Dr. S.M.Sadikot.
Hon. Endocrinologist,
Jaslok Hospital and Research Centre,
Mumbai 400026

Diabetes and high blood pressure are two powerful, if independent, risk factors leading to many serious complications such as cardiovascular diseases states, renal dysfunction and many more. The occurrence of both, diabetes and hypertension, in the same patient does not merely double the chances for developing these problems, but the risk is COMPOUNDED! This is a classic example of 1+1 not equaling two but eleven!

Unfortunately, hypertension is much more frequently seen in a person with diabetes than in the patient who does not have diabetes. In fact, both along with dyslipidemias, central obesity and atherosclerosis are now grouped together in the classical metabolic syndrome, popularly referred to as "Syndrome X".

The pathology which leads to coronary artery disease, cardiac failure, periperal vascular disease, transient ischemic attacks and strokes are all increased significantly when both these risk factors are present in the same patient. Furthermore, there is ample and overwhelming evidence to suggest that microvascular diabetic complications like nephropathy and retinopathy are made worse in the presence of high blood pressure.

Retinopathy is seen earlier in hypertensive as compared to normotensive diabetics. In fact, the severity of retinal changes are closely related to the degree of the hypertension and very significantly, adequate control of the high blood pressure can retard the progression of the retinopathy! There is also considerable evidence that the presence of hypertension is an important factor in accelerating, if not initiating diabetic nephropathy. Microalbuminuria is an important diagnostic factor for the presence of incipient or early diabetic renal disease, and it has been shown that higher degrees of albumin excretion correlates with higher levels of blood pressure. Optimal control of both the blood pressure and the hyperglycemia can return the raised levels of urinary albumin excretion to normal or at the very least, slow down the progression of the disease state to a considerable extent. Even in those patients with diabetes, who have reached a more severe degree of renal dysfunction, those with high blood pressure which has not been adequately controlled, will tend to progress to the end stage at a much faster pace.

In fact, there are people who feel that once a person with diabetes develops a certain degree of dysfunction, there comes a stage of "no return" when even tight glucose control will not be able to stop the relentless progression of the disease state. Even in such circumstances, tight control of the blood pressure (120/80) does help in slowing down the progression!

Thus, patients with high blood pressure are those at greater risk of developing the full blown picture of end stage renal disease as compared to those who are normotensive, or those in whom the blood pressure is optimally controlled.

The story is similar for diabetic retinopathy.

The importance of tight blood glucose control in decreasing the long term complications has been highlighted in recent mega-trials such as the DCCT and the UKPDS and I do not intend going into details here. But there is one excellent trial which I would like to mention.

The importance of controlling hypertension in diabetes is brought about by figures given from the Joslin Clinic. Since 1939, they followed all Type 1 patients who were seen within one year of the diagnosis of the disease. This homogenous group was followed closely till 1980 or until death, which ever was earlier. Ninety percent of the patients survived 20 years, 77% survived 30 years and 46% of the patients survived the 40 years of the study. Of all the patients who died during the 40 years of the study, 48% of the mortality was from coronary artery disease whilst 31% died from renal disease. Most of the latter also had evidence of significant coronary artery disease. Most of those who died with renal disease were in the age from 30-45 years whilst those who died from the coronary episodes were spread over the full age spectrum. Hypertension was present in all the patients dying from the renal disease and in all but three patients who died from the coronary disease. Uncontrolled hypertension was RARELY seen in those who survived !

WHAT ARE OPTIMAL B.P. LEVELS

Thus, it is obvious that high blood pressure is detrimental to a diabetic and that efforts should be made to bring it down. This is where the initial problem arises. What levels of blood pressure constitutes a risk for the development of complications. In the past there was quite a controversy as to what constituted good blood pressure control. Fortunately this has now been laid to rest and in all patients with diabetes, one should aim to achieve a blood pressure recording of as close to 120/80 as possible.

