Role of Ultrasound in Evaluation of Undifferentiated Shock in ICU Settings.

OBJECTIVE

To classify shock, using ultrasonography as the modality of choice for imaging and to assess the diagnostic accuracy of ultrasound as a tool to classify shock.

DESIGN

Prospective study.

SETTING

KEM Hospital, Pune in the ICU (Intensive care unit).

STUDY POPULATION

100 patients admitted to the ICU with undifferentiated shock.

METHODS

Bedside ultrasound examination was performed within 1 hour of admission to the ICU. These patients were also evaluated clinically and biochemically to confirm the type of shock. All patients immediately received standard diagnostic emergent interventions including physical examination, intravenous access for whole blood assays, arterial gas analysis, electrocardiography, continuous cardiac monitoring, supplemental oxygen and chest radiograph. Clinical parameters, urine output, ECG and biochemical tests were performed within 12 hours of USG. Additional investigations were performed wherever required. The ultrasonographic diagnoses were compared with the respective final clinical diagnoses by employing the Cohen kappa inter-rater coefficient of agreement. In addition, various ultrasound parameters were also analyzed to assess the best predictors for each type of shock.

RESULTS

The ultrasound diagnosis showed an overall good agreement (Cohen's kappa coefficient > or = 0.6) with the final clinical diagnosis, in identifying the type of shock, in the emergency setting, when ultrasound was done within 1 hour after admission to the ICU. In our study, ultrasound showed maximum sensitivity, specificity, negative and positive predictive values in the setting of obstructive shock. In addition, perfect agreement was seen between the ultrasound and clinical diagnosis, with a Cohen kappa coefficient of 1 in obstructive shock. The least sensitivity, specificity, negative and positive predictive values of ultrasound were seen in the setting of distributive shock. Least agreement between the ultrasound and clinical diagnosis was also seen in distributive shock, as most ultrasound findings were found to overlap with those in the other types of shock. (Cohen kappa coefficient of 0.6).

CONCLUSION

Ultrasonography carried out within 1 hour of admission to the ICU plays a major role in correct diagnosis of the type of shock and subsequent patient management. The best ultrasonographic predictors for diagnosis of each type of shock, can help the clinician to start timely specific interventions in critical care settings for each type of shock.