Transposition of the Great Vessels - Nursing Case Study
Pathophysiology
• Primary mechanism: Transposition of the Great Vessels (TGV) is a congenital heart defect where the aorta and pulmonary artery are switched. The aorta arises from the right ventricle (normally supplies deoxygenated blood to the lungs) and the pulmonary artery from the left ventricle (supplies oxygenated blood to the body). This results in two separate circulations (systemic and pulmonary) which are not connected, leading to insufficient oxygen supply to the body.
• Secondary mechanism: A small hole (foramen ovale or ventricular septal defect) between the atria or ventricles allows some oxygenated blood to mix with deoxygenated blood, partially compensating for the defect. However, this is not enough to fully oxygenate the body.
• Key complication: Without early intervention, cyanosis (blue or purple coloration of the skin due to lack of oxygen) develops soon after birth. This can lead to heart failure and other serious complications such as brain damage due to inadequate oxygen supply
Patient Profile
Demographics:
2 months old, Male, No occupation
History:
• Key past medical history: Born with transposition of the great vessels, cyanotic since birth
• Current medications: Prostaglandin E1, Furosemide, Digoxin
• Allergies: No known allergies
Current Presentation:
• Chief complaint: Increasing difficulty in feeding, persistent cyanosis, worsening breathlessness
• Key symptoms: Fast breathing, poor weight gain, excessive sweating particularly during feedings, cool and pale extremities
• Vital signs: Heart rate: 160 beats per minute, Respiratory rate: 60 breaths per minute, Oxygen saturation: 75% on room air, Temperature: 98.6 F, Blood pressure: 85/45 mm Hg
Section 1
New Diagnostic Results:
After noting the infant's persistent cyanosis and increasingly labored breathing, the healthcare team decides to perform additional diagnostic testing to assess the severity of his condition. Given the young age of the patient and the severity of his TGV, an echocardiogram is ordered to evaluate the structure and function of his heart. The results reveal a severe form of transposition of the great vessels, with the aorta and pulmonary artery in reversed positions. The echocardiogram also shows a small ventricular septal defect that is allowing some mixed blood flow, but not enough to compensate for the transposed vessels.
Concurrently, a complete blood count (CBC) and arterial blood gas (ABG) are also performed. The CBC shows a significantly elevated hematocrit level of 65% (normal range for a 2-month-old: 28-42%), indicating polycythemia, a condition where the body produces too many red blood cells in response to chronic low oxygen levels. The ABG reveals a PaO2 of 50 mmHg (normal range: 75-100 mmHg), a PaCO2 of 35 mmHg (normal range: 35-45 mmHg), and a pH of 7.35 (normal range: 7.35-7.45), indicating hypoxemia and a compensatory response to maintain a normal pH. These findings confirm the clinical suspicion of inadequate oxygenation due to the transposition of the great vessels and highlight the need for urgent intervention.
Section 2
Change in Patient Status:
Over the next few hours, the infant's condition begins to deteriorate. Despite receiving supplemental oxygen, his oxygen saturation levels continue to fall, now measuring in the low 80s (normal range for infants: 92-100%). He becomes increasingly lethargic and less responsive to stimuli, indicating worsening hypoxia. His respiratory rate also increases to 70 breaths per minute (normal range for a 2-month-old: 30-60 breaths per minute), with observed intercostal retractions and nasal flaring, signs of severe respiratory distress. Furthermore, his heart rate is elevated at 170 beats per minute (normal range for a 2-month-old: 85-205 beats per minute), suggesting increased cardiac workload due to the heart's continued efforts to compensate for the lack of oxygen.
Additionally, the infant's skin and mucous membranes become even more cyanotic, and the capillary refill time increases to 4 seconds (normal: <2 seconds), indicating poor peripheral perfusion. These changes highlight the urgent need for more aggressive intervention to correct the anatomic abnormality and improve oxygenation. The escalating clinical picture requires quick clinical reasoning to manage the infant's symptoms and reduce further complications. The clinical team begins to prepare for possible surgical intervention, while regularly monitoring the infant's vital signs and adjusting supportive care as needed.
Section 3
New Diagnostic Results:
The clinical team conducts a chest X-ray, which shows an egg-on-side appearance of the heart, as well as decreased pulmonary vascularity, suggesting transposition of the great arteries (TGA). An echocardiogram is also performed and confirms the diagnosis of TGA. The echocardiogram reveals the aorta arising from the right ventricle and the pulmonary artery from the left ventricle, an abnormality causing the oxygen-poor blood to be circulated back to the body and oxygen-rich blood to the lungs.
Initial blood gas analysis shows a pH of 7.26 (normal: 7.35-7.45), indicating acidosis, PaCO2 of 55 mmHg (normal: 35-45 mmHg), indicating hypercapnia, and PaO2 of 50 mmHg (normal: 75-100 mmHg), indicating hypoxemia. These lab findings suggest the infant's body is compensating for the hypoxia by increasing the respiratory rate and cardiac output, but this is leading to respiratory and metabolic acidosis.
These diagnostic results further highlight the severity of the infant's condition and the urgent need for intervention. The team must now consider the best course of action, taking into account the infant's worsening condition and the risk associated with surgical intervention.
Section 4
New Complications:
As the infant's condition continues to deteriorate, the team notes further indications of worsening hypoxia. The baby's skin appears bluish (cyanosis), especially around the lips and fingernails, and the infant's respiratory rate increases to 60 breaths per minute (normal: 30-60 breaths per minute). The baby's heart rate also rises to 180 beats per minute (normal: 100-160 beats per minute), indicating tachycardia. These signs suggest the baby's body is attempting to compensate for the lack of oxygen.
During this time, the infant's blood gas analysis is repeated and shows further deterioration, with a pH of 7.20, PaCO2 of 60 mmHg, and PaO2 of 45 mmHg. These worsening values indicate continued respiratory and metabolic acidosis, as well as persistent hypoxemia. The team also notes increased lactate levels of 5 mmol/L (normal: 0.5-1.6 mmol/L), indicating tissue hypoxia. Given these findings, the team concludes that the infant's compensatory mechanisms are failing, and immediate intervention, likely in the form of surgical repair, is required. This decision will require careful consideration of the risks and benefits, as well as coordination with the infant's family.
Section 5
New Diagnostic Results:
The surgical team decided to perform an echocardiogram to assess the infant's heart structure and function. The echocardiogram results confirmed the diagnosis of Transposition of the Great Vessels, revealing a ventricular septal defect and a patent ductus arteriosus. These abnormalities were allowing the mixing of oxygenated and deoxygenated blood, which was helpful for the infant's survival thus far. However, the team also noted that the oxygen concentration in the infant's blood remained dangerously low, despite the mixing of blood.
The team also performed a chest X-ray, which showed cardiomegaly, indicating that the infant's heart was enlarged from working harder to pump blood. The X-ray also showed increased pulmonary vascular markings, suggesting increased blood flow to the lungs. These findings, coupled with the infant's deteriorating condition, made it clear to the surgical team that they needed to proceed with surgery as soon as possible. This decision was discussed with the family, who were understandably distressed but agreed to the proposed plan. The team reassured them that this was the best course of action for their baby's survival.