Sleep disturbance after major surgery is common, and some people assume anesthesia is the cause. That is probably wrong.
The “surgical stress response“, the body’s hormonal and metabolic response to the trauma of surgery, is quite profound and has an important effect on the subsequent amount and quality of sleep. The bigger the surgery, it seems, the more significant is the stress response and the accompanying sleep disturbance.
During the stress response, hormones from the pituitary gland are released, and the sympathetic nervous system is activated (adrenaline and its companion “fight or flight” hormones). Metabolic changes include increased blood sugar, and breakdown of body protein. Injured tissues release cytokines and other potent chemicals associated with inflammation.
Pain, and the medications used to treat pain, sedatives, food deprivation, fever, psychological factors, age, and a person’s usual sleep profile all affect sleep after surgery.