Influence of α-stat and pH-stat blood gas management strategies on cerebral blood flow and oxygenation in patients treated with therapeutic hypothermia after out-of-hospital cardiac arrest: a crossover study.

OBJECTIVES: In patients treated with therapeutic hypothermia after out-of-hospital cardiac arrest, two blood gas management strategies are used regarding the PaCO2 target: α-stat or pH-stat. We aimed to compare the effects of these strategies on cerebral blood flow and oxygenation. DESIGN: Prospective observational single-center crossover study. SETTING: ICU of University hospital. PATIENTS: Twenty-one therapeutic hypothermia-treated patients after out-of-hospital cardiac arrest more than 18 years old without history of cerebrovascular disease were included. INTERVENTIONS: Cerebral perfusion and oxygenation variables were compared in α-stat (PaCO2 measured at 37 °C) versus pH-stat (PaCO2 measured at 32-34 °C), both strategies maintaining physiological PaCO2 values: 4.8-5.6 kPa (36-42 torr). MEASUREMENTS AND MAIN RESULTS: Bilateral transcranial middle cerebral artery flow velocities using Doppler and jugular vein oxygen saturation were measured in both strategies 18 hours (14-23 hr) after the return of spontaneous circulation. Pulsatility and resistance indexes and cerebral oxygen extraction were calculated. Data are expressed as median (interquartile range 25-75) in α-stat versus pH-stat. No differences were found in temperature, arterial blood pressure, and oxygenation between α-stat and pH-stat. Significant differences were found in minute ventilation (p = 0.006), temperature-corrected PaCO2 (4.4 kPa [4.1-4.6 kPa] vs. 5.1 kPa [5.0-5.3 kPa], p = 0.0001), and temperature-uncorrected PaCO2 (p = 0.0001). No differences were found in cerebral blood velocities and pulsatility and resistance indexes in the overall population. Significant differences were found in jugular vein oxygen saturation (83.2% [79.2-87.6%] vs. 86.7% [83.2-88.2%], p = 0.009) and cerebral oxygen extraction (15% [11-20%] vs. 12% [10-16%], p = 0.01), respectively. In survivors, diastolic blood velocities were 25 cm/s (19-30 cm/s) versus 29 cm/s (23-35 cm/s) (p = 0.004), pulsatility index was 1.10 (0.97-1.18) versus 0.94 (0.89-1.05) (p = 0.027), jugular vein oxygen saturation was 79.2 (71.1-81.8) versus 83.3% (76.6-87.8) (p = 0.033), respectively. However, similar results were not found in nonsurvivors. CONCLUSIONS: In therapeutic hypothermia-treated patients after out-of-hospital cardiac arrest at physiological PaCO2, α-stat strategy increases jugular vein blood desaturation and cerebral oxygen extraction compared with pH-stat strategy and decreases cerebral blood flow velocities in survivors.

Usefulness of routine laboratory parameters in the decision to treat refractory cardiac arrest with extracorporeal life support.

AIM: To evaluate the usefulness of routine laboratory parameters in the decision to treat refractory cardiac arrest patients with extracorporeal life support (ECLS). METHODS: Sixty-six adults with witnessed cardiac arrest of cardiac origin unrelated to poisoning or hypothermia undergoing cardiopulmonary resuscitation without return of spontaneous circulation (duration: 155 min [120-180], median, [25-75%-percentiles]) were included in a prospective cohort-study. ECLS was implemented under cardiac massage, using a centrifugal pump connected to a hollow-fiber membrane-oxygenator, aiming to maintain ECLS flow ≥ 2.5 l/min and mean arterial pressure ≥ 60 mm Hg. RESULTS: Forty-seven of 66 patients died within 24 h from multiorgan failure and massive capillary leak. Of 19/66 patients who survived ≥ 24 h with stable circulatory conditions permitting neurological evaluation, four became conscious and were transferred for further cardiac assistance, while three became organ donors. Ultimately, one patient survived without neurologic sequelae after cardiac transplantation. Using multivariate analysis, only pre-cannulation peripheral venous oxygen saturation (SpvO2, 28% [15-52]) independently predicted inability to maintain targeted ECLS conditions ≥ 24 h (odds ratio for each 10%-decrease [95%-confidence interval]: 1.65 [1.21; 2.25], p=0.002). The area under the receiver-operating-characteristics curve was 0.78 [0.63; 0.93]. SpvO2 cut-off value of 33% was associated with a sensitivity of 0.68 [0.50; 0.83] and specificity of 0.81 [0.54; 0.96]. SpvO2 ≤ 8%, lactate concentration ≥ 21 mmol/l, fibrinogen ≤ 0.8 g/l, and prothrombin index ≤ 11% predicted premature ECLS discontinuation with a specificity of 1. CONCLUSION: SpvO2 is useful to predict the inability of maintaining refractory cardiac arrest victims on ECLS without detrimental capillary leak and multiorgan failure until neurological evaluation.

Pulmonary artery sarcoma: a rare cause of dyspnoea.

A 72-year-old woman with no significant medical history presented to the emergency room for severe dyspnoea. The initial clinical diagnosis was acute pulmonary embolism. Heparin infusion was initiated while awaiting a computed tomographic scan but the patient's condition deteriorated dramatically and stat echocardiogram showed tamponade. Post-evacuation echo showed a dilated right ventricle with pulmonary hypertension and obstruction of the right pulmonary artery by a homogeneous mass attached to the pulmonary artery, suggesting a tumour rather than a thrombus. Computed tomographic scan confirmed the presence of an obstructive mass with almost no perfusion of the right lung. The patient was referred to cardiac surgery and the mass was removed, with anatomo-pathological diagnosis of a typical pulmonary artery sarcoma. Unfortunately, the patient died a few days after surgery. Primary pulmonary artery sarcoma is a rare tumour that arises in the central pulmonary arteries. Clinical presentation is often attributed to other causes of pulmonary hypertension, like pulmonary embolism. Magnetic resonance imaging could help to distinguish a soft tissue mass from a thrombus but definitive diagnosis is almost always made at surgery or autopsy since patients usually present in acute and unstable situations. Prognosis is poor, from several months to a few years, and depends on how early the diagnosis is made, the presence of recurrence or metastasis after surgical resection, and the use of adjuvant therapy like radiation and chemotherapy.