Until a few years ago, the use of ultrasound in anesthesia was primarily for vascular access and regional anesthesia. However, in the last decade, its development and application have been exponential. Point of Care Ultrasound (POCUS) refers to the use of portable ultrasound devices at the patient‘s bedside to provide immediate diagnostic and therapeutic insights. This approach enables to perform real-time imaging to guide clinical decisions in a difference scenario such as emergency departments, intensive care units, operating rooms, and outpatient clinics.

POCUS has been described as a useful tool for anaesthesiologist in all the perioperative period and now is an integral part of anesthesia practice, contributing to enhanced patient safety and procedural efficacy.¹

Additionally, several cardiopulmonary protocols have been proven to be effective in the perioperative setting.² Focusing on the postoperative period, episodes of hypoxia and hypotension are common complications in the PACU setting. Implementing standardized POCUS protocols ensures consistency, accuracy, and efficiency in patient management. Consequently, POCUS could be used to differentiate diagnoses in patients experiencing hemodynamic instability or acute respiratory failure.

Focus cardiac ultrasound (FOCUS) is an echocardiographic examination performed at the bedside and includes a series of specific cardiac views that provide valuable information about heart´s structure and function and identify potential causes of haemodynamic instability. The Parasternal Long-Axis (PLAX) view, Apical Four-Chamber (A4C) view, and Subcostal view are used to assess global cardiac function, left ventricular size and function, pericardial effusion, and the diameter and collapsibility of the inferior vena cava (IVC).³ Based on these findings, different types of shock can be identified. In hypovolemic shock, left ventricular function is normal or hyperdynamic and the IVC is small and collapsible more than 50%. In cardiogenic shock, left ventricular function is reduce with possible regional wall motion abnormalities or dilated left ventricle. Obstructive shock, such as cardiac tamponade, presents with a pericardial effusion with diastolic collapse of right ventricle. Pulmonary embolism shows a dilated right ventricle with septal flattening and a small left ventricle. Distributive shock, including septic shock, typically shows hyperdynamic or normal cardiac function and a collapsible IVC due to relative hypovolemia.⁴

Respiratory complications are common in the postoperative period and lung ultrasound (LUS) is increasingly being recognized as a valuable tool in the PACU. LUS offers several advantages, including being non-invasive, easily repeatable, and capable of providing real-time diagnostic information.⁵Patients in this setting are particularly susceptible to various respiratory complications due to the residual effects of anesthesia, the stress of surgery, and any preexisting pulmonary conditions. LUS has shown high sensitivity and specificity for detecting common postoperative complications, such a pulmonary oedema, pleura effusion, atelectasis and pneumothorax.⁶ LUS scanning technique examinate bilateral thoracic regions, covering anterior, lateral and posterior-lateral thoracic areas. LUS finding include the presence of lung sliding; A-lines, suggesting normal aeration or pneumothorax; B-lines, indicating interstitial syndrome or pulmonary oedema; consolidation image, which may signify atelectasis or pneumonia; and pleura effusion. The Blue Protocol, developed by Daniel Lichtenstein, is a standardized approach to using lung ultrasound in critically ill patients.⁷ It is particularly useful in the PACU for rapidly diagnosing causes of acute respiratory failure.

Therefore, perioperative point of care ultrasound value is particularly evident in emergent cases and in unstable patients, since it provides crucial information for decision making. These advancements facilitate the regular use of bedside ultrasound in anesthesia practice, where it now assumes a crucial role similar to the fifth pillar of the physical examination.⁸

A new concept in anesthesia practice involves the introduction of bedside ultrasound at ‘Minute Zero.’ This approach emphasizes the use of ultrasound at the beginning of the perioperative period, providing an image of the patient´s baseline status and providing a basis for comparison with subsequent evaluations. Minute Zero evaluation aims to have a global picture of patients´clinical condition and not only to answer targeted question.⁹

There are two critical moments in which patients should be evaluated: upon arrival at the operating room – pre-operative Minute Zero; and upon arrival at the post-anaesthetic care unit (PACU) – PACU Minute Zero.

Minute Zero ultrasound examination consists of a lung ultrasound to detect lung sliding, B lines, pleura effusion or areas of consolidation; focus echocardiography to evaluate global and regional contractility, compare the relationship between the right and left ventricles, and assess the inferior vena cava; abdominal ultrasound to examine the bladder and assess gastric content before surgery; in the PACU Minute Zero, this can be replaced with scanning to detect intraperitoneal free fluid in abdominal surgery.

Performing ultrasound at Minute Zero allows anesthesiologists to assess the patient‘s baseline status before anesthesia induction and/or in the immediately postoperative time. This early assessment can detect hidden pathologies such as cardiac abnormalities (, lung conditions (e.g., bilateral B lines, pleural effusions, atelectasis), or abdominal issues (e.g., small intraperitoneal free fluid, urinary retention), which may not be evident on physical examination alone.

Identifying these abnormalities early helps in risk stratification and can guide the anesthesia plan or recovery plan. For instance, knowing about cardiac abnormalities can influence fluid management or choice of anesthetic agents. Therefore, this proactive approach not only improves diagnostic accuracy but also has the potential to anticipate several complications and optimize patient outcome by facilitating timely interventions and personalized care strategies.⁹

In conclusion, POCUS is an invaluable tool for anesthesia that should be used routinely, not only in the presence of complications but also as a routine bedside ultrasound examination in patient with previous moderate or severe pathology, patient having major surgery and elderly patients. By integrating POCUS and Minute Zero into the standard perioperative assessment, we can more effectively recognize patients baselines and identify any pathologies that may influence the intraoperative and postoperative outcomes.

References

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8. Narula J, Chandrashekhar Y, Braunwald E. Time to Add a Fifth Pillar to Bedside Physical Examination: Inspection, Palpation, Percussion, Auscultation, and Insonation. JAMA Cardiol. 2018 Apr 1;3(4):346-350. doi: 10.1001/jamacardio.2018.0001. PMID: 29490335.

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