Precordial Thump - For Asystole?

In The Precordial Thump, Adam Thompson, EMT-P writes about an article^[1] by Dr. Keith Wesley in JEMS. Dr. Wesley was reviewing a study of the use of precordial thump (PT is the abbreviation used in the study, but since PT is commonly used for other medical terminology, I prefer to write it out) as the initial therapy for all cardiac arrest not yet treated by EMS. As with much in EMS, the answers are not abundant, but there is a lot that is interesting.


Here is the way the study worked:

This study was part of a larger epidemiological investigation of OOH-CA , conducted between March 2004 and November 2005. The study protocol pertinent to PT was as follows: all patients in CA (confirmed according to the 2000 ILCOR guidelines) for whom it was decided to attempt CPR were regarded as qualifying for this study. After placing defibrillation pads on the victim, a pre-cordial chest thump was delivered, regardless of the presenting rhythm. All EMS personnel was trained in Advanced Life Support, but did not receive specific training or instructions on how to perform PT, to obtain data pertinent to the typical ‘real-life’ conditions. Whenever any other resuscitative manoeuvre preceded PT, the protocol was considered violated, and the case was not included in the PT study cohort (see Table 1 for detail).^[2]

CA = Cardiac Arrest
OOH-CA = Out-Of-Hospital - Cardiac Arrest (as opposed to in hospital CA)
ILCOR = International Liaison Committee on Cardiopulmonary Resuscitation
CPR = CardioPulmonary Resuscitation

Whenever any other resuscitative manoeuvre preceded PT, the protocol was considered violated, and the case was not included in the PT study cohort.

This is important in understanding all of the data. Unless EMS showed up and thumped the patient before doing anything else, the patient was placed in the other or no thump category. They could have thumped the patient dozens of times, but if they did not deliver one thump immediately after confirming cardiac arrest the patient was not considered to have been thumped. This is not necessarily a bad way to divide the treatment groups, but where is the information on these cases? Did they not happen at all? I can't tell from the information provided. The researchers should include enough patients to allow for these protocol deviations. They should also prospectively describe the various subgroup analyses that will look at the various ways the patients will be treated. I cannot find these in the paper.

This study does show that the intention-to-treat analysis of data is more than a little misleading. Intention-to-treat analysis of data is looking at what the study protocol indicated for treating the patient, rather than looking at the actual treatment the patient received. Just having to mention this in a study shows a significant problem persuading participants to follow the protocol. Had they used intention-to-treat analysis, they could have claimed 100% use of precordial thump as the initial EMS treatment. The actual compliance was 40%. There was no use of intention-to-treat analysis in this study, but it was used in the Gausche pediatric intubation study.^[3]

All EMS personnel was trained in Advanced Life Support, but did not receive specific training or instructions on how to perform PT, to obtain data pertinent to the typical ‘real-life’ conditions.

It is true that many paramedic programs will not provide any specific instruction on performance of the precordial thump, even though it may be in the paramedic scope of practice where the school is located. This foolishness should not be used to justify shortcuts in the protocol design. Some training is essential. If the precordial thump is found to be very effective in treatment of cardiac arrest, then you can expect a lot more attention will be paid to instruction of precordial thump. How do we know what was being done by the medics in the study? There is no standard precordial thump being delivered. The precordial thump, in this study, is whatever you think a precordial thump should be.

This is not controlling for variables, but introducing variables. Good research is about controlling for as many variables as possible. In this area, good research may not have a lot to do with the real world, but it does have to do with finding out what may work. If precordial thump is found to be worthy of further study, then more consideration of real world limitations conditions ought to be addressed.

What are the participants doing, when they are thumping? If you are familiar with the instruction of CPR, and you have seen CPR certified health care professional performing what they believe to be CPR, then you know that some of the simplest things can be open to interpretation. What are the participants doing, when they are thumping? I suspect that they received written instructions on how a precordial thump should be delivered. How literate are the paramedics? How well written are the written instructions? Do those writing the written instructions understand what a precordial thump should be? Should a precordial thump be delivered in the way that most people thump patients?

This study raises a lot of questions, but is too small and uncontrolled to answer them. Still, it is interesting, otherwise so many people would not be writing about it. This study was done according to the 2000 guidelines, so we should expect that the numbers discharged neurologically intact would be much higher now, even with the prolonged response times.

