Internal bleeding

Internal bleeding also called internal hemorrhage, is a loss of blood from a blood vessel inside the body that is not usually or easily seen from the outside. Internal bleeding is a medical emergency and should be treated immediately by medical professionals. Heavy internal bleeding may occur in the abdominal cavity, chest cavity, digestive tract, or tissues surrounding large bones, such as the thighbone (femur) and pelvis, that are broken. Internal bleeding is a serious medical emergency but the extent of severity depends on bleeding rate and location of the bleeding (e.g. head, torso, extremities). Severe internal bleeding into the chest, abdomen, retroperitoneal space, pelvis, and thighs can cause hemorrhagic shock or death if proper medical treatment is not received quickly ¹.

In a healthy adult, there is an average of 4.5-5.5 liters or 70-90 ml/kg of blood circulating at any given time ². Most adults can tolerate losing up to 14% of their blood volume without physical symptoms or deviations in their vital signs. The severity of hemorrhage divides into a class system organized by percent of blood volume loss. Up to 15% of blood volume loss classifies as a Class 1 hemorrhage. The patient is generally asymptomatic, and vital signs are within normal limits. Class 2 hemorrhage is a loss of 15 to 30% of total blood volume. Common manifestations include complaints of nausea and fatigue. On physical exam, there will be pallor and cooling of the extremities. Vital signs will start to deviate from normal, tachycardia being the first vital sign to increase (100 to 120 beats per minute), which is followed by an increased respiratory rate (20-24 breaths per minute). Class 3 hemorrhage is 30 to 40% of total blood volume loss. Common manifestations include delayed capillary refill (greater than two seconds) and changes in mental status. Drastic blood pressure deviations (less than 90 mmHg) are generally not seen until 30% of the blood volume is lost. Vital signs may reflect a systolic less than 90 mmHg or 20 to 30% of original measurement; heart rate is greater than 120, changes in mental status, and narrow pulse pressure (less than 25 mmHg). These changes represent the body attempting to maintain perfusion to the vital organs by constricting peripheral blood vessels. Class 4 hemorrhage is defined as greater than 40% of total blood volume loss. There is commonly a lack of urine output, absent peripheral pulses, and further deviations in vital signs. Severe hemorrhaging can lead to shock, which occurs when the blood loss becomes significant enough that it is unable to meet the oxygen demands of the tissue. Cellular aerobic metabolism shuts down, and anaerobic metabolism begins, leading to the production of lactic acid and ultimately a metabolic acidosis ³. The risk is very high for organ failure, coma, and death absent the timely implementation of life-saving interventions.

Initially, internal bleeding may cause no symptoms, although an injured organ that is bleeding may be painful. However, the person may be distracted from this pain by other injuries or may be unable to express pain because of confusion, drowsiness, or unconsciousness. Eventually, internal bleeding usually becomes apparent. For example, blood in the digestive tract may cause vomiting of blood or passage of bloody or black stool.

Extensive blood loss causes low blood pressure, making the person feel weak and light-headed. The person may faint when standing or even sitting and, if blood pressure is very low, lose consciousness. If extensive bleeding causes light-headedness or symptoms of shock, the person should be laid down and the legs elevated. Medical assistance should be summoned as quickly as possible.

Doctors will use one of these treatments to stop the bleeding as quickly as possible:

• For bleeding at or near the skin:
  • Surgery
  • Apply pressure on the wound
• For internal bleeding or bleeding deep inside the body:
  • Surgery
  • Minimally Invasive, image-guided procedure called an embolization. Embolization works by plugging up the bleeding blood vessel with special materials. Embolizations are performed through a pinhole by specialized doctors called interventional radiologists. Your loved one’s doctors will decide whether surgery or an embolization is the better option.

Bleeding from a vein often stops on its own or by putting pressure on the wound. It is less common for accident victims to need surgery or embolization for bleeding veins.

