Surgical Airway : Cricothyroidotomy [Archive]

Sacamuelas

07-08-2004, 09:13

"The essential indication for a surgical airway is the need for an airway.

However, the usual first preference is for orotrachael intubation. (Nasotrachael intubation is slower and should be attempted only if the patient is haemodynamically stable and can be hand ventilated for long enough to obtain optimum pre-oxygenation). The hard collar may be temporarily removed if the neck is protected by in-line immobilisation. A Surgical Airway should be performed if orotrachael intubation is unsuccessful.

Situations in which a Surgical Airway should be considered as the primary method include Major Maxillo-Facialary Injury (eg compound mandibular fractures, Le Forte III Midface Fracture), Oral Burns, Fractured Larynx.

The simplest technique is needle cricothyroidotomy. This involves placing a 12 Gauge Cannula into the trachea via the cricothyroid membrane. This will allow adequate ventilation for up to 45 minutes, hypercapnea being the main limiting factor. This may buy enough time to obtain expert airway assistance and attend to other emergency procedures. (NB This is the prefered technique for children under the age of 12.)

Formal Crycothyroidotomy is the classic surgical airway. It is safer and quicker then attempting Formal Tracheostomy in the Emergency Room. The patients cervical spine is immobilised in the neutral position. A Right Handed Surgeon stands on the patient's right. The area is preped and draped. Local anaesthetic with adrenaline is used only in the conscious patient who has a patent airway. In an asphyxiated / dying patient there is insufficient time.

The thyroid cartilage is stabilised with the left hand as the right hand makes the incision. The first incision is 3cm long transverse incision through the skin overlying the crycothyroid membrane (closer to the crycoid cartilage then then the thyroid cartilage). The second pass of the scalpel is again transverse, through the crycothyroid membrane into the airway. With the scalpel blade protruding into the airway, it is rotated 90 degrees so that it is now longitudinal, holding the two edges of the incised membrane apart.

The left hand now releases the thyroid cartilage and picks up an artery forcep. The artery forcep is placed into the airway, through the exposed gap, and opened so as to take over from the scalpel as the means of holding the incised edges apart. The scalpel can now be removed and placed in the sharps tray. The right hand then picks up the endotracheal tube or tracheostomy tube and inserts it into the airway, directed towards the chest. The best size ET tube for an adult cricothyroidotomy is a size 6.0.

After confirming adequate position, the tube should be secured and suctioned. A definitive airway will be required as soon as the patient is stable, fully assessed and appropriate interventions have been performed.

Fortunately, with skilled airway doctors in most trauma centres, surgical airways are rarely required."

Sacamuelas

07-08-2004, 10:22

basic anatomy for landmarks

Roguish Lawyer

07-08-2004, 10:43

Oh fine, do this one while Crip is totally occupied. I see how you are. :rolleyes: LOL

Sacamuelas

07-08-2004, 10:44

It's a tribute!! ;) LOL

ccrn

07-08-2004, 11:07

I dont have anything to add to this other than it shouldnt be used as a substitute for good airway management skills.

Many EMS systems have banned cric prehospital at all.

It is good for true upper airway obstruction when ETT or double lumen tube (ie Combitube) cannot be used.

I think all EMT-P and airway qualified providers should have more time in the OR intubating, say a certain amount of hours per year rather than a refresher every two years-

ccrn

steel71

07-08-2004, 12:51

Hum, let's try some of my calls ( this is the training everybody should go through) lol
call #1, 500 lb ,male pt found supine on the bathroom floor with coffee ground emesis coming out if the pt's mouth and rectum, unk down time, weak radial pulse, it's only you and your emt partner( with 1 week of experience)
call # 2, 10 yr old female was playing soccer , syncope while playing, pulseless, apneic,crowd of 300 people on the feild, yelling at you to do something, oh yeah it's only you and your partner.
call # 3, 1 yr old male, parents found the pt at the bottom of their pool, pt was out of their site for 45/60 sec, you find the pt on the pool deck, with a pulse but apneic, oh, mom has been yelling at you since the 1st sec you got on scene, her husband tries to restrain her, but she slaps him and starts screaming in you ear while you try to intubate her child.
I think it' s the environment your in that test your skills, not the procedure. The OR was the place I learned how to intubate during paramedic school, cool temp and great lighting, perfect environment, stable pt, hey it doesn't get any better then this! But, those days are long gone, and I don't think I'm going to learn anything by doing EET in an OR,ER setting.

