Packed Red Blood Cells

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32 | Fundamentals of Frontline Surgery

ratio. SWB is most provided as low titre group O whole blood (LTOWB). The AABB (formerly known as the American Association of Blood Banks) requires any facility using LTOWB to locally determine the number of units that a patient can receive, the nature of the patients, and the maximum anti-A and anti-B titre threshold. Civilian and military practices of LTOWB vary in terms of these parameters. Also, the length of time that an LTOWB unit can be stored and transfused varies, but the duration can never exceed that speciﬁed by the nature of the anticoagulant in which the whole blood was collected. LTOWB offers a more ‘concentrated’ product compared to reconstituted whole blood using conventional components, as whole blood is collected into 70 mL of storage solution/ anticoagulant whereas each conventional RBC unit transfused contains up to 110 mL of additive solution that permits the extended storage of the RBCs up to 42 days; the additive solution does not carry oxygen, nor does it promote haemostasis. FWB is also collected into 70 mL of solution, but it is not stored for a prolonged period before its transfusion. FWB is not normally permitted for civilian use as it is not tested for transmissible diseases before transfusion. Both LTOWB and FWB offer several other advantages over separated blood products, including convenience in transportation than separate units of RBCs, plasma, and platelets and reduced risk of bacterial contamination compared to conventional warm stored platelets and simplifying the logistics of the resuscitation by offering all three components in one bag. In fact, in a study of paediatric trauma patients, the use of LTOWB was shown to provide balanced resuscitation quicker than when only conventional components were used, even though a massive transfusion protocol that included the immediate provision of platelets was available at the hospital where the study was conducted.

The evidence to support the use of LTOWB, especially in early resuscitation, is mounting, albeit indirectly. In a secondary analysis of a randomised controlled trial that demonstrated the superiority of adding two units of plasma transfusion to the standard of care during the helicopter evacuation of trauma patients to a hospital, receipt of any blood product during pre-hospital resuscitation yielded a signiﬁcantly improved 30-day survival rate compared

to patients who received crystalloids alone. A greater survival beneﬁt was demonstrated amongst those who received RBCs and plasma compared to those who received plasma alone. While this study did not involve the transfusion of LTOWB directly, the combination of RBC and plasma transfusion would have been provided by LTOWB, in addition to a small dose of cold-stored platelets (which might be hyper-functional compared to their room temperature-stored). During the recent conﬂicts in Iraq and Afghanistan, for casualties presenting haemorrhagic shock, a transfusion strategy that included FWB with RBCs and plasma was associated with improved survival compared to the use of stored components only (FFP, RBCs, and PLTs). Compared to SWB or component therapy, FWB is available in austere conditions (requires only the presence of donors and collection equipment), has no loss of clotting factor or platelet activity that is often associated with storage, and has no red blood cell ‘storage lesion’.

PACKED RED BLOOD CELLS

The main advantage of a packed red blood cell (PRBCs) transfusion is the replenishment of oxygencarrying capacity. Emergency transfusion of PRBC when the recipient blood group is unknown should be performed using only type O units. In the past, resuscitation of bleeding trauma patients was based on the transfusion of high volumes of PRBCs, in ratios reaching 10:1 between PRBCs and plasma. However, recent data suggest that imbalanced transfusion ratios with high ratios of PRBCs have a detrimental effect on patient outcomes. Thus, most resuscitation protocols now instruct a balanced transfusion of PRBCs with plasma and platelets. In prehospital scenario, the use of PRBCs is hindered by the need for cold storage and controlled temperature capability, so most prehospital systems do not provide PRBCs at the point of injury. Some systems, however, provide PRBCs during transport for patients suffering from haemorrhagic shock. The positive effect of prehospital PRBCs transfusion was demonstrated in a retrospective analysis of US military combat casualties treated during aeromedical evacuation; early transfusion of PRBCs was associated with improved survival.

