Aneurysms..and Transplants?

This past week was basically a continuation of what I blogged last week. Except that the scope of what I observed was a bit more interesting as compared to the seemingly mundane kidney transplants. So obviously to prolong the life of a patient awaiting kidney transplant, which is in the order of 5 -7 years, the patient has to undergo dialysis every 3 days to purge out urea and other waste products. I observed minor operations intended to either construct or remove blood vessels(Fistula) necessary for dialysis. The first and initial route of dialyzing blood is by peritoneal dialysis. This is done by tapping into high pressure blood from peritoneal artery which is a major vessel with blood being pumped in and out of the heart. While this is reasonable method of drawing blood for dialysis, it is however a short-term approach typically used before an arterovenous fistula (AVF) construction. This is because the peritoneal approach requires making a permanent opening through the neck area which exposes the subject to wide array of infections. A way to get around that is to construct a graft that can provide access to blood under high pressure, while minimizing chances of infections. One can directly poke into a major artery, but poking to into it every 3 days would be dangerous to the patient; a bleeding from artery can be life-threatening. What is normally done to preclude the need to expose the subject such a high risk is to construct a graft by attaching a vein, which are abundant in the body, to a major artery such as the brachial artery (in the arm). This is referred to as arterovenous fistula (AVF) construction. Once the AVF is healed, blood is then drawn by poking the vein (graft) which is less life-threatening as it is abundant and is not a major blood supply vessel. So I observed one of these procedures and a day later observed a De-construction of it in another case and wondered aloud what big arm swelling was(Aneurysm).

As it turns out, repeated poking the graft vein in order to dialyze a patient is like 'repeatedly hitting a car tire against a curb' which effectually results in a bubble-like swelling on the tire. So after years of dialysis, a diabetic patient develops arm aneurysm..I am sure some of you have seen it in the past. When there's no longer a need for this AVF graft, i.e., the patient has gotten a kidney transplant, the aneurysm a.k.a AVF graft has to be removed. There are 2 majors reasons why this is done. One is that aneurysms (distension of vein), increases the cardiac output, necessary to maintain physiological blood pressure. This makes the heart work harder than it should. In addition, increased blood pressure will also aid in further distending the swelling, which can rupture the graft. When this occurs, the subject can bleed to death since the aneurysmic vein is grafted to a brachial artery, a major blood vessel. I hope you have learned that aneurysms are not only aesthetically unpleasant but are also very dangerous....

The Wide World of NYPH and Weill

This past week was interesting, and I got somewhat started on my summer project. I also spent time learning things that pertain to my work back in Ithaca for my dissertation. It is convinient when your physician mentor and doctoral advisor collaborate together. It makes the time here far more meaningful.

I spent some of my time this past week in the pulmonary function testing lab on the fifth floor. It worked out that I got to see function tests on the two different types disease (obstructive and restrictive) and how you can determine the presence of one or the another (or both) from just a couple of measures. The way the pulmonary function test work is basically the person blows into a machine a bunch of different ways (like if your running, calm, hard as you can, etc...). The machine then can calculates:

• How much total air you have in your lungs.
  
• Whats the least amount you can have in your lungs
  
• How much air you can blow out in 1 second
• How much gas exchange your lungs can achieve

and so forth. And just by looking at the ratios between patients performance versus an age-sex-race adjusted basline score for that measure, you can determine a person lung health (anything >80% is normal).

I also had a discussion with a physicist with regards to my summer project (the design aspect at least). He made the interesting (and valid point) that best thing to do sometimes when you want a variation of XYZ product for some reason is just get a manufacturer who makes XYZ anyways do the modification for you. The most important thing I learned though from my discussion with him, though, is that a lot of the time, drawing a picture is the fastest way to get your point across. It makes things understandable to everyone much faster it seems.

Today I start in the ICU, should be interesting. I'll get to see now how the images I analyze are acquired, as well as all the things that appear in the image (i.e. the catheters and such that get put in the patients). I'll let you know how it goes next week.

Neurological Surgery

This week I had the opportunity to observe several more procedures in the interventional neuroradiology department. I gained a better appreciation of the broad range of treatments endovascular approaches combined with imaging technology have made possible. Last week, I discussed the detection and treatment of aneurysms, which are the main cases dealt with in this department. However, I was also able to observe treatment of a scalp AVM (arteriovenous malformation) patient where a glue-type substance was injected to block the channels connecting the arteries to the veins, a stroke patient who was treated with thrombolytic agents injected endovascularly, and a brain tumor patient whose arteries leading to the tumor were embolized to block blood flow to the tumor. These suggest the treatment of many other brain disorders through endovascular means - a much less invasive means than craniotomies – however the technology just needs to be developed.