rogerabn

07-08-2004, 18:36

Having worked prehospital I can certainly relate to the stress of the crisis situation that you work in. Intrubating patients under duress can be challenging to say the least.
But one can never get enough experince intubating patients. The nice thing about refreshing your skills in the OR, is that you can take your time. Really identify the anatomical landmarks. and increase confidence levels. More often than not most of the paramedics that rotate though my OR miss intially, possivbly due to the stress of being observed, and working in an "alien" setting. I have yet to have any paramedic student or experinced provicer "bag" every intubation we allow them to attempt. Even we who practice intubation on a daily basis, tube the goose once in awhile. Over confidence is killer in airway management, the more experince the better.

ccrn

07-08-2004, 21:54

**RESULTS: Of 108 patients intubated in the prehospital setting, the ETT was found to be misplaced on assessment in the ED in 25% of cases (esophageal placement, 17%; hypopharyngeal placement, 8%). Fifty-six percent of the patients with esophageal ETTs and 33% of those with hypopharyngeal ETTs died in the ED. The rate of ETT misplacement was 37% in trauma patients compared with 14% in medical patients (p<0.01). Failure to detect ETCO2 on patient arrival at the ED was noted in all but one of the patients with esophageal ETTs (the one exception was a patient who was breathing spontaneously upon arrival), and in four of nine with hypopharyngeal ETTs, as well as 17% of the patients with correctly placed ETTS (all of whom were asystolic with no return of spontaneous circulation).

CONCLUSIONS: The alarmingly high rate of unrecognized ETT misplacement in the prehospital setting within this EMS system suggests a need for an evaluation of the scope of this problem in other communities. **

This is just one of many studies I found on a search. I wont even go into details of my own experiences working in ER recieving intubated pts from EMS.

This is not to say I do not respect them because I do, in fact I admire them.

But to say one would NOT benefit from continuing education under controlled environments from higher providers is remiss in my opinion.

My apologies for going off topic-

ccrn

Doc T

07-08-2004, 22:14

few comments...

Nasotracheal intubations are quick and do not require hemodynamic stability...the only requirement in a breathing patient. That said, it is not the first choice of airway due to the risk of sinusitis and risk of necrosis if left for a prolonged period.

As for surgical crics...well, any EMS system that allows RSI needs to teach their prehospital people to perform crics... We have had a few performed in our system that went well, but it is not always that way. It is not a procedure that is performed often in any ER and takes practice to be fast like anything else.

I typically make a longitudinal incision, not transverse as there are anterior jugular veins that tend to get cut in a transverse incision and bleeding just makes the airway more difficult. It usually takes more than two passes of the scapel as the people winding up with surgical airways rarely have long skinny necks. Four or five passes is more typical. And I have never seen anyone use a needle cric except in a child...it is a terrible airway.

doc t.

Doc T

07-08-2004, 22:20

Originally posted by ccrn
**RESULTS: Of 108 patients intubated in the prehospital setting, the ETT was found to be misplaced on assessment in the ED in 25% of cases (esophageal placement, 17%; hypopharyngeal placement, 8%). Fifty-six percent of the patients with esophageal ETTs and 33% of those with hypopharyngeal ETTs died in the ED. The rate of ETT misplacement was 37% in trauma patients compared with 14% in medical patients (p<0.01). Failure to detect ETCO2 on patient arrival at the ED was noted in all but one of the patients with esophageal ETTs (the one exception was a patient who was breathing spontaneously upon arrival), and in four of nine with hypopharyngeal ETTs, as well as 17% of the patients with correctly placed ETTS (all of whom were asystolic with no return of spontaneous circulation).

CONCLUSIONS: The alarmingly high rate of unrecognized ETT misplacement in the prehospital setting within this EMS system suggests a need for an evaluation of the scope of this problem in other communities. **

This is just one of many studies I found on a search. I wont even go into details of my own experiences working in ER recieving intubated pts from EMS.

This is not to say I do not respect them because I do, in fact I admire them.

But to say one would NOT benefit from continuing education under controlled environments from higher providers is remiss in my opinion.

