,NR283 – PathoPhysiology – MidteRM
A 58-year-old male with a history of chronic hypertension, type 2 diabetes mellitus, and
hyperlipidemia presents to the emergency department with sudden onset of severe, crushing
substernal chest pain radiating to the left arm and jaw, accompanied by diaphoresis, nausea,
and shortness of breath. The pain began 45 minutes ago while he was shoveling snow and has
not been relieved by rest or sublingual nitroglycerin. On assessment, the nurse notes blood
pressure 168/98 mmHg, heart rate 112 bpm, respiratory rate 24 breaths/min, and oxygen
saturation 92% on room air. The client appears pale, cool, and clammy. ECG reveals ST-segment
elevation in leads V2-V5. Considering the pathophysiological mechanisms of acute coronary
syndrome, the cellular changes occurring in myocardial tissue during prolonged ischemia, and
the systemic inflammatory response, which nursing diagnosis should be prioritized in the
immediate care of this client?
a. Anxiety related to fear of death and uncertain prognosis
b. Acute pain related to myocardial ischemia and necrosis
c. Decreased cardiac output related to impaired contractility and dysrhythmias
d. Ineffective tissue perfusion (cardiopulmonary) related to coronary artery occlusion
Correct Answer: d. Ineffective tissue perfusion (cardiopulmonary) related to coronary artery
occlusion
Expert Rationale
This client is experiencing an acute anterior ST-elevation myocardial infarction (STEMI), as
evidenced by the classic presentation of crushing substernal chest pain, diaphoresis, nausea, ST
elevation in anterior leads (V2-V5), and risk factors (hypertension, diabetes, hyperlipidemia).
The underlying pathophysiology involves rupture of an atherosclerotic plaque in the left
anterior descending (LAD) coronary artery, leading to thrombus formation and complete
occlusion of blood flow to the anterior wall of the left ventricle. The priority nursing diagnosis is
ineffective tissue perfusion (cardiopulmonary) because the fundamental problem is the
interruption of oxygenated blood supply to myocardial tissue, resulting in cellular hypoxia,
anaerobic metabolism, lactic acid accumulation, and eventual myocyte necrosis if perfusion is
not restored within 20-40 minutes. While acute pain is present and significant, it is a symptom
of the underlying perfusion deficit. Decreased cardiac output may develop as a complication if
significant myocardial necrosis occurs, but perfusion is the more immediate concern. Anxiety is
present but is not the physiological priority. The goal of immediate intervention (reperfusion
therapy via PCI or fibrinolytics) is to restore tissue perfusion and limit infarct size, making this
,the priority diagnosis that drives all other interventions.
DIF: Cognitive Level: Analysis
OBJ: Prioritize nursing diagnoses in acute MI
TOP: Cardiovascular pathophysiology / Acute coronary syndrome
A 42-year-old female is admitted to the medical-surgical unit with a diagnosis of diabetic
ketoacidosis (DKA) secondary to newly diagnosed type 1 diabetes mellitus. She presents with
polyuria, polydipsia, and polyphagia over the past 2 weeks, followed by nausea, vomiting, and
abdominal pain for the past 24 hours. On admission, her blood glucose is 542 mg/dL, arterial pH
is 7.18, serum bicarbonate is 12 mEq/L, and serum ketones are positive. She exhibits Kussmaul
respirations (deep, rapid breathing at 28 breaths/min), dry mucous membranes, poor skin
turgor, and confusion. Considering the metabolic derangements in DKA, including insulin
deficiency, counterregulatory hormone excess, lipolysis, ketogenesis, and the body's
compensatory mechanisms, which pathophysiological process best explains the client's
Kussmaul respirations?
