Call the Midwife: What is septicaemia – and is it life-threatening?

In a sombre end to Call the Midwife episode six, Dr Turner (Stephen McGann) rushes Nurse Barbara Hereward (Charlotte Ritchie) to hospital with a suspected case of septicaemia. Her shocked husband Rev Tom Hereward (Jack Ashton) is driven to her bedside.

What are the symptoms of septicaemia?

When the blood poisoning begins, the immune system will immediately try to fight the infection in the bloodstream, bringing on alarmingly sudden symptoms. These can include a high temperature, extreme tiredness, violent shivering and chills, faintness, pale and clammy skin, and rapid and shallow breathing.

This is what we're seeing in Barbara by the time her husband Tom goes off to the neighbourhood party, leaving Nurse Phyllis Crane (Linda Bassett) in charge as a precaution. The symptoms worsen and Phyllis makes the decision to summon Dr Turner.

With septicaemia, the skin may also develop "petechiae" (pinprick bruises) or "purpura" (large purple areas) which do not change colour when pressure is applied. One of the first tests Dr Turner carries out when he arrives to visit the patient is inspect her "rash". Petechiae or purpura are caused by blood leaking into the tissues under the skin.

This suggests she has a type of blood poisoning which can lead to meningitis (inflammation of the membranes that surround the brain and the spinal cord) as well as septicaemia. The two often go hand-in-hand, and when meningitis and septicaemia occur together it is referred to as "meningococcal disease".

Particularly worrying is the fact that Barbara can no longer bend her neck, which prompts Dr Turner to send for an ambulance immediately. This symptom makes it likely that the blood poisoning has already led to bacterial meningitis.

In severe cases of blood poisoning, sufferers can go into "septic shock" when blood vessels become leaky and lose fluid, affecting blood flow and damaging vital organs. Blood pressure will drop to a dangerously low level, leading to symptoms including loss of consciousness, disorientation and slurred speech.

What causes septicaemia?

Septicaemia can develop from a wound or burn, or as a result of a serious illness. Nurse Barbara is not in any of the high risk groups (older people, young children, teenagers and people with damaged immune systems), but earlier in the episode she is seen wiping her nose and complaining about a persistent cold which won't go away.

Sources of infection can include pneumonia, appendicitis, peritonitis, urinary tract infections, skin infections and flu – but sometimes the specific cause cannot be identified.

So what's happening inside the body to make this illness so dangerous? White blood cells are very efficient at fighting off infections from bacteria and viruses and will travel to the site of the problem to sort it out and repair the damage. However, sometimes infections can become so serious that they can't be controlled by these white blood cells.

When this happens, the bad bacteria can enter the blood stream and be carried to other tissues and organs, releasing endotoxins and causing severe illness. Bacteria will multiply rapidly, doubling in number around every 30 minutes. It sends the immune system into overdrive and inflames the whole body, which interferes with blood flow and stops oxygen reaching organs and tissues.

When the meningococcal bacteria travel through the blood and reach the meninges (the membranes covering the brain and spinal cord), this leads to meningitis.

How dangerous is septicaemia?

If septicaemia is diagnosed very early, it can be treated with antibiotics at home. But once severe symptoms have begun, patients should be rushed to hospital and treated with intravenous antibiotics injected straight into the bloodstream.

When vital organs are damaged sufferers are likely to become very ill. Most people who get meningococcal disease will make a full recovery, but 5-10% of cases will result in death. Survivors can be left with disabling after effects such as blindness, deafness, brain damage, loss of limbs, and organ damage.

Septicaemia, and more generally meningococcal disease, is not easily transmitted from person to person and cases usually occur in isolation – though people who have shared a kiss with the patient would be at risk. By contrast, viral meningitis is highly contagious.

The only preventative treatment for meningococcal disease is vaccination, including the Men C, Men B and Men ACWY vaccines.