a b s t r a c t

Background: The success of Closed Chest Cardiopulmonary Resuscitation (CC-CPR) degrades with prolonged times. Open Chest CPR (OC-CPR) is an alternative that may lead to superior coronary and cerebral perfusion. It is critical to determine when continued CC-CPR is unlikely to be successful to justify initiating OC-CPR as Rescue therapy. The purpose of this study is to review CC-CPR outcomes to define a time threshold for attempting OC-CPR. Methods: We identified all adult non-trauma patients diagnosed with cardiac arrest, ventricular fibrillation, ventric- ular tachycardia and asystole from 1/1/10-12/31/14. We collected demographics, cardiac rhythm, resuscitation du- ration, survival to hospital discharge and neurological outcome. Using time to ROSC after ED arrival and good neurological outcome, we explored varioUS times as triggers for attempting OC-CPR.

Results: Among 242 cases of CPR, 205 cases were out-of-hospital cardiac arrest (OHCA). Mean age was 63.7 (+-16.9),woman comprised 29.8% (72/242), and median prehospital CPR time was 30 min (20-44). Patients suffer- ing ED arrest had improved ROSC (54.1% vs. 12.7%, pb 0.001) and survival to hospital discharge rates (37.8% vs. 2.9%, pb 0.001) compared to OHCA. Patients achieving ROSC had median total CPR duration of 18 minutes (10 minutes of pre-hospital CPR) compared with patients without ROSC who had 45 minutes (30 pre-hospital) respectively. No pa- tient receiving N 10 minutes of CPR in the ED survived to hospital discharge.

Conclusion: In patients suffering OHCA and requiring CC-CPR in the ED, overall survival rate to good neurologic func- tion is low. OC-CPR could potentially be attempted after 10 minutes of CC-CPR in the ED.

(C) 2016

Introduction

Cardiac arrest is a common Public health problem and a leading cause of death in developed nations. Approximately 37 adults have out-of-hospital cardiac arrest (OHCA) per hour in the United States [1]. Closed-chest cardiopulmonary resuscitation (CC-CPR) with ad- vanced cardiac life support has been the standard method of resuscita- tion since 1960. Despite initial reports of high survival rates, currently, the survival rate of CC-CPR is only 6.7% [1].

Before widespread adoption of CC-CPR, however, open-chest cardio- pulmonary resuscitation (OC-CPR), the act of compressing the heart di- rectly between the hands via thoracotomy or sternotomy, was the prevailing method of Cardiac resuscitation [2]. When performed expedi- tiously by an experienced surgeon, OC-CPR can be beneficial [3], but widespread application is limited by lack of training and concerns about unnecessary invasive procedures. After its initial description in

? Support: None.

* Corresponding author at: 165 Cambridge St #810, Boston, MA 02114.

E-mail address: [email protected] (D.D. Yeh).

1960, CC-CPR became widely adopted because it could be performed by anyone (including laypersons) and does not require surgical instru- ments [4]. However, CC-CPR has not been adequately compared to OC-CPR in a rigorous manner, and it is possible that, in appropriately se- lected patients, OC-CPR can lead to superior outcomes.

Given the risks of this procedure, the patients most likely to benefit are those who will not be successfully resuscitated with CC-CPR. To best define this population, we performed a retrospective study of patients receiving CC-CPR at our hospital to determine a time threshold beyond which continuing CC-CPR is likely futile (Probability of survival b 1%).

Methods

Study design and setting

This retrospective study was approved by our local institutional re- view board. The study institution is an urban academic level 1 trauma center hospital. The emergency department (ED) records more than 100 000 visits annually. Using International Classification of Diseases, Ninth Revision, codes (427.1, 427.41, 427.42, 427.5), we screened all

