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Could anyone advise on the optimum dosage of cryotherapy for treating plantar VP's? Thanks

Depends how much you like you like your patient and what type of cryo.

Liquid nitrogen
I usually start with a single dose of 30 seconds with an ice ball slightly larger than the lesion (and obviously following an aggressive debridement) I have been know to go up to 45 seconds and have seen a dermatologist do a one minute freeze (ouch). For resistant lesions i will sometimes do the cryo then apply 60% sal acid.

nitrous oxide
Don't use this any more but i had good results with 3 X 1 minute freezes in one sitting.

Don't know if this helps.

Regards
Robert

Related threads:
Cryosurgery or salicylic acid for warts?
Cryotherapy to treat verrucae in young children
Cryosurgery in the treatment of verrucae on toes

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We use a Spembly system set up for use with Carbon Dioxide.

We use one 3-minute freeze on smaller lesions, but re-apply another 3 minutes after thaw-out for larger, longer-standing lesions. Ensuing blister is debrided after seven days.

Regards,

Hi Robert
Re:
nitrous oxide
Don't use this any more but i had good results with 3 X 1 minute freezes in one sitting.

Please could you advise your reasoning behind the above discission. I am just about to start offering cryosurgery as an option in my practice and have invested in a CryoPen (N2O) as I felt the flask of liquid nitrogen would be wastful in a small practice such as mine.
Also would anyone else be able to advise if N2O is useful for anything other than the usual VP's, I was wondering if anyone had used it to numb the injection area prior to using LA in nail surgery.
Wendy

Wendy;
I have no direct experience w/ the cryo pen but have talked to several docs who use it. It seems that you apply the stream of N2O from the pen for 5 second per millimeter of depth of the lesion. I think they suggest 30 seconds per lesion in general, thaw and then repeat.

They say no local anesthetic is necessary.

I hope this helps.
Bruce

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Hello

Ivan G or other CO2 users could you advise on the method used when applying CO2. I imagine it is formed into a pellet and applied to the wart. Does it stick to the wart? If so how do you get it off.

Hello

Wendy I believe with the cryopen perfectII pen, once opened the cartridge leaks so that in frequent use could work out expensive. Is this the one you've got? I would love to hear of your experiences with it.

Hi johnatperth,

Sorry this reply is coming so late!
Actually we use a Spembly Cryosurgical Unit adapted for use with CO2. The use is the same as for N2O. Contact of the probe is limited to 3 minuts, and repeated after thaw-out for larger lesions. The contact are is enhanced by a ball of aqueous gel (e.g. KY-Jelly).

Regards,

Thank you Ivan

The spembly unit looks like it uses gaseous CO2 from the pictures I've found on the internet. I've heard that country GP's use liquid CO2 to produce a snow or pellet and wondered if any pods have had experiences with this.

Hi johnatperth
An update on my Cryopen......I have found that I need 1 cartridge per pt however in saying that have not had that many suitable VPs for freezing since purchasing, the warts (fingers - collegue/family member) I have treated have reacted favourably however and am hopeful for future VPs.
Wendy

Hi all,

Just a couple of things to throw into this conversation:

There used to be (I don't think it is still available) a device called a 'Kidde dry ice maker. It might be this that johnatperth has heard of. A gas cartridge was emptied into the outer chamber of the device, creating CO2 'snow'. This was compressed into an ice pencil in an integral syringe-like applicator which could then be applied directly to the VP. It worked well, created a good ice ball, and the direct contact of the dry ice gave the rapid temperature reduction which is recognised as necessary for maximal cellular damage. Unfortunately the gas containers became difficult to obtain, and this lead to the introduction of the Cryopen (that works on a different principle).

The second thing I think should be mentioned in this thread is the value of multiple freezing. The ice ball needs to form as quickly as possible (to create the highest number of microcrystals that physically do the damage to the frozen cells). It has been said that the therapeutic temperature of -60 degrees Celsius must be attained. The ice ball is then allowed to thaw slowly (again for maximal damage). The second freeze episode applied at the end of the thaw period is considered to be more damaging than the first since the already damaged cells are no longer able to put up any defence and succumb completely, beyond recovery.

