I was listening to a lecture yesterday given by the discoverer of the West Nile virus, and he mentioned a topic that I have discussed before: The fact that irradiation of food would greatly reduce food-transmitted illness.
I would like to expand on that topic here, discussing it both as a physicist and as a physician. It is important to realize that gamma radiation at the energies we would employ canNOT make the food radioactive.
There are three types of radiation: alpha rays,. or helium nuclei (two protons plus two neutrons), beta rays, or electrons, and gamma rays, or photons, which we know as visible radiation, infrared radiation, ultraviolet radiation, microwave radiation, radio waves, television waves, or xrays (the label varies depending on the wavelength and energy of the radiation, but they are all photons, or packets of energy). At energies below several Mev (and xrays are in the Kev range, or 1,000 times less energetic) a nucleus cannot be made radioactive. All that Kev radiation can do is to disrupt the nucleus of the cell and fragment its DNA, thereby either killing the cell or rendering it incapable of reproducing. But the food we eat is already dead or dying, and disrupting the nuclei of a leaf of lettuce will not kill it twice over---dead is dead. And the vegetable nucleus cannot absorb the gamma radiation and release it when we eat it; such a process is impossible by the laws of physics, which are much more accurate and precise than the laws of medicine.
The people who got harmed by gamma radiation were people directly exposed to high energy Xrays, such as those at Hiroshima and Nagasaki, as well as many of the people around Chernobyl and Fukushima. The irradiation of the food would take place in processing plants, far away from us, and in a lead-lined shielded room. The radiation would kill viruses (no hepatitis transmitted by the lettuce you eat) bacteria, (no E. Coli from the hamburgers you eat), and parasites (no tapeworm or trichinosis from the ham you eat).
As a public health measure, this process is inexpensive and tremendously protective, but there is an irrational fear of "radiation". Apparently we would rather risk becoming ill by ingesting possibly contaminated food, than expose ourselves to irradiated food. I was also reminded that MRI, or Magnetic Radiation Imaging was initially called NMR, for Nuclear Magnetic Resonance, which is an accurate label of the physics involved, but the "powers that be" pandered to the fear of the word "radiation" by changing its name.
Monday, April 16, 2012
Friday, April 13, 2012
Medicine and the Scientific Method
The scientific method was pioneered by Galileo Galilei who did the first recorded gedankenexperiment (thought experiment) as well as the first experimental test of a physical law. He kept detailed records of his thoughts, experiments, and observations, including the observation while in church that a hanging lamp with a longer chain had a longer period and swung more slowly than a similar lamp with a shorter chain. Through a series of experiments he also determined that the period of the pendulum was independent of the mass of the lamp, that the period varied directly as the square root of the length of the chain, and that the period was independent of the length of the arc. (This latter statement only holds true for arc angle lengths for which the sine of the angle is approximately equal to the angle, expressed in radians, i.e. up to about 10 degrees, which is why grandfather pendulum clocks are tall and thin.)
Now let us address the science behind medical diagnosis and treatment. Almost all correct medical treatments and predictions were arrived at by observation and induction,and almost all the incorrect treatments arrived at by deduction or using false analogies. Induction (pace David Hume) is the reasoning that says that since the sun has risen in the east for over 10,000 years, it will rise in the east tomorrow. Deduction is the reasoning that says that the proper way to prevent calcium kidney stones is to decrease the amount of calcium in the diet (a statement which has been shown to be false: clinical studies have shown that you should INcrease the amount of calcium in the diet). We have to rely on induction because the "laws" of biology and life cannot be expressed by mathematical equations, and there are few if any axioms from which medical "laws" can be deduced. We also sometimes have difficulty defining what we mean by "normal", and how "abnormal" you have to be before a doctor declares that you have a "disease".
And let us not forget the male analog of a tree falling in a forest and making no sound because there is no one there to hear it: Many men feel that you are only sick if a doctor tells you that you are sick, so if you never see a doctor.............then you are never sick. This is one reason why men get so depressed when they have a heart attack---their denial has crashed into the wall of reality. They then also often become extreme believers in the virtues of a healthy diet, weight loss, and daily exercise.
We also have a macro/micro problem: If I want to improve the overall health of a nation of 10 million people, and lengthen the average life expectancy of its citizens, I would recommend certain tests, but for a given individual, since I have no advance way of knowing the ultimate cause of his/her death, I cannot recommend those same tests with the same degree of certainty. I have a number of elderly patients who have refused annual mammograms, and a number of patients (curiously enough not the same people) who have refused an annual stool for occult blood and periodic colonoscopies, and so far none of the first group has developed breast cancer, and none of the second (with one exception) has developed colon cancer. (The exception was a female who had had lymphoma, and did agree to annual pap smears.) In addition, to the best of my knowledge, none of my patients who refused the flu vaccine have died from influenza.
