14
OVERVIEW/PATHOPHYSIOLOGY
Acute respiratory failure (ARF) develops when the lungs are unable to exchange O
2and CO
2adequately. Clinically, respi- ratory failure exists when Pa
O2is less than 60 mm Hg with the patient at rest and breathing room air. Pa
CO2of 50 mm Hg or more or pH less than 7.35 is significant for respiratory aci- dosis, which is the common precursor to ARF.
Although a variety of disease processes can lead to the development of respiratory failure, four basic mechanisms are involved.
Alveolar hypoventilation:
Occurs secondary to reduction in alveolar minute ventilation. Because differential indicators (cyanosis, somnolence) occur late in the process, the condi- tion may go unnoticed until tissue hypoxia is severe.
Ventilation-perfusion mismatch:
Considered the most common cause of hypoxemia. Normal alveolar ventilation occurs at a rate of 4 L/min, with normal pulmonary vascular blood flow occurring at a rate of 5 L/min. Normal ventilation/
perfusion ratio is 0.8 : 1. Any disease process that interferes with either side of the equation upsets physiologic balance and can lead to respiratory failure as a result of reduction in arterial O
2levels.
Diffusion disturbances:
Processes that physically impair gas exchange across the alveolar-capillary membrane. Diffusion is impaired because of the increase in anatomic distance the gas must travel from alveoli to capillary and capillary to alveoli.
Right-to-left shunt:
Occurs when the previously mentioned processes go untreated. Large amounts of blood pass from the right side of the heart to the left and out into the general circulation without adequate ventilation; therefore, blood is poorly oxygenated. This mechanism occurs when alveoli are atelectatic or fluid filled, inasmuch as these conditions inter- fere with gas exchange. Unlike the first three responses, hypoxemia secondary to right-to-left shunting does not improve with O
2administration because the additional Fi
O2is unable to cross the alveolar-capillary membrane.
HEALTH CARE SETTING
Primary care; acute care resulting from complications
ASSESSMENT
Clinical indicators of ARF vary according to the underlying disease process and severity of the failure. ARF is one of the most common causes of impaired level of consciousness. Often
Early indicators:
Restlessness, changes in mental status, anxiety, headache, fatigue, cool and dry skin, increased blood pressure, tachycardia, cardiac dysrhythmias.
Intermediate indicators:
Confusion, increased agitation, and increased oxygen requirements with decreased oxygen saturations. Patients who have hypoventilation respiratory failure often exhibit lethargy and bradypnea. Patients with ventilation-perfusion mismatch often exhibit tachypnea.
Late indicators:
Cyanosis, diaphoresis, coma, respiratory arrest.
DIAGNOSTIC TESTS
Arterial blood gas (ABG) analysis:
Assesses adequacy of oxygenation and effectiveness of ventilation and is the most important diagnostic tool. Typical results are Pa
O260 mm Hg or less, Pa
CO250 mm Hg or more, and pH less than 7.35, which are consistent with severe respiratory acidosis.
Chest x-ray examination:
Ascertains the presence of under- lying pathophysiology or disease process that may be contrib- uting to the failure.
NURSING DIAGNOSES/PROBLEMS:
(THE LISTED DISORDERS MAY BE PRECURSORS TO ARF)
“Psychosocial Support” p. 72
“Chronic Obstructive Pulmonary Disease” p. 111
“Pneumonia” for Impaired Gas Exchange p. 118
Deficient Fluid Volume p. 120
“Pneumothorax/Hemothorax” p. 122
“Pulmonary Embolus” p. 127
“Guillain-Barré Syndrome” p. 267
“Multiple Sclerosis” p. 286
PATIENT-FAMILY TEACHING AND DISCHARGE PLANNING
ARF is an acute condition that is symptomatically treated during
the patient’s hospitalization. Discharge planning and teaching
should be directed at educating the patient and significant others
about the underlying pathophysiology and treatment specific for
that process. See chapters in this Respiratory section, shown
above, as precursors that relate specifically to the underlying
137
Cardiovascular Care Plans
Aneurysms 15
OVERVIEW/PATHOPHYSIOLOGY
An aneurysm is a pathologic expansion in a section of an arterial wall. The most common cause is atherosclerosis, which alters the vessel pathology, weakens the vessel wall, and allows expansion. Additional causes include vessel wall trauma, congenital connective tissue disorders (e.g., Marfan’s syndrome), and infection, particularly syphilis or acquired immunodeficiency syndrome (AIDS). Primary risk factors are heredity, age, and smoking. Because undiagnosed and untreated aneurysms are at risk for rupture and embolization, early diagnosis is imperative. Although aneurysms can develop in any artery, the abdominal aorta is the most common site.
Abdominal aortic aneurysms (AAAs) occur more often in men and represent approximately 80% of all aneurysms. As the aneurysm enlarges, the risk of rupture increases. Aneu- rysms larger than 5.5 cm have the highest risk of rupture and require frequent monitoring and intervention.
Aneurysms in the thoracic aorta are most often attributed to the modifiable risk factors of hypertension and cigarette smoking. Thoracic aneurysms are more susceptible to dissec- tion. The atherosclerotic lesions present in
dissecting aneu- rysms develop intimal tears, which allow bleeding into thelayers of the vessel, causing false lumens to form that obstruct or limit blood flow in the true lumen of the vessel. This pathology is distinctly different from that of AAAs.
Early diagnosis and periodic evaluation of aneurysms are essential to protect the patient from emergent life-threatening rupture. Physical assessment combined with ultrasound and radiologic screening of patients with risk factors leads to diagnosis.
