Capnography is an essential element when anaesthetising patients. It helps ensure you achieve positive outcomes for your patients, especially neonatal or small patients where there is a larger risk involved. This was highlighted in a recent article in the Veterinary Times (Vol 46 No5) by Carrington-Brown and Walsh.
Sidestream or Mainstream Capnography?
The article states that “Capnography can be used to aid the monitoring of ventilation and cardiac output”, both of which are critical parameters. It continues, “There may be some inaccuracy because of the small tidal volume of neonatal patients when side- stream monitoring is used”.
We absolutely agree; when your patient has a small tidal volume, you have to question the value of removing a constant sample of 125ml/minute for a monitor that probably won’t give you accurate data.
Then comes the contentious bit: “mainstream monitors will be more accurate but the size of the sampling unit may increase dead space and produce physical drag”. This is where we disagree.
The older human capnographs (2nd hand) and the cheaper Chinese units sold as “veterinary monitors” certainly do suffer from this problem. However, the VM-2500-M mainstream capnograph from Thames Medical has a neonatal dead space of just 0.6ml. With such low resistance, even the author (90kg with a tidal volume of 620ml) can breathe through it without too much discomfort.
To ease the minds of the nursing and veterinary staff that I work with, I ask them to breathe through the airway adapter themselves and I haven’t lost one yet!
Cost vs. Performance
The logic is simple; we want to monitor our smaller patients because they are the ones most at risk. It’s really worth spending the extra £500 (rather than opting for the cheapest kit available). Buy the piece of kit that will actually work properly on these very small patients that you need to be really careful with. We know the subject and can support both your equipment and your staff. Buy a VM-2500-M mainstream Capnograph from Thames Medical.
The VM-2500-M is not the cheapest. But it is the best, and probably the only piece of kit that can actually accurately monitor the small risky patients.
Ask yourself: “Which would I want for my pet’s anaesthetic?”
You could opt fot the cheaper one, that might, if you are lucky, get some (all-be-it inaccurate) data. Or, you could purchase the top-of-the-range unit that will capture accurate data for all sizes and species!