Sepsis & Septic Shock

Pathophysiology
Sepsis is a potentially life-threatening complication of an infection that eventually leads to temporary or permanent organ dysfunction; septic shock is a drop in blood pressure caused by systemic inflammation and vasodilation. Sepsis and septic shock are at the far end of a continuum that often begins with a local wound or a MRSA infection, influenza that results in a pneumonia, a urinary tract infection that leads to a kidney infection, traveler’s diarrhea caused by some strains of E. coli, or from an intestinal infection that leads to a perforated bowel.
While the invading organisms can be bacteria, viruses, fungi, and parasites, the most common sepsis-causing pathogens are the bacteria Staphylococcus aureus (staph), Escherichia coli (E. coli), and some forms of Streptococcus.

SEPSIS PROGRESION
Local Infection > Systemic Infection > Sepsis > Severe Sepsis > Septic Shock > Death

The progression from a local infection to septic shock typically requires weeks, and once diagnosed, the mortality rate is 25-50% during the following month. While the immune system in healthy adults is typically capable of dealing with the index infection, the immune system of infants, immunocompromised persons, and persons 65 years old and older, may not be.

In a wilderness environment where minor wounds are, unfortunately, all to common, thorough wound cleaning and subsequent monitoring are important. Local inflammation—mild pain and tenderness, redness, and warmth—are normal but should not extend more than a millimeter or two beyond the site. Increased inflammation and pus at the site after 24 hours indicate a local infection; red streaks and fever indicate a systemic infection.

MRSA thrives in crowded, unsanitary conditions and outbreaks have occurred in children’s camps and on expeditions where poor personal and group hygiene was the norm. Be aware that MRSA infections—Methicillin-Resistant Staphylococcus aureus—are highly contagious and can be acquired through contact with the contaminated clothing or the skin of an infected person. MRSA bacteria may enter the body at the site of a minor wound or present as swollen, painful bumps that resemble pimples or a spider bite. This may quickly turn into a painful abscess that requires surgical draining. A few cases will continue to progress to a systemic infection, and fewer still to sepsis.
Lower respiratory infections are also relatively common in the outdoors, especially on longer expeditions; fortunately most resolve with simple rest and fluids. That said, some, particularly those associated with a flu virus, may progress to a pneumonia. Symptoms of a pneumonia vary from mild to severe but typically include a dry or productive cough, fever, chills, fatigue, and respiratory distress. Some people experience a sharp or stabbing pain that gets worse with a deep breath or cough.
Urinary tract infections (UTI) are relatively common among females in the outdoors and are often linked to poor hygiene and/or chronic dehydration. Treatment with antibiotics is recommended to prevent the infection spreading to the kidneys and blood. Once active in the blood, sepsis is possible.
Travelers diarrhea caused by some strains of E. coli may lead to a systemic infection and sepsis, as can any intestinal infection that results in a perforated bowel: diverticulitis, appendicitis, ulcerative colitis, Crohn’s disease, strangulated hernia (which can result in poor blood flow to the intestines), peptic ulcers, etc. All require an urgent evacuation to a hospital for physician assessment and follow-up treatment; refer to the “Red Flag” signs and symptoms for an urgent—level 1 or 2—evacuation listed in our Wilderness Medicine Handbook.
Sepsis is rare on wilderness expeditions for a number of reasons:

• Sepsis rarely occurs in healthy adults with good personal and group hygiene. (Focusing on personal and group hygiene goes a long way to preventing the index infection.) That said, remember that the risk of sepsis from a local infection increases in immunocompromised individuals and patient’s greater than 65 years old, especially those in poor health.
• Patients with a local infection are typically evacuated early in the continuum in order to prevent a systemic infection; or if one already exists, starting a course of broad-spectrum antibiotics during the evacuation helps prevent the infection from worsening.

Sepsis S/Sx

• A probable or confirmed local skin, lung, GI or GU infection plus two of the following:
• Core temperature greater than 102º F (38.9º C) or below 96.8º F (36º C)
• A pulse rate greater than 90/min; a patient’s pulse rate increases roughly 10 beats/min for every degree increase in core temperature.
• A respiratory rater higher than 20/min; a patient’s respiratory rate increases roughly 2 beats/min for every degree increase in core temperature. (Breathing fast “blows off” carbon dioxide; lab results in a patient with sepsis will show low levels of blood CO2 (PaCO2 < 32; normal = 38-42).

White blood cell production increases in an effort to combat the infection by releasing nitrous oxide and cytokines and engaging in phagocytosis (cell eating). Nitrous oxide causes the blood vessels to dilate and increase the permeability of their walls leading to plasma leaks. And, as plasma leaks into tissue spaces, it takes oxygen longer to diffuse into individual cells. Cytokines are proteins that activate the patient’s cellular defenses and immune system. Pulse and respiratory rates increase in patients with a fever to increase oxygen delivery to tissues. The increased pulse rate also helps maintain the patient's blood pressure.

Severe Sepsis S/Sx
The S/Sx of Sepsis plus one of the following—which may indicate initial organ failure:

• Significantly decreased urine output indicates kidney failure. As kidneys fail, urine output drops and the kidneys are no longer able to clear toxins from the blood or balance blood pH. (In the hospital decreased urine output with fluid bolus via large-bore IVs indicate sepsis.)
• Abrupt change in mental status
• Respiratory distress indicates damage to the blood vessels in the patient's lungs.
• Irregular pulse or heart sounds indicate heart damage.
• Severe abdominal pain often indicates a perforation.

Septic Shock S/Sx

• S/Sx of Severe Sepsis plus a drop in blood pressure. (Initially, the patient’s pulse rate increases in an effort to maintain BP; however, if septic shock progresses and the heart is damaged, the pulse rate and blood pressure will drop. Death will ensue.)

WORSENING SYSTEMIC INFECTION
Systemic vasodilation + increased vascular permeability > Systemic leakage > Increased pulse & respiratory rates > Organ failure > Decreased BP > Death

Treatment

• Immediate Level 1 Evacuation if sepsis is suspected.
  
• Begin a course of broad-spectrum antibiotics. Consider adding an anti-fungal if available and no response within 2-3 days.

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