My apologies for going off topic-

ccrn

\

can you give the citation for this abstract. I am guessing its old...from prior to CO2 detectors placed on most EMS trucks. -+

swatsurgeon

07-08-2004, 22:56

Just to echo doc-T (a fellow trauma surgeon) the cric is usually a last ditch effort...most patients can be managed with BVM and a nasal airway.....that said, if the cric is going to happen don't fall into the trap of abandoning the procedure due to bleeding. I do and teach the vertical incision also....the anterior jugular veins are 1) always present, 2) always distended unless the patient lost a lot of blood and 3) have a 30-40% incidence of being in the wrong place. All that you'll cut with the vertical incision is the bridging anterior jugular and that typically is small and the cric apparatus usually compresses it. That being said the #1 reason people abandon the cric once initiated is BLEEDING. Remember that A comes before B or C.....I know, I'm preaching to the choir on this one but if you start it, finish it...isn't that one of your motto's anyway? (I hope that wasn't in bad taste!!!)
I have a saying....no one dies without an airway...believe it, live it.
T-2

ccrn

07-08-2004, 23:59

http://www.paracademy.com/events/abst_june01.htm

This study was conducted in '97 and submitted in '01. There are many more but I chose this one as it more closely resembles my own experience and challenges the results of most other studies claiming only 1-5% undetected esophageal intubation. Further searching did reveal that most studies including recent ones achieved results this study challenged.

My search results show end tidal co2 detectors including colorimetric as far back as '92 aboard EMS with one OR study as far back as '88-

ccrn

Sacamuelas

07-09-2004, 09:48

Originally posted by Doc T
I typically make a longitudinal incision, not transverse as there are anterior jugular veins that tend to get cut in a transverse incision and bleeding just makes the airway more difficult. It usually takes more than two passes of the scapel as the people winding up with surgical airways rarely have long skinny necks. Four or five passes is more typical. And I have never seen anyone use a needle cric except in a child...it is a terrible airway.
doc t.

Thank you very much Ma'am- Also thanks to SwatSurgeon for both of your comments. :cool:

Let me refocus this a little since it seems it has taken a civilan EMS slant. This is for a review for SF medics and early basci education for the potentials. The likelyhood of them facing oral maxillo-facial trauma and/or severe burns is a distinct possibility. That is why this thread was started. I think everyone will stipulate that ALL medical personnel should get as much personal experience in standard ETT placement as they can. The more the better- I agree completely with Rogerabn. It isn't only EMT's that place bad placed airways, I have seen MD's, RNA's, and RN's do it too- oh yeah, DMD's too :o. LOL

Back on point, based on the incision technique recommendations of our resident trauma surgeons, I will post a pic of the anterior triangle of the neck for all viewing this thread that don't have familiarity of the anatomy. Thanks again Doc t and SS.

Sacamuelas

07-09-2004, 09:57

Follow-up question for Doc T or SS-

WHen making your vertical(longitudinal) initial incision, what length of an incision do you make? I realize that you would make it larger for access/visibility if needed, but what is your initial cut length?

swatsurgeon

07-09-2004, 15:41

I make it 2 cm...... never be reluctant to make it as long as necessary. It usually gets extended when we convert to a tracheostomy. Incision size never hurt anyone...better a big scar and breathing patient than a cosmetic scar and no airway....besides you guys wear your scars proudly!!

Doc T

07-09-2004, 16:06

Originally posted by Sacamuelas
The likelyhood of them facing oral maxillo-facial trauma and/or severe burns is a distinct possibility. That is why this thread was started.

in both cases an orotracheal intubation would STILL be your first line...if unable then a surgical airway would be a possibility. You don't mean to imply that this is the first choice?

Doc T

07-09-2004, 16:08

Originally posted by ccrn
http://www.paracademy.com/events/abst_june01.htm

This study was conducted in '97 and submitted in '01. There are many more but I chose this one as it more closely resembles my own experience and challenges the results of most other studies claiming only 1-5% undetected esophageal intubation. Further searching did reveal that most studies including recent ones achieved results this study challenged.

My search results show end tidal co2 detectors including colorimetric as far back as '92 aboard EMS with one OR study as far back as '88-

ccrn

but they were not mainstain until much more recently. A few EMS units may have had them in '97 but certainly not the majority.