Table 1.
Summary of population characteristics of victims treated according to the study protocol by pre-cordial thump (PT) [Thump] before any other resuscitatory intervention, compared to the sub-cohort excluded for protocol violation (non-PT) [No Thump]. Data is presented as patient numbers and percentage of total. VF/VT: ventricular fibrillation/tachycardia (VT observed in one PT and no non-PT cohort case); PEA: pulseless electrical activity, time: mean delay between emergency medical support contact call and first intervention by emergency medical service (EMS) personnel (in brackets: minute-bin of 25th and 75th quartile); EMS-witnessed: EMS-witnessed cardiac arrest; ROSC: return of spontaneous circulation; discharge: discharged alive from hospital.^[2]

Here is the information from Table 1. I could not get the html to work, so this should at least keep the information organized:

Thump: 144 patients

No Thump: 219 patients


Thump: 74 (51%) Male

No Thump: 131 (60%) Male


Thump: 73 ± 16 Years Old

No Thump: 69 ± 19 Years Old


Thump: 24 (17%) VF/VT

No Thump: 42 (19%) VF/VT


Thump: 42 (29%) PEA

No Thump: 59 (27%) PEA


Thump: 78 (54%) Asystole

No Thump: 118 (54%) Asystole


Thump: 9:48 minutes response - (6/12) 25%/75% Quartiles

No Thump: 9:24 minutes response - (5/11) 25%/75% Quartiles


Thump: 11 (8%) EMS Witnessed

No Thump: 19 (9%) EMS Witnessed


Thump: 21 (15%) Bystander CPR

No Thump: 55 (25%)* Bystander CPR


Thump: 31 (21.5%) ROSC

No Thump: 43 (19.6%) ROSC


Thump: 8 (5.6%) Discharged Alive

No Thump: 14 (6.4%) Discharged Alive

* Significant difference between PT [Thump] and non-PT [No Thump] cohort (p < 0.05).^[4]


Let's look at some of the ways that small numbers can lead to data that encourage misrepresentation.

The cardiac arrests witnessed by EMS:

The success rate of PT for ROSC was as high as 27.3% (3 of 11; Table 2), highlighting the need for early application of PT. Overall survival among EMS-witnessed CA victims was 36.4% (4 of 11); one half of these were cardioverted by PT.^[2]

Treatment of 11 patients with witnessed cardiac arrest does not give a large enough sample to draw any conclusions other than this is interesting and deserves more study. By more study, I mean a much larger study. In this study, only 40% of patients were treated according to the study design. So, we should anticipate that about two thirds of patients attempted to be enrolled will be excluded, just by those on scene not delivering a precordial thump first. 144 cardiac arrest patients is not a lot of patients for any kind of study of response to treatment. There are parts of New York City, that would have each medic responding to more than 144 cardiac arrests in a year. While the intent of the researchers is good, the numbers do not support any interpretation of effect on survival.

The results include a paragraph each on six patients with changes in rhythm after precordial thump. 2 of these patients were discharged neurologically intact. 2/144 ≠ an acceptable outcome. Not even if your average response time is almost 10 minutes (mean time to precordial thump was 9:48).

Then there are the survival numbers. 22 survivors to hospital discharge. 8 of these survivors are in the thump group. A paragraph each on 6 patients who had changes in rhythm immediately after precordial thump. Only 2 of those 6 patients survived to hospital discharge. There are 6 patients resuscitated, with apparently good outcome, who are only mentioned in passing. What does this mean? I suspect that it means that these patients were initially treated with a thump, but did not have a rhythm change right after the thump, then they received conventional treatment and had ROSC after the conventional treatment was begun.

Were the patients unresponsive to precordial thump not treated the same as if they had not received a precordial thump? This does not appear to be that much different from the double standard that the acupuncture researchers applied, however unintentionally, in the studies I wrote about in Eureka - Conventional Treatment Plus Placebo Beats Conventional Treatment Alone. Precordial thump is proposed as a complementary treatment - not an alternative treatment.

Some patients received precordial thump, but did not respond immediately after the thump, then may have responded after other treatment. These patients do not get enough discussion. Did 20% of the thumped patients have ROSC by other means? Did they survive to discharge? Did the thump cause any change in response to treatment?

Statistically, shouldn't there have been other ROSC patients surviving to discharge?