Internal bleeding things to remember

• Always call your local emergency number.
• First aid for severe external bleeding includes direct pressure on the wound maintained by using pads and bandages, and raising the injured area above the level of the heart if possible.
• First aid for internal bleeding includes laying the person down, raising their legs above the level of their heart and not giving them anything to eat or drink.

Internal bleeding causes

Bleeding is the loss of blood from the circulatory system. The cause of internal bleeding is diverse and varies by lifestyle and socioeconomic background, causes can range from disease processes to trauma or injuries to the body. In 2000, the World Health Organization estimated that injury was responsible for 9% of the global mortality, and worldwide, it comprised 12% of the disease burden ⁴. Approximately 90% of injuries occur in low and middle-income nations. Of the myriad ways people are injured, most can be categorized as blunt or penetrating. Blunt injury involves a forceful impact (e.g., blow, kick, strike with an object, fall, motor vehicle crash, blast). Penetrating injury involves breach of the skin by an object (e.g., knife, broken glass) or projectile (e.g., bullet, shrapnel from an explosion). Traffic accidents and violence contribute to high rates of fatal hemorrhages ⁵. Injury is the number one cause of death for people aged 1 to 44. In the US, there were 231,991 trauma deaths in 2016, about 70% being accidental. Of intentional injury deaths, more than 70% were due to self-harm. In addition to deaths, injury results in about 39 million emergency department visits and 2.8 million hospital admissions annually. In America up to age 46, bleeding secondary to trauma is the leading cause of death ⁶.

Trauma

The most common cause of death in trauma is bleeding ⁷. Death from trauma accounts for 1.5 million of the 1.9 million deaths per year due to bleeding ⁸.

There are two types of trauma: penetrating trauma and blunt trauma ¹.

• Penetrating trauma is the most common cause of vascular injury and can result in internal bleeding. It can occur after a ballistic injury or stab wound. If penetrating trauma occurs in blood vessels close to the heart, it can quickly lead to hemorrhagic or hypovolemic shock , exsanguination, and death ¹.
• Blunt trauma is another cause of vascular injury that can result in internal bleeding. It can occur after a high speed deceleration in an automobile accident ⁹.

Non-traumatic

A number of pathological conditions and diseases can lead to internal bleeding. These include:

• Blood vessel rupture as a result of high blood pressure, aneurysms, esophageal varices, peptic ulcers, or ectopic pregnancy ¹⁰.
• Other diseases linked to internal bleeding include cancer, hematologic disease, Vitamin K deficiency, and rare viral hemorrhagic fevers, such as the Ebola, Dengue or Marburg viruses ¹¹.

Other

Internal bleeding could be caused by medical error as a result of complications after surgical operations or medical treatment. Some medication effects may also lead to internal bleeding, such as the use of anticoagulant drugs or antiplatelet drugs in the treatment of coronary artery disease ¹².

Signs and symptoms of internal bleeding

It is important to remember that an injured person may be bleeding internally even if you can’t see any blood. An internal injury can sometimes cause bleeding that remains contained within the body; for example, within the skull or abdominal cavity.

Listen carefully to what the person tells you about their injury – where they felt the impact, for example. They may display the signs and symptoms of shock. In the case of a head injury, they may display the signs and symptoms of concussion. Therefore, it is important to ask the right questions to collect the relevant information.

Signs and symptoms of internal bleeding depend on where the bleeding is inside the body, but may include:

• Pale, cool, clammy and sweaty skin
• Discoloration of the skin in the injured area
• Lightheadedness
• Fainting
• Anxiety or restlessness
• Rapid breathing, difficulty breathing or breathlessness
• Rapid weak pulse
• Nausea or vomiting
• Deteriorating conscious state or unconsciousness
• Pain at the injured site
• Swollen, tight abdomen
• Extreme thirst
• Chest pain
• Abdominal pain

Symptoms of shock

If your bleeding starts abruptly and progresses rapidly, you could go into shock. Signs and symptoms of shock include:

• Drop in blood pressure
• Not urinating or urinating infrequently, in small amounts
• Rapid pulse
• Unconsciousness

Some signs and symptoms specific to concussion (caused by trauma to the head) include:

• headache or dizziness
• loss of memory, particularly of the event
• confusion
• altered state of consciousness
• wounds on the head (face and scalp)
• nausea and vomiting.

