blood_pressure2 case study

Part I – Children Playing in the Heat The summer of 1985 turned out to be the hottest on record for Tulsa, Oklahoma, and that day in July was one of the hottest. Two boys were playing outside while their mothers were inside preparing lunch for their children. “The boys have been outside for more than two hours, they must be hot and tired. Let’s get them inside and have them watch TV after lunch; they can go back outside when it cools off. John has been talking about putting in a pool; that will make these hot summers more bearable.” The women stopped talking when they heard someone tapping on the sliding glass door facing the back yard. “Mrs. Myron, Mrs. Myron, come quickly,” someone called out. “What’s wrong, Jack?” asked Mrs. Myron as she opened the sliding door. “Greg fell over and didn’t get up,” Jack said, as he and the two women ran over to a four- year-old boy lying next to the sand box. “We were building a big castle in the sand box,” Jack continued. “Greg wasn’t happy because one of the towers fell in. He stood and went to jump on it, but he just fell over. I thought he was just playing, but he didn’t get up.” The two women carried the limp boy into the house and lay him on the sofa. Mrs. Myron was placing a cool, wet cloth on her son’s forehead when his eyes opened. “What happened?” Greg asked. “You passed out, again,” replied his mother. “I noticed that you didn’t touch the lemonade we left you boys.” “Do you think we should take him to hospital?” asked Mrs. Rose, Jack’s mother. “I’m afraid this isn’t the first time this has happened,” replied Mrs. Myron. She pinched the skin on the back of her son’s hand and noticed that it did not spring back. “I think he’s just dehydrated. He gets so immersed in what he’s doing that he forgets to drink. It’s my fault. It really is too hot, but he loves to play outside.” Greg started to get off the sofa, but quickly fell back. “Mom, I’m feeling dizzy and I’m really thirsty. Can I have a glass of water?” “Of course, my dear. I think you two will be staying inside this afternoon.” “But Mom…” “I need to have you close by so I can keep an eye on you. Here, I’ll turn on the TV.” “I’ve Fallen Over and I Can’t Get Up” by Madern, Hood, Paul, & Stephens Page 1 by Ashley L. Madern, Michael D. Hood, Jeff rey C. Paul, Jr., and Philip J. Stephens Department of Biology, Villanova University, Villanova, PA NA TI ON AL C ENTE R FO R A C SE S TUDY TEA CH I N G IN S CI EN E C I’ve Fallen Over and I Can’t Get Up

NATIONAL CENTER FOR CASE STUDY TEACHING IN SCIENCE Questions 1. What signs and symptoms did Greg exhibit when he was in the house? Dizziness, thirst, and loss of skin elasticity. 2. Was Mrs. Myron correct when she said that Greg was dehydrated? Which signs and symptoms are consistent with this notion? Yes, the dizziness and thirstiness both can be due to dehydration and your body trying to tell you to get more fluids. The decrease in skin elasticity and loss in appetite/wanting the lemonade is also due to dehydration. The fainting may also be caused by a drop in blood pressure due to the dehydration. 3. Explain how each sign or symptom can be created by dehydration. Dehydration can cause a decrease in blood volume which is what can make the blood pressure drop and result in not enough blood getting to the brain leading to him passing out. Dehydration can also lessen the amount of saliva produced which can make him excessively thirsty as well as the imbalance of electrolytes and fluids that can cause dizziness. Dehydration also means there is less water in the skin which can cause it to lose its elasticity. 4. Mrs. Myron thought that it was not necessary to seek medical treatment. Do you think she was correct? I think due to her knowledge of this happening to her son before she knows how to monitor him and help him rehydrate while also keeping a close eye on him so that if it worsens she could take him to the doctor. Part II – The High School Football Game It was a beautiful Saturday morning in October 1999. The weather in Tulsa, Oklahoma, was a balmy 92°F with 71% humidity. Greg woke up and went downstairs. He felt a little dizzy. “Whoever heard of having a team party the night before the State Championship,” he mumbled to himself as he staggered into the kitchen. “Your breakfast is ready; better hurry and eat or you’ll be late!” Mrs. Myron put the plate of waffles on the table with a smile. “I’m not hungry Mom,” Greg said as he pushed the plate to the center of the table. “Is coffee ready?” “Oh Gregory, it’s probably just nerves for the game tonight. You really should try to eat something or you’re going to fade by the third quarter. Here’s some coffee and take this bagel and banana with you and eat them on the way.” Greg took the bagel and coffee and steadied himself against the table as he stood up. “Are you okay, Greg?” his mother asked him. “Sure, just a little dizzy; probably got up too fast.”  Arriving in the parking lot he polished off the last of the coffee and left the bagel in the car – there was no time to eat, and he still wasn’t feeling hungry anyway. “Myron!” yelled the coach. “Had a little too much fun last night? I know this is only the pre-game warm up, but you look like you’re dragging! Hope you’re ready for tonight. We’re counting on the school’s star running back to lead us to victory!” Greg removed his helmet “Yes, sir!” he yelled enthusiastically, but he felt anything but. “I’ve Fallen Over and I Can’t Get Up” by Madern, Hood, Paul, & Stephens Page 2

