For severe bleeding, first press firmly on the wound with your hand; if this fails on limbs, apply a tourniquet and call 120 immediately

Cost: A twist-style tourniquet costs anywhere from a few dozen to over a hundred yuan; it can easily be stored in a car or first-aid kit. Learning how to position it above the wound, twist it until bleeding stops, and note the time takes just a few minutes.
In plain terms: Begin by pressing hard on the wound with your hand or a cloth; if bleeding on a limb persists, fasten a tourniquet and call 120 right away. Once applied, never loosen it. Among battlefield casualties, 90% who received a tourniquet before going into shock survived, compared to only 10% who got one after shock set in; all five patients who needed a tourniquet but did not receive one died. Position the tourniquet above the wound, twist it until bleeding ceases, and record the time. Never substitute shoelaces or ordinary rope. For neck or torso injuries, only compression is allowed—no tourniquets may be used.
Benefit: Over six years, 11 Level I trauma centers in Texas treated 1,026 patients with limb vascular injuries; 181 of them (17.6%) had a tourniquet applied prior to arrival. Unadjusted mortality rates were 3.9% for those with a tourniquet and 5.2% for those without. After adjusting for other factors, tourniquet use remained strongly linked to survival; the adjusted odds ratio was 5.86, with a 95% confidence interval ranging from 1.41 to 24.47. At a Baghdad field hospital, 90% of 232 injured patients who received a tourniquet before shock survived, versus just 10% who got one after shock occurred; all five patients needing a tourniquet but not receiving one perished, while 87% of those with a tourniquet survived. The recommended sequence is: direct manual compression using any cloth or towel → if bleeding on a limb persists, apply a tourniquet → call 120 → never loosen it.
Evidence grade: A
Sources:Teixeira PGR 等 (2018). Civilian Prehospital Tourniquet Use Is Associated with Improved Survival in Patients with Peripheral Vascular Injury. Journal of the American College of Surgeons. https://doi.org/10.1016/j.jamcollsurg.2018.01.047 ; Kragh JF 等 (2009). Survival with emergency tourniquet use to stop bleeding in major limb trauma. Annals of Surgery. https://doi.org/10.1097/SLA.0b013e31818842ba ; 中国医师协会急诊医师分会等 (2020). 止血带的急诊应用专家共识. 中华急诊医学杂志 29(6):773-779：「院前急救时，止血带一旦使用则不建议松开，除非得到可以替代的彻底止血的救治」「最长使用时间不应超过2 h。但如果客观情况无法到医院救治或者无替代止血办法，则在得到正规救援前不解除止血带」. https://doi.org/10.3760/cma.j.issn.1671-0282.2020.06.006，全文 http://www.cem.org.cn/rhtml/20200606/index.htm
Notes: Never use thin materials such as rope or shoelaces as tourniquets; they cannot sufficiently constrict arteries and may cut the skin. Once a tourniquet is applied, do not loosen it periodically to “release blood flow.” Compression only applies to neck and torso injuries—never a tourniquet. No amputations resulted from tourniquet use in the battlefield data; transient nerve paralysis occurred in four cases. Chinese expert consensus among emergency physicians agrees: once applied pre-hospitally, a tourniquet should not be removed unless an alternative method can fully stop bleeding. For arm bleeding, position the tourniquet on the upper third of the arm; for leg bleeding, place it near the groin. Avoid applying it to forearms, calves, elbows, or knees. Experts recommend keeping tourniquet application time under two hours total before reaching medical care; however, if reaching a facility proves impossible and no other method works, leave it on until professional help arrives. Improvised tourniquets made from belts, ties, or sleeves alone rarely suffice; they must be twisted tightly using a stick or similar tool to be effective.