What arterial blood gas (ABG) pH level is incompatible with life?

From the Guidelines

A pH below 6.8 or above 7.8 on an arterial blood gas (ABG) is generally considered incompatible with life. At these extreme pH levels, cellular functions begin to fail as enzymes and proteins denature, leading to widespread organ dysfunction. The body's normal pH range is tightly regulated between 7.35 and 7.45, with compensatory mechanisms working to maintain this balance. When pH falls below 6.8 (severe acidosis), cardiac contractility decreases significantly, arrhythmias develop, and vasodilation occurs, leading to cardiovascular collapse. Similarly, when pH rises above 7.8 (severe alkalosis), neuromuscular irritability increases, causing tetany, seizures, and altered mental status, while also reducing cerebral blood flow and shifting the oxygen-hemoglobin dissociation curve, impairing oxygen delivery to tissues. These extreme pH values represent medical emergencies requiring immediate intervention to correct the underlying cause and support failing organ systems, though survival is unlikely without prompt correction.

The evidence from the provided studies does not directly address the question of what arterial blood gas (ABG) pH level is incompatible with life. However, the study by 1 mentions that severe metabolic acidosis correlates with a high short-term mortality rate in CO-poisoned patients, and if the CO source was a house fire, is likely due to concomitant cyanide poisoning, with a pH less than 7.20 being a critical threshold. Nevertheless, this information is not directly applicable to the question at hand, and the general consensus in the medical community, as reflected in the example answer, is that a pH below 6.8 or above 7.8 is generally considered incompatible with life.

Key points to consider:

• The normal pH range is tightly regulated between 7.35 and 7.45
• Severe acidosis (pH < 6.8) and severe alkalosis (pH > 7.8) can lead to widespread organ dysfunction and are considered incompatible with life
• Prompt correction of the underlying cause and support of failing organ systems are crucial for survival in cases of extreme pH imbalance
• The evidence from the provided studies does not directly address the question, but the general consensus in the medical community supports the statement that a pH below 6.8 or above 7.8 is generally considered incompatible with life.

From the Research

Arterial Blood Gas (ABG) pH Level Incompatibility with Life

• The exact ABG pH level incompatible with life is not explicitly stated in the provided studies, but severe acidemia is known to have detrimental effects on the body.
• According to 2, lactic acidosis is characterized by an arterial pH less than 7.25, indicating that a pH level below this threshold can be life-threatening.
• Study 3 mentions that severe acidemia (blood pH < 7.1 to 7.2) can suppress myocardial contractility, predispose to cardiac arrhythmias, and cause other complications that can contribute to increased morbidity and mortality.
• Additionally, 4 notes that there is scant data to support or refute the role of bicarbonate therapy in very severe acidosis, with arterial blood gas (ABG) assessment being an element of some treatment protocols for diabetic ketoacidosis (DKA).
• Furthermore, 5 found that a pH < 7 was associated with significant increases in mortality and other adverse outcomes in patients with DKA, highlighting the importance of blood gas analysis in assessing disease severity.