Hemorrhagic Shock Workup

Generally, laboratory values are not helpful in acute hemorrhage because values do not change from normal until redistribution of interstitial fluid into the blood plasma occurs after 8-12 hours. Many of the derangements that eventually occur are a result of replacing a large amount of autologous blood with resuscitation fluids.

Hemoglobin and hematocrit values remain unchanged from baseline immediately after acute blood loss. During the course of resuscitation, the hematocrit may fall secondary to crystalloid infusion and re-equilibration of extracellular fluid into the intravascular space.

No absolute threshold hematocrit or hemoglobin level that should prompt transfusion exists. A hemoglobin concentration of less than 7 g/dL in the acute setting in a patient that was otherwise healthy is concerning only because the value most likely will drop considerably after re-equilibration.

In the absence of preexisting disease, transfusions can be withheld until significant clinical symptoms are present or the rate of hemorrhage is enough to indicate ongoing need for transfusion.

Patients with significant heart disease are at higher risk of myocardial ischemia with anemia, and transfusion should be considered when values drop below 7 mg/dL.

Arterial blood gas may the most important laboratory value in the patient in severe shock.

Acidosis is the best indicator in early shock of ongoing oxygen imbalance at the tissue level. A blood gas with a pH of 7.30-7.35 is abnormal but tolerable in the acute setting. The mild acidosis helps unload oxygen at the peripheral tissues and does not interfere with hemodynamics.

A pH below 7.25 may begin to interfere with catecholamine action and cause hypotension unresponsive to inotropics. Although this is a time-honored concept, recent data do not find evidence of this phenomenon.

Metabolic acidosis is a sign of underlying lack of adequate oxygen delivery or consumption and should be treated with more aggressive resuscitation, not exogenous bicarbonate. Life-threatening acidemia (pH < 7.2) initially may be buffered by the administration of sodium bicarbonate to improve the pH. However, be aware that no survival benefit to this practice has been documented.

Coagulation studies generally produce normal results in the majority of patients with severe hemorrhage early in the course. The notable exceptions are patients who are on warfarin, low molecular weight heparin, or antiplatelet medications or those patients with severe preexisting hepatic insufficiency.

If patients are unable to provide adequate medication histories, tests for primary and secondary hemostasis should be ordered. The prothrombin time (PT) and the activated partial thromboplastin time (aPTT) will identify major problems with secondary hemostasis.

The best test for platelet function is the bleeding time. This test is difficult to perform in the patient with acute hemorrhage.

An alternative is thromboelastography, which is at least equivalent, and possibly superior, to the bleeding time. This test is an ex vivo analysis of all of the components of clotting and has been used extensively in orthotopic hepatic transplantation, cardiac surgery, and trauma.

Qualitative platelet dysfunction can be inferred in those patients with a clinical coagulopathy and normal PT and aPTT values. Obviously, abnormal PT or aPTT values should be corrected emergently in the context of severe hemorrhage.

Electrolyte studies usually are not helpful in the acute setting. After massive resuscitation, certain abnormalities can occur.

Sodium and chloride may increase significantly with administration of large amounts of isotonic sodium chloride. Hyperchloremia may cause a non–ion gap acidosis and significantly worsen an existing acidosis.

Calcium levels may fall with large-volume, rapid blood transfusions. This is secondary to chelation of the calcium by the ethylenediaminetetraacetic acid (EDTA) preservative in stored blood. Newer methods of blood banking avoid using EDTA, and the problem of hypocalcemia should be minimized.

Likewise, potassium levels may rise with large-volume blood transfusions.

Creatinine and blood urea nitrogen usually are within normal limits unless preexisting renal disease is present. Caution should be used when administering iodinated contrast in patients with elevated creatinine because the dye load could initiate a contrast-induced nephropathy in addition to chronic renal impairment.

A blood specimen for type and crossmatch should be obtained as soon as the patient arrives.

For patients who are actively bleeding, 4 U of packed red blood cells (PRBCs) should be prepared, along with 4 U of fresh frozen plasma (FFP). Platelets may be obtained as well, depending on the physician's estimation of the likelihood of the need for platelet transfusion (less commonly needed compared to FFP).

Imaging studies are aimed at identifying the source of bleeding. In many types of severe hemorrhage, therapeutic interventions, such as exploratory laparotomy, will preclude comprehensive diagnostic studies.

Chest radiographs

Chest radiographs indicate a diagnosis of hemothorax by showing a large opacity in one or both lung fields.

Hemothoraces large enough to cause shock usually are obvious as a complete whiteout of one pleural space.

Abdominal radiographs

Abdominal radiographs are rarely helpful. Hemoperitoneum usually will not be visible on plain film.

Occasionally, a radiograph will have a diffuse ground glass appearance, suggesting a large amount of intraperitoneal fluid, but this sign is not reliable.

Rarely, a ruptured abdominal aortic aneurysm can be diagnosed by noting an incomplete shell (calcified wall) of a dilated aorta.

Loss of the psoas shadow unilaterally also can suggest retroperitoneal blood.

CT scan

Computed tomography (CT) scan, as seen in the image below, is sensitive and specific for diagnosing intrathoracic, intra-abdominal, and retroperitoneal bleeding. It is the test of choice for diagnosing bleeding in these cavities.

CT scan only has an adjunctive role in the diagnosis of GI bleeding when other tests have suggested a mass lesion as part of the disease process.

Ultrasound is rapidly replacing CT scan as the diagnostic test of choice for the identification of hemorrhage in major body cavities. It is, of course, limited in its ability to evaluate the retroperitoneum. Retroperitoneal evaluation remains the purview of the CT scan.

