Scientific Evidence
TIVA has advantages for patients
Gaseous anaesthesia is contraindicated in some patients and virtually impossible to administer in others. International guidelines from UK specialists recommend that all anaesthetists should be able to deliver TIVA competently and safely.
Longer term patient benefits
Retrospective analysis has shown that patients with cancer live longer if given TIVA rather than gaseous anaesthesia. Laboratory derived findings support these emerging clinical outcome data and randomised control trials of the potential for improved outcomes in patients with cancer who are anaesthetised with TIVA are now being undertaken.
TIVA has advantages for healthcare workers
The hazards to healthcare workers of occupational exposure to low doses of gaseous anaesthetics include reduced mental performance and manual dexterity and an increased risk of miscarriage, genetic damage, and of cancer.
Consequently, maximum exposure levels for healthcare workers have been set and incorporated into legal Control of Substances Hazardous to Health Regulations (COSHH).
Despite these regulations, atmospheric pollution in the workplace still occurs.
TIVA has advantages for the environment
Inhalational anaesthetics are greenhouse gases (GHG). According to the UK Sustainable Development Unit 5% of an acute hospital’s carbon footprint stems from anaesthetic gases. Global anaesthetic emissions contribute 3 million tonnes of carbon dioxide equivalent every year. The NHS’ anaesthetic emissions are equal to the emissions from the commute for all 1.3 million NHS staff.
Even when a full cradle-to-grave approach, encompassing resource extraction, drug manufacturing, transport to health care facilities, drug delivery to the patient, and disposal or emission to the environment, is used, the GHG impact of propofol is 4 orders of magnitude lower than that of the anaesthetic gases. There has been a call for the complete abandonment of volatile anaesthesia
The far lower lifecycle carbon footprint of intravenous anaesthesia is accounted for almost exclusively by the electricity required for the syringe pump and not from drug production or direct release to the environment.
TIVA is clean and environmentally safer than gaseous anaesthesia.
Our solution: A real-time blood propofol concentration monitor
Somnus’ innovative technology will enable us to develop products to directly benefit patients, the NHS and the environment.
Learn moreFactors Constraining The More Widespread Use Of TIVA
And the solution that real-time blood propofol monitoring offers
The 5th National Audit Project (NAP5) of the Royal College of Anaesthetists concerned accidental awareness (i.e. the lack of unconsciousness) during general anaesthesia, a fundamental failure of anaesthesia with repercussions that can be devastating for both patients and anaesthetists. The incidence of awareness during general anaesthesia is approximately twice as high during TIVA as it is during gaseous anaesthesia. During gaseous anaesthesia, the expired anaesthetic gas concentration can be used as an indication that the drug is being delivered as intended; this is not possible during TIVA. If the delivery of propofol to the patient is interrupted e.g. by disconnection of the infusion tubing, then this may go undetected as the infusion pump will continue to display adequate delivery.
The development of real-time point-of-care (RtPoC) blood propofol monitoring will provide a means of ensuring drug delivery during TIVA. It will significantly increase the safety and reliability of TIVA.
TIVA delivered by pumps using mathematical models (target-controlled infusion (TCI)) is known to be inaccurate.
The development of RtPoC blood propofol monitoring will enable refinement of the mathematical models underpinning the pump-based algorithms; significantly increasing the efficacy of TIVA.
A study in morbidly obese patients assessed the predictive performance of 5 propofol pharmacokinetic models currently used in TCI pumps. All 5 models underestimated blood propofol concentrations. Similarly, a study of measured vs predicted blood propofol concentrations in children undergoing surgery during target-controlled infusions showed a median performance error of 38.9%. The authors concluded that “propofol target-controlled infusion models had poor performance characteristics in children and that point-of-care propofol assay may enable adjustment of the infusion to better achieve the intended blood level.”
No single monitor of the depth of anaesthesia to demonstrate that a patient is adequately but not excessively anaesthetised exists. Surrogate indicators of the depth of anaesthesia such as processed EEG fall short of providing a reliable depth of anaesthesia monitor. Currently, the anaesthetist must assimilate a range of information provided in real-time to assess the adequacy of anaesthesia without knowing the concentration of anaesthetic drug in the patient’s blood stream.
The development of RtPoC blood propofol monitoring will add significantly to the data available to assess the depth of anaesthesia for any individual patient. It will provide the equivalent of end- expired concentration of volatile agent in the patient’s breath, data anaesthetists employing gaseous techniques use to estimate the adequacy of anaesthesia.
Beyond addressing these current needs, the development of RtPoC blood propofol monitoring offers, by linking its output to the rate of drug infusion, an opportunity to move closer to semi- closed, or truly personalised, anaesthesia for each patient. Such a solution aligns with the UK Government’s publication Personalised Health and Care 2020 , a framework for action that includes proposals to
- give care professionals access to all the data, information and knowledge they need – real- time digital information on a person’s health and care by 2020 for all NHS-funded services;
- bring forward life-saving treatments and support innovation and growth
- maximise the benefits of new medicines and treatments
The development of RtPoC blood propofol monitoring will add significantly to the data available to construct genuinely individual anaesthetic drug regimens personalised to each patient as opposed to assumptions made on demographic data or mathematical models.
Finally, once the system for monitoring RtPoC blood propofol has been optimised it will be adapted to monitor concentrations of other drugs administered by infusion.
The UK government, via its Innovate UK platform, has awarded Somnus Scientific Limited funding for a 16 month research project the end point of which is expected to be a functioning lab-based prototype real-time blood propofol monitor that measures venous blood propofol concentrations at clinically relevant concentrations. The academic partner for this project is the Institute for Bio-Sensing Technology at the University of the West of England (UWE) and the prototype monitor has been developed at the Health Tech Hub, UWE.
The prototype monitor and its novel biosensor has been shown to accurately and reliably detect propofol spiked into a plasma substitute at clinically relevant concentrations.
Real-time blood propofol concentration monitoring will make the use of TIVA safer and facilitate its use in patient groups for whom it is preferentially indicated. One such group might be those who have cancer.
Recent retrospective analyses of clinical datasets suggest that the two major classes of general anaesthetics used during cancer surgery (inhalational agents and intravenous propofol) disparately influence post-operative cancer outcomes. There is also growing laboratory-derived data helping to explain how these drugs exert distinct effects on cancer cells and immune systems. The available evidence tends to support the superiority of propofol in terms of the effect on cancer outcomes. Prospective randomised trials have commenced to bring more rigour to these conclusions.
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