Cardiac surgery in acute heparin-induced thrombocytopenia managed with therapeutic plasma exchange and intravenous immunoglobulin.

Background: Urgent surgery requiring heparin exposure during cardiopulmonary bypass can be challenging in patients with acute heparin-induced thrombocytopenia (HIT). The use of treatments such as therapeutic plasma exchange (TPE) to remove HIT antibodies and intravenous immunoglobulin (IVIg) to antagonize HIT antibody-mediated platelet activation are increasingly reported in patients who undergo cardiac surgery. The optimal treatment approach to mitigate the risks of heparin administration in this situation is not known. Key Clinical Question: Can TPE coupled to IVIg allow for safe heparin exposure in patients with HIT? Clinical Approach: TPE and IVIg were used to enable heparin exposure for surgical placement of a left ventricular assist device in a patient with HIT. Serial patient samples were tested in antigen-based and functional HIT assays. Conclusion: Dissociation between antigen-based (enzyme-linked immunosorbent assay) and functional (serotonin release assay) testing was noted, and TPE coupled to IVIg was associated with an excellent clinical response.

Physiologic variability at the verge of systemic inflammation: multiscale entropy of heart rate variability is affected by very low doses of endotoxin.

INTRODUCTION: Human injury or infection induces systemic inflammation with characteristic neuroendocrine responses. Fluctuations in autonomic function during inflammation are reflected by beat-to-beat variation in heart rate, termed heart rate variability (HRV). In the present study, we determine threshold doses of endotoxin needed to induce observable changes in markers of systemic inflammation, investigate whether metrics of HRV exhibit a differing threshold dose from other inflammatory markers, and investigate the size of data sets required for meaningful use of multiscale entropy (MSE) analysis of HRV. METHODS: Healthy human volunteers (n = 25) were randomized to receive placebo (normal saline) or endotoxin/lipopolysaccharide (LPS): 0.1, 0.25, 0.5, 1.0, or 2.0 ng/kg administered intravenously. Vital signs were recorded every 30 min for 6 h and then at 9, 12, and 24 h after LPS. Blood samples were drawn at specific time points for cytokine measurements. Heart rate variability analysis was performed using electrocardiogram epochs of 5 min. Multiscale entropy for HRV was calculated for all dose groups to scale factor 40. RESULTS: The lowest significant threshold dose was noted in core temperature at 0.25 ng/kg. Endogenous tumor necrosis factor α and interleukin 6 were significantly responsive at the next dosage level (0.5 ng/kg) along with elevations in circulating leukocytes and heart rate. Responses were exaggerated at higher doses (1 and 2 ng/kg). Time domain and frequency domain HRV metrics similarly suggested a threshold dose, differing from placebo at 1.0 and 2.0 ng/kg, below which no clear pattern in response was evident. By applying repeated-measures analysis of variance across scale factors, a significant decrease in MSE was seen at 1.0 and 2.0 ng/kg by 2 h after exposure to LPS. Although not statistically significant below 1.0 ng/kg, MSE unexpectedly decreased across all groups in an orderly dose-response pattern not seen in the other outcomes. CONCLUSIONS: By using repeated-measures analysis of variance across scale factors, MSE can detect autonomic change after LPS challenge in a group of 25 subjects using electrocardiogram epochs of only 5 min and entropy analysis to scale factor of only 40, potentially facilitating MSE's wider use as a research tool or bedside monitor. Traditional markers of inflammation generally exhibit threshold dose behavior. In contrast, MSE's apparent continuous dose-response pattern, although not statistically verifiable in this study, suggests a potential subclinical harbinger of infectious or other insult. The possible derangement of autonomic complexity prior to or independent of the cytokine surge cannot be ruled out. Future investigation should focus on confirmation of overt inflammation following observed decreases in MSE in a clinical setting.

Tracheostomy: epidemiology, indications, timing, technique, and outcomes.

Tracheostomy is a common procedure performed in critically ill patients requiring prolonged mechanical ventilation for acute respiratory failure and for airway issues. The ideal timing (early vs late) and techniques (percutaneous dilatational, other new percutaneous techniques, open surgical) for tracheostomy have been topics of considerable debate. In this review, we address general issues regarding tracheostomy (epidemiology, indications, and outcomes) and specifically review the literature regarding appropriate timing of tracheostomy tube placement. Based on evidence from 2 recent large randomized trials, it is reasonable to wait at least 10 d to be certain that a patient has an ongoing need for mechanical ventilation before consideration of tracheostomy. Percutaneous tracheostomy with flexible bronchoscopy guidance is recommended, and optimal percutaneous techniques, indications, and contraindications and results in high-risk patients (coagulopathy, thrombocytopenia, obesity) are reviewed. Additional issues related to tracheostomy diagnosis-related groups, charges, and procedural costs are reviewed. New advances regarding tracheostomy include the use of real-time ultrasound guidance for percutaneous tracheostomy in high-risk patients. New tracheostomy tubes (tapered with low-profile cuffs that fit better on the tapered dilators, longer percutaneous tracheostomy tubes) are discussed for optimal use with percutaneous dilatational tracheostomy. Two new percutaneous techniques, a balloon inflation technique (Dolphin) and the PercuTwist procedure, are reviewed. The efficacy of tracheostomy teams and tracheostomy hospital services with standardized protocols for tracheostomy insertion and care has been associated with improved outcomes. Finally, the UK National Tracheostomy Safety Project developed standardized resources for education of both health care providers and patients, including emergency algorithms for tracheostomy incidents, and serves as an excellent educational resource in this important area.