Pathophysiology Exam #4

Hypoxemia

* low arterial blood O2
* can lead to hypoxia (low tissue O2)
* Presentations:
* uncommonly: can be blue in color (cyanotic)

PaO2

* arterial O2
* invasive; must be taken through ABG
* Normal range: 80-100 mmHg
* measure of actual arterial pressure of O2 in the blood
* Hypoxemia =

Pulse Ox (Pulse Oximetry; SpO2)

* non-invasive; small tool placed on finger
* % O2 saturation
* Normal Range: 95-100%
* Hypoxemia:

T/F: PaO2 and SpO2 are the same thing?

False:

* PaO2 is the actual measure of O2 in the blood
* SpO2 is the % of O2 saturation

SpO2 and PaO2 calculations

For every 1% drop in SpO2, you will drop 4 mmHg for PaO2

\
100% SpO2 = 100 mmHg PaO2

99% SpO2 = 96 mmHg PaO2

98% SpO2 = 92 mmHg PaO2

97% SpO2 = 88 mmHg PaO2

96% SpO2 = 84 mmHg PaO2

95% SpO2 = 80 mmHg PaO2

SpO2 at 80-89% and PaO2

For every 1% drop in SpO2, the PaO2 drops 1.5 mmHg

\
89% SpO2 = 58.5 mmHg PaO2

88% SpO2 = 57 mmHg PaO2

87% SpO2 = 55.5 mmHg PaO2

86% SpO2 = 54 mmHg PaO2

85% SpO2 = 52.5 mmHg PaO2

84% SpO2 = 51 mmHg PaO2

83% SpO2 = 49.5 mmHg PaO2

82% SpO2 = 48 mmHg PaO2

81% SpO2 = 46.5 mmHg PaO2

80% SpO2 = 45 mmHg PaO2

SpO2

For every 1% below 80 the PaO2 will be half the SpO2 value

\
79% SpO2 = 39.5 mmHg PaO2

78% SpO2 = 39 mmHg PaO2

77% SpO2 = 38.5 mmHg PaO2

76% SpO2 = 38 mmHg PaO2

75% SpO2 = 37.5 mmHg PaO2

and so on

Causes / How someone becomes hypoxemic

* ventilation abnormality
* diffusion abnormality
* pulmonary respiration
* perfusion abnormality
* problem getting blood supply to the lungs
* perfusion symbol = Q
* PE
* V/Q scan to find PE
* FiO2
* fraction of inspired O2
* how much oxygen is in the air you’re breathing in
* least common reason
* EX: smoke inhalation, high altitude

Pneumonia

* infected lung tissue
* bacterial, viral, fungal causes
* fungal being most uncommon
* bacterial is more severe
* viral is usually self-limited; can be problematic, superinfection (infection on top of viral infection)

\
* alveoli are occupied with cellular debris, fluids, blood, pus, or whatever
* the air sacs (alveoli) are filled rather than hollow as they should be
* can produce hypoxemia; poor oxygenation
* ventilation problem (alveoli are occupied with gunk and no air can get in)
* diffusion problem (pulmonary respiration)
* should be treated very quickly to prevent pneumonia from progressing to further sections or occupying more area of the lung

Categorizations of Penumonia

* lobar pneumonia
* entire lobe
* segmental
* entire segment
* sub segmental
* partial segment

\
* can also be categorized as Unilateral (one lung) or Bilateral (both lungs)

Asthma

* acute respiratory disorder
* sudden onset, acute attacks
* respiratory function is relatively normal until an acute attack
* ventilation and diffusion problems (mainly ventilation)
* most cases are mild to moderate; can be severe
* can become hypoxemic:
* ventilation
* diffusion problem (airways are constricted)

Manifestations of Asthma and Treatment

* Bronchoconstriction
* airway wall inflammation

\
Treatment:

