Care of the critically ill child: endotoxin shock.

F OR practical purposes we may consider that endotoxins of gram-negative bactena are the cause of endotoxic shock. In general, endotoxins are produced by bactena which form smooth colonies. However, it should be mentioned that small quantities of endotoxin have been found in colonially rough, gram-negative rods and in some gram-positive bacteria. Endotoxins are found in the outer layers of the bacterial cell wall. They are so closely associated with other constituents of this structure that their isolation requires strong chemical treatment.1 Endotoxins are macromolecules which readily form cornplexes with each other and with other macromolecules. The two major constituents of endotoxins are lipids and polysacchanides. Endotoxins also contain a small percentage of peptides, so we may consider that endotoxins are lipid-polysaccharide-peptide macromolecules. All endotoxins contain phosphorus also. The polysacchanide moiety is composed of a number of different carbohydrates, such as glucose, galactose and mannose, as well as pentoses, heptoses, and hexosamines.2 Also present are di-deoxy hexoses, which are found only in endotoxins. The lipid moiety contains even-nurnbered saturated and unsaturated fatty acids. The chemical constituents of endotoxins are arranged in three major zones in the macromolecule : the polysacchanide, the lipid-rich, and the amino acid-rich moieties. The backbone of the molecule is polysaccharide, to which are attached amino acids. The fatty acids are also attached to the carbohydrate backbone; these are ester bound to OH groups or amide bound to NH2 groups of the carbohydrate, probably through such compounds as glucosamine.2 The endotoxin molecule is unique in its fatty acid-carbohydrate linkages, which have not been found in any other natural substance. Phosphoric acid is found in both the lipid and carbohydrate moieties. Endotoxins elicit, directly or indirectly, a large number of reactions affecting many organ systems of the host. It seems very likely that most of these toxic reactions are caused by the presence of the lipid moiety, particularly the long chain fatty acids. Rough mutant, gram-negative bacteria ( which contain no polysaccharide moiety) have been shown to contain endotoxins which have full endotoxic action. The poiysacchanide moiety probably corresponds to the 0 antigen of the gram-negative bacilli. This portion of the macromolecule determines the serologic specificity of the organism. The peptide moiety appears to have little, if any, endotoxic activity, since removal of this portion of the molecule does