No Blood … What to Do? | 33

PLASMA

The use of plasma as a resuscitation ﬂuid holds many theoretical advantages – plasma has a high oncotic pressure which allows effective intravascular volume preservation, a physiologic pH level for mitigation of trauma-related acidosis, and a normal concentration of clotting factors that can potentially reduce the lethal trauma-induced coagulopathy. Emergency transfusion of plasma to patients of unknown blood group should be performed with group AB or A plasma. Abundant data support the beneﬁcial effect of early plasma-based resuscitation. Most of these data are derived from in-hospital care; however, in recent years, prehospital systems are adopting the use of plasma as a resuscitation ﬂuid, replacing the classic crystalloids-based resuscitation with some preliminary data supporting the beneﬁcial effect of prehospital plasma use already available. The main obstacle to prehospital plasma use remains the logistical challenge. The most used plasma is either thawed fresh frozen plasma (FFP) or liquid, never-frozen plasma. These ﬂuids require refrigeration, and unless being used in a high-volume environment, will result in a high wastage rate. A possible solution to the logistical constraints of liquid plasma transfusion is freeze-dried plasma (FDP). FDP has similar biochemical properties of thawed FFP or liquid plasma, can be stored at ambient temperatures, has a shelf life of 18–24 months, and can be reconstituted and ready to use within minutes. These characteristics of FDP make it an ideal product for plasma administration in prehospital scenario and point of injury care. Several FDP products are currently available worldwide.

CRYSTALLOIDS

These are solutions of water and electrolytes, including 0.9% normal saline (NS), lactated Ringer’s solution (LR), and Hartmann’s solutions (HS). NS is slightly hypertonic, containing equal amounts of sodium and chloride, causing it to be both hypernatremic and hyperchloremic. Replenishing extracellular ﬂuid volume with a large volume of saline was previously advocated, especially during the wars in Korea and Vietnam. However, the widespread use of isotonic ﬂuids was not without harmful effects,

such as the so-called Da Nang lung (later termed acute respiratory distress syndrome or ARDS), compartment syndrome, coagulopathy, hyperchloremic metabolic acidosis, immune dysfunction, kidney injury, and eventually, increased mortality.

An important study that investigated outcomes of trauma patients who were resuscitated using large volumes of crystalloid was published in 1994 by Bickell et al. In this study, hypotensive patients with gunshot or stab wounds to the torso were randomised to receive crystalloid therapy before surgery, including during transport to the hospital (early), or to only receive ﬂuids during their surgical procedure (delayed). The randomisation was effective: the patients in the early ﬂuid intervention group received an average of 870 ± 667 mL of crystalloid ﬂuid in the pre-hospital phase of their resuscitation compared to an average of 92 ± 309 mL in the delayed resuscitation group (p < 0.001). Similarly, the volume of crystalloid administered after arrival at the trauma centre and before the surgery was also signiﬁcantly higher in the early intervention group compared to the delayed intervention group (1608 ± 120l vs. 283 ± 722 mL, respectively, p < 0.001). There was an 8% reduction in mortality in the group that only received ﬂuids during their surgical intervention compared to the early ﬂuid resuscitation group; patients in this group also had a signiﬁcantly shorter average hospital length of stay, without an increase in postoperative complications.

LR and HS more closely resemble plasma as they contain potassium, calcium, and lactate – with less sodium and chloride than 0.9% NS – and seemed reasonable alternatives for NS, especially for trauma patients. Indeed, LR was found superior to NS for haemorrhagic shock resuscitation since NS caused a more severe metabolic acidosis, worsened coagulopathy, and led to increased blood loss. However, LR still contributes to coagulopathy by hemodilution and does not provide oxygen-carrying capabilities.

COLLOIDS

Colloids are aqueous solutions that also contain electrolytes and organic macromolecules. These macromolecule constituents are unable to cross the endothelial membrane of the blood vessels, remaining within the intravascular space, exerting

34 | Fundamentals of Frontline Surgery

higher oncotic pressure than the electrolytes contained in crystalloids. Several types of colloids are in use, differing in the type of macromolecules contained in each. The most common options include albumin, hydroxyethyl starch (HES), gelatins, and dextrans. Despite the presumed rationale for colloid, compared with crystalloid use, the expected greater intravascular volume expansion was not shown to improve the prognosis of patients suffering from haemorrhagic shock. Furthermore, colloids were shown to increase kidney injury, impair immune function, and worsen coagulopathy.

