Posts for category: Hypertension
In the early 1980’s, while I was in medical school, another class of blood pressure (BP) medicine was developed called angiotensin-converting enzyme inhibitors (ACEI), based on improved understanding of how the kidneys regulate BP. The kidneys can sense when the system is not full which decreases renal blood flow and causes the production of angiotensin. Meaning: angio-vessel, tensin-squeeze. The arterial constriction raises blood pressure and increases renal blood flow making the system seem fuller. ACEI block this effect and relax blood vessels, which reduces BP. Angiotensin also causes aldosterone to be released from the adrenal gland, which causes salt, and water retention, which does make the system more full. At last we completely understood HTN and had a new wonder drug, captopril, an ACEI that could be used as a single agent, in theory! What we discovered, in practice, ACEI alone only worked transiently. When used alone BP nearly always returned to pre-treatment levels as the kidneys strive to maintain the volume of fluid in the system. The combination of Hydrochlorothiazide (HCTZ) to clamp the volume at a lower level, and ACEI to relax blood vessels, proved to be a potent way to treat HTN, and remains the most common initial therapy. The most commonly used ACEI is the Lisinopril/HCTZ 20/25, $4/30 days at Wal-Mart. ACEI have also shown to reduce the risk of kidney damage in diabetics, reduce the risk of CHF after a heart attack, and improve outcome in patients with CHF. Angiotensin Receptor Blockers (ARB) were developed in the 1990’s for people with adverse reactions to ACEI and work by a similar mechanism. There are a few other BP medications, but these are the most commonly used ones.
Lasix is another fluid pill that is used for patients with a weak heart or systolic CHF, which reduces blood flow in their kidneys, or in patients where the kidneys are weak. This can be viewed as when the hole in the side of the bucket is too small and smaller than the faucet. Even with fluid draining out that hole more fluid is being added faster, and so the bucket will fill up. Lasix is like drilling a hole in the bottom of the bucket, the higher the dose, the bigger the hole. The aim is to use just the right dose/hole to make up for the difference in the size of the hole in the side of the bucket and the size of the faucet. Too big a hole and the bucket runs dry, and the kidneys fail. It is not a substitute for HCTZ because the hole in the bottom drains at a constant rate, so the volume in the bucket goes up and down according to how much is being added. HCTZ and the hole in the side of the bucket is still frequently needed to regulate the fluid level at a constant volume and allows for a lower and safer dose of Lasix.
In conclusion, JNC-7 guidelines referred to in Part 1 states that: “certain high-risk conditions are compelling indications for the initial use of other antihypertensive drug classes (ACEI, ARB, BB, CCB).” However as stated at the beginning, when 2 or more BP meds are required, one of them should be HCTZ.
Hypertension (HTN) and its treatment can be easily understood with a couple of simple models. Most people in East Houston have an intuitive understanding of the dynamics of pumping fluid through pipes! If the pressure in the system is too high, then the pipes are too full, simple! The cardiovascular system is a little more complicated than the pumps and pipes at the chemical plants. Our system is more dynamic because variable amounts of fluids are being added to the system on a regular basis. This is why we have kidneys, to regulate the volume in the system. By maintaining a constant volume in the system, the kidneys regulate our blood pressure on a day-to-day basis. Picture your body as a bucket of water with a faucet pouring fluid in all the time at varying rates. We take in an average of 2.5 liters of salt water per day in food and fluid. Everything we eat was once 90% salt water if it was once living! Without kidneys, the bucket would quickly overflow or explode. The simplest way to think of how your kidneys control the volume is to imagine them as a hole in the side of the bucket. The bucket fills up to the level of the hole then the water spills out keeping the volume in the bucket constant. IF the hole in the side of the bucket is the same size as the opening in the faucet, then it wouldn't matter whether the faucet is wide open or not open at all, the volume in the bucket will remain constant. If the hole is at a higher level than average, the bucket is fuller than average and the pressure in the system is too high. A thiazide diuretic essentially lowers the position of the hole in the side of the bucket thus decreasing the constant volume in the system and lowering the pressure. For that reason, thiazide was the first blood pressure medicine widely used, in the late 1950's and remains the cornerstone of blood pressure treatment still today.
Adrenaline, produced during physical or emotional stress, causes the heart to beat faster and the blood vessels to constrict, which raises blood pressure, and some people just make too much all the time. Propanol was the next blood pressure medicine used in the early 1960's and was the first of it’s class called Beta-Blockers (BB). Beta- Blockers block adrenaline receptors, which cause the heart to beat slower and softer and blood vessels, to relax, which lowers blood pressure. In 1967 the VA published convincing data, from a large study, showing that lowering blood pressure, with the combination of thiazide and Beta-Blockers significantly reduced the mortality and morbidity associated with hypertension, namely cardiovascular heart disease, heart attacks, congestive heart failure (CHF), and stroke. No other combination has proven more effective at prolonging life since. The most commonly used Beta-Blockers today are Metoprolol and Carvedilol. In the 1970's a third class of anti-hypertensive were developed, called calcium channel blockers (CCB). By blocking calcium channels on the smooth muscles around the arteries, it causes them to relax and become more compliant which reduces the pressure transmitted during the heart's contraction cycle, lowered systolic blood pressure. The most commonly used CCB today are Diltiazem, Nifedipine, or amlodipine. Several studies done at that time showed that they reduced, the likelihood of having a second heart attack in patients with coronary artery disease.
Killam MD on Hypertension Part 1
The Joint National Committee on the diagnosis and treatment of hypertension publishes guidelines every few years. I’m not smart enough to write these guidelines, but I am smart enough to know that I should read them! JNC 6 guidelines were published in 1997, JNC-7 guidelines were published in Dec. 2003 and JNC-8 guidelines were published in Feb. 2014. While similar, personally I found that the JNC-7 guidelines were simpler, made more sense, and were easier to understand and follow. It is about 80 pages long with a 1 page abstract with 8 points.
The first three points defined hypertension as >140/90, declared it as a risk factor for cardiovascular disease and stroke, and recommended lifestyle changes for pre-hypertension of 130-140/80-90. The fourth point states; “Thiazide-type diuretics should be used in the drug treatment of most patients with hypertension either alone or combined with drugs from other classes.” The fifth point states; “Most patients with hypertension will require two or more antihypertensive medications.” The sixth point states; “ If blood pressure is > 20/10 above goal, consideration should be given to initiating therapy with two agents, one of which usually should be a thiazide diuretic.” The seventh and eighth points mostly say that the patient is more likely to be compliant, and the treatment is more likely to be successful when the patient has confidence in his or her physician. The understanding and explanation of the treatment regimen are vital to its success.
If you are being treated for hypertension and are not on a Thiazide diuretic, then in my opinion, you should ask your physician “why not?” Let me explain why in my next blog.