Pyrogenic Shock: Definition, Signs, Symptoms, Influence of Pyrogens and Detection Tests

It is characterized by a feverish reaction due to the presence of pyrogens (agents that increase body temperature).

It can be caused by contamination of the solution and materials used in procedures that have had intravenous contact (puncture).

Signs and symptoms

The signs and symptoms are:

  • Hypotension .
  • The skin is generally pale, sweating, and may have peripheral cyanosis.
  • Hypothermia .
  • Fast and thin pulse.
  • Emotional changes, which can present agitation, mental confusion or apathy.
  • Tachypnea and superficial.
  • Oliguria.

What are pyrogens?

Pyrogens are substances that can cause fever . The most common pyrogens are endotoxins, which are lipopolysaccharides (LPS) produced by Gram negative bacteria such as E. Coli.

The amoebocyte lysate (LAL) test is used to detect endotoxins. Another assay that detects endotoxins is the recombinant factor C assay.

The advantage of the latter is the lack of positive tests for glucan-containing substances, a problem sometimes seen in post-processing when traces of carbohydrates are released from chromatographic resins.

The best-studied pyrogen is lipopolysaccharide (LPS, also known as endotoxin), which is found in the membrane of bacteria. Release of LPS from bacteria occurs after cell lysis and can occur as a result of sterilization.

Good examples of pyrogen-producing gram-negative bacteria are:

  • Escherichia coli (E. Coli).
  • Proteus.
  • Pseudomonas
  • Enterobacter.
  • Klebsiella.

During gram-negative sepsis, endotoxin stimulates host macrophages to release inflammatory cytokines, and excessive inflammation causes multiple organ failure and death.

Endotoxins are therefore ubiquitous pathogenic molecules that are detrimental to the pharmaceutical industry and the medical device community.

Endotoxins result from high levels of gram-negative bacterial bioburden. It is difficult to remove endotoxins from products once they are present.

The most common depyrogenation procedures for physical components include incineration and removal by washing (also called dilution), which are impractical after terminal sterilization.

Pyrogen test

As previously explained, pyrogens include endotoxins (toxins derived from gram-negative bacteria) and non-endotoxic pyrogens (substances derived from microorganisms other than gram-negative bacteria, or from chemicals).

Iryokiki-Shinsa mentions the pyrogen test, which uses a rabbit, which can detect endotoxins and non-endotoxic pyrogenic substances, and the in vitro endotoxin test, widely used as a method for detecting microbial contamination (endotoxins).

The pyrogen test with a rabbit involves administering a physiological saline extract of the test substance intravenously and determining the existence of pyrogens by the increase in body temperature after administration.

In vitro

The endotoxin test includes the gelation method, which indexes the formation of a gel that occurs through endotoxins derived from gram-negative bacteria acting on a lysate test solution prepared from limulus amebocyte lysate, and the methods turbidimetric and colorimetric. that index of optical changes.

The selected test method differs depending on the purpose of the test (a limit test to verify the default values ​​below, a quantitative test to verify the content) and the characteristics (color, existence of reaction interference factors) of the prepared extract. .

Endotoxins and non-endotoxic pyrogens show mechanisms of increase in body temperature and behavior that are complex and indistinct and it is necessary to select the extraction conditions according to the properties of the material and the purpose of use of the product.

The test method given in Iryokiki-Shinsa No.36 is fundamentally a criterion of determination equivalent to the pyrogen test method included in the general test methods listed by the Japanese Pharmacopoeia.

It differs slightly from the determination standards of the United States Pharmacopoeia (USP) or the European Pharmacopoeia (EP). In any case, the test is carried out taking into account various terms and conditions, such as the content, characteristics, application, etc., of the raw materials of the medical device.

The test substance or its extract is administered into the atrial vein of a rabbit, the body temperature (rectal temperature) is measured continuously for 3 h, and any difference from the reference body temperature is looked for.

When the body temperature (rectal temperature) of at least 2 out of 3 animals increases 0.6 ° C or more within 3 h after administration, the result is considered positive for pyrogens.

Although it cannot be considered a positive result in itself, if an animal shows a body temperature increase of 0.6 ° C or the sum of the maximum temperature of three animals exceeds 1.4 ° C, a second test should be performed.

Five animals are used for this second test and if two or more animals show an increase in body temperature of 0.6 ° C or more, the result is considered positive. h after administration, the result is considered positive for pyrogens.

Although it cannot be considered a positive result in itself, if an animal shows a body temperature increase of 0.6 ° C or the sum of the maximum temperature of three animals exceeds 1.4 ° C, a second test should be performed.

Five animals are used for this second test and if two or more animals show an increase in body temperature of 0.6 ° C or more, the result is considered positive.