I also observed a myelogram (a procedure in which a contrast dye was injected into the subarachnoid space next to the spine and x-ray images were taken to visualize the bones and space between bones in the spine) on a patient whose intervertebral disk had slipped and was compressing the spinal cord, causing weakness in his legs and one of his arms. The method of spreading the dye consisted of basically tilting the patient and allowing gravity to spread the dye, and seemed especially crude.

What struck me most during this past week is how much room there is for improvements in biomedical technology - every doctor seems to have ideas of things that could really dramatically improve treatment if developed. In the interventional neuroradiology department, there are still issues with catheters being able to navigate through some of the tortuous channels in the brain, technology for treatment of aneurysms, and so forth. I spent some portion of this past week investigating improvements in technology for treating cerebrovascular disorders and parameters that would govern improvements. Some ideas that are being worked out for aneurysm treatment in particular include hydrogel coils that expand upon being inserted in the blood such that they expand to fill an aneurysm and polymer materials that harden to fill an aneurysm.

Biomedical Engineering-what we are studying.

As engineers we are always trying to improve things. We look at our cars, computers, bikes and etc. looking at how we can make it better, easier to use, more efficient and effective.

As a biomedical engineer, we just through a medical utility twist on the overall basic engineering concept. Here at the Weil Medical Hospital, I have strengthened my understanding of what a Biomedical Engineer is and how we should be able interact with the physicians, nurses and medical staff who use our devices.

Since my time here this summer I have found that the medical staff like the tools and devices as simple as possible. Whether it is microscope to aide the physicians eyes, a dremal tool to cut the skull, or even a simple scalpel to make a incision, the simpler and more durable the better. The physicians goal is not to have fun or enjoy the surgery, but to treat the patient as quickly and safely as possible.

In many cases this summer I found that the physicians did not even know how to use "advance" features of the medical instruments they use....and they admit it! So what does this mean for me; someone who is conducting research on Acoustic Drug Delivery for his Ph.D. and wants to bring his idea to a reality in the operating room. It means that I have to make it simple, easy to use and effective.

Continuing Plastics

In the past week I have been able to see many very interesting cases both in the OR and during office hours. On Monday I attended the monthly Mortality and Morbidity meeting where the death of patients being cared for by plastics is discussed. At the beginning of the meeting a particular program recently implemented in plastics was introduced by a company representative. The program is an online program that allows patients to read and view information on the particular procedure that the surgeon has suggested be performed. This is a beneficial way for patients to have many of their questions and concerns addressed. Additionally, at the meeting a case where a patient had died post surgery was discussed along with the possible causes of death.

Later in the week, I attended many surgeries including a breast reduction, hernia repair with tissue expanders, debridements, excessive skin removals, and eye lifts. During the breast reduction it was interesting to see which parts of the breast were maintained and which were removed; the top portion of the skin was maintained but the breast was formed of mammary tissue from the lower portion of the breast while maintaining the intact nipple. Over 1.1 kg was removed from each breast! Durign the eye procedure a piece of gold was sewn into create a more normal appearance in the eye lid and a portion of the roof of the mouth was inserted below the eye to improve appearance. Using autologous tissue is the best way to avoid complications with an implant.

During office hours it is always interesting to see what case we will walk in on next. In some of the most interesting cases, the patients are dealing with wound healing issues. I have been amazed to see patients that are able to go home even with very large open wounds. The V.A.C. (Vacuum Assisted Closure) system is very often used to help in these cases. This is a fairly basic idea developed over 10 years ago. The patient is fitted with a sponge that covers the open wound and a plastic seal is placed over the sponge. Then a hole is made in the seal and a vacuum hose is attached which allows for continuous suction of the wound. This has been shown to greatly aid in wound closure. In addition, during office hours I have seen Dr. Spector remove small tissue masses and sebaceous cyst, inject steriods to decrease keloid formation, clean wounds of dead tissue, and perform patient consults.

Electrophysiology Lab

At the EP lab, I had the pleasure to shadow Dr. Zacks while he performed ablations on the heart and installed pacemakers.  The first day I met him, he performed an ablation procedure on a mid-20 year old female who had recently discovered that she was prone to fainting due to a congenital heart defect.  Her heart had an accessory pathway (AP) between the right atrium and right ventricle that predisposed her to mild arrhythmias that interfered with her life-style.  Fortunately, the treatment was relatively safe so she agreed to have a few wires inserted into her so that the doctor could ablate the AP using high-energy radio frequencies.  In less than an hour, the procedure was over and post ablation ECG readings suggested that the patient's heart was functioning normally.

