Percutaneous venovenous CO2 removal with regional anticoagulation in an ovine model.

Extracorporeal CO2 removal may reduce minute ventilation requirements and allow for better tolerance of low tidal volume ventilating strategies in patients with severe respiratory insufficiency. Conventional extracorporeal gas exchange is labor-intensive, expensive, and usually requires systemic anticoagulation. In this study, a simplified venovenous circuit was developed by using regional citrate anticoagulation to avoid potential complications associated with systemic heparin. Five healthy adult sheep underwent percutaneous placement of a double-lumen 18F catheter into the internal jugular vein. The extracorporeal circuit consisted of a hollow fiber oxygenator and a variable speed roller pump. Regional anticoagulation consisted of a continuous citrate infusion to the inflow limb of the circuit. Systemic calcium levels were maintained by calcium chloride infusion through a central line. CO2 transfer was measured at varying levels of blood and gas flow. CO2 transfer ranged from 31 ml/min (500 ml/min blood flow; 2 l/min gas flow) to 150 ml/min (1000 ml/min blood flow; 15 l/min gas flow) and was directly proportional to blood flow and gas flow (p < 0.05). Normocapnia was maintained despite a 75% reduction in minute ventilation. At 24 hours, there was no significant clot formation in the circuit.

Venovenous carbon dioxide removal in chronic obstructive pulmonary disease: experience in one patient.

Chronic obstructive pulmonary disease (COPD) is the fourth leading cause of death in the United States. Acute exacerbations of COPD account for up to 84% of the total economic cost of this disease. The altered mechanics of the COPD patient represent a unique challenge to the clinician instituting assisted ventilation in this population. We developed an alternative mode of limited extracorporeal support termed Venovenous carbon dioxide removal (VVCO2R). We report our first case using VVCO2R, a 42-year-old white woman with a history of COPD and asthma, who was a heavy smoker at the time of admission. We utilized a compact, low flow pediatric extracorporeal circuit interposed with a low resistance gas exchange device. Venovenous carbon dioxide removal allowed for a reduction in the patient's minute ventilation to 30% of baseline with improved arterial blood gases (ABGs), a reduction in peak airway pressures and improvement in her hyperinflation. Our experience demonstrates that this system can effectively remove CO2 safely in a single cannula venous configuration while maintaining minimal anticoagulation. We believe this system could potentially be utilized in any medical or surgical intensive care unit.

High-frequency percussive ventilation with systemic heparin improves short-term survival in a LD100 sheep model of acute respiratory distress syndrome.

We undertook an assessment of high-frequency percussive ventilation (HFPV) and systemic heparin on survival in our LD100 sheep model of smoke/burn-induced acute respiratory distress syndrome (ARDS). This was a prospective controlled outcomes study in a large animal critical care laboratory. ARDS was induced in 13 sheep by a combination of 48 cotton smoke breaths and 40% full-thickness cutaneous burn (LD100) followed by mechanical ventilation (15 ml/kg tidal volume). After meeting ARDS criteria (PaO2/FiO2 < 200), the sheep were divided into high-frequency percussive ventilation (HFPV; n = 7) or volume-controlled mechanical ventilation (VCMV; n = 6) groups. Both groups received systemic heparin to achieve an ACT 180-300 seconds. HFPV was managed with the Volumetric Diffusive Respiration Ventilator (Percussionaire Corp., Sandpoint, ID). The VCMV group was managed with up to 10 ml/kg tidal volume. Arterial blood gases and ventilator settings were monitored every 6 hours after onset of ARDS. HFPV did not affect sheep hemodynamics. Survival 84 hours after smoke and burn injury was significantly greater in the HFPV (7/7, 100%) compared with the VCMV group (3/6, 50%, P < .05). PaCO2 was significantly greater in VCMV group at 36, 48, and 72 hours after smoke and burn injury. PaO2/FiO2 after 36 hours of smoke and burn injury in the HFPV group was improved compared with the VCMV group, but no statistical difference was found. In the VCMV group, peak airway pressure was decreased to 19.7 +/- 2.2 cm H2O at 36 hours from 29 +/- 2.8 at 24 hours as the tidal volume changed from 15 ml/kg to 10 ml/kg and then gradually increased to 39 +/- 5.6 cm H2O at 72 hours. In the HFPV group, peak inspiratory pressure kept constant at a level of 30 cmH2O. In our smoke/burn-induced LD100 sheep model of ARDS, volume-controlled mechanical ventilation with systemic heparin achieved a 50% survival whereas HFPV with systemic heparin achieved 100% survival at 60 hours after the onset of ARDS.

Possible subdural hematoma associated with Ginkgo biloba.

A 78-year-old Caucasian man developed headache, confusion and progressive right-sided weakness following a fall resulting in ecchymosis over the left eye orbit five days prior to admission. A subdural hematoma was diagnosed upon CAT scan. Upon evacuation, a very large left frontoparietal subdural hematoma with the appearance of mixed elements of hemorrhage and older fluid was noted. The finding was chronic subdural hematoma described as "crankcase oil." The patient's only prior medications were lisinopril 20 mg daily and ginkgo biloba 50 mg three times a day. Ginkgo biloba is advocated to augment cerebral blood flow to enhance memory and improve dementia. One of Ginkgo biloba's components is ginkgolide B, a potent inhibitor of platelet activating factor essential for induction of arachidonate-independent platelet aggregation. We believe Ginkgo biloba either caused or predisposed this patient to subdural hematoma and is of concern given ginkgo's widespread use with minimal or no monitoring.