* Bronchodilators: rescue agent; rapid-acting bronchodilator (Albuterol)
* Given in acute attacks to prevent the attack from progressing
* prophylactic given as a slow-acting drug to help prevent future attacks
* Anti-inflammatory drugs: corticosteroids; Advair

Chronic Obstructive Pulmonary Disease (COPD)

* chronic issue (always have it; never really have normal function)
* obstructed air movement into and out of the lungs
* 2 disorders:
* chronic bronchitis
* airway wall inflammation
* typically produce mucous, chronic productive cough
* emphysema
* alveolar wall destruction
* lung hyperinflation: lungs trap a lot of air; loss of pulmonary capillaries and less area for exchange
* chest X-ray will show significant hyperinflation of lungs; can look barrel-chested
* both can develop hypoxemia
* These are both, almost always, associated with long-term smoking history

Main / Driving force for respiration in COPD

* CO2 drive: if levels go up in arterial blood, you breathe at a higher rate and vice versa
* COPD patients have hypercapnia (high PaO2)
* Hypoxemic drive: drop in PaO2
* this is what stimulates COPD patients to breathe
* Respiratory acidosis; because of hypercapnia
* Patients frequently get supplemental oxygen
* can be a problem if they get too much
* Raising the PaO2 values above a certain threshold and this can cause them to stop breathing; gets rid of the hypoxemic drive
* To prevent this, they typically get 2-3 L/min

Pneumothorax (PTX)

* air between lungs and chest wall
* there should never be any air between the chest wall and the lungs
* air leaks from the lungs
* air from chest wall defect
* Hypoxemia: ventilation impaired

\
* Classified as:
* Open
* chest wall defect where atmospheric pressure and interthoracic pressure are equal
* Tension
* air accumulated and the interthoracic pressure continues to rise
* potentially life threatening; the pressure is so great that it begins pushing all the contents from the side of the chest where it is occurring and to the other side of the chest (neither lung can ventilate now; causes good lung to collapse)
* can place a chest tube or any hollow tube to release the pressure; must be done emergently to prevent circulatory collapse

Acute Respiratory Distress Syndrome (ARDS)

* severe hypoxemia (refractory hypoxemia)
* severe pulmonary edema
* inflammatory process taking place
* capillaries become really leaky

\
* Problematic because:
* diffuse bilateral process (widespread involving both lungs)
* ALL alveoli are full of fluid, meaning both lungs are full and can’t ventilate properly, can’t diffuse
* can go into multiple organ failure
* will place patients on positive pressure supplemental oxygen; forces oxygen in

\
* Underlying causes: 2 most common
* sepsis
* multiple trauma (traumatic event with multiple injuries)
* Treatment:
* pressor agents, treat underlying causes, positive pressure O2, diuretics to help get a little excess fluid off (can’t get it out of alveoli with diuretics)

Urinary System

* kidneys More proximal
* produce urine / EPO
* EPO: stimulated RBC production
* Ureter
* drain urine from kidney to bladder
* Urinary bladder
* collects urine until full
* Urethra More distal
* drains bladder

\
* Any urinary disorder is cause by any of these components malfunctioning
* Blood flow drives filtration / urine production

Reasons for Urinary Disorders

* reduced renal perfusion (blood flow; also written as Q)
* CHF, MI
* Renal artery stenosis (narrowing)
* renal arteries come from abdominal artery
* direct injury
* trauma
* infection
* cancer
* toxic
* DM
* HTN (poorly controlled)
* Obstruction (trouble draining)
* stones (internal / external)
* compression (tumor) internal / external

Indications of declining renal function

* Blood Urea Nitrogen (B.U.N)
* measure of nitrogenous compounds in blood
* least reliable
* high protein intake can raise these values with normal renal function
* Creatinine
* Normal Values:

Acute Kidney Injury (AKI)

