An Analysis Using Modified Rapid Ultrasound for Shock and Hypotension for Patients with Endogenous Cardiac Arrest.

AIMS: We prospectively investigated whether or not a rapid ultrasound for shock and hypotension (RUSH) examination is useful for managing patients with endogenous cardiac arrest (CA). SETTINGS AND
DESIGN: A prospective medical chart review in a single hospital.
MATERIALS AND METHODS: From March 2016 to December 2017, we performed a modified RUSH for all patients with out-of-hospital endogenous CA. We investigated the frequency of positive findings on modified RUSH and what kind of diseases could most easily be pinpointed as the cause of CA by the modified RUSH.
RESULTS: During the investigation period, 194 participants were enrolled in the present study. They were primarily male, with an average age of 68.8-year-old, and 178/194 (91.7%) died as outpatients. The most frequent cause of CA was cardiogenic, followed by aortic disease, respiratory failure, and stroke except for unknown. There were 14/26 (54%) aortic disease patients who showed positive RUSH findings. Among cases of the aortic disease, only aortic dissections had positive findings. Aside from aortic disease, there were no cases of positive findings of the modified RUSH among the remaining diseases, and all patients with positive findings died. Only pulseless electrical activity (PEA) was a statistically significant factor for positive findings of the modified RUSH in cases of the aortic disease.
CONCLUSIONS: The present study revealed that, among patients with out-of-hospital endogenous CA, modified RUSH is useful for diagnosing ascending aortic dissection for the detection of hemothorax and/or cardiac tamponade, especially with PEA.

INTRODUCTION

Ultrasound studies for investigating shock are considered to be important and have recently become essential in Emergency Departments worldwide. The rapid ultrasound for shock and hypotension (RUSH) examination is a study protocol employed to evaluate the patients with shock. The RUSH examination assesses three key physiologic points, coequally expressed as the pump, tank, and pipes.[123] This examination assesses the heart and lungs as a pump; the lungs, inferior vena cava, and abdominal compartment (specifically the volume status) as the tank; and the aorta and femoral veins as the pipes.[123] The target of the RUSH is to diagnose the origin of shock. Possible causes include cardiac dysfunction, pneumothorax, intra-abdominal hemorrhaging, abdominal aortic aneurysm, hypovolemia, and pulmonary embolism.[123] Cardiac arrest (CA) is thought to be an advanced type of shock.

Accordingly, we prospectively investigated whether or not RUSH was useful for managing patients with endogenous CA.

MATERIALS AND METHODS

This prospective study protocol was approved by the review board of Juntendo Shizuoka Hospital (approval number: UMIN000021292). The Department of Acute Critical Care Medicine is located in Shizuoka, a 552-bed hospital of Juntendo University in the Izu Peninsula in Shizuoka Prefecture (near Tokyo). There are two acute critical care centers in Eastern Shizuoka that accommodate critical ill patients, such as those with CA, unstable circulation, unconsciousness, acute coronary syndrome, stroke, severe wound trauma, severe burns, or poisoning. One of the acute critical care centers is ours, and the other is Numazu City Hospital; as Numazu City Hospital lacks emergency physicians, our hospital often sends staff members to provide help. Our hospital also has helicopter landing pads for the emergency medical system utilizing physician-staffed emergency helicopters in Eastern Shizuoka Prefecture and serves a population of approximately 1.2 million.

From March 2016 to December 2017, we performed modified RUSH for all patients with out-of-hospital endogenous CA who were treated by thei department staff. In our department, computed tomography (CT) and biochemical analysis of the blood are routinely performed, if a patient is not in the terminal stage of cancer, or informed consent cannot be obtained to perform the necessary examinations from the family.[45] We performed CT after resuscitation when resuscitation failed to obtain spontaneous circulation but before the declaration of death, or after obtaining stable circulation by resuscitation, as the Japanese tend to request CT imaging rather than an autopsy for determining the cause of death.[6] The exclusion criteria for the present study included patients who experienced cardiopulmonary arrest in the hospital, patients with exogenous CA (trauma, hanging, suffocation, or poisoning), and those who did not undergo a CT examination and blood test.

Modified RUSH included checking for the signs of cardiac tamponade, dissection of the ascending aorta, D-shaped deformity of the cardiac ventricles, and fluid collection of the thoracic and abdominal cavity. We did not include evaluations of cardiac hypokinesis and flattening of inferior vena cava, as this finding did not specify the diagnosis of CA. We also did not examine the loss of sliding sign, as this finding rarely indicates endogenous CA.[45] Modified RUSH was performed via a subxiphoid approach during chest compression and via a parasternal approach during pulse check within 10 s every 2 min.