The basis of medical reasoning by induction is that if a certain treatment for a certain disease diagnosed by a certain method "cured" more patients than did non-treatment, then the same treatment for the same disease (if indeed you do have the same disease as the treated group) will cure you. We are here generalizing that we are all human beings, and deliberately neglecting all differences in sex, age, weight, height, hair color, skin color, ethnic background, geography, living conditions, time of year, religious belief, overall health, and prior medical history. Whether or not any of these conditions makes a difference for the particular treatment for a particular disease has not, in general, ever been looked at, and we are also assuming that if a drug is given it will have the same chemical constituents and potency as the medicine used to treat the cured group. This is a very large assumption. We also conveniently ignore the fact that the test group was not on any other medicines, since the test group is almost always pharmacologically null, and most patients over the age of 50 are taking at least three prescription or over-the-counter drugs. To show you how disease outcome predictions have changed, I just read a medical summary of the third patient to survive an infection of the brain with the rabies virus, which we were taught as recently as 10 years ago is 100% fatal.
I am forever reminding my medical residents that common diseases occur commonly, but can occur with uncommon symptoms. For instance, an acute attack of (ocular) glaucoma can present as intense abdominal pain. If a brunette says she is coughing up red hair, then you should check her mediastinum for a dermoid cyst. If a patient complains of red urine or blood-like red strands in the stool, inquire about recent ingestion of beets. If the computer says that a female patient has severe diabetes because she is spilling sugar and protein in her urine, has an elevated blood sugar, and has not had her period for two months, you must first rule out pregnancy, because in most computer disease diagnostic trees, pregnancy is not listed as a disease, and therefore the computer cannot recognize the constellation of symptoms for what it really signifies.
The field of medicine is an art as well as a science. A well-trained physician can look at a patient, recall the last seen visage of the patient and decide that "this patient looks sick", using some internal heuristic and gestalt.
Unfortunately that is not an acceptable computer diagnosis, so we are forced to invent a disease that fits.
I tell my residents that if the admitted patient is alive when I come in to do my morning rounds, then they have succeeded in the first part of their job, which is to ask for each and every symptom and abnormal test "what disease or condition can the patient have that can kill him/her if I don't make the diagnosis, and how can I diagnose and treat it?". This requires applied induction, because the resident must ask him/herself what condition that he/she has either seen or read about that can evince these symptoms. I might add that the real challenge is to know which abnormal tests should be ignored, because they are not clinically significant to the presenting case.
As a final note, a physician's ego should never interfere with the treatment of the patient. A patient's disagreeing with either the diagnosis or proposed treatment is never a reason for the physician so show anger or disbelief. I have many, many male diabetic patients who should be taking insulin but they refuse: if they take insulin they really have diabetes, but if they only take pills then they just have "a sugar problem".
Now let us address the science behind medical diagnosis and treatment. Almost all correct medical treatments and predictions were arrived at by observation and induction,and almost all the incorrect treatments arrived at by deduction or using false analogies. Induction (pace David Hume) is the reasoning that says that since the sun has risen in the east for over 10,000 years, it will rise in the east tomorrow. Deduction is the reasoning that says that the proper way to prevent calcium kidney stones is to decrease the amount of calcium in the diet (a statement which has been shown to be false: clinical studies have shown that you should INcrease the amount of calcium in the diet). We have to rely on induction because the "laws" of biology and life cannot be expressed by mathematical equations, and there are few if any axioms from which medical "laws" can be deduced. We also sometimes have difficulty defining what we mean by "normal", and how "abnormal" you have to be before a doctor declares that you have a "disease".
And let us not forget the male analog of a tree falling in a forest and making no sound because there is no one there to hear it: Many men feel that you are only sick if a doctor tells you that you are sick, so if you never see a doctor.............then you are never sick. This is one reason why men get so depressed when they have a heart attack---their denial has crashed into the wall of reality. They then also often become extreme believers in the virtues of a healthy diet, weight loss, and daily exercise.
We also have a macro/micro problem: If I want to improve the overall health of a nation of 10 million people, and lengthen the average life expectancy of its citizens, I would recommend certain tests, but for a given individual, since I have no advance way of knowing the ultimate cause of his/her death, I cannot recommend those same tests with the same degree of certainty. I have a number of elderly patients who have refused annual mammograms, and a number of patients (curiously enough not the same people) who have refused an annual stool for occult blood and periodic colonoscopies, and so far none of the first group has developed breast cancer, and none of the second (with one exception) has developed colon cancer. (The exception was a female who had had lymphoma, and did agree to annual pap smears.) In addition, to the best of my knowledge, none of my patients who refused the flu vaccine have died from influenza.
The basis of medical reasoning by induction is that if a certain treatment for a certain disease diagnosed by a certain method "cured" more patients than did non-treatment, then the same treatment for the same disease (if indeed you do have the same disease as the treated group) will cure you. We are here generalizing that we are all human beings, and deliberately neglecting all differences in sex, age, weight, height, hair color, skin color, ethnic background, geography, living conditions, time of year, religious belief, overall health, and prior medical history. Whether or not any of these conditions makes a difference for the particular treatment for a particular disease has not, in general, ever been looked at, and we are also assuming that if a drug is given it will have the same chemical constituents and potency as the medicine used to treat the cured group. This is a very large assumption. We also conveniently ignore the fact that the test group was not on any other medicines, since the test group is almost always pharmacologically null, and most patients over the age of 50 are taking at least three prescription or over-the-counter drugs. To show you how disease outcome predictions have changed, I just read a medical summary of the third patient to survive an infection of the brain with the rabies virus, which we were taught as recently as 10 years ago is 100% fatal.
