Patho - chapter 3

increased capillary permeability

- Usually causes localized edema: May result from an inflammatory response or infection Histamines and other chemical mediators increase capillary permeability - Can also result from some bacterial toxins or large burn wounds and result in widespread edema

Capillary hydrostatic pressure (blood pressure)

facilitates the outward movement of water from the capillary to the interstitial space

The clinical manifestations and effects of edema may include the following:

Swelling Increase in body weight Functional impairment Pain Impairment of arterial circulation

Parathyroid hormone

Stimuli: Low plasma calcium Physiologic effects: increases resorption of bone; stimulates renal re-absorption of calcium; inhibits renal re-absorption of phosphate.

Which of the following processes describes the mechanism underlying the sodium-potassium pump?

Active transport The sodium-potassium pump transports sodium out of cells and potassium into cells by means of an active transport mechanism.

Calcium

Calcium is a major extracellular cation (Ca++) in the structure of bones and teeth, and used for muscle contraction and relaxation (including vascular smooth muscle), blood clotting, hormone secretion, cell receptor functions, and membrane stabilization. Concentrations are controlled by parathyroid hormone, vitamin D, and calcitonin.

Forces moving fluid from the capillaries into the interstitial compartment

Capillary hydrostatic pressure - Outward push of the vascular fluid against the capillary walls Interstitial oncotic pressure - Inward-pulling force of particles in the interstitial fluid

Forces moving fluid from the interstitial compartment into the capillaries

Capillary oncotic pressure - Inward-pulling force of particles in the vascular fluid Interstitial fluid hydrostatic pressure - Outward push of the interstitial fluid against the outside of the capillary walls

Isotonic Fluid Excess

Cause: Excessive administration of IV fluids Hypersecretion of aldosterone Drugs such as cortisone Renal failure Findings: Weight gain Decreased hematocrit Decreased plasma protein levels Distended neck veins Increase in BP Edema

Respiratory acidosis causes and findings

Causes: Decreased ventilation (inadequate respirations), which can be caused by overdose of sedatives, diseases of the central nervous system, weakness of respiratory muscle(s), or obstruction of the airway Findings: Breathlessness Restlessness Apprehension Lethargy Disorientation Muscle twitching Tremors Convulsions Coma

Hypomagnesemia develops when the serum magnesium level is < 1.5 mEq/L.

Causes: Malabsorption Malnutrition Alcoholism Overuse of loop diuretics Renal tubular dysfunction Findings: Neuromuscular hyperirritability Insomnia Personality changes Increased heart rate Cardiac arrhythmias

Hypophosphatemia develops when the serum phosphate level is < 2.0 mg/dL.

Causes: Malabsorption syndromes Diarrhea Excessive use of antacids Hyperparathyroidism Long-term alcohol abuse Refeeding syndromes Findings: Impaired neurologic function, including tremors, weak reflexes, paresthesia, confusion, and stupor Anorexia Dysphagia

Hypermagnesemia develops when the serum magnesium level is > 3.0 mEq/L.

Causes: Renal failure Excessive intake of magnesium-containing antacids Findings: Depresses neuromuscular function, including decreased reflexes, lethargy, and cardiac arrhythmias Nausea and vomiting

Metabolic acidosis Causes and findings

Causes: Shock Diabetic ketoacidosis Renal failure Diarrhea Findings: Headache Lethargy Kussmaul respirations (deep and rapid respirations; respiratory system blows off carbon dioxide to decrease carbonic acid) Nausea and anorexia Vomiting Diarrhea Coma Death

Hypercalcemia with total serum calcium concentrations exceeding 10.5 mg/dL can be caused by a number of diseases.

Causes: Uncontrolled release of calcium ions from malignant neoplasms that invade bone Hyperparathyroidism Immobility Increased intake of calcium caused by either excessive vitamin D or excess dietary calcium Increase in physiologically active calcium as occurs with acidosis Findings: Depressed neuromuscular activity, including muscle weakness, loss of muscle tone, lethargy, and stupor Anorexia, nausea, and constipation Interference with ADH in the kidneys, resulting in less absorption of water and polyuria Cardiac arrhythmias

Metabolic alkalosis Causes and Findings

Causes: Vomiting (loss of hydrochloric acid) Hyperaldosteronism Diuretics Excessive antacid intake Findings: Weakness Muscle cramps Hyperactive reflexes Tetany Confusion Convulsions Atrial tachycardia

