Ebook Paediatric intensive care: Part 1

(BQ) Part 1 book Paediatric intensive care presents the following contents: General introduction to paediatric intensive care, organ system support and related practical procedures.

OXFORD MEDICAL PUBLICATIONS Paediatric Intensive Care Oxford Specialist Handbooks published and forthcoming Oxford Specialist Handbooks in General Oxford Specialist Neurology Handbooks Epilepsy A Resuscitation Room Guide Parkinson’s Disease and Other Addiction Medicine Movement Disorders Hypertension Stroke Medicine Perioperative Medicine, Second Edition Oxford Specialist Handbooks in Post-Operative Complications, Paediatrics Second Edition Paediatric Dermatology Pulmonary Hypertension Paediatric Endocrinology and Renal Transplantation Diabetes Oxford Specialist Handbooks in Paediatric Gastroenterology, Anaesthesia Hepatology, and Nutrition Paediatric Haematology and Cardiac Anaesthesia Oncology Day Case Surgery Paediatric Intensive Care General Thoracic Anaesthesia Paediatric Nephrology Neuroanaethesia Paediatric Neurology Obstetric Anaesthesia Paediatric Palliative Care Paediatric Anaesthesia Paediatric Radiology Regional Anaesthesia, Paediatric Respiratory Medicine Stimulation and Ultrasound Techniques Oxford Specialist Handbooks in Psychiatry Oxford Specialist Handbooks in Cardiology Child and Adolescent Psychiatry Old Age Psychiatry Adult Congenital Heart Disease Cardiac Catheterization and CoroOxford Specialist Handbooks in nary Intervention Radiology Cardiac Electrophysiology Interventional Radiology Cardiovascular Magnetic Resonance Musculoskeletal Imaging Echocardiography Pulmonary Imaging Fetal Cardiology Heart Failure Oxford Specialist Handbooks Nuclear Cardiology in Surgery Pacemakers and ICDs Cardiothoracic Surgery Valvular Heart Disease Colorectal Surgery Hand Surgery Oxford Specialist Handbooks in Liver and Pancreatobiliary Surgery Critical Care Operative Surgery, Second Edition Advanced Respiratory Oral Maxillofacial Surgery Critical Care Otolaryngology and Head and Oxford Specialist Handbooks in Neck Surgery End of Life Care Paediatric Surgery Plastic and Reconstructive Surgery End of Life Care in Dementia Surgical Oncology End of Life Care in Nephrology End of Life in the Intensive Care Urological Surgery Vascular Surgery Unit Oxford Specialist Handbooks in Paediatrics Paediatric Intensive Care Edited by Peter Barry Consultant in Paediatric Intensive Care, University Hospitals of Leicester NHS Trust, Honorary Senior Lecturer, Department of Child Health, University of Leicester, UK Kevin Morris Consultant in Paediatric Intensive Care, Birmingham Children’s Hospital, Honorary Senior Lecturer, University of Birmingham, UK Tariq Ali Consultant in Paediatric Intensive Care and Anaesthesia, John Radcliffe Hospital, Honorary Senior Lecturer, Oxford University, Oxford, UK With Special PICU Nursing Advisor Yvonne Heward 1 Great Clarendon Street, Oxford OX2 6DP Oxford University Press is a department of the University of Oxford It furthers the University’s objective of excellence in research, scholarship, and education by publishing worldwide in Oxford New York Auckland Cape Town Dar es Salaam Hong Kong Karachi Kuala Lumpur Madrid Melbourne Mexico City Nairobi New Delhi Shanghai Taipei Toronto With offices in Argentina Austria Brazil Chile Czech Republic France Greece Guatemala Hungary Italy Japan Poland Portugal Singapore South Korea Switzerland Thailand Turkey Ukraine Vietnam Oxford is a registered trade mark of Oxford University Press in the UK and in certain other countries Published in the United States by Oxford University Press Inc., New York © Oxford University Press, 2010 The moral rights of the author have been asserted Database right Oxford University Press (maker) First published 2010 All rights reserved No part of this publication may be reproduced, stored in a retrieval system, or transmitted, in any form or by any means, without the prior permission in writing of Oxford University Press, or as expressly permitted by law, or under terms agreed with the appropriate reprographics rights organization Enquiries concerning reproduction outside the scope of the above should be sent to the Rights Department, Oxford University Press, at the address above You must not circulate this book in any other binding or cover and you must impose this same condition on any acquirer British Library Cataloguing in Publication Data Data available Library of Congress Cataloging in Publication Data Data available Typeset by Glyph International, Bangalore, India Printed in China on acid-free paper by Asia Pacific Offset ISBN 978–0–19–923327–4 10 Oxford University Press makes no representation, express or implied, that the drug dosages in this book are correct Readers must therefore always check the product information and clinical procedures with the most up-to-date published product information and data sheets provided by the manufacturers and the most recent codes of conduct and safety regulations The authors and publishers not accept responsibility or legal liability for any errors in the text or for the misuse or misapplication of material in this work v Preface In writing this book, we have aimed to provide a comprehensive, practical guide to the care of the critically ill child, both on an intensive care unit and in other clinical areas—wherever children need to be stabilized and failing organ systems need to be supported Throughout, we have tried to stick to the underlying principles that guide us in everyday practice—the application of applied physiology; an understanding of disease processes; a reckoning of what is likely and what is possible; and the provision of care driven by compassion for our patients and their families The book is not just for intensivists and intensive care trainees We hope that it will help clinicians who provide care to sick children outside the intensive care unit as well, in emergency departments, on paediatric wards and adult units that are occasionally asked to support a critically ill child Of course, we hope that it will also prove to be a useful resource for doctors and nurses who work in intensive care, either as specialists or on rotation It is a book to be picked up to find the answers to specific problems and for guidance on how to manage specific issues Where appropriate, we have tried to provide more in-depth information, highlighting areas of controversy and stimulating further reading The preparation of the book has been made easy by the work of the various contributors, who delivered chapters on time and to length They are listed on page xv We hope that in editing their work we have not taken too many liberties Whilst writing the handbook, we were saddened by the deaths of Heinrich Werner and David Todres, colleagues who we hoped would contribute and comment on our work Children’s intensive care, and this handbook, are less without them We thank Julie Edge, James Greening, and David Luyt for their comments and help with specific chapters We would also like to thank Susan Crowhurst, Anna Winstanley, and Helen Liepman at the Oxford University Press for keeping us on track and seeing the project through from conception to publication Finally, we thank our families for their support and forbearance PWB, KM, TA Oxford, Leicester, and Birmingham, 2009 vi SUBJECT OF THIS PAGE Additional disclaimer We have checked all drugs and dosages suggested in this handbook, but the ultimate responsibility for their use in a particular patient rests with the prescriber vii Foreword The specialty of paediatric critical care medicine has come of age When it began to emerge as a specialty in its own right in the 1970s, much of what was done was learnt from adult intensive care medicine Paediatric intensive care units (PICUs) were largely run by anaesthetists because they were the experts in airway and ventilation management and understood cardiac and respiratory physiology In those days, diseases like Reye syndrome and Haemophilus influenzae acute epiglottitis were diseases that presented unique challenges to those involved in paediatric critical care, where the use of recently introduced invasive monitoring and skilful airway management could dramatically influence survival It also saw the dawn of a new era in surgery for congenital heart disease which saw major improvements in survival and the eventual evolution of paediatric cardiac critical care as a specialty Thirty years ago, little of the evidence for the therapies we used was ever subjected to the rigor of clinical trials, there was little formalized training, and paediatric critical care was a part-time specialty Much has changed Many countries have established formalized training schemes with specialty examinations, full-time career intensivists with academic positions are being appointed, and the specialty has its own journal There are also a number of published textbooks in paediatric critical care medicine Do we need another and, if so, how is Paediatric Intensive Care different? The answer is yes, we do, if it presents knowledge in a different and more accessible format I particularly appreciate the way it deals with the important issues in an abbreviated arrangement which presents knowledge in an easily accessible layout It has a comprehensive coverage of the important physiological principles and, as someone from the previous era where anaesthesia was the entry into PICU, I am pleased to see that prominence is given to airway management and the use of anaesthetic drugs We are entering a new era in the specialty where what we will be judged by our results The public and profession are rightly less tolerant of errors and less than optimal care At the same time the intensive care specialist is dealing with increasing amounts of new knowledge which he or she has to absorb in a very demanding clinical specialty Having access to a reference source such as Paediatric Intensive Care which gives them vital information presented in such an easy to navigate format will make that task less burdensome Desmond Bohn MB MRCP FRCPC FFARCS Professor of Anaesthesia and Paediatrics University of Toronto; Chief, Department of Critical Care Medicine The Hospital for Sick Children, Toronto, Canada This page intentionally left blank ix Acknowledgement We would like to thank Mr David Barron for providing the illustrations for the cardiac lesions described in Chapter 20 332 CHAPTER 19 Imaging in paediatric intensive care Standard radiography Radiological imaging has a major role in patient assessment in PICU, as clinical examination may be limited by patient position, noise from ventilators, alarms, or the environment, and the presence of wounds, drains, or dressings Chest X-ray (CXR) • The CXR is the commonest radiologic modality in use and is suitable for intensive care, offering rapidity, portability, and a reasonable diagnostic yield for most clinical questions raised in critically ill patients • Bedside chest films should include the upper trachea and larynx, as well as lung bases and upper abdomen The patient should be well centred and all lines and artefacts should be removed from the surface of the chest The degree of inspiration and rotation should be considered and the degree of flexion/extension of the neck noted with respect to interpretation of ETT position • Neck flexion will advance the ETT down the trachea • Routine daily chest radiography has a high prevalence of findings but less frequently leads to management changes in the absence of clinical signs and is therefore not recommended • Equally an intubated critically ill patient with lines and tubes should not go for days without a CXR Indications • On admission, particularly following cardiac surgery (Box 19.1) • Post-intubation or following placement or an internal jugular or subclavian central venous catheter • To identify position of NG tube if other methods fail • Investigation of clinical signs (abnormal chest movement, air entry, adventitious sounds) • Clinical suspicion of pneumothorax • Following thoracocentesis with or without drain insertion • Increasing oxygenation or ventilation requirement • Fever and changes in endotracheal secretions or inflammatory markers suggesting infection • Follow up of known intrathoracic disease Placement of medical devices • ETTs may be malpositioned in up to 10% ETT tip should be located midway between clavicles and carina • Endobronchial intubation may result in overinflation of ipsilateral lung and atelectasis of contralateral lung or in air leak, i.e pneumothorax, pneumomediastinum, or SC emphysema • CXR should include upper abdomen to verify intragastric position of NG tubes (NG tubes must have radio-opaque portion) • Chest drain position after insertion for pneumothorax or effusion may appear acceptable but may be intraparenchymal, in extrathoracic soft tissue, or sandwiched in a lung fissure Absence of respiratory swing, failure to withdraw fluid, lack of bubbling, and/or clinical signs of ongoing air leak or fluid collection should raise suspicion STANDARD RADIOGRAPHY • Routine X-ray after removal of chest drains has a low yield in the absence of clinical signs • Re-expansion pulmonary oedema may be seen after drain placement for effusion or pneumothorax • Central venous catheter placement may be complicated by pneumothorax (seen with subclavian lines more commonly than jugular), malposition, the wrong trajectory, or haemothorax Assessment of airways and lung parenchyma • Pneumothorax: notoriously difficult to identify if anteromedial, subpulmonic, or loculated; the size on plain film correlates poorly with clinical significance May appear only as sharper cardiac or diaphragmatic outlines and may require CT scan for confirmation Mediastinal air may cross the midline or extend into the neck or abdomen • Effusions: may be difficult to quantify or localize and may appear only as uniform haze or opacification Costophrenic angles generally obscured • Pulmonary oedema: cardiogenic is associated with cardiomegaly, vascular prominence, or redistribution, and may be more uniform in appearance Non-cardiogenic, usually due to icapillary permeability (ARDS), is patchy, lacks cardiovascular changes, and may be associated with air bronchograms • ARDS: poor correlation between radiologic changes and clinical condition but useful when new consolidation noted or to follow progress Alveolar opacification without cardiomegaly is characteristic Associated findings include atelectasis and barotrauma with evidence of air leak • Viral pneumonitis: interstitial changes common with peribronchial thickening Commonly associated with atelectasis due to endobronchial plugging and poor collateral air flow • Basal opacities are common but the extent of the abnormality may be underestimated on plain X-rays Loss of hemidiaphragmatic outline suggests lower lobe pathology • Whole lung ‘white-out’ is rarely consolidation; more likely to be atelectasis or effusion/empyema.(but not if develops acutely) • The majority of air space opacities in ventilated patients are not pneumonia Box 19.1 The postoperative CXR after cardiac surgery • Provides baseline assessment of mediastinum, heart shape and size • Identify and localize ETT, central venous and atrial catheters, drains, pacing wires, clips, and other intrathoracic devices • Assess lung fields for atelectasis, or opacification suggestive of contusion Infective consolidation unlikely in first 48h • Pleural fluid likely to be haemothorax in early postoperative period; transudate common when pulmonary venous pressures remain high or fluid overload Chylothorax should be ruled out when persistent 333 334 CHAPTER 19 Imaging in paediatric intensive care Table 19.1 CXR signs Collapse (atelectasis) Consolidation Commonest cause of opacification, especially LLL, RUL May occur in any lobe Loss of volume generally secondary to bronchial obstruction No loss of volume: airspaces filled with exudate, oedema or blood Mediastinal shift towards collapse Mediastinal shift uncommon Segmental, lobar or whole lung Patchy, homogenous, or irregular; lesions contiguous to heart or diaphragm associated with loss of that border Central location Peripheral, abutting fissure or pleura No air bronchograms Air bronchograms common as air-filled bronchi outlined against fluid-filled alveolar spaces Changes evolve rapidly Changes evolve more slowly LLL, left lower lobe; RUL, right upper lobe Abdominal X-ray • Relatively few indications on PICU • Main indication to rapidly rule out perforation or bowel obstruction at bedside but may give insufficient information as an isolated investigation • NG or nasojejunal tube placement may be confirmed • Bowel wall thickening non-specific and frequent in critically ill patients • Gas pattern should be described • Gastric dilatation frequently seen after mask ventilation or with CPAP • Air or fluid in the abdomen compress viscera centrally • Free air suggests bowel perforation but difficult in supine patient Lateral views (‘shoot through’) may be required • Paralytic ileus causes widespread bowel loop distension with loops of colon greater in calibre than small bowel, or can be gasless • Small bowel distension secondary to obstruction may have a more organized ‘stepladder’ appearance Computed tomography • Computed tomography (CT) scanning remains one of the most useful modalities in the ICU, due to its availability and ability to provide detailed cross sectional images of the brain, chest, and abdomen Technological advances with higher resolution and reduced scanning times have made it an integral part of the emergency management of the patient with trauma and other acute intracranial, intrathoracic, and intra-abdominal emergencies • Multiplanar reconstruction using volumetric data to convert axial to 3D images, is particularly applicable to the study of vascular and tracheo-bronchial structures COMPUTED TOMOGRAPHY • The pitfalls of CT scanning are related mainly to the need for transfer from the intensive care department In an extremely unstable patient one may have to weigh the risks of transfer against the findings of the scan Chest • Helical CT with rapid multislice systems provides continuous volume data that can then be reconstructed to study mass lesions, vascular anatomy, mediastinal and airway disease, lung parenchyma • Rapid scanning minimizes or eliminates respiratory artefact • Most investigations use IV contrast and images acquired within seconds of contrast injection provide angiographic detail and information on anatomy and thromboembolic disease • CT angiography permits visualization of central and peripheral vascular structures and their relationship to tracheo-bronchial tree and lung parenchyma Reconstructed images can produce virtual 3D images of vascular tree and may replace the need for conventional angiography • High-resolution CT with non-contiguous slices is more suitable for diffuse disease and provides detailed images of the lung parenchyma and pleura at lower radiation dose • May be helpful when oxygenation and ventilatory requirements unexplained by plain X-rays or echocardiography • Trauma: essential part of the workup of patients with blunt trauma where airways or major vascular structure injury is suspected • ARDS: demonstrates non-uniformity of disease and changes seen when position changed from prone to supine with associated gravity-dependent atelectasis New changes identified may signify superimposed infection Bronchial dilation and subpleural cysts associated with prolonged ventilation may be seen • Pulmonary oedema: cardiogenic oedema can be differentiated from non-cardiogenic oedema due to capillary leak by the prominent interlobular septal thickening and vascular enlargement seen in the former • Pleural effusion: size and character of loculated effusions may be better ascertained with CT • Pneumothorax: if loculated, anterior or subpulmonic, CT provides information to guide drainage • Pulmonary embolus: CT-angiogram is imaging modality of choice to identify central and segmental emboli which may be missed on US • Abscess: distribution and character of abscesses well seen, often localized to upper lobes in immunocompetent and more diffuse and multilobar in immunocompromised children Peripheral lung lesions can be differentiated from empyema • CT-guided diagnostic and interventional procedures may avoid surgical intervention • Virtual bronchoscopy: 3D reconstruction provides detailed images of large and small airways and enables highly accurate measurement of airway calibre and visualization of focal stenoses • 3D-CT has the advantage of non-invasively seeing ‘beyond’ areas of airway obstruction, unlike bronchoscopy, and examines the relationship of the airways to extra-luminal structures, including mediastinal vessels and lymph nodes 335 336 CHAPTER 19 Imaging in paediatric intensive care Abdomen • Abdominal CT is an integral part of the initial workup of the patient with serious trauma to rapidly identify intra-abdominal injury • Haemodynamically unstable patients may not be amenable to CT and require urgent bedside US and/or rapid surgical intervention • Injury to the liver and spleen are common and easily identified on CT • Retroperitoneal structures well seen on CT including haemorrhage and pancreatic pathology • Oral contrast is useful to delineate viscera and IV contrast to identify vascular, infectious, or inflammatory pathology • Major role in identification of non-traumatic intra-abdominal pathology, generally difficult to assess clinically in the critically ill patient • CT indicated when intra-abdominal or