Acute lung injury in paediatric intensive care: course and outcome

Introduction: Acute lung injury (ALI) and acute respiratory distress syndrome (ARDS) carry a high morbidity and mortality (10-90%). ALI is characterised by non-cardiogenic pulmonary oedema and refractory hypoxaemia of multifactorial aetiology [1]. There is limited data about outcome particularly in children. Methods This retrospective cohort study of 85 randomly selected patients with respiratory failure recruited from a prospectively collected database represents 7.1% of 1187 admissions. They include those treated with High Frequency Oscillation Ventilation (HFOV). The patients were admitted between 1 November 1998 and 31 October 2000. Results: Of the 85, 49 developed acute lung injury and 47 had ARDS. There were 26 males and 23 females with a median age and weight of 7.7 months (range 1 day-12.8 years) and 8 kg (range 0.8-40 kg). There were 7 deaths giving a crude mortality of 14.3%, all of which fulfilled the Consensus I [1] criteria for ARDS. Pulmonary occlusion pressures were not routinely measured. The A-a gradient and PaO2/FiO2 ratio (median + [95% CI]) were 37.46 [31.82-43.1] kPa and 19.12 [15.26-22.98] kPa respectively. The non-survivors had a significantly lower PaO2/FiO2 ratio (13 [6.07-19.93] kPa) compared to survivors (23.85 [19.57-28.13] kPa) (P = 0.03) and had a higher A-a gradient (51.05 [35.68-66.42] kPa) compared to survivors (36.07 [30.2-41.94]) kPa though not significant (P = 0.06). Twenty-nine patients (59.2%) were oscillated (Sensormedics 3100A) including all 7 non-survivors. There was no difference in ventilation requirements for CMV prior to oscillation. Seventeen of the 49 (34.7%) were treated with Nitric Oxide including 5 out of 7 non-survivors (71.4%). The median (95% CI) number of failed organs was 3 (1.96-4.04) for non-survivors compared to 1 (0.62-1.62) for survivors (P = 0.03). There were 27 patients with isolated respiratory failure all of whom survived. Six (85.7%) of the non-survivors also required cardiovascular support.Conclusion: A crude mortality of 14.3% compares favourably to published data. The A-a gradient and PaO2/FiO2 ratio may be of help in morbidity scoring in paediatric ARDS. Use of Nitric Oxide and HFOV is associated with increased mortality, which probably relates to the severity of disease. Multiple organ failure particularly respiratory and cardiac disease is associated with increased mortality. ARDS with isolated respiratory failure carries a good prognosis in children

An investigation into the effects of commencing haemodialysis in the critically ill

<b>Introduction:</b> We have aimed to describe haemodynamic changes when haemodialysis is instituted in the critically ill. 3 hypotheses are tested: 1)The initial session is associated with cardiovascular instability, 2)The initial session is associated with more cardiovascular instability compared to subsequent sessions, and 3)Looking at unstable sessions alone, there will be a greater proportion of potentially harmful changes in the initial sessions compared to subsequent ones. <b>Methods:</b> Data was collected for 209 patients, identifying 1605 dialysis sessions. Analysis was performed on hourly records, classifying sessions as stable/unstable by a cutoff of >+/-20% change in baseline physiology (HR/MAP). Data from 3 hours prior, and 4 hours after dialysis was included, and average and minimum values derived. 3 time comparisons were made (pre-HD:during, during HD:post, pre-HD:post). Initial sessions were analysed separately from subsequent sessions to derive 2 groups. If a session was identified as being unstable, then the nature of instability was examined by recording whether changes crossed defined physiological ranges. The changes seen in unstable sessions could be described as to their effects: being harmful/potentially harmful, or beneficial/potentially beneficial. <b>Results:</b> Discarding incomplete data, 181 initial and 1382 subsequent sessions were analysed. A session was deemed to be stable if there was no significant change (>+/-20%) in the time-averaged or minimum MAP/HR across time comparisons. By this definition 85/181 initial sessions were unstable (47%, 95% CI SEM 39.8-54.2). Therefore Hypothesis 1 is accepted. This compares to 44% of subsequent sessions (95% CI 41.1-46.3). Comparing these proportions and their respective CI gives a 95% CI for the standard error of the difference of -4% to 10%. Therefore Hypothesis 2 is rejected. In initial sessions there were 92/1020 harmful changes. This gives a proportion of 9.0% (95% CI SEM 7.4-10.9). In the subsequent sessions there were 712/7248 harmful changes. This gives a proportion of 9.8% (95% CI SEM 9.1-10.5). Comparing the two unpaired proportions gives a difference of -0.08% with a 95% CI of the SE of the difference of -2.5 to +1.2. Hypothesis 3 is rejected. Fisher’s exact test gives a result of p=0.68, reinforcing the lack of significant variance. <b>Conclusions:</b> Our results reject the claims that using haemodialysis is an inherently unstable choice of therapy. Although proportionally more of the initial sessions are classed as unstable, the majority of MAP and HR changes are beneficial in nature

