Case Study 1: Disorders of Fluid, Electrolyte, and Acid-Base Balance

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Amanda is an 18-year-old with anorexia nervosa. She was recently admitted to an eating disorders clinic with a BMI of 13.9, and although she was a voluntary patient, she was reluctant about the treatment. She was convinced that she was overweight because her clothes felt tight on her. She complained that even her hands and feet were fat. One of her nurses explained that a protein in her blood was low. The nurse further explained that, as difficult as it may be to believe, eating a normal healthy diet would make the fat hands and feet go away.
What protein do you suspect the nurse was referring to? How would a deficiency in this protein contribute to edema?
What is the difference between the physiology of pitting and nonpitting edema?
Because of her weakened condition, Amanda was moved around the ward in a wheelchair when she was not on bed rest. How does this affect her edematous tissues?
Case Study 2: Respiratory Tract Infections, Neoplasms, and Childhood DisordersPatricia was called at work by a woman at the local day care center. She told Patricia to come and pick up her son because he was not feeling well. Her son, 3-year-old Marshall, had been feeling tired and achy when he woke up. While at daycare, his cheeks had become red, and he was warm to touch. He did not want to play with his friends, and by the time Patricia arrived, he was crying. Later that afternoon, Marshalls condition worsened. He had fever, chills, a sore throat, runny nose, and a dry hacking cough. Suspecting Marshall had influenza, Patricia wrapped him up and took him to the community health care clinic.
Why did Marshalls presentation lead Patricia to think he had influenza and not a cold? Why is it important to medically evaluate and diagnose a potential influenza infection?
Describe the pathophysiology of the influenza virus. Outline the properties of influenza A antigens that allow them to exert their effects in the host.
Marshall may be at risk of contracting secondary bacterial pneumonia. Why is this so? Explain why cyanosis may be a feature associated with pneumonia.
Case Study 3: Disorders of Ventilation and Gas ExchangeEmmanuel and his mother live in an urban community housing complex. The building is worn down and dirty from the urban dust, cockroaches, and mold. Emmanuel is 5 years of age and has suffered from asthma for the last 2 years. One evening, his mother poured him some milk and put him to bed. Shortly afterward, Emmanuel woke up wheezing and coughing. As he gasped for air, he became more and more anxious. His mother ran for his inhaler, but he was too upset and restless to use it. Emmanuels skin became moist with sweat, and as he began to tire, his wheezing became quieter. His mother called 911 and waited anxiously for the ambulance to arrive.
Emmanuel uses a corticosteroid inhaler for the management of his asthma. What is the mechanism of action of this drug? How is its action different from the 2-agonist inhalants?
Why does someone with severe asthma become physically fatigued during a prolonged attack? What are the physiologic events that occur during an attack?
One of the complications of respiratory fatigue is the development of hypercapnia. How does the body compensate for an increase in CO2? What are the effects of hypercapnia on the central nervous system?
Case Study 4: Disorders of Renal FunctionFred, a fit and healthy 44-year-old, was working outside one warm summer afternoon. When he returned home by the end of the day, his lower back felt sore and he felt nauseated. His wife made him dinner, but he was not hungry and chose to go to bed instead. Freds symptoms progressed, and soon he was rolling on the bed with excruciating pain. He said his back hurt as well as his stomach and groin area. The pain would ease off only to return a short while later, and when it did, Fred would begin to sweat and run to the bathroom to vomit. His wife became concerned and started the car. When his symptoms abated, she helped him into the car and rushed him to the hospital.
At the hospital, an abdominal radiograph showed the presence of renal calculi in Freds right ureter (urolithiasis). What is the mechanism of stone formation in the kidney? What is the role of citrate in the kidneys?
Why would the administration of calcium supplements be useful for a patient with calcium oxalate stones?
Hydronephrosis can be a complication of renal calculi. What is hydronephrosis? How does back pressure occur in a kidney, and what physiologic mechanism is responsible for nephron damage when back pressure is present?

Sample Solution

Protein Deficiency and Edema

The protein the nurse likely referred to is albumin. Albumin is a major protein in the blood that helps to maintain osmotic pressure. It prevents fluid from leaking out of blood vessels into the surrounding tissues.

A deficiency in albumin contributes to edema by reducing the osmotic pressure in the blood. This allows fluid to seep out of the blood vessels and accumulate in the tissues, causing swelling. This is particularly evident in areas with lower gravity, such as the hands and feet, leading to the perception of “fat” hands and feet.

Pitting vs. Non-pitting Edema

  • Pitting edema: This is when pressure applied to the swollen area leaves a dent. It occurs when excess fluid accumulates in the interstitial spaces. It’s often associated with conditions like heart failure, kidney disease, and protein deficiency.
  • Non-pitting edema: In this case, pressing on the swollen area doesn’t leave a dent. It’s usually caused by inflammation or lymphatic obstruction, where the fluid is thicker and doesn’t easily displace.

Effect of Wheelchair Immobilization on Edematous Tissues

Immobilization, especially in a sitting position, can worsen edema. This is because it reduces muscle contraction, which helps pump fluid back into the circulation. Additionally, the dependent position of the legs in a wheelchair can increase fluid accumulation in the lower extremities.

Case Study 2: Marshall and Influenza

Influenza vs. Common Cold

Marshall’s presentation with sudden onset of fever, chills, body aches, and a dry hacking cough is more suggestive of influenza than a common cold. The common cold typically has a gradual onset with milder symptoms and primarily affects the upper respiratory tract.

It’s crucial to medically evaluate and diagnose a potential influenza infection because:

  • Influenza can lead to severe complications like pneumonia, bronchitis, and even death.
  • Early diagnosis allows for timely antiviral treatment, which can reduce the severity and duration of illness.
  • Influenza can cause widespread outbreaks, and accurate diagnosis helps in public health surveillance and control measures.

Pathophysiology of Influenza Virus

Influenza is caused by an RNA virus that infects the respiratory tract. The virus binds to specific receptors on the surface of respiratory cells, enters the cell, and replicates. This leads to cell death and damage to the respiratory epithelium.

Influenza A antigens possess properties that contribute to their virulence:

  • Hemagglutinin: This protein allows the virus to bind to host cells and initiate infection.
  • Neuraminidase: This enzyme helps the virus to release new virus particles from infected cells and spread to other cells.
  • Antigenic shift and drift: These mechanisms allow the influenza virus to undergo rapid genetic changes, making it difficult for the immune system to recognize and fight off the infection.

Secondary Bacterial Pneumonia

Marshall is at risk of secondary bacterial pneumonia because the influenza virus damages the respiratory epithelium, creating a favorable environment for bacterial growth. Additionally, the weakened immune system caused by the viral infection makes the body more susceptible to bacterial infections.

Cyanosis is a bluish discoloration of the skin due to low oxygen levels in the blood. In pneumonia, it can occur due to impaired gas exchange caused by inflammation and fluid accumulation in the lungs.

 

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