a. Hypoxemia stimulating peripheral chemoreceptors to increase respiratory rate
b. Metabolic acidosis triggering respiratory compensation to eliminate CO2 and raise pH
c. Pain and anxiety causing hyperventilation and respiratory alkalosis
d. Pulmonary edema from fluid overload stimulating increased respiratory effort
Correct Answer: b. Metabolic acidosis triggering respiratory compensation to eliminate CO2 and
raise pH
Expert Rationale
Diabetic ketoacidosis is characterized by the triad of hyperglycemia, metabolic acidosis, and
ketonemia resulting from absolute or relative insulin deficiency. In the absence of adequate
insulin, glucose cannot enter cells, leading to cellular starvation and activation of
counterregulatory hormones (glucagon, cortisol, catecholamines, growth hormone). This
promotes glycogenolysis, gluconeogenesis, and lipolysis. Free fatty acids are converted in the
liver to ketone bodies (acetoacetate, beta-hydroxybutyrate, and acetone), which are strong
organic acids that dissociate, releasing hydrogen ions and consuming bicarbonate buffers,
resulting in high-anion-gap metabolic acidosis (pH <7.35, bicarbonate <18 mEq/L). The body
compensates for metabolic acidosis through the respiratory system: hydrogen ions stimulate
peripheral and central chemoreceptors, increasing respiratory rate and depth (Kussmaul
respirations) to blow off CO2 (an acid when dissolved as carbonic acid). This respiratory
compensation follows Winter's formula: expected PaCO2 = (1.5 × HCO3-) + 8 ± 2. By reducing
PaCO2, the body attempts to normalize the pH toward 7.40. Kussmaul respirations are deep and
rapid (not shallow), distinguishing them from other respiratory patterns. Hypoxemia is not
typically present in uncomplicated DKA. Pain and anxiety may contribute but do not explain the
, characteristic deep, labored breathing pattern. Pulmonary edema is not typical in DKA, which
presents with dehydration from osmotic diuresis, not fluid overload.
DIF: Cognitive Level: Analysis
OBJ: Explain compensatory mechanisms in acid-base disorders
TOP: Endocrine pathophysiology / Diabetic ketoacidosis
A 67-year-old male with a 45-pack-year smoking history is diagnosed with stage IIIB non-small
cell lung cancer (NSCLC) with metastasis to the brain and bones. He presents with progressive
dyspnea, chronic cough with hemoptysis, weight loss of 25 pounds over 3 months, and severe
bone pain. The oncology team is considering immunotherapy with a PD-1 inhibitor
(pembrolizumab). Considering the tumor microenvironment, immune evasion mechanisms
employed by cancer cells, and the mechanism of action of checkpoint inhibitors, how does
pembrolizumab exert its antitumor effect in this client?
a. Directly kills cancer cells by inducing apoptosis through DNA damage
b. Blocks the interaction between PD-1 on T-cells and PD-L1 on tumor cells, restoring T-cell-
mediated cytotoxicity
c. Inhibits angiogenesis by blocking vascular endothelial growth factor (VEGF) receptors
d. Suppresses tumor growth by inhibiting tyrosine kinase activity in cancer cells
Correct Answer: b. Blocks the interaction between PD-1 on T-cells and PD-L1 on tumor cells,
restoring T-cell-mediated cytotoxicity
Expert Rationale
Non-small cell lung cancer, particularly in smokers, often expresses high levels of programmed
death-ligand 1 (PD-L1) on tumor cell surfaces. Normally, PD-L1 binds to programmed death-1
(PD-1) receptors on activated T-cells, delivering an inhibitory signal that suppresses T-cell
proliferation, cytokine production, and cytotoxic activity. This is a physiological immune
checkpoint that prevents autoimmunity and limits tissue damage during inflammation.
However, cancer cells exploit this mechanism to evade immune surveillance: by expressing PD-
L1, tumor cells effectively "turn off" cytotoxic T-cells that would otherwise recognize and
destroy them. Pembrolizumab is a monoclonal antibody that binds to PD-1 receptors on T-cells,
blocking the PD-1/PD-L1 interaction. This prevents the inhibitory signal, allowing T-cells to
remain activated, proliferate, produce cytokines (interferon-gamma, TNF-alpha), and exert
cytotoxic effects on tumor cells through release of perforin and granzymes or induction of
apoptosis via Fas/FasL pathways. This restores the body's own immune response against the
cancer. Option a describes chemotherapy (cytotoxic agents). Option c describes anti-angiogenic
therapy (bevacizumab). Option d describes tyrosine kinase inhibitors (erlotinib, gefitinib) used in
EGFR-mutated NSCLC. Understanding immune checkpoint pathways is essential for oncology
nursing, as these agents have unique side effect profiles (immune-related adverse events)
A 58-year-old male with a history of chronic hypertension, type 2 diabetes mellitus, and
hyperlipidemia presents to the emergency department with sudden onset of severe, crushing
substernal chest pain radiating to the left arm and jaw, accompanied by diaphoresis, nausea,
and shortness of breath. The pain began 45 minutes ago while he was shoveling snow and has
not been relieved by rest or sublingual nitroglycerin. On assessment, the nurse notes blood
pressure 168/98 mmHg, heart rate 112 bpm, respiratory rate 24 breaths/min, and oxygen
saturation 92% on room air. The client appears pale, cool, and clammy. ECG reveals ST-segment
elevation in leads V2-V5. Considering the pathophysiological mechanisms of acute coronary
syndrome, the cellular changes occurring in myocardial tissue during prolonged ischemia, and
the systemic inflammatory response, which nursing diagnosis should be prioritized in the
immediate care of this client?
