Oxygenation & Perfusion: Covid-19 Case Study

Oxygenation and Perfusion

Lower Respiratory Disorders

​Covid-19 Non-Fiction Case Study

NSG 452

​Our Patient

​Patient Data: JD

48 year old male

Health history: obesity, recent negative stress test performed for reports of angina, no other known medical conditions

Occupation: butcher

Hobbies: home improvement projects, fishing

Medications: none

Drug Allergies: none

Social: married, 6 children

Vaccination status: unvaccinated

​Initial Illness

​Initial symptoms leading to testing and diagnosis: fatigue, low grade fever, loss of taste and nasal congestion.

Fairly uneventful clinical course until day 8 post diagnosis.

​

Day 8: the patient’s wife takes him to the local emergency department due to increasing shortness of breath and low oxygen saturations despite supplemental oxygen and nebulizer treatments at home.

​

JD is admitted to a medical COVID treatment floor and placed on a non-rebreather. He continues to desaturate and is subsequently placed on a heated and humidified high flow nasal cannula at 60 L/min.

Multiple Choice

In addition to high liter flow and the ability to administer 100% FiO2 what is another known advantage of high flow nasal cannulas?

• Positive end-expiratory pressure in the lower airways

• Cost reduction compared to low flow nasal cannulas

• Decreased need for staff training

• Increased physical mobility potential

​Rationale

​There are many advantages to high flow nasal cannulas including the creation of positive end-expiratory pressure in the nasopharynx as well as the lower airways. This allows for improved alveolar recruitment, increasing the effective available surface area within the lungs for gaseous diffusion both to and from the blood.

​

​High flow nasal cannulas are more expensive than traditional low flow nasal cannulas, require more training and education of staff, and reduce the potential for physical mobility (high flow cannulas essentially tie the patient to the wall/NIPPV machine).

​Hospitalization Continued

​It is now day 6 of hospitalization. JD has been fairly stable for the last several days. He continues to require alternating high flow nasal cannula therapy and NIPPV via BiPaP. He is receiving IV remdesivir, IV dexamethasone 6 mg daily as well as supportive treatment with zinc, vitamin C and vitamin D3.

​

​The next day JD’s respiratory distress increases and it becomes more and more difficult to maintain oxygen saturations above 85%. He becomes increasing tachypneic and his doctors decide he needs to be intubated. They are very concerned about respiratory muscle fatigue and his current oxygenation status. His wife is allowed into the hospital to see him before endotracheal intubation is initiated. She has not seen him since the day he came into the ED as no visitors are allowed for Covid-19 patients. 

Multiple Choice

What is the primary reason dexamethasone (Decadron) is administered in severe COVID-19 infections in adult hospitalized patients?

• Reduction of secondary infection risk

• Decreased prevalence of refractory hypotension

• Decreased severity of cytokine release syndrome

• Reduced incidence of arterial thrombosis aka "covid clots"

​Rationale

​Dexamethasone (Decadron) is given in severe covid-19 infections in hospitalized adult patients for the purpose of reduction of severity of cytokine release syndrome and the subsequent autoimmune destruction of the lungs.

​Post Intubation and Transfer to ICU

​Initially some improvement is seen in JD’s clinical status but this improvement is not sustained. He starts spiking fevers frequently and his WBC count jumps and continues to elevate. Pan cultures are ordered in order to find the etiology of the leukocytosis and pyrexia.

​ By rule out, JD’s care team decides he has developed a fungal infection (aspergillosis) in his lungs that is associated with Covid-19 infection and the use of corticosteroids. It is difficult to confirm the diagnosis of CAPA (Covid-19-associated pulmonary aspergillosis) because the symptoms are non-specific and testing requires a specimen from deep in the lungs.

He is started on voriconazole – the recommended first line treatment for intrapulmonary aspergillosis.

Multiple Choice

One particular challenge inherent to antifungal drug therapy includes:

• Multitude of drug-drug interactions

• High risk of nephrotoxicity

• Cardiac dysrhythmias

• Increased splenic sequestration of platelets

​Rationale

​Unfortunately, the vast majority of antifungal medications used in the US have many drug-drug interactions. The antifungal with the least drug interactions is fluconazole (Diflucan).

​

​Amphotericin B can be nephrotoxic but the commonly used -azole antifungals are not. Some may cause QT shortening or prolongation but this usually does not result in dysrhythmias. There is no evidence of increased sequestration of platelets due to antifungals.

​Continued Complications

​The severe Covid-19 infection compounded with a fungal pulmonary infection continues to wreak havoc on JD’s lungs. He remains on maximum or near maximum ventilatory support, has been proned several different times and paralyzed and sedated with cisatracurium, midazolam, propofol, and fentanyl. 