NATIONAL CENTER FOR CASE STUDY TEACHING IN SCIENCE Blood pressure 100/60 120/70 Time of urination n/a - Blood pH 7.38 7.35 – 7.45 Arterial pO 2 98 90 - 100 Arterial pCO 2 43 35 - 45 Electrolytes: Na + 152 135 - 147 Electrolytes: K + 3.9 3.5 – 5.2 Blood glucose 65 60 – 110 (fasting) Cortisol (ug/dL) 12 3 – 17 ACTH (pg/mL) 38 <50 Skin color No discoloration - Dr. Jenkins looked at Greg’s heart monitor and noticed that it was still 58. “Your mother mentioned that you did not eat the morning of the game. It was hot yesterday. Did you drink a lot of fluids during the game?” “I rarely drink during games, Doc. You get hit in the gut a lot when you run the ball, and the last thing you want to do is throw up on the fi eld.” The doctor smiled and Mrs. Myron remembered the days when her son would forget to drink when he played outside and ended up passing out. “Do you remember anything before you were tackled?” “One moment I was running down the field and then I remember being in the ambulance with the P.A. announcer saying that we had won the championship.” Greg smiled and moved his arms and felt the IV in his forearm. “That’s to counter any dehydration,” explained the doctor. “How do you feel Greg? Are you nauseous,” he asked Greg as he gently pinched the skin on the back of Greg’s hand; it sprang back. “Yeah. I’m feeling kind of weak and this bad headache makes me feel sort of out of it.” “Can you try sitting up?” asked the doctor. Greg’s father leaned forward to help him. Greg lifted his head. Dr. Jenkins looked at the heart monitor and noticed that Greg’s heart rate increased to only 60 when Greg said that he was feeling dizzy and was seeing flashing lights. “I’m not sure that sitting up is such a good idea,” Greg murmured. “Hmm, why don’t you rest for a bit Greg? I think we’ll repeat the blood work and get a neurologist in for a consultation.” Questions 1. What are Greg’s new signs and symptoms? Weakness, headache, dizziness, and seeing lights. “I’ve Fallen Over and I Can’t Get Up” by Madern, Hood, Paul, & Stephens Page 4

NATIONAL CENTER FOR CASE STUDY TEACHING IN SCIENCE 2. Baroreceptors are responsible for monitoring blood pressure. Where are the baroreceptors located in your body? The baroreceptors responsible for monitoring blood pressure are located near the carotid artery in the neck and near your aortic arch by the heart. 3. Now you will design a pressure receptor. First, draw a circle on a piece of paper and then draw two or three lines from the center to beyond the perimeter of the circle. Imagine that the circle represents a balloon, and the lines are threads, which are attached to the surface of the balloon. How would blowing into the balloon, to increase the pressure of the air inside, affect: a. Th e size of the balloon? b. The threads attached to the surface of the balloon? c. Imagine that the threads are the terminals and axons of sensory neurons. If the terminals are sensitive to stretch, what will happen to the frequency of the action potentials in the axons as the pressure inside the balloon is changed? 4. What parts of your model (question #3) are analogous to the carotid sinus, the sensory nerve endings, and the arterial blood? The balloon represents the carotid sinus, the threads represent the sensory nerve endings, and the pressure from blowing air within the balloon represents the arterial blood. 5. Baroreceptors send sensory information to the medulla in your brain, which then stimulates the autonomic nervous system; this is a critical part of the baroreceptor reflex. What are the two main divisions of the autonomic nervous system? The sympathetic and parasympathetic autonomic nervous systems. 6. The chart below shows that when baroreceptors detect a drop in arterial blood pressure the sympathetic nervous system stimulates the heart and the smooth muscles in the walls of the arteries and the veins. Use an upward arrow (to represent an increase) or a downward arrow (to represent a decrease) to indicate the effect of the sympathetic nervous system on the variable in each numbered box. 1=increase 2=increase 3=increase 4=increase 5=increase 6=decrease 7=decrease 8=decrease 9=increase 10=increase “I’ve Fallen Over and I Can’t Get Up” by Madern, Hood, Paul, & Stephens Page 5

