Help Using Nitrous Oxide

Re: Help Using Nitrous Oxide

Claire Bloor — Fri, 16 Mar 2012 21:09:20 GMT

No more than 60% nitrous...typically people use 50:50 nitrous and oxygen.

Definitely advisable where possible to use some monitors (although be aware of their limitations):

pulse oximiter - measures the saturation of haemoglobin with oxygen
capnograph - measures the end tidal carbon dioxide level (thus is the better piece of equipment of the two to assess the efficacy of a patient's ventilatory efforts)

Remember that your FGF rates in anaesthesia are not fixed...you should calculate the standard amount for the patient's weight as you have been taught as a starting point, but you need to be adaptive with regards to the changing physiological status of your patient under anaesthetic.

Re: Help Using Nitrous Oxide

Sarah Balloch — Mon, 13 Feb 2012 15:18:29 GMT

Thank you all for your great info, we had 2 bitch spays on Friday and both went very well. I definitely noticed a difference using the nitrous compared to iso on it's own as the bitches were alot more 'steady' and I was able to leave the iso on 2!

This was my first question on these forums and I didn't think I would get such a quick response so thank you! I'll be sure to get your advice on other topics when they arise!

Re: Help Using Nitrous Oxide

emvn80 — Wed, 08 Feb 2012 11:44:01 GMT

Just to add to the fab answer by Juliet.

That is correct for non-rebreathing circuits (Lack, T-piece, Bain etc). If you are using it with a circle then for starters be careful! Only use it at concentrations of 50% O2 & 50% N2O (ie 1 L each) and make sure you are supplying in excess of the patient's metabolic oxygen demand (ie 10mL/kg) of oxygen. Using Nitrous with a rebreathing circle circuit can deliver a hypoxic mixture (as the oxygen is used up by the patient the N2O continues to circle round the system so the O2 concentration may drop over time to below 30%) so it is important to ideally use inspired gas monitoring to ensure the inspired oxygen concentration is actually >30% or at least a pulse oximeter.

Nitrous can be very useful- it provides some analgesia (not as good as in poeple!) but also reduces the amount of isoflurane you need (& therefore the negative side effects of iso such as hypotension) with minimal cardiovascular effects.

Re: Help Using Nitrous Oxide

Jenny Cook RVN — Wed, 08 Feb 2012 07:29:44 GMT

Thank you :)

Re: Help Using Nitrous Oxide

Juliet Drummond DAVN (med) RVN D32/33 — Tue, 07 Feb 2012 22:41:38 GMT

hi jenny,

its 2 parts nitrous to one part oxygen, less than 50% concentrations of nitrous are of little benefit to the patient, but the concentration should not exceed 70%of the gas mix to avoid hypoxia.

to help with the original question-

to avoid diffusion hypoxia, patients must have oxygen enriched gas (100% oxygen) for 5 to 10 mins after stopping the nitrous.

the main benefit to animal patients is a reduction of anaesthetic agents required to maintain anaesthesia, due to the second gas effect- helps with the rapid uptake of volatile agent.

nitrous should be avoided in patients with conditions such as GDV or pneumothorax, as the nitrous can diffuse into any gas filled pocked causing it to expand.

hope this is of use

Re: Help Using Nitrous Oxide

Jenny Cook RVN — Tue, 07 Feb 2012 22:26:53 GMT

Hi, I haven't got notes to hand but I remember from college to work out the oxygen flow rate and divide by 3. Then its 2 part oxygen to 1 nitrous. Eg, 6 l/min oxygen / by three = 2 So, 4 litres oxygen and 2 litres nitrous (Or might be 2 nitrous and 1 oxygen.) Please if someone wants to correct me, go ahead, lol. In meantime ill double check my notes!! Lol. So please tahnee, don't take my word for it just yet x