​

Most recent ABGs: pH: 7.26 PaCO2: 92.1 PaO2: 61.6 HCO3: 42.1 Base excess: 11.8

Most recent ventilator settings (prone position):

Assist Control with rate of 32

Tidal volume: 330 ml

FiO2: 90%

PEEP: 12.5

​Acid-Base Balance Overview

​Let's concentrate on JD's ABGs and ventilator settings for a minute...

​

Most recent ABGs: pH: 7.26 PaCO2: 92.1 PaO2: 61.6 HCO3: 42.1 Base excess: 11.8

​

Most recent ventilator settings (prone position):

Assist Control with rate of 32

Tidal volume: 330 ml

FiO2: 90%

PEEP: 12.5

​In most cases, a PaCO2 in the 90s would equivocate to a pH so low it's incompatible with life, but in JD's case...

​The Covid-19 "new normal"

​Definitive Airway Placement & Organ Failure

​After approximately 17 days on the ventilator, JD’s liver enzymes become and subsequently remain elevated indicating end organ damage (AST and ALT, 200s & 300s).

CRP remains elevated (18). A CT scan of the chest reveals moderate to severe pulmonary fibrosis, a CT of the head reveals no abnormalities.

​

On day 20 of being intubated with an ET tube, JD undergoes a tracheostomy procedure, the paralytics are discontinued but he remains on midazolam and fentanyl.

He is receiving enteral nutrition via a flexible, small-bore NG tube (dobhoff tube).

​End Organ Damage

​

What are potential reasons for the drastic increase in JD's liver enzymes?

​New Infections & Genetic Considerations

​Approximately 4 days after the trach is inserted JD is producing copious amounts of respiratory secretions and is diagnosed with MRSA in his sputum, he is subsequently treated with vancomycin and cefepime.

​

*Genetic consideration: while JD is intubated in the ICU, his older brother succumbs to Covid while hospitalized in another part of the state. Like JD, he was not considered to be in the “high risk” category for death from Covid-19.

​Benzodiazepine Withdrawal

​Efforts are made to wean JD from the midazolam to assess neurologic and cognitive function and attempt a spontaneous breathing trial (SBT). The midazolam is decreased too rapidly and benzodiazepine withdrawal ensues. One SBT was done lasting approximately 15 minutes prior to the withdrawal.

​

He is placed back on midazolam and is unable to do more SBTs but he is no longer on max ventilatory support (FiO2 requirements are 70% – 80%, PEEP of 10) for the time being.

Multiple Select

What are typical signs and symptoms of acute benzodiazepine withdrawal?

SELECT ALL THAT APPLY.

• Tremors

• Depression

• Diaphoresis

• Palpitations and tachycardia

• Hypotension

​Rationale

Benzodiazepine withdrawal is ​characterized by sleep disturbances, irritability, increased tension and anxiety, panic attacks, hand tremor, sweating, difficulty in concentration, dry wretching and nausea, some weight loss, palpitations, headache, muscular pain and stiffness and a host of perceptual changes. Instances are also reported within the high-dosage category of more serious developments such as seizures and psychotic reactions.

​

​https://pubmed.ncbi.nlm.nih.gov/7841856/

​Sudden Decompensation

​3 days later JD experiences sudden decompensation at 0715 after being stable throughout the night shift. Pneumonia is suspected by his care team.

His oxygen saturation is in the 70s despite manual bagging by the pulmonologist in a desperate to reestablish adequate oxygenation, he is reparalyzed with cisatracurium and placed back onto maximum ventilatory support with FiO2 at 100% and PEEP at 15.

The next day severe, uncontrolled bleeding is noted coming from JD’s tracheostomy site as well as his mouth. Day 36 in the hospital, day 28 on ventilator he is made a DNR.

DIC panel rules out the presence of DIC

​Critical Thinking

​JD's DIC panel ruled out DIC as the cause of the profuse bleeding from his trach and mouth.

​

​Why else might this be occurring?

​Continued Developments

​Multiple follow up CT scans reveal bilateral pulmonary emboli followed by severe pulmonary fibrosis and eventually multiple pulmonary cavitations.

​Ventilator weaning is in progress and daily JD is able to be off the ventilator and on a humidified trach shield for at least a few hours.

​Case Conclusion

​A few days later JD develops a spontaneous pneumothorax that requires the placement of a chest tube. The next day he undergoes a VATS procedure. Another scheduled, serial bronchoscopy is performed a few days later and the BAL washing reveals a very rare fungal infection (pulmonary mucormycosis), it is generally associated with chronic immunosuppression and lacks effective therapies; the mortality rate of this fungal infection is reported as high as 80%.

​

After over 2 months in the hosp​ital JD requests comfort care and is discharged home with hospice.