considered and positive and negative aspects of this type of monitoring is reviewed. Starting from these considerations we would like to underline the importance of understanding the physiological basis of monitoring and the correct interpretation of data in order to have improvement on patient outcome.

[Pharmacotherapy of sepsis]

Despite an increasingly understanding of the pathogenetic mechanisms of sepsis, its mortality remains extremely high, caused mainly by hemodynamic impairment-related alterations frequently present in severe sepsis. Currently, treatment of sepsis is based on hemodynamic support, antibiotic therapy, surgical excision of infectious foci and immunomodulatory therapy. In fact, a massive host inflammatory infection response has recently emerged to substantially contribute to the development of septic shock and multiple organ dysfunction. Many clinical trials on various pharmacological agents have been conducted: glucocorticoids, nonsteroidal anti-inflammatory drugs (NSAIDs), antithrombin III (AT III), anti-endotoxin monoclonal antibodies, nitric oxide inhibitors, interleukin-1 receptor antagonist, anti-tumor necrosis factor (TNF) antibodies. Apart from some likely favourable findings connected to low doses of glucocorticoids, most studies yielded disappointing results. Nevertheless, the use of recombinant human activated protein C (drotrecogin-alpha) has recently proven to have a mortality reduction effect particularly in patients with severe sepsis and dysfunction of at least two organs. Furthermore, the early treatment of hemodynamic instability with volume expanders and vasopressors (early goal-directed therapy), and a strict glycemic control represent important measures in order to significantly reduce mortality from severe sepsis and septic shock, and are fundamental guidelines recommended by most scientific societies (Surviving Sepsis Campaign).

Postoperative Sedation and Analgesia After Pediatric Liver Transplantation

The goal of sedation in the pediatric intensive care unit (PICU) is to produce a calm and comfortable child, free from pain and discomfort. Children receiving liver transplantation need analgesics to control pain from surgical incisions, drains, vascular access, or endotracheal suctioning. Sedatives are used to facilitate the delivery of nursing care, to prevent self-extubation, and to facilitate mechanical ventilation. Optimal sedation produces a state in which the patient is somnolent, responsive to the environment but untroubled by it, and with no excessive movements. A common problem in the PICU is the fluctuation in the delivery of sedatives and analgesics depending on the health care providers and on a breakdown in communication between physicians and nurses to define end points for pharmacological therapy. This variability more often leads to oversedation rather than undersedation. Oversedation delays extubation, promotes ventilator-associated pneumonia, and increases the risk of reintubation. The use of written sedation policies to guide practice at the bedside reduces the length of time for which patients require mechanical ventilation and the length of PICU stay. Protocols for drug administration practices increase patient safety during mechanical ventilation, promote nursing autonomy, and facilitate communication between nurses and physicians as well as between nurses.

Central blocks with levobupivacaina in children

Regional anesthesia has become a routine practice in paediatric anesthesia and local anaesthetics are now widely used in infants and children. Although local anaesthetics are generally quite safe and effective, they may produce systemic toxic reactions affecting the heart and brain. Because postoperative analgesia is often the primary justification for regional anesthesia in infants and children, bupivacaine, a long-acting local anaesthetic, is the most commonly used local anaesthetic for paediatric regional anesthesia. Levobupiva-caine has been used in children by caudal injection, by lumbar epidural route for anesthesia during operation, by continuous epidural infusion for pain control after operation and for spinal anesthesia. Levobupivacaine had shown comparable clinical profiles to that of bupivacaine but produced lower incidence of residual motor blockade. Efforts to minimize the risk of complications during caudal anesthesia must be directed towards measures that reduce accidental intravenous and intraosseous injections, reduce the total amount of local anaesthetic used and use drugs with lower toxic potential. In patients under general anesthesia, when using a large amount of local anaesthetic, in case of accidental intravenous infusion, patients receiving levobupivacaine may tolerate larger doses before manifestation of toxicity compared with those receiving bupivacaine. There are clinical situations including prolonged local anaesthetic infusions, use in neonates or small babies, and caudal block, where replacement of bupivacaine with levobupivacaine appears to be safer.

Randomized, double-blind, phase III, controlled trial comparing levobupivacaine 0.25%, ropivacaine 0.25% and bupivacaine 0.25% by the caudal route in children

BACKGROUND

The rationale for replacing racemic bupivacaine with the s-enantiomers levobupivacaine and ropivacaine is to provide a wider margin of safety with the same analgesic efficacy and less postoperative motor block. In a randomized, double-blind, phase III, controlled trial we compared the caudal administration of levobupivacaine 0.25% and ropivacaine 0.25% with bupivacaine 0.25% in children.

METHODS

Ninety-nine ASA I-II children less than 10 yr old scheduled for elective sub-umbilical surgery were randomized to receive caudal block with bupivacaine 0.25%, ropivacaine 0.25% or levobupivacaine 0.25%. The primary outcome of the study was the clinical efficacy of the caudal block during the operation. Secondary outcome measures were analgesic onset time, pain relief after the operation and residual motor blockade.

RESULTS

The proportion of children with effective analgesia during the operation was similar among groups. There were no significant differences in the analgesic onset time of the caudal block. Bupivacaine produced a significant incidence of residual motor block compared with levobupivacaine or ropivacaine at wake-up (P<0.01). There were no significant differences in the number of patients receiving rescue analgesia after surgery. However, analgesic block lasted significantly longer in patients receiving bupivacaine (P=0.03).

CONCLUSION

During sub-umbilical surgery, caudal levobupivacaine, ropivacaine and bupivacaine provided comparable analgesic efficacy. Bupivacaine produced a higher incidence of residual motor blockade and a longer analgesic block than ropivacaine and levobupivacaine.

[Identification of the patient with sepsis]

Sepsis may be defined as a clinical syndrome caused by an organism's response to infection. The complex alterations triggered by the infection include inflammation and systemic coagulopathy in the absence of effective fibrinolysis. Possible manifestations vary in entity and severity, ranging from systemic inflammatory response syndrome (SIRS) to septic shock and multiorgan dysfunction syndrome (MODS). The nurse can play a fundamental role in the timely recognition of SIRS and in the early identification of the onset of signs of organ damage. In this way, an additional aid to establishing diagnosis can be provided and targeted treatment instituted. Following a brief presentation of the pathophysiology and epidemiology of sepsis, the manifestations and attendant risks are described, the most appropriate monitoring methods and the main nursing tasks in treating sepsis are discussed. We present the results of our experience in identifying patients with sepsis through the application of selection criteria adopted from clinical studies on the use of activated protein C.

Neuropathic pain in children

The International Association for the Study of Pain (IASP) defines neuropathic pain as being caused by a lesion or dysfunction of the nervous system. Characteristics that would define neuropathic pain and differentiate it from other types of pain include: pain and sensory symptoms that persist beyond the healing period; presence, in variable degree, of neurological sensory signs manifesting as negative and positive sensory phenomena; presence, in variable degree, of other neurological signs, including motor, manifesting as negative and positive motor phenomena or autonomic signs. Many of the conditions causing neuropathic pain in adults are rare in children, but some forms of neuropathic pain do affect children and adolescents as complex regional pain syndrome or phantom limb pain. Treatment strategies that have demonstrated to be efficacious in adults have been extrapolated to be used in children, including medications, nerve blocks, physical therapy, and behavioral medicine. A multidisciplinary program that combines all of these approaches provides the best chance of relief.