Question

why O2 saturation levels is low on a septic shock? please provide pathophysiology and references.

Answer 1

In patients experiencing septic shock, oxygen delivery is relatively high, but the global oxygen extraction ratio is relatively low. Oxygen uptake increases with rising body temperature despite a fall in oxygen extraction.

Maldistribution of blood flow, disturbances in the microcirculation, and, consequently, peripheral shunting of oxygen are responsible for diminished oxygen extraction and uptake, pathologic supply dependency of oxygen, and lactate acidemia in patients experiencing septic shock.

patients with sepsis who have low oxygen extraction and elevated arterial lactate levels, oxygen uptake depends on oxygen supply over a much wider range than normal. Therefore, oxygen extraction may be too low for tissue needs at a given oxygen supply, and oxygen uptake may increase with a boost in oxygen supply—a phenomenon termed oxygen uptake supply dependence or pathologic supply dependence. This concept is controversial, however; some investigators argue that supply dependence is an artifact rather than a real phenomenon.

PATHOPHYSIOLOGY

•invasion of microorganism

•release of endotoxins

•endotoxin release of inflammatory mediators

•mediators causes vasodilatation and capillary

permlabily

•massive dilation

•organ hypoperfusion

•decrese venous return

•decrese end diastolic volume.

A key role in the development of severe sepsis is played by an immune and coagulation response to an infection. Both pro-inflammatory and anti-inflammatory responses play a role in septic shock. Septic shock involves a widespread inflammatory response that produces a hypermetabolic effect. This is manifested by increased cellular respiration, protein catabolism, and metabolic acidosis with a compensatory respiratory alkalosis.

Reference

•Levis's Medical surgical nursing 3rd South Asia Edition

•Brunner and Suddarth's Medical surgical nursing Volume-1

•Joyce M BlackM Medicalsurgical nursing