The pathophysiology of myocardial infarction

Answer

Assignment 2: Case Study

Question 1

The pathophysiology of myocardial infarction had advanced in Ben and this profoundly affected his cardiopulmonary functions. Consequently, there are specific assessments that should be done to ensure the management strategies are effective, and there is no further development of complications. Risk assessment should be conducted before commencing the therapy. The CPAP is not a ventilator and therefore, the work of breathing will remain with the patient's respiratory functions. Therefore, nursing assessment should focus on Ben’s vital signs, capnography, SpO₂, and his clinical responses.  The assessment is to ensure that Ben is stable while using the CPAP respiratory support. The nurse should conduct a physical assessment to examine the heart rate, respiratory rate, compliance with the therapy, and the work of breathing (The Royal Children's Hospital Melbourne, 2015). The CPAP device itself should also be assessed for its ventilation settings, alarm settings, battery back-up, and humidification settings. Hygiene is a very important component of patient safety. Therefore, the level of oral hygiene should also be assessed to prevent contraction of infections via the mask.

The most important assessment would be the assessment of Ben’s tissue oxygenation status. Low oxygenation status of tissues would be an important marker of respiratory failure. The clinical responses such as CO₂ levels in the blood can be used to evaluate improvements or deteriorations while using CPAP. Lack of respiratory function improvements can necessitate the need for assisted ventilations or intubation. CPAP is also associated with complications such as rupture of respiratory airways or alveoli. Any sign of such complications such as hemoptysis should be followed by an immediate removal of the CPAP. Therefore, close monitoring of the patient would be important to prevent any morbidity or mortality associated with the use of CPAP supportive device.

The non-invasive CPAP had advantages and disadvantages in its use in ventilation. According to the American Academy of Otolaryngology-Head and Neck Surgery (2015), the advantages of CPAP are the facts that CPAP is non-surgical and it is the most effective management strategy for apnea. Therefore, CPAP would be effective in controlling sleep apnea-related problems such as hypertension and heart disease. Additionally, the CPAPA would open up all the alveoli fully to receive maximum oxygenation. The other advantages of CPAP are less susceptibility to MRSA infections, low cost of equipment, and lack of ICU admission requirement (Mattera, 2010). On the other hand, the disadvantages of CPAP use are nasal congestion, mask discomfort, throat and nose dryness, and its constrictive nature for travelers because it has to be used every night (American Academy of Otolaryngology-Head and Neck Surgery, 2015). Therefore, these pitfalls might reduce future compliance to the use of CPAP. The immense positive pressure in the alveoli can also create dead spaces that decrease the flow of blood in the lungs. Therefore, some gas will occupy alveoli spaces and still fails to cross the capillary walls. There is also a potential risk of damage to the alveoli due to the continuous positive pressure in the airway. For instance, rupture of the walls of the alveoli can cause air to move into the thorax and the lung tissues leading to a pneumothorax. However, benefits of CPAP outweighs its potential risks and therefore, CPAP would be the appropriate management to improve Ben’s acid-base and oxygenation status.

Considering the benefits and disadvantages of CPAP, several nursing implications can be adduced on the use of CPAP support. First, nurses should acknowledge the various complications of CPAP use to support patients. Troubleshooting the complications can be done through assessing patient for adequacy in ventilation and conducting regular medical reviews. Patients should also be educated on the use of CPAP facial mask so that they adhere to the requirements and stop unnecessary anxiety. Additionally, nurses can educate caregivers and parents of patients on the principles behind the use of CPAP and its importance for the recovery of the patient. Such education would motivate caregivers to be supportive to the patient. Nurses should also participate in infection control while using CPAP by ensuring the mask is always clean. Most importantly, nurses should meet academic qualifications on the use of CPAP machinery.

The CPAP will have some physiological effects on Ben’s acid-base balance and oxygenation status. According to Hall (2015), venous return is supported by the negative thoracic pressure. Therefore, the continuous positive airway pressure can cause positive pressure in the thorax and reduce venous return. A reduction in venous return results in low cardiac output that can lead to decreased blood flow to tissues in patients with cardiac failure like Ben. Therefore, caution must be taken in the use of CPAP for supporting Ben's respiratory function to ensure his cardiac function is kept optimal. The positive pressure will ensure enough oxygen is present in the lungs and at a greater pressure top diffuse across the capillary walls in the lungs. Therefore, the amount of oxygen transferred from air that Ben breaths into his blood would increase, and oxygenation of the patient will be improved by the continuous positive pressure. Gaseous exchange is also improved by opening up the alveoli in the lungs. Therefore, more CO₂ will diffuse into the alveolar spaces and finally into the atmosphere. The re-expanding of alveoli sacs under positive pressure would improve ventilation/perfusion matching in the lungs and increase the gaseous-exchange time (Open Anesthesia, 2016). Consequently, more oxygen would diffuse into the blood as more CO₂ diffuses out to the lungs. As a result, hypoxia will reduce, and the increased CO₂ concentration in the blood will also decrease. The level of acidosis improves as more CO₂ diffuses into the lungs. Therefore, the blood will become less acidic.

