Understanding AIDS, Renal Pathophysiology, and Metabolic Stress

Posted on Nov 29, 2024 in Biology

AIDS and HIV Infection

What is AIDS?

AIDS, a disease caused by HIV, manifests after infection with the human immunodeficiency virus (HIV).

  • Syndrome: A group of signs and symptoms characterizing a disease.
  • Immunodeficiency: The body’s inability to defend against microorganisms.
  • Acquired: Unlike other immunodeficiencies, AIDS is not congenital but caused by an external factor.

Etiologic Agent: HIV

HIV is a retrovirus (an RNA virus that replicates via a DNA intermediate). It’s fragile and easily inactivated by heat, sodium hypochlorite, glutaraldehyde, alcohol, and hydrogen peroxide. Its extreme genetic variability allows it to mutate readily.

Stages of HIV Infection

  • Acute Infection: Occurs 2-3 weeks post-exposure in 50-90% of patients. Symptoms range from cold-like to infectious mononucleosis (fever, pharyngitis, myalgia). This phase is self-limiting (1-2 weeks).
  • Asymptomatic Phase: Averages 7-10 years, with fluctuating viral levels.
  • Symptomatic Phase: Manifests as constitutional symptoms (prolonged fever, chronic diarrhea, weight loss) due to immunodeficiency.
  • AIDS: The most advanced stage, characterized by serious opportunistic infections or cancers.

Transmission

HIV transmits through blood, semen, and vaginal fluids. Unprotected sex and direct blood contact are major risk factors.

  • Incubation Period: 5-30 days between infection and acute phase symptoms.
  • Latency Period: 3-10 years (median) between infection and AIDS without antiretroviral drugs.
  • Period of Communicability: HIV is transmissible at all stages of infection, with risk proportional to viremia.

Renal Pathophysiology

Kidney Structure and Function

Each kidney contains about 1 million nephrons (Bowman’s capsule, glomeruli, proximal convoluted tubule, loop of Henle, distal tubule, and collecting duct). Kidney functions include:

  • Maintaining fluid, electrolyte, and solute balance.
  • Eliminating metabolic waste.
  • Regulating electrolyte balance, acid-base balance, osmolarity, and fluid volume.
  • Excreting exogenous substances.
  • Producing hormones (erythropoietin, renin, vitamin D).
  • Producing urine.

Renal Syndromes

  • Nephrotic Syndrome: Characterized by glomerular protein loss, often linked to systemic diseases (diabetes, lupus, amyloidosis) or kidney diseases (minimal change disease, membranous nephropathy, focal glomerulosclerosis, membranoproliferative glomerulonephritis). Leads to hypoalbuminemia, edema, hypercholesterolemia, hypercoagulability, and abnormal bone metabolism.
  • Nephritic Syndrome: Inflammation of glomerular capillary loops, often stemming from streptococcal infection. Causes acute glomerulonephritis (sudden onset, short duration, good prognosis) or chronic nephritic syndrome. Symptoms: Hematuria, hypertension, oliguria, azotemia, mild proteinuria, and red blood cell casts.

Renal Failure

  • Acute Renal Failure: Sudden loss of renal function, causing nitrogenous waste accumulation. Causes include decreased blood supply, urine flow obstruction, and kidney damage.
  • Chronic Renal Failure: Slow, progressive, irreversible loss of renal function. Risk factors include hypertension, diabetes, chronic glomerulonephritis, and family history.

Classification and Etiology of Renal Failure

  • Acute Renal Failure:
    • Pre-renal: Hypovolemia, decreased cardiac output, vasodilation, vasoconstriction, drugs.
    • Post-renal: Bilateral ureter obstruction, bladder obstruction, urethral obstruction.
    • Intrinsic renal: Hemodynamic, nephrotoxic, vascular, glomerular diseases, acute interstitial nephritis.
  • Chronic Renal Failure:
    • Stage 1: Normal GFR (>90 ml/min).
    • Stage 2 (Mild): GFR 60-89 ml/min.
    • Stage 3 (Moderate): GFR 30-59 ml/min.
    • Stage 4 (Severe): GFR 15-29 ml/min.
    • Stage 5 (End-stage): GFR <15 ml/min.

Signs and Symptoms of Renal Disease

Discolored urine, painful urination, frequent urination, nocturia, edema, back pain, hypertension, anemia, weakness, nausea, and vomiting.