Internal bleeding – visible:

The most common type of visible internal bleed is a bruise, when blood from damaged blood vessels leaks into the surrounding skin. Some types of internal injury can cause visible bleeding from an orifice (body opening). For example:

• Bowel injury – bleeding from the anus
• Stomach injury – vomiting blood, which might be red or might be dark brown and resemble coffee grounds in texture. Black, tarry stool.
• Head injury – bleeding from the ears, nose or mouth
• Lung injury – coughing up frothy, bloodied sputum (spit)
• Urinary tract injury – blood in the urine.

Internal bleeding in brain

Bleeding within the brain occurs when a blood vessel is ruptured and bleeds into or around the brain. The signs and symptoms will correlate with the location. The term for any bleeding occurring within the skull is an intracranial hemorrhage; this commonly occurs as a result of chronically elevated blood pressure leading to a weakening of the arterial walls ¹³. Symptoms vary ranging from unilateral weakness to headache, nausea, vomiting, and altered mental status. Other causes of intracranial hemorrhage include heavy alcohol use, long term tobacco use, old age, and drug abuse ¹⁴. Trauma is another major contributor to intracranial bleeding. Another type of intracranial bleeding is a subarachnoid hemorrhage (SAH). This type of bleeding occurs due to the rupture of a bridging cortical vein causing blood to accumulate between the delicate arachnoid matter and pia tissue, causing direct irritation to the meninges lining the brain and can result in severe pain. The classic scenario is a patient presenting with the sudden onset of the “worst headache of their life,” otherwise known as a “thunderclap headache.” Ruptured aneurysms account for most cases of subarachnoid hemorrhage, but other causes include a traumatic head injury or arteriovenous malformations ¹⁵. Additional types of intracranial bleeding include intraparenchymal hemorrhage, subdural hematoma, and epidural hematoma. Patients may present with more than one type of intracranial bleed, especially after trauma.

Internal bleeding in chest

Bleeding in the pleural cavity of the chest is called hemothorax. Blood enters a small space between the visceral and parietal pleura, causing the buildup of blood to interfere with the normal lung expansion, ultimately affecting the transfer of oxygen and carbon dioxide between alveoli and blood. This type of breed commonly presents in traumatic injuries, metastatic cancer, blood clotting disorders, or rarely spontaneously. Symptoms include dizziness, shortness of breath, and chest pain. If bleeding continues unabated, this can result in shock or even death. If the pressure builds within the chest and affects the cardiac return of blood, this is known as a tension hemothorax, and this too can result in death if not treated promptly.

Internal bleeding in abdomen

Traumatic blood loss in the abdomen requires a high degree of clinical suspicion. If present, symptoms can be nonspecific and usually require imaging for diagnosis. Symptoms include abdominal pain, hematemesis, hematuria, melena, and bruising, amongst others. More severe bleeding can result in hemorrhagic shock and even death. Common sources of hemorrhage include organ damage (hepatic, splenic, renal, adrenal), vascular injury, gynecologic/obstetric procedure complications, or coagulopathies. Ectopic pregnancy and cyst rupture are two common causes of an abdominal hemorrhage in a woman of childbearing age ¹⁶.

The retroperitoneum contains visceral and vascular structures and is susceptible to injury in abdominal or pelvic injuries. The types of hematomas that develop divide into anatomic zones. Zone 1 is in a central location and damage here includes pancreaticoduodenal injuries or major blood vessels such as the renal artery or aorta. Zone 2 involves the flanks and peri-nephric regions, including the colon. Zone 3 is the pelvic zone. An injury here is common with a pelvic fracture or femoral vascular access injuries ¹⁷. Signs and symptoms include abdominal pain, back pain, flank pain, urinary symptoms if compressing the bladder, and femoral nerve palsy. Unique physical exam findings related to the retroperitoneum include Grey Turner sign (bruising on the flanks).

