[17][18][19][20][21][22][23][24][25][26][27][28][29][excessive citations] It is generally considered or hypothesized that a more invasive surgery, with extensive tissue trauma and noxious stimuli, triggers a more significant stress response.
[30][31][32][33][34][35] However, duration of surgery may affect the stress response which therefore may make comparisons of procedures that differ in time difficult.
[37][38] Loss of nitrogen (urea) was observed already in the 1930s in fracture patients by the Scottish physician David Cuthbertson.
The reason for the patients' catabolic response was not understood at the time, but later attention was turned to the stress reaction caused by the surgery.
[39][40] The evolutionary background is believed to be that a wounded animal increases its chance of survival by using stored energy reserves.