CHD Tetrology of Fallot with Pulmonic stenosis - Nursing Case Study

Pathophysiology

• Primary mechanism: In Tetralogy of Fallot (TOF) with pulmonic stenosis, there is a structural defect in the heart causing a stenotic pulmonary valve, obstructing the outflow of blood from the right ventricle into the pulmonary artery. This leads to a decrease in the volume of oxygenated blood reaching the lungs and subsequently the body.

• Secondary mechanism: The structural defect includes a ventricular septal defect (VSD), which causes an abnormal blood flow between the right and left ventricles. The right-to-left shunt results in deoxygenated blood mixing with oxygenated blood, resulting in systemic cyanosis, a significant complication of TOF.

• Key complication: Progressive hypoxia due to the continuous shunting of deoxygenated blood can lead to "Tet spells" - episodes of deep cyanosis, syncope, and, potentially, cerebral hypoxia. Chronic hypoxia may also result in polycythemia, increasing the risk of blood clots and stroke.

Patient Profile

Demographics:

38 years old, Female, Office Secretary

History:

• Key past medical history: Diagnosed with Tetralogy of Fallot with Pulmonic stenosis at birth, underwent palliative shunt placement at 6 months, complete repair at 2 years of age. History of recurrent respiratory infections and hospitalizations for heart failure.

• Current medications: Furosemide 20 mg daily, Carvedilol 6.25 mg twice daily, Digoxin 0.125 mg daily, Warfarin 2 mg daily.

• Allergies: Penicillin causes skin rash

Current Presentation:

• Chief complaint: Shortness of breath on exertion, increasingly worsening over the past month.

• Key symptoms: Cyanosis, fatigue, palpitations, lower extremity swelling, light-headedness, and occasional chest pain.

• Vital signs: Blood Pressure: 100/70 mmHg, Heart Rate: 125 bpm irregular, Respiratory Rate: 28 breaths per minute, Oxygen Saturation: 88% on room air, Temperature: 98.6°F.

Section 1

Change in Patient Status:

The patient's condition began to deteriorate rapidly during the night. The patient was found in a state of altered consciousness, experiencing a "Tet spell". She appeared extremely cyanotic, with an oxygen saturation dropping to 78% despite supplemental oxygen. Her heart rate had increased to 140 bpm, and her blood pressure was 90/60 mmHg. She was also showing signs of respiratory distress, with a respiratory rate of 35 breaths per minute and use of accessory muscles noted. On auscultation, a harsh systolic murmur was prominent.

New Complications:

The situation was further complicated by the development of a sudden onset, severe headache and right-sided weakness. A quick neurological assessment revealed a decrease in motor strength in the right upper and lower extremities, scoring 3/5 on the Medical Research Council (MRC) scale. The patient's speech was slurred, and she was unable to hold her right arm up against gravity. The Glasgow Coma Scale was 12/15, indicating a moderate level of impaired consciousness. These symptoms were suggestive of a possible cerebrovascular event, possibly due to a thromboembolic complication secondary to her polycythemia. An urgent CT scan of her head was ordered to confirm the suspicion.

Section 2

New Diagnostic Results:

The urgent CT scan revealed an acute ischemic stroke in the left middle cerebral artery territory, confirming the suspicion of a thromboembolic event. The patient's lab results also came back with an elevated D-dimer level at 1.2 mcg/mL, further suggesting the presence of a clot. Meanwhile, her complete blood count showed a hemoglobin level of 20 g/dL, pointing towards the polycythemia. Her arterial blood gas analysis revealed a pH of 7.29, PaCO2 of 50 mmHg, PaO2 of 60 mmHg, HCO3- of 24 mEq/L, and a base excess of -3 mEq/L, indicating respiratory acidosis, likely due to her worsening respiratory distress.

