chapter 2: fluids, electrolytes, and acid-bases

metabolic acidosis

associated with a decrease in serum bicarbonate resulting from: - excessive loss of bicarbonate ions, for example from diarrhea - increased utilization of serum bicarbonate to buffer increased acids until kidneys can remove acids - renal disease or failure - decompensated metabolic acidosis, which may develop when an additional factor interferes with compensation.

antidiuretic hormone (ADH)

controls the amount of fluid leaving the body in the urine, ADH promotes reabsorption of water into the blood from the kidney tubules

aldosterone

hormone which determines the reabsorption of both sodium ions and water from the kidney tubules, these hormones conserve more fluid when there is a fluid deficit in the body

eight effects of edema

- a local area of swelling may be visible and may be very pale or red in color, depending on the cause - /pitting/ edema occurs in the presence of excess interstitial fluid, which moves aside when firm pressure is applied by the fingers. A depression or "pit" remains after the finger is removed. - increase in body weight (this may indicate a problem before there are any other visible signs) - functional impairment due to edema, for example when it restricts the range of motion of joints. edema around the heart or lungs impairs movement and function of these organs. - pain may occur if edema exerts pressure on the nerves locally - with sustained edema the arterial circulation may be impaired. - in dental practice, tissues become swollen, dentures don't fit, and sores develop that are slow to heal and become infected because blow flow to gingival tissue is impaired. - edematous tissue in the skin is very susceptible to tissue breakdown from pressure, abrasion, and external chemicals.

respiratory alkalosis (doesn't occur as often as acidosis)

- results from hyperventilation, usually caused by anxiety, high fever, or an overdose of aspirin. - stress related alkalosis may develop rapidly.

seven causes of dehydration

- vomiting - diarrhea - excessive sweating - diabetic ketoacidosis - insufficient water intake - drainage or suction - use of concentrated infant formula

four causes of edema & how each of results in accumulation of fluid in the extracellular compartment

1. increased capillary hydrostatic pressure, forcing excessive amounts of fluid out and preventing return of fluid from the interstitial compartment 2. loss of plasma proteins, reducing plasma osmotic pressure 3. obstruction of lymphatic circulation, restricting the return of excess fluid and protein to the general circulation 4. increased capillary permeability -- as in inflammation, resulting in fluid and protein movement into the interstitial compartment

Define edema

An excessive amount of fluid in the interstitial compartment, which causes swelling or enlargement of the tissues. Edema may be localized in one area or generalized throughout the body. Depending on the type of tissue and the area of the body, edema may be highly visible or relatively invisible, or not relatively reflect the amount of fluid hidden in the area. Prolonged edema interferes with venous return, arterial circulation, and cell function in the affected area.

Potassium Imbalances: hypokalemia & hyperkalemia

HYPOKALEMIA - level of potassium less than 3.5 mEq/L causes: - diarrhea - diuresis due to diuretic drugs (patients with heart disease) - the presence of excessive aldosterone or glucocorticoids in the body - decreased dietary intake (alcoholism, eating disorders, or starvation) - treatment of diabetic ketoacidosis with insulin effects: - cardiac dysrhythmias - interferes with neuromuscular function HYPERKALEMIA - level of potassium higher than 5 mEq/L causes: - renal failure - deficit of aldosterone - use of "potassium sparing" diuretic drugs - leakage of intercellular potassium due to trauma effects: - cardiac dysrhythmias - muscle weakness - fatigue, nausea, and paresthesias

cerebral edema

a headache develops in patients with cerebral edema. if cerebral edema becomes severe, the pressure can impair brain function because of ischemia can cause death.

metabolic alkalosis

an increase in serum bicarbonate ion, commonly follows loss of hydrochloric acid from the stomach either in the early stages of vomiting or with drainage from the stomach.

swelling of the ankles associated with heart problems:

cause of edema: increased capillary hydrostatic pressure

the swelling that accompanies inflammation:

cause of edema: increased capillary hydrostatic pressure and increased capillary permeability

swelling associated with allergic reactions, such as hives:

cause of edema: increased capillary hydrostatic pressure and increased capillary permeability caused by inflammation

swelling that occurs following multiple tooth extractions:

cause of edema: increased capillary hydrostatic pressure and increased capillary permeability caused by inflammation

the generalized edema that occurs in several kidney diseases:

cause of edema: increased capillary hydrostatic pressure caused by increased blood volume; possibly caused by decreased capillary osmotic pressure due to protein-wasting kidney disease

swelling of the ankles that often happens at the end of the day or after prolonged standing:

cause of edema: increased capillary hydrostatic pressure caused by the effects of gravity