a. Anxiety related to fear of death and uncertain prognosis
b. Acute pain related to myocardial ischemia and necrosis
c. Decreased cardiac output related to impaired contractility and dysrhythmias
d. Ineffective tissue perfusion (cardiopulmonary) related to coronary artery occlusion
Correct Answer: d. Ineffective tissue perfusion (cardiopulmonary) related to coronary artery
occlusion
Expert Rationale
This client is experiencing an acute anterior ST-elevation myocardial infarction (STEMI), as
evidenced by the classic presentation of crushing substernal chest pain, diaphoresis, nausea, ST
elevation in anterior leads (V2-V5), and risk factors (hypertension, diabetes, hyperlipidemia).
The underlying pathophysiology involves rupture of an atherosclerotic plaque in the left
anterior descending (LAD) coronary artery, leading to thrombus formation and complete
occlusion of blood flow to the anterior wall of the left ventricle. The priority nursing diagnosis is
ineffective tissue perfusion (cardiopulmonary) because the fundamental problem is the
interruption of oxygenated blood supply to myocardial tissue, resulting in cellular hypoxia,
anaerobic metabolism, lactic acid accumulation, and eventual myocyte necrosis if perfusion is
not restored within 20-40 minutes. While acute pain is present and significant, it is a symptom
of the underlying perfusion deficit. Decreased cardiac output may develop as a complication if
significant myocardial necrosis occurs, but perfusion is the more immediate concern. Anxiety is
present but is not the physiological priority. The goal of immediate intervention (reperfusion
therapy via PCI or fibrinolytics) is to restore tissue perfusion and limit infarct size, making this
,the priority diagnosis that drives all other interventions.
DIF: Cognitive Level: Analysis
OBJ: Prioritize nursing diagnoses in acute MI
TOP: Cardiovascular pathophysiology / Acute coronary syndrome
A 42-year-old female is admitted to the medical-surgical unit with a diagnosis of diabetic
ketoacidosis (DKA) secondary to newly diagnosed type 1 diabetes mellitus. She presents with
polyuria, polydipsia, and polyphagia over the past 2 weeks, followed by nausea, vomiting, and
abdominal pain for the past 24 hours. On admission, her blood glucose is 542 mg/dL, arterial pH
is 7.18, serum bicarbonate is 12 mEq/L, and serum ketones are positive. She exhibits Kussmaul
respirations (deep, rapid breathing at 28 breaths/min), dry mucous membranes, poor skin
turgor, and confusion. Considering the metabolic derangements in DKA, including insulin
deficiency, counterregulatory hormone excess, lipolysis, ketogenesis, and the body's
compensatory mechanisms, which pathophysiological process best explains the client's
Kussmaul respirations?