TRANEXAMIC ACID

Tranexamic acid (TXA) inhibits the enzymatic breakdown of ﬁbrin blood clots (ﬁbrinolysis) and is expected to reduce bleeding. The CRASH 2 trial, a large prospective interventional trial, showed that in trauma patients suffering from major bleeding, early administration (under 3 hours from injury) of TXA reduces mortality. Subsequent analysis showed that delay in treatment (beyond 3 hours) increase mortality. The MATTERS study reinforced the results of the CRASH 2 trial, a retrospective analysis conducted on haemorrhaging combat casualties in a military hospital. The results of these studies led to widespread implementation of TXA administration both in prehospital scenario – by military and civilian systems – as well as in trauma bays. The recently published CRASH-3 study demonstrated that TXA is also effective in reducing mortality in patients with mild to moderate isolated traumatic brain injury.

HOW DO I STOP THINKING ABOUT THE FUTURE AND TREAT THE PATIENT NOW?

To provide casualties with optimal care, austere environment providers must not only overcome the challenge of choosing the ideal of the worst options available but also deal with the fact that the best resuscitative protocol is yet to be determined and supported by high-quality studies. One should treat patients using practical means – making sure that compressible bleeding has stopped, using a single

infusion bag at a time, aiming for a restored radial pulse, mental status, or systolic blood pressures – depending on the speciﬁc protocol used. These boluses are to be repeated if necessary.

The decision to use blood products is a medical decision and, in most countries, it must be made only by a physician. In an austere environment, the medical provider should have full knowledge of both the clinical situation and the availability of compatible blood products. Establishing a Walking Blood Bank (WBB) Program before treatment, based on risk assessment and potential for casualties, is recommended.

Patients in shock need resuscitation. Patients who have mechanisms of injury likely to produce shock (traumatic amputation, penetrating injury to the thorax or abdomen) will probably require transfusion prior to shock. Transfusions should be prioritised in patients clearly in shock and then to those who will need blood, based on injury patterns and volume lost, but who are not yet in shock. The goal, if resources permit, is to keep the latter patients out of shock:

⚫

Where and when possible – whole blood (fresh or stored)

⚫

Plasma, RBCs, and platelets in a 1:1:1 ratio

⚫

Plasma and RBCs at a 1:1 ratio

⚫

Any of the blood products available – RBCs/ plasma

⚫

Freeze-dried/reconstituted dried plasma

⚫

Combination of solutions with physiologic activity: Albumin + Fibrinogen concentrate

⚫

If all you have left is NS – Let’s face it, in the RDCR/austere environment context, if this is all you have, you better have some training in palliative care as well

WHENEVER SHOCK IS DIAGNOSED, ADMINISTER TRANEXAMIC ACID (TXA)

Administer 1 g of tranexamic acid in 100 mL Normal Saline or Lactated Ringers as soon as possible but NOT later than 3 hours after injury. When given, TXA should be administered over 10 minutes by IV infusion.

No Blood … What to Do? | 35

KEY POINTS

1. Follow preceding algorithm.

2. Initiate hypothermia prevention that should

occur along with treatment.

3. Blood products induce hypocalcemia. Treatment

should start early. Give 2 g CaCl or 6 g Ca gluconate EARLY (<4 U transfused).

4. Documentation.

5. Follow adverse effects.

5 Point-of-Care Ultrasound

INTRODUCTION

In mentioning the Resource-Limited Environment (RLE), we are narrowing our focus to pre-hospital care scenario with few resources or critical care conditions. These are usually clinical situations in remote or hard to reach areas, rescue in wild areas, battleﬁeld, and space ﬂights – among others. It is important to mention that one of the main missions of pre-hospital care in this scenario is to provide fast, high-quality care, and subsequently transport patients quickly from the remote site to deﬁnitive care, avoiding delays and negative outcomes.

