The West Lothian Community Health and Care Partnership along with the local pharmacy department have unilaterally decided that they will no longer supply practices with liquid nitrogen for cryotherapy. The liquid nitrogen had been supplied for over 20 years to our practice. They cite potential health and safety risks in the transport and use of liquid nitrogen. This seems another example of health and safety being used inappropriately.
They say ‘there have been a number of recent incidents regarding the spillage and evaporation of liquid nitrogen during the transportation process and local storage at health centres,’ but do not detail the incidents.
They allude to ‘well documented hazards associated with liquid nitrogen including oxygen deficiency (spillages and venting/leaking dewars), asphyxia, damage to lungs, and cold burns, confined space exacerbation, oxygen enrichment, and ice plugs’.
Apparently ‘The NHS Lothian policy prohibits transportation by car and states it is to be done only by a suitable transport vehicle. This is a vehicle with cab separate to the cab, that is, a box van. The storage facility for the flasks requires further upgrading to meet requirements of the policy and procedure — and as a result of a recent audit in relation to carriage of dangerous goods. Following the recent incidents, transport have reviewed their system and highlighted that local controls are not adequate’.
They also state ‘the current facilities in our health centres and treatment rooms do not comply with the ventilation requirements — estimated cost of £1200 for ventilation to be installed for each room and appropriate alarm system. There is no standard operational procedure in place for reception of liquid nitrogen in the health centres’.
The volume that practices receive was around 500 ml, given the volume of a reception area or a consulting room is probably about 32 000 l (4m x 4m x 3m), then the volume of liquid nitrogen if a gas = 700 × 0.5 l = 350 l. Air is appro×imately 80% nitrogen therefore the volume of nitrogen in the room prior to any nitrogen spill 80% × 32 000 l = 25 600. After the spill of 500 ml of liquid nitrogen this increases the volume to 25 950 l, which is an increase in nitrogen concentration of less than 1%.
The whole scenario seems bizarre, liquid nitrogen historically is the chosen modality of most dermatologists for cryotherapy. Other freezing agents exist but may not be as efficient.
The main driver seems to be cost, however practices can obtain Histofreezer® 150 ml dimethyl ether/propane/iso butane aerosol on stock order in Scotland. This costs approximately £50 for 50 applications. Histofreezer reaches a temperature of –55°C within 15 seconds. There seem to be very few papers on its use, however one from Madrid1 suggests it may be useful and I would be interested to hear of other GPs’ experiences.
However I feel the withdrawal of liquid nitrogen will result in more referrals to dermatologists.
- © British Journal of General Practice 2012
