When you read the words “coronavirus and the sofa score” during a period of shelter-in-place for COVID-19, your first thought will be “laying on a sofa watching Netflix.”
Wrong. SOFA is a medical metric called the SOFA score.
This column is about rationing of ICU care and ventilators. If/when hospital intensive care units (ICUs) become overwhelmed with too many coronavirus patients requiring ventilators, then ethical choices may need to be made. If there are “n” number of ventilators and “n+10” patients who need one, who gets a ventilator and who does not? Which patients have an excellent prognosis to live and which do not?
Will ICU beds and ventilators need to be rationed in the COVID-19 crisis?
In crisis areas like New York City and Italy’s Lombardy region, anxiety and fear abound. I’ve previously posted this video showing the stress at an Italian COVID-19 ward.
This week I was contacted by a reader in his 70s who had a history of heart disease. His anxiety regarding the coronavirus epidemic was so high he asked me if he purchased a ventilator for the local university hospital, could he be guaranteed it would be available for him if he needed it?
What data are available specifically for COVID-19 to address the question of which patients will have the highest ICU mortality?
Fei Zhou, MD et al published a retrospective study regarding COVID-19 patients from the Wuhan, China area in the medical journal Lancet. 191 patients were included in this study. 137 were discharged and 54 died in hospital.
Zhou measured data on each patient at the time of admission to the ICU. He discovered that the odds of dying in the hospital increased with:
A) increasing age,
B) a D-dimer level exceeding 1 mcg/L on admission, and
C) a higher SOFA score on admission to the ICU.
Of these three criteria:
- We’ve already heard that a higher age is a risk factor for dying from COVID-19. See chart above
- A high D-dimer level indicates that increased blood clotting is occurring. The D-dimer is not specific, and can correlate with a deep venous thrombosis, a pulmonary embolus, or other diagnoses which include increased blood clotting.
- What is a SOFA score? Read below:
SOFA stands for Sequential Organ Failure Assessment, and it quantifies the extent of a patient’s organ function or failure in six different organ systems: the lungs (respiratory), the heart (cardiac), the kidney (renal), the brain (neurological), the liver (hepatic), and the blood clotting system (coagulation). It’s used to predict ICU mortality based on lab results and clinical data. The higher the score, the worse the prognosis.
Let’s look at how each organ system is rated, first for a normal person like yourself, and secondly for a sick COVID-19 patient in the ICU:
Lung or respiratory failure is the most common failing system in sick COVID-19 patients. The SOFA respiratory score is based on the ratio of: your blood oxygen level (PaO2) divided by the percentage of oxygen that you’re breathing. Right now your blood oxygen level is approximately 90 mm Hg, and the percentage of oxygen in room air that you are breathing is 21%, or 0.21 as a decimal. Divide 90/0.21 = 428. From the chart above, you earn 0 points, which is good. A COVID-19 patient sick with pneumonia may have a low blood oxygen level of 50 mm Hg on 100% oxygen, or 1.0 as a decimal (100% oxygen is the most a ventilator can deliver). 50/1.0 = 50, which earns that patient a respiratory score of +4 points.
The cardiac score is based on how high or low your blood pressure is, and on what concentration of adrenaline-like medication is required to keep your blood pressure up to a safe level. The blood pressure metric used is the mean arterial pressure (MAP), which is your average blood pressure. Right now your blood pressure may be 120/80, which equates to a mean arterial pressure of 93. Because you require no medications to keep your mean blood pressure > 70, you earn 0 points. A sick COVID-19 patient with heart failure might require a high concentration of an epinephrine (adrenaline) drip to maintain their blood pressure. This would earn them a cardiac score of +4.
The renal score is based on now much urine a patient produces per day, or how high their blood creatinine level rises to. Normal urine output is at least of 0.5 milliliters/kilogram of body weight per hour. A 70 kilogram (154-pound) human makes a minimum of 840 milliliters of urine/day, which earns them 0 renal points. A sick COVID-19 ICU patient with renal failure may make less that 200 milliliters of urine per day, which earns them a renal score of +4 points.
The liver score is based on how high the bilirubin concentration is in the blood. Bilirubin increases as a liver fails. Your bilirubin is a normal concentration of 1.0 mg/dL, and you earn 0 points. A sick ICU patient with a failing liver may have a buildup of bilirubin in the blood. An elevation to a concentration of > 204 mg/dL earns them a liver score of +4 points.
The Glasgow Coma Scale (GCS) quantifies the level of consciousness. Because you are awake and reading this, let’s assume you have a perfect GCS of 15. This earns you 0 points. A comatose patient on a ventilator may have a score of < 6, which earns them a neurological score of +4 points.
The normal concentration of platelets in the bloodstream is > 150,000, or (150 X 103 microL), and if you’re normal individual you will earn a score of 0. A sick COVID-19 patient in the ICU may be bleeding for a variety of reasons, and be consuming platelets trying to cease bleeding. A low platelet count of (20 X 103 microL) earns them a coagulation score of +4 points.
Zhou wrote: “Older age, elevated D-dimer levels, and high SOFA score could help clinicians to identify at an early stage those patients with COVID-19 who have poor prognosis.”
What about rationing ICU care? Will older age or a higher SOFA score on admission impact a rationing of ICU care, that is, will older patients or patients with a very high SOFA score be denied a ventilator or an ICU stay? Will famous people or rich people score the last ventilators? I am doubtful this will happen in the ethical practice of medicine in the United States. But if the number of ICU patients greatly exceeds the number of ICU beds with ventilators, difficult choices may have to be made. Some patients may receive ventilators while others are denied ventilators. The Zhou data supports the premise that older patients and those with elevated organ failure scores on admission to the ICU have a worse prognosis. If ethical decisions are made, these two numbers (as well as an elevated D-dimer level) may be criteria which guide these difficult decisions.
Further research and data collection on COVID-19 patients in the hospitals and ICUs will give more detailed answers to these questions. Stay tuned.
I refer you to a fine and pertinent article written by Dr. Robert Truog, of the Harvard Center for Bioethics, entitled, “The Toughest Triage – Allocating Ventilators in a Pandemic,” published in the New England Journal of Medicine March 23, 2020.
The April 1, 2020 issue of The New York Times discusses the issue of rationing ICU care in New York City.