HEALTH CARE SETTING
Chronic aneurysms may be monitored in primary care, with periodic radiographic or ultrasound assessment. Surgical inter- vention requires hospitalization and acute or intensive care during the perioperative period. Rehabilitation and home care services may be necessary during recovery.
ASSESSMENT
Abdominal aortic aneurysm:
A pulsatile, nontender mass may be palpated on both sides of the abdominal midline.
Assessment is more difficult in obese patients. Severe acute abdominal pain, of sudden onset with radiation to the back, may be indicative of aneurysm rupture and is a surgical emer- gency. Rupture carries a high mortality of up to 75% (Radvany
& Seguritan, 2008).
Thoracic aneurysm:
Patients may be asymptomatic for years; however, pressure from the aneurysm on adjacent struc- tures can result in dull pain in the upper back, dyspnea, cough, dysphasia, hemoptysis, tracheal deviation, and hoarseness. If there is pain associated with these aneurysms, it is more likely to be nonradiating central chest pain.
Femoral aneurysm:
Leg or groin pain, decreased pulses, and swelling of the affected leg may occur. Femoral aneurysms may rupture or thrombose. See indicators discussed in Chapter
16, “Atherosclerotic Arterial Occlusive Disease,” p. 140.Acute indicators (rupture or dissection):
Sudden onset of severe pain in the area of aneurysm with radiation, pallor, diaphoresis, and sudden loss of consciousness.
Physical assessment with acute rupture:
Sudden drop of blood pressure (BP), weak and thready peripheral pulses, tachycardia, cyanosis, cool and clammy skin, and altered level of consciousness. Hypovolemic shock and death may occur, depending on severity of the bleeding.
DIAGNOSTIC TESTS
CT scan:
Imaging standard with 100% accuracy, depicting exact location and size. It must be used in urgent situations in which suspicion for rupture is high and the patient is stable.
Ultrasound:
Sound waves evaluate aneurysm size, shape, and location. This is a noninvasive and efficient examination, used for initial and emergent screening, especially when the patient is unstable.
Abdominal x-ray examination:
May detect calcifications in the vessel wall but is not used for aneurysm evaluation.
Contrast arteriography:
Determines size of the aneurysm,
leaking, and origin of blood vessels arising from the aorta.
PART I: Medical-Surgical Nursing
Risk for Decreased Cardiac Tissue Perfusion/
Risk for Ineffective Renal Perfusion/
Risk for Ineffective Gastrointestinal Perfusion
related to interrupted arterial flow occurring with rupture, bleeding, or embo- lization following the invasive procedure
Desired Outcome:
The patient has adequate perfusion as evidenced by peripheral pulse amplitude greater than 2
+on a 0-4
+scale, brisk capillary refill (less than 2 sec), and exhibits baseline extremity sensation, motor function, color, and temperature.
ASSESSMENT/INTERVENTIONS RATIONALES
Assess vital signs (VS) and peripheral pulses frequently in the perioperative period. Use a Doppler if necessary.
This provides ongoing assessment of perfusion. Pulse amplitude 2 or less (or other than “N”) could signal embolization. Some health care centers use A (absent), D (requires Doppler), W (weak), N (normal), and B (bounding) to describe peripheral pulses. A Doppler is necessary for detection of a pulse that cannot be palpated.
If indicated, mark the location of peripheral pulses with a pen. Location marking enables rapid identification of the pulses by all members of the health care team.
Assess peripheral sensation with VS. Instruct the patient to report impaired sensation promptly.
Impaired sensation could signal impaired perfusion secondary to embolization or bleeding. The patient is the first to notice changes in sensation.
Assess urine output frequently, recording intake and output measurements.
Severe hypotension or renal artery occlusion can decrease renal perfusion. Optimally urine output is 30 mL/hr or greater.
Report to the health care provider immediately any changes in vital signs, extremity color, capillary refill, temperature, motor function, sensation, or increasing pain.
These are assessments of peripheral perfusion; changes from baseline (e.g., VS variance of 20% or greater, capillary refill 3 sec or greater, coolness, pallor, or mottling, decreased motor function or sensation, and pain) may signal embolization or bleeding. Arterial obstruction and bleeding must be treated emergently to prevent hemorrhage, ischemia, and potential loss of the extremity.
Maintain the patient in neutral position and on bedrest until otherwise directed.
Bedrest helps maintain BP and perfusion. The neutral position maintains integrity of the graft and minimizes risk of postprocedure
embolization.
Report any bloody diarrhea to the health care provider. This may be a sign of bowel ischemia.
As prescribed, administer beta-blockers (i.e., metoprolol, atenolol, propanolol) to decrease myocardial irritability and contractility.
These agents slow the heart rate and decrease BP, which aids in preventing dissection.
PATIENT-FAMILY TEACHING AND DISCHARGE PLANNING
When providing patient-family teaching, focus on sensory information, avoid giving excessive information, and initiate a visiting nurse referral for necessary follow-up teaching.
Include verbal and written information about the following:
✓
Importance of regular medical follow-up to ensure graft patency, arterial integrity, and adequate perfusion.
✓
Reduction and/or management of risk factors (i.e., ciga- rette smoking, hypertension, obesity, diabetes) to
prevent postoperative complications and slow the pro- gression of atherosclerosis.
✓
Necessity of a regularly scheduled exercise program that may progress as the patient recovers.
✓
Indicators of wound infection and thrombus or embolus formation, and the need to report them promptly to the health care provider should they occur.
✓