Bone fractures can lead to dangerously fast life-threatening hemorrhaging. The center of the long bones contains the bone marrow where the red blood cells are made and contain many arteries. The most vascular bones include the long bones: humerus, radius, ulna, femur, fibula, pelvis, and vertebrae ¹⁸. For example, the thigh can hold up to 1 to 2 liters of blood. Trauma to blood vessels outside of the bone, but coursing with it anatomically, can also result in significant hemorrhage if they are injured. Hemorrhage can occur as a result of either a traumatic injury or during surgical repair.

Internal bleeding diagnosis

Recognizing the degree of blood loss via vital sign and mental status abnormalities is important. The American College of Surgeons Advanced Trauma Life Support (ATLS) hemorrhagic shock classification links the amount of blood loss to expected physiologic responses in a healthy 70 kg patient. As total circulating blood volume accounts for approximately 7% of total body weight, this equals approximately five liters in the average 70 kg male patient.

• Class 1: Volume loss up to 15% of total blood volume, approximately 750 mL. Heart rate is minimally elevated or normal. Typically, there is no change in blood pressure, pulse pressure, or respiratory rate.
• Class 2: Volume loss from 15% to 30% of total blood volume, from 750 mL to 1500 mL. Heart rate and respiratory rate become elevated (100 BPM to 120 BPM, 20 RR to 24 RR). Pulse pressure begins to narrow, but systolic blood pressure may be unchanged to slightly decreased.
• Class 3: Volume loss from 30% to 40% of total blood volume, from 1500 mL to 2000 mL. A significant drop in blood pressure and changes in mental status occur. Heart rate and respiratory rate are significantly elevated (more than 120 BPM). Urine output declines. Capillary refill is delayed.
• Class 4: Volume loss over 40% of total blood volume. Hypotension with narrow pulse pressure (less than 25 mmHg). Tachycardia becomes more pronounced (more than 120 BPM), and mental status becomes increasingly altered. Urine output is minimal or absent. Capillary refill is delayed.

Again, the above is outlined for a healthy 70 kg individual. Clinical factors must be taken into account when assessing patients. For example, elderly patients taking beta blockers can alter the patient’s physiologic response to decreased blood volume by inhibiting mechanism to increase heart rate. As another, patients with baseline hypertension may be functionally hypotensive with a systolic blood pressure of 110 mmHg.

Evaluation

The first step in managing hemorrhagic shock is recognition. Ideally, This should occur before the development of hypotension. Close attention should be paid to physiological responses to low-blood volume. Tachycardia, tachypnea, and narrowing pulse pressure may be the initial signs. Cool extremities and delayed capillary refill are signs of peripheral vasoconstriction ¹⁹.

In the setting of trauma, an algorithmic approach via the primary and secondary surveys is suggested by Advanced Trauma Life Support. Physical exam and radiological evaluations can help localize sources of bleeding. A trauma ultrasound, or Focused Assessment with Sonography for Trauma (FAST), has been incorporated in many circumstances into the initial surveys. The specificity of a FAST scan has been reported above 99%, but a negative ultrasound does not rule out intra-abdominal pathology.

Especially in the setting of shock secondary to abdominal bleeding, the use of a CT scan, and the focused assessment with sonography for trauma (FAST Scan) are indicated ²⁰. A Focused Assessment with Sonography for Trauma (FAST) is a highly reliable noninvasive diagnostic test available at the bedside. For example, it can be used to assess for an abdominal aortic aneurysm in a patient with concerning symptoms ²¹. Indications for surgical intervention in those with suspected abdominal bleeding include peritoneal signs, clinical deterioration, hemodynamic instability, and a positive FAST exam. Patients with hemodynamic stability should undergo less invasive methods of imaging before surgical intervention as indicated. Retroperitoneal bleeds can undergo an evaluation with a CT scan and ultrasound ¹⁷.

Evaluation of bleeding from an anatomic orifice often relies on endoscopy of the area of concern, which may include, but not limited to, bronchoscopy, cystoscopy, colonoscopy, or esophagogastroduodenoscopy (EGD).