Kidney Stones (Nephrolithiasis)

Kidney stone formation is a complex process influenced by diet (high protein, salt, carbohydrates).

Risk Factors

Male sex, young age, urinary tract abnormalities, warm climate, dietary factors, metabolic disorders, endocrine disorders, urinary pH changes, low urine output, immobilization, and lithogenic drugs.

Major Components

  • Calcium: Increased urinary or blood calcium.
  • Magnesium: Low urinary magnesium enhances stone formation.
  • Oxalate: Present in calcium oxalate stones.
  • Cystine: Low solubility leads to supersaturation and stone formation.
  • Uric acid
  • Citrate: Low excretion (<450mg/day) is a risk factor.

Complications

Urinary tract infections, urinary obstruction, chronic renal failure, hypertension, surgical complications, and lithotripsy complications.

Neoplasms

Tumor Growth and Cancer

Neoplasms are abnormal tissue proliferations that grow uncontrollably (tumors). Cancer is a malignant neoplasm that can arise in any organ (common sites: prostate in men, breast in women).

Oncogenes

Altered genes (oncogenes) promote the transformation of normal cells and induce tumor formation.

Antineoplastic Agents

  • Physical Agents: Radiant energy and heat.
  • Chemical Agents: Dyes (aniline), smoking.
  • Biological Agents: Viruses and bacteria.

Types of Neoplasms

  • Benign Neoplasms: Well-differentiated, slow-growing tumors that grow by expansion and are encapsulated. They are not usually fatal unless they disrupt vital functions.
  • Malignant Neoplasms: Poorly differentiated, rapidly growing tumors that invade tissues, metastasize, and cause death.

Metabolic Stress, Sepsis, and Trauma

Metabolic Stress

A pathological process resulting from the body’s reaction to external forces and abnormal conditions that disrupt homeostasis.

Sepsis

A systemic response to severe infection. Sepsis is present if systemic inflammatory response syndrome (SIRS) is triggered by infection.

SIRS

Two or more of the following: Temperature >38°C or <36°C, heart rate >90 bpm, respiratory rate >20/min or PaCO2 <32 mmHg, WBC >12,000/mm3 or <4,000/mm3, or >10% immature forms.

Severe Sepsis and Septic Shock

  • Severe Sepsis: Organ dysfunction, hypoperfusion, or hypotension; may include lactic acidosis, oliguria, or altered consciousness.
  • Septic Shock: Hypotension despite fluid resuscitation, with perfusion abnormalities.

Multiple Organ Dysfunction Syndrome (MODS)

Altered organ function in acutely ill patients, requiring intervention to maintain homeostasis.

Risk Factors for Sepsis

AIDS, protein-energy malnutrition, alcoholism, neoplasms, invasive procedures, immunosuppressants.

Clinical Manifestations of Sepsis

Fever, chills, anorexia, myalgia, tachycardia, tachypnea, hypotension, oliguria, irritability, and lethargy.

Treatment of Sepsis

Antimicrobial therapy and supportive care (fluid replacement, vasoactive drugs, nutritional support, oxygen, monitoring, dialysis).

Trauma

Injuries caused by external agents. Leading preventable cause of death (burns, car crashes, falls, etc.).

Traumatic Brain Injury (TBI)

Acute or chronic brain injury. Clinical manifestations depend on the injury’s nature. Diffuse TBI is often associated with diffuse axonal injury or coma. Localized lesions may cause neurobehavioral changes, hemiparesis, or other focal neurological deficits.

Primary vs. Secondary TBI

  • Primary: Direct injury.
  • Secondary: Indirect effects or complications.

Patients are hypermetabolic and catabolic, with increased catecholamine and cortisol release. This leads to lean body mass loss and immunosuppression.

TBI Rating Scales

Glasgow Coma Scale, post-traumatic amnesia duration, Glasgow Outcome Scale.

Burns

Injury caused by physical agents (thermal, electrical, radiation, chemical).

Burn Grades

  • Grade 1: Superficial, redness, swelling, mild pain.
  • Grade 2: Deeper, blisters, pain, swelling.
  • Grade 3: Full-thickness, charring, little to no pain.

Burns cause severe trauma, hypermetabolism, hypercatabolism, protein loss, increased nitrogen excretion, infection susceptibility, bowel changes, and anorexia.

Metabolic Response to Stress

Involves most metabolic pathways, characterized by increased metabolism, lean body mass loss, skeletal muscle loss, and negative nitrogen balance.