Extracorporeal membrane oxygenation for refractory shock in fulminant meningococcal sepsis

Central extracorporeal membrane oxygenation for refractory pediatric septic shock

OBJECTIVE

To demonstrate positive outcome, to achieve higher flow rates, and to reverse shock more quickly by implementing central extracorporeal membrane oxygenation (ECMO) in children with refractory septic shock. Children hospitalized with sepsis have significant mortality rates. The development of shock is the most important risk factor for death. For children with septic shock refractory to all other forms of therapy, ECMO has been recommended but estimated survival is <50% and the best method of applying the technology is unknown. In recent years, our institutional practice has been to cannulate children with refractory septic shock directly through the chest (central, atrioaortic ECMO) to achieve higher blood flow rates.

DESIGN

Retrospective case series.

SETTING

Intensive care unit of a tertiary referral pediatric hospital.

PATIENTS

Twenty-three children with refractory septic shock who received central ECMO primarily as circulatory support.

INTERVENTIONS

Central ECMO.

MEASUREMENTS AND MAIN RESULTS

The primary outcome measure was survival to hospital discharge. Pre-ECMO circulatory and ventilatory parameters, infecting organism, duration and complications of ECMO and length of hospital stay were also collected. Twenty-three patients (median: age, 6 yrs; weight, 20 kg) over a 9-yr period were included. All patients had microbiological evidence of infection, and meningococcemia was the most common diagnosis. Twenty-two (96%) patients had failure of at least three organ systems, and all patients received at least two inotropes with a mean inotrope score of 82.2 (sd, 115.6). Eight (35%) patients suffered cardiac arrest and required external cardiac massage before ECMO. Eighteen (78%) patients survived to be decannulated off ECMO, and 17 (74%) children survived to hospital discharge. Higher pre-ECMO arterial lactate levels were associated with increased mortality (11.7 mmol/L in nonsurvivors vs. 6.0 mmol/L in survivors, p = .007).

CONCLUSIONS

Central ECMO seems to be associated with better survival than conventional ECMO and should be considered by clinicians as a viable strategy in children with refractory septic shock.

Management of septic shock in childhood

OBJECTIVE

The object of this review is to discuss the recognition and treatment of septic shock in children based on principles of resuscitation, antibiotic use and recent therapeutic advances.

METHODS

A comprehensive literature search combining these

METHODS

on-line searches of Ovid, PubMed, and Medline; hand searches of 25 international journals; a trawl of 26 textbooks; searches of reference lists of pertinent articles; and scans of abstracts of recent international meetings. Various national and international units were contacted with regard to current research therapeutic strategies, both published and unpublished.

CONCLUSIONS

Septic shock remains a leading cause of morbidity and mortality in children. Early administration of empirical antibiotic therapy reduces mortality. The keystone of resuscitation is aggressive volume replacement. Adjunctive therapies to modulate the inflammatory response may further enhance outcome, but do not replace principles of resuscitation.

Pharmacokinetic changes during extracorporeal membrane oxygenation: implications for drug therapy of neonates

Extracorporeal membrane oxygenation (ECMO) is a prolonged form of cardiopulmonary bypass used to support patients with life-threatening respiratory or cardiac failure. In neonates, ECMO is used for a variety of indications, including sepsis and pulmonary diseases such as meconium aspiration syndrome, persistent pulmonary hypertension or congenital diaphragmatic hernia. In recent years, ECMO has been increasingly used after surgery to correct congenital cardiac defects. Despite the need for numerous drugs to maintain the ECMO circuit and treat the patient's underlying illness, relatively little is known of the disposition of drugs in this patient population. To date, the largest number of pharmacokinetic studies have been conducted with gentamicin and vancomycin. Both drugs have been found to have an increased volume of distribution, probably as a result of the addition of a large exogenous blood volume for circuit priming. Elimination half-lives for both drugs are prolonged during ECMO, with several studies demonstrating a return to expected values after decannulation. The reason for this prolonged elimination is probably multifactorial, with a reduction in renal function as the primary determinant. This same pattern of an increased volume of distribution and prolonged elimination has been found for several other drugs, including tobramycin, bumetanide and ranitidine. Other factors that affect drug disposition during ECMO include loss of the drug from adhesion to the circuit components and loss in the circulating blood volume during changes in the equipment. The benzodiazepines and propofol are largely sequestered within the circuit. Serum concentrations of heparin, morphine, fentanyl, furosemide, phenytoin and phenobarbital are also reduced by these mechanisms. The addition of haemofiltration or dialysis in up to a quarter of ECMO patients further complicates the determination of population pharmacokinetic parameters. The literature published to date on the pharmacokinetic changes associated with ECMO provide preliminary support for dosage adjustment; however, more research is needed to identify optimal administration strategies for this patient population.