For a bleed in the skull, a prompt non-contrast CT scan is necessary within six hours of onset for the best outcomes ²². MRI is considered to be more sensitive as time passes the six-hour threshold ²³. A lumbar puncture is another useful diagnostic test as it can reveal the presence of red blood cells in the CSF, or xanthochromia indicating hemorrhage.

For bleeding in the chest, diagnosis is aided using a chest X-ray, ultrasound, or CT scan depending on the available resources (and the patient’s clinical stability). Hemodynamically unstable patients should not be moved to a diagnostic area for evaluation. Bedside procedures such as chest X-ray and/or ultrasound can help make a diagnosis of a significant hemothorax without moving the patient to a more uncontrolled area such as is often required for advanced imaging like CT scan. A fluid analysis will definitively diagnose the presence of blood from other forms of fluid. Treatment includes placement of a chest tube for drainage and possible surgical exploration if there is greater than 1500 mL output initially or greater than 200 mL per hour after initial placement.

Internal bleeding treatment

Internal bleeding is a medical emergency. There is little a first aider can do for internal bleeding other than seek medical attention. Whilst waiting for the ambulance to arrive, follow the general guidelines:

• Check for danger before approaching the person.
• If possible, send someone else to your local emergency number for an ambulance.
• Prevent further injury
• Check that the person is conscious.
• Help the casualty into the most comfortable position. Lie the person down.
• Maintain normal body temperature. Cover them with a blanket or something to keep them warm.
• Offer reassurance. Manage any other injuries, if possible.
• Monitor the ABC (airway, breathing and circulation).
• If possible, raise the person’s legs above the level of their heart.
• Don’t give the person anything to eat or drink.
• If the person becomes unconscious, place them on their side. Check breathing frequently. Begin cardiopulmonary resuscitation (CPR) if necessary.

Spread of disease through bleeding

Some diseases can be spread through open wounds. Remember:

• If possible, wash your hands with soap and water before and especially after administering first aid. Dry your hands thoroughly before putting on gloves.
• First aid kits contain gloves. Always put on gloves beforehand if available. If not, improvise.
• Do not cough or sneeze over the wound.

The management of hemorrhage will vary based on anatomic location, the extent of the injury, patient presentation, and the resources available. Resuscitation with IV fluids is necessary if the patient is demonstrating signs of hypovolemia. Basic fluid resuscitation is by placing two large bore IVs, infusing normal saline or lactated ringer and beginning transfusion protocol. Blood product administration should be in equivalent amounts (1:1:1 packed red blood cells, fresh frozen plasma, platelets) and transfused as needed. Patients receiving transfusions should have monitoring for hypothermia. The goals of treatment are to restore intravascular volume and to maintain oxygen delivery until the source of bleeding can be resolved. Target mean arterial pressure (MAP) is a pressure greater than 65mmHg. For penetrating trauma, a systolic blood pressure goal is greater than 90mmHg. For brain injuries, the goal mean arterial pressure is 105 mmHg or higher, and systolic blood pressure greater than 120 mmHg ²⁴. It is also essential to monitor lactic acid production, and worsening metabolic acidosis as this can lead to loss of peripheral vasoconstriction and cardiovascular collapse. For traumatic external wounds, direct pressure and placement of tourniquets proximal to the source of the hemorrhage can be life-saving interventions.

Hypotensive resuscitation has been suggested for the hemorrhagic shock patient without head trauma. The aim is to achieve a systolic blood pressure of 90 mmHg in order maintain tissue perfusion without inducing re-bleeding from recently clotted vessels. Permissive hypotension is a means of restricting fluid administration until hemorrhage is controlled while accepting a short period of suboptimal end-organ perfusion. Studies regarding permissive hypotension have yielded conflicting results and must take into account type of injury (penetrating versus blunt), the likelihood of intracranial injury, the severity of the injury, as well as proximity to a trauma center and definitive hemorrhage control ²⁵.