In this study, clinical diagnoses were made as follows: (1) For cardiogenic arrest, no specific findings on radiological or biochemical tests with the existence of preceding chest pain or dyspnea, and/or ST elevation on strip electrocardiogram (ECG), and/or confirmation of ventricular fibrillation or tachycardia, and/or a history of acute coronary syndrome, chronic heart failure, or cardiomyopathy; (2) For stroke, the confirmation of cerebrovascular injury on CT; (3) For aortic disease, the confirmation of aortic disease on CT; (4) For bowel bleeding, the confirmation of hematemesis and/or melena or bloody stool; (5) For chronic renal failure, the confirmation of increased levels of blood urea nitrogen, creatinine, and potassium with regular hemodialysis; (6) For respiratory failure, the confirmation of lung lesions on CT and an increase in inflammatory reactions on blood tests with or without chronic obstructive lung disease; (7) For sepsis, positive inflammatory reactions on blood tests with an undetermined septic focus on CT; (8) For cerebral degeneration, CA in the patient with Parkinson's disease or Parkinson syndrome without specific fatal diseases; (9) For others, when the cause of CA is specified but not mentioned above, and (10) For unknown, when the cause of CA is unknown after the evaluations which were usually classified into cardiogenic CA based on the Utstein-style.

We investigated the sex, age, duration of chest compression from the start to hospital arrival, clinical diagnoses of CA, final outcome (dead or survival), frequency of positive findings of the modified RUSH for each disease, and what kind of diseases could most easily be pinpointed as the cause of CA by modified RUSH among the participants. In addition, we investigated what factors were associated with positive findings of modified RUSH and compared the findings of the modified RUSH and CT. Both the Chi-squared test and the nonpaired Student's t- test were used for the statistical analyses. A value of P < 0.05 was considered to be statistically significant.

RESULTS

During the investigation period, 3152 patients were treated as outpatients by the staff of the department. Among them, there were 334 cases of the CA. After excluding 126 cases of exogenous CA, 208 cases with endogenous CA remained. After excluding 10 cases of terminal-stage malignancy and four cases whose family did not permit the evaluation and the treatment of CA, the 194 remaining participants were enrolled in the present study.

The background characteristics of the participants and causes of CA are summarized in Table 1. They were primarily male, with an average age of 68.8-year-old, and 178/194 (91.7%) died as outpatients. The most frequent cause of CA was cardiogenic, followed by aortic disease, respiratory failure, and stroke except for unknown. Table 2 shows the number of cases with positive findings by modified RUSH for each cause of CA. There were 14/26 (54%) aortic disease patients who showed positive RUSH findings. Among the cases of the aortic disease, only aortic dissections had positive findings. In contrast, there was one false-positive D-shaped pattern in a case of sepsis due to acute cor pulmonale without pulmonary embolism. Aside from aortic and septic disease, there were no cases of positive findings of modified RUSH among the remaining diseases. This difference was statistically significant (P< 0.0001). All the participants who had positive findings on modified RUSH died.

Table 1

Background characteristics of participants

Variable	Data
Sex (n)
Female	70
Male	138
Age (years)
Range	0-96
Average	68.8
Dead as outpatients	178
Chest compression on arrival (min)	30.8±12.7
Classification
Cardiogenic arrest	75
Acute coronary syndrome	65
Chronic heart failure	7
Arrhythmia	4
Aortic disease	26
Dissection	23
Rupture of an abdominal aneurysm	1
Aorta-pulmonary fistula	2
Respiratory failure	19
Pneumonia	10
Chronic respiratory failure	8
Alveolar hemorrhaging	1
Stroke	11
Subarachnoid hemorrhaging	9
Intracerebral hemorrhaging	2
Chronic renal failure	7
Cerebral degeneration	4
Sepsis	4
Bowel bleeding	4
Other	3
Alcohol ketoacidosis	1
Laryngeal edema	1
Anaphylaxis	1
Unknown	41
Total	194

Table 2

Results of the ultrasound

	Positive	Negative
Cardiogenic arrest	0	75
Aortic disease	15	11
Respiratory failure	0	19
Stroke	0	11
Chronic renal failure	0	7
Cerebral degeneration	0	4
Sepsis	1	3
Bowel bleeding	0	4
Other	0	3
Unknown	0	41

Table 3 shows all data of participants who had the aortic disease, and Table 4 shows the results of analyses concerning the relationship between positive findings of modified RUSH and the background characteristics of the aortic disease patients. The classifications of ECG in Tables 3 and 4 were determined by the results of ECG strip during resuscitation. Only pulseless electrical activity (PEA) was a statistically significant factor for positive findings of modified RUSH in cases of aortic disease. Ascending aortic dissection tended to be a factor for positive findings of modified RUSH in cases of aortic disease but was not significant.