I am forever reminding my medical residents that common diseases occur commonly, but can occur with uncommon symptoms. For instance, an acute attack of (ocular) glaucoma can present as intense abdominal pain. If a brunette says she is coughing up red hair, then you should check her mediastinum for a dermoid cyst. If a patient complains of red urine or blood-like red strands in the stool, inquire about recent ingestion of beets. If the computer says that a female patient has severe diabetes because she is spilling sugar and protein in her urine, has an elevated blood sugar, and has not had her period for two months, you must first rule out pregnancy, because in most computer disease diagnostic trees, pregnancy is not listed as a disease, and therefore the computer cannot recognize the constellation of symptoms for what it really signifies.
The field of medicine is an art as well as a science. A well-trained physician can look at a patient, recall the last seen visage of the patient and decide that "this patient looks sick", using some internal heuristic and gestalt.
Unfortunately that is not an acceptable computer diagnosis, so we are forced to invent a disease that fits.
I tell my residents that if the admitted patient is alive when I come in to do my morning rounds, then they have succeeded in the first part of their job, which is to ask for each and every symptom and abnormal test "what disease or condition can the patient have that can kill him/her if I don't make the diagnosis, and how can I diagnose and treat it?". This requires applied induction, because the resident must ask him/herself what condition that he/she has either seen or read about that can evince these symptoms. I might add that the real challenge is to know which abnormal tests should be ignored, because they are not clinically significant to the presenting case.
As a final note, a physician's ego should never interfere with the treatment of the patient. A patient's disagreeing with either the diagnosis or proposed treatment is never a reason for the physician so show anger or disbelief. I have many, many male diabetic patients who should be taking insulin but they refuse: if they take insulin they really have diabetes, but if they only take pills then they just have "a sugar problem".
Friday, April 6, 2012
How Does a Doctor Determine That You Are Dead?
The concepts of this blog are largely taken from the book "The Undead", by Dick Teresi, which raises serious questions about the possibility that some organ donors may have a functioning cerebral cortex and therefore be aware (and possibly also feel pain) as they are cut into and their organs are harvested for transplant, and this book should be referred to for further information and references.
Disclaimer: I am not opposing organ transplantation here, but merely showing what the legal definition of death is in our present time.
What do we mean by "dead"? There is more than one answer to this question. There is what you would think is or should be the definition, what most doctors think, what many philosophers think, what various religious leaders think, what the law says, and finally, how the law is applied by doctors. Without editorializing, I will describe how the definition of "dead" has changed (I hesitate to use the word "evolved") over the history of man. Our acceptance of the definition is modified by at least three factors: (a) the normal ego cannot conceive of its own non-existence, (b) none of us wishes to be buried while still "alive", and (c) it's easier to say and think that "they" know what they are doing when a doctor declares a patient to be dead.
First, some fundamental facts. The cortex of the brain, which is what we see in our minds when we think of a brain, generates electrical and magnetic impulses while you are alive and thinking, dreaming, processing sensory input from the world, etc. These electrical signals can be detected by an ElectroEncephaloGram, or EEG, and the flow of blood and metabolic activity can be measured by a functional MRI, or fMRI as well as a PET scan.The brain stem controls breathing as well as reflexes that involve the cranial nerves, such as the corneal or blink reflex, the gag reflex, and a positive response to the apnea test---more about these tests later. Finally, the heart has its own pacemaker(s) and can beat by itself and circulate blood even when the brain stem has been totally destroyed.
I am not going to discuss the various definitions of death that operated in different societies, or before WWII, or in fact before 1968. Up until that time, it was generally felt that if your heart stopped beating (no pulse), AND you were not breathing (no signal to the diaphgram from the brainstem), you were considered to be dead. In certain cases of deep coma, some doctors insisted on a "flat line" EEG, i.e. no electrical evidence of cortical activity from the thinking part of your brain. Even then it was recognized that there were exceptions to that rule: certain drug overdoses such as glutethamide (Doriden) or cold water suffocation (drowning and a core body temperature below 95.0 degrees F) could mimic the state of death, and those patients, especially drowned children, could be revived with no apparent aftereffects.
Anesthesiologists often say that a deeply anesthetized patient is in a near-death state, in that they have to mechanically breathe for the patient. In the case of open heart surgery, the still, pulseless heart is shocked back into "life". If the anesthesiologist observes an acute increase in pulse rate or blood pressure during surgery, his/her immediate assumption is that the patient is feeling pain, and a narcotic is injected to suppress the putative pain, i.e. the anesthesia is deepened. Only if the elevated pulse and/or blood pressure does not respond to additional pain medication does he/she inject medicine to lower the pressure and the pulse. So the point here is if the pulse or blood pressure rise as an operation is being performed, the cortex of the brain may be perceiving pain.
In the August 5, 1968 of the Journal of the American Medical Association, the Harvard Committee, which contained psychiatrists, neurologists, and ethicists, but NO cardiologists issued their new guidelines for declaring death. They gave several reasons for the need for this new definition. Two of them were the need to free up ICU beds for patients who could better benefit from them, and to reduce the controversy over obtaining organs for transplantation. The conditions were (caps added by me): an unreceptive and unresponsive patient, no movements or breathing, no reflexes, and TWO FLAT EEG'S taken 24 hours apart. They reiterated the importance of this last test. Note that no mention was made of an absent pulse or a flat line EKG, but then again there were no cardiologists on the panel(!).