To increase the quality of care in a distant/critical environment and reduce mortality, recent advances in point-of-care ultrasound (POCUS) in pre-hospital care stands out. Historically, POCUS has its ﬁrst reports of military use as a screening tool in harsh environments and remote locations. This fact is corroborated by articles and consensus statements that choose POCUS as a priority in the care of critically ill patients in this scenario. POCUS is, therefore, supposed to be focused on speciﬁc issues such as traumatic and nontraumatic acute pulmonary changes, presence of cavity ﬂuids, aetiology of shock and acute neurological damage—in other words, identiﬁcation of acute life-threatening conditions. While POCUS has several applications in austere environment, three protocols are the most comprehensive in this scenario: E-FAST, RUSH, and Optic Nerve Sheath Diameter (ONSD).

real-time images. However, one of the main reasons why healthcare providers working in austere environments should master POCUS is its portability and accuracy as a diagnostic tool. Indeed, the development of pocket-sized ultrasound machines has revolutionised the patients’ bedside assessment. Probes are now used as an extension of physical examination by trained physicians, enhancing diagnostic accuracy without the need for further testing. By applying POCUS as an adjunct to interventional procedures, patients can be more safely managed. POCUS outperforms conventional radiographs in several lifethreatening situations in terms of diagnostic accuracy, while displaying portability and procedure-guidance advantages. Computerised tomography (CT) yields better results in terms of diagnostic accuracy, although it presents several cumbersome features such as the use of ionising radiation, the need to transport patients to dedicated suites, higher costs, and greater equipment size. These features render POCUS an invaluable tool in the assessment, management, and triage of patients in remote locations.

In an RLE, triage decisions are critical. Scarce resources push healthcare providers to make decisions based on the best evidence available. In that sense, POCUS offers advantages with its wide range of applications in the ﬁelds of Emergency, General Surgery, and Trauma, as an adjunct for life-saving decision-making. It is a small, pocket-size machine which provides excellent diagnostic and interventional results.

RESOURCE LIMITATION CONCERN

POCUS has gained widespread utilisation due to its several advantages over other image gadgets. It is lowcost, does not expose patients to radiation, and yields

BRIEF REVIEW OF MATERIAL

In an RLE scenario, portability and size matter. There are several ultrasound machines with such

38 | Fundamentals of Frontline Surgery

characteristics in the market. It is also important to bear in mind the basic ultrasound principles, temperature and battery concerns, and the speciﬁcations of each transducer. The principles of ultrasound are not the scope of this chapter and can be found in several textbooks and articles. Due to climate extremes, it is imperative to optimise storage and usage requirements to reduce the impact of extreme environmental conditions on equipment functionality and durability. Since each transducer has its own characteristics and advantages, having only one probe available may jeopardise a broader applicability of point of care ultrasound. Ideally, at least two probes—a low- and a high-frequency transducer—should be available to make the most of this tool in the frontline. Normally, the linear probe exhibits a 7–12 MHz frequency and is ideal for superﬁcial structures scanning and procedures such as foreign objects identiﬁcation, soft tissue evaluation, and vascular accesses. The low-frequency (3–5 MHz) probes, such as the curvilinear or the phased array, are used to evaluate deep structures and to guide interventional procedures. Hence, E-FAST should be performed using these probes.

Box 5.1 Essentials of Austere Environment POCUS

RESOURCE-LIMITED ENVIRONMENT POCUS

E-Fast

The Extended Focused Assessment Sonography for Trauma (EFAST) evaluation aims to identify free intraperitoneal ﬂuid, pericardial effusion, and pneumothorax or haemothorax in trauma patients. To perform the E-FAST exam, the physician should use a curvilinear or phased array transducer to evaluate the four abdominal views and four thoracic views (apex and basal views, bilaterally). The clinician may choose to use a higherfrequency linear probe to evaluate the thoracic windows, as it yields sharper images of superﬁcial structures.

HOW TO PERFORM THE EXAM

To obtain a good subxiphoid view, the examiner should place the transducer horizontally, almost parallel to the skin (Figure 5.1C and Video 5.1: Subxyphoid). The optimal image will show liver parenchyma between the skin and the right ventricle (the most anterior cardiac chamber). All cardiac chambers are displayed in an almost complete coronal view, and the physician may search for pericardial ﬂuid anteriorly or posteriorly.