Ventilatory ratio : a simple bedside index to monitor ventilatory efficiency

A lack of a simple index that monitors ventilatory efficiency at the bedside has meant that oxygenation has been the predominant variable that is used to monitor adequacy of ventilatory strategies and disease severity in mechanically ventilated patients. Due to complexities in its measurement, deadspace ventilation, the traditional method to track ventilatory failure, has failed to become integral in the management of mechanically ventilated patients. Ventilatory ratio (VR) is an easy to calculate index that uses variables measured at the bedside: [Mathematical equation appears here. To view, please open pdf attachment] where [Symbols appears here. To view, please open pdf attachment] is taken to be 100 ml.kg-1.min-1 based on predicted body weight and [Symbols appears here. To view, please open pdf attachment] is taken to be 5 kPa. Physiological analysis of VR dictates that it is influenced by deadspace fraction and CO2 production. Physiological analysis of VR was validated in a benchside lung model and a high fidelity computational cardiopulmonary physiology model. The impact of CO2 production on VR was investigated in patients undergoing laparoscopic surgery who received exogenous intraperitoneal CO2. This showed that delta values of the 2 variables were linear. The variability of CO2 production was examined in ICU patients and results of the study showed that variability of CO2 production was small. In an ICU population correlation of VR was stronger with deadspace in comparison to CO2 production. Of these two variables, deadspace had the greater effect on VR. The clinical uses of VR were examined in 4 databases of ICU patients. VR was significantly higher in non-survivors compared to survivors. Higher values of VR were associated with increased mortality and more ventilator days. A rising values of VR over time was also associated with worse outcome. VR is a simple bedside index that provides clinicians with useful information regarding ventilatory efficiency and is associated with outcome

Estimation of Blood Oxygen Content Using Context-Aware Filtering

In this paper we address the problem of estimating the blood oxygen concentration in children during surgery.Currently, the oxygen content can only be measured through invasive means such as drawing blood from the patient. In this work, we attempt to perform estimation by only using other non-invasive measurements (e.g., fraction of oxygen in inspired air, volume of inspired air) collected during surgery. Although models mapping these measurements to blood oxygen content contain multiple parameters that vary widely across patients, the non-invasive measurements can be used to provide binary information about whether the oxygen concentration is rising or dropping. This information can then be incorporated in a context-aware filter that is used to combine regular continuous measurements with discrete detection events in order to improve estimation. We evaluate the filter using real-patient data collected over the last decade at the Children’s Hospital of Philadelphia and show that it is a promising approach for the estimation of unobservable physiological variables