http://dx.doi.org/10.1016/j.ajem.2016.05.060

0735-6757/(C) 2016

Table 1 Demographics and outcomes
	All (n = 242)	Prehospital CPR (n = 205)	Arrested in ED (n = 37)	P
Age	63 (IQR, 53-77)	63 (IQR, 52-78)	63 (IQR, 59-75)	.55
Female	72 (29.8%)	60 (29.3%)	12 (32.4%)	.70
initial cardiac rhythm				b.0001
Shockable	55 (22.7%)	47 (22.9%)	8 (21.6%)
VF	42 (17.4%)	38 (18.5%)	4 (10.8%)
VT	8 (3.3%)	4 (2%)	4 (10.8%)
Nonshockable	187 (77.3%)	158 (77.1%)	29 (78.4%)
PEA	89 (36.8%)	63 (30.7%)	26 (70.3%)
Asystole	93 (38.4%)	90 (43.9%)	3 (8.1%)
ROSC	46 (19%)	26 (12.7%)	20 (54.1%)	b.0001
ICU LOS (d)a	2.5 (IQR, 1-6)	1 (IQR, 1-5)	3 (IQR, 1-8)	.37
Hospital LOS (d)a	4 (IQR, 1-12)	1 (IQR, 1-6)	5 (IQR, 4-20)	.032
24-h survival	29 (12%)	12 (5.9%)	17 (45.9%)	b.0001
Survival to hospital discharge	20 (8.3%)	6 (2.9%)	14 (37.8%)	b.0001
Good neurologic outcome	20 (8.3%)	6 (2.9%)	14 (37.8%)	b.0001

Abbreviation: ICU, intensive care unit; LOS, length of stay.

^a Limited only to those patients with ROSC.

adult patients (age >= 18 years old) diagnosed with cardiac arrest, Ven- tricular fibrillation , Ventricular tachycardia , or asystole from January 1, 2010, to December 31, 2014. We excluded trauma patients and patients with known prestated limitations of life-sustaining treat- ments (ie, do-not-resuscitate orders).

Data collection

Data collected included patient demographics, cardiac rhythm, re- suscitation duration, survival to hospital discharge, and neurologic out- comes. Shockable rhythm was defined as VF and VT, and all other rhythms were defined as a nonshockable rhythm. Initiation of cardio- pulmonary resuscitation (CPR) was defined as the initiation of chest compressions by a professional rescuer, and duration of CPR was calcu- lated until return of spontaneous circulation (ROSC) or termination of Resuscitative efforts. The ability to follow commands was used to define a good neurologic outcome.

Statistical analysis

Normally distributed variables are presented as mean (SD), whereas nonnormally distributed data are presented as median (interquartile ranges [IQRs]). Comparisons were performed using 2-sample t tests or Wilcoxon rank sum tests as appropriate. Categorical data are presented as frequency and percentage and compared using ?² tests. A 2-sided P value of less than .05 was considered statistically significant.

Results

During the 5-year study period, 869 patients were treated in our institution’s ED for cardiac arrest, VF, VT, or asystole. After exclusion of

pediatric and trauma patients, the final cohort comprised 242 cases. De- mographic characteristics, initial cardiac rhythm, and outcomes of the cohort are summarized in Table 1. Of the 242 patients, 205 (85%) had OHCA and received prehospital CPR for a median duration of 30 minutes (20-44 minutes); overall, 46 (19%) of 242 achieved ROSC. However,

only 29 (12%) of 242 survived for 24 hours, and 20 (8.3%) of 242 sur- vived to hospital discharge. All 20 patients surviving to hospital dis- charge had good neurologic outcomes.

Age and sex were not significantly different when comparing pa- tients with OHCA to those with witnessed arrest in the ED, nor were the relative frequencies of shockable vs nonshockable initial cardiac rhythm. In both groups, most patients had initially nonshockable cardi- ac rhythm. However, patients with OHCA had a significantly higher in- cidence of asystole and lower incidence of Pulseless electrical activity . Patients with witnessed arrest in the ED had significantly higher rates of ROSC (54.1% vs 12.7%; P b .001), 24-hour survival rate (45.9% vs 5.9%; P b .001), survival to hospital discharge rate (37.8% vs 2.9%;

P b .001), and good neurologic outcome (37.8% vs 2.9%; P b .001) when compared to those receiving prehospital CPR.

Prehospital CPR

Table 2 summarizes the demographics, CPR duration, and initial car- diac rhythm for only those patients with OHCA. We excluded cases with unknown CPR duration and were left with 177 remaining subjects. Pa- tients who achieved ROSC had a median time of 10 minutes of prehospital CPR and 18 minutes of total CPR duration. Patients without ROSC had significantly longer prehospital CPR duration (median, 35 vs 10 minutes), ED CPR duration (median, 10 vs 6 minutes), and total CPR duration (median, 47 vs 18 minutes), and asystole accounted for nearly half of all Initial cardiac rhythms.

