Care of the COVID-19 Patient

Upon completion of this section, you will be able to:

1. Identify signs and symptoms of acute respiratory events
2. Interpret arterial blood gas results and identify implications for patient care
3. Identify appropriate primary nursing interventions for the IMCU patient experiencing hypoxia

Care of the Hypoxic Patient (ABG Analysis)

Acid-base balance is essential to maintain homeostasis in the body. This balance contributes to protecting cellular function and tissue perfusion and any disruption in this balance can result in poor outcomes for acutely ill patients (Wang et al., 2019). It is therefore imperative that acid-base status is monitored closely, and interventions implemented to restore balance if possible. The test to monitor this balance is the arterial blood gas (ABG). ABGs outline the cause and extent of an acid-base disturbance and guide the selection of appropriate treatment strategies and nursing care. ABGs can also be used to evaluate the effectiveness of implemented strategies and the patient’s overall progress.

Arterial Blood Gases

Review the following:

The arterial blood gas (ABG) is the gold standard in evaluating acid-base balance, oxygenation and ventilation in critically ill patients (Hamidreza et al., 2018).

Normal Parameters:

Assessment of Ventilation

The carbon dioxide level in the blood (PaCO₂) is the respiratory parameter of the blood gas and provides information on the client’s ventilation. If PaCO₂ levels are greater than 45 mmHg then the client is hypoventilating; if the PaCO₂ levels are less than 35 mmHg then the client is hyperventilating. When the client is hyperventilating it is said that they are “blowing off” their PaCO₂, and therefore it will be lower. When the client is hypoventilating it is said that they are “retaining” their PaCO₂ and therefore it will be higher.

Assessment of Oxygenation

PaO₂ - represents the partial pressure of oxygen dissolved in arterial blood. The normal range of 80-100 mmHg on room air usually indicates that the arterial blood is carrying adequate oxygen. It is important to note that although we classify hypoxemia at a PaO₂ of less than 60 mmHg, a PaO₂ less than 80 mmHg is considered abnormal and may require an intervention (e.g., supplemental oxygen).

SaO₂ - assesses the patient’s oxygenation status. SaO2 reflects the amount of oxygen carried on hemoglobin and is measured as a percentage, with a normal (room air, non-diseased person) SaO2 being greater than 97%. Each patient may have a different “normal” SaO2 so it is important to evaluate what is considered normal on an individual basis rather than a group norm. Pulse oximetry measures SaO2 and is referred to as SpO2 when the oximeter is used (Thijssen, Janssen, Jos, & Foudraine, 2019).

Assessment of Acid-Base Balance

pH - The concentration of hydrogen (H⁺) ions in the body indicates whether a solution is acidic or alkalotic. The pH and the H⁺ ion have an inverse relationship, which means that when the H⁺ ions go up, the pH goes down and vice versa. In arterial blood a pH below 7.35 indicates an acidic solution with more H⁺ ions. A pH higher than 7.45 indicates an alkalotic (base) solution and a low amount of H⁺ ions.

pH < 7.35 indicates an acidic state

pH > 7.45 indicates an alkalotic/basic state

PaCO₂

CO₂ in the blood combines with water to form carbonic acid and is considered an acid when interpreting acid-base balance. It represents the respiratory parameter of the acid-base relationship.

PaCO₂ > 45 mmHg, then the pH falls, RR will be low

PaCO₂ < 35 mmHg, the pH rises, RR will be high

HCO₃^-

The bicarbonate (HCO₃^-) level of the blood gas represents the metabolic parameter of acid-base balance. HCO₃^- is the main alkaline substance or base found in the blood. The regulation of HCO₃^- in the blood is managed by the kidneys.

HCO₃^- > 28 mmol/L, causes the pH to rise

HCO₃^-, < 21 mmol/L, causes the pH to fall

Acid-Base Physiology

The major buffer systems of the body that maintain acid-base balance are: the carbonic acid-bicarbonate system, the hemoglobin/oxyhemoglobin system, the protein system, and the phosphate system. The carbonic acid-bicarbonate system is the one measured by the arterial blood gas and will be our focus.

Respiratory System

The lungs can respond quickly to maintain pH by controlling the elimination of CO₂. When the body's pH becomes acidic, the rate and depth of respiration will speed up to eliminate CO₂ (acid). Conversely, when the pH becomes alkalotic (base), rate and depth of respiration are slowed to conserve CO₂ or acid.

Respirations     CO₂

Respirations     CO₂

Renal System

The renal system responds slowly, up to 18-24 hours, to changes in the pH. The kidneys control H⁺ and HCO₃^- by:

urinary excretion of H⁺ and conservation of HCO₃^- when blood is acidic, or

urinary excretion of HCO₃^- and conservation of H⁺ when blood is alkaline

Watch the following video on ABG interpretation:

To pump blood and perfuse tissues, the body requires adequate volume. Remember the concepts of determinates of cardiac output as they will be important to further understanding of how arterial lines work. Hemodynamic monitoring is one of the more advanced technologies for monitoring in the acutely ill client.

Upon completion of this module, the learner will be able to:

1. Identify patients who may require continuous blood pressure monitoring with an arterial line
2. Identify the equipment required and nursing responsibilities for arterial line insertion
3. Explain the set up, assessment and maintenance of an arterial line (basic pressure tubing and blood conservation tubing)
4. Recognize abnormal waveforms and describe appropriate troubleshooting
5. List potential complications of arterial lines

Common Principles for Arterial Line Monitoring

1. Single readings are not as significant as the trend of the pressure (e.g. is it increasing, decreasing, or staying stable).
2. Values must be interpreted in relation to the client’s history, clinical course, interventions, and other parameters (e.g., mean arterial pressure).
3. To obtain accurate values, the transducer must be levelled to the phlebostatic axis.

Arterial Line Insertion Site Advantages/Disadvantages

(CCNP, 2021)

The arterial waveform is a graphic representation of the ejection of blood from the left ventricle. This waveform is divided into the two components of arterial blood pressure: systole and diastole. The normal arterial waveform is characterized by: (a) an initial sharp rise (anacrotic limb), (b) a rounded top (systole), (c) a dicrotic notch on the downstroke (dicrotic limb) of the arterial waveform, and (d) a tapering off of the downstroke after the dicrotic notch (diastole). The highest point recorded corresponds to the systolic reading and the lowest point corresponds to the diastolic reading.

The square wave snap test is performed by:

1. pulling or squeezing the fast flush valve fully open;
2. holding it for one second;
3. quickly releasing the valve, allowing it to “snap” shut and
4. observing the change in waveform on the monitor.

Note: To prevent vasospasm and/or embolus, forceful or prolonged flushing should be avoided.

Watch the following video on ultrasound guided arterial line placement. Although this video is meant for physicians, it does a good job outlining why and how an arterial line is placed:

Watch the following video on how to set up an arterial line:

Note the following patient safety measures that need to be considered:

• Check your patient's coagulation status (INR, PTT and platelet levels) before removal of any line in a patient.
• Apply firm pressure to the insertion site for at least five minutes after removing the arterial catheter. Inspect the site for bleeding or hematoma formation which can lead to compromised perfusion to the extremity.
• Change the arterial catheter flush solutions and tubing every 96 hours to prevent infection. Heparin is not used with arterial lines in NS due to the risks of developing heparin induced thrombocytopenia (HIT).
• Check the patient status when a problem is suspected before proceeding on to examine the equipment or troubleshooting. This ensures that patient safety is always the priority.
• Use the minimal amount of blood discard prior to taking samples to avoid anemia. Blood conservation systems are used to minimize blood loss and may be cost effective in patients requiring multiple specimens.