⚫

Clinical situations in remote or hard to reach areas, rescue in wild areas, battleﬁeld, space ﬂights among others are deﬁned as remote/austere environment. Such scenarios demand fast and objective evaluation using portable equipment.

⚫

POCUS use on the military frontline should initially focus on life-threatening conditions. Therefore, E-FAST, RUSH, and ONSD are the essential applications of POCUS.

⚫

POCUS has a wide range of applications that may help the clinician make critical decisions based on the best available evidence in low-resource settings.

⚫

At least one high- and one low-frequency transducer should be available to perform the essential applications of POCUS.

VIDEO CONTENT

The videos referenced in

this chapter can be accessed at https://www.routledge.com/ 9780367435592, under Support Material, or by viewing the QR code to the left.

The hepato-renal space (Morrison’s Pouch) may be evaluated by putting the probe longitudinally at the level of the 11th–12th rib on the midaxillary line. It is important to scan the whole hepato-renal surface, as ﬂuid may accumulate at the tip of the inferior margin of the liver (Figure 5.1A; Video 5.2: Morrisons positive). Approximately 70% of the positive FAST exams will display free ﬂuid in this space. The physician may also look for ﬂuid in the suprahepatic space.

Hepatorenal view (RUQ)

Coronal section

Subxiphoid pericardial view

Coronal section

Suprapubic view

Transverse section

(perpendicular to skin)

Rotate probe

in place

Suprapubic view Sagittal/longitudinal section (perpendicular to skin)

Parasternal pericardial view Long axis section

Splenorenal view (LUQ) Coronal section

Figure 5.1

VIDEO CONTENT

The splenorenal space is evaluated similarly, but slightly cranially (10th–11th rib) and posteriorly (Figure 5.1B; Video 5.3: Splenorenal positive). It is imperative to scan the subdiaphragmatic region on this side, as ﬂuid accumulates in that space more often than in the splenorenal.

The pelvic window is obtained by placing the transducer horizontally, 1–2 cm above the pubis. The examiner should basculate the transducer caudally in approximately 45° to facilitate the bladder visualisation. One should scan the whole bladder surface to minimise missing a positive exam (Figure 5.1D). The physician may also perform this evaluation with the transducer in the longitudinal position, obtaining a sagittal view of the bladder.

The thoracic views of the E-FAST may be more cumbersome, although the results are more reliable.

Point-of-Care Ultrasound | 39

POCUS can identify tiny amounts of ﬂuid in the thoracic cavity, and the interpretation of the exam is similar to the abdominal views (anechoic images

The videos referenced in this

chapter can be accessed at https://www.routledge.com/ 9780367435592, under Support Material, or by viewing the QR code to the left.

representing ﬂuid surrounded by structures with different echogenicity). However, while looking for pneumothorax, the healthcare provider should also be familiar with lung ultrasound artefacts. It is imperative to evaluate sings such as lung sliding, A-lines and B-lines, and actively look for the lung point, in cases where pneumothorax may be a differential diagnosis. Studies show that POCUS outperforms chest radiographs, with an 86–100% sensitivity and a 92–100% speciﬁcity for the diagnosis of pneumothorax, making it an excellent tool for ruling out that condition. When analysing the diagnostic performance of ultrasound to identify pleural effusion, evidence shows a sensitivity of 82–94% and a speciﬁcity of 97%, also outperforming chest X-rays. Moreover, ultrasound can be used to follow stable patients undergoing unpressurised aircraft transfer.

RUSH (Rapid Ultrasound for Shock)

The RUSH protocol is a complete and fast-running protocol that assesses the various probable causes of shock. It divides shock assessment into three broad

40 | Fundamentals of Frontline Surgery

groups: the pump, the tank, and the pipes. The ‘pump’ is the part that corresponds to the cardiac evaluation; the ‘tank’ represents the evaluation of the lung, the great vessels and the abdomen, and the ‘pipes’ stand for the vessels, more speciﬁcally the aorta and femoral vein. The protocol recommends the use of two probes—the phase matrix (3.5–5 MHz) for thoracoabdominal evaluation and the linear matrix (7.5–10 MHz) for venous and pneumothorax evaluation.