Table 2

Out-of-hospital cardiac arrest only limited to those with prehospital CPR duration available

	All (n = 177)	ROSC (n = 22)	No ROSC (n = 155)	P
Age	62 (50-77)	58 (IQR, 50-63)	64 (50-78)	.18
Female	49 (27.7%)	7 (31.8%)	42 (27.3%)	.64
Prehospital CPR duration (min)	30 (20-44)	10 (IQR, 4-30)	35 (IQR, 25-45)	b.0001
ED-CPR duration (min)	10 (5-16)	6 (IQR, 3-10)	10 (IQR, 6-16)	.03
Total CPR duration (min) Initial cardiac rhythm Shockable	45 (36-55) 39 (22%)	18 (IQR, 8-44) 6 (27.3%)	47 (IQR, 37-57) 33 (21.3%)	b.0001 .007
VF	33 (18.6%)	4 (18.2%)	29 (18.7%)
VT	2 (1.1%)	1 (4.5%)	1 (0.6%)
Nonshockable	138 (78%)	16 (72.7%)	122 (78.7%)
PEA	57 (32.2%)	11 (50%)	46 (29.7%)
Asystole	77 (43.5%)	3 (13.6%)	74 (47.7%)

Includes only subjects with known duration of prehospital CPR.

CPR = cardiopulmonary resuscitation; ED = Emergency Departmen;tROSC = return of spontaneous circulation

Fig. 1. Out-of-hospital cardiac arrest and ED CPR duration.

Among the OHCA patients, the percentage achieved ROSC, the per- centage of patients with survival to hospital discharge, and good neuro- logic outcomes decreased with increasing duration of ED CPR (Fig. 1). No OHCA patient receiving prehospital CPR and who then underwent CPR in the ED for more than 10 minutes had a good neurologic outcome (0/99; 95% confidence interval, 0%-3.7%). Likewise, among patients with witnessed arrest in the ED, the cumulative percentage for achieving ROSC or survival to hospital discharge and good neurologic outcomes had minimal increase after 10 minutes of ED CPR (Fig. 2). No patient

requiring CPR for more than 10 minutes of CPR (total CPR duration = ED CPR duration) survived to hospital discharge with a good neurologic outcome (0/19; 95% confidence interval, 0%-17.7%).

Discussion

In this retrospective review of patients receiving CC-CPR in the ED of an urban academic hospital, we report that overall, ROSC was achieved in 19%, but the rate of survival to hospital discharge with a good

CPR = cardiopulmonary resuscitation; ED = Emergency Department; ROSC = return of spontaneous circulation

Fig. 2. Witnessed ED arrest and total (ED) CPR duration.

