Friday, March 13, 2015

Driving Pressure in ARDS: A new concept!


Using a statistical tool known as multilevel mediation analysis to analyze individual data from 3562 patients with ARDS enrolled in nine previously reported randomized trials, we examined ΔP as an independent variable associated with survival. In the mediation analysis, we estimated the isolated effects of changes in ΔP resulting from randomized ventilator settings while minimizing confounding due to the baseline severity of lung disease.


Among ventilation variables, ΔP was most strongly associated with survival. A 1-SD increment in ΔP (approximately 7 cm of water) was associated with increased mortality (relative risk, 1.41; 95% confidence interval [CI], 1.31 to 1.51; P<0.001), even in patients receiving “protective” plateau pressures and VT (relative risk, 1.36; 95% CI, 1.17 to 1.58; P<0.001). Individual changes in VT or PEEP after randomization were not independently associated with survival; they were associated only if they were among the changes that led to reductions in ΔP (mediation effects of ΔP, P=0.004 and P=0.001, respectively).


We found that ΔP= Pplateau - PEEP was the ventilation variable that best stratified risk. Decreases in ΔP owing to changes in ventilator settings were strongly associated with increased survival. 

Sunday, December 28, 2014

New Oral Anticoagulants: Specific tests

Anti-FXa activity
PT and aPTT modified according to the reagent (PT more sensitive)

Anti-FXa activity
PT and aPTT not really prolonged

Ecarin clotting time, Haemoclott or anti-IIa
PT, aPTT and TT modified according to the reagent (aPTT more sensitive)

Ref. MM Samama et al Clin Chem Lab Med 2011;49,761

Wednesday, August 27, 2014

Wednesday, June 11, 2014

Mechanical ventilation in pregnancy

Mechanical Ventilation in Pregnancy

The indications for intubation of a pregnant patient are no different than the non-pregnant patient.

The guiding principle of ventilating the pregnant patient is ensuring adequate oxygen delivery. The goal is a PaO2 of >90 mmHg.

Positive end-expiratory pressure (PEEP) should be applied to keep the FiO2 <60%, but the patient should be kept in the left lateral decubitus position to minimize the effect of PEEP on venous return.

Permissive hypercapnia, a strategy used in acute lung injury, may lead to fetal distress. If higher PaCO2 levels are being sustained in the pregnant patient, then continuous fetal monitoring is required.

Sedation with propofol and opioid drugs are safe, though the fetus may need to be intubated on delivery as these drugs cross the placenta.

Benzodiazepines should be avoided as they have been shown to increase the incidence of cleft palate.

Higher than normal peak and plateau airway pressures can be expected on the ventilator: compression of the diaphragm by the gravid uterus will increase respiratory system elastance.

Fetal viability can be maintained while a patient is on mechanical ventilation, even during maternal brain death. Delivery or termination of pregnancy does not seem to improve the respiratory status of the mother, and therefore is not recommended.

Saturday, June 7, 2014

Perioperative Erythropoetin Use

- Use is encouraged when expected surgical blood loss > 800 ml.
- It is indicated when Hemoglobin value is between 10 and 13 without iron deficiency anemia.
- Dose approved is 600 U/kg/week subcutaneously.
- It is given in 3 injections. 
- It should be started 3 weeks prior to surgery without exceeding hemoglobin target level of 15.
- Monitor blood pressure before each injection.

Ref. MAPAR 2014

Monday, June 2, 2014

The EEG waves


0-3 Hz

Deep sleep or deep anesthesia; hypoxia, hypocapnea, ischemia,

Electrolyte disturbances


4-7 Hz

Sleep and anesthesia


8-13 Hz

Resting, awake with eyes closed

Sunday, June 1, 2014

Blood transfusion reactions

Hemolytic Reactions




Acute Hemolytic Transfusion Reaction

Antibody reaction  + Complement fixation to rbc A, B, Kell, Kidd, Duffy and Ss antigens

Hemolysis, acute renal failure, hypotension, bronchospasm, DIC

Supportive measures: inotropes and vasopressors to prevent shock, maintain intravascular volume and urine output with IVF and diuretics

Delayed Hemolytic Reactions


Prior sensitization to donor antigens (kidd, kell, Rh) – low levels of antibodies over time such that they are not detected on routine screening. Transfusion exposure causes an anamnestic response.

Usually rbc destruction occurs extravascularly and symptoms are less severe than AHTR. Low grade fever, ↑ indirect bilirubin, jaundice, anemia

Supportive, hydration and transfusion of compatible rbc as necessary




Nonhemolytic reactions




Minor Allergic Reactions

Allergic reaction to donor plasma proteins

Rash, pruritus, swelling

Diphenhydramine, Steroids

Anaphylactic Reactions

Prior sensitization in a patient with IgA deficiency and subsequent exposure to IgA containing product

Dyspnea, bronchospasm, angioedema, hypotension

Steroids, epinephrine

Febrile reactions

Antibody reactions to donor leukocytes.

Typically >1◦C rise in temperature within 4 hours of transfusion plus chills, myalgia, nausea, non-productive cough, respiratory distress

Acetaminophen. Usually defervesce in 48 hours.


Transfusion-Related Acute Lung Injury (TRALI)


Anti- HLA antibodies in the donor interacts with recipients leukocytes causing aggregation in the pulmonary circulation

Fever, chills, non-cardiogenic pulmonary edema, bilateral pulmonary infiltrates and severe pulmonary insufficiency

Supportive. Usually resolves in 24-48 hours with supportive care

Graft-Versus-Host Disease (GVHD)

Donor lymphocytes may not be rejected in immunosuppressed patients. They can proliferate and establish an immune response against the recipient. Typically with transfusion of cellular products, less with FFP and cryoprecipitate.

Rapid pancytopenia

Irradiation of blood products is the only proven preventive measure.