PUMP EVALUATION

For this evaluation, four cardiac ultrasound windows are used: parasternal long and short axis, apical, and subxiphoid. The ﬁrst is obtained by placing the phased array transducer at the level between the third and ﬁfth ribs, with the probe marker pointing to the right shoulder (Videos 5.4–

5.7). This view will provide an adequate evaluation of the left ventricle, the interventricular septum, and the aortic and mitral valves. The optimal view is obtained when the image displays the right ventricle outlet and descending aorta. The parasternal short axis view is obtained by rotating the probe 90° clockwise, aiming the probe marker to the left shoulder of the patient. This view displays the relationship between the left and the right ventricles and may be used to estimate the contractility of the former when visualising both papillary muscles. The apical view is obtained by placing the transducer horizontally at the tip of the heart, yielding a coronal view of the four chambers. As such, the physician can assess size, contractility, presence of pericardial effusion, or intracardiac thrombi. The last view is the subxiphoid, the same sonographic window present in the FAST exam.

VIDEO CONTENT

The videos referenced in this

chapter can be accessed at https://www.routledge.com/ 9780367435592, under Support Material, or by viewing the QR code to the left.

In the cardiac evaluation, the RUSH protocol recommends the evaluation of three variables: pericardial effusion, left ventricular dysfunction, and right ventricular dysfunction. Thus, it is possible to identify three plausible causes of shock—cardiac tamponade, myocardial ischemia, and pulmonary hypertension with right ventricular involvement. Through these windows, it is possible to evaluate the pericardium, conﬁrm or rule out the presence of cardiac effusion and tamponade, evaluate the contractility of both ventricles, and estimate the degree of dysfunction. If present, left dysfunction is suggestive of myocardial ischemia, while right dysfunction suggests pulmonary hypertension as a result of possible embolism. In the latter, a massive event may result in enlarged right cardiac chambers and a leftward insinuation of the interventricular septum.

TANK EVALUATION

The tank is composed of the lungs, abdomen, and large vessels known to be reservoirs of blood. During this evaluation, the thoracic cavity is evaluated for pneumothorax or pleural effusion, following the same principles as the E-FAST exam. The thoracic evaluation should also aim to identify patients with pulmonary oedema. This can be achieved by observing B-lines at the intercostal spaces, which arise due to interlobular septal thickening. These lines are sonographic artefacts due to reverberation of the sound waves. B-lines are hyperechoic and bright images that arise from the pleural line and stream downwards to the end of the image. They are different from the ‘comet tail’ artefact, which are more commonly distributed along the pleural line and are not as long as the B-line. The presence of B-lines, especially of more than three in an intercostal space, is often pathological and may be associated with pulmonary oedema when diffused, or focal pathologies if more restricted (i.e. pneumonia) (Video 5.7). It is important to note that the number of B-lines and intercostal spaces displaying this sonographic sign is associated with the severity of the condition and can be used to evaluate the clinical response to treatment.

In the abdominal part, FAST is performed to search free ﬂuid in the cavity, indicating leakage in

Point-of-Care Ultrasound | 41

the tank. This examination may be useful for patients in remote scenarios (to facilitate decisionmaking), immediate postoperative period of an abdominal surgery (i.e. frontline surgery team), or those recovering in the ICU bed who develops persistent hypotension.