* __rapid__ decline in renal function
* Classified as:
* Prerenal
* AKI caused by reduced renal perfusion (before the kidney)
* Hypovolemia
* bleeding, dehydration
* CHF, MI
* Intrinsic / Intrarenal
* inside kidney
* direct injury
* trauma, infection, toxic, DM, cancer
* Obstructive / Post Renal
* stones
* BPH (benign prostatic hyperplasia)
* Tumor compression

\
* AKI can be reversed

Signs / Symptoms of AKI

* oliguria
* abnormally low urine output
* Extremity edema
* upper or lower
* kidneys are functioning properly, therefore fluids are accumulating
* Fatigue
* Confusion
* Seizure

Chronic Kidney Disease (CKD)

* either kidney damage OR GFR

Signs / Symptoms of CKD

* oliguria
* extremity edema
* fatigue
* confusion
* seizures
* uremic frost
* forming crystals of urea on their skin (looks like a pale yellow/whiteish salt on the skin)
* Pruritis
* skin becomes itchy

\
Most common causes of CKD:

* poorly controlled DM
* poorly controlled HTN

Hematuria

* blood in the urine
* categorized as:
* microscopic
* only seen under microscope
* gross
* can be seen with the naked eye
* blood can come from __any__ part of the urinary tract
* kidneys, ureters, urinary bladder, urethra

Urinary Tract Infections (UTIs)

* can involve any part of the urinary system
* kidneys, ureters, urinary bladder (most commonly; cystitis), urethra

\
* Presentations:
* dysuria
* painful urination; burns
* frequency
* often needing to go
* urgency
* overwhelming need to go
* cloudy urine
* normal is a light straw yellow color and transparent
* hematura

\
Females are about 5x more likely to develop UTIs due to anatomical differences

Elderly adults tend to present differently with UTIs:

* Psychological changes
* altered mental status
* confusion
* irritability
* infection can reside and spread over time
* UTIs → pyelonephritis → urosepsis

\
MOST UTI infections will get treated before it ever reaches pyelonephritis or urosepsis

UTI classifications

* Uncomplicated UTI
* occurs in someone with no underlying medical conditions or predisposed conditions to UTIs
* Healthy 22 y/o female presents with UTI
* Complicated UTI
* occurs in someone with underlying disease process or underlying anatomical abnormality with increased risk of developing UTI
* Patient with DM
* Pregnant female
* Indwelling foley catheter

Nephrolithiasis and Ureterolithiasis

* Nephrolithiasis
* kidney stones
* all stones form in the kidneys and then migrate to other parts of the tract
* Ureterolithiasis
* ureteral stones
* stones formed in kidneys but migrated

\
Renal or Ureteral Calculi

Most stones are Ca2+ oxalate (not test material)

Classic presentation of stones

* __Excruciating__ pain
* hematuria
* frequently gross hematuria
* nausea and vomiting
* usually from pain
* stones can (not always) cause rost renal / obstructive AKI
* kidneys are producing urine but can’t drain so the collecting system dilates and swells full so the functional area of the kidney is minimized to very little
* hydronephrosis

GI tract pathways

GI Tract: mouth → anus

Upper GI Tract (UGI)

* start at esophagus through the duodenum (first / most proximal part of small intestine)

Lower GI tract (LGI)

* jejunum through the anus
* ileum, all of large intestine, anus

\
Accessory Organs

* liver, gallbladder, pancreas, salivary glands, etc

GI Bleeding

* can be upper or lower
* typically, UGI bleeds are more brisk / bleed faster than LGI bleeds
* can bleed out (exsanguinate) from UGI bleeds

\
Characterized as:

* hematemesis
* vomiting blood (blood has been digested by some stomach acids and looks like coffee grounds)
* coffee ground emesis
* almost always associated with UGI bleeds
* Hematochezia
* bright red / maroon blood in the stool
* BRBPR (bright red blood per rectum)
* tends to be LGI and less commonly UGI
* Melena
* black, tarry, foul smelling stool
* most often associated with UGI bleeds; sometimes LGI

