Author: Mobeen Syed

Two years ago. I sat at my desk checking other successful brands in the field of medical education. I was awestruck by how many friends, fans, and followers they had. I felt that this was your way of saying thank you to those who were helping you. At this moment, I thought, I will never be able to do this. This recognition is reserved only for the best.

Then I got to work – as you know, I always do. I wrote down my philosophy. When I die I hope people say, “he worked tirelessly to improve patient care.” I didn’t care if drbeen was small, or we practically had no fans or followers, or that we were a brand not even worth noticing.

Two years later, we’ve just crossed half a million fans and followers this month. I am sitting at my desk, with eyes welling up. Overwhelmed with your love and support.

I have no words to say you thank you, jump into my melting heart, feel it and know that it is my thanks to you. 💕🌹

Thank you for your love and support. We will continue to offer our services and make them even better because you are worth it. Because YOU ARE IMPORTANT to us. Because we are nothing without you. Thank you again. 💕💕💕

Love you

Dr. Mobeen

Question: surgery case – ID SUR1001

64 y F with Hx of emphysema, HTN, laparoscopic hemicolectomy for Stage 2 colorectal cancer, and femoral hernia who presents with cramping abdominal pain, nausea, and vomiting. Her last bowel movement was yesterday morning. On exam, she has a distended abdomen with mild diffuse tenderness without rebound or guarding. She has a lump in her left groin which is reducible and non-tender.

Vitals: T 37.2C, HR 98, BP 138/74, SpO2 93%.
Her WBC is 10.1, Hb 11.4, BUN 39, Cr 1.1, LFTs normal. CT Abdomen / Pelvis shows dilated loops of small bowel with a transition point.

What is the appropriate management?

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The heart pumps a volume of blood into the lungs which after getting oxygenated is transported back to heart. This oxygenated blood is then pumped out of the heart and into the aorta and subsequently into the systemic circulation. As a consequence, at any given time the lungs (pulmonary vasculature) contain around 500ml of blood, thereby allowing them to function as a reservoir of the blood. This reservoir volume is increased by 500 ml when the person is in the supine or lying down position. This is because in supine position there’s an increased venous return (due to the effect of gravity) to the right heart from the peripheries and therefore more blood accumulates in the central parts of body. Upon standing up, this extra 500ml of blood gets redistributed under the effect of gravity, to the now more dependent parts of the body which includes the peripheral tissues and the lower extremities.

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The division of vasculature in the pulmonary circuit is somewhat different from that in the systemic circulation. The arteries in the pulmonary circuit divide in a binary fashion, thereby following the pattern of division of the airways. The veins too exhibit a pattern similar to the arterioles and the bronchioles, thereby finally converging into forming one large pulmonary vein. These pulmonary veins transport the oxygenated blood back to the heart.

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NODAL ACTION POTENTIAL VS. VENTRICULAR ACTION POTENTIAL

The nodal tissues and the Purkinje fibers exhibit automaticity in their properties as they are able to undergo spontaneous depolarizations. In other words, these tissues do not require the need of an external stimulus or a trigger to undergo depolarization. This is in contrast to ventricular fibers that do not show automaticity. The reason behind this phenomenon can be explained as follow:

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  • The resting membrane potential (RMP) of nodal tissues is less negative than the RMP of ventricular fibers. This allows the nodal tissue channels to operate in a semi-activated state even during the resting phase of the action potential. The comparatively more negative ventricular fibers do not show this property and hence, are not easily activated by low voltage impulses.

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Nitric Oxide is called an endothelium derived relaxing factor (EDRF) as it is released by the endothelium of the blood vessel. EDRF cause relaxation of the vascular smooth muscle, and as a result cause vasodilation of the blood vessel. The following factors contribute to the release of nitric oxide from the endothelium:

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  1. Blood travelling at high velocity causes a shearing effect on the wall of the blood vessels. As the endothelial cells endure a drag force produced due to friction. This results in a mechanical trigger which stimulates release of nitric oxide.

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TYPES OF CHANNELS AND CONCENTRATIONS OF VARIOUS IONS

  1. Sodium Channels: The concentration of sodium ions outside the cell membrane is greater than that inside the cell. Therefore, there is a passive movement of sodium ions into the cell as the channels open. The sodium channels are voltage gated as they undergo conformational change in response to differences in potential across the membrane. The sodium channels have two types of gates that control the passage of sodium ions; the ‘H’ gate and the ‘M’ gate. At resting stage, the M gate is closed and the H gate is open. Upon stimulation by an action potential, the M gate opens and the channels become active, allowing sodium ions to travel into the cell. This opening of the channels is limited by time. After a fraction of a second, the H gates close spontaneously rendering the channels inactive. The sodium channels enter a refractory period during which they cannot be activated no matter how strong is the stimulus. At the same time, the M gate closes as well. As soon as the refractory period ends, the H channels open and the sodium channels are restored to their initial inactive state. The M gates remain closed till the arrival of the next action potential and the cycle is repeated.

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Different states of the fast sodium channels and relative conformational states of the H and M gates are summarized in the table below:

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