Equipment in Regional Anesthesia
Question:
Are stimulating catheters less prone to shearing due to their electric wire? Which sort of stimulating catheter would minimize this risk?
Answer:
There is no data to answer this question so I will give you my personal opinion.
I am convinced that all stimulating catheters are prone to shearing but that this is an extremely remote possibility. In my personal experience of placing many stimulating catheters, I have never experienced one single incidence of catheter shearing. So, I thin this is purely a theoretical problem, which stems from our training in epidural anesthesia. We were trained never to retract an epidural catheter back through the needle, but in our training with stimulating catheters, we add that if it necessary to retract a stimulating catheter or any other catheter, it should be done carefully. If the catheter is stuck or does not retract readily and without any force, one should pull back on the needle and catheter as a unit. This straitens out the catheter and usually this is all that is necessary to pull the catheter back.This maneuver usually un-sticks the catheter. But if the catheter is still stuck to the needle, the needle and catheter should be removed as a unit and the needle recited.
Yours sincerely,
André Boezaart
Question:
There are needles with plastic sheaths left in place for placing catheters through; examples are Venflon and Pajunk Plexolong. Would it not protect against shearing of the stimulating catheter if it were threaded through the plastic sheath? Would this give up the possibility to direct the catheter?
Answer:
The second part of your question answers the first part. If plastic sheathing is used and the catheter is placed through this sheath, it would be impossible to shear the catheter. It would also be impossible to accurately place the catheter. It would only be possible to test afterwards if the catheter is correctly placed. Let me explain: The problem comes when the catheter takes the wrong route and needs to be redirected. If in the Venflon and Pajunk Plexolong system, the catheter is placed and if it is decided that the catheter is in the wrong position, the whole procedure needs to be repeated, i.e., the catheter and needle need to be removed, the metal part of the needle reinserted, the needle and catheter re-positioned, and again one would hope that the catheter is in correct position. If it is again not in the correct position, the whole procedure needs to be redone.
In short therefore, placing catheters through a plastic sheath will only give you a retrospective answer that the catheter is correctly placed or not. If it is not correctly placed, the whole procedure needs to be repeated, and using a plastic sheath deprives one of the ability of directing and redirecting the catheter.
Therefore, it makes perfect sense to use a metal needle with a Tuohy tip through which the catheter can be directed and redirected. Obviously, one needs to be very careful when withdrawing the catheter. If the catheter gets stuck to the needle, the needle needs to be pulled back slightly to straiten out the bend in the catheter. In my personal experience of many catheters, I never encountered one single case of catheter shearing and I think this is a very, very remote possibility stemming from our teaching in epidural block that one never pulls back a catheter once it protruded beyond the tip of the needle. That teaching is still very valid but we only add that if it is necessary to retract a catheter, it should be done carefully. If the catheter is stuck, the needle and catheter should be redrawn as a unit.
I trust that this answer is satisfactory and that it adds some value to your practice.
Yours sincerely,
André Boezaart
Question:
What type of needle do you consider best for directing and placing a stimulating catheter (Tuohy, pencil point)?
Answer:
The pencil point needle has been proven effective in eliminating or significantly reducing post-dural puncture headache. The mechanism by which it reduces the post-dural puncture headache is by “traumatizing” the dura, rolling it up and causing edema. (Reg Anesth Pain Med 2000; 25(4): 393 – 402) This, as opposed to what happens to the clean cutting edge of the Quincke cutting needle, causes the hole in the dura to close and minimizes CSF leakage. The very reason for the pencil point needle is therefore the trauma, edema and tissue reaction that it causes.
It would therefore, make absolutely no sense to use a pencil point needle for peripheral nerve blocks. On the other hand, the Tuohy needle was primarily designed to avoid penetrating the dura during epidural block. Because the nerve roots as they exist the neuro foramen of the vertebra, are largely surrounded by dura, it makes perfect sense to use a Tuohy needle around nerves, especially where dura is still present.
There is no data available on this issue and therefore, I can only provide you with my personal opinion on this matter. Personally, I have experience of trying to place Tuohy needles and bullet-tip catheters into the nerve of pigs under direct vision and as of yet, I have not succeeded in intra-neural placement of catheters this way. It is therefore my contention that the thicker and the blunter the needle, the better. I think it is absolutely wrong to use pencil point needles around nerves. To answer your question, I regard the 17 or 18-gauge Tuohy needle the best for directing and placing stimulating or any other catheter.
I trust that you find this answer satisfactory and that it may add some value to your practice.
Kindest regards,
André Boezaart
Question:
We fix our catheters with an epidural fixation device. I have adapted the Portex “Lockit” device from my Pediatric epidural practice. I find that when placed on skin prepared with Tincture of Benzoin, it provides very good fixation and to date, I haven’t had a problem with dislocation over 2-3 days. With this technique, the patients remove the catheter themself. Approximately, 80% of our patients are government funded in the private sector so cost if very much an issue. If we have to get a nurse visiting the patient like your institution does, I think we would have to stop doing this. I am therefore interested in the patient that you mention that “attracted medical legal attention”. Was this in the context of tunneling?
Answer:
Thank you for this interesting question.
I think your solution to this problem is excellent, and I would have absolutely no problem in sending these patients home and asking them to remove their own catheters. I am convinced that some of the problems we had been because there was a minute “skin bridge” of the dermis of the skin but that excluded the epidermis, so it was not evident. This caused the catheter to kink and got stuck and this caused the catheter to break on removal.
I applaud your innovation and I think your solution to this problem is an excellent solution. I will implement this into my own practice and evaluate it. Even if it does mean that a higher percentage of catheters dislodge, if this percentage is acceptably low, it would still be a satisfactory solution. The tunneling of the catheter does add complexity to the situation and I fully agree with you that if we could get rid of it, it would be an advantage.
Thank you for adding this value to my personal practice. I think it is a great solution and I will certainly implement it and report back to you on my experience.
Yours sincerely,
André Boezaart
Question:
Catheter would not go through needle tip of Arrow kit. Good stimulation of femoral nerve with the needle (lost at 0.3mA) but was unable to feed the catheter despite several manipulations of the needle. Upon taking the needle out of the patient I noted that the catheter was getting caught at the tip at the junction of the catheter edge/stimulating tip. With considerable force the metal tip would protrude further but the plastic outer sheath wouldn’t budge. With even more force i manage to push the catheter through but it seemed there was a small plug of plastic attached at the interface between the plastic and metal of the catheter. I am wondering if it may have been a bit of the insulating material, which somehow got caught on the inside of the needle tip. Do you know how the insulation is applied to the Tuohy needle and if it would be possible for some of it to get inside the needle?
Answer:
Never heard of this before. I will pass it on to Arrow for their response. Did you take pictures of it? If you have good pics, a letter to the editor may be a good idea, but if you are only speculating they will probably not publish it.