Delayed resuscitation The traditional viewpoints showed that fluid resuscitation and vasoactive drugs should be given immediately to rapidly increase the blood pressure to normal level after shock. But recent studies showed that for severe traumatic shock, especially for uncontrolled hemorrhage shock, early use of vasoactive drugs or large amounts of fluid to rapidly raise the blood pressure before completely controlling bleeding did not improve the survival rate of the patients. In contrary, it has big risk to increase the mortality and complication [17]. Based on the results of laboratory and clinical research, the new concept of “delayed resuscitation” is suggested for severe traumatic shock, especially for uncontrolled hemorrhagic shock. This concept advocated a small amount of balanced salt solution was given to this kind of patients to meet the basic need of body before operation, but not giving a large amount of fluid resuscitation. A very famous observation is from Bickell et al. They compared the effects of immediate versus delayed fluid resuscitation on severe trauma with 598 penetrating torso injured patients. The results showed that patients in delayed resuscitation group had better organ function, lower renal, respiratory, and infection complications and lower mortality than immediate resuscitation group [18]. Schreiber et al. investigated the effects of controlled resuscitation and standard resuscitation on trauma patients in out-of-hospital settings in nineteen emergency medical services (EMS) systems in the Resuscitation Outcome Consortium. Eligible patients had an out-of-hospital systolic blood pressure (SBP) of 90 mm Hg or lower. Patients in controlled resuscitation group received 250 mL of fluid if they did not have radial pulse or an SBP lower than 70 mm Hg and another 250-mL boluses to maintain a radial pulse or an SBP of 70 mm Hg or greater. Patients in standard resuscitation group received 2 L initially and additional fluid to maintain an SBP of 110 mm Hg or greater if needed. The crystalloid protocol was maintained until hemorrhage control or 2 h after hospital arrival. The results found that 24 h after admission, there were 5 deaths (5 %) in the controlled resuscitation group and 14 (15 %) in the standard resuscitation group. Among patients with blunt trauma, 24-h mortality was 3 % in controlled resuscitation group and 18 % in standard resuscitation group. These results suggest that controlled resuscitation in out-of-hospital and hospital settings is proper and may offer an early survival advantage in blunt trauma [19]. Nevertheless, what type of and how much fluid are needed for different trauma patients during pre-hospital period needs further investigation. Large-scale, Phase III clinical trials to investigate the effects on survival and other clinical outcomes are needed.

Hypothermic resuscitation Hypothermic resuscitation has always been a controversial issue. Long-time profound hypothermia may influence the metabolism, coagulation and cardiovascular functions [20]. But in recent years, more and more studies suggested that, for severe traumatic hemorrhagic shock , short-term and mild hypothermia during the period from injury to operation may enhance the hypotensive resuscitation effects. Safer resuscitation center of America found that mild or moderate hypothermia (32–28 °C) implemented before bleeding control from injury could significantly increase the animal survival and vital organ function [21]. Our studies found that 1 h, 34 °C mild hypothermia significantly enhanced the resuscitation effect of hypothensive resuscitation, which include decreasing the cellular metabolism rate, reducing the oxygen demand, and extending the golden save time [22] (Figs. 2 and 3). Recently, Gu et al. [23] found pharmacologically induced hypothermia attenuates the traumatic brain injury in neonatal rats. These studies showed that hypothermic resuscitation has beneficial effect for traumatic shock before hemorrhage controlled. But how to implement hypothermic resuscitation at early stage of shock needs further investigation. In addition, it’s worth pointing out that the controlled hypothermia at early stage of shock treatment is different from the spontaneous hypothermia in trauma patients. The former is beneficial for the trauma patients while the latter is harmful. Large amount of studies showed that severe hemorrhage, large amount of blood and fluid infusion after trauma would result in hypothermia, which severely interferes with the cellular metabolism and organ function [24].

Damage control resuscitation In patients with severe trauma, in addition to the limited fluid resuscitation , “damage control resuscitation” has also been put forward in recent years [4]. The damage control resuscitation is that, in the first 24–48 h treatments for the severe trauma patients, non-surgical treatment strategies are taken to prevent or reverse a series of hemorrhage induced damages, such as blood loss anemia, coagulopathy, hypothermia, acidosis (spontaneous), etc., which may improve the resuscitation effect. The specific measures include: application of permissive hypotensive resuscitation , prevention and treatments for hypothermia including passive and positive warming measures, the use of exogenous buffer to correct acidosis, direct application of 1:1:1 fresh frozen plasma, packed red blood cell and platelet. Recombinant factor VII was recommended early use, etc. [25, 26]. The damage control resuscitation has been widely used in early treatment of severe trauma and shock, but some specific proposals and measures, especially for the treatment of coagulation function, still need further investigation to improve the efficacy [27, 28].

Adaptive hypotensive resuscitation The common view point of fluid resuscitation for traumatic sock is rapidly recovering the blood pressure via enough fluid resuscitation after surgical bleeding control. While the fact is that immediately implementing enough fluid infusion after surgical bleeding control would cause tissue edema and damage organ function. Our research team found that immediately recovering the blood pressure to normal level (MAP at 90 mmHg) for uncontrolled hemorrhagic shock rats after bleeding control further damaged the vital organ function, the main reason is the tissue edema and cellular function injury after immediately enough resuscitation. While transiently adaptive hypotensive resuscitation, maintaining MAP at 70 mmHg for 1 h enhanced the resuscitative effect of hypotensive resuscitation including significantly improved the tissue oxygen delivery and utilization, improved the vital organ function and animal survival [29] (Figs. 4 and 5).

The resuscitation end point of traumatic shock Restoration of blood volume, tissue perfusion and oxygen supply are the core issues of resuscitation for traumatic hemorrhagic shock. The traditional fluid resuscitation endpoints of traumatic hemorrhagic shock include blood pressure, heart rate and urine volume, etc. But these parameters cannot well reflect the tissue perfusion and oxygenation status, especially when the patients are in compensatory stage or after use of vasoconstrictor drugs. In recent years, many researchers have proposed many new resuscitation indices, including oxygen delivery (DO2), oxygen utilization (VO2), blood lactate, base deficit, and gastric mucosa pH value, etc. These indices provide reliable reference for ideal resuscitation and increase the success rate of resuscitation for trauma shock [30, 31].

DO2 and VO2 Studies have shown that tissue ischemia and hypoxia in patients with severe trauma and shock are not simply caused by insufficient blood supply, but are closely related to DO2 and VO2. Therefore, the recovery of shock in recent years, in addition to using blood pressure and cardiac index (CI) as resuscitation endpoints, some new endpoints have been put forward such as DO2 and VO2. Many animal and clinical studies have shown that traumatized animals and patients who obtained super normal value of DO2 and VO2 in resuscitation can get higher resuscitation success rate and higher survival than those who did not obtain the super normal value of DO2 and VO2 in resuscitation [32]. Common measures to increase DO2, VO2 include: (1) expand capacity and improve the effective circulating blood volume; (2) use positive inotropic drugs, such as dopamine and dobutamine; (3) use vasoconstrictors (epinephrine, norepinephrine, and phenylephrine) when dopamine is invalid; (4) improve the ventilation and maintain arterial blood oxygen saturation.