Table 3

All data of subjects who had the aortic disease

Sex	Age	Classification	Ultrasound	Details of findings	Electrocardiogram	Computed tomographic findings
						Tamponade	Ascending	Hemothorax
Male	73	Dissection	Positive	Tamponade, hemothorax	Asystole	Positive	Positive	Positive
Male	94	Dissection	Positive	Tamponade, ascending		Positive	Positive	Positive
Female	94	Dissection	Negative		PEA	Negative	Negative	Negative
Female	77	Dissection	Positive	Hemothorax	PEA	Negative	Positive	Positive
Male	83	Dissection	Negative		PEA	Positive	Positive	Negative
Male	58	Dissection	Negative		Asystole	Positive	Positive	Positive
Female	86	Dissection	Positive	Tamponade, hemothorax	PEA	Positive	Positive	Positive
Male	13	Dissection	Positive	Tamponade, ascending	PEA	Positive	Positive	Negative
Female	85	Dissection	Positive	Tamponade, ascending	PEA	Positive	Positive	Negative
Female	89	Dissection	Negative		Asystole	Positive	Positive	Negative
Male	57	Dissection	Positive	Tamponade	PEA	Positive	Positive	Negative
Female	79	Dissection	Positive	Tamponade	Asystole	Positive	Positive	Negative
Female	83	Dissection	Negative		Asystole	Positive	Positive	Negative
Female	78	Dissection	Positive	Tamponade, ascending	PEA	Positive	Positive	Positive
Female	80	Dissection	Positive	Tamponade	PEA	Positive	Positive	Negative
Female	79	Dissection	Positive	Ascending	PEA	Positive	Positive	Negative
Female	75	Dissection	Negative		PEA	Positive	Positive	Negative
Male	76	Dissection	Positive	Ascending	PEA	Positive	Positive	Negative
Female	80	Dissection	Positive	Tamponade, ascending	PEA	Positive	Positive	Negative
Female	96	Dissection	Positive	Tamponade, ascending	PEA	Positive	Positive	Negative
Female	81	Dissection	Negative		Asystole	Positive	Positive	Negative
Female	54	Dissection	Positive	Tamponade, hemothorax	PEA	Positive	Positive	Positive
Male	84	An abdominal aneurysm	Negative		PEA	Negative	Negative	Negative
Male	90	AP fistula	Negative		Asystole	Negative	Negative	Negative
Male	75	AP fistula	Negative		Asystole	Negative	Negative	Negative

PEA: Pulseless electrical activity, AP: Aortopulmonary

Table 4

Results of analysis concerning the relationship between positive findings of modified rapid ultrasound for shock and hypotension and the background characteristics of patients with aortic disease

	Ultrasound positive (n=15)	Ultrasound negative (n=7)	P
Sex (male/female)	5/10	2/5	NS
Age
PEA (yes/no)	13/2	3/4	<0.05
Duration from chest compression to arrival (min)	30.5±10.7	34.3±13.5	NS
CT findings
Tamponade (yes/no)	14/1	6/1	NS
Ascending (yes/no)	15/0	6/1	0.1
Hemothorax (yes/no)	6/9	1/6	NS
Dead as an outpatient	15	7	NS

CT: Computed tomography, PEA: Pulseless electrical activity, NS: Not significant

Table 5 shows the relationship between the CT and modified RUSH findings in cases of aortic disease. Hemothorax and tamponade were relatively frequently found by the modified RUSH. Assuming that the CT diagnosis was correct, the sensitivity and specificity of modified RUSH were 55% and 100% for cardiac tamponade, 38% and 100% for ascending aortic dissection, and 62% and 100% for hemothorax, respectively.

Table 5

Relationship between computed tomography and modified rapid ultrasound for shock and hypotension findings in patients with aortic disease

CT findings	Correct of ultrasound	Error of ultrasound	P
Tamponade (yes/no)	11/2	9/0	0.08
Ascending (yes/no)	8/1	13/0	NS
Hemothorax (yes/no)	4/15	3/0	=0.001

CT: Computed tomography, NS: Not significant

DISCUSSION

This is the first report to demonstrate that, in patients with out-of-hospital endogenous CA, the modified RUSH is useful for diagnosing ascending aortic dissection for the detection of hemothorax and/or cardiac tamponade, especially in the cases of PEA.

We noted aortic dissection in 11.8% of patients in the present study, which seems to be a relatively large number of dissections for out-of-hospital CAs. In America, the annual incidence of the ruptured aortic aneurysm was 7.89/1 million in 2016.[7] In Japan, a survey by the Ministry of Health, Labour and Welfare showed the percentage of aortic disease among the causes of death in Japan to be 1.3% in 2015, ranking 9th from the top (malignancy was top, followed by heart disease, pneumonia, cerebrovascular disease, senility, accident, renal failure, suicide, and aortic disease). As the Japanese data were not based on an autopsy, the cases of aortic disease might have been included in the study among those who died of senility. However, our hospital mainly treated the patients with acute critical illness, and patients with terminal diseases, including malignancy, or chronic diseases, such as chronic obstructive lung disease or renal failure, were mainly managed at local medical facilities. In addition, we excluded the patients with exogenous diseases or in the terminal stage of malignancy, and hence the percentage of aortic disease might have been increased compared with the general population. These selection biases increased the proportion of aortic disease in the present study.

