What preparation is needed for parathyroid surgery?
The extent of pre-operative preparation depends on the severity of the disease irrespective ofthe surgical approach used.
Severe cases
In severe cases with a grossly elevated calcium the patient will be admitted to hospital for hydration using an intravenous saline drip. This may mean several days in hospital prior to surgery. In very severe cases the drug Pamidronate disodium is given intravenously; this drug has the unique ability to bind to bone crystals and stops the leeching out of calcium from the bones into the blood. Pamidronate is very effective and the serum calcium level usually drops to normal within 24 to 48 hours. The disadvantage of using Pamidronate is that it can post-operatively result in asevere hypocalcaemia (a low serum calcium) which can persist for severalweeks and require supplements to treat.
One novel way which to our knowledge has not been described as a method of preparation is the administration of the calcimimetic drug Cinacalcet. This drug increases the sensitivity of the calcium sensing receptor (CaR) and reduces the secretion of parathyroid hormone and the serum calcium. It is used in the treatment of hypercalcaemia in parathyroid cancer that has failed surgery and also in renal hyperparathyroidism. It may be effective in the long term management of primary hyperparathyroidism but its cost in these circumstances is prohibitive.
Long term use of Cinacalcet is valuable in cases of secondary hyperparathyroidism.TheNICE guidelines in January 2007 do not support its general long term use. Instead NICE recommends it for patients with very high parathyroid levels that cannot be lowered by other treatments and in patients who are unfit to undergo parathyroidectomy with secondary hyperparathyroidism. These guidelines will be reviewed in December 2009.
Mild or moderate cases
In the more common mild or moderate cases with calcium below 3 millimoles per litre (12 milligrams per l00 ml) sensible intake of fluid with restriction of cheese and other milk products is all that is needed. Whether the operation is under general or local anaesthetic it is mandatory to fast six hours prior to surgery.
Because the surgery involves operating near the voice box nerves (recurrent laryngeal nerves) it is advisable for the voice box to be checked by a simple telescope test (indirect or direct laryngoscopy). This is mandatory if there has been previous surgery on the neck. In our view neuromonitoring of the recurrent laryngeal nerveshould be used in all operations except when the surgery is performed under local anaesthetic.
The use of pre-operative methylene blue
For years surgeons have sought out dyes that selectively stain the parathyroid gland making them distinctive colourat parathyroid exploration. Originally one used toluidine blue to selectively stain the parathyroid glands making them distinctive at the time of operation. Unfortunately toluidine blue was toxic to the heart and its use was stopped. In1971 Nick Dudley from Oxford described the use of a methylene blue infusion as a method of colouringthe parathyroids at the time of operation.Dudley used an infusion one hour prior to the estimated time of neck exploration of 5mgs perkilogram body weight of methylene blue in 500 mls of 5% dextrose and 1/5th normal saline.For years methylene blue infusionswere usedand atany major parathyroid meeting the audience opinionwas usually equally dividedabout its useand its safety.I unlike Bambach and Reeve who published in 199720 cases ofmethylene blue for parathyroid identification and suggested it was safe have never beeninfavour of the use of methylene blue since it has structural similaritiesto the phenothiazines.I have neverregarded it as an innocuous drug .This view has been confirmed in recent years by several authors. In 2006an anaesthetic department from Birmingham UK reported a methylene blue induced coma needing dialysis and in the same year David Scott-Coombes and co-workers from Cardiffcommented that in an audit of 25UK surgeons there wasa 44% incidence ofadverse reactions to a methylene blue infusion.This data prompted the Cardiff group to suggest that methylene blue was dangerous and its use stopped. Patients would be wise to ask their surgeons if they use methylene blue and if they do so to be warned of its possible risks.The UK based National Poisons Information Service states that if methylene blue is used its dose should not exceed 4mg per kg body weight.This dose isless than Dudley originally used.My own view is that methylene blue is potentially dangerous and should not be used at alland that if it is and complications occur the surgeon is at risk of a claim of a breach of duty of care.Such a claim iswhich is likely to be sucessful.
Apart from the risks of the methylene blue, the peudocyanotic of the patients skin andthe passing of blue urine for up to a week after surgery is disconcerting to say the least!