neurologic outcome was only 8.3%. Not surprisingly, ED witnessed ar- rests had significantly better rates of ROSC (54.1%) and survival to hos- pital discharge with good neurologic outcome (37.8%), a finding consistent with other reports. For example, Brooks et al reported a sur- vival to hospital discharge rate in OHCA of 8.3%, whereas Kayser et al re- ported patients with witnessed arrest in the ED had a 22.2% rate of survival to hospital discharge [5,6]. Goldberger et al [7] also reported that 49% of Inhospital CArdiac arrest patients had ROSC, with 15% overall survival to hospital discharge. Recognizing that ROSC alone is not an ad- equate patient-centered outcome, we chose to consider survival to hos- pital discharge with good neurologic outcome as a meaningful end point. Using this metric and reviewing 5 years’ worth of outcomes, we can define 10 minutes of CPR in the ED as the limit of futility for continu- ing ongoing resuscitative efforts with standard closed-chest compres- sions. A recent study by Grunau et al [8] have also attempted to address the question of how long to persist with resuscitation efforts. In a post hoc analysis of the Resuscitation Outcomes Consortium data- base, the investigators examined outcomes according to the initial rhythm (shockable or nonshockable) taking into consideration the time to ROSC. In their cohort of 1617 patients with OHCA, nearly half (49%) achieved ROSC (the remainder were not transported to the hospi- tal), but only 10% had a neurologically favorable outcome. Time to ROSC was independently associated with the probability of survival and good neurologic outcome. It is worth emphasizing that Grunau et al [8] counted total CPR time, including prehospital CPR time. For both shock- able and nonshockable initial rhythms, the percentage of patients sur- viving with good neurologic outcome was less than 1% at 34 minutes into the resuscitation. However, the median time to ROSC was approx- imately 15 minutes for all patients; for those patients who achieved a fa- vorable neurologic outcome, median time to ROSC was 8 and 6 minutes for shockable and nonshockable, respectively. In their study, only 82 (5.1%) arrived in the ED without previously achieving ROSC. Those au- thors conclude that resuscitation efforts should continue up to 48 mi- nutes of total CPR time, especially for younger patients with initial Shockable rhythms. Our study, by definition, enrolled only patients ar- riving in the ED with CPR ongoing after a median of 30 minutes of prehospital CPR. We found that those patients who achieved ROSC in the ED did so after a median of 6 minutes of ED CPR, and the longest du- ration of ED CPR time for a Favorable neurologic outcome was 10 mi- nutes. Our total CPR time, thus, is very similar to the limit of futility reported by Grunau et al.

Cardiopulmonary resuscitation is associated with high rates of surviv- Extracorporeal life support“>al if several conditions are met: (1) favorable etiology (eg, VF vs asystole) [9], (2) early initiation of chest compressions by medical professionals (as in witnessed arrests in the ED) or bystanders, and (3) high-quality resus- citation efforts [10-12]. Outside of this confluence of factors, meaningful outcomes after CPR are dismal, usually approximately 5% [13]. Although etiology and early initiation are beyond the control of the ED physician, high-quality cardiac compressions are a potentially modifiable factor. The principal purpose of cardiac compression is to maintain adequate cor- onary and cerebral perfusion, as higher pressures are associated with higher likelihood of ROSC and good neurologic outcome, respectively. It is commonly believed that external compressions maintain cardiac out- put by directly compressing the heart between the sternum and the spine. However, studies have discounted this theory, and it is now accept- ed that the forward flow of blood is a result of the recoil of the thoracic cavity, with the heart acting as a passive conduit [14-18]. This results in, at best, a cardiac output of only 25% to 33% of normal cardiac output and oxygen delivery. There is, however, a way to drastically improve car- diac output by restoring the heart pump function: resuscitative thoracot- omy with direct cardiac massage, aka OC-CPR.

Open-chest CPR

Animal studies of medical cardiac arrest have shown that OC-CPR re- sults in higher cardiac output, dramatic improvements in coronary

perfusion pressure and cerebral blood flow, and higher rates of ROSC when compared to CC-CPR [2,19-25]. In 1 randomized study, cardiac ar- rest was induced by potassium chloride injection, and dogs were ran- domized to receive either CC-CPR or OC-CPR after 5 minutes of nonintervention. All subjects receiving OC-CPR were successfully resus- citated and behaviorally normal at 72 hours. In contrast, only 43% of dogs receiving CC-CPR survived, and most survivors had incapacitating neurologic deficits [26]. Another study in dogs demonstrated that OC- CPR was an effective “rescue” technique after CC-CPR was unable to achieve adequate coronary perfusion pressures after 15 minutes. Eighty percent of subjects receiving OC-CPR survived, compared to none in the continued CC-CPR group [27]. However, time to initiation of OC-CPR is a critical factor. Sanders et al demonstrated that 75% of animals were re- suscitated when OC-CPR was initiated within 15 minutes. If the proce- dure was delayed to 20 minutes, ROSC rates dropped to 40% [28,29]. This intervention should be ideally initiated within 20 to 25 minutes of cardiac arrest to be successful [23], although there have been case re- ports of successful resuscitation (with good neurologic outcome) after up to 75 minutes of unsuccessful CC-CPR [30].