In relation to the great vessels, the inferior vena cava (IVC) will be evaluated to deﬁne its collapsibility during the breathing cycle and yield an estimate of intravascular volume – whether the patient will respond to volume infusion. The IVC view may be obtained by placing the curvilinear or phased array transducer longitudinally in the epigastric or right ﬂank (like the e-FAST view) areas. The optimal view should display the IVC and the right atrium inlet. The identiﬁcation of the ‘kissing walls’ sign (i.e. when the IVC collapses until its walls touch each other) should be interpreted as hypovolemia in an adequate clinical context, especially when the available cardiac windows corroborate this ﬁnding. Studies demonstrate a positive correlation between IVC measurements and central venous pressure (CVP). IVC measurements are better performed using the Mmode to identify the inspiratory and expiratory phases of ventilation. It is important to complement the IVC evaluation with a horizontal view of the vessel to avoid underestimation due to cylinder effect. The collapsibility index is calculated dividing the IVC diameter during inspiration and by its diameter during expiration. Roughly, ≤2 cm IVC with ≥50% collapsibility correlates with a CVP of less than 10 mmHg. When the IVC diameter is ≥2 cm displaying <50% collapse during inspiration, the estimated CVP is higher than 10 mmHg. These measurements may also be used to monitor clinical response to treatment.

PIPE EVALUATION

The pipes will be evaluated for aneurysm, dissection, and rupture of the aorta by scanning the sites with the highest incidence of these abnormalities—the suprasternal, parasternal, epigastric, and supraumbilical. The ideal transducer for this assessment is the phased array, and the examiner may identify aortic enlargements, intraluminal ﬂaps, and periaortic hematomas. The aorta is evaluated by placing the probe in at least four regions. The aortic root is visualised by placing the transducer horizontally on the suprasternal area. The

physician should then obtain a parasternal long-axis view to evaluate the descending aorta. Further down, the examiner should place the transducer horizontally in the epigastric and periumbilical areas to cover the abdominal aorta. Abdominal compression may be necessary to obtain a clearer image of the aorta by displacing intraluminal gas. Since most of the aortic ruptures and hematomas are in the retroperitoneum, this speciﬁc evaluation may be limited with ultrasound. However, the presence of aortic aneurysm in a hypotensive patient should prompt the need for urgent investigation of a possible rupture. The sensitivity of ultrasound to detect aortic aneurysms vary from 93–100%. Aortic dissection may be identiﬁed by aortic root enlargement or an intimal ﬂap. The suprasternal, parasternal long axis, epigastric, and periumbilical views may cover the most common areas of dissection. By using the colour Doppler, it may be possible to identify two distinct lumens in some cases.

In the venous part, healthcare providers will evaluate the femoral and the popliteal veins with the linear transducer, actively searching for thrombi. The examiner should start by obtaining a transverse view of the common femoral vein just below the inguinal ligament, followed by images of the superﬁcial femoral vein distally to the great saphenous vein conﬂuence. The examiner should then pursue a transverse view of the popliteal vein in the posterior aspect of the knee. The transverse view facilitates identiﬁcation of the vessel, but the examiner should also use the longitudinal view. There are three key features associated with intraluminal thrombi: absence of collapsibility during compression, presence of a hyperechoic intraluminal material, and absence of ﬂow on colour imaging. The evaluation of the pipes may help manage the patient who will be urgently operated on and has a risk factor for thrombosis. The evidence of thrombi may help the clinician to decide, for example, whether to place a vena cava ﬁlter prior to the operation.

Optic Nerve Sheath Diameter (ONSD)

The gold standard for diagnosing high intracranial pressure (ICP) after a traumatic brain injury (TBI) is through the insertion of an intraventricular catheter that allows ICP monitoring. However, it is an invasive method not universally available, and associated with complications such as infection,

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PACKED RED BLOOD CELLS

PLASMA

CRYSTALLOIDS

COLLOIDS

TRANEXAMIC ACID

HOW DO I STOP THINKING ABOUT THE FUTURE AND TREAT THE PATIENT NOW?

WHENEVER SHOCK IS DIAGNOSED, ADMINISTER TRANEXAMIC ACID (TXA)

KEY POINTS

FURTHER READING

5 Point-of-Care Ultrasound

INTRODUCTION

RESOURCE LIMITATION CONCERN

BRIEF REVIEW OF MATERIAL

RESOURCE-LIMITED ENVIRONMENT POCUS

E-Fast

HOW TO PERFORM THE EXAM

RUSH (Rapid Ultrasound for Shock)

PUMP EVALUATION

TANK EVALUATION

PIPE EVALUATION

Optic Nerve Sheath Diameter (ONSD)