Then the federal government stepped in, passing the Uniform Determination of Death Act (UDDA) 1n 1981. This is now the law in all 50 states, The UDDA states that the ENTIRE brain must cease to function, irreversibly, and again it notes that drug overdose and hypothermia must be ruled out. However, unlike the Harvard statement, there is no requirement for flat-line EEG's, and certainly no requirement for a flat-line EKG. It is important to note here for the non-doctors in my reading audience that all the tests of reflexes, including calorics, doll's eyes and ciliospinal are only tests of brain stem activity or the lack thereof. There is NO reliable test for the absence of higher cortical function if an EEG is not done. No reason was given for dropping the last requirement of the Harvard Committee.
Let me close by noting that there are two well-recognized near-death neurological states in which the patients can think and sense the outside world, but doctors are unable to determine that the patient has a functioning brain. In each state, there have been cases of patients recovering and becoming fully conversant with their doctors, and describing what they felt like. One is the Locked-In Syndrome, and the other is the Persistent Vegetative State. In the locked-in syndrome the brain stem is permanently damaged or destroyed, but the cortex is fully functioning. In the persistent vegetative state, there are brain waves, a sleep-wake cycle, and spontaneous breathing. The precise definitions are unimportant except to note that such patients can recover.
P.S. Karen Ann Quinlan lived for over 10 years after she was disconnected from her respirator.
Disclaimer: I am not opposing organ transplantation here, but merely showing what the legal definition of death is in our present time.
What do we mean by "dead"? There is more than one answer to this question. There is what you would think is or should be the definition, what most doctors think, what many philosophers think, what various religious leaders think, what the law says, and finally, how the law is applied by doctors. Without editorializing, I will describe how the definition of "dead" has changed (I hesitate to use the word "evolved") over the history of man. Our acceptance of the definition is modified by at least three factors: (a) the normal ego cannot conceive of its own non-existence, (b) none of us wishes to be buried while still "alive", and (c) it's easier to say and think that "they" know what they are doing when a doctor declares a patient to be dead.
First, some fundamental facts. The cortex of the brain, which is what we see in our minds when we think of a brain, generates electrical and magnetic impulses while you are alive and thinking, dreaming, processing sensory input from the world, etc. These electrical signals can be detected by an ElectroEncephaloGram, or EEG, and the flow of blood and metabolic activity can be measured by a functional MRI, or fMRI as well as a PET scan.The brain stem controls breathing as well as reflexes that involve the cranial nerves, such as the corneal or blink reflex, the gag reflex, and a positive response to the apnea test---more about these tests later. Finally, the heart has its own pacemaker(s) and can beat by itself and circulate blood even when the brain stem has been totally destroyed.
I am not going to discuss the various definitions of death that operated in different societies, or before WWII, or in fact before 1968. Up until that time, it was generally felt that if your heart stopped beating (no pulse), AND you were not breathing (no signal to the diaphgram from the brainstem), you were considered to be dead. In certain cases of deep coma, some doctors insisted on a "flat line" EEG, i.e. no electrical evidence of cortical activity from the thinking part of your brain. Even then it was recognized that there were exceptions to that rule: certain drug overdoses such as glutethamide (Doriden) or cold water suffocation (drowning and a core body temperature below 95.0 degrees F) could mimic the state of death, and those patients, especially drowned children, could be revived with no apparent aftereffects.
Anesthesiologists often say that a deeply anesthetized patient is in a near-death state, in that they have to mechanically breathe for the patient. In the case of open heart surgery, the still, pulseless heart is shocked back into "life". If the anesthesiologist observes an acute increase in pulse rate or blood pressure during surgery, his/her immediate assumption is that the patient is feeling pain, and a narcotic is injected to suppress the putative pain, i.e. the anesthesia is deepened. Only if the elevated pulse and/or blood pressure does not respond to additional pain medication does he/she inject medicine to lower the pressure and the pulse. So the point here is if the pulse or blood pressure rise as an operation is being performed, the cortex of the brain may be perceiving pain.
In the August 5, 1968 of the Journal of the American Medical Association, the Harvard Committee, which contained psychiatrists, neurologists, and ethicists, but NO cardiologists issued their new guidelines for declaring death. They gave several reasons for the need for this new definition. Two of them were the need to free up ICU beds for patients who could better benefit from them, and to reduce the controversy over obtaining organs for transplantation. The conditions were (caps added by me): an unreceptive and unresponsive patient, no movements or breathing, no reflexes, and TWO FLAT EEG'S taken 24 hours apart. They reiterated the importance of this last test. Note that no mention was made of an absent pulse or a flat line EKG, but then again there were no cardiologists on the panel(!).