retro-peritoneal sepsis suspected, i.e fever, cardiovascular instability, and metabolic acidosis unexplained by clinical examination, plain radiography, and US Abscesses, ischaemia, or infarction can be ruled out • CT-guided drainage for diagnosis and treatment may avoid surgical intervention Brain (See b Chapters 22 and 23.) CT remains the imaging modality of choice in acute traumatic and nontraumatic brain injury/encephalopathy Contrast enhancement is not routinely required for acute brain injury but is used to address specific diagnostic questions, i.e the presence and characteristics of infectious, inflammatory, or malignant lesions These include meningitis, abscesses, malignancies, and vascular malformations Further study with MRI or angiography is often required in these cases • Major advantages include rapid access and rapid study time to establish intracranial pathology requiring early neurosurgical intervention • Intracranial haemorrhage, i.e intraparenchymal, subdural, extradural and subarachnoid haemorrhage are well seen on CT Basal and orbital skull fractures are also identified • Raised ICP may be present in severely brain-injured patients even when an early CT scans is reported as ‘normal’ • CT does not necessarily exclude raised ICP • Routine repeat CT after traumatic brain injury is rarely indicated, and is infrequently associated with the need for neurosurgical intervention in the absence of clinical change • Repeat scanning should be directed by clinical parameters and ICP monitoring: • Changes in level of consciousness • Focal or persistent neurological abnormalities • Intractable intracranial hypertension • Seizures and haemodynamic changes suggestive of raised ICP • Patients with non-traumatic neurologic pathology presenting with altered level of consciousness, seizures, or focal signs are generally assessed initially with CT scan COMPUTED TOMOGRAPHY • Space-occupying lesions, cerebral oedema, and parenchymal changes associated with metabolic disease may be visible on early CT and direct initial management and the need for further imaging Box 19.2 Evaluation of the spine in trauma • Clinical evaluation in the obtunded, intubated child is unreliable and radiographic study essential • Plain radiography may be limited in detecting cervical spine fractures, especially at the levels of C1–C2 and C7–T1 • Dynamic fluoroscopic examination of the cervical spine is no longer standard practice • Standard CT studies limited to axial images may potentially miss abnormalities in translation, angulation, and rotation • CT with reconstructed multiplanar images is the imaging modality of choice to rule out spinal injury with rapid studies readily performed at the time of initial trauma work-up • ‘Reformatted’ or reconstructed CT images enable better assessment of these variations and provide indirect evidence of ligamentous injury when bony misalignment or malrotation is present High resolution images may reveal small avulsion fractures • MRI is superior at detecting abnormalities of alignment, spinal cord integrity, and ligamentous and soft tissue injuries However, high sensitivity may make non-specific abnormalities difficult to interpret clinically • MRI is rarely indicated or available in the emergency situation but may be indicated when clinical examination, X-ray, or CT scanning suggest ligamentous or cord injury, or instability • Plain radiography is generally adequate for thoracic and lumbar spine but CT scan can image the entire spine rapidly with minimal motion artefact Axial slices with reformatted and reconstructed views are commonly obtained at the time of initial CT of brain, chest, and abdomen Fluoroscopy • Fluoroscopy has a number of uses—it generally requires transporting the patient to the radiology department, though portable units exist • Tracheobronchography with non-ionic water-soluble contrast may provide information about dynamic tracheobronchial disease: • The patient must be spontaneously breathing through an ETT or tracheostomy • Images are acquired in >1 plane after injection of a small volume of contrast into the trachea • Imaging is repeated as different levels of positive pressure are applied, assessed with a manometer incorporated into the circuit • The degree of collapse of the trachea and bronchial tree are recorded and the reversibility with PEEP noted • Screening a post-pyloric feeding tube into position • Assessing diaphragmatic excursion when paralysis is suspected —US is generally used as first-line investigation (see b p.338) 337 338 CHAPTER 19 Imaging in paediatric intensive care Ultrasound US is used as a diagnostic tool and to aid in specific therapy Echoes or reflections of the US beam from tissues with different acoustic properties yield information on size, shape, and structure of organs and body spaces US has an increasing role in the early assessment of the unstable trauma patient, with its capacity to examine multiple systems at one time at the bedside Although less sensitive than CT in trauma and surgical emergencies, it may be useful when CT is unavailable or delayed Advantages • Portability • Enables rapid bedside analysis in real time and follow-up • Avoids the risks associated with transporting the critically ill child to the radiology suite • Increases the yield and decreases the complications of several interventional procedures, e.g central line placement • May guide