Among endogenous CA diseases, ascending aortic dissection tended to be easily detected by the modified RUSH. This might be because there were several indirect signs, such as tamponade and hemothorax-induced by an aortic dissection, that were relatively easy to detect by ultrasound.[8910] In contrast, major endogenous CA diseases, such as acute coronary syndrome, could not be directly found by the modified RUSH. This might be because whole cardiac ischemia progresses during the CA phase, resulting in hypokinesis or akinesis of the ventricular motion, even though the initial onset is not markedly different from the acute coronary syndrome. In addition, our protocol excluded the hypokinesis of ventricular motion, which might have influenced our results.

In the present study, the sensitivity for hemothorax and cardiac tamponade was higher than that for ascending aortic dissection. Two possible reasons may explain this. The first is the observation time. A left parasternal view was required to evaluate the dissection of the ascending aorta. However, this view was limited during the pulse check phase to within 10 s every 2 min during resuscitation. In contrast, cardiac tamponade and hemothorax could be confirmed via other views during the chest compression. This flexibility may have contributed to the difference in the sensitivity. The second possible reason was deformity of the ascending aorta. In severe aortic dissection, the aortic contour can be changed due to intra-wall thrombus [Figure 1]. In such a situation, it was difficult to determine which feature was the ascending aorta by ultrasound. If the examiner could not identify the ascending aorta, it was impossible to determine ascending aortic dissection. These two reasons may explain the less frequent detection of direct signs of ascending aortic dissection using ultrasound.

Figure 1

Deformity of the ascending aorta. The true lumen of the ascending aorta became collapsed due to intra-wall thrombus and massive hemorrhaging

However, not even hemothorax and tamponade showed high-sensitivity for detection using ultrasound in this study.[910] This might be because hemopericardium or hemothorax was observed in high-echoic areas in comparison with effusion on ultrasound. A high-echoic mass or layer is difficult to differentiate from the pericardial fat or ventricular wall itself, as these two structures are also high-echoic layers on ultrasound [Figure 2].[11121314] After separating the clot and serum, the serum tended to present as a low-echoic area similar to effusion [Figure 3]. The presence of a high-echoic clot or hematoma may have reduced the sensitivity of ultrasound for detecting the cardiac tamponade. In addition, the subtle movement of the ventricle can help detect hemopericardium, allowing ascending aortic dissection to easily be detected under conditions of PEA.[15]

Figure 2

A case of hemopericardium.[6] Ultrasonography shows hemopericardium as a high-echoic area. It is difficult to identify hemopericardium when cardiac movement is absent

Figure 3

The separation between the clot (arrow) and serum (*) on computed tomography. After separating the clot and serum, the serum tends to present as a low-echoic area, resembling effusion

In the present study, we showed that advanced cardiac life support with modified RUSH did not improve the outcome. Indeed, all participants with aortic dissection detected by the modified RUSH in this study ultimately died. Chardoli et al. also reported that although bedside ultrasound was able to identify some reversible causes of PEA, there were no significant changes in the survival outcome between the ultrasound group and those treated with traditional cardiopulmonary resuscitation.[16] However, there have been reports of survival outcomes being obtained even when patients with aortic dissection entered CA.[1718] These cases underwent urgent open cardiac massage with resolution of cardiac tamponade by pericardial fenestration. Accordingly, more aggressive treatments for patients with ascending aortic dissection may result in a favorable outcome in the future.

Limitations

The present study is associated with several limitations, including the small number of positive findings in patients without an autopsy study. Future studies involving a larger number of patients are, therefore, needed to further examine this issue.

CONCLUSIONS

The present study shown that, among the patients with out-of-hospital endogenous CA, the modified RUSH is useful for diagnosing the ascending aortic dissection for the detection of hemothorax and/or cardiac tamponade, especially with PEA. However, its sensitivity is not very high, and it did not contribute to obtaining a survival outcome.

Financial support and sponsorship

This work received funds from Pfizer and the Ministry of Education, Culture, Sports, Science and Technology (MEXT)-Supported Program for the Strategic Research Foundation at Private Universities, 2015-2019. Title is (the constitution of total researching system for comprehensive disaster, medical management, corresponding to wide-scale disaster).

Conflicts of interest

There are no conflicts of interest.