NATIONAL CENTER FOR CASE STUDY TEACHING IN SCIENCE 2. What part of the nervous system was Dr. Rose checking when she hit Greg’s patella tendon with a rubber hammer? She was checking the lumbar spine. 3. What part of the nervous system was Dr. Rose checking when she ran her pen along the underside of Greg’s foot? His central nervous system. 4. What evidence suggests that Greg suffered from a mild concussion? The lessened headache and flashing lights. 5. What types of symptoms would you expect if Greg’s concussion had been more severe? He would have also suffered amnesia, nausea, and ringing in his ears. 6. Do you wish to modify your diagnosis of Greg’s long-term problem? I still believe his symptoms indicate concussion and hydration however we should check for me considering he had similar problems frequently as a child which could indicate a brain tumor. Part V – The Follow-up Visit Greg and his parents walked into the hospital and directly into Dr. Rose’s office. “How have you been over the past week, Greg?” “I’ve been okay, except I felt dizzy a few times.” “I remember you as a boy playing with Jack and passing out in the sandbox. Of course, that was before I went back to school and got my medical degree,” said Dr. Rose. “The dizzy spells seem to be getting more frequent,” said Mrs. Myron. “Could it be because he has been stressed from missing school, getting into college, and getting a football scholarship?” “Stress?” said Greg. “How about coming to the hospital? I get lightheaded just being here.” There was a knock on the office door and two nurses and an orderly entered with a table. “Great timing; I am glad you feel like that Greg. There is one more test I would like you to take. Could you lie on the table facing up?” Greg clambered from the chair onto the table and the nurse attached sticky electrodes to measure his electrocardiogram; she attached a clip to his finger to monitor his heartbeat. “Okay Greg,” said Dr. Rose.” Move down the table so that your feet push against the plate at the bottom.” They could all hear the beeping sound of Greg’s heart in the otherwise silent room. “Now, we are going to tilt the table so that you come to a standing position; don’t worry, the straps will prevent you from falling off the table. We’ll be able to monitor your heart rate and measure your blood pressure, if necessary.” The technician tilted the table. “Wow,” said Greg as the table began to move. The table continued to tilt, and Greg’s heart monitor continued to sound at about the same rate. “Tell us if you feel faint,” said the doctor. “Oh boy, am I feeling dizzy,” said Greg as his eyes rolled back in his head and he passed out. The table was rotated back to the horizontal position again and locked in place. The “I’ve Fallen Over and I Can’t Get Up” by Madern, Hood, Paul, & Stephens Page 7

NATIONAL CENTER FOR CASE STUDY TEACHING IN SCIENCE nurse placed a cold cloth on Greg’s forehead and a pillow under his head as Greg came round. “Just lie there for a few minutes, Greg. You did great,” said the doctor. “I fainted and you said that it was great?” “Yes, the instruments monitored your response and this then allows me to see exactly what happened to your heart during the procedure,” said Dr. Rose as she looked through the ECG recording. “What happened, Dr. Rose—apart from him fainting?” asked Greg’s mother. “Greg fainted as the table reached an angle of around 80 degrees. This probably would not have happened had he not felt the extra stress of being in uncomfortable surroundings here in the hospital. His heart rate did not increase sufficiently to maintain his arterial blood pressure so insufficient blood went to his brain and he passed out.” Questions 1. Imagine a fountain where water is being shot into the air. What happens to the pressure of the water as it travels against gravity? Going against gravity the pressure will decrease. 2. What is the relative position between the heart and the head (or baroreceptors in the carotid sinus) when you are lying down? They are approximately on the same level on the horizontal plane. 3. What is the relative position between the heart and the head (or baroreceptors in the carotid sinus) when you are standing? The heart is now below the head. 4. What happens to the pressure of the blood as it travels against gravity in a standing person? The pressure weakens as does the water. 5. The baroreceptor reflex insures that the pressure of the blood entering the brain remains within defined limits, irrespective of body position. Under these circumstances, predict the blood pressure in the aorta of a standing person and a person who is lying flat on their back. The pressure will be greater in the aorta of the person who is standing than that of who is lying flat to try and combat gravity working against it. 6. If the baroreceptor reflex functions to maintain a constant pressure in the blood entering the brain, how does the circulatory system compensate for a person going from a lying to a standing position? Refer to the diagram in question #6 in Part III if necessary. It increases the heart rate while constricting the blood vessels to combat the differing blood pressure. 7. Do you wish to modify your diagnosis of Greg’s problem? Yes, instead of a brain injury he may have a problem with the mechanism responsible for maintaining the blood pressure delivered to his brain or within the sensors corresponding to the baroreceptor reflex itself. “I’ve Fallen Over and I Can’t Get Up” by Madern, Hood, Paul, & Stephens Page 8

NATIONAL CENTER FOR CASE STUDY TEACHING IN SCIENCE • Image in title block by Wikipedia user JonRidinger, http://commons.wikimedia.org/wiki/File:Roosevelt_Stadium_night_2.jpg, and used in accordance with the Creative Commons Attribution 3.0 Unported license. Case copyright held by th e National Center for Case Study Teaching in Science , University at Buff alo, State University of New York. Originally published January 5, 2012. Please see our usage guidelines , which outline our policy concerning permissible reproduction of this work. “I’ve Fallen Over and I Can’t Get Up” by Madern, Hood, Paul, & Stephens Page 10