Easier said than done! Unfortunately, the management of high blood pressure, especially the drug therapy is not simple in a person with diabetes. Many of the drugs used in the management of hypertension are themselves apt to cause problems. They may interfere with the metabolic parameters, decrease insulin sensitivity, increase the blood glucose levels, increase the lipid levels, and may worsen some of the complications.

But nothing good comes easily! Although, optimizing the blood pressure levels may be difficult in a person with diabetes, it is definitely possible especially with the recent array of drugs. A judicious approach can successfully optimise the raised blood pressure, and the benefits for the patient far out-weigh any trouble that the doctor has to take in managing the blood pressure.

SOME SPECIAL ASPECTS

Before we discuss the management of high blood pressure in a diabetic, there are certain small, but important, aspects that I would like to mention. High blood pressure may be a manifestation of hypoglycemia. Often, the sudden appearance of high blood pressure in a normotensive diabetic may be the only clue to the presence of subtle, or even subclincial hypoglycemia. Thus, its presence should always make one suspect whether the patient may be undergoing subclinical hypoglycemia. To take an example, which I have used elsewhere the presence of early morning hypertension, possibly accompanied by early morning headaches may be a clue to the presence of nocturnal hypoglycemia. As the patient would be asleep, one may not be able to experience the signs and symptoms of hypoglycemia, but the presence of high blood pressure in the early morning may point towards this possibility. The reason for this is the hypoglycemia is countered by the counter regulatory hormones like epinephrine, cortisol, growth hormone, glucagon etc. A side effect of these hormones would be seen as an increase in the blood pressure. Thus, when faced with a sudden onset high blood pressure in a patient diabetic under treatment, one should not blindly think of starting antihypertensive therapy until such possibilities have been ruled out.

Another aspect which makes the management of high blood pressure difficult is in those patients who do have hypertension but due to the presence of associated autonomic neuropathy, also have postural hypotension. Therefore, it is essential that not only the blood pressure readings be taken on both the arms (in view of the possible presence of peripheral vascular disease ) but also in the lying down, sitting and standing positions. Often, the blood pressure is taken in the lying down position and if this is seen to be high, treatment may be started which may lead to the patient getting a fainting attack when he stands up. Conversely, if the blood pressure is taken in the sitting position as often happens, then one may miss the presence of high blood pressure as the postural drop may mask the hypertension.

MONITORING THE BLOOD PRESSURE.

It is absolutely essential that all patients be made aware of the tremendous importance of keeping their blood pressures under optimal control. One way to show how important you, as the doctor, feels this is, is to check the blood pressure regularly at each visit. It should also be made clear to the patients that blood pressure control, just as it is for blood glucose, must be lifelong and therefore, complacency should not set in once they have been told that the blood pressure has been normalised. Unfortunately, many patients are under the impression that high blood pressure must be acccompanied by some symptoms, the most common being headaches. It has to be made quite clear that this is not so and that high blood pressure can, and does, occur silently. Waiting for it to manifest with signs and symptoms may mean treating the raised blood pressure at a stage when much of the damage has already been done!

I always tell my patients who have high blood pressure that it would be better for them to learn to monitor their own blood pressures regularly and that they should contact me if the pressure recordings are consistently higher than the limits I have set for them. I make it quite clear to the patients that the best way to monitor the blood pressure is to use the mercury meter or the aneroid meter with the use of a simple stethoscope. Human tendency being what it is, many patients get sophisticated measuring instruments from abroad which do not need a stethoscope and which give a audiovisual or digital readout. Many of these instruments have a microphone as the listening device and this must be correctly placed or else one could get quite wrong readings. Even when the patient uses the routine instruments, I make it a point to ask him to get this meter when he comes for a visit and I cross check the accuracy of the instrument. This also enables me to judge whether the patient is correctly measuring the blood pressure. This also enforces in the mind of the patient the importance of a correct and regular check on his blood pressure.