Utility of ultrasound in the ICU.

REVIEW URRENT C OPINION

Utility of ultrasound in the ICU Ranjit Deshpande, Shamsuddin Akhtar, and Ala Sami Haddadin

Purpose of review Use of ultrasound in the acute care setting has become more common in recent years. However, it still remains underutilized in the perioperative management of critical patients. In this review, we aim to increase the awareness of ultrasound as an important diagnostic modality that can be used in the perioperative period to improve patient care. Our main focus will be in describing the diagnostic uses of ultrasound to identify cardiac, pulmonary, airway and vascular diseases commonly encountered in acute care settings. Recent findings We find that ultrasound can be used in a quick fashion to assess a haemodynamically unstable patient. Protocols are available to use ultrasound as a part of cardiopulmonary resuscitation. Ultrasound can help in deciding fluid vs. pressor treatment by evaluating the inferior vena cava and other cardiac structures. Lung ultrasound can not only help in diagnosing pneumothoracies and effusions but also look at lung recruitment and diaphragmatic movement, hence can aid in deciding extubation strategies. This modality can be utilized for confirmation of endotracheal tube. Recent interest in axillary vein cannulation with ultrasound guidance has gained some momentum. Summary This article covers the recent developments and literature available on point of care ultrasound and its utilization in the perioperative period. We have not covered some other important uses of ultrasound such as abdominal examination looking at the aorta and other abdominal organs. This was beyond the scope of this article. Keywords airway ultrasound, echocardiography, lung ultrasound, perioperative medicine, ultrasound

INTRODUCTION

HISTORY OF MEDICAL ULTRASOUND

Ultrasound use in acute care medicine has gained a lot of following in recent years. Acute care physicians can use the ultrasound machine at the bedside to diagnose and manage patients. Ultrasound technology is also used to safely perform various percutaneous procedures at the bedside that previously required resource intensive transport to the radiology or cardiology suites. Until recently, ultrasound has been in the purview of cardiologist and radiologist. Technological advances have led to sophisticated, powerful and portable ultrasound machines that can be used at the bedside to yield reliable and meaningful information. To utilize ultrasound at the bedside, perioperative physicians should be proficient in its use. In this article, we want to highlight some of the applications of ultrasound in critical care medicine that can be used by nonradiologist/cardiologist. Our focus here is on common diagnostic uses of point-of-care ultrasound.

Karl Dussik in 1942 at the University of Vienna is credited with the first use of ultrasound for the diagnosis of brain tumours. In the recent years, Daniel Lichenstein pioneered the use of point-ofcare ultrasound in the ICU. With technological advances, the ultrasound machines continue to evolve, become smaller and portable. Although many machines are available in the market, an ultrasound machine to be used in the critical care units should have at the minimum Doppler, Motion mode and 2D capabilities. The machine should Department of Anesthesiology, Yale University School of Medicine, New Haven, Connecticut, USA Correspondence to Ranjit Deshpande, MBBS, Department of Anesthesiology, Yale University School of Medicine, New Haven, CT 06510, USA. Tel: +1 203 785 2802; fax: +1 203 785 6664; e-mail: Ranjit. [email protected] Curr Opin Anesthesiol 2014, 27:123–132 DOI:10.1097/ACO.0000000000000057

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Copyright © Lippincott Williams & Wilkins. Unauthorized reproduction of this article is prohibited.

Intensive care and resuscitation

Indications for use of ultrasound in the perioperative period

KEY POINTS The use of ultrasound in perioperative medicine is evolving and we as an anaesthesiologist should be proficient in the use of this technology. Cardiac ultrasound is currently used by us in the operating room; we need to understand its utility outside of the intraoperative phase and utilize it in managing preoperative and postoperative issues one has to understand that if we do find something then we must get a formal echo examination. Lung/pulmonary ultrasound is easy to learn and perform and can play an important role in diagnosing pneumothoraces and significant pulmonary effusions. There are issues that should be immediately addressed. Airway ultrasound has uses for percutaneous tracheostomies and confirming endotracheal tube placement.

be able to accommodate a high-frequency linear transducer, a low-frequency curved array transducer and a cardiac low frequency transducer with imaging capabilities.

