Sodium under suspicion

There are lots of sodium compounds but the one that accounts for most of this element in our lives is salt (NaCl) in which the sodium is present in its most stable state: the positively charged sodium ion, Na+. It is not technically a poison but it is a cause of concern because doctors believe that too much salt puts unnecessary stress on the human frame and especially in those with a predisposition to high blood pressure and heart disease, resulting in a situation where the body is less able to remove unwanted salt and so it compensates by retaining more water. This causes increased pressure on the arteries, resulting in high blood pressure with all the risks to health that this implies. Nevertheless, it is necessary to take in a regular supply of sodium because it is continually lost from the bloodstream as it is filtered out by the kidneys.

The amount of sodium a person consumes each day varies from individual to individual and from culture to culture; some people get as little as 2 g per day, some as much as 20 g. Foods which have a lot of salt include tuna, sardines, eggs, liver, butter, cheese, and pickles. Vegetables generally have very little. Although a lot of sodium is recycled within the body, a lot is lost via urine (which contains around 350 ppm), the faeces, and the sweat glands.

Blood tastes salty because it contains a lot of salt, 0.35% in fact. Our skeleton contains a lot also (1%), as do most tissues of the body, which is why the total body burden of this element is 100 g. Sodium in the body is mainly in the fluid outside cells, the situation being just the opposite to that which pertains with potassium. Blood needs a lot of sodium to regulate osmotic pressure and blood pressure, as well as to help solubilize proteins and organic acids.

Salt is a blessing in tropical countries, where it has saved millions of lives. Diarrhoea, and the resulting dehydration it causes, is reported to kill millions of children a year. The simple answer to this potentially fatal illness is to drink a solution of glucose and salt and the United Nations children's organization, UNICEF, distributes millions of sachets for making up such solutions.

While such use of salt saves lives, it also has the power to harm, if not to kill. Too much salt taken in a single dose will provoke the toxic response of vomiting. This would suggest that it would be impossible to murder somebody by feeding them salt, but it was just how 39-year-old Susan Hamilton of Edinburgh, Scotland, repeatedly poisoned her daughter. Hamilton appeared before a jury on 6 June 2003 and, after a three week trial, she was found guilty of 'assault and the endangerment of life' and sentenced to four years in jail. She committed the crime three years earlier, on 10 March 2000, when she had injected concentrated salt solutions into the feeding tube that doctors had inserted into her daughter's stomach.

Her daughter, who could not be named for legal reasons, was born in 1991; she had muscle problems that made it hard for her to swallow and the doctors to whom she was taken thought she had a wasting disease. When she was four, the decision was taken to feed the girl via a naso-gastric tube which is inserted up one nostril and then goes down into the stomach, but this too had appeared not to be successful and eventually she had had a percutaneous endoscopic gastrostomy tube inserted directly into the stomach. All this may have been unnecessary in view of what her mother was doing, but at the time it seemed the right course of treatment.

Time and time again Hamilton reported that her daughter was very ill, which led to repeated admissions to Edinburgh's Royal Hospital, and each time her examination revealed very high levels of sodium in her blood. Because there are medical reasons why sodium levels can be higher than normal, this did not at first raise suspicions, but eventually the doctors treating the child came to the conclusion that she was being deliberately poisoned. Neither the special foods that the girl was being given, nor the medication that she was taking would raise her blood sodium levels to the extent being observed. The police were called in and when they went round to the Hamiltons' home they discovered a syringe which contained drops of liquid. This was taken away for forensic analysis and the liquid identified as salty water.

Susan Hamilton's last attempt to poison her daughter had almost killed the child, but in any case it had left her permanently damaged. The hospital records revealed that she must have been repeatedly injecting solutions of salt into her daughter's feeding tube and on 17 separate occasions she had made the child so ill that hospitalization was necessary. Indeed the poor girl was thought at one stage to be developing leukaemia and a 'Dream Come True' trip had been organized to take her to Euro Disney in the belief that she was terminally ill.

Hamilton was administering the equivalent of two teaspoonfuls of salt to the girl to make her ill but on the final occasion of March 2000 she had given her so much that the child suffered a stroke which then left her permanently brain damaged. The explanation for the mother's behaviour was Munchausen's syndrome by proxy.

Blood Pressure Health

Blood Pressure Health

Your heart pumps blood throughout your body using a network of tubing called arteries and capillaries which return the blood back to your heart via your veins. Blood pressure is the force of the blood pushing against the walls of your arteries as your heart beats.Learn more...

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