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The Forgotten Hemodynamic (PCO2 Gap) in Severe Sepsis
Background. Central venous-arterial carbon dioxide difference (PCO2 gap) can be a marker of cardiac output adequacy in global metabolic conditions that are less affected by the impairment of oxygen extraction capacity. We investigated the relation between the PCO2 gap, serum lactate, and cardiac index (CI) and prognostic value on admission in relation to fluid administration in the early phases of resuscitation in sepsis. We also investigated the chest ultrasound pattern A or B. Method. We performed a prospective observational study and recruited 28 patients with severe sepsis and septic shock in a mixed ICU. We determined central venous PO2, PCO2, PCO2 gap, lactate, and CI at 0 and 6 hours after critical care unit (CCU) admission. The population was divided into two groups based on the PCO2 gap (cutoff value 0.8 kPa). Results. The CI was significantly lower in the high PCO2 gap group (). The high PCO2 gap group, on admission, required more administered fluid and vasopressors ( and , respectively). There was also a significant difference between the two groups for low mean pressure (), central venous O2 (), and lactate level (). The mean arterial pressure was lower in the high PCO2 gap group, and the lactate level was higher, indicating global hypoperfusion. The hospital mortality rate for all patients was 24.5% (7/28). The in-hospital mortality rate was 20% (2/12) for the low gap group and 30% (5/16) for the high gap group; the odds ratio was 1.6 (95% CI 0.5–5.5; ). Patients with a persistent or rising PCO2 gap larger than 0.8 kPa at T = 6 and 12 hours had a higher mortality change (n = 6; in-hospital mortality was 21.4%) than patients with a PCO2 gap of less than 0.8 kPa at T = 6 (n = 1; in-hospital mortality was 3%); this odds ratio was 5.3 (95% CI 0.9–30.7; ). The PCO2 gap had no relation with the chest ultrasound pattern. Conclusion. The PCO2 gap is an important hemodynamic variable in the management of sepsis-induced circulatory failure. The PCO2 gap can be a marker of the adequacy of the cardiac output status in severe sepsis. A high PCO2 gap value (>0.8 kPa) can identify situations in which increasing CO can be attempted with fluid resuscitation in severe sepsis. The PCO2 gap carries an important prognostic value in severe sepsis.
A Predictive Model for Acute Respiratory Distress Syndrome Mortality Using Red Cell Distribution Width
Methods. This observational retrospective cohort study includes 318 ARDS patients extracted from an ICU database between the years of 2001 and 2008. Clinical factors including age, gender, comorbidity score, Sequential Organ Failure Assessment (SOFA) score, and PaO2/FiO2 ratio were chosen for the base model to predict ICU mortality. The RDW value at the time of ARDS diagnosis was added to the base model to determine if it improved its predictive ability. Results. 318 subjects were included; 113 (36%) died in the ICU. AUC for the base model without RDW was 0.76, and 0.78 following the addition of RDW . The NRI was 0.46 (), indicating that, in 46% of patients, the predictive probability of the model was improved by the inclusion of RDW. Conclusions. Adding RDW at time of ARDS diagnosis improved discrimination in a model using 4 clinical factors to predict ICU mortality.
Beta-Blocker Therapy Preserves Normal Splenic T-Lymphocyte Numbers Reduced in Proportion to Sepsis Severity in a Sepsis Model
Lymphocyte cell death contributes to sepsis-induced immunosuppression, leading to poor prognosis. This study examined whether sepsis severity and beta-blocker therapy could affect the degree of T-lymphocyte cell death in a mouse model of sepsis. In the first control study, 20 animals were allocated to 4 groups: control group with sham operation (group C, n = 5) and 3 groups with cecum ligation and puncture (CLP) performed at 3 different sites: proximal, middle, and distal cecum (groups CLP-P, CLP-M, and CLP-D, respectively; n = 5 in each group). Their spleens were resected under general anesthesia 24 hours after CLP, and the total number of normal splenic T lymphocytes per mouse and the percentage of apoptotic T lymphocytes were evaluated using flow cytometry. In the second experimental study, the effect of the beta-blocker esmolol was examined in CLP-P (group CLP-PE vs. CLP-P; n = 5 in each group). The total normal splenic T-lymphocyte numbers per mouse significantly decreased in proportion to CLP severity (group C, 18.6 × 106 (15 × 106–23.6 × 106); CLP-D, 9.2 × 106 (8.8 × 106–9.8 × 106); CLP-M, 6.7 × 106 (6.3 × 106–7.0 × 106); and CLP-P, 5.3 × 106 (5.1 × 106–6.8 × 106)). Beta-blocker therapy restored T-lymphocyte numbers (group CLP-PE vs. CLP-P; 6.94 ± 1.52 × 106 vs. 4.18 ± 1.71 × 106; ) without affecting apoptosis percentage. Beta-blocker therapy might improve sepsis-induced immunosuppression via normal splenic T-lymphocyte preservation.