or decrease the need for surgical intervention • No use of ionizing radiation Limitations to optimal acoustic windows • • • • • • • • Inadequate patient positioning Dressings, wounds, or drains interfering with probe angle Excessive fat Air and bone reflect US, limiting use in chest and musculoskeletal system Structures surrounded by bone are not generally visible Gas in hollow intra-abdominal organs may obscure deeper structures Mechanical ventilation with hyperinflation of lungs, pneumothorax, or SC air may obscure views Depends on operator experience and skill Chest • Superior to CXR for identification of small or loculated effusions • Estimates volume of effusion and need for drainage better than X-ray • Defines the character of the fluid, the presence of loculation and septations, and may suggest aetiology • Distinguishes between effusion and collapse/consolidation • Enables some assessment of lung parenchyma deep to effusions or air • Useful to quantify direction and adequacy of diaphragmatic excursions Diaphragm • Phrenic nerve injury is relatively common after cardiac surgery • The affected hemidiaphragm may be paralysed, or move paradoxically when lack of tone causes the hemidiaphragm to move cephalad instead of caudad as the rib cage expands in inspiration • Diaphragmatic weakness/paralysis is also common following liver transplantation, and is seen in a number of neurometabolic and myopathic disorders • Fluoroscopy provides good images but is limited by need for transport to the radiology department and need for ionizing radiation ULTRASOUND • US at the bedside is accessible, makes an immediate diagnosis, and enables simple repeated follow-up—M-mode is preferred, patient must be taken off positive pressure • Should be investigated when failure to wean, respiratory distress, asymmetric breathing pattern, or paradoxical diaphragmatic movement are noted CXR may reveal raised hemidiaphragm but this may not be present in a patient on positive pressure ventilation Abdomen • Provides general evaluation of entire abdominal contents including pelvis and retroperitoneum • Enables assessment of the unstable patient with abdominal trauma for rapid diagnosis of organ or vascular damage • Has an increasing role in identification of NG and nasojejunal tube position as an alternative to plain X-ray or fluoroscopy • Solid organs can be assessed for parenchymal changes • Identifies intraperitoneal or visceral mass lesions but may miss those obscured by overlying organs or air-filled bowel • Detects even small amounts of peritoneal fluid, e.g around liver—small amounts of free fluid are common and can be seen in the absence of intra-abdominal pathology, including with generalized capillary leak and/ or fluid overload • Superior to other modalities in imaging of the biliary tree • Although a good screen for pancreatic disease, CT may be required for diagnosis with US useful for intervention and follow-up Renal • Assessment of the genitourinary tract includes renal parenchyma, collecting system and a ‘vascular map’ to assess perfusion that measures renal arterial and venous flow • US is an appropriate study in the evaluation of acute renal failure to distinguish pre-renal, from renal pathology and obstructive uropathy • iechogenicity (‘bright kidneys’) is seen in conditions where glomerular or tubular disease is present • drenal perfusion may be seen in patients with sepsis and hypotension, and with the use of vasoconstricting drugs—Doppler shows a high resistive index (high systolic/diastolic ratio) • Calcified lesions are easily identified including stones, or nephrocalcinosis associated with excessive diuretic use • US may identify adrenal haemorrhage in children with fulminant septicaemia, usually but not restricted to meningococcal disease • Renal vein flow and patency as well as renal size are assessed to rule out renal vein thrombosis in the patient with haematuria, thrombocytopenia, and an abdominal mass • Bladder volume estimation is useful in a child with a neuropathic bladder in assessing adequacy of emptying and the need for catheterization Venous thromboembolic disease • Venous thrombosis, particularly of the central veins, is rarely suspected clinically but occurs quite commonly in critically ill children 339 340 CHAPTER 19 Imaging in paediatric intensive care • Thrombi are most commonly associated with a CVL, and more often seen in lower extremities, reflecting the widespread use of the femoral vein for central catheterization • Risk factors include young age, recent trauma or surgery, low cardiac output state, systemic infection, malignancy or autoimmune disease, and prolonged immobility • In the presence of a blocked CVL or positive blood cultures, thrombosis should be strongly suspected and ruled out • US remains the most common tool for the diagnosis of venous thrombosis Venography is considered the gold standard but is impractical in the intensive care setting and few studies have compared it to US in children • Prophylaxis and treatment of high risk patients with unfractionated or low molecular weight heparin is increasingly common and appears safe and effective in children Stockings may be a useful adjunct, especially if anticoagulation is contraindicated US-guided intervention • US offers the major advantage of obviating the need to move the patient outside the ICU for interventional procedures • Imaging in