Human studies of OC-CPR are sparse yet encouraging [31,32]. In 1 study, Boczar et al [33] performed OC-CPR a median 45 minutes of un- successful standard CC-CPR for nontraumatic OHCA. It is interesting to note that 30% of patients achieved ROSC with OC-CPR, despite being previously declared unsalvageable. It must be stressed that the purpose of this exploratory study was not to assess clinical efficacy, but rather to measure hemodynamic parameters in a human model. The lack of long- term survival after ROSC in this pilot study was likely due to the prolonged delay before initiating OC-CPR. In a Japanese case series of 33 patients receiving OC-CPR for OHCA after unsuccessful CC-CPR (me- dian, 25 minutes) [34], ROSC was achieved in 13 (39%) of 33, a signifi- cantly higher rate than the 12.7% we reported for OHCA in our series. No Wound infections were noted, and there was only 1 case of iatrogenic heart damage, which was subsequently successfully repaired. Another case series from Japan reported that 15 (58%) of 26 of patients receiving OC-CPR for OHCA achieved ROSC, with the likelihood of success highest among those undergoing thoracotomy within 5 minutes of hospital arriv- al. Overall, 12% were discharged alive, compared to 1% of contemporane- ous patients receiving standard CC-CPR [35]. Acceptability of OC-CPR by laypersons and surviving family members is high, with nearly 80% uncon- ditionally agreeing with the use of OC-CPR [36]. However, at this time, no strong recommendations can be made regarding the routine use of OC- CPR due to the lack of evidence of benefit or harm [37].

Extracorporeal life support

Another invasive option which may be considered in select institu- tions is Extracorporeal life support , which encompasses both ex- tracorporeal membrane oxygenation and cardiopulmonary bypass [37]. Although there are no randomized trials comparing ECLS to continuing CC-CPR, small case series and single-center observational studies have reported encouraging results [38,39]. A recently published meta- analysis combined 14 publications (2008-2014) describing the use of ECLS in both inhospital and OHCA patients and concluded that overall survival and neurologic seemed to be improved at 3 to 6 months in ECLS patients, although the benefits for OHCA patients were less robust [40]. As with OC-CPR, the American Heart Association acknowledges that there is insufficient evidence to recommend routine use of ECLS in cardiac arrest patients, although it may be considered, if readily avail- able, in select circumstances [37].

Limitations

Our study has several limitations. First, this was a retrospective med- ical record review, and therefore, we were unable to record important data points such as whether the OHCA was witnessed and whether by- standers initiated CC-CPR. Second, we were unable to assess the quality

(depth and rate) of chest compressions or the adherence of the overall resuscitation with advanced cardiac life support best practices. Third, we acknowledge that therapeutic hypothermia was not performed in the 6 OHCA patients surviving more than 24 hours. However, all 6 pa- tients were discharged with a good neurologic outcome, and therefore, we do not feel that addition of therapeutic hypothermia would have al- tered our findings (according to our definition of good neurologic out- come) or conclusions regarding the limitations of CC-CPR.

Although the median prehospital CPR time was 30 minutes overall, no patient receiving greater than 10 minutes of CPR in the ED survived to hospital discharge. These data suggest that alternative rescue options such as OC-CPR should be considered after 10 minutes of CC-CPR in the ED in patients with OHCA.

Conclusion

In our urban, academic ED, the overall rate of survival to hospital dis- charge and survival with good neurologic outcome in patients receiving CPR in the ED is 8.3%. Patients with witnessed arrests have significantly improved outcomes compared to patients suffering OHCA. Given the universally poor survival and neurologic outcomes in patients without ROSC after 10 minutes of CC-CPR in the ED, OC-CPR could potentially be attempted with low risk of unnecessary thoracotomy.