The echocardiogram revealed an overriding aorta, ventricular septal defect, right ventricular hypertrophy, and significant pulmonic stenosis, consistent with her diagnosis of Tetralogy of Fallot. The pulmonic stenosis was severe, with a peak gradient of 80 mmHg, leading to right-to-left shunting and explaining her cyanosis and hypoxemia. These findings necessitated immediate intervention to address both her neurological and cardiac complications.

Section 3

Change in Patient Status:

Over the next few hours, the patient's condition deteriorated rapidly. She became increasingly short of breath, with her respiratory rate escalating to 35 breaths per minute and her pulse oximetry reading dropping to 88% on 3 liters of oxygen via nasal cannula. Her blood pressure also became unstable, fluctuating between 80/50 mmHg and 120/80 mmHg. The patient complained of worsening headache and confusion, suggestive of increasing cerebral edema secondary to the acute ischemic stroke. Neurological examination revealed a new right-sided weakness, with a power of 3/5 in both the upper and lower limbs, indicating a progression of the stroke.

Her follow-up arterial blood gas analysis displayed a further drop in pH to 7.25 and an increase in PaCO2 to 55 mmHg, suggesting a worsening respiratory acidosis. A repeat complete blood count showed a further rise in hemoglobin to 22 g/dL, indicating progressive polycythemia. The patient's worsening hypoxemia, combined with her unstable hemodynamics and deteriorating neurological status, signaled an urgent need for critical care management and a reassessment of the treatment strategy.

Section 4

New Diagnostic Results:

Given the patient's deteriorating condition, an urgent echocardiogram was performed, which confirmed the presence of severe pulmonic stenosis and overriding aorta. Additionally, the echocardiogram showed worsening right ventricular hypertrophy and a newly developed right ventricular failure. This was indicative of the progressive severity of the Tetralogy of Fallot. Furthermore, a CT scan of the brain revealed a large area of infarction in the left middle cerebral artery region, corroborating the clinical findings of right-sided weakness and confusion.

Response to Interventions:

Despite aggressive measures to stabilize the patient, the response to interventions was inadequate. The patient was started on Dobutamine infusion to support her blood pressure; however, her hemodynamics remained unstable. The respiratory team was consulted and she was intubated and placed on mechanical ventilation to manage her worsening hypoxemia and respiratory acidosis. The ventilator was set to deliver a higher respiratory rate of 20 breaths per minute, a tidal volume of 500 mL, and a positive end-expiratory pressure of 5 cmH2O. Despite these measures, her pulse oximetry readings fluctuated around 90% and her arterial blood gas showed persistent respiratory acidosis with a pH of 7.28 and a PaCO2 of 52 mmHg, indicating poor response to respiratory support. Her neurological status also continued to decline despite the administration of mannitol for cerebral edema, raising concerns about the increasing extent of the brain damage.

Section 5

New Complications:

As the patient's condition continued to deteriorate, new complications arose. Her hemodynamics remained unstable despite the Dobutamine infusion and she developed a new onset of atrial fibrillation, with a rapid ventricular response of 130-150 beats per minute. The cardiologist was urgently consulted and the patient was started on amiodarone infusion. Despite this, her blood pressure continued to drop, reaching as low as 80/50 mmHg.

Her renal function also started to decline, with her serum creatinine level increasing from 0.9 mg/dL to 1.5 mg/dL within 24 hours. Her urine output also decreased to less than 0.5 mL/kg/hour, raising suspicions of acute kidney injury secondary to the persistent low blood pressure. The nephrologist was consulted and the patient was started on low-dose dopamine in an attempt to preserve renal function. However, her persistent hemodynamic instability necessitated the initiation of continuous renal replacement therapy.

This new development of multiorgan dysfunction syndrome further complicated the patient's situation and required the care team to re-evaluate the management plan, highlighting the need for advanced critical thinking and clinical judgment. The potential consequences of these new developments and the possible need for more invasive interventions, such as extracorporeal membrane oxygenation (ECMO), are now being considered.