a. Hypoxemia stimulating peripheral chemoreceptors to increase respiratory rate
b. Metabolic acidosis triggering respiratory compensation to eliminate CO2 and raise pH
c. Pain and anxiety causing hyperventilation and respiratory alkalosis
d. Pulmonary edema from fluid overload stimulating increased respiratory effort
Correct Answer: b. Metabolic acidosis triggering respiratory compensation to eliminate CO2 and
raise pH
Expert Rationale
Diabetic ketoacidosis is characterized by the triad of hyperglycemia, metabolic acidosis, and
ketonemia resulting from absolute or relative insulin deficiency. In the absence of adequate
insulin, glucose cannot enter cells, leading to cellular starvation and activation of
counterregulatory hormones (glucagon, cortisol, catecholamines, growth hormone). This
promotes glycogenolysis, gluconeogenesis, and lipolysis. Free fatty acids are converted in the
liver to ketone bodies (acetoacetate, beta-hydroxybutyrate, and acetone), which are strong
organic acids that dissociate, releasing hydrogen ions and consuming bicarbonate buffers,
resulting in high-anion-gap metabolic acidosis (pH <7.35, bicarbonate <18 mEq/L). The body
compensates for metabolic acidosis through the respiratory system: hydrogen ions stimulate
peripheral and central chemoreceptors, increasing respiratory rate and depth (Kussmaul
respirations) to blow off CO2 (an acid when dissolved as carbonic acid). This respiratory
compensation follows Winter's formula: expected PaCO2 = (1.5 × HCO3-) + 8 ± 2. By reducing
PaCO2, the body attempts to normalize the pH toward 7.40. Kussmaul respirations are deep and
rapid (not shallow), distinguishing them from other respiratory patterns. Hypoxemia is not
typically present in uncomplicated DKA. Pain and anxiety may contribute but do not explain the
, characteristic deep, labored breathing pattern. Pulmonary edema is not typical in DKA, which
presents with dehydration from osmotic diuresis, not fluid overload.
DIF: Cognitive Level: Analysis
OBJ: Explain compensatory mechanisms in acid-base disorders
TOP: Endocrine pathophysiology / Diabetic ketoacidosis
A 67-year-old male with a 45-pack-year smoking history is diagnosed with stage IIIB non-small
cell lung cancer (NSCLC) with metastasis to the brain and bones. He presents with progressive
dyspnea, chronic cough with hemoptysis, weight loss of 25 pounds over 3 months, and severe
bone pain. The oncology team is considering immunotherapy with a PD-1 inhibitor
(pembrolizumab). Considering the tumor microenvironment, immune evasion mechanisms
employed by cancer cells, and the mechanism of action of checkpoint inhibitors, how does
pembrolizumab exert its antitumor effect in this client?
a. Directly kills cancer cells by inducing apoptosis through DNA damage
b. Blocks the interaction between PD-1 on T-cells and PD-L1 on tumor cells, restoring T-cell-
mediated cytotoxicity
c. Inhibits angiogenesis by blocking vascular endothelial growth factor (VEGF) receptors
d. Suppresses tumor growth by inhibiting tyrosine kinase activity in cancer cells
Correct Answer: b. Blocks the interaction between PD-1 on T-cells and PD-L1 on tumor cells,
restoring T-cell-mediated cytotoxicity
Expert Rationale
Non-small cell lung cancer, particularly in smokers, often expresses high levels of programmed
death-ligand 1 (PD-L1) on tumor cell surfaces. Normally, PD-L1 binds to programmed death-1
(PD-1) receptors on activated T-cells, delivering an inhibitory signal that suppresses T-cell
proliferation, cytokine production, and cytotoxic activity. This is a physiological immune
checkpoint that prevents autoimmunity and limits tissue damage during inflammation.
However, cancer cells exploit this mechanism to evade immune surveillance: by expressing PD-
L1, tumor cells effectively "turn off" cytotoxic T-cells that would otherwise recognize and
destroy them. Pembrolizumab is a monoclonal antibody that binds to PD-1 receptors on T-cells,
blocking the PD-1/PD-L1 interaction. This prevents the inhibitory signal, allowing T-cells to
remain activated, proliferate, produce cytokines (interferon-gamma, TNF-alpha), and exert
cytotoxic effects on tumor cells through release of perforin and granzymes or induction of
apoptosis via Fas/FasL pathways. This restores the body's own immune response against the
cancer. Option a describes chemotherapy (cytotoxic agents). Option c describes anti-angiogenic
therapy (bevacizumab). Option d describes tyrosine kinase inhibitors (erlotinib, gefitinib) used in
EGFR-mutated NSCLC. Understanding immune checkpoint pathways is essential for oncology
nursing, as these agents have unique side effect profiles (immune-related adverse events)