real-time minimizes the risk of damage to vital structures • US-guided drainage of pleural effusion is associated with a higher yield and fewer complications • Direct instillation of fibrinolytic agents into empyemas and follow-up imaging are possible at the bedside • Abscesses and cysts in the chest and abdomen are often diagnosed by CT but drainage may be guided by either modality • Abdominal paracentesis and placement of Tenckhoff catheters for peritoneal dialysis may be aided by identifying optimal location for drainage avoiding vital structures • Emergency paracentesis can be guided at the bedside in cases of rapidly progressive abdominal compartment syndrome Vascular access • US is increasingly used in the placement of CVLs, with NICE recommending its use, though supporting evidence for this is limited • Evidence for US use is best for internal jugular and subclavian veins • The traditional ‘landmark’ technique is still widely practised and associated with well-known complications including haemorrhage, arterial puncture, and wrong trajectory of the catheter • Pneumothorax or haemothorax may be seen after internal jugular and subclavian line insertion • The success of catheter placement is significantly reduced in the presence of venous thrombosis regardless of technique used, so US imaging may be useful as a screen when problems are anticipated ECHOCARDIOGRAPHY Echocardiography (See b Chapter 20.) • Echocardiography assesses cardiac structure and function and has become a major adjunct to clinical examination and to monitoring of the critically ill • Pre- and postoperative US imaging of the child with congenital heart disease is an essential part of their ICU management • Transthoracic echocardiography (TTE) is most commonly used for rapid bedside evaluation • A number of different views are obtained (see Fig 19.1) • New diagnosis of previously unsuspected cardiac disease in the critically ill child is not uncommon, particularly in the neonatal period • Detailed images of cardiac anatomy including atrial and ventricular chambers and septae, valves, vegetations, and thrombi can be obtained • The configuration of the large vessels draining into and away from the heart can be established • Doppler technology permits assessment of flow patterns and velocities within the heart and great vessels and the study of intracardiac shunting across valves or septal defects • Regurgitant flow across the pulmonary and tricuspid valves is frequently seen in critically ill patients enabling estimation of pulmonary arterial pressures (see b p.861) • Cardiac function can be examined in a qualitative manner as well as with specific measurements of chamber diameters, systolic and diastolic function (see b Chapter 7) • A major advantage is the ability to sequentially study function to follow the effects of time or specific therapeutic interventions • IVC assessment may provide information on patient volume status and femoral venous catheter-related thrombosis Indications for echocardiography • Review of anatomy and function following cardiac surgery • Evaluation when cardiac disease is suspected • Assessment of myocardial function and regional wall abnormalities, valve function, presence of vegetations or thrombi • Estimation of intravascular volume status and response to preload • Clinical suspicion of cardiac tamponade • Unexplained haemodynamic instability with high inotrope requirement • Unexplained hypoxaemia where intracardiac shunt suspected • Clinical evidence suggestive of high pulmonary artery pressures • Clinical suspicion of proximal pulmonary emboli or with or without presence of deep vein thrombosis • Identification and quantification of pericardial fluid • US-guided pericardiocentesis • Evaluation of the infant with stridor and suspected vascular ring 341 342 CHAPTER 19 SVC AO Imaging in paediatric intensive care AO LPA RA RA PA LA LA RV LV RV RV IVC IVS AV LV PM MV AO LV RV IVC LV TV IVS RA LA PM MV LA Long-axis view Four-chamber view SVC AO RA IVC RA IAS LA AO RV TV RV IVS LV PV MV PA RV LV PPM APM Short-axis views AO = aorta; AV = aortaic valve; IAS = interatrial septum; IVC = inferior vena cava; IVS = interventricular septum; LA = left atrium; LV = left ventricle; MV = mitral valve; PM = papillary muscle; RA = right atrium; RV = right ventricle; SVC = superior vena cava; TV = tricuspid valve Fig 19.1 Three major axis views of 2D-echocardiography for defining structural abnormalities Reproduced from Toro-Figueroa LO, Levin D (1992) Essentials of Paediatric Intensive Care Manual Quality Medical Publishing Inc St Louis, MO Limitations • Images may be limited in mechanically ventilated children by the use of high ventilator pressures, PEEP, and air trapping • The presence of dressings, drains, large cannulae for assist devices, or when sternal closure after cardiac surgery has been delayed, may all impede optimal imaging • Right ventricular function is more difficult to assess RV dilatation and dysfunction is seen in parenchymal lung disease, sepsis, and any condition that increases PVR • TTE is poor at imaging peripheral vascular structures, including branch pulmonary arteries Transoesophageal echocardiography (TOE) • TOE views the heart from behind and enables highly detailed examination of valves, vegetations and thrombi, particularly within the atria • Has a major role in intraoperative assessment during cardiac surgery ~assessing repair and any residual intracardiac shunts • Useful when TTE is limited by poor acoustic windows • Thoracic aorta well seen, useful in the assessment of trauma • TOE is superior to TTE at demonstration of endocardial detail • Provides similar information on haemodynamic status as TTE and may have a role in continuous monitoring—increasingly used during cardiac surgery, particularly in adults MAGNETIC RESONANCE IMAGING • Complications are uncommon—the intensivist should be present throughout as there is potential for the ETT to be moved or dislodged by the probe Pulmonary emboli • The majority of pulmonary emboli in children originate from CVL-associated thrombi • Emboli are easy to miss clinically because signs are often ascribed to the patient’s underlying illness • Pulmonary emboli contribute significantly to morbidity and mortality when they are present • TTE is frequently performed as a first-line bedside investigation and may identify large proximal thrombi • Diagnosis of the associated acute cor pulmonale can be made at the bedside with TTE although right ventricular dilatation and dysfunction may be due to other causes of acute pulmonary hypertension • Ventilation-perfusion (VQ) scanning has a role in the diagnosis, but is rarely used in the ICU setting due in part to the confounding presence of underlying lung parenchymal disease • CT angiography is the diagnostic modality of choice to thoroughly assess central and peripheral emboli, and small septic emboli Magnetic resonance imaging MRI is based on the principle that nuclei in hydrogen atoms will align themselves with a strong magnetic field Radiowaves then applied to the tissue under study are altered by aligned hydrogen nuclei and the signal returned is measured and recorded • MRI offers excellent spatial resolution and a high sensitivity for detecting structural lesions in the CNS and cardiovascular system • It can also provide information on function and perfusion and the status of tissue with respect to ischaemia and vascular patency In critically ill children the commonest indication is the assessment of intracranial pathology on a non-emergency basis • Metal-containing medical devices such as infusion pumps and pacemakers can malfunction in the magnetic field Advantages of MRI • • • • • No ionizing radiation Multiplanar imaging possible Provides non-invasive information on function and perfusion Better correlation than CT with severity and outcome in brain injury Non-iodine based ‘paramagnetic’ contrast associated with fewer allergic reactions Disadvantages of MRI • Often geographically at a distance from intensive care environment • ICU equipment often incompatible with MRI environment • Monitoring and supportive therapy may be suboptimal during study 343 344 CHAPTER 19 Imaging in paediatric intensive care • Long study times and the numbers of staff involved in transfer make MRI scanning a labour intensive process • Unstable critically ill children may be unsuitable for scanning The diagnostic benefit has to weighed against the risk and effort involved • Metallic devices (pacemakers, wires, clips, spinal rods, ICP catheters) cause significant artefact and may preclude MRI study altogether MRI of the central nervous system • Diffuse axonal injury well detailed with superior grey/white differentiation capabilities to CT • Provides superior information on white matter and basal ganglia • Part of work-up in non-accidental injury when brain injury documented • Useful for study of intracerebral or spinal cord ischaemia, infarction, inflammation, subdural or extradural haemorrhage • Acute disseminated encephalomyelitis best diagnosed with MRI • Detailed assessment of demyelination possible • Useful when suspicion of c-spine cord or ligamentous injury • Gadolinium contrast primarily used to assess vascular supply of mass lesions or to differentiate tumour from oedema MR spectroscopy • Used to investigate the metabolic activity over an area of interest • Characteristic ‘metabolic profile’ may offer diagnostic information • Lacate peak of interest in metabolic disease and/or ischaemia MRI of the cardiovascular system • Role increasing in the assessment of structural congenital heart disease • Enables visualization of central and peripheral vascular anatomy and relationships to lungs and airways • No ionizing radiation in contrast to conventional angiography • Direction and speed of blood flow as well as shunt can be documented • Reconstructed images give 3D structural information • Right and left ventricular volumes and function can be estimated • Gadolinium contrast may be used to provide magnetic resonance angiogram (MRA) of great vessels Further reading Johnson K, Williams H, Foster K, et al (eds) (2009) Paediatric Radiology Oxford University Press ... Prescribing 3 13 19 39 45 61 103 12 9 17 5 18 5 19 9 2 21 229 257 275 289 295 xii SUBJECT OF THIS PAGE CONTENTS 18 Transport and retrieval 19 Imaging in paediatric intensive care 20 21 22 23 24 25... hypertension protease inhibitor paediatric intensive care Paediatric Intensive Care Audit Network paediatric intensive care medicine Paediatric Intensive Care Society paediatric intensive care unit pulmonary... measurement Vascular access and clinical monitoring Applied physiology and bedside assessment 10 11 12 13 14 15 16 17 Section Organ system support and related practical procedures Airway management and