From this it might be understood that the freezing agent (cryogen), and to some extent its temperature, are not all that important. But fast freeze, slow thaw, repeat freeze are all desirable parameters. Direct contact probes or cryogen seem to favour rapid cooling and allow negative pressure technique where the ice ball can be raised to limit the depth of the freeze to subcutaneous tissues.

These ideas and more come from a book the title of which I cannot remember, by an American author, Zaccariah?

I used to love the spembly system. Had the CO2 and the N2O at different time. Got N2 now and its not as good IMHO.

Fully agree with John on the multiple freezes.

Regards
Robert

All,

Cochrane review (I've attached the full review in .PDF):

Here's the bit on cryotherapy if you can't be bothered to download and read it all:

Efficacy
Seventeen trials of cryotherapy were included with cryotherapy
being the main focus in 13 trials.
Four trials (Hansen 1986; Sonnex 1988; Berth-Jones 1994; Connolly
1999) examined the benefit of ’aggressive’ versus ’gentle’
cryotherapy (comparison 15). Although these trials were in different
populations, on different types of warts and used different
definitions of aggressive and gentle (see below), it was felt that the
results could be usefully combined for analysis.
• Berth-Jones 1994 - double versus single freeze
• Connolly 1999 - 10 second freeze versus a gentle freeze
• Hansen 1986 - 2 minutes versus 15 seconds with a cryoprobe
• Sonnex 1988 - 20 or 30 second freeze with local anaesthesia
versus 10 or 15 second freeze (hands and feet respectively)
Pooling of data showed aggressive cryotherapy to be significantly
more effective, with cure rates of 159/304 (52%) versus 89/288
(31%), which translates to a 90% increase in the cure rate (RR
1.90, 95%CI 1.15 to 3.15) and aNNT of 5 (95%CI 3 to 7). Unfortunately,
reporting of side effects was less complete and pooling
of data on pain and blistering was not possible. The impression
from those trials that did comment on adverse effects was that,
not surprisingly, pain and blistering were more frequent with aggressive
cryotherapy.
There were three trials (Bourke 1995;Bunney 1976a; Larsen 1996)
examining the optimum treatment interval that showed no significant
difference in long term cure rates between treatment at two,
three and four weekly intervals (comparisons 12,13 and 14). The
frequency of pain and blistering was higher with shorter treatment
intervals although this may have been due to seeing participants
sooner after treatment.Generally, data on side effects were sketchy.
The two trials (Bunney 1976b; Steele 1988i) that compared
cryotherapy (weekly and three weekly respectively) with topical
SA/LA on hand and foot warts (comparison 11) have already been
discussed under ’trials of salicylic acid and other topical agents’.
Only one trial (Berth-Jones 1992b) examined the important question
of the optimum number of treatments and this showed no
significant benefit of prolonging three weekly cryotherapy beyond
three months (approximately four freezes) in a large population of
adults and children with warts on the hands and feet.
Two small trials (Wilson 1983; Gibson 1984), both classified as
low quality by the authors, contained a cryotherapy and placebo
group and both included another topical treatment (DNCB and
acyclovir respectively). Pooled data from these trials (comparison
10) showed, surprisingly, no advantage of cryotherapy over placebo
(RR 0.88, 95% CI 0.26 to 2.95). One of these trials (Gibson
1984) showed an unusually low cure rate (1/11) for cryotherapy
consisting of four double freezes at intervals of two weeks and the
other (Wilson 1983) showed a relatively high cure rate (8/20) in
its placebo group after four months of ’treatment’.
A more recently published trial (Focht 2002), classified as medium
quality by the authors, compared occlusive treatment with duct
tape and cryotherapy in 61 children and young adults. The duct
tape was applied for six and a half days every seven days and
cryotherapy given for ten seconds every two to three weeks up to
a maximum of six times. Cure rates in the intention to treat population
were 22/30 (71%) and 15/31 (46%) respectively, which
translates to a 52% increase in cure rate in the participants using
the duct tape (RR 1.52, 95% CI 0.99 to 2.31). The trial was relatively
small, and some would say that 10 seconds of cryotherapy is
inadequate. An unspecified number of outcome assessments were
carried out over the telephone and it is not entirely clear how long
after the treatment period this was done. Despite these weaknesses
(Abramovits 2003; Buccolo 2003) this properly randomised and
blinded trial adds weight to the argument that simpler and safer
treatments are likely to be at least as effective as cryotherapy and
possibly more so.