The quantity, type of fluids to be used, and endpoints of resuscitation remain topics of much study and debate ²⁵. For crystalloid resuscitation, normal saline and lactated ringers are the most commonly used fluids. Normal saline has the drawback of causing a non-anion gap hyperchloremic metabolic acidosis due to the high chloride content, while lactated ringers can cause a metabolic alkalosis as lactate metabolism regenerates into bicarbonate.

Recent trends in damage control resuscitation focus on “hemostatic resuscitation” which pushes for early use of blood products rather than an abundance of crystalloids in order to minimalize the metabolic derangement, resuscitation-induced coagulopathy, and the hemodilution that occurs with crystalloid resuscitation. The end goal of resuscitation and the ratios of blood products remain at the center of much study and debate. A recent study has shown no significant difference in mortality at 24 hours or 30 days between ratios of 1:1:1 and 1:1:2 of plasma to platelets to packed red blood cells. However, patients that received the more balanced ratio of 1:1:1 were less likely to die as a result of exsanguination in 24 hours and were more likely to achieve hemostasis Additionally, reduction in time to first plasma transfusion has shown a significant reduction in mortality in damage control resuscitation.

In addition to blood products, products that prevent the breakdown of fibrin in clots, or antifibrinolytics, have been studied for their utility in the treatment of hemorrhagic shock in the trauma patient. Several antifibrinolytics have been shown to be safe and effective in elective surgery. The CRASH-2 study was a randomized control trial of tranexamic acid versus placebo in trauma has been shown to decrease overall mortality when given in the first eight hours of injury. Follow-up analysis shows additional benefit to tranexamic acid when given in the first three hours after surgery ²⁵.

Damage control resuscitation is to occur in conjunction with prompt intervention to control the source of bleeding. Strategies may differ depending on proximity to definitive treatment.

