BSOA Project Grant
The effect of paediatric tourniquets on tissue oxygenation levels using Near Infra-Red Spectroscopy (NIRS)
Dr Anuraag Guleria
Limb tourniquets are routinely applied in certain orthopaedic and plastic surgical operations in order to minimise patient blood loss and to improve the surgical view of the operating field. A tourniquet applies direct pressure and works by reducing the blood flow to the area of the body to which it has been applied. In addition to reducing blood flow they also reduce the supply of oxygen and removal of waste products from the limb. Complications such as pain, hyperthermia, blood clots, nerve damage, temporary and permanent limb paralysis, muscle weakness and severe muscle damage (rhabdomyolysis, compartment syndrome) have been observed in both the adult and paediatric population. The current guidance on the safe use of tourniquets is not evidence based and in children it is adapted from adult practice, for which evidence was generally translated from animal studies.
Near infra-red spectroscopy (NIRS) is a non-invasive monitor that has been successfully used to measure tissue oxygen level. It is routinely used in paediatric cardiac surgery to monitor cerebral tissue oxygenation and protect against ischaemia (cell damage/death primarily due to a lack of oxygen) during periods of critical perfusion (significantly reduced blood flow). Studies have also used NIRS to measure oxygen levels in muscle tissue and within the liver.
We aim to use NIRS to measure the drop in tissue oxygenation levels (RsO2) and time to recover from ischaemia cause by the application of the tourniquet. We hope to evaluate the impact of tourniquet inflation time and tourniquet inflation pressure on tissue oxygen levels and tissue oxygen recovery time. Each patient will act as its own control i.e. we will take measurements from the opposite limb and use these to compare. Other measurement parameters: FiO2 (inspired oxygen), ETCO2 (expired carbon dioxide), SpO2 (oxygen saturations) and NIBP (non-invasive blood pressure).
We aim to add the current evidence base on tourniquet use and potentially influence current guidance and clinical practice - there are very human studies and similar paediatric studies do not currently exist.
Statistical analysis has revealed that we require 15 cases to complete our Pilot Study.
Patient Inclusion Criteria: ASA Class 1 or 2; Age 5-15 years. Exclusion Criteria: Patient/parental refusal, contraindication to tourniquet use, regional or neuraxial blockade, vascular pathology, myopathy or neuropathy, blood disorders, skin sensitivity or allergy, contralateral limb pathology.