Then the federal government stepped in, passing the Uniform Determination of Death Act (UDDA) 1n 1981. This is now the law in all 50 states, The UDDA states that the ENTIRE brain must cease to function, irreversibly, and again it notes that drug overdose and hypothermia must be ruled out. However, unlike the Harvard statement, there is no requirement for flat-line EEG's, and certainly no requirement for a flat-line EKG. It is important to note here for the non-doctors in my reading audience that all the tests of reflexes, including calorics, doll's eyes and ciliospinal are only tests of brain stem activity or the lack thereof. There is NO reliable test for the absence of higher cortical function if an EEG is not done. No reason was given for dropping the last requirement of the Harvard Committee.
Let me close by noting that there are two well-recognized near-death neurological states in which the patients can think and sense the outside world, but doctors are unable to determine that the patient has a functioning brain. In each state, there have been cases of patients recovering and becoming fully conversant with their doctors, and describing what they felt like. One is the Locked-In Syndrome, and the other is the Persistent Vegetative State. In the locked-in syndrome the brain stem is permanently damaged or destroyed, but the cortex is fully functioning. In the persistent vegetative state, there are brain waves, a sleep-wake cycle, and spontaneous breathing. The precise definitions are unimportant except to note that such patients can recover.
P.S. Karen Ann Quinlan lived for over 10 years after she was disconnected from her respirator.
Monday, April 2, 2012
Diabetes---Part I
This blog will discuss adult-onset, non insulin-dependent diabetes, otherwise known as Adult Onset Diabetes (AODM), or Diabetes II. The "M", of course, stands for "Mellitus", which is Latin for "sweet", since diabetic urine usually tastes sweet because of its sugar content (there should be no sugar in your urine). This discussion is not meant to be exhaustive, but will cover what I feel to be the essential topics of the disease.
Every cell in your body needs sugar (usually glucose) to function at peak efficiency. All cells can ingest a little glucose by passive absorption, but the absorption is greatly facilitated by the presence of insulin in the bloodstream along with the glucose. Two groups of metabolically active cells can absorb enough glucose without insulin to continue their normal processes: red blood cells and brain cells. If this were not the case, then all diabetics would die very rapidly. I should mention here that cancer cells have a higher metabolic rate than non-cancerous cells, and therefore have an accelerated uptake of glucose. This is the basis for the PET scan, which replaces one O-16 oxygen atom in glucose with O-17, a radioactive oxygen atom that emits a positron (hence Positron Emitting Test) and is thereby converted to N-17, an isotope of nitrogen.
Most diabetic patients have one or both of two defects: either their pancreas does not secrete enough insulin, or their tissues are resistant to the action of insulin. In either case, their blood sugar is higher than is normal for their given metabolic state, and some sugar may spill over into the urine. The urine test for sugar can have several false positives, so by itself the urine test canNOT be used to diagnose diabetes, but only to suggest its presence. I should mention here that the metabolism of the liver is also affected by the presence of insulin, because the liver requires insulin both to suppress its generation of glucose and to enhance its absorption of triglycerides, so that most diabetics have elevated fasting triglyceride levels.
What is a "normal" level of glucose in your blood? There are at least two definitions: the numerical definition which defines a "normal" range, or the clinical definition which states the level at which clinical intervention, i.e. treatment, either extends the patient's life or prevents damage to any organ. I will not consider here the subset of diabetics with congestive heart failure, except to note that blood is a non-Newtonian viscous fluid, and that the shear resistance to blood being circulated by the heart rises abruptly at sugar levels above 250, so that a patient with a glucose of 300 may be in heart failure while the same patient can be brought out of heart failure by lowering the blood glucose to 200.
It is universally accepted that a glucose level greater than 200 measured two hours after a full dinner denotes diabetes; this may be quantified by repeating the measurement two hours after the patient ingests 75 grams of glucose on an empty stomach. It is also generally agreed that a fasting (i.e. 8 AM blood test with no food for the previous 8 to 12 hours) blood glucose of less than 100 means that there is no fasting diabetes. Inbetween these two numbers there is some leeway and much argument. It used to be that a fasting glucose of over 140 was called "impaired glucose tolerance" or "pre-diabetes" and some interventions (e.g. with metformin) reduced the risk of progression to full diabetes. Then the "pre" level was lowered to 125, then 110, and then to 100, with the major result that many more patients were labeled "pre-diabetic) and had to pay higher premiums for life insurance and/or long-term care insurance.
When the blood glucose level is above 200 in most patients, two irreversible events occur. The first, which causes lasting damage, is the deposition of sorbitol, a non water-soluble molecule, into the membranes of the capillaries of some but not all the organs of the body. This renders a capillary bed incapable of transporting oxygen and soluble nutrients across its boundary from the blood to the affected organ. The second, which is of diagnostic import, is an increased creation of glycosolated hemoglobin, or glycohemoglobin (HbA1c) in your bloodstream. When glucose diffuses across the red blood cell membrane, a small percentage of it forms a stable complex with the hemoblogin molecule that all red blood cells possess to carry their oxygen. Since red blood cells have an average lifetime of 120 days in your blood stream, the concentration of glycohemoglobin is an indirect measure of your average blood glucose for the past three months. HbA1c concentrations in excess of 7.0 are considered to be indicative of, or even diagnostic of, diabetes mellitus. (Even this test is not 100% accurate because heavy daily users of aspirin will have an elevated level of HbA1c, since acetylated glycohemoglobin is eluted more rapidly.)
