HESI Pathophysiology Final Exam Prep:
Comprehensive Practice Questions, Key
Concepts & Detailed Answers
Acid-Base Values Normal values — The range of normal values varies
among laboratories. In general, normal values for acidity
(pH), the partial pressure of carbon dioxide (PaCO2) and
bicarbonate concentration (HCO3) are as follows:
● pH - 7.35 to 7.45
● PaCO2 - 35 to 45 mmHg (4.7 to 6 kPa)
● HCO3 - 21 to 27 mEq/L
Respiratory acidosis excess CO2 retention, pH <7.35, HCo3 >45, PaCO2 >45
S/S: anxiety, apprehension, confusion/coma, excessive
sweating, headache, restlessness, tachycardia
,Respiratory alkalosis excess CO2 excretion, pH >7.45, HCO3 <35, PaCO2 <35
S/S: anxiety, fear, lightheadedness, paresthesias, rapid deep
breathing, twitching
Metabolic Acidosis HCO3 loss and acid retention, pH <7.35, HCO3<22, PaCO2 >35
S/S: coma (in severe cases), drowsiness, fatigue, fruity breath (if
DKA), headache, lethargy, nausea, rapid deep breathing,
vomiting.
Metabolic Alkalosis HCO3 retention, acid loss, pH>77.45, HCO3 >28, PaCO2 > 45
S/S: coma (in severe cases), confusion, irritability, hypertonic
muscles, mental apathy, restlessness, seizures, slow shallow
breathing, tetany, twitching
Amputation Indications ●An unsalvageable extremity due to critical limb ischemia
in patients with vascular disease. Primary amputation may be
the only option for patients without an anatomic option
for revascularization or those with medical risk factors that
contraindicate revascularization.
• Peripheral artery disease.
• Acute arterial thrombosis or thromboembolism.
● Trauma resulting in a mangled extremity or failed
attempt at limb salvage.
● Severe infections with extensive soft tissue
or bony destruction, or osteomyelitis.
● Locally unresectable malignant
tumors of the musculoskeletal system [6].
● Frostbite-related gangrene.
● Failed management of acute compartment syndrome.
● Failed management of Charcot's
degenerative osteoarthropathy.
● Debilitating extremity paralysis, which can be
unilateral but is frequently bilateral (eg, paraplegia), from
infection or pressure-related complications.
, Amputation Medical Risks ●Myocardial infarction is the most common cause of
death following lower extremity amputation in patients
with peripheral artery disease
● Pulmonary complications, including atelectasis
and pneumonia, complicate 5 percent of major lower
extremity amputations
● The incidence of new-onset renal failure after a
lower extremity major amputation is 0.6 to 2.6 percent. Renal
failure is associated with increased operative and long-
term mortality
Amputation Complications -Deep vein thrombosis — Deep vein thrombosis (DVT) has
been reported in up to 50 percent of patients following major
lower extremity amputation without prophylaxis [32]. The
incidence of deep vein thrombosis is higher for above-
knee amputation compared with below-knee amputation
(37.5 versus 21.2 percent, respectively) [47]. This difference
may contribute to the increased incidence of sudden death
due to thromboembolism in patients with above-knee
amputation.
Thus, it is important to provide thromboprophylaxis.
(See 'Thromboprophylaxis' above and 'Perioperative
mortality' below.)
-Stump hematoma — Postoperative bleeding that requires
reoperation occurs in 3 to 9 percent of major lower extremity
amputations, and stump hematoma may lead to stump wound
breakdown [9,48]. Patients on antithrombotic therapy,
including DVT prophylaxis, are at a higher risk for stump
hematoma. Patients with stump hematoma causing pain and
stump swelling with or without drainage should have the
wound opened partially, the hematoma evacuated, and
the wound washed out and packed with a moist saline
dressing.
-Infection — Wound infection following major lower extremity
amputation occurs in 13 to 40 percent of patients [26,27,49].
Patients with diabetes, preoperative wound infection,
malnutrition, malignancy, advanced age, wound hematoma,
and prior prosthetic bypass grafts have an increased risk for
stump wound infection. In patients with prior lower extremity
bypass graft, stump infection rates are reduced by complete
removal of synthetic graft material [50].
-Superficial wound infections are treated by removing the skin
sutures and initiating broad-spectrum antibiotics, which are
adapted to reflect the results of wound culture and
sensitivities. Deeper wound infection requires operative
management with removal of skin and fascial sutures, drai
Comprehensive Practice Questions, Key
Concepts & Detailed Answers
Acid-Base Values Normal values — The range of normal values varies
among laboratories. In general, normal values for acidity
(pH), the partial pressure of carbon dioxide (PaCO2) and
bicarbonate concentration (HCO3) are as follows:
● pH - 7.35 to 7.45
● PaCO2 - 35 to 45 mmHg (4.7 to 6 kPa)
● HCO3 - 21 to 27 mEq/L
Respiratory acidosis excess CO2 retention, pH <7.35, HCo3 >45, PaCO2 >45
S/S: anxiety, apprehension, confusion/coma, excessive
sweating, headache, restlessness, tachycardia
,Respiratory alkalosis excess CO2 excretion, pH >7.45, HCO3 <35, PaCO2 <35
S/S: anxiety, fear, lightheadedness, paresthesias, rapid deep
breathing, twitching
Metabolic Acidosis HCO3 loss and acid retention, pH <7.35, HCO3<22, PaCO2 >35
S/S: coma (in severe cases), drowsiness, fatigue, fruity breath (if
DKA), headache, lethargy, nausea, rapid deep breathing,
vomiting.
Metabolic Alkalosis HCO3 retention, acid loss, pH>77.45, HCO3 >28, PaCO2 > 45
S/S: coma (in severe cases), confusion, irritability, hypertonic
muscles, mental apathy, restlessness, seizures, slow shallow
breathing, tetany, twitching
Amputation Indications ●An unsalvageable extremity due to critical limb ischemia
in patients with vascular disease. Primary amputation may be
the only option for patients without an anatomic option
for revascularization or those with medical risk factors that
contraindicate revascularization.
• Peripheral artery disease.
• Acute arterial thrombosis or thromboembolism.
● Trauma resulting in a mangled extremity or failed
attempt at limb salvage.
● Severe infections with extensive soft tissue
or bony destruction, or osteomyelitis.
● Locally unresectable malignant
tumors of the musculoskeletal system [6].
● Frostbite-related gangrene.
● Failed management of acute compartment syndrome.
● Failed management of Charcot's
degenerative osteoarthropathy.
● Debilitating extremity paralysis, which can be
unilateral but is frequently bilateral (eg, paraplegia), from
infection or pressure-related complications.
, Amputation Medical Risks ●Myocardial infarction is the most common cause of
death following lower extremity amputation in patients
with peripheral artery disease
● Pulmonary complications, including atelectasis
and pneumonia, complicate 5 percent of major lower
extremity amputations
● The incidence of new-onset renal failure after a
lower extremity major amputation is 0.6 to 2.6 percent. Renal
failure is associated with increased operative and long-
term mortality
Amputation Complications -Deep vein thrombosis — Deep vein thrombosis (DVT) has
been reported in up to 50 percent of patients following major
lower extremity amputation without prophylaxis [32]. The
incidence of deep vein thrombosis is higher for above-
knee amputation compared with below-knee amputation
(37.5 versus 21.2 percent, respectively) [47]. This difference
may contribute to the increased incidence of sudden death
due to thromboembolism in patients with above-knee
amputation.
Thus, it is important to provide thromboprophylaxis.
(See 'Thromboprophylaxis' above and 'Perioperative
mortality' below.)
-Stump hematoma — Postoperative bleeding that requires
reoperation occurs in 3 to 9 percent of major lower extremity
amputations, and stump hematoma may lead to stump wound
breakdown [9,48]. Patients on antithrombotic therapy,
including DVT prophylaxis, are at a higher risk for stump
hematoma. Patients with stump hematoma causing pain and
stump swelling with or without drainage should have the
wound opened partially, the hematoma evacuated, and
the wound washed out and packed with a moist saline
dressing.
-Infection — Wound infection following major lower extremity
amputation occurs in 13 to 40 percent of patients [26,27,49].
Patients with diabetes, preoperative wound infection,
malnutrition, malignancy, advanced age, wound hematoma,
and prior prosthetic bypass grafts have an increased risk for
stump wound infection. In patients with prior lower extremity
bypass graft, stump infection rates are reduced by complete
removal of synthetic graft material [50].
-Superficial wound infections are treated by removing the skin
sutures and initiating broad-spectrum antibiotics, which are
adapted to reflect the results of wound culture and
sensitivities. Deeper wound infection requires operative
management with removal of skin and fascial sutures, drai