Adverse events
Only two trials had precise data on adverse events. In one trial
(Connolly 1999) pain and/or blistering in was noted in 64/100
(64%) participants treated with an ’aggressive’ freezing regime
(10 seconds) compared to 44/100 (44%) of those treated with
a ’gentle’ regime (brief freeze) regime. This translates to a 45%
significant increase in pain and/or blistering in the ’aggressive’
group (RR 1.45, 95%CI 1.12 to 2.31), and a number needed to
harm (NNH) of 5 (95% CI 3 to 15). Five participants withdrew
from the aggressive group and one from the gentle group due to
pain and blistering. In the other trial (Bourke 1995) pain and/or
blistering was reported in 29%, 7% and 0% of those treated at
1, 2 and 3 weekly intervals respectively. The higher percentage of
reported adverse effects with a shorter interval between treatments
might have been a reporting artefact due to participants being seen
sooner after each treatment. Pain (ranging frommild to severe)was
reported in all 25 cryotherapy participants by Focht et al (Focht
2002).

Conclusion
Inconclusive evidence concerning the relative merits of cryotherapy
compared with placebo and other simpler and safer treatments.

Authors’ conclusions for the review
There is a considerable lack of evidence on which to base the rational use of topical treatments for common warts. The reviewed trials are highly variable in method and quality. Cure rates with placebo preparations are variable but nevertheless considerable. There is certainly evidence that simple topical treatments containing salicylic acid have a therapeutic effect. There is less evidence for the efficacy of cryotherapy, but reasonable evidence that it is only of equivalent efficacy to simpler and safer treatments.

I can hear you "justifying" your use of cryotherapy as I type this. The evidence may be lacking, but the evidence we do have seems to suggest that there are "simpler, safer" equally efficacious treatments that the patient could maybe just do at home...

Or perhaps you could point out some published data which makes the conclusions from the Cochrane review wrong? Have a nice weekend .

Attached Files

CD001781.pdf (434.3 KB, 14 views)

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From the Cochrane Review:

"The best available evidence was for simple topical treatments containing salicylic acid, which were clearly better than placebo. Data pooled from five placebo-controlled trials showed a cure rate of 117/160 (73%) compared with 78/162 (48%) in controls, which translates to a risk ratio of 1.60 (95% confidence interval 1.16 to 2.23), using a random effects model.

Evidence for the absolute efficacy of cryotherapy was surprisingly lacking. Two trials comparing cryotherapy with salicylic acid and one comparing duct tape with cryotherapy showed no significant difference in efficacy."


I have read somewhere the Cochrane review summarised in this manner:
Salicylic acid success rate 70%
Cryotherapy success rate 40%

In my own practice I have used cryo to break a deadlock when not making progress i.e. add potency to other treatments.
If you can't knock out a VP with straight jabs, throw in an uppercut!

So, if at first you don't succeed...
Try something demonstrably less efficacious but more painful.

Nice work fella.

Just playing John

Although, if you believe that cryotherapy success rate is only 40% this really does not bode well since ""The best available evidence was for simple topical treatments containing salicylic acid, which were clearly better than placebo. Data pooled from five placebo-controlled trials showed a cure rate of 117/160 (73%) compared with 78/162 (48%) in controls" In other words placebo gives 48% success, while you're claiming 40% success from cryotherapy. Oh dear.

Rub some emollient onto my foot, it's painless and there's a 48% chance of getting rid of my VP. Alternatively, freeze it, make it hurt like **** and come up in a blood blister and there's a 40% chance that it will go away- with multiple treatments, which means multiple pain and multiple blisters. I like to give my patients an informed choice. Which one would you choose?

Interested in the idea of mixing therapies to "add potency"- what does the literature tell us on this?

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Hi Simon and all,

The literature, so far as I am aware, does not address the concept. But I have very successfully applied the concept in practice and I firmly believe from close observation of its effects that it has reasonable and rational basis.

If what we are doing (to eradicate VPs) is not working it suggests poor ethics and little sense to keep on repeating such application at a fee each time.