Impact of Hyperoxia and Hypocapnia on Neurological Outcomes in Patients with Aneurysmal Subarachnoid Hemorrhage: A Retrospective Study
In recent decades, there is increasing evidence suggesting that hyperoxia and hypocapnia are associated with poor outcomes in critically ill patients with cardiac arrest or traumatic brain injury. Yet, the impact of hyperoxia and hypocapnia on neurological outcome in patients with subarachnoid hemorrhage (SAH) has not been well studied. In the present study, we evaluated the impact of hyperoxia and hypocapnia on neurological outcomes in patients with aneurysmal SAH (aSAH). Patients with aSAH who were admitted to the intensive care unit (ICU) of a tertiary hospital in Hong Kong between January 2011 and December 2016 were retrospectively recruited. Patients’ demographics, comorbidities, radiological findings, clinical grades of SAH, PO2, and PCO2 within 24 hours of ICU admission, and Glasgow Outcome Scale (GOS) at 3 months after admission were recorded. Patients with a GOS score of 3 or less were considered having poor neurological outcomes. Among the 244 patients with aSAH, 122 of them (50%) had poor neurological outcomes at 3 months. Early hyperoxia (PO2 > 200 mmHg) and hypercapnia (PCO2 > 45 mmHg) were more common among patients with poor neurological outcomes. Logistic regression analysis indicated that hyperoxia independently predicted poor neurological outcomes (OR 3.788, 95% CI 1.131–12.690, ). Classification tree analysis revealed that hypocapnia was associated with poor neurological outcomes in patients who were less critically ill (APACHE < 50) and without concomitant intracranial hemorrhage (ICH) or intraventricular hemorrhage (IVH) (adjusted , χ2 = 7.452). These findings suggested that hyperoxia and hypocapnia may be associated with poor neurological outcomes in patients with aSAH.
Using pCO2 Gap in the Differential Diagnosis of Hyperlactatemia Outside the Context of Sepsis: A Physiological Review and Case Series
Introduction. There is an inverse relationship between cardiac output and the central venous-arterial difference of partial pressures of carbon dioxide (pCO2 gap), and pCO2 gap has been used to guide early resuscitation of septic shock. It can be hypothesized that pCO2 gap can be used outside the context of sepsis to distinguish type A and type B lactic acidosis and thereby avoid unnecessary fluid resuscitation in patients with high lactate, but without organ hypoperfusion. Methods. We performed a structured review of the literature enlightening the physiological background. Next, we retrospectively selected a series of case reports of nonseptic critically ill patients with elevated lactate, in whom both arterial and central venous blood gases were simultaneously measured and the diagnosis of either type A or type B hyperlactataemia was conclusively known. In these cases, we calculated venous-arterial CO2 and O2 content differences and pCO2 gap. Results. Based on available physiological data, pCO2 can be considered as an acceptable surrogate of venous-arterial CO2 content difference, and it should better reflect cardiac output than central venous saturation or indices based on venous-arterial O2 content difference. In our case report of nonseptic patients, we observed that if global hypoperfusion was present (i.e., in type A lactic acidosis), pCO2 gap was elevated (>1 kPa), whilst in the absence of it (i.e., in type B lactic acidosis), pCO2 gap was low (<0.5 kPa). Conclusion. Physiological rationale and a small case series are consistent with the hypothesis that low pCO2 gap in nonseptic critically ill is suggestive of the absence of tissue hypoperfusion, mandating the search for the cause of type B lactic acidosis rather than administration of fluids or other drugs aimed at increasing cardiac output.
Evaluation of the Safety of Percutaneous Dilational Tracheostomy Compared with Surgical Tracheostomy in the Intensive Care Unit
Background. Tracheostomy is a necessary procedure for patients who require long-term mechanical ventilation support. There are two methods for tracheostomy in current use: surgical tracheostomy (ST) and percutaneous dilational tracheostomy (PDT). In the current study, we retrospectively compared the safety of both procedures performed in our intensive care unit (ICU). Methods. In this study, we enrolled subjects who underwent tracheostomy in our ICU between January 2012 and March 2016. We excluded subjects who were <20 years old and underwent tracheostomy in the operating room. As a primary outcome, we evaluated the rate of complications between ST and PDT groups. The length of ICU stay, time to tracheostomy from intubation, and the rate of mechanical ventilation and mortality at 28 postoperative days were also examined as secondary outcomes. Results. Compared with the ST group, the rate of all complications was lower in the PDT group (13.4% vs. 38.8%, ). Although the rate of intraoperative complications did not differ between the two groups (3.8% vs. 8.1%, ), relative to the ST procedure, the PDT procedure was associated with fewer postoperative complications (34.6% vs. 9.6%, ). Among postoperative complications, accidental removal of the tracheostomy tube and an air leak from the tracheostomy fistula were less frequent in the PDT group than the ST group. Between the two groups, there were no significant differences in their secondary outcomes. Conclusion. This retrospective study indicates that relative to ST, PDT is a safer procedure to be performed in the ICU. Fewer postoperative complications following PDT might be attributed to the small skin incision made during this procedure.