References

1. Go AS, Mozaffarian D, Roger VL, Benjamin EJ, Berry JD, Blaha MJ, et al. Heart disease and stroke statistics-2014 update: a report from the American Heart Association. Circulation 2014;129(3):e28-292.
2. Alifimoff JK. Open versus closed chest cardiac massage in non-traumatic cardiac ar- rest. Resuscitation 1987;15(1):13-21.
3. Briggs BD, Sheldon DB, Beecher HK. Cardiac arrest; study of a thirty-year period of operating room deaths at Massachusetts General Hospital, 1925-1954. JAMA 1956;160(17):1439-44.
4. Kouwenhoven WB, Jude JR, Knickerbocker GG. Closed-chest cardiac massage. JAMA 1960;173:1064-7.
5. Kayser RG, Ornato JP, Peberdy MA. Cardiac arrest in the emergency department: a report from the National Registry of Cardiopulmonary Resuscitation. Resuscitation 2008;78(2):151-60.
6. Brooks SC, Schmicker RH, Rea TD, Aufderheide TP, Davis DP, Morrison LJ, et al. Out- of-hospital cardiac arrest frequency and survival: evidence for temporal variability. Resuscitation 2010;81(2):175-81.
7. Goldberger ZD, Chan PS, Berg RA, Kronick SL, Cooke CR, Lu M, et al. Duration of re- suscitation efforts and survival after in-hospital cardiac arrest: an observational study. Lancet 2012;380(9852):1473-81.
8. Grunau B, Reynolds JC, Scheuermeyer FX, Stenstrom R, Pennington S, Cheung C, et al. Comparing the prognosis of those with initial shockable and Non-shockable rhythms with increasing durations of CPR: informing minimum durations of resuscitation. Resuscitation 2016;101:50-6.
9. Meaney PA, Nadkarni VM, Kern KB, Indik JH, Halperin HR, Berg RA. Rhythms and outcomes of adult in-hospital cardiac arrest. Crit Care Med 2010;38(1):101-8.
10. Soholm H, Hassager C, Lippert F, Winther-Jensen M, Thomsen JH, Friberg H, et al. factors associated with successful resuscitation after out-of-hospital cardiac arrest and temporal trends in survival and comorbidity. Ann Emerg Med 2015;65(5): 523-531.e2.
11. Hasselqvist-Ax I, Riva G, Herlitz J, Rosenqvist M, Hollenberg J, Nordberg P, et al. Early cardiopulmonary resuscitation in out-of-hospital cardiac arrest. N Engl J Med 2015; 372(24):2307-15.
12. Olasveengen TM, Sunde K, Brunborg C, Thowsen J, Steen PA, Wik L. Intravenous drug administration during out-of-hospital cardiac arrest: a randomized trial. JAMA 2009; 302(20):2222-9.
13. Stiell IG, et al. Advanced cardiac life support in out-of-hospital cardiac arrest. N Engl J

    Med 2004;351(7):647-56.

    Cooper JA, Cooper JD, Cooper JM. Cardiopulmonary resuscitation: history, current practice, and future direction. Circulation 2006;114(25):2839-49.

