Shock

At the same time that one is ensuring an adequate ventilation, efforts should be directed toward rapidly restoring a more than adequate tissue perfusion. After hemorrhagic shock, the cardiac output and oxygen delivery must be 25 to 50 percent greater than normal to adequately perfuse and oxygenate the intestinal mucosa and liver.3

Other preliminary studies indicate that capnometry to determine the end-tidal P co2 (PETco2), particularly if combined with arterial Pco2 determinations so that one can determine the arterial-end tidal CO2 difference [P (a - ET)co2] can also help monitor the adequacy of tissue perfusion ventilation. In general, a persistent PET co2 < 28 mmHg or P (a - ET)co2 > 10 mmHg is an indication of a poor prognosis.

If hypovolemic hypotension is present in patients with blunt chest trauma, it is most likely due to pelvic or extremity fractures, intraabdominal injuries, and/or intrathoracic bleeding.

In patients with penetrating chest trauma, the cause of shock will be intrathoracic injury in about three-quarters. The most frequent sources of intrathoracic bleeding are lung, heart, great vessels, and intercostal or internal mammary arteries. Up to one-half may have extrathoracic injuries contributing to the shock. When this occurs, it is most likely due to intraabdominal bleeding which often has a delayed diagnosis.

TREATMENT Fluids Failure to correct hypotension within 15 to 30 min greatly increases the mortality rate. In previously healthy patients requiring massive transfusions but having hypotension for less than 30 min, the mortality rate has averaged about 10 percent. However, if the hypotension is present for more than 30 min, the mortality rises to almost 50 percent. If the patient has preexisting disease or is over 65 years of age, the mortality with massive transfusions plus prolonged hypotension exceeds 90 percent.

To provide fluids rapidly in hypotensive patients, one usually needs at least two large intravenous catheters. If peripheral veins are not readily available, one may be forced to cannulate the subclavian or internal jugular veins. If a subclavian vein line is required, it should be inserted on the side of the injury. If one side of a chest is injured and the other lung is collapsed during insertion of a central intravenous line, impaired function of both lungs could be rapidly fatal.

Peripheral veins may be collapsed, unavailable, or inadequate. Especially in patients with thoracic trauma (and because of the activity required at the chest to deal with the direct consequence of that trauma) femoral venous cannulation is a preferred route of access for infusion of fluids. Seldinger technique is usually used (that is, "catheter over a guidewire") to insert a short, fat cannula, such as an "introducer" of the kind otherwise used in conjunction with pulmonary artery catheters. If percutaneous access to the femoral veins is difficult—as it often is when the patient has "bled out"—an experienced operator can place a cannula in the femoral vein via a saphenous vein cutdown in less than a minute. Such saphenous cutdowns are rare but can be lifesaving.

Irrespective of the route used to obtain vascular access, the goal is to stabilize the intravascular volume long enough to definitively manage the bleeding and only then to fully resuscitate the patient. Rapid resuscitation prior to control of the source can increase the rate and volume of blood loss, worsening hypothermia, immune suppression, and even mortality. Stopping the bleeding is the penultimate priority.

Chest Tube and Thoracotomy A large hemothorax or pneumothorax can seriously interfere with ventilation and venous return; consequently, it should be evacuated as rapidly as possible. If blood is being removed rapidly through the chest tube, the vital signs should be followed very closely. If the vital signs are improving, one can continue to evacuate the blood. However, if the vital signs deteriorate as the blood is being evacuated, in spite of the rapid infusion of intravenous fluids, the patient may be exsanguinating via the chest tube because the tamponading effect of the hemothorax has been removed. In such circumstances, the chest tube should be clamped and the patient taken directly to the operating room for an emergency thoracotomy.

If it is thought that the bleeding is from an internal mammary or intercostal artery, one can insert a 30-mL balloon Foley catheter into the chest at the injured site, inflate the balloon, and pull it back tightly against the inside of the chest wall. The Foley catheter can also be used to drain blood or air from the pleural cavity, and if adequate pressure is applied with the inflated balloon against the chest wall for 12 to 24 h by taping the stretched tube to the chest wall, the bleeding will usually remain controlled.

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