Infectious Diseases and Sepsis

How diseases spread

Two kinds of microorganism account for most of the infections an EMT meets. Bacteria are living, single-celled organisms that are able to reproduce independently. Viruses are not cells at all: each one is a protein coat enclosing genetic material (DNA/RNA), and a virus can only reproduce by using a host.

Two words that sound interchangeable are not. A disease is infectious when it is caused by a microbe, and communicable when it can spread from person to person. Lyme disease shows the difference. It is infectious, because bacteria delivered by a tick bite cause it, but it is not communicable, because a patient who has it cannot pass it to you.

Communicable disease quick reference

The table below sets out the communicable diseases an EMT is most likely to encounter, how each one is transmitted and the signs that should raise suspicion.

Table 24.1Communicable disease quick reference

Hepatitis, HIV & influenza detail

The hepatitis viruses share a name and a target organ but differ in how they spread and how they end. Hepatitis A spreads by the fecal-oral route; patients usually recover fully, and a vaccine is available. Hepatitis B spreads through blood and other body fluids and can become chronic, carrying a risk of cirrhosis and liver cancer; a vaccine is available for it as well. Hepatitis C also spreads through blood and body fluids, mainly through shared needles. It is often asymptomatic for years, and there is no vaccine against it, although effective curative regimens now exist.

HIV/AIDS is transmitted by needle-sharing, by unprotected sex and from mother to newborn. How communicable it is tracks the viral load: treatment can drive the viral load to undetectable levels, which virtually eliminates the risk of transmission. If you are exposed, wash the site first, then begin postexposure prophylaxis (PEP), a course of antiviral medication taken for 28 days. Timing is what makes PEP work: start it as soon as possible, ideally within hours of the exposure, and never later than 72 hours, after which it is no longer expected to help.

Influenza spreads both by airborne droplets and by contact. Antiviral medication helps only if it is started within 48 hours of the onset of symptoms, which is why recognizing the illness early matters, and the annual vaccine is built around the strains predicted for the coming season.

Tuberculosis & meningitis

A patient with latent tuberculosis (TB) is infected but has no symptoms and is not contagious, and roughly 90 percent of these patients never go on to develop active disease. When TB is suspected, an N-95 respirator is required rather than a surgical mask, because a surgical mask does not filter the small particles that carry the organism. After an exposure, report it to the receiving hospital and have a baseline skin test done, followed by a repeat test later.

Meningococcal meningitis announces itself abruptly. The patient develops fever, a severe headache, nuchal rigidity (a neck so stiff that the chin cannot be brought to the chest), photophobia, and petechiae, small spots in the skin that do not blanch when they are pressed. The complications are severe: shock, brain damage and deafness. Standard Precautions generally protect you; only very close contact, such as mouth-to-mouth ventilation, may warrant prophylactic antibiotics.

STIs, Lyme disease & emerging/resistant disease

Sexually transmitted infections (STIs) divide by the organism responsible. The viral STIs include HIV, hepatitis A/B/C, herpes and human papillomavirus (HPV). The bacterial STIs are chlamydia, gonorrhea and syphilis, all of which can be treated with antibiotics.

Lyme disease is carried by ticks, and in most patients it announces itself with the classic bull's-eye rash within a week of the bite. It responds to antibiotics, most effectively when treatment starts early. A tick generally has to feed for at least 36 hours before it transmits the organism, so a tick found and removed promptly is much less likely to have caused infection.

Antibiotic resistance is a different kind of problem. Organisms such as MRSA, VRE and C. diff spread in patients you will often not know are carrying them, which is precisely why Standard Precautions are applied to every patient rather than to selected ones.

The recently emerged diseases (HIV/AIDS, SARS, Ebola, MERS and Zika) have all followed the same pattern: initial panic, then investigation, then protocols, and finally mitigation. When a new disease is in the news, verify what you hear against guidance from the Centers for Disease Control and Prevention (CDC) or your local health department rather than relying on news reports.

What sepsis actually is

Sepsis is a life-threatening condition that arises from the body's own abnormal and counterproductive response to an infection. The distinction matters: the damage to tissues and organs is done by that response, not by the infection alone. When sepsis progresses to shock, with hypotension that does not respond to intravenous (IV) fluids, it is called septic shock.

Two mechanisms drive the fall in perfusion, in varying combination. The capillaries become leaky, so fluid is lost out of the vascular space, and the vessels dilate, which prevents adequate venous return to the heart.

Infection anywhere in the body can lead to sepsis, but a few sources are common. The lungs, in the form of pneumonia, are one; the gastrointestinal tract, often after surgery, is another; the genitourinary tract, frequently in patients with urinary catheters, is a third; the skin and soft tissue, around IV catheters or pressure sores, is a fourth; and the central nervous system (CNS), as in meningitis, is a fifth. In many cases no source is ever clearly identified.

Assessment — SIRS & qSOFA

Two field tools help you think about sepsis, and they answer different questions. The first is the systemic inflammatory response syndrome (SIRS) criteria. In a patient with a documented or suspected infection, meeting two or more of the following raises the likelihood of sepsis:

• A temperature below 96.8°F (36°C) or above 100.4°F (38°C)
• A heart rate (HR) above 90 beats per minute
• A respiratory rate (RR) above 20 breaths per minute
• A white blood cell (WBC) count above 12,000 or below 4,000, a lab value the hospital obtains, not the EMT

In the field you are working with the three vital-sign criteria. Many EMS sepsis screens add a systolic blood pressure (BP) below 90 mmHg or altered mental status that is new or has worsened. Those are not SIRS criteria; they are signs that sepsis is already affecting perfusion or the brain, and your protocol may count them.

SIRS is an imperfect screen, and you should treat it as a prompt rather than a verdict: trauma patients, for example, frequently meet 2 of the criteria without being septic.

Some septic patients are hypothermic rather than febrile, so do not rule sepsis out on the basis of temperature alone.

The second tool, qSOFA, asks a different question. Its three findings are altered mental status, a respiratory rate of 22 or more and a systolic blood pressure of 100 mmHg or less, and together they do not predict who has sepsis; they predict which septic patients face a worse prognosis. No field tool is 100 percent accurate, so follow your local protocol.

Management

The EMT's care of the septic patient is supportive. Give oxygen as needed to maintain a saturation of at least 94 percent, take steps to keep the patient's body temperature normal, and call for advanced life support (ALS) as appropriate.

The most valuable thing you do may be a radio call. If the patient meets the SIRS criteria, or similar criteria used by your system, notify the emergency department (ED) of a sepsis alert. Earlier diagnosis leads to earlier treatment and to higher survival, and for a stable septic patient that notification is probably the single most valuable action an EMT can take.