\
* Occult bleeds:
* patient is unaware of it; asymptomatic
* slow, not visible to the naked eye

Pancreatitis

* inflammation of the pancreas
* “autodigestion” of pancreas
* pancreatic enzymes flood pancreas and start to digest the organ
* pancreas has endocrine and exocrine functions
* exocrine: digestive secretions; released into the duodenum

\
Most common causes:

* long term ETOH abuse
* gallstones

\
Presentations:

many are non-specific

* abdominal pain (most common finding)
* sudden onset and then becomes more consistent
* radiates to the back
* Nausea / Vomiting
* Anorexia
* loss of appetite

Cholecystitis

* inflammation of the gallbladder
* Most common cause:
* gallstones blocking the cystic duct
* cystic duct: allows bile to enter and exit the gallbladder
* cholelithiasis: gallstones
* Presentations:
* starts with epigastric pain that migrates to the RUQ (most common finding)
* RUQ: right upper abdominal quadrant
* RUQ pain can also radiate to the Right shoulder
* epigastric: pain that is localized to the region of the upper abdomen immediately below ribs
* Nausea / Vomiting
* Anorexia
* loss of appetite
* Tests to run:
* Patient will have a + Murphy’s sign
* deep breath in and Dr. presses on abdomen (inflamed gallbladder will hit their hand and causes pain)
* Intervention:
* surgery
* cholecystectomy

Appendicitis

* Location of appendix: RLQ; appendage off the cecum
* inflammation of the appendix
* clinical emergency
* risk of rupture and other ensuing issues
* periumbilical pain that migrates to RLQ
* Nausea / Vomiting
* vomiting almost always follows onset of pain
* Anorexia
* loss of appetite
* Only about half present with normal presentations

Inflammatory Bowel Disease (IBD)

Characterized as 2 Diseases:

* Crohn’s Disease (CD)
* Ulcerative Colitis (UC)

\
* Thought to be some sort of auto-immune disease
* body identifies parts of the GI tract and attacks it

\
* TX:
* anti-inflammatories
* Biologic agents: Humira

Crohn’s Disease (CD)

* occurs at any point in the GI tract
* mouth to anus
* most common location: ileum (last part of small intestine)
* rectum is usually spared
* Transmural
* lesions affect entire thickness of the wall
* “Skip” lesions
* lesions in random spots between normal spots of GI tract
* Not surgically curable
* development of fistulas, abscesses
* Fistula: draining tract forms between GI tract and some other organ / bowel

Ulcerative Colitis (UC)

* occurs only in the colon
* rectum is __always__ affects
* mucosa
* inner layer of the wall if affected
* lesions are continuous
* surgically curable
* will take out entire colon; not just diseased segment to prevent recurrence
* no development of fistulas
* colon cancer risk is significantly higher

Constipation

* Fewer than 3 bowel movements per week __and__ difficult passage of stool

\
Causes:

* Originating within the colon
* tumor
* obstruction of large intestine
* compression of large intestine
* chronic laxative abuse
* colon becomes immune and stops working properly
* originating outside the colon
* poor dietary fiber and water intake
* certain drugs; opioids (morphine, Percocet, Dilaudid)

Obstipation

* no bowel movements
* most severe form of constipation
* fecal impaction (rock-solid stool)
* more common in elderly
* causes abdominal distention
* sometimes to the point of bowel rupture

Diarrhea

* more frequent bowel movements and stool tends to be loose or watery
* Causes:
* infectious
* bacterial
* viral
* medications
* medical conditions
* cancers
* lots of things can cause it
* Acute
* self-limited (runs its course and resolves)
* lasts no longer than 14 days
* Chronic
* lasts longer than 14 days

\
* Complications presenting from diarrhea (acute or chronic)
* dehydration
* severe dehydration from diarrhea can lead to hypovolemic shock; uncommon, especially in the developed world
* metabolic alkalosis
* Not always necessary to treat
* if infectious, let it run its course unless it becomes intolerable