Sacamuelas

07-09-2004, 19:30

Originally posted by Doc T
in both cases an orotracheal intubation would STILL be your first line...if unable then a surgical airway would be a possibility.
Correct. That was definitely not my intention. Thanks for clarifying a possible misunderstanding. As stated earlier ma'am. :cool:
Originally posted by Sacamuelas
However, the usual first preference is for orotrachael intubation.... A Surgical Airway should be performed if orotrachael intubation is unsuccessful.

Otherwise, my AprofSoldier username would be 'surgicalcric' right? Oops, sorry James- and he is not even here to defend himself. HAHA

Gypsy

07-09-2004, 20:44

Originally posted by Sacamuelas

Otherwise, my AprofSoldier username would be 'surgicalcric' right? Oops, sorry James- and he is not even here to defend himself. HAHA

No but I shared it with him, he told me to tell you he got a kick out of your tribute. ;)

ccrn

07-10-2004, 00:38

Originally posted by Doc T
but they were not mainstain until much more recently. A few EMS units may have had them in '97 but certainly not the majority.

I am told by the EMT-P personel here in my very rural Midwestern region that they have been using colorimetric detectors for about ten years.

Doc T

07-10-2004, 08:10

Originally posted by ccrn
I am told by the EMT-P personel here in my very rural Midwestern region that they have been using colorimetric detectors for about ten years.

if that is the case what is their excuse for such a high rate of esophageal intubations? It should have been recognized and treated prior to arrival to an ER.

In my experience in all places I have been I would guess about a 1-2% rate of esophageal intubations and mostly in patients arriving in arrest.

doc t.

ccrn

07-10-2004, 08:19

The study I presented was conducted in Orlando Florida not the Midwest nor by the EMS system that serves the area I live in.

As this is Sacamuelas' thread regarding cricothyrotomy this is the last I will mention it unless you wish to start another thread regarding oral intubation or in PM-

ccrn

Doc T

07-10-2004, 09:08

Originally posted by ccrn
[url]

This study was conducted in '97 and submitted in '01. There are many more but I chose this one as it more closely resembles my own experience and challenges the results of most other studies claiming only 1-5% undetected esophageal intubation. ccrn

the above quote by you seems to indicate that the EMS system in your area has similar results to the study (regardless of the fact that it was from Orlando)...namely a high yield of esophageal intubations as found in the study. I do not believe Saca will mind if we continue on...

I am curious how your EMS system is rectifying the problem. Are the EMS providers having to go through additional training?

ccrn

07-10-2004, 09:32

Originally posted by Doc T
I do not believe Saca will mind if we continue on...

The EMT-P I spoke with on the phone yesterday stated their successful intubatiuon rate closer mirrored other study results of 95-99%. He states that they are required to do four intubations per year to remain qualified. If they do not get them in the field they go to the OR.

My own experience is subjective (I worked localy for one year in ED/ICU) as I have not participated in any studies of local EMS RSI, however I would disagree with his claim.

The fact that the Orlando study and the EMS system in my area are seperated by both time and geography might support that other EMS sytems could be experiencing similar results as the study claims. Idependent research would be the only way to confirm this. Apparently most providers are not motivated to find out.

It is not my EMS system other than the fact that I live here. They are doing nothing to add to intubation training at this time according to them. I got the feeling from speaking to them that they would appreciate it if they did. If I was director in charge of that program I would probably want to rotate my people through a program in a large city just as many of the small rural hospitals here do with their nursing staff.

A call to an air-ground service in the large metropolitan area where I work reveals 120 hours adult and pediatric OR time initialy, then 4 hours a year with an MD doing ETT, LMA, and cric on sheep. They feel this is adequate as long as a candidate gets the entire initial training-

ccrn out

Sacamuelas

07-10-2004, 16:01

Originally posted by Doc T
I do not believe Saca will mind if we continue on...
LOL.... I think I just got the civilian trauma surgeon equivalent of the "Team Sergeant Stare"!! hahaha

I have been overruled, play ball. LOL But I reserve the right to still ask questions about technique and managing complications of the procedure even after Doc T proves that ccrn is the ONLY person in his area or this country it seems to believe that the EMT's are incompetant at ETT. LOL

Doc T

07-10-2004, 16:24

Originally posted by Sacamuelas
But I reserve the right to still ask questions about technique and managing complications of the procedure

you can ask away...

as for complications...they are few.