14. Niemann JT, Rosborough JP, Hausknecht M, Garner D, Criley JM. Pressure- synchronized cineangiography during experimental cardiopulmonary resuscitation. Circulation 1981;64(5):985-91.
15. Paradis NA, Martin GB, Goetting MG, Rosenberg JM, Rivers EP, Appleton TJ, et al. Si- multaneous aortic, jugular bulb, and right atrial pressures during cardiopulmonary resuscitation in humans. Insights into mechanisms. Circulation 1989;80(2):361-8.
16. Rich S, Wix HL, Shapiro EP. Clinical assessment of heart chamber size and valve mo- tion during cardiopulmonary resuscitation by two-dimensional echocardiography. Am Heart J 1981;102(3 Pt 1):368-73.
17. Werner JA, Greene HL, Janko CL, Cobb LA. Visualization of cardiac valve motion in man during external chest compression using two-dimensional echocardiography. Implications regarding the mechanism of blood flow. Circulation 1981;63(6): 1417-21.
18. Weiser FM, Adler LN, Kuhn LA. hemodynamic effects of closed and open chest car- diac resuscitation in normal dogs and those with acute myocardial infarction. Am J Cardiol 1962;10:555-61.
19. Jackson RE, Joyce K, Danosi SF, White BC, Vigor D, Hoehner TJ. Blood flow in the ce- rebral cortex during cardiac resuscitation in dogs. Ann Emerg Med 1984;13(9 Pt 1): 657-9.
20. Bircher N, Safar P. Comparison of standard and “new” closed-chest CPR and open- chest CPR in dogs. Crit Care Med 1981;9(5):384-5.
21. Alzaga-Fernandez AG, Varon J. Open-chest cardiopulmonary resuscitation: past, present and future. Resuscitation 2005;64(2):149-56.
22. Sanders AB, Kern KB, Atlas M, Bragg S, Ewy GA. Importance of the duration of inad- equate coronary perfusion pressure on resuscitation from cardiac arrest. J Am Coll Cardiol 1985;6(1):113-8.
23. Sanders AB, Kern KB, Ewy GA, Atlas M, Bailey L. Improved resuscitation from cardiac arrest with open-chest massage. Ann Emerg Med 1984;13(9 Pt 1):672-5.
24. Rubertsson S, Grenvik A, Wiklund L. Blood flow and perfusion pressure during open- chest versus closed-chest cardiopulmonary resuscitation in pigs. Crit Care Med 1995;23(4):715-25.
25. Benson DM, O’Neil B, Kakish E, Erpelding J, Alousi S, Mason R, et al. Open-chest CPR improves survival and neurologic outcome following cardiac arrest. Resuscitation 2005;64(2):209-17.
26. Sanders AB, Ewy GA, Taft TV. Prognostic and therapeutic importance of the aortic dia- stolic pressure in resuscitation from cardiac arrest. Crit Care Med 1984;12(10):871-3.
27. Kornhall DK, Dolven T. Resuscitative thoracotomies and open chest cardiac com- pressions in non-Traumatic cardiac arrest. World J Emerg Surg 2014;9(1):54.
28. Sanders AB, Kern KB, Ewy GA. time limitations for open-chest cardiopulmonary re- suscitation from cardiac arrest. Crit Care Med 1985;13(11):897-8.
29. Shocket E, Rosenblum R. Successful open cardiac massage after 75 minutes of closed massage. JAMA 1967;200(4):333-5.
30. Paradis NA, Martin GB, Rivers EP. Use of open chest cardiopulmonary resuscitation after failure of standard closed chest CPR: illustrative cases. Resuscitation 1992; 24(1):61-71.
31. Calinas-Correia J, Phair I. Physiological variables during open chest cardiopul- monary resuscitation: results from a small series. J Accid Emerg Med 2000; 17(3):201-4.
32. Boczar ME, Howard M, Rivers EP, Martin GB, Horst MH, Lewandrowski C, et al. A technique revisited: hemodynamic comparison of closed- and open-chest cardiac massage during human cardiopulmonary resuscitation. Crit Care Med 1995;23(3): 498-503.
33. Hachimi-Idrissi S, Leeman J, Hubloue Y, Huyghens L, Corne L. Open chest cardiopul- monary resuscitation in out-of-hospital cardiac arrest. Resuscitation 1997;35(2): 151-6.
34. Takino M, Okada Y. The optimum timing of resuscitative thoracotomy for non- traumatic out-of-hospital cardiac arrest. Resuscitation 1993;26(1):69-74.
35. Sakamoto T, Saitoh D, Kaneko N, Kawakami M, Okada Y. Is emergency open chest cardiopulmonary resuscitation accepted by patients’ families? Resuscitation 2000; 47(3):281-6.
36. Cave DM, Gazmuri RJ, Otto CW, Nadkarni VM, Cheng A, Brooks SC, et al. Part 7: CPR techniques and devices: 2010 American Heart Association guidelines for cardiopul- monary resuscitation and emergency cardiovascular care. Circulation 2010;122(18 Suppl. 3):S720-8.
37. Tanno K, Itoh Y, Takeyama Y, Nara S, Mori K, Asai Y. Utstein style study of cardiopul- monary bypass after cardiac arrest. Am J Emerg Med 2008;26(6):649-54.
38. Nagao K, Kikushima K, Watanabe K, Tachibana E, Tominaga Y, Tada K, et al. Early in- duction of hypothermia during cardiac arrest improves neurological outcomes in pa- tients with out-of-hospital cardiac arrest who undergo emergency cardiopulmonary bypass and percutaneous coronary intervention. Circ J 2010;74(1):77-85.
39. Kim SJ, Kim HJ, Lee HY, Ahn HS, Lee SW. Comparing extracorporeal cardiopulmonary resuscitation with conventional cardiopulmonary resuscitation: a meta-analysis. Re- suscitation 2016;103:106-16.