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Showing posts from May, 2012

Atrial premature beats

APBs result from ectopic stimuli i.e. these beats arise from somewhere in either the left or right atrium but not in the SA node. After an atrial depolarization, the stimulus that spread normally through the His-Purkinje system into the ventricles gives a normal QRS complex. APBs have the following major features:   1. The atrial depolarization is premature, occurring before the next normal P wave is due. 2. The QRS complex of the APB is often preceded by a visible P wave that usually has a slightly different shape and/or different PR interval from the P wave seen with normal sinus beats. The PR interval of the APB may be either longer or shorter than the PR interval of the normal beats. In some cases, the P wave may be buried in the T wave of the preceding beat. 3. After the APB, a slight pause generally occurs before the normal sinus beat resumes. This usually slight delay is due to “resetting” of the SA node pacemaker by the premature atrial stimulus. This slight delay contras

Abdominal examination - liver

Liver Examination sequence: 1) Start the palpation in the right iliac fossa. If you start in the right lumbar or right hypochondrium you may miss a massively enlarged liver. 2) The radial border of the right hand is used to feel the liver. The hand must be placed flat on the abdomen. Make sure you do not poke the patient’s abdomen with your finger tips. 3) Now your right hand is kept stationary and the patient is asked to take a deep breath. During inspiration the diaphragm becomes flat and pushes the liver downwards. Try feeling the edge when the patient inspires. 4) As the patient breathes out, move your hand up the abdomen for 1-2cm. Step 3) is then repeated. 5) Repeat step 4) till you reach the costal margin or you detect the edge of the liver. 6) If you feel the edge, then you have to work out whether it is a true enlargement of the liver or the latter has been displaced downwards by a hyperinflated lung e.g. in a case of emphysema. To check this, you have to percu

Determining the size of the endotracheal tube

Adults:   We must select the largest diameter ETT that can be tolerated  for adults.  A size 7.5-mm cuffed ETT is well tolerated by  most adult female patients.  A size 8.0-mm cuffed ETT is well  tolerated by most adult male patients. Pediatrics:   An uncuffed ETT should be used for children  under the age of 8 years.    The  formula most commonly used is: ETT size(mm) = (Age[yr] +16)/4 To estimate the depth of insertion for a child older than  2 years: Depth of insertion = 3× internal diameter of the ETT

ECG T wave changes and interpretation

Ventricular repolarisation produces the T wave. The normal T wave is asymmetrical, the first half having a more gradual slope than the second half. This is well shown below with an up-slope of a duration of nearly 3 squares and a down-slope in only around 1 and  1/2 squares.  T wave orientation usually corresponds with that of the QRS complex, and thus is inverted in lead aVR, and may be inverted in lead III.  But the T waves are discordant with the QRS complexes in Left Bundle Branch Block (LBBB) i.e. T is inverted while the QRS complex is positive or vice-versa. T wave is positive in lead II. Left-sided chest leads such as V4-V6 normally always show a positive T wave. In the T wave can be inverted in the right precordial leads in normal persons. T waves are commonly inverted in all precordial leads at birth but usually become upright as time passes. A persistent juvenile pattern with inverted T waves in the leads to the left of V1 occurs in 1-3% o

Light's criteria to differentiate between transudates and exudates

The criteria for separating transudates from exudates were published in 1972 by Light and coworkers. They were based on the measurements of serum and pleural fluid protein and LDH.  The criteria are as follows: If at least one of the following 3 criteria is present, the fluid is virtually always an exudate and if none is present then the fluid is virtually always a transudate: 1)      Pleural fluid : Serum protein ratio > 0.5 2)      Pleural fluid LDH > 2/3 of the upper limit of the serum reference range 3)      Pleural fluid : Serum LDH ratio > 0.6 An exception to using Light’s criteria is in the setting of CHF treated with diuretics. Normally, in CHF, the effusions are due to an increased capillary hydrostatic pressure and are therefore transudates. But the use of diuretics has been shown to increase the pleural fluid protein and LDH concentrations. Thus we will have a false positive result making the fluid appear as an exudate. It is believed to be