In my opinion, she was one of the lucky ones.  Sometimes the ablation procedures don't run so smoothly.  Take for example the case of an elderly patient that was being treated for atrial fibrillation.  In his case, the boundary between the arterial/venous tissue and the atrial myocardium were deemed as sights that promoted electrical conduction anomalies.  To deal with this boundary, the common procedure is to ablate circumferentially around the superior/inferior vena cava and the pulmonary artery and vein.  To my surprise, this procedure was incredibly difficult due to the lack of good engineering tools.  Although the doctor was assisted by a 3D model of the patient's atrium - mapped using an electrode - it seemed like he ablated most of the atrium.  According to an anonymous doctor, this is usually not uncommon because such damage to the endocardium does not compromise the function of the heart.  Nevertheless, one could use an ablation probe that could be adjusted to form a circle or some other shape. (Get at it guys! :)

Patients can obviously have other problems that can cause the electrical propagation down the heart to fail.  For those that have problems with their SA/AV node, the common procedure is to implant an electrical pacemaker.  Frankly, this procedure seemed very simple (this is a good thing).  Two wires with screws at the ends were inserted into the left subclavian artery and were attached inside the right ventricle and right atrium.  Following, the other ends of the wires were attached to a small pacemaker implanted in a sac near the patient's left clavical bone.  This procedure lasted about an hour.  

Catheterization Lab

In the Cath lab, I shadowed Dr. Wong while he performed angiograms and angioplasty.  From what I could gather, it was routine to do an angiogram on a patient to diagnose abnormal growth of the heart's myocardium, occlusions in the coronary arteries or regurgitation in the chambers. Often, while doing the angiograms, if a doctor observes that the vessel is occluded more than 60%, he/she will usually recommend the patient for angioplasty.  Apparently, most doctors prefer not to perform angioplasty on any occlusion since the stent used in the procedure can cause problems in the future.  Mainly, it has been shown that introducing a stent into an artery raises the risk of a clot unless the patient takes a drug such as Plavix for at least a year.  Nevertheless, if the stent is not flush with the arterial wall, the risk of a clot is very high.  As a result, most doctors will use unique high-pressured balloon to insure that the stent is flush with the vessel wall.  A few doctors will even use an interventional ultra sound device (IVUS) to visualize the lumen of the vessel.  

The IVUS seems like a good way to assess the placement of a stent, but it prolongs the procedure.  As a result, most experienced doctors will not use it.  I personally think the IVUS should be built into the lead that carries the balloon.  This would greatly improve the accuracy and long-term success rate of the procedure since the built in IVUS will allow doctors to visualize the lumen of the arteries while they implant the stent. (Get at it guys! :)

 

Vascular Vernacular

Vascular Surgery
Week 2

Like any other profession, the world of vascular surgery is littered with jargon and acronyms. The first step in figuring out what’s going on is learning the lingo, so here’s your guide to some common language heard around the operating room and clinics.

Vascular Vernacular

First off, let’s outline some major anatomical landmarks so we’re all on the same page. The arterial system of the lower body starts with the abdominal aorta, a continuation of the thoracic aorta (the one in your chest you think about when you hear “aorta”). This splits into two common iliac arteries (CI). Going down one leg (and occurring in each leg), the CI splits into the internal iliac artery and the external iliac artery (EI). The EI continues to the groin and is called the common femoral artery (CFA). The CFA splits again into the profunda femoris artery (PFA) and the superficial femoral artery (SFA). The SFA changes name to the popliteal artery behind the knee. This continues and carries blood to the leg as three arteries—the peritoneal artery which stops at the ankle and the anterior and posterior tibial arteries which perfuse the foot. Got it?

A Few Other Terms You Should Be Familiar With:

AAA
“Triple ‘A’”, or Abdominal Aortic Aneurysm

ABI
Ankle Brachial Index
This test is a ratio of the measures of arterial pressure in the ankle to the arm and can be used to detect peripheral vascular disease.

Anastomosis
The joining of blood vessels, such as during an AV fistula

AV fistula
Arteriovenous fistula
This is the joining of an artery to a vein. It can be created for therapeutic reasons (renal dialysis) or can occur congenitally.

Bulldog
A specific type of vascular clamp

C-Arm
Portable fluoroscopic device shaped like a ‘C’ used for angiograms

Debridement
Removal of dead tissue to promote healing of a wound

Endarterectomy
An operation to remove or bypass plaque or blockage in a stenotic artery

Grand Slam
A specific type of guide wire

Patent; patency
The state of being open as applied to vessels or stents

Profunda
Deep seated, as in profunda femoris artery

Restenosis
Reoccurrence of stenosis, or narrowing of a vessel

What Else?

Learning fancy terms was just part of my experience this week. I got to check out a leg angiogram and a debridement of a leg wound. Debridement will hopefully help the tissue to granulate and improve healing. I also spent time at the clinic and met with some reps from Cook regarding a stent trial. This was really great—I got to see the technical specs of the trial and got a medical company’s perspective on pushing their products to a surgeon.

That’s all for now!