Given the sample size, the rate of ROSC, and the survival to discharge rate, there are not enough patients in the sample to answer that question. They state that this is a part of a larger study, so maybe there will be publication of data on a much larger group of precordial thump patients.

Among patients who were discharged from hospital alive, PT was the original cause of ROSC in two of eight cases. Patients in whom ROSC was caused by non-PT interventions had a survival rate of 21.4% (6 of 28), compared to 2/3 among those in whom ROSC occurred upon PT.^[2]

Reading the full study does not answer these questions. I will repeat what I stated at the beginning. This study raises a lot of questions, but is too small and uncontrolled to answer them.


Here is everything the Pennsylvania ALS protocols have on precordial thump use.

4. Precordial thump may be used when ALS personnel witness VF arrest in a monitored patient.^[5], ^[6]

Precordial thump is in the protocols, but not in the scope of practice? Are medics in Pennsylvania trained in this? How do you QA/QI/CYA something like this?


Finally, what do the ACLS guidelines have to say about precordial thump?

Precordial Thump for VF or Pulseless VT
There are no prospective studies that evaluated the use of precordial (chest) thump. In 3 case series (LOE 5),104–106 VF or pulseless VT was converted to a perfusing rhythm by a precordial thump. In contrast, other case series documented deterioration in cardiac rhythm, such as rate acceleration of VT, conversion of VT to VF, or development of complete heart block or asystole following the use of the thump (LOE 5105,107–111; LOE 6112).

The precordial thump is not recommended for BLS providers. In light of the limited evidence in support of its efficacy and reports of potential harm, no recommendation can be made for or against its use by ACLS providers (Class Indeterminate).^[7]

While they do not mention asystole, the results of the studies published since these guidelines were published suggest that the biggest change should be adding asystole to the list of things for which no recommendation can be made for or against its use by ACLS providers (Class Indeterminate).

Reading the full study does not answer questions. I will repeat what I stated at the beginning. This study raises a lot of questions, but is too small and uncontrolled to answer them. Interesting. Not useless, but really only useful in encouraging more research and suggesting that some of what we believed about precordial thump (only for VF/VT - not for asystole) is wrong.


Footnotes:

^ ¹ To Thump, Or Not To Thump
JEMS.com
Keith Wesley, MD, FACEP
Street Science
2009 May 11
Article


^ ² Utility of pre-cordial thump for treatment of out of hospital cardiac arrest: A prospective study
Pellis T, Kette F, Lovisa D, Franceschino E, Magagnin L, Mercante WP, Kohl P.
Resuscitation. 2009 Jan;80(1):17-23. Epub 2008 Nov 17.
PMID: 19010581 [PubMed - indexed for MEDLINE]


^ ³ Effect of out-of-hospital pediatric endotracheal intubation on survival and neurological outcome: a controlled clinical trial.
Gausche M, Lewis RJ, Stratton SJ, Haynes BE, Gunter CS, Goodrich SM, Poore PD, McCollough MD, Henderson DP, Pratt FD, Seidel JS.
JAMA. 2000 Feb 9;283(6):783-90. Erratum in: JAMA 2000 Jun 28;283(24):3204.
PMID: 10683058 [PubMed - indexed for MEDLINE]]
Free Full Text . . . . Free PDF


^ ⁴ Utility of pre-cordial thump for treatment of out of hospital cardiac arrest: A prospective study
The tables is my pathetic recreation of one table from the study. I have changed the wording that I felt was not clear, or that lost some context separated from the rest of the study.
Same as Footnote [2]


^ ⁵ Ventricular Fibrillation / Pulseless VT
Pennsylvania Adult Statewide ALS Protocol
Note # 4
23/121 enter 23 in the page count window.
Nov. 2008 posting of PA ALS Protocols


^ ⁶ Prehospital Practitioner Scope of Practice
PA Bulletin
[38 Pa.B. 6565]
[Saturday, November 29, 2008]
I would point to a particular part where it isn't, but that is the point. It isn't there, anywhere. Pennsylvania can be very strict in punishing violations of scope of practice, yet here they seem to encourage it.
Nov. 2008 posting of PA Scope of Practice


^ ⁷ Precordial Thump for VF or Pulseless VT
2005 American Heart Association Guidelines for Cardiopulmonary Resuscitation and Emergency Cardiovascular Care
Part 7.2: Management of Cardiac Arrest
Interventions Not Supported by Outcome Evidence
Free Full Text . . . . Free PDF page 8/10


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