In all individuals, fat cells require insulin to process the conversion of triglycerides to fat molecules. When you become fatter, the number of fat cells does not increase, but rather each fat cell swells. Therefore, the heavier you are, the greater is the total area of fat cell membranes that is exposed to the circulating blood, and the more insulin they will extract from your circulation. This is why as you gain weight you become more and more "pre-diabetic", and why the first advice given to all overweight diabetics is to lose weight. Unfortunately, as I have indicated in earlier blogs, the only method of weight loss that is guaranteed to work is operative reduction of your stomach volume and food capacity, either by stomach banding or by gastric bypass surgery. I should also mention that daily exercise (about 30 minutes non-stop) is also beneficial, because exercise promotes the cellular uptake of glucose from the bloodstream, and this effect lasts for longer than the 30 minutes you spent exercising. When you exercise, it is sufficient to exercise at such a rate that at the end of the 30 minutes you feel that you have had a workout; your pulse rate is immaterial.
P.S. Although elevated blood sugar is pathognomic of diabetes, it is NOT true that eating sugar or carbohydrates will make you diabetic, unless it also makes you gain weight.
Every cell in your body needs sugar (usually glucose) to function at peak efficiency. All cells can ingest a little glucose by passive absorption, but the absorption is greatly facilitated by the presence of insulin in the bloodstream along with the glucose. Two groups of metabolically active cells can absorb enough glucose without insulin to continue their normal processes: red blood cells and brain cells. If this were not the case, then all diabetics would die very rapidly. I should mention here that cancer cells have a higher metabolic rate than non-cancerous cells, and therefore have an accelerated uptake of glucose. This is the basis for the PET scan, which replaces one O-16 oxygen atom in glucose with O-17, a radioactive oxygen atom that emits a positron (hence Positron Emitting Test) and is thereby converted to N-17, an isotope of nitrogen.
Most diabetic patients have one or both of two defects: either their pancreas does not secrete enough insulin, or their tissues are resistant to the action of insulin. In either case, their blood sugar is higher than is normal for their given metabolic state, and some sugar may spill over into the urine. The urine test for sugar can have several false positives, so by itself the urine test canNOT be used to diagnose diabetes, but only to suggest its presence. I should mention here that the metabolism of the liver is also affected by the presence of insulin, because the liver requires insulin both to suppress its generation of glucose and to enhance its absorption of triglycerides, so that most diabetics have elevated fasting triglyceride levels.
What is a "normal" level of glucose in your blood? There are at least two definitions: the numerical definition which defines a "normal" range, or the clinical definition which states the level at which clinical intervention, i.e. treatment, either extends the patient's life or prevents damage to any organ. I will not consider here the subset of diabetics with congestive heart failure, except to note that blood is a non-Newtonian viscous fluid, and that the shear resistance to blood being circulated by the heart rises abruptly at sugar levels above 250, so that a patient with a glucose of 300 may be in heart failure while the same patient can be brought out of heart failure by lowering the blood glucose to 200.
It is universally accepted that a glucose level greater than 200 measured two hours after a full dinner denotes diabetes; this may be quantified by repeating the measurement two hours after the patient ingests 75 grams of glucose on an empty stomach. It is also generally agreed that a fasting (i.e. 8 AM blood test with no food for the previous 8 to 12 hours) blood glucose of less than 100 means that there is no fasting diabetes. Inbetween these two numbers there is some leeway and much argument. It used to be that a fasting glucose of over 140 was called "impaired glucose tolerance" or "pre-diabetes" and some interventions (e.g. with metformin) reduced the risk of progression to full diabetes. Then the "pre" level was lowered to 125, then 110, and then to 100, with the major result that many more patients were labeled "pre-diabetic) and had to pay higher premiums for life insurance and/or long-term care insurance.
When the blood glucose level is above 200 in most patients, two irreversible events occur. The first, which causes lasting damage, is the deposition of sorbitol, a non water-soluble molecule, into the membranes of the capillaries of some but not all the organs of the body. This renders a capillary bed incapable of transporting oxygen and soluble nutrients across its boundary from the blood to the affected organ. The second, which is of diagnostic import, is an increased creation of glycosolated hemoglobin, or glycohemoglobin (HbA1c) in your bloodstream. When glucose diffuses across the red blood cell membrane, a small percentage of it forms a stable complex with the hemoblogin molecule that all red blood cells possess to carry their oxygen. Since red blood cells have an average lifetime of 120 days in your blood stream, the concentration of glycohemoglobin is an indirect measure of your average blood glucose for the past three months. HbA1c concentrations in excess of 7.0 are considered to be indicative of, or even diagnostic of, diabetes mellitus. (Even this test is not 100% accurate because heavy daily users of aspirin will have an elevated level of HbA1c, since acetylated glycohemoglobin is eluted more rapidly.)