Inhalation injury: epidemiology, pathology, treatment strategies

Lung injury resulting from inhalation of smoke or chemical products of combustion continues to be associated with significant morbidity and mortality. Combined with cutaneous burns, inhalation injury increases fluid resuscitation requirements, incidence of pulmonary complications and overall mortality of thermal injury. While many products and techniques have been developed to manage cutaneous thermal trauma, relatively few diagnosis-specific therapeutic options have been identified for patients with inhalation injury. Several factors explain slower progress for improvement in management of patients with inhalation injury. Inhalation injury is a more complex clinical problem. Burned cutaneous tissue may be excised and replaced with skin grafts. Injured pulmonary tissue must be protected from secondary injury due to resuscitation, mechanical ventilation and infection while host repair mechanisms receive appropriate support. Many of the consequences of smoke inhalation result from an inflammatory response involving mediators whose number and role remain incompletely understood despite improved tools for processing of clinical material. Improvements in mortality from inhalation injury are mostly due to widespread improvements in critical care rather than focused interventions for smoke inhalation. Morbidity associated with inhalation injury is produced by heat exposure and inhaled toxins. Management of toxin exposure in smoke inhalation remains controversial, particularly as related to carbon monoxide and cyanide. Hyperbaric oxygen treatment has been evaluated in multiple trials to manage neurologic sequelae of carbon monoxide exposure. Unfortunately, data to date do not support application of hyperbaric oxygen in this population outside the context of clinical trials. Cyanide is another toxin produced by combustion of natural or synthetic materials. A number of antidote strategies have been evaluated to address tissue hypoxia associated with cyanide exposure. Data from European centers supports application of specific antidotes for cyanide toxicity. Consistent international support for this therapy is lacking. Even diagnostic criteria are not consistently applied though bronchoscopy is one diagnostic and therapeutic tool. Medical strategies under investigation for specific treatment of smoke inhalation include beta-agonists, pulmonary blood flow modifiers, anticoagulants and antiinflammatory strategies. Until the value of these and other approaches is confirmed, however, the clinical approach to inhalation injury is supportive

Adjuncts to pre-hospital resuscitation strategies for haemorrhagic shock and blast injury : supplemental oxygen and recombinant activated factor VII

M.D. ThesisExplosion is responsible for almost 80% of Coalition injuries in today’s conflicts. Haemorrhage is the leading cause of death and blast lung injury is evident in 11% of Coalition casualties surviving to reach the (UK) Field Hospital. Military prehospital evacuation times can be prolonged and the combined insults of haemorrhage and blast injury present a ‘double hit’ to oxygen delivery. Resuscitation strategies must be capable of preserving life from such trauma for several hours. Alongside fluid therapy, adjuncts to resuscitation might improve battlefield survival. This randomized controlled animal trial assessed two adjuncts: supplemental inspired oxygen and recombinant activated Factor VII (rFVIIa). Neither adjunct is currently available in the far-forward military echelon, but with modern technology, both are potentially deployable. 18 terminally anaesthetized swine were exposed to blast, controlled haemorrhage and grade IV liver laceration (uncontrolled haemorrhage). Animals were allocated randomly into three treatment groups. All animals were resuscitated with normal saline to a hypotensive systolic target (80mmHg), which continued until the 8hr end point. Thirty minutes after the onset of resuscitation each group received one of the following: single (180mcg/kg) dose of rFVIIa; supplemental oxygen (min FiO2 0.3 to maintain SaO2>95%) or the control group (breathed air throughout and received saline placebo 0.18ml/kg). 5/6 control animals died within 4 hours. Supplemental oxygen improved survival (4/6 survival to 8h endpoint, P=0.014). Single dose rFVIIa did not prolong survival compared to control (2/6 survived, p=0.65). Oxygen arrested physiological decline while control and rFVIIa animals continued to decline until death. Supplemental oxygen is a useful adjunct to fluid resuscitation in the context of haemorrhage and blast injury. Delivery of oxygen support capability to forward echelon units is recommended. By contrast, a single intravenous (pre-hospital) dose of rFVIIa was not an effective treatment for blast lung based on our model of complex battlefield injury