Esophagogastroduodenoscopy

Esophagogastroduodenoscopy (EGD) is the test of choice for acute upper GI bleeding because it can provide a specific diagnosis and has therapeutic potential.

Lavage the stomach with a large gastric tube before the procedure to remove as much clot as possible.

Capabilities for epinephrine injection and bipolar circumactive probe (BICAP) cautery should be available.

Aortoenteric fistulas are very rare and usually are caused by erosion of an aortic aneurysm into the duodenum. EGD may be able to diagnose this problem, but the false-negative rate in these cases is very high.

Colonoscopy

Colonoscopy is used to diagnose acute lower GI bleeding.

It is considered by most to be difficult to perform in the acute setting and may fail to show the exact source of bleeding in cases of rapid hemorrhage.

Although some experience exists with therapeutic interventions, such as cauterization for acute arteriovenous malformation bleeding, these techniques are not used widely.

Ultrasound

Ultrasound is a useful technique to diagnose intraperitoneal bleeding in the trauma patient.

The focused abdominal sonographic technique (FAST) examination realistically has replaced diagnostic peritoneal lavage as the test of choice for identifying intraperitoneal fluid in the trauma patient.

The FAST examination includes 4 anatomical views of the pericardium, abdomen, and pelvis that attempt to identify free intra-abdominal fluid.

Bedside ultrasound can be performed by radiologists, surgeons, and emergency medicine physicians who have specialized training and certification.

Angiography

Angiography is extremely useful in the diagnosis of acute hemorrhage from many different sources. Its utility is limited by the availability of an angiographer on a timely basis.

In cases of lower GI bleeding, angiography is one of the best tests to localize a bleeding source. Angiography usually can detect bleeding that is at least 1-2 mL/min. Selective angiograms of the celiac, superior mesenteric, and inferior mesenteric arteries are performed to locate the areas of bleeding. The best time to perform the examination is when the patient is actively bleeding. Once the source is identified, embolotherapy may be used as an acute means of arresting hemorrhage. This will allow resuscitation to proceed prior to operation. If embolotherapy is not used, then identifying the site of bleeding will allow a more limited bowel resection to be performed if surgery becomes indicated during the admission.

Angiography can be used for diagnosis and management of severe bleeding from pelvic fractures. Although most bleeding from severe pelvic fractures is venous in origin, occasional significant arterial bleeding can be diagnosed and treated effectively with embolization.

Severe liver injuries pose a challenge to the trauma surgeon because of the large amounts of blood loss and the difficulty in gaining surgical control quickly. Many severe liver injuries now are being diagnosed and treated with angiographic embolization. Angiography is increasingly considered first-line intervention (before laparotomy) for severe liver injuries in centers that are equipped to perform rapid angiography and angiographic intervention. Similar methods may be used for other solid organ injuries, such as the spleen and kidney.

Angiography may be used in the diagnosis of massive hemoptysis of unclear etiology. Selective angiography of the bronchial arteries, combined with a selective pulmonary angiogram through a separate venous catheterization can localize bleeding.

The role of angiography in upper GI bleeding is more limited. Hemobilia is a rare cause of upper GI bleeding. If blood definitely is observed emanating from the ampulla of Vater, angiography should be performed to localize and control the source of bleeding.

Nuclear medicine scanning

Nuclear medicine scanning can be used to localize GI bleeding.

A tagged red blood cell scan may help differentiate upper from lower GI bleeding and may provide anatomic information, such as identifying bleeding from the right versus left colon. Overlap of structures will confound the utility and accuracy of this test.

The test requires a significant amount of time to complete, but it is very sensitive, detecting bleeding as slow as 0.5 mL/min.

Diagnostic peritoneal lavage is a bedside procedure that utilizes a small midline laparotomy and insertion of a catheter directly into the peritoneal cavity. Percutaneous insertion techniques are available but carry an increased risk of injury to underlying structures.

The intent of diagnostic peritoneal lavage is to determine if significant intra-abdominal bleeding or injuries to hollow organs are present.

If more than 5 mL of blood is aspirated, the test result is said to be grossly positive and laparotomy usually is indicated.

If blood is not aspirated, 1000 mL of warm lactated Ringer’s solution is infused into the abdomen and then allowed to drain out into the IV bag. The contents of the bag are examined in the lab. A red blood cell count of greater than 10,000 per µL is considered a microscopically positive test result.

Other conditions that make the test results positive include the following: white blood cell count greater than 500/µL; high levels of amylase, lipase, or bilirubin; and particulate matter that may be from an intraluminal source.

Central venous access

Central venous access is considered an adjunct to large-bore (16- or 14-gauge) peripheral IV lines.

Flow through a catheter is inversely proportional to the length and directly proportional to the diameter. Thus, long small-caliber lines, such as a standard triple lumen catheter, will deliver significantly less volume than a short large-caliber line, such as a peripheral IV.

Large-bore (12F) central resuscitation lines

This large-bore sheath introducer is used for volume resuscitation. Smaller sizes are less effective but are more effective than a standard multi-lumen central venous catheter.

If significant intra-abdominal bleeding from a venous injury is suspected, volume lines should be avoided in the femoral veins.

In general, access above and below the site of an injury is a good practice. This allows the operator to switch the primary resuscitation lines should one or more be ineffective or be positioned directly below an injury in the vessel in which the catheter resides.

Chest tube

The initial management of a hemothorax involves the insertion of a large-caliber chest tube for drainage, or open thoracotomy. In most patients with a hemothorax, tube thoracostomy alone is sufficient.

Surgical exploration with open thoracotomy is mandated in the presence of persistent bleeding; the presence of more than 1500 mL of blood in the initial chest tube drainage; or drainage of more than 200 mL/h for 2-4 hours.