Dermot R. Doherty

Hypothermia Therapy After Pediatric Cardiac Arrest

Background— Hypothermia therapy improves mortality and functional outcome after cardiac arrest and birth asphyxia in adults and newborns. The effect of hypothermia therapy in infants and children with cardiac arrest is unknown. Methods and Results— A 2-year, retrospective, 5-center study was conducted, and 222 patients with cardiac arrest were identified. Seventy-nine (35.6%) of these patients met eligibility criteria for the study (age >40 weeks postconception and <18 years, cardiac arrest >3 minutes in duration, survival for ≥12 hours after return of circulation, and no birth asphyxia). Twenty-nine (36.7%) of these 79 patients received hypothermia therapy and were cooled to 33.7±1.3°C for 20.8±11.9 hours. Hypothermia therapy was associated with higher mortality (P=0.009), greater duration of cardiac arrest (P=0.005), more resuscitative interventions (P<0.001), higher postresuscitation lactate levels (P<0.001), and use of extracorporeal membrane oxygenation (P<0.001). When adjustment was made for duration of cardiac arrest, use of extracorporeal membrane oxygenation, and propensity scores by use of a logistic regression model, no statistically significant differences in mortality were found (P=0.502) between patients treated with hypothermia therapy and those treated with normothermia. Also, no differences in hypothermia-related adverse events were found between groups. Conclusions— Hypothermia therapy was used in resuscitation scenarios that are associated with greater risk of poor outcome. In an adjusted analysis, the effectiveness of hypothermia therapy was neither supported nor refuted. A randomized controlled trial is needed to rigorously evaluate the benefits and harms of hypothermia therapy after pediatric cardiac arrest.

Hypothermia Therapy for Cardiac Arrest in Pediatric Patients

Cardiac arrest is associated with high morbidity and mortality in children. Hypothermia therapy has theoretical benefits on brain preservation and has the potential to decrease morbidity and mortality in children following cardiac arrest. The American Heart Association guidelines recommend that it should be considered in children after cardiac arrest. Methods of inducing hypothermia include simple surface cooling techniques, intravenous boluses of cold saline, gastric lavage with ice-cold normal saline, and using the temperature control device with extracorporeal life support. We recommend further study before a strong recommendation can be made to use hypothermia therapy in children with cardiac arrest.

A weight‐based formula for tracheal tube size in children

Objective:  Age (in years) of the child has conventionally been used in formulae to estimate the tracheal tube (TT) size. The objective of this retrospective study was to test a weight‐based formula (WBF) for uncuffed oral TT in children and compare it with the conventional age‐based formula (ABF).

A review of pediatric capnography.

ObjectivesCapnography has become a standard of perioperative monitoring in pediatric anesthesiology. It has also begun to find application in a variety of situations outside the perioperative setting. While the use of capnography has been increasing, the dissemination and acceptability of capnography in all areas of pediatrics has been variable. The purpose of this study was to describe all the applications and interpretations of capnography that have been reported in children.MethodsIn March 2010, we completed a search of peer reviewed literature from MEDLINE (from 1950), CINAHL (from 1982) and the Cochrane Library. Final search results were limited to publications in which the primary intent was to describe the application or interpretations of capnography in children.ResultsThis search resulted in a list of 44 applications and interpretations of capnography. We classified the applications and interpretations of capnography in children into six categories—Anesthetic Delivery Apparatus, Airway, Breathing, Circulation, Homeostasis and Non-perioperative. We discuss the four randomized controlled trials describing the use of capnography in children. Based on the available evidence, we have also assigned grades of recommendations for these applications and interpretations.ConclusionsCapnography has been proven to be a useful non-invasive perioperative monitor of the physiology and safety of the child. This list of the clinical applications and interpretations of capnography could find use in teaching and simulation in pediatrics.Capnography has become a standard of perioperative monitoring in pediatric anesthesiology. It has also begun to find application in a variety of situations outside the perioperative setting. While the use of capnography has been increasing, the dissemination and acceptability of capnography in all areas of pediatrics has been variable. The purpose of this study was to describe all the applications and interpretations of capnography that have been reported in children. In March 2010, we completed a search of peer reviewed literature from MEDLINE (from 1950), CINAHL (from 1982) and the Cochrane Library. Final search results were limited to publications in which the primary intent was to describe the application or interpretations of capnography in children. This search resulted in a list of 44 applications and interpretations of capnography. We classified the applications and interpretations of capnography in children into six categories—Anesthetic Delivery Apparatus, Airway, Breathing, Circulation, Homeostasis and Non-perioperative. We discuss the four randomized controlled trials describing the use of capnography in children. Based on the available evidence, we have also assigned grades of recommendations for these applications and interpretations. Capnography has been proven to be a useful non-invasive perioperative monitor of the physiology and safety of the child. This list of the clinical applications and interpretations of capnography could find use in teaching and simulation in pediatrics.

Calcitriol trend following pediatric cardiac surgery and association with clinical outcome

BackgroundConsistent with accepted practice in stable ambulatory populations, the majority of ICU research has evaluated vitamin D status using a single blood 25-hydroxyvitamin D (25(OH)D) level. Only a limited number of ICU studies have measured the active hormone, 1,25-dihydroxyvitamin D (calcitriol) and none have used change in calcitriol levels to evaluate axis functioning. The objective of this study was to describe the impact of Congenital Heart Disease (CHD) surgery on calcitriol levels and evaluate the relationship between change in postoperative levels and clinical course.MethodsSecondary analysis of a prospective cohort study of 56 children undergoing surgery for CHD.ResultsMean calcitriol levels dropped from 122.3 ± 69.1 pmol/L preoperatively to 65.3 ± 36.5 pmol/L (p < 0.0001) at PICU admission. The majority (61%, n = 34) were unable to increase calcitriol levels in the 48 h immediately following surgery. Post operative trend in calcitriol was inversely related to cardiovascular dysfunction, fluid requirements, ventilatory support and PICU length of stay (p < 0.01).ConclusionCHD patients had significant dysfunction of the vitamin D axis immediately postoperatively, demonstrated by both a significant intraoperative decline in calcitriol and inability to increase levels. Interventional research will be required to determine whether the use of calcitriol, in addition to cholecalciferol, reduces postoperative illness severity.

Pediatric Critical Care – Fourth Edition

This is the fourth addition of a textbook which is long recognized as one of the core reference textbooks in the specialty of pediatric critical care medicine (PCCM). This edition should be seriously considered by trainees embarking on a career in PCCM or by established specialists seeking to update their desktop reference book. Similar to the other textbook models, the list of chapter authors is drawn from many of the experts who frequent international conferences along with authors who are beginning their careers. It is notable that the chapter authors are drawn predominantly from North America, with surprisingly few authors from elsewhere in the world. This approach has the advantage of contributing content that reflects contemporary North American practice, terminology, and nuances; however, with this type of focus, it has the disadvantage of possibly losing other perspectives, as PCCM is truly an international specialty. For the most part, the textbook format and writing style is consistent, although there are some chapters that are particularly strong and others that leave room for improvement. In my review of the textbook, I found the chapters in which I have a professional interest to be especially strong. I also used several chapters to structure resident tutorials and found them to be a comprehensive resource. The textbook was not designed as a resource for a resident to use when setting a ventilator at 4 a.m. while on-call, but it does provide depth into the fundamentals of the specialty. This edition of the book comes with an online version, which makes it accessible for those who wish to consult the textbook while on the go. The online version is intuitive and easy to use, and by using the search function, readers can quickly identify whether the book has the answer to a focused question. More often than not, I received answers to my focused questions when I made use of the search function, which, in my view, is characteristic of many similar texts. At the beginning of the textbook, the editors acknowledge that pediatric intensive care is a resource-intense highacuity specialty provided largely by academic institutions. There are some especially solid chapters that address institutional organization, ethics, family-centred care, quality metrics, research, education, and evidence-based medicine. I applaud the editors for this approach, as they recognize that most of an intensivist’s time is spent in pursuing the academic and administrative mandate of an institution and not in direct patient contact. This first part of the textbook provides a foundation for this perspective, and it is as important as the ‘‘comfort food’’ in the following chapters based on systems and disease. The focus of the remainder of the book is on applied physiology, pathology, and therapeutics—what a reader would expect from an intensive care textbook. The cardiovascular system is the main focus of the second part of the textbook. While the basic knowledge of this system is adequate, in my opinion, the coverage of the pediatric congenital cardiac surgical population is not comprehensive enough to meet the challenges of working in a large congenital cardiac surgical program. Programs that have large cardiac intensive care components would require an additional core textbook to cover this material in detail. Yet, I do not consider this as an indictment of this textbook but rather the reality of what some might consider a sister specialty. The neurocritical care section of the text is particularly strong and comprehensive. The textbook also includes D. Doherty, MD (&) Irish Paediatric Critical Care Network, Dublin, Ireland e-mail: dermot.doherty@cuh.ie

Towards a pharmacological neuro-protectant: can anesthesia deliver?

Transient global cerebral ischemic injury (tGCI) continues to be a significant cause of death and disability. Global cerebral ischemia usually results from complex medical conditions, including cardiac arrest, circulatory shock, and birth asphyxia or iatrogenic interventions, such as circulatory arrest for cardiovascular surgery. The pathophysiology of global cerebral ischemia is complex. Experimental studies have identified a number of potential therapeutic treatments. Some of these treatments have targeted the initial metabolic events following brain ischemia, including energy failure, calcium ion flux, free radical generation, and the attenuation of excitotoxicity. These harmful mechanisms have been targeted with pharmacological interventions in experimental models. However, none of these promising pharmacological therapies have been successfully translated into clinical use. Such ‘‘easy to administer’’ therapies could be stocked in crash carts for administration to patients once the heart has been restarted. By contrast, physiological therapies, such as therapeutic hypothermia, have gained success in both experimental and clinical settings. This type of therapy is difficult to administer and involves extensive infrastructure, resources, and personnel. However, even therapeutic hypothermia may not be applicable across all human populations. Pre-conditioning is a strategy that involves increasing the brain’s tolerance to ischemia by exposing the brain to minor ischemic insults or pharmacological agents prior to the occurrence of a major ischemic event. While anesthetic preconditioning has shown initial promise in protecting the brain from ischemic events in pre-clinical studies, to date, there is no convincing clinical epidemiology supporting this practice. The pre-clinical science regarding the potential of anesthetic preconditioning is far from clear. This is illustrated in a recent article by Codaccioni et al., who report a transient but non-sustained improvement in neurocognitive testing in a rodent model of focal brain ischemia. In reality, this may simply be reflective of and/or specific to the particular model employed in their experiments. Any potential neuroprotective effects of anesthetic preconditioning depend on the anesthetic agent used to precondition, the species studied, the model of ischemia, the age and sex of the animal, the duration of preconditioning, and the interval between preconditioning and ischemic insult. In other words, it is not clear whether this will translate into a universally applicable therapy for tGCI. Anesthetic preconditioning is one of several strategies that prepare the brain to anticipate or react to the ischemic insult. Examples of other strategies used to precondition the brain include toxins, temperature, pharmaceuticals, and ischemia itself, with the latter showing most promise. The common theme of these strategies is to unbalance several key cell signal transcriptional programs in favour of cell survival, rather than any single metabolic pathway or target protein. Neuronal death after tGCI is complex. Characteristic lesions in vulnerable regions of the brain (such as the hippocampus and the striatum) appear from 12 h to 3 days after resuscitation and continue to evolve in the following weeks to months. Most cells that die do so by programmed cell death (PCD), as opposed to necrosis. This type of neuronal death has several features of apoptosis, with the cysteine-dependent aspartate-directed proteases family (the caspases) featuring strongly as executioners of PCD. Caspases normally exist in an inactivated state (pro-caspases), but under stressful conditions, cleavage (activation) D. R. Doherty, MBBCh (&) Department of Anesthesiology, Children’s Hospital of Eastern Ontario, 401 Smyth Road, Ottawa, ON K1H 8L1, Canada e-mail: ddoherty@cheo.on.ca