New therapies and vaccines for meningococcal disease

Meningococcal disease (MCD) is an important cause of morbidity and mortality. The pathophysiology consists of a complex interaction of bacterial and host factors, triggered by the release of endotoxin which initiates the inflammatory cascade, resulting in multi-organ failure, coagulopathy, capillary leak, metabolic derangement and eventually death. Prompt recognition and aggressive management are essential in reducing mortality. Over the past decade, there has been intense research into novel therapies and vaccines, with largely disappointing results. Therapies have been broadly divided into anti-endotoxin and anti-TNF-alpha therapies, treatment aimed at correcting coagulopathy and at blood purification and anti-inflammatory cytokine therapy. The reasons for the disappointing results in the search for new therapeutic strategies are difficult to identify. The disordered physiology in MCD results from a complex interaction of several mediators; therefore attempts to correct this by altering just one step represents a gross oversimplification of the process. In addition, the experimental model of endotoxaemia, which is often used, is a poor representation of an acutely ill patient with rapidly progressive shock. There have been several small or poorly designed trials, which have failed to reach definite conclusions. In order to yield conclusive results any future trials must be multicentre, randomised, controlled trials, but these are expensive and, in practice, difficult to conduct. The BPI trial (vide infra) was a significant step forward in this regard and demonstrated the ability to organise a large multicentred trial which can act as a template for future trials. Although the results were not significant there was an overall trend towards improved outcome in the treatment arm. Whilst the development of effective therapies and vaccines are awaited, the priorities at present must be the prompt recognition and aggressive management of disease.

Management of sepsis and septic shock in infants and children

Sepsis and septic shock constitute an important cause of morbidity and mortality in critically ill children. Thus, the systemic response to infection and its management remains a major challenge in clinical medicine. Apart from antibiotic administration, the majority of available therapies are limited to supportive strategies, although considerable efforts are being undertaken to devise innovative approaches that modulate host inflammatory responses. In suspected sepsis, 2 or 3 days' empiric antibiotic therapy should begin immediately after cultures have been obtained without awaiting results. Antibiotics should be re-evaluated when the results of the cultures and susceptibility tests are available. The initial antibiotic (combination) is determined by the likely causative agent, susceptibility patterns within a specific institution, CNS penetration, toxicity, and the patient's hepatic and renal function. The likely offending micro-organism in turn depends primarily on the patient's age, coexistence of any premorbid condition leading to impaired immune response, and the presenting signs and symptoms. Close attention to cardiovascular, respiratory, fluid and electrolyte, haematological, renal and metabolic/nutritional support is essential to optimise outcome. Fluid resuscitation is of utmost importance to overcome hypovolaemia on the basis of a diffuse capillary leak. Monitoring and normalisation of the heart rate is essential. In case of nonresponse to fluid resuscitation, inotropic and vasoactive agents are commonly used to increase cardiac output, maintain adequate blood pressure and enhance oxygen delivery to the tissue. Because respiratory distress syndrome is seen in about 40% of critically ill children with septic shock, increased inspired oxygen is essential. To provide optimal relief from respiratory muscle fatigue and facilitate the provision of positive airway pressure, early intubation and mechanical ventilation should be considered. Renal support is essential to avoid prolonged renal shutdown in hypoperfusion states. Haematological support comprises replacement therapy of clotting factors to overcome disseminated intravascular coagulation. Metabolic support may include glucose support, extraction of ammonia from the body and recognition of liver dysfunction. Nutritional support may modify the inflammatory host response, and early enteral feeding can improve outcome in critical illness. To date, glucocorticoid and non-glucocorticoid anti-inflammatory agents have not shown significant benefit in septic patients.

Extracorporeal support for intractable cardiorespiratory failure due to meningococcal disease

BACKGROUND

Meningococcal disease is still associated with considerable mortality, despite the use of early antibiotics and management in specialised intensive care units, due principally to early refractory myocardial depression and hypotension as well as severe acute respiratory distress syndrome. Extracorporeal membrane oxygenation (ECMO) is a complex technology that uses a modified "heart-lung" machine to provide temporary cardiac and respiratory support. We reviewed the UK and Australian experience of the use of ECMO in patients with refractory cardiorespiratory failure due to meningococcal disease.

METHODS

The records from all 12 known patients supported with ECMO for meningococcal disease in the UK and Australia since 1989 were reviewed.

FINDINGS

12 patients (aged 4 months to 18 years, median 26 months) with meningococcal disease received ECMO over 8 years. In seven patients, ECMO was required early for cardiac support for intractable shock within 36 h of admission to intensive care. In the other five patients, ECMO was indicated for respiratory failure due to severe adult respiratory distress syndrome, which tended to occur later in the disease. The paediatric risk of mortality score ranged from 13 to 40 (median 29, median predicted risk of mortality 72%). Six of the 12 patients required cardiopulmonary resuscitation before ECMO and the other six were deteriorating despite maximal conventional therapy. Overall, eight of the 12 patients survived, with six leading functionally normal lives at a median of 1 year (range 4 months to 4 years) of follow-up.

INTERPRETATION

ECMO might be considered to support patients with intractable cardiorespiratory failure due to meningococcal disease who are not responding to conventional treatment.