top of page



Sepsis is a life threating reaction to an infection. it happens when your immune system over reacts to an infection and starts to damage your body's own tissue organs. you cannot catch sepsis from another person. Sepsis is sometimes called septicemia or blood poisoning.


An arterial blood gas analysis (ABG) measures the balance of oxygen and carbon dioxide in blood to see how well lungs are working. It also measures the acid-base balance in the blood. Kidney and lungs work to keep your acid base levels in balance.

Normal Values:

pH -- 7.35 -7.45

PaCo2 -- 35 -45 mm Hg

HCO3 -- 22-26 mEq/L

Below Normal Above

PH < 7.35 7.35-7.45 PH >7.45

Acidemia Alkalemia

Paco2 <35 35-45 Paco2 >45

Respiratory alkalosis Respiratory acidosis

Hco3 > 22 22-26 Hco3 >26

Metabolic acidosis Metabolic alkalosis

Metabolic Acidosis:  When the pH and HCO3 are below the normal range and PaCO2 is normal, it is called Metabolic Acidosis.

Low pH, low bicarbonate (HCO3), normal PaCO2.

Metabolic Alkalosis: When the pH and HCO3 are above the normal range and PaCO2 is normal, it is called Metabolic Alkalosis.

High pH, high bicarbonate (HCO3), normal PaCO2.

Respiratory Acidosis: When the pH is below the normal range, PaCO2 is above the normal range and HCO3 is normal, it is called Respiratory Acidosis.

Low pH, high PaCO2, normal bicarbonate (HCO3).

Respiratory Alkalosis: When the pH is above the normal range, PaCO2 is below the normal range and HCO3 is normal, it is called Respiratory Alkalosis.

High pH, low PaCO2, normal bicarbonate (HCO3).

Here this pie chart shows the ABG ranges across the sepsis patients ,in middle circle shows the total no of patients affected in ABG during sepsis .the outer circle shows the ranges between the patients . The size is fixed automatically based on the count of patients.

I.E: Metabolic Acidosis 47 patients affected

Metabolic Alkalosis 26 patients affected

Respiratory Acidosis 42 patients affected

Respiratory Alkalosis 18 patients affected


Septic shock is a serious medical condition that occurs when an overwhelming infection leads to life-threatening low blood pressure. It is a type of distributive shock, where there is widespread dilation of blood vessels and impaired distribution of blood flow throughout the body. Septic shock typically results from a severe bacterial infection, although it can also be caused by other pathogens such as viruses or fungi.

  1. Definition: Septic shock is the last and most dangerous stage of sepsis. Sepsis itself can be divided into three stages: sepsis, severe sepsis, and septic shock.

  2. Symptoms: Early signs of sepsis can include a fast heart rate, fever or hypothermia (low body temperature), shaking or chills, warm, clammy, or sweaty skin, confusion or disorientation, and hyperventilation (rapid breathing). When sepsis progresses to septic shock, additional symptoms may include very low blood pressure, lightheadedness, little or no urine output, heart palpitations, cool and pale limbs, and a skin rash.

  3. Causes: Any infection can lead to sepsis, which can then develop into septic shock if it worsens. Common infections originate from bacteria, viruses, or fungi and can start anywhere in the body, such as the lungs, bladder, or stomach.

  4. Risk Factors: People with weakened immune systems, including newborns and those over age 65, are at higher risk for septic shock.

Key features of septic shock include:

  1. Systemic inflammation: The body's immune response to the infection can lead to widespread inflammation, which can cause damage to organs and tissues.

  2. Hypotension: Low blood pressure occurs as a result of vasodilation and decreased vascular tone, leading to inadequate blood flow to vital organs.

  3. Organ dysfunction: In severe cases, septic shock can lead to multiple organ dysfunction syndrome (MODS), where organs such as the lungs, kidneys, liver, and heart fail to function properly.

  4. Lactic acidosis: Inadequate tissue perfusion can lead to the accumulation of lactic acid in the bloodstream, contributing to metabolic acidosis.

ABG (arterial blood gas) compensation based on the pH and other parameters. These terms help us understand how the body responds to acid-base imbalances:

  1. Compensated:

  • Definition: In compensated situations, both the pH and one other parameter (either CO₂ or HCO₃⁻) are abnormal.

  • Explanation: The body actively tries to normalize the pH by adjusting the other parameter.

  • Example:

  • If the pH is low (acidic), the body may increase ventilation (respiratory compensation) to decrease PaCO2 (partial pressure of carbon dioxide).

  • Alternatively, if the pH is high (alkaline), the kidneys may retain or excrete bicarbonate ions (metabolic compensation) to restore balance.

2.Fully Compensated:

  • Definition: In fully compensated situations, the pH returns to the normal range, and both CO₂ and HCO₃⁻ are also within the normal range.

  • Explanation: The body successfully restores acid-base balance.

  • Example:

  • If the pH was initially low due to metabolic acidosis, compensatory mechanisms (such as increased ventilation and kidney adjustments) bring it back to normal.

3.Partial Compensation:

  • Definition: When the pH is abnormal, and the body is attempting to bring the other parameter toward normal, but it hasn’t fully succeeded yet.

  • Explanation: The compensatory response is ongoing but hasn’t completely restored balance.

  • Example:

  • If the pH remains low (acidic), but the kidneys are actively retaining bicarbonate ions, it’s a partial compensation.

4. Uncompensated:

  • Definition: In uncompensated situations, only one parameter (either CO₂ or HCO₃⁻) is abnormal without the other attempting to compensate.

  • Explanation: The body hasn’t initiated compensatory mechanisms.

  • Example:

  • If the pH is low (acidic) due to respiratory acidosis (elevated PaCO2), but the kidneys haven’t adjusted bicarbonate levels, it’s uncompensated.

Conclusion for ABG analysis in sepsis:

In sepsis, arterial blood gas (ABG) analysis plays a crucial role in assessing the patient’s condition. Here are some key points regarding ABG analysis in sepsis:

  1. Acid-Base Status: ABGs can reveal information about the patient’s acid-base balance. Acidosis (low blood pH) may be present due to metabolic changes associated with sepsis. Monitoring the pH value is essential.

  2. Oxygenation: ABGs help assess hypoxemia (low oxygen levels in the blood).Supplemental oxygen should be provided to sepsis patients with indications for oxygenation. Continuous monitoring of oxygen saturation using pulse oximetry is recommended.

  3. Hypercapnia: ABGs may also indicate elevated carbon dioxide (CO2) levels (hypercapnia).Monitoring CO2 levels is important for managing respiratory function.

  4. Imaging: In addition to ABGs, imaging targeted at the suspected site of infection is warranted. This may include chest radiography or computed tomography of the chest and/or abdomen.

145 views3 comments

Recent Posts

See All


Rated 0 out of 5 stars.
No ratings yet

Add a rating
Feb 13
Rated 4 out of 5 stars.

Well presented. Nice blog.

Replying to

Thank you



bottom of page