The client will already have tried most things to rid themselves of a VP, and they come to us with the reasonable expectation that we will do something they cannot do for themselves. To this end, adding a freeze episode is intended to create a local conflict (cause tissue damage / inflammation) that might (hopefully) bring on a series of events culminating in resolution. If nothing else, it no doubt works on a psychological level to convince the client that we are still trying!

Rather in the manner of polypharmacy, the sum of two methods is greater than either one applied in isolation ......... 2+2=5 !!!

Cryotherapy is a misnomer. It is not exactly therapy! It sets out with the intention of killing virus infected cells. If salicylic acid is insufficient to the task, a dose of cryogen (a sterile pathogen) must help!

40% chance of doing harm to do good, 60% chance of doing harm for the sake of doing harm. And the Hippocratic oath says...

Just a thought.

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Yes it does, it's in the Cochrane review I posted yesterday:

Two trials (Bunney 1976b; Steele 1988i) that compared cryotherapy
(weekly and 3 weekly respectively) with topical SA/LA on
hand and foot warts (comparison 11) showed no convincing difference
in efficacy between the treatments (RR 1.04, 95%CI 0.88
to 1.22). A trend towards both treatments together being more
effective than either treatment alone was reported (RR 1.24, 95%
CI 1.07 to 1.43 for cryotherapy + SA/LA versus SA/LA alone; and
RR 1.20, 95% CI 0.99 to 1.45 for cryotherapy + SA/LA versus
cryotherapy alone), all using a random effects model (comparisons
16 and 17).

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Thanks Simon for reminding me of the statements made in the Cochrane Review: Gibbs S, Harvey I. Topical treatments for cutaneous warts. Cochrane Database of Systematic Reviews 2006, Issue 3. Art. No.: CD001781. DOI: 10.1002/14651858.CD001781.pub2.

"Main results
Sixty trials were identified that fulfilled the criteria for inclusion. The evidence provided by these studies was generally weak due to poor methodology and reporting."

I just want to point out that:
"Two trials (Bunney 1976b; Steele 1988i) that compared cryotherapy
(weekly and 3 weekly respectively) with topical SA/LA on
hand and foot warts (comparison 11)"
is not highly convincing and does not relate to plantar VPs alone. Nor does it have much relevance to the principle to which I referred.

How was the cryotherapy applied? Cryogen boiling point? Freeze duration? Multiple freezes? SA/LA? (Is that Lactic acid crept in there?) What concentrations? How applied? For how long? And just look at the frequencies of application.

The evidence base is only as good as the evidence contained therein.

To quote Sackett et al 1996:
"The practise of evidence based medicine means integrating individual clinical expertise with the best available external clinical evidence from systematic research."

Forgive me, but the evidence on this topic which is presently held in the database is not useful, nor is it applicable. As first a clinician and then an academic, I am totally committed to lthe principle of learning from the evidence and acting within its teachings - provided it has validity and relevance to current practice. I see little of either in that which has been brought to our attention.

I try primarily to satisfy the needs of my client. The whole business is supposed to be client centred - is it not? With other clinicians I am still trying to discover what works and what doesn't. When I make such discovery it will then be written up, peer reviewed and published for the guidance of clinicians who will follow. If someone else gets there first I will be only too pleased to apply the proven regimen to ensure best efficacy for my client. At this time, in this specific topic, the evidence probably has less value to me than many years of clinical experience.

Evidence based medicine -what it is and what it isn't BMJ 312 (7023), 13th January, pp 71-72.

Here is what can happen if you use the wrong dose:

Frostbite following use of a commercially available cryotherapy device for the removal of viral warts.
Sammut SJ, Brackley PT, Duncan C, Kelly M, Raraty C, Graham K.
Dermatol Online J. 2008 Jun 15;14(6):9.

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This is a real problem and one I have seen a growing number of people with. Going slightly off topic, but I have seen and treated people who have believed, or been told by their GP/other health professional/bloke down the pub, they have a VP and so have gone out and bought one of these home freezing kits. After 3 or 4 unsuccessful attempts at treating them themselves they have come in to see me. On examination they present with little more than a corn but now with a large lesion/wound around it.

I believe these kits should not be available to buy and possibly only be on prescription to minimise the amount of damage some people are doing to themselves.

The optimal dosage and the effect of the sclerotomy sites' cryotherapy on the development of FVIG were not clear