Question 2

Ben has progressed to the state of cardiogenic shock. The physical assessment findings are linked to the pathophysiology of cardiogenic shock. Cardiogenic shock presents when the heart cannot pump enough blood to meet the needs of all the tissues. Barrett, Barman, & Boitano (2010) posit that cardiogenic shock is caused by the inadequate pumping of the heart due to myocardial abnormalities. Therefore, the principal basis for the pathophysiology of cardiogenic shock is the incompetence of the heart to pump blood to all the tissues. In the case of Ben, he suffered a myocardial infarction leading to the death of some of the cardiac cells. Therefore, his myocardium, especially the left ventricle, was incapable of pumping adequate blood.

The first observation in the assessment is a tachycardia of 135beats per minute. The heart rate was also irregular. Tachycardia presented as a compensatory mechanism due to the low cardiac output associated with the shock. The inadequate pumping of the heart ultimately resulted in reduced preload due to a decrease in venous return that depends on the total blood pressure. However, blood pressure dropped due to the low myocardial contractility presenting during the shock. Therefore, compensatory tachycardia presented to sustain adequate blood flow out of the heart. The blood pressure dropped to as low as 78/47mmHg while the average normal blood pressure for an adult is 120/80mmHg (Hall, 2015). The decrease in blood pressure was due to low contractility of the myocardium because some of the cardiac muscles had died following the STEMI leading to the cardiogenic shock. Hall (2015) further asserts that blood pressure is calculated as cardiac output multiplied by the total peripheral resistance. However, the cardiac output would reduce due to the low myocardial contractility. Therefore, blood pressure reduced as well.

The next observation was an increase in the respiratory rate to 36 breaths per minute. According to Johns Hopkins Medicine (2016), the normal respiratory rates for a resting adult can range from 12 to 16 breaths per minute. Therefore, Ben’s respiratory rate trebled. The immensely increased breathing rate was due to the hypoxic and hypercapnic stimuli to the respiratory center in the brain stem. The poor oxygenation of tissues leading to hypoxia was due to the decrease in afterload related to the low cardiac output due to the reduced myocardial contractility. Hypoxia is one of the basic stimuli for increasing the rate of breathing (Barrett, Barman, & Boitano, 2010). However, the breathing was shallow due to the exhaustion of the respiratory muscles.

The decreased cardiac output also resulted in the low SpO₂ to 86%. The capillary refill and increased JVP were also related to the low capacity of the left ventricle to pump blood out of the heart. The JVP increase is a direct indication of an increase in the central venous pressure following the cardiogenic shock. Cardiogenic shock presents with decreased ability of the heart to pump blood out of the heart. Therefore, positive pressure is created inside the atria because there is no room for the incoming blood. The internal jugular vein used to measure JVP is directly linked to the superior vena cava without the presence of any valves (Chua, Parikh, & Fergusson, 2013). Therefore, an increase in the central venous pressure in the right atrium will be reflected by an increase in the JVP. The capillary refill time also increased to more than 3 seconds due to the hypoperfusion. The low contractility of the myocardium reduces cardiac output and blood pressure. Therefore, blood will not be able to perfuse into the tissues efficiently. The crackles heard in the assessment were suggestive of pulmonary congestion. As such, the heart failure resulted into pulmonary edema due to the incapability of the ventricles to pump blood out of the heart. The blood flowing into the left atrium from the lungs was blocked due to lack of enough room because less blood is pumped out. Consequently, pulmonary edema resulted because the pressure created in the pulmonary capillary walls led to fluid flux into the pulmonary interstitial tissue.

The observations made at each tissue level resulted from the hypoperfusion of those tissues due to the decreased blood pressure. There was hypoperfusion of all the tissues including the myocardium itself. The drop in coronary perfusion increased his risk of further complications such as cardiac arrest. Cardiogenic shock decreases cardiac output thereby reducing blood pressure. Consequently, the flow of blood into tissues will reduce. Cerebral hypoperfusion is the sole reason for Ben’s decreased level of consciousness and confusion. The brain was not receiving enough blood, and therefore, cerebral functions started diminishing. The gastrointestinal perfusion will also be compromised to sustain blood supply to other important organs such as the brain and liver. Therefore, it can be deduced that the prognosis of Ben's cardiogenic shock is the death of brain tissue, damage to gastrointestinal mucosa, and progressive death of the cardiac tissue. Ben requires critical care to sustain his tissue perfusion.