edematous hands and ankles that sometimes accompany excessive ingestion of sodium:

cause of edema: increased capillary hydrostatic pressure caused by the increase of water retention

edema that accompanies burns:

cause of edema: increased capillary permeability and loss of plasma proteins

the abdominal swelling that occurs with starvation:

cause of edema: loss of plasma proteins cause by the decreased synthesis of plasma proteins

the abdominal swelling that accompanies liver failure:

cause of edema: loss of plasma proteins due to decreased production of plasma proteins

a swollen arm following mastectomy (removal of breast):

cause of edema: obstruction of lymphatic circulation due to removal of lymphatic vessels; increased capillary permeability following surgery

edema that may accompany cancer:

cause of edema: obstruction of lymphatic circulation or increased capillary hydrostatic pressure if blood vessels are compressed

insufficient secretion of ADH:

hypernatremia

prolonged use of corticosteroid:

hypernatremia, hypokalemia

identify the electrolyte imbalances that affect normal cardiac function

hypo & hyperkalemia ***hypo & hypercalcemia

prolonged vomiting:

hyponatremia

excessive sweating:

hyponatremia,

inadequate dietary intake of vitamin D:

hyponatremia, hyperkalemia

identify the electrolyte imbalance or imbalances that could develop in each of the following situations -- renal failure:

hyponatremia, hyperkalemia,

aldosterone insufficiency:

hyponatremia, hypokalemia (with potassium sparing diuretic drugs - hyperkalemia)

identify the compensatory mechanisms that are recruited during dehydration

increased thirst, falling BP, increased heart rate, constricted cutaneous blood vessels, and decreased urinary output

describe the manifestations of dehydration. what is the most serious complication of dehydration?

manifestations include; - sunken, soft eyes - decreased skin turgor - thirst - weight loss - rapid, weak pulse - low blood pressure - fatigue, weakness, dizziness, and possible stupor (almost unconscious) - increased body temp the most serious problems are decreased blood pressure and potential shock

renal failure:

metabolic acidosis - increased rate and depth of respiration

chronic diarrhea:

metabolic acidosis - increased rate and depth of respirations, more acid urine

extreme weight loss resulting in lipolysis:

metabolic acidosis - increased renal excretion of acids and conversation of bicarbonate

induced vomiting (bulimia):

metabolic alkalosis - slow, shallow respirations and increased pH of the urine

what is the pH range of normal human plasma? at what pH levels does death usually result?

normal pH range is 7.35-7.4. pH less than 6.8 and greater than 7.8 result in death

Sodium Imbalances: hyponatremia & hypernatremia

normal sodium - 135 to 142 mEq/L HYPONATREMIA - refers to a serum sodium concentration less than 135 mEq/liter causes: direct loss of sodium from the body or from an excess of water in the extracellular compartment. sweating, vomiting, and diarrhea, diuretic drugs and low salt diets effects: impaired nerve conduction, fatigue, muscle cramps, and abdominal discomfort or cramps with nausea and vomiting. brain cells may swell causing confusion, headache, weakness, and seizure. HYPERNATREMIA - an excessive sodium level in the blood and extracellular fluids more than 145 mEq/liter causes: insufficient ADH which results in a large volume of dilute urine, loss of thirst mechanism, watery diarrhea, rapid respiration effects: thirst, weakness, edema, elevated blood pressure

osmotic vs. hydrostatic pressure

proteins and electrolytes contribute to the osmotic pressure of a fluid and therefore are very important in maintaining fluid volumes in various compartments. hydrostatic pressure may be viewed as the "push" force and osmotic pressure and the "pull" or attraction force. Change in either force will alter fluid movement and volume in the compartments.

identify which acid-base imbalance could potentially develop; also identify the compensatory mechanisms that might prevent this from occurring. chronic bronchitis:

respiratory acidosis - more acidic urine

narcotic or barbiturate overdose resulting in respiratory depression:

respiratory acidosis - more acidic urine

pneumonia with severe bronchial congestion:

respiratory acidosis - more acidic urine and increased rate and depth of respiration (if possible)

panic attack with hyperventilation:

respiratory alkalosis - less acidic urine

identify four major buffer systems

sodium bicarbonate--carbonic acid system, phosphate system, hemoglobin system, and protein system

respiratory acidosis

there is an increase in carbon dioxide levels, may occur under several conditions: - acute problems such as pneumonia, airway obstructio, or chest injuries, and in those taking drugs that depress the respiratory control center -chronic respiratory acidosis, common in people with COPD such as emphysema - decompensated respiratory acidosis