Heavy weight on body parts may partially or completely cut off blood flow. Decrease in oxygen supply leads to anaerobic metabolism, skeletal muscle tissue begins to break down. As muscle cells die, they absorb sodium, water and calcium; releases potassium, myoglobin, phosphate and other toxins. When a patient is released from weight, blood flow is returned and these chemicals circulate throughout the body. Resulting in shock, acute renal failure, cardiac arrest and other systemic symptoms.