Point-of-care ultrasound is typically used for two broad reasons. It is either used for performing percutaneous invasive procedures or for diagnostic evaluation. Its value in aiding well tolerated central venous access was recognized early and devices with limited capabilities have been in use for more than a decade. As ultrasound technology advanced, it is now used to gain peripheral intravenous (i.v.) access, peripheral arterial access. It is also used to aid pericardiocentesis, pleuracentesis, paracentesis and even tracheostomy and airway devices (Fig. 1) However, ultrasound’s greatest promise is being realized in helping bedside diagnosis. As Fig. 2 depicts, it is used to diagnose multiple diseases, especially the heart, lung and abdominal diseases. It is also used to identify venous thrombosis in critically ill patients and cerebral blood flow perioperatively.

Cardiac ultrasound Many critically ill patients become haemodynamically unstable during the course of their illness or in

Heart

Pericardiocentesis

Lung

Pleuracentesis and chest tube placement

Cardiothoracic

Venous access Vascular Arterial access Interventional Paracentesis Abdominal and pelvis Suprapubic catheter

Airway

Percutaneous tracheostomy

Intubation

FIGURE 1. Interventional uses of ultrasound. 124


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Utility of ultrasound in the ICU Deshpande et al.

Tamponade

Heart

Preload

Contractility

Valvular problems

Cardiothoracic

Pneumothorax

Lung

Efussion

Renal

Pulmonary edema

Abdomial/pelvis Liver Diagnostic Abdomial/pelvis

Gall bladder

Ocular

Urinary bladder

Vascular

Deep vein thrombosis

TCD's

FIGURE 2. Diagnostic uses of ultrasound.

the perioperative period. Bedside echocardiography can rapidly help assess a haemodynamically unstable patient. Common indications for performing an echocardiographic examination in the ICU are haemodynamic instability, infective endocarditis, aortic dissection and rupture, and unexplained hypoxemia, and to look for source of embolus, ventricular failure, hypovolemia, pulmonary embolus, acute valvular dysfunction, complications after cardiothoracic surgery and cardiac tamponade can be readily diagnosed by echocardiography. Correct placement of intra-aortic balloon pump can also be aided by echocardiography. In patients with ventricular assist device, echocardiography is helpful in confirming position of the cannula, septum

and potential from weaning the device. Echocardiography is helpful in aiding pericardiocentesis. Echocardiography is also being increasingly used to assess cardiovascular status in patients presenting for urgent or emergent noncardiac operative procedures. Indications in the preoperative period can be to evaluate undifferentiated ejection systolic murmur and rule out severe valvular dysfunction, perioperative haemodynamic instability, assess ventricular function, evaluate hypoxemia and rule out severe cardiac dysfunction in the setting of limited functional capacity. Two modalities to assess cardiopulmonary function are transthoracic and transesophageal echocardiography. On the basis of a particular situation, both



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expert consensus statement Basic Perioperative Transesophageal Echocardiography Examination: A Consensus Statement of the American Society of Echocardiography and the Society of Cardiovascular Anesthesiologists [6 ]. Inferior vena cava view helps in the assessment of the preload and volume responsiveness in critically ill patients. In a healthy patient breathing spontaneously, there is a decrease in inferior vena cava (IVC) diameter on inspiration by nearly 50% due to changes in pleural pressure (http://www. ncbi.nlm.nih.gov/pubmed/?term=Respiratory+ maneuvers+in+echocardiography:+a+review+of+ clinical+applications). A FLAT IVC has been described as an IVC diameter less than 2 cm [7]. This correlates with a central venous pressure of less than 10 cm. Maximum and minimum IVC diameter values are interrogated in M mode and measured in long axis view. These measurements are used to determine distensibility index for IVC (max-min/mean or max-min/min). Cut-off values of 12% using maxmin/mean and 18% using max-min/min were shown to accurately predict responders versus nonresponders [7,8]. On the basis of these results, assessment of the IVC variation during mechanical ventilation may prove to be a useful technique to predict fluid responsiveness and thus guide fluid resuscitation in the ICU and may be better than the stroke volume variation (SVV) obtained with the Vigileo monitor that failed to predict fluid resuscitation in patients with sepsis [9]. Pericardial effusions can be seen with echocardiography. Signs of large pulmonary embolus causing haemodynamic compromise can also be detected with echocardiography. In the presence of right ventricular dilatation, impairment of RV free wall motion with apical strain, with akinesia of the mid free wall but normal motion at the apex (McConnell’s Sign) [10] dilatation of the right pulmonary artery and prompt treatment with thrombolysis should be considered. The 2010 Advance Life Support (ALS) (UK) guidelines recognize the potential role of ultrasound

can be used in the ICU and perioperative period. Ideally, perioperative physicians and intensive care physicians should be adept at both. Both of them have certain advantages and limitations. Comparison is presented in Table 1. Time taken to perform a complete ultrasound examination along with a focused echocardiography is around 20 min [1]. A number of different protocols have been defined for a quick bedside point-of-care examination (FATE, RACE, FADE, BEAT, RUSH) [2–5]. The transthoracic echocardiogram examination can be divided into four parts each looking for certain diseases in the ICU. Subcostal view is used to assess ejection fraction, left ventricle (LV) and right ventricle (RV) size and function, left atrial/right atrial size and intra-atrial septal dynamics and pericardial effusion. Apical four-chamber and subcostal views are favoured for RV assessment. This view is a part of the FEEL (focused echocardiography in emergency life support) examination. This might be the only good quality view for patients in the ICU. However, it could be difficult to get this view in patients with abdominal surgeries due to dressing. Parasternal long axis view as a part of the critical care examination should be focused at assessing pericardial fluid, LV/RV size and function and septal kinetics. This view is used to calculate fractional shortening, ejection fraction and to obtain the diameter of the left venricular outflow track (LVOT) for cardiac output calculations. Parasternal short axis view should look at the mid-papillary view and then move on to assess the other views (apical, mitral, basal or aortic). One should appreciate wall motion and septal kinetics in this view. Apical four-chamber view is important to identify RV dilatation, assessment of the septum, the LV, ejection fraction by Simpson’s method, and valvular disease can be seen in this view. A detailed examination of the valves and great vessels may not be a part of the basic ICU examination. However, it is important to pick up abnormalities and get an expert opinion. A basic transesophageal echocardiogram (TEE) examination should include at least 11 views as described in the

&

Table 1. Comparison of transthoracic versus transoesophageal echocardiography TTE

TEE

Better visualization of LV apex

Prone to foreshortened ventricles might miss an LV apical thrombus.

Better view of the ventricular aspect of a prosthetic MV

Better view of the LA aspect of a prosthetic MV and LA appendage

Interrogation the interventricular septum is better.

Excellent views of the MV, AV

Poor image acquisition in presence of tubes, dressing, emphysema and mechanical ventilation with high level of PEEP

Better image quality in obesity, emphysema, mechanical ventilation with high level of PEEP, presence of tubes, surgical incisions, dressings

LA, left atrium; LV, left ventricle; MV, mitral valve; PEEP, positive end expiratory pressure; TEE, transesophageal echocardiogram.

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imaging during ALS. No studies have shown that it improves outcomes. Presence of sonographic cardiac activity at the beginning of resuscitation has been associated with successful outcome in a recent study. A number of protocols have been studied in this setting. Some involve looking at the heart while others combine the evaluation of lung, IVC, aorta and endotracheal tube (ETT). The aim is to perform a quick examination with minimal interruptions of chest compression. The Resuscitation council of UK along with the British Society of Echocardiography have developed an echocardiography training programme (FEEL-UK) for novice practitioners. Echocardiography performs much better than pulmonary artery catheter (PAC) in many clinical situations. In a prospective study, Benjamin et al. [11] found that the TEE data disagreed with the PAC evaluation of intracardiac volume in 55% of cases and assessment of myocardial function in 39% of cases. In 58% of patients, therapeutic recommendations based on PAC data were different from those after TEE. This study also looked at the time to data acquisition. TEE was performed in 12 7 versus 30 min or more for pulmonary artery catheterization insertion. In a study by Kaul et al. [12], the time required to place a PAC and record the data was 63 45 versus 19 7 min to perform bedside TEE. Poelaert et al. [13] found that of 64% of patients with PAC, 44% underwent therapy changes after TEE (41% in the cardiac and 54% in the septic subgroup). They also found that in 41% of patients without

PAC, TEE led to a change in therapy. They concluded that TEE produced a change in therapy in at least one-third of ICU patients, independent of the presence of PAC. In some ICUs, TEE has completely replaced PAC for assessment of circulatory status of mechanically ventilated patients.

Lung and pleura Many patients in the ICU develop diseases involving the lung and the pleura (Figs 3 and 4). Although computed tomographic (CT) scans can help identify a multitude of pulmonary abnormalities, it requires transport of critically ill patients out of the unit. Significant catastrophic events during transport have been reported. Clinical examination and chest radiography have been ubiquitously used at the bedside to diagnose common clinical problems. However, their inherent limitations are well recognized, especially when performed in a semi-recumbent or supine position. Lung ultrasound can be used at the bedside to diagnose a number of conditions: pneumothorax, interstitial syndrome, lung consolidation and pleural effusion. Combining the lung ultrasound with an echocardiographic and venous examination can yield a lot of information in a relatively short period of time [14]. Lung ultrasonography is predominantly based on the careful analysis of artefact because the waves poorly penetrate inflated lungs. In normal individuals, the visceral and parietal pleura can be seen

Pneumothorax

Interstitial syndrome Diagnostic Pleural effusion

Lung ultrasound Consolidation/ atelectasis

Interventional

Pleurocentesis/ thoracentesis

FIGURE 3. Lung ultrasound uses. 0952-7907 ß 2014 Wolters Kluwer Health | Lippincott Williams & Wilkins


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Peripheral venous

Venous thrombosis

Central venous

Access

Venous thrombosis

Access

Internal jugular

Femoral

Subclavian/axillary

FIGURE 4. Ultrasound of the venous system.

sliding against one another during respiration. Because air is a relatively poor conductor of ultrasound waves, in normal individuals, the parietal pleural reflections can be seen and are called A-lines or reverberation artefacts. When there is fluid or thickening of the interstitium, the pleural surface gives rise to B-lines. B-lines are artefacts that arise when an ultrasound wave interacts with a small air–fluid interface. The presence of lung sliding and B-lines rules out a pneumothorax with a negative predictive value of 100% at the site of the ultrasound probe [15]. It is important to examine multiple points, especially the nondependent areas of the chest wherein air would accumulate. Although ultrasound is a good tool to rule out a pneumothorax, the diagnosis of pneumothorax with lung ultrasound depends on the identification of the lung point. The lung point is the point at which the partly inflated lung touches the chest wall and when observed has 100% specificity and 66% sensitivity for pneumothorax [16]. In a completely collapsed lung wherein no part of the lung is touching the chest wall, no lung point can be identified and the sensitivity is decreased. A recent metaanalysis concluded that ultrasound was superior to chest radiography in detecting pneumothorax. Lung ultrasound has also been shown to be of value in detecting alveolar interstitial syndrome by detecting B-lines. Multiple B-lines signify pulmonary oedema due to cardiogenic or noncardiogenic causes and may also be seen in patients with lung 128


infections or atelectasis. B-lines are dynamic and disappear, as the underlying process is treated usually by treating heart failure, removing fluid by dialysis or treating pneumonia. B-lines have also been shown to have clinical significance in distinguishing acute cardiogenic pulmonary oedema from acute chronic obstructive pulmonary disease (COPD) exacerbation [17]. ‘The BLUE protocol’, a goal-directed pathway described by Lichtenstein et al., uses lung ultrasound to establish a rapid diagnosis in a patient with acute respiratory failure [18]. Recently, lung ultrasound has been shown to help quantitatively assess the lung re-aeration after antimicrobial therapy in 24 critically ill patients with ventilator-associated pneumonia. At the bedside, the whole lung was examined as described above, and each region of interest was attributed a score according to four stages of lung aeration before and after antimicrobial therapy. A tight correlation was found between pulmonary re-aeration measured by lung CT and the change in the ‘ultrasound score’. Another study also showed that lung ultrasonography can be used to estimate alveolar reaeration in patients treated for ventilator-associated pneumonia and to estimate positive end expiratory pressure (PEEP)-induced lung recruitment. Further studies are required to confirm the utility of lung ultrasound, in measuring alveolar recruitment resulting from PEEP or recruitment manoeuvre [19,20]. Volume 27 Number 2 April 2014


Utility of ultrasound in the ICU Deshpande et al. &

Xirouchaki et al. [21 ] looked at the impact of lung ultrasound (LU) on clinical decision-making in mechanically ventilated critically ill patients. Two hundred and fifty-three LU examinations were performed. They found that the management was changed directly as a result of information provided by the lung ultrasound in 119 out of 253 cases (47%). In 81 cases, the change in patient management involved invasive interventions (chest tube, bronchoscopy, diagnostic thoracentesis/fluid drainage, continuous venous–venous haemofiltration, abdominal decompression, tracheotomy), and in 38 cases noninvasive interventions (PEEP change/ titration, recruitment maneuver, diuretics, physiotherapy, change in bed position, antibiotics initiation/change). In 53 out of 253 cases (21%), lung ultrasound revealed findings that supported diagnoses not suspected by the primary physician. Lichtenstein et al. looked at 32 patients with adult respiratory distress (ARDS) and 10 healthy volunteers to compare the diagnostic performances of auscultation, chest radiography and lung ultrasonography in acute respiratory distress syndrome. They found that lung ultrasound is highly sensitive, specific and reproducible for diagnosing main lung pathologic entities in patients with ARDS. Lung ultrasonography had a diagnostic accuracy of 93% for pleural effusion, 97% for alveolar consolidation and 95% for alveolar-interstitial syndrome. Lung ultrasonography, in contrast to auscultation and chest radiography, could quantify the extent of lung injury [22]. Accuracy of lung ultrasound for diagnosing pneumothorax, lung consolidation, alveolar-interstitial syndrome and pleural effusion in critically ill patients is well documented. The routine use of lung ultrasound appears as a practical alternative to bedside chest radiography: it is noninvasive, easily repeatable at the bedside and provides a detailed evaluation of the respiratory diseases [23]. Lung ultrasound in the hands of well trained intensivists appears to be one of the most promising techniques for respiratory system monitoring.

Vascular ultrasound Vascular ultrasound is used for two primary purposes: evaluation of the peripheral vascular system and guidance for vascular access. Evaluation of the peripheral vascular system can involve both the arterial and venous systems. The evaluation of the arterial system is beyond the scope of this article. We will focus on the venous system especially on the diagnosis of deep vein thrombosis. Portable ultrasound machines with Doppler function can help evaluate the patients for deep vein

thrombosis without the need to transport to the radiology suite. It is important to understand the deep venous anatomy of the upper and lower extremities prior to performing this examination. The patient lies supine in a reverse Trendelenberg position (approx. 458) such that the veins are distended. The lower limb being examined is externally rotated and the knee is slightly bent. For the upper extremity, the patient lies supine with his head flat on a pillow to scan the subclavian and axillary veins and in the reverse Trendelenburg position to scan the remainder of the arm veins. The ultrasound examination is started with a B mode scan followed by a transverse plane compression test. The most reliable method to differentiate venous from arterial flow is to use pulse wave Doppler and compare waveforms between the vessels. The waveform seen in veins will tend to be continuous varying only with respiration. Arterial waveforms should have a peak and trough quality or a frank triphasic flow pattern specific diagnostic criteria can help diagnose the venous thrombi in upper and lower extremities. Physician-performed compression studies yielded a sensitivity of 86% and a specificity of 96% with a diagnostic accuracy of 95%. Median time delay between the ordering of a formal vascular study (FVS) and the FVS result was 13.8 h [24]. Use of ultrasound to access the internal jugular and the femoral veins is practiced widely; subclavian and axillary veins can also be accessed by using ultrasound. The approach to the subclavian vein can be accomplished via two approaches, supraclavicular or infraclavicular. For infraclavicular access, the ultrasound probe is placed inferior and lateral to the clavicle, oriented initially in the long axis and then in the short axis to differentiate the vein from the artery. The probe is placed more lateral to the traditional blind approach and gets the vein when it changes from the axillary to the subclavian.

Upper airway ultrasound Raphael and Conrad [25] initially described use of ultrasound to visualize the ETT in 1987; since then, limited numbers of studies have been published describing the use of airway ultrasound for endotracheal intubation, difficult airway assessment, prediction of postextubation stridor, extubation failure and percutaneous tracheostomy. Ultrasound has been used to look at different aspects of difficult intubation. Pretracheal soft tissue swelling has been identified as a risk factor for difficult laryngoscopy and can be evaluated with an ultrasound [26]. However, Komatsu et al. [27] was unable to reproduce initial findings. The data



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are inconclusive for using ultrasound as a tool to predict difficult airway. Ultrasound can be used as an adjunct in confirming endotracheal tube placement and positioning confirmation and position verification. This is especially true in a code situation, as one might not get end-tidal CO2 or may be confounded by other factors (CO2 from the unfastened stomach, airway obstruction, technical error or falsely negative with epinephrine use) [28]. Here, one can use the ultrasound for direct visualization of the pleural motion, the diaphragmatic motion. Eslami et al. [29] suggest that the diaphragmatic motion in the right subcostal view is an effective adjunct to diagnose ETT placement in emergency department. A total of 57 patients aged 59 5 years who underwent ETT insertion were studied. Thirty-four of them were men (60%). Ultrasound correctly identified 11 out of 12 oesophageal intubations for sensitivity of 92% [95% confidence interval (CI) 62–100], but misidentified one oesophageal intubation as tracheal. Sonographers correctly identified 43 out of 45 (96%) tracheal intubations for specificity of 96% (95% CI 85–99), but misdiagnosed two tracheal intubations as oesophageal ventilation [29]. In case of an oesophageal intubation, one would notice an immobile or a paradoxically moving diaphragm [30]. Another method described in the literature is identifying lung sliding, which is direct visualization of the movement of the visceral pleura over the parietal. Cuff inflation with isotonic saline/ air bubbles or keeping the stylet in the ETT to aid in the ultrasound visualization has also been used [31]. The T.R.U.E. protocol by Chou and his group was product of a prospective observational study to look at real-time tracheal ultrasound to confirm ETT placement during CPR [32]. Here, the same team looked at 89 patients during CPR out of whom seven had oesophageal intubations. The sensitivity, specificity, positive predictive value and negative predictive value of tracheal ultrasonography were 100 (95% CI 94.4–100), 85.7 (95% CI 42.0–99.2), 98.8 (95% CI 92.5–99.0) and 100% (95% CI 54.7–100), respectively [33 ]. Ultrasound can also be used to determine the ideal size of double lumen tube for a patient. It has been correlated well with MRI, which is the gold standard. When choosing a double lumen tube (DLT), one can measure the left mainstem bronchus and get a proper size tube. Sustic et al. [34] performed two independent studies with 20 patients. In the initial study, tracheal width obtained by CT scan and ultrasound just above the sternoclavicular joint in the transversal section were measured. In the second part of the study, patients’ tracheas were intubated with a left DLT on the basis of ultrasound measurements. The frequencies of incorrect &

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selections of left DLT and unsatisfactory lung collapse were analysed. There was a strong correlation between tracheal width as measured by ultrasound and tracheal width (r ¼ 0.882, P < 0.001) and left main bronchus width (r ¼ 0.832, P < 0.001) as measured by CT. In five cases (25%), incorrect left DLT by ultrasound was selected, and one (5%) was found to have an unsatisfactory lung collapse. Measurement of the outer tracheal width by ultrasound can be a useful method for predicting the diameter of left main bronchus and for selecting correct size left DLT [34]. A study done by Ding et al. [35] used real-time ultrasound to look at the air leak and hypothesized that the air column width measured by ultrasound may be correlated to the development of postextubation stridor. Air leak in patients with postextubation stridor was 25 ml and in the nonstridor group was 300 ml. The air column width was 4.5 mm in the stridor group and 6.4 in the nonstridor group. The authors concluded that the air column width during cuff deflation was a potential predictor of postextubation stridor [35]. Some limitations to the study were presence of secretions and the size of endotracheal tube. Intubated patients receiving mechanical ventilation in a medical ICU had their breathing force evaluated by ultrasound. The probe was placed along the right anterior axillary line and the left posterior axillary line for measurement of liver and spleen displacement in craniocaudal aspects, respectively. The cutoff value of diaphragmatic displacement for predicting successful extubation was determined to be 1.1 cm. The liver and spleen displacements measured in the study are thought to reflect the ‘global’ functions of the respiratory muscles, and this method is a good parameter of respiratory muscle endurance and predictor of extubation success [36]. More studies are needed in this aspect of ultrasound use. Accurate identification of anterior neck structures during percutaneous dilatational tracheostomy can eliminate potential dreaded complications. Although structures within or behind the trachea are not seen, much useful information may be obtained regarding pre and paratracheal anatomy using ultrasound. Before proceeding for percutaneous dilatational tracheostomy, the pretracheal area should be examined for tracheal midline, approximate level of tracheal cartilages, anterior jugular veins (its diameter and location, i.e. in or near the midline), thyroid isthmus, vulnerable thyroid vessels and any other aberrant vessels. With refined ultrasound technology, it will be possible in the future to have the real-time guidance in the placement of dilators and tracheostomy tubes. Volume 27 Number 2 April 2014



TRAINING In the USA, use of ultrasound by intensivist is steadily increasing. American College of Chest Physicians has recently introduced a critical care ultrasonography certificate completion programme. This programme is spread over months and involves online as well as campus lectures. Other organizations such as Society of Critical Care Medicine have comprehensive certificate courses. All these courses have a theoretical/lecture component and a practical/ hands-on component. The Society of Cardiovascular anaesthesiologists allows for basic echocardiography certification for anaesthesiologists via the practice pathway. Many European, British and Australasian societies have, or are, incorporating ultrasound training as part of their anaesthesia and critical care curriculum. It is expected that use of ultrasound will become more ubiquitous in anaesthesiology and critical care practice and hopefully improve patient outcomes.

CONCLUSION Ultrasound in the perioperative arena is a relatively new advancement for anaesthesiologists. Emergency physicians and intensivists are using this technology beyond cardiac and pulmonary scanning to include the aorta, abdominal organs and even to look for increased intracranial pressure. In this article, we have looked at some studies to support and refute the use of ultrasound in critically ill patients. We as perioperative physicians need to familiarize ourselves with this technology. There needs to be research looking at patient outcomes to support the use of ultrasound examination in the perioperative period. This may eventually lead to ultrasound being an extension of our routine physical examination. Acknowledgements No funding was received for this article. Conflicts of interest There are no conflicts of interest.

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Ultrasound Utility in the Diagnosis of a Morel-Lavallée Lesion.

Utility of the PRE-DELIRIC delirium prediction model in a Scottish ICU cohort.

Application of rapid ultrasound in shock protocol in the ICU for management of shock.

Utility of endoscopic ultrasound in patients with portal hypertension.

Utility of transcranial ultrasound in predicting Alzheimer's disease risk.

Utility of diagnostic ultrasound in evaluating fracture healing.

The utility of transvaginal ultrasound in the ED evaluation of complications of first trimester pregnancy.

The utility of midtrimester ultrasound assessment of the subcutaneous space in predicting cesarean wound complications.

Utility of ultrasound in the diagnosis of polycystic ovary syndrome in adolescents.

Evaluation of ultrasound for central venous access in ICU by an in experienced trainee.

Bedside Doppler ultrasound for the assessment of renal perfusion in the ICU: advantages and limitations of the available techniques.

The utility of ultrasound elastography in differentiation of endometriomas and hemorrhagic ovarian cysts.

The utility of ultrasound surveillance of fluid and growth in obese women.

Catatonia in the ICU.

Neuromonitoring in the ICU.

Noise in the ICU.

Telemedicine in the ICU.

Sedation in the ICU.

The Utility of MicroPure™ Ultrasound Technique in Assessing Grouped Microcalcifications without a Mass on Mammography.

The utility of ultrasound-guided thoracentesis and pleural biopsy in undiagnosed pleural exudates.

The utility of thoracic ultrasound in patients with acute eosinophilic pneumonia.

Identifying decreased diaphragmatic mobility and diaphragm thickening in interstitial lung disease: the utility of ultrasound imaging.

Utility of high-frequency ultrasound: moving beyond the surface to detect changes in skin integrity.

The utility and limitations of contrast-enhanced ultrasound for the diagnosis and treatment of prostate cancer.