The systematic review protocol was registered with PROSPERO (CRD42023402223). Preferred Reporting Items for Systematic Review and Meta-Analyses (PRISMA) guidelines were used to conduct this systematic review8.
Selection criteria:
The inclusion criteria were as follows: 1) adult patients who presented to the intensive care unit with an undifferentiated shock state, and 2) ultrasound assessment to identify the type of shock. The following studies were excluded: (1) studies that used ultrasound as a diagnostic tool to determine shock outside the ICU. 2) Patients in whom the type of shock had already been determined (shock due to trauma, sepsis, or any known type of shock). 3) Case reports, case series, animal studies, retrospective studies, and review articles were excluded.
Search Strategy:
We searched PubMed, Embase, Scopus, Cochrane Library and Google Scholar. Additional searches included citation tracking of included studies and previous systematic reviews. Databases were searched from their inception to June 2023. The following MeSH terms were used: "Shock" and "Ultrasound" OR "Echocardiography" OR “POCUS” and "Critical care.”
The references of the included studies were assessed, and appropriate review articles were evaluated for further relevant articles. Three reviewers (LK, HE, and BG) independently reviewed the literature and included studies that met the inclusion criteria. Full-text review, quality assessment, and data extraction were independently conducted by LK and HE. The reviewers were not blinded to the authorship, journal, or year of publication. Any disagreement was resolved by a consensus-based discussion, and when required, a third reviewer, BG, adjudicated any disputes. We extracted the study design, location, sample size, characteristics of participants, intervention, reference standards, and outcome measures from the selected articles. Two authors, LK and HE, independently assessed the quality of the studies using the Quadas − 2 tool to identify bias9.
We performed a systematic review and meta-analysis to determine the diagnostic accuracy of ultrasound in intensive care patients with undifferentiated shock.
Statistical analyses:
We divided the studies into 5 separate groups: cardiogenic, hypovolemic, distributive, obstructive, and mixed shock categories. Meta-DiSc® (version 1.4, XI Cochrane Colloquium, Spain) was used for all the statistical analyses. The Spearman correlation coefficient of sensitivity and 1-specificity log were used to estimate heterogeneity due to the threshold effect. Heterogeneity due to nonthreshold effects was estimated using the I2 test. I2 values ≤ 25% were considered to indicate low heterogeneity, 25–50% as moderate heterogeneity, and > 50% as high heterogeneity. In the presence of heterogeneity, a random-effects model was used for further analysis. For each study, we calculated the true positive (TP), false positive (FP), false negative (FN), and true negative (TN) index parameters. The pooled sensitivity, specificity, Negative Likelihood Ratio, and Positive Likelihood Ratio were determined along with 95% CIs. For each parameter, a summary receiver operating characteristic curve (SROC) was generated and the Q value was calculated. The area under the curve (AUC), including the standard error, was computed to assess the diagnostic accuracy of ultrasound in detecting shock types. A test with good discriminating ability has an AUC value close to 1.
Table 1
Author | Year | Design, site and location (country) | No. of participants | Median or Mean age (years) | Inclusion factors | Exclusion factors | Operator; equipment | Study Outcome | Protocol | Reference standard |
Vaidya et al (10) | 2014 | Prospective, ICU, India | 100 | 51.5 (mean) | Age > 18 SBP < 90 and Unresponsiveness, altered mental status, syncope, respiratory distress profound asthenia fatigue and malaise severe chest or abdominal pain | Etiology for shock (trauma, external bleeding, pregnancy related complications) | Intensivist; Sonosite M-Turbo and Voluson ultrasound machines. Straight linear array probe- 5 12 MHz, Curvilinear probe- 2–5 MHz and Sector array ultrasound probe 1–5 MHz | US high sensitivity, Specificity in diagnosing Obstructive shock and lowest specificity and PPV in diagnosing and distributive shock and lowest sensitivity in diagnosing hypovolemic shock | RUSH protocola | Clinical and biochemical studies, evaluation by physician and also depending on response to treatment. |
Majo et al (11) | 2004 | Prospective, ICU, Canada | 100 | 63 ± 14 | SBP < 100mmHg Fall in BP > 25% and inotrope use Evidence of low output Pulmonary/venous congestion | Within 7days after cardiac surgery | National Board of Echocardiography diplomates ; GE Vingmed System V or Vivid 5 with 2.5MHZ transducer | ECHO detection of cardiac/non cardiac cause for shock | No protocol. Pre specified ECHO criteria of cardiac cause of shock | Clinical diagnosis with PAC parameters, ECG, biochemical markers, angiography, surgery, autopsy, patient chart, discharge diagnoses, death certificates. Cardiac cause -clinical positive/negative. |
P Geng et al (12) | 2022 | Prospective, EICU, China | 112 | 66.5 ± 13.5 | Age > 18 < 95 years SBP < 90mmHg Signs of Hypoperfusion (altered mental status, resp distress, oliguria, fatigue, discomfort, mottling, elevated lactate and severe chest pain or abd pain Vasopressor dependent shock despite IV fluid challenge to achieve CVP of 8 | Preexisting hypotensive state from past medical history or reported by the patient. Transfer from another hospital with known diagnosis of shock No definite diagnosis of shock type established during hospitalization. | Operator: Physician who had completed 20 hours of emergency ultrasound workshop including the THIRD protocol and 3 years of experience with > 300 US exams per year Equipment: Philips Sparq. High frequency 4–12 MHz linear probe, 2–6 MHz curvilinear probe and a 2- 4MHz cardiac probe | ECHO diagnosis of type of shock using THIRD protocol Agreement between ECHO and final diagnosis of shock subtype. | THIRD protocolb | Three board certified physicians confirm final diagnosis of shock based on all relevant clincal data - history of presenting illness, signs, auxiliary examination results. Disagreement in diagnosis resolved by voting. |
Agmy et al (13) | 2017 | Prospective, ICU, Egypt | 63 | Not available* | Tachycardia > 100, non-palpable pulse, cool peripheries PP < 20mmHg, preexisting HTN, drop in SBP by 30% | | | Efficiency of transthoracic ultrasound (TUS) in hemodynamic assessment of shock. | FALLS protocolc. | History, clinical examination, laboratory investigations, chest x- ray, echocardiography, CT pulmonary angiography or other diagnostic tools. |
PPV, positive pressure ventilation; SBP, systolic blood pressure; BP, blood pressure; HTN, hypertension; CVP, central venous pressure; ICU, intensive care unit; EICU, emergency intensive care unit.
aRUSH: Rapid ultrasound for shock and hypotension
bTHIRD: Tamponade/Tension Pneumothorax, Heart, Inferior Vena Cava, Respiratory System, Deep Venous Thrombosis/Aortic Dissection.
cFALLS: Fluid administration limited by lung ultrasonography
± indicates standard deviation.
* Data are not available in the poster abstract.