In all individuals, fat cells require insulin to process the conversion of triglycerides to fat molecules. When you become fatter, the number of fat cells does not increase, but rather each fat cell swells. Therefore, the heavier you are, the greater is the total area of fat cell membranes that is exposed to the circulating blood, and the more insulin they will extract from your circulation. This is why as you gain weight you become more and more "pre-diabetic", and why the first advice given to all overweight diabetics is to lose weight. Unfortunately, as I have indicated in earlier blogs, the only method of weight loss that is guaranteed to work is operative reduction of your stomach volume and food capacity, either by stomach banding or by gastric bypass surgery. I should also mention that daily exercise (about 30 minutes non-stop) is also beneficial, because exercise promotes the cellular uptake of glucose from the bloodstream, and this effect lasts for longer than the 30 minutes you spent exercising. When you exercise, it is sufficient to exercise at such a rate that at the end of the 30 minutes you feel that you have had a workout; your pulse rate is immaterial.
P.S. Although elevated blood sugar is pathognomic of diabetes, it is NOT true that eating sugar or carbohydrates will make you diabetic, unless it also makes you gain weight.
Tuesday, March 27, 2012
Monday, March 19, 2012
Random Medical Facts
In the following, when I state a "fact", I am referring to a datum that has been verified in at least one double-blind clinical study. If I say there is "no evidence", I mean that there has been no such study. And I want to remind my readers that, as always, statistical correlation between condition or action A and disease B does NOT mean that A causes B----I refer you to Hume's "A Discourse Concerning Human Understanding" for a further discussion of this as well as the pitfalls inherent in reasoning by induction. Finally, absence of proof is not proof of absence, in that even though there may be no evidence that an intervention saves lives, the intervention may save lives nevertheless.
1) There is no evidence that an annual physical saves lives.
2) We do not know how often a patient should be brought back for evaluation for ANY condition, i.e. the optimum time interval to preserve the patient's health. We choose a time interval that "feels" right for pap smears,for blood sugar tests, for blood pressure checks, and the like.
3) A doctor seeing a patient with a physical complaint should always ask him/herself two questions: (a) is this patient ill enough to need hospitalization, and (b) what disease could the patient have that could kill him/her if I don't make the diagnosis and start treatment.
4) There is no evidence that total body CT scans saves lives.
5) There is no evidence that fast electron CT scans to evaluate cardiac calcium saves lives.
6) With the exception of a single abdominal ultrasound in males over the age of 65 who have hypertension there is no evidence that screening ultrasound Doppler studies of arterial flows saves lives.
7) Copper wrist bracelets do not treat/prevent arthritis.
8) A staple in your earlobe does not help you to lose weight.
9) The only guaranteed weight loss treatment, which also can reverse diabetes and bring the patient back to normoglycemia is stomach banding.
10) Every patient understates to the doctor the amount of cigarettes and alcohol consumed.
11) Virtually every patient has had or will have "unsafe sex".
12) Eight glasses of water or other fluid a day is not necessary for good health.
13) If you have a purely vegetarian diet with no vitamin supplements you will die from pernicious anemia.
14) All cigarette smokers will develop chronic emphysema and end their lives attached to an oxygen tank if they live long enough.
15) If you want to be tested for Sexually Transmitted Diseases, donate a unit of blood to the Red Cross or your hospital blood bank. Not only will they test your blood free of charge, there will also be no note or record of the test being done in your doctor's medical chart, and you will have helped your country.
16) Pregnant women have the keenest sense of smell of all. When a pregnant woman calls the gas company to say that she smells a gas leak, the repairman never leaves the house until the leak is found.
17) We don't know why some people sneeze uncontrollably when they leave a dark movie house in midday and their eyes are struck by the full force of the sun.
18) Please, please, please never look up your symptoms on the internet. EVERY complaint will be listed as possibly being due to AIDS or cancer, and usually Alzheimer's Disease as well. Please wait until you are given a diagnosis, and then look the diagnosis up.
19) One-half to one drink of any alcohol---beer, wine, whiskey--reduces the heart attack rate and increases your life span.
20) Coffee increases mental alertness, shortens eye-hand reaction time, reduces depression, treats asthma, and potentiates all pain medicines.
1) There is no evidence that an annual physical saves lives.
2) We do not know how often a patient should be brought back for evaluation for ANY condition, i.e. the optimum time interval to preserve the patient's health. We choose a time interval that "feels" right for pap smears,for blood sugar tests, for blood pressure checks, and the like.
3) A doctor seeing a patient with a physical complaint should always ask him/herself two questions: (a) is this patient ill enough to need hospitalization, and (b) what disease could the patient have that could kill him/her if I don't make the diagnosis and start treatment.
4) There is no evidence that total body CT scans saves lives.
5) There is no evidence that fast electron CT scans to evaluate cardiac calcium saves lives.
6) With the exception of a single abdominal ultrasound in males over the age of 65 who have hypertension there is no evidence that screening ultrasound Doppler studies of arterial flows saves lives.
7) Copper wrist bracelets do not treat/prevent arthritis.
8) A staple in your earlobe does not help you to lose weight.
9) The only guaranteed weight loss treatment, which also can reverse diabetes and bring the patient back to normoglycemia is stomach banding.
10) Every patient understates to the doctor the amount of cigarettes and alcohol consumed.
11) Virtually every patient has had or will have "unsafe sex".
12) Eight glasses of water or other fluid a day is not necessary for good health.
13) If you have a purely vegetarian diet with no vitamin supplements you will die from pernicious anemia.
14) All cigarette smokers will develop chronic emphysema and end their lives attached to an oxygen tank if they live long enough.
