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The 2002 Annual meeting of the Society, chaired by Maurice
S. Zwass (University of California, San Francisco), took place on
October 11, 2002 in Orlando, FL. The meeting was again divided into major
themes, covering both scientific and clinical areas of anesthesia practice.
The morning's two sessions were devoted
to an examination of hemostasis and coagulation. In the first, moderated
by Dr. Zwass, Marilyn Manco-Johnson (The Children's Hospital, Denver/
University of Colorado) gave an exceptionally clear review of coagulation
in infants and children in the perioperative period. She noted that the
classical conception of the clotting cascades, in which two parallel pathways
converge with the conversion of Factor X to Factor Xa, has given way to
an integrated system in which tissue factor initiates the activation of
the coagulation system. This "intrinsic pathway" is now thought
to be the dominant system, in which tissue factor, exposed when endothelium
is damaged, interacts with zymogen and Factor VIIa to convert a small
amount of Factor X to Xa. This is amplified through the entire coagulation
system response, including platelet activation and the activation of other
coagulation factors to induce clotting as an integrated and interacting
circuit. Dr. Manco-Johnson discussed the developmental physiology of the
coagulation system, and described the alterations in clotting function
in neonates. Neonates are particularly prone to disorders of hemostasis,
in that they may have more pronounced tissue factor elaboration. A logical
approach to testing and therapy of genetic and ascquired disorders of
hemostasis and thrombosis in pediatrics was presented.
Michael A. Gropper (University
of California, San Francisco) discussed the sepsis syndrome and its interface
with systemic inflammatory response and the coagulation system. The systemic
response to infection is characterized by the elaboration of inflammatory
mediators such as TNFa, IL-1 and IL-6, which can spill over and injure
organs not initially involved in the inciting event. Unfortunately, attempts
at blocking these cytokines have not proven successful in improving outcome
in multiple clinical trials, probably because we are unable to properly
modulate the immune response. Dr. Gropper discussed the role that supportive
therapies may have in both attenuating and aggravating the sepsis/ systemic
inflammatory response syndrome. The use of low tidal volume ventