The Karla slide Ruler is designed to decrease the chances of making an error in calculating drug dosages. The device allows medical clinicians to quickly and easily determine the correct amount of drug to be used without mental calculation.

The Slide Rule is made from laminated paper and fits easily into a pocket , so it can be carried around all the time. The front and back section of the ruler provides information on different drugs and their dosages according to age. In the centre part of both sides is the age, as this is key to the way the entire ruler operates.

The Middle section of the slide ruler can be moved from side to side and contains various age groups, weights, vital signs, endotracheal tube lengths (tube down the mouth to the lungs to give oxygen) and defibrillator amounts (defibrillator is the device supplying brief amounts of electric shock to establish normal heartbeat). Medical personnel use the ruler by sliding the middle section to the correct age of their patient and read the outer section for the drug name according to symptoms.

On the back of the pull out section of the Ruler is the Wong Baker Faces Pain Rating Scale. The Wong Baker Faces are for scared and or hurt kids who cannot communicate or describe adequately what kind of pain they are feeling. Kids point to the face they are feeling. If they point at the high numbers 6-10, they are in lots of pain and require pain relief in the form of paracetamol or even morphine. The Wong Baker face pain score has been used for years but the slide rule allows a score of 1-10 which is what most paramedics and hospital systems use now.

The invention also has other uses; for example, in the center on one side of the rule are the vital signs, pulse, blood pressure and breathing rates. This can be useful in an emergency to compare with what the normal rates are. Also positioned in the center of the other side of the rule is the defibrillation rate at the lowest setting of 2 joules of electrical energy per kilogram of weight.

Many people don’t realise that medicines have multiple uses. The drugs listed on the Slide Ruler can treat a number of problems and if the wrong amounts are given, some drugs can be dangerous, so by displaying only the lowest therapeutic amounts of all drugs the risk of error has been minimized. And as ambulance staff don't treat many children it is useful to have a handy list of the only drugs allowed for both children and adults, as advised under Queensland Health policy.