15) If you want to be tested for Sexually Transmitted Diseases, donate a unit of blood to the Red Cross or your hospital blood bank. Not only will they test your blood free of charge, there will also be no note or record of the test being done in your doctor's medical chart, and you will have helped your country.
16) Pregnant women have the keenest sense of smell of all. When a pregnant woman calls the gas company to say that she smells a gas leak, the repairman never leaves the house until the leak is found.
17) We don't know why some people sneeze uncontrollably when they leave a dark movie house in midday and their eyes are struck by the full force of the sun.
18) Please, please, please never look up your symptoms on the internet. EVERY complaint will be listed as possibly being due to AIDS or cancer, and usually Alzheimer's Disease as well. Please wait until you are given a diagnosis, and then look the diagnosis up.
19) One-half to one drink of any alcohol---beer, wine, whiskey--reduces the heart attack rate and increases your life span.
20) Coffee increases mental alertness, shortens eye-hand reaction time, reduces depression, treats asthma, and potentiates all pain medicines.
Wednesday, March 14, 2012
"To Sleep, Perchance to Dream"
Once again a study on the use of hypnotics (aka "sleeping pills") has made its way into the headlines. This time it was an (online) publication of the British Medical Journal. Again, this study was a retrospective study, which compared patient who took sleeping pills with those who did not, and looked for clinical differences.
As readers of my blog are well aware, I firmly believe that the results of such studies should be used to generate a hypothesis, and not to come to a clinical conclusiuon, This hypothesis must then be tested in a forward study, i.e. now compare users of sleeping pills with non-users for the next two years. One of the most cited retrospective studies was a diet study of American females, which showed that those on a "low-fat" diet had a lower incidence of breast and colon cancer. A five-year study was then done, comparing the cancer rates of American females on a low-fat diet (defined as having fats make up less than 15% of their total daily calories) with those on their regular diet. NO DIFFERENCE was found in the breast or colon cancer rates of these two groups. Nevertheless, the American Cancer Society still recommends a low-fat diet as a cancer preventative.
There can always be confounding effects that invalidate a retrospective study. The first study of coffee drinkers showed that they had significantly more heart attacks than non-coffee drinkers. This created great alarm and various degrees of belief and disbelief, until one epidemiologist realized that more coffee drinkers smoke cigarettes than do non-coffee drinkers, and this was the overwhelming confounding factor and largest risk factor for heart attacks
Insofar as sleeping pills and lack of sleep is concerned (I had written a blog on this in 2009) I am more concerned with the mental effects of lack of sleep than I am with the effects of sleeping pills. The federal government limits the number of hours per day and per week that an interstate trucker can drive as well as the number of hours a commercial pilot can fly. Healthy young medical interns are limited as to the amount of consecutive hours they can work whereas much older physicians such as myself have no such limitation.Lack of sleep impairs concentration, increases irritability, increases the errors made on the job, degrades ego functions, makes one more susceptible to depression, and decreases stamina. I would like to see a study comparing the cognitive functions of patients taking sleeping pills with a matched control group of sleep-deprived patients, to determine which group had the greater dimunition of CNS executive functions. Another study would be to compare for two years the health of an age-matched group wherein both asked for sleeping pills, and only half of them were given the prescription. Then we would have a direct comparison of underslept patients with those on sedative-hypnotics.
As readers of my blog are well aware, I firmly believe that the results of such studies should be used to generate a hypothesis, and not to come to a clinical conclusiuon, This hypothesis must then be tested in a forward study, i.e. now compare users of sleeping pills with non-users for the next two years. One of the most cited retrospective studies was a diet study of American females, which showed that those on a "low-fat" diet had a lower incidence of breast and colon cancer. A five-year study was then done, comparing the cancer rates of American females on a low-fat diet (defined as having fats make up less than 15% of their total daily calories) with those on their regular diet. NO DIFFERENCE was found in the breast or colon cancer rates of these two groups. Nevertheless, the American Cancer Society still recommends a low-fat diet as a cancer preventative.
There can always be confounding effects that invalidate a retrospective study. The first study of coffee drinkers showed that they had significantly more heart attacks than non-coffee drinkers. This created great alarm and various degrees of belief and disbelief, until one epidemiologist realized that more coffee drinkers smoke cigarettes than do non-coffee drinkers, and this was the overwhelming confounding factor and largest risk factor for heart attacks
Insofar as sleeping pills and lack of sleep is concerned (I had written a blog on this in 2009) I am more concerned with the mental effects of lack of sleep than I am with the effects of sleeping pills. The federal government limits the number of hours per day and per week that an interstate trucker can drive as well as the number of hours a commercial pilot can fly. Healthy young medical interns are limited as to the amount of consecutive hours they can work whereas much older physicians such as myself have no such limitation.Lack of sleep impairs concentration, increases irritability, increases the errors made on the job, degrades ego functions, makes one more susceptible to depression, and decreases stamina. I would like to see a study comparing the cognitive functions of patients taking sleeping pills with a matched control group of sleep-deprived patients, to determine which group had the greater dimunition of CNS executive functions. Another study would be to compare for two years the health of an age-matched group wherein both asked for sleeping pills, and only half of them were given the prescription. Then we would have a direct comparison of underslept patients with those on sedative-hypnotics.
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