Bleeding as I mentioned above which is a horrendous thing because it makes the procedure much more difficult

incision too deep in the excitement and you can go through the back wall of the trachea and give an esophageal injury.

complications are very rare though....

doc t.

NousDefionsDoc

07-10-2004, 16:25

By allah Saca, I'm impressed. Excellent thread, posts and training aids. Outstanding. Here's your Senior Medic's Smiley Face for your class - :D

The way I was taught to do it is lift the skin, cut and blunt dissect with forceps. Make entrance with the forceps, not a blade and open the forceps to make way for the hose. I think there is less chance of cutting the aforementioned veins this way.

Aspiring medics - anatomy is important.

swatsurgeon - the "abandon because of bleeding" - I don't get this. I find it incredible that anyone trained would make an incision, then not go on to establish an airway for any reason.

NousDefionsDoc

07-10-2004, 16:29

incision too deep in the excitement and you can go through the back wall of the trachea and give an esophageal injury.

I almost invariably see new guys be too hesitant about cutting. How is it with surgeon wannabes?

ccrn

07-10-2004, 16:57

Originally posted by Sacamuelas
...after Doc T proves that ccrn is the ONLY person in his area or this country it seems to believe that the EMT's are incompetant at ETT. LOL

I never meant to give this impression. I believe EMT-P's are second only to anesthesiologists and CRNA's with the acception of one pulmonologist in California I know who can intubate faster and smoother than anyone Ive ever seen.

My intent was that even they as well as any other provider can only benifit from continuing education. Perhaps I stressed that too strongly for some.

As far as "abondoned because of bleeding" Ive seen new residents do this and have to have the fellow or attending take over-

Doc T

07-10-2004, 18:42

Originally posted by NousDefionsDoc
I almost invariably see new guys be too hesitant about cutting. How is it with surgeon wannabes?

most of our residents have gotten to do a few crics... and they get alot of experiences with tracheostomies so are usually comfortable by the time it happens. It is not a junior level procedure (crics...trachs are) because typically airway is a big problem by the time we move onto a cric...

so the surgeon wannabe is typically a 3-5 year resident...

I personally have never seen an esophageal injury from a cric... have seen bleeding from all sorts of things including the anterior jugulars...

doc t.

Doc T

07-10-2004, 22:51

Originally posted by NousDefionsDoc

swatsurgeon - the "abandon because of bleeding" - I don't get this. I find it incredible that anyone trained would make an incision, then not go on to establish an airway for any reason.

i think the point was don't try to control the bleeding until after the airway is obtained. You would be amazed at how people stop cutting and start clamping not recognizing in the flurry that seconds and minutes are passing while the patient has no airway. As surgeons we tend to control bleeding as we go so it goes against the natural instinct if that makes sense.

doc t.

NousDefionsDoc

07-11-2004, 07:46

As surgeons we tend to control bleeding as we go so it goes against the natural instinct if that makes sense.

Roger. Thank you.

NousDefionsDoc

07-11-2004, 15:22

Check this out (http://www.chinookmed.com/detail.php?product_id=000497&limit_start=10)

swatsurgeon

07-12-2004, 06:48

that is a re-newed version of the old puncture cric kit. Doc-T hit it...the bleeding issue makes someone question the procedure....OMG! Am I in the wrong place, did I cut something REALLY bad.....just keep going and finish the airway. The pressure from the tube or tape or securing device will ususally tamponade the bleeding. It's very low pressure bleeding1-3 mmHg and will stop by raising their head. As faras abandoning the procedure, thattypically wouldn't happen in the field for SF (or similiar) care but happens with EMS and even Emergency Medicine docs. I have been called STAT 4-6 times a year for a "failed" cric which turned out to be due to significant bleeding with the procedure.
I have spoken to many a combat medic that when the face is burned, frag'ed, the tongue is lacerated, etc, the cric is the 1st step, not the last for an airway. I'm going to attach 2 pictures, 1 is an explosion in the mouth (M-80) but could be something seen in the field and the second is a massive blunt trauma to the face...how would you approach the airway??

swatsurgeon

07-12-2004, 06:53

here are the 2 pics...first blunt trauma, second explosion

swatsurgeon

07-12-2004, 06:54

oops...the previous one was the explosion....now for blunt

swatsurgeon

07-12-2004, 06:56

the impotant message for the field is 1) never lean them back, they'll drown and 2) CRIC!!!!!!!. Never needed lidocaine for either of them and they were both wide awake.