References

1. Fritz, Davis (2011). “Vascular Emergencies”. Current Diagnosis & Treatment: Emergency Medicine (7e ed.). New York: McGraw-Hill. ISBN 978-0071701075
2. Johnson AB, Burns B. Hemorrhage. [Updated 2019 Nov 22]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2019 Jan-. Available from: https://www.ncbi.nlm.nih.gov/books/NBK542273
3. Foucher CD, Tubben RE. StatPearls [Internet]. StatPearls Publishing; Treasure Island (FL): Feb 22, 2019. Lactic Acidosis.
4. Kauvar DS, Lefering R, Wade CE. Impact of hemorrhage on trauma outcome: an overview of epidemiology, clinical presentations, and therapeutic considerations. J Trauma. 2006 Jun;60(6 Suppl):S3-11.
5. Carmichael H, Steward L, Peltz ED, Wright FL, Velopulos CG. Preventable death and interpersonal violence in the United States: Who can be saved? J Trauma Acute Care Surg. 2019 Jul;87(1):200-204.
6. Matano F, Fujiki Y, Mizunari T, Koketsu K, Tamaki T, Murai Y, Yokota H, Morita A. Serum Glucose and Potassium Ratio as Risk Factors for Cerebral Vasospasm after Aneurysmal Subarachnoid Hemorrhage. J Stroke Cerebrovasc Dis. 2019 Jul;28(7):1951-1957.
7. Teixeira, Pedro G. R.; Inaba, Kenji; Hadjizacharia, Pantelis; Brown, Carlos; Salim, Ali; Rhee, Peter; Browder, Timothy; Noguchi, Thomas T.; Demetriades, Demetrios (December 2007). “Preventable or Potentially Preventable Mortality at a Mature Trauma Center”. The Journal of Trauma: Injury, Infection, and Critical Care. 63 (6): 1338–46, discussion 1346–7. doi:10.1097/TA.0b013e31815078ae
8. Cannon, Jeremy (January 25, 2018). “Hemorrhagic Shock”. The New England Journal of Medicine. 378 (4): 370–379. doi:10.1056/NEJMra1705649
9. Duncan, Nicholas S.; Moran, Chris (2010). “(i) Initial resuscitation of the trauma victim”. Orthopaedics and Trauma. 24: 1–8. doi:10.1016/j.mporth.2009.12.003
10. Lee, Edward W.; Laberge, Jeanne M. (2004). “Differential Diagnosis of Gastrointestinal Bleeding”. Techniques in Vascular and Interventional Radiology. 7 (3): 112–122. doi:10.1053/j.tvir.2004.12.001
11. Bray, M. (2009). “Hemorrhagic Fever Viruses”. Encyclopedia of Microbiology. pp. 339–353. doi:10.1016/B978-012373944-5.00303-5 ISBN 9780123739445
12. Pospíšil, Jan; Hromádka, Milan; Bernat, Ivo; Rokyta, Richard (2013). “STEMI – the importance of balance between antithrombotic treatment and bleeding risk”. Cor et Vasa. 55 (2): e135–e146. doi:10.1016/j.crvasa.2013.02.004
13. Lee SU, Kim T, Kwon OK, Bang JS, Ban SP, Byoun HS, Oh CW. Trends in the Incidence and Treatment of Cerebrovascular Diseases in Korea : Part I. Intracranial Aneurysm, Intracerebral Hemorrhage, and Arteriovenous Malformation. J Korean Neurosurg Soc. 2019 May 08
14. Gross BA, Jankowitz BT, Friedlander RM. Cerebral Intraparenchymal Hemorrhage: A Review. JAMA. 2019 Apr 02;321(13):1295-1303.
15. Agarwal S, Zhou T, Frontera J. Journal Club: Association between aspirin dose and subarachnoid hemorrhage from saccular aneurysms: A case-control study. Neurology. 2019 May 07;92(19):920-922.
16. Pontius E, Vieth JT. Complications in Early Pregnancy. Emerg. Med. Clin. North Am. 2019 May;37(2):219-237.
17. Baekgaard JS, Eskesen TG, Lee JM, Yeh DD, Kaafarani HMA, Fagenholz PJ, Avery L, Saillant N, King DR, Velmahos GC. Spontaneous Retroperitoneal and Rectus Sheath Hemorrhage-Management, Risk Factors and Outcomes. World J Surg. 2019 Aug;43(8):1890-1897.
18. Lazarev A, Golokhvast K, Borozda I. Review of the Problems of Diagnosis of Endopelvic Haemorrhage, Its Intensity, Volume, and Duration, and Treatment Methods of Circulatory Injuries and Surgical Hemostasis after Pelvic Fractures. Emerg Med Int. 2019;2019:2514146
19. Erdman MO, Chardavoyne P, Olympia RP. School Nurses on the Front Lines of Medicine: The Approach to a Student With Severe Traumatic Bleeding. NASN Sch Nurse. 2019 Sep;34(5):280-286.
20. Aboudara M, Maldonado F. Update in the Management of Pleural Effusions. Med. Clin. North Am. 2019 May;103(3):475-485.
21. Rubano E, Mehta N, Caputo W, Paladino L, Sinert R. Systematic review: emergency department bedside ultrasonography for diagnosing suspected abdominal aortic aneurysm. Acad Emerg Med. 2013 Feb;20(2):128-38.
22. Mackenzie MJ, Hiranandani R, Wang D, Fung T, Lang E. Determinants of Computed Tomography Head Scan Ordering for Patients with Low-Risk Headache in the Emergency Department. Cureus. 2017 Oct 09;9(10):e1760.
23. Kim du S, Kong MH, Jang SY, Kim JH, Kang DS, Song KY. The usefulness of brain magnetic resonance imaging with mild head injury and the negative findings of brain computed tomography. J Korean Neurosurg Soc. 2013 Aug;54(2):100-6.
24. Vulliamy P, Thaventhiran AJ, Davenport RA. What’s new for trauma haemorrhage management? Br J Hosp Med (Lond). 2019 May 02;80(5):268-273.
25. Hooper N, Armstrong TJ. Hemorrhagic Shock. [Updated 2019 May 6]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2019 Jan-. Available from: https://www.ncbi.nlm.nih.gov/books/NBK470382