Hypernatremic volume depletion

Causes: Water deprivation Loss of thirst Inability to swallow Diabetes insipidus Excessive urination Findings: Weight loss Weak pulses Increased heart rate Postural hypotension Excessive urination

Hypokalemia

Causes: Diarrhea Diuresis associated with certain diuretic drugs Excessive aldosterone or glucocorticoids in the body Decreased dietary intake Treatment of diabetic ketoacidosis with insulin Respiratory alkalosis Findings: Diarrhea Diuresis associated with certain diuretic drugs Excessive aldosterone or glucocorticoids in the body Decreased dietary intake Treatment of diabetic ketoacidosis with insulin Respiratory alkalosis

Hyperphosphatemia develops when the serum phosphate level is > 4.7 mg/dL.

Causes: Renal failure Cancer therapy Hypoparathyroidism Laxatives or enemas containing phosphates Findings: Impaired neurologic function, including tremors, weak reflexes, paresthesia, confusion, and stupor Anorexia Dysphagia

Hyperkalemia

Causes: Renal failure Deficit of aldosterone Use of "potassium-sparing" diuretic drugs Leakage of intracellular potassium into the ECF in patients with extensive tissue damage such as crush injuries or burns Displacement of potassium from cells by prolonged or severe acidosis Findings: Cardiac dysrhythmias that may progress to cardiac arrest Muscle weakness progressing to paralysis Fatigue Nausea Paresthesias Little or no urine output Decreased serum pH (acidosis)

Hypernatremic volume excess (serum sodium levels >147 mEq/L)

Causes: Excessive intake of sodium compared to water (rarely a result of dietary intake) Findings: Weakness Agitation Firm subcutaneous tissue Increased thirst Edema Elevated BP

antidiuretic hormone (ADH)

Stimuli: increased plasma osmolality, substantially decreased arterial blood pressure Physiologic effects: increases renal water re-absorption, vasoconstriction.

Isotonic Fluid Loss

Causes: Hemorrhage, Wound drainage Excessive sweating, diarrhea, vomiting Decreased fluid intake Findings: Weight loss Dryness of skin and mucous membranes Decreased skin turgor Decreased urine output Symptoms of hypovolemia (rapid HR, flattened neck veins, and normal or decreased BP, and in severe instances, hypovolemic shock)

A deficit of electrolytes in the ECF may be caused by:

Decreased electrolyte intake or absorption Shift of electrolytes from the ECF into the ICF Increased electrolyte excretion Abnormal loss of electrolytes

Which factor causes decrease plasma oncotic pressure?

Decreased plasma oncotic pressure is caused by diminished production of plasma albumin.

Which of the following is the largest fluid compartment in the body?

Intracellular Approximately two-thirds of the body's water is contained inside the cells. The extracellular fluid (interstitial and intravascular) accounts for the remaining third.

Edema

Edema is the excessive accumulation of fluid within the interstitial spaces. It is often a problem of fluid distribution and does not necessarily indicate a fluid excess. In some conditions, sequestered fluids can cause both edema and intravascular dehydration. The pathophysiologic process of edema is related to an increase in the forces favoring fluid filtration from the capillaries or lymphatic channels into the tissues. The four most common mechanisms are: Increased capillary hydrostatic pressure Decreased capillary oncotic pressure Increased capillary membrane permeability Lymphatic obstruction

If body potassium is depleted (hypokalemia), what state best describes the altered membrane potential of the cell?

Hyperpolarized When intracellular potassium concentrations are lower than normal, the cell becomes hyperpolarized. A neuron or muscle cell in this state is more difficult to excite because the membrane potential is now further away from threshold.

Increased capillary hydrostatic pressure

Increased capillary hydrostatic pressure can result from venous obstruction or sodium and water retention. Venous obstruction causes hydrostatic pressure to increase behind the obstruction, pushing fluid from the capillaries into the interstitial spaces. Venous blood clots, hepatic obstruction, right-sided heart failure, tight clothing around the extremities, and prolonged standing are common causes of venous obstruction. Right-sided congestive heart failure, renal failure, and cirrhosis of the liver are conditions associated with excessive sodium and water retention, which in turn cause volume overload, increased venous pressure, and edema. The volume of interstitial fluid exceeds the capacity of the lymphatics to return fluid to the vascular system.

An excess of electrolytes in the ECF may be caused by:

Increased electrolyte intake or absorption Shift of electrolytes from the ICF into the ECF Decreased electrolyte excretion

Types of edema

Localized—usually limited to the site of tissue injury, as in a sprained joint. Generalized—is manifested by a more uniform distribution of fluid in interstitial spaces throughout the body. Dependent fluid accumulates in gravity-dependent areas of the body; it might appear in the feet and legs when standing and in the sacral area and buttocks when supine.

Magnesium

Magnesium is a major intracellular cation (Mg++) that functions in enzymatic reactions and often interacts with calcium at the cellular level. About 50% of total body magnesium is stored in bone. Serum levels are linked to potassium and calcium levels and are regulated by the parathyroid hormone.

Metabolic acidosis definition

Metabolic acidosis is caused by an increase in noncarbonic acids (such as lactic acid, ketoacids, etc.) or a decrease in bicarbonate. It is clinically recognized as an abnormally low serum pH accompanied by an abnormally low bicarbonate level on an arterial blood gas (ABG).

Metabolic alkalosis definition

Metabolic alkalosis is an excessive loss of metabolic acid and an increase in bicarbonate. It is clinically recognized as an abnormally high serum pH accompanied by an abnormally high bicarbonate level on an arterial blood gas (ABG). Select the illustration to refer the pathologic sequence of events that occurs as a result of metabolic alkalosis.

Osmolality

Osmolality is the solute concentration when measured per kilogram of fluid A variety of electrolytes are needed for physiologic processes. For general clinical purposes, the number of electrolytes present in the body water determines to the greatest degree the osmolality (concentration) of the body water compartment. Osmolality refers to the proportion of solute to solvent, or, to put it another way, the amount of electrolytes compared with the volume of water in any compartment.

Factors that determine osmotic pressure

Osmotic pressure is the amount of hydrostatic pressure required to oppose the movement of water. Osmotic pressure is determined by the size of the molecules, the concentration gradient, and the permeability of the plasma membrane through which water is diffusing.

Phosphate

Phosphate ion (PO4-) is located primarily in the bone but circulates in the ICF and ECV. It acts as a buffer in acid-base regulation and provides energy for muscle contraction. Phosphate concentrations are controlled by parathyroid hormone, vitamin D, and calcitonin.

Which of the following electrolytes is found in the highest concentration in the intracellular fluid (ICF)?

Potassium Potassium is the major cation inside cells and plays an important role in maintaining resting membrane potential.

Atrial natriuretic hormone

Stimuli: increased volume in the cardiac atria. Physiologic effects: Increases renal sodium and water excretion

Potassium

Potassium (K+) is the major intracellular electrolyte and is found in most body fluids. The ICF concentration of K+ is about 150 to 160 mEq/L; the ECF concentration is about 3.5 to 5.0 mEq/L. Total body potassium content is about 4000 mEq, with most of it located in the cells. Daily dietary intake of potassium is 40 to 150 mEq/day, with an average of 1.5 mEq/kg body weight. Potassium balance is highly regulated because of its role in neuromuscular function. About 90% of dietary potassium is absorbed in the gastrointestinal tract. The increased serum K+ stimulates insulin, aldosterone, and epinephrine (β-adrenergic stimulation) secretion, which activates K+ transport into liver and muscle cells. Aldosterone also promotes renal excretion of K+ by the distal tubules, accounting for 90% to 95% of K+ excretion (see What's New? Potassium Intake, Hypertension and Stroke). The human kidneys cannot conserve potassium as carefully as they do sodium. Thus, the average adult loses about 40 to 80 mEq of potassium per 24 hours through renal excretion. Under normal conditions, the required potassium can be replaced if an individual follows a standard diet. In fact, as long as renal function is normal, the kidneys can excrete considerable amounts of ingested potassium. Only renal failure impairs potassium excretion, which can lead to dangerously elevated body potassium levels. On the other hand, if a patient with normal renal function cannot consume food or fluid, potassium replacement is a "must" in an intravenous or enteric feeding maintenance plan. Otherwise, potassium depletion will result in just a few days.

Respiratory acidosis Primary change, compensation, lab values

Primary change: pH - decreases PaCO2 - increases HCO3 - no change Compensation: Kidneys excrete more hydrogen ion and reabsorb more bicarbonate Lab values: PaC02 is high Compensated - PaCO2 is high, pH is normalized because bicarbonate levels are high Uncompensated - PaCO2 is high, pH < 7.33 and no change in bicarbonate

Metabolic acidosis Primary change, compensation and lab values

Primary change: pH - decreases PaCO2 - no change HCO3 - decreases Compensation: Respiratory system-can increase pH by increasing the rate and/or depth of respiration. One identifiable compensatory breathing pattern is termed Kussmaul respirations, which is an involuntary deep and rapid breathing pattern that may be seen in significant metabolic acidosis. Lab values: Compensated - bicarbonate is low, pH is normalized because PaCO2 is low Uncompensated - bicarbonate is low, pH < 7.33 and no change in PaCO2

Metabolic alkalosis Primary change, compensation and findings

Primary change: pH - decreases PaCO2 - no change HCO3 - increases Compensation: Shallow, slow respirations (respiratory systems holding on to carbonic acid) Kidneys excrete less acid and decrease bicarbonate reabsorption Findings: Elevated bicarbonate (HCO3) Compensated - bicarbonate is high, pH is normalized because PCO2 is high Uncompensated - bicarbonate is high, pH > 7.47 , and no change in PaCO2

Respiratory acidosis definition

Respiratory acidosis is an increase in hydrogen ions that results from an increase in carbon dioxide levels. It is clinically recognized as an abnormally low serum pH accompanied by an abnormally high carbon dioxide level on an arterial blood gas (ABG).

Aldosterone

Stimuli: Angiotensin II, increased plasma potassium. Physiologic effects: Increases renal sodium and water re-absorption; increases renal excretion of potassium and hydrogen ions.

Compensatory Mechanisms for Acid-Base Imbalances

Respiratory system - increases or decreases carbon dioxide by changing the rate and/or depth of respirations. Renal system - increases or decreases the amount of bicarbonate that is available in the blood to bind with hydrogen ions

Aldosterone

Responsible for sodium and potassium regulation Aldosterone indirectly regulates water balance through its regulation of sodium. Serum aldosterone is manufactured as a result of a sequence of hormonal activities that involve the vascular system, heart, and kidney (Renin-Angiotensin-Aldosterone system or RAA). It acts primarily to control the amount of sodium that is conserved or excreted by the kidney. Serum aldosterone levels will rise if the serum becomes hypotonic due to a decrease in serum sodium levels, or if hydrostatic pressure in the glomeruli of the kidneys drop due to a decrease in blood pressure or blood volume. In contrast, an increase in vascular compartment volume, sodium intake, or blood pressure can lower serum aldosterone concentration, resulting in enhanced sodium excretion by the kidney. This response is mediated by a network of volume receptors that are located throughout the cardiac and vascular and renal systems. Aldosterone also regulates the potassium content of the body. However, it does so in a way that is reciprocal or opposite to that of sodium regulation. That is, increased levels of aldosterone result in sodium conservation and potassium excretion, whereas low aldosterone levels result in potassium conservation and sodium excretion.

Natriuretic hormones

Responsible for stimulating water and sodium excretion When the volume receptors of the cardiovascular system detect an increase in vascular compartment volume, natriuretic hormones (Atrial natriuretic peptide [ANP], brain natriuretic peptide [BNP], C-type natriuretic peptide, and urodilatin) are released from manufacturing sites within the heart and brain. These hormones then act on the kidney to increase the excretion of both sodium and water, as well as causing a dilation in the vasculature. Under the opposite condition of dehydration, when the body water volume is low, levels of natriuretic hormone become undetectable.

Antidiuretic hormone (ADH)

Responsible for water conservation ADH is manufactured in the hypothalamus of the brain and stored in the posterior section of the pituitary gland. Its release is regulated on a minute-to-minute basis by a network of osmoreceptors located throughout the vascular system that sense when body fluids vary from an isotonic state. ADH is released when serum Na+ concentrations are elevated, or if the serum osmolarity is elevated. ADH increases the release of H2o from the renal tubules into the renal capillary network, thereby increasing total body water.

Calcitonin

Stimuli: High plasma calcium Physiologic effects: Inhibits osteoclasts in the bone

Which clients are at risk for hypernatremia?

The elderly

Osmosis

The movement of fluid from an area of lower solute concentration (low osmolality) to an area of higher solute concentration (high osmolality) across a semipermeable membrane.

Osmosis describes the movement of:

Water By definition, osmosis describes the movement of water from an area of high concentration of water to low concentration of water.

Difference between osmotic and oncotic pressures

Whereas osmotic pressure is determined by the electrolyte concentration, the term oncotic pressure relates to the protein content of the intravascular space The body maintains a specific osmotic pressure between intracellular and extracellular ion concentrations via electrolyte levels, and a specific oncotic pressure between intravascular and interstitial spaces via oncotic pressure. These two mechanisms work simultaneously to maintain a homeostasis in the body compartments.

oncotic pressure

Whereas osmotic pressure is determined by the electrolyte concentration, the term oncotic pressure relates to the protein content of the intravascular space. As described previously, the major contributor to the protein levels is albumin. Proteins in general, and albumin in specific are large molecules and therefore have a significant amount of "pull" or "push" in the intravascular space. If the intravascular space has an abundance of protein, fluid will shift toward the intravascular space. If the intravascular space has a protein deficiency, fluid will shift toward the interstitial space.

Active mediated transport is used to transport molecules:

across a membrane. Active mediated transport is used to transport molecules across a membrane from an area of low concentration to high concentration of solute.

Water moves freely by diffusion through the lipid bilayer cell membrane and through:

auquaporins. Water moves freely by diffusion through the lipid bilayer cell membrane and aquaporins.

Hypocalcemia occurs when serum total calcium concentrations are less than 9.0 mg/dL and ionized levels are less than 5.5 mg/dL.

causes: Hypoparathyroidism Malabsorption of dietary calcium Deficient serum albumin Increase in physiologically inactive calcium as occurs with alkalosis Lack of vitamin D Chronic renal failure Large blood transfusions Findings: Increased neuromuscular stimulation Circumoral numbness or tingling Muscle spasm Chvostek sign Trousseau sign Arrhythmias Intestinal cramping

interstitial hydrostatic pressure

facilitates the inward movement of water from the interstitial space into the capillary

Serum pH

he concentration of hydrogen ions (H+) in the body is tightly regulated within a very narrow range to maintain cell homeostasis. The H+ concentration is expressed in terms of its pH (potential [or power of] hydrogen). The pH is a mathematical value that clinically indicates the acidity or alkalinity of a fluid such as blood or urine. The more hydrogen ions present in a solution, the more acidic is the solution. The pH maintains an inverse relationship with the amount of H+ present. Therefore, as H+ decreases, pH increases (becomes more alkaline); as H+ increases, pH decreases (becomes more acidic). The following points summarize this relationship: Arterial blood pH < 7.4 = more hydrogen ions, which leads to acidosis (more acidic) Arterial blood pH > 7.4 = less hydrogen ions, which leads to alkalosis (more basic) A normal human arterial blood pH is considered 7.40; however, pH is a dynamic value that normally ranges from 7.35 to 7.45. Death usually results if arterial pH is below 6.8 or above 7.8 for a long period of time. The body has a natural tendency toward acidosis because cell metabolism is constantly producing two types of acids: Volatile - carbonic acid (H2CO3) which is eliminated by the lungs as carbon dioxide (CO2) gas Nonvolatile - eliminated by the kidneys, including metabolic acids such as lactic acid, ketoacids, sulfuric acid and phosphoric acid

The inside of the cell is more _______ charged than the outside.

negatively

lymphatic obstruction

occurs when the lymphatic channels are blocked because of infection or tumor. Proteins and fluids are not reabsorbed and accumulate in the interstitial space causing lymphedma.

osmolarity

osmolarity is the solute concentration when measured per liter of fluid.

interstitial oncotic pressure

osmotically attracts water from the capillary into the interstitial space

Capillary (plasma) oncotic pressure

osmotically attracts water from the interstitial space back into the capillary

What is the client with edema at risk of?

pressure ulcers

Plasma oncotic (colloid osmotid) pressure is maintained primarily by the quantity of plasma:

proteins. Plasma oncotic pressure is maintained by the presence of plasma proteins, such as albumin.

decreased plasma oncotic pressure

results from losses or diminished production of plasma albumin

Osmolarity measures:

the concentration of solute per liter of solution. Osmolarity measures the number of milliosmoles per liter of solution, whereas osmolality measures the number of milliosmoles per kilogram of water.