Sacamuelas

07-12-2004, 08:23

Good pics... and great advice, Thanks Doc. Another oral/maxillofacial trauma case, here is a case done by one of my good buddies/old classmate of mine last year. Standard ETT would be "difficult".:p

rakkasan187

07-13-2004, 22:24

Here is a decent vid of a cricothyroidotomy as well as some other procedures.....

CLICK HERE (http://www.biodigital.org/voz2/slide2.htm)

The procedure shown uses the horizontal incision. I was taught the vertical as mentioned earlier. Another interesting thing is the cutter uses the tracheal hook inferior to the incision versus superiorly. I really like using the hook and Trousseau Dialator. It makes the procedure much easier but obviously we should train to do it with field expedient tools. BTW I have never done one for real...only on the pig trachs and mannekin...

rak

18C/GS 0602

07-19-2004, 12:07

This article came out in Academic Emergency Medicine this June. In the discussion section they talk about a study by Katz et al 2001 done in Orlando (the same one that ccrn cited) that showed a miss rate of 25%. A follow up to the Katz study by the same authors showed a decrease in miss rates from 25% to 9% after the implementation of protocols that required ET CO2 detection devices. They also showed that in a subset of paramedics that had 100% compliance with the ET CO2 monitoring they had a 0% miss rate.

Emergency Physician–Verified Out-of-hospital Intubation: Miss Rates by Paramedics
James H. Jones, MD, Michael P. Murphy, MD, Robert L. Dickson, MD, Geoff G. Somerville, BS, EMT-P and Edward J. Brizendine, MS

-ABSTRACT

Objectives: To prospectively quantify the number of unrecognized missed out-of-hospital intubations by ground paramedics using emergency physician verification as the criterion standard for verification of endotracheal tube placement. Methods:The authors performed an observational, prospective study of consecutive intubated patients arriving by ground emergency medical services to two urban teaching hospitals. Endotracheal tube placement was verified by emergency physicians and evaluated by using a combination of direct visualization, esophageal detector device (EDD), colorimetric end-tidal carbon dioxide (ETCO2), and physical examination. Results: During the six-month study period, 208 out-of-hospital intubations by ground paramedics were enrolled, which included 160 (76.9%) medical patients and 48 (23.1%) trauma patients. A total of 12 (5.8%) endotracheal tubes were incorrectly placed outside the trachea. This comprised ten (6.3%) medical patients and two (4.2%) trauma patients. Of the 12 misplaced endotracheal tubes, a verification device (ETCO2 or EDD) was used in three cases (25%) and not used in nine cases (75%). Conclusions: The rate of unrecognized, misplaced out-of-hospital intubations in this urban, midwestern setting was 5.8%. This is more consistent with results of prior out-of-hospital studies that used field verification and is discordant with the only other study to exclusively use emergency physician verification performed on arrival to the emergency department.

crash

10-20-2007, 07:42

Surgical airway (cricothyroidotomy). -Trained use only. An emergency cric set can be fashioned by cutting an IV drip chamber in half. Find the anatomical landmark of cricothyroid membrane below "adam's apple." Make a longitudinal incision through the skin and visualize the membrane. Take top half of cut IV drip chamber, remove cap on spike that usually goes into IV bag. Insert spike through cricothyroid membrane. If patient needed a surgical airway, there will be a rush of air. The drip chamber needs to be secured in place with 100 mph tape or tac sutures. An ambu-bag can be attached to the drip chamber and the patient ventilated.

Found this on the net, I've never heard of this method, seems ok in theory, not sure if you could move enough air through the spike on a IV drip chamber.:confused:

Anyone heard of this method before?

update: tested this a little at work today, the drip chamber does not fit a bvm, its a litle bigger, but cutting a slit in the side and over lapping it will fit, with minimal leakage.
Now breathing normally you cannot move enough air through the spike of the drip chamber, but with a BVM you can put enough air in, exhalation however, not so much. So if the pt's upper airway was not completely occluded and the pt could exhale; it could work.
I was breathing through it for about 5 mins inhaling through the spike and BVM exhaling out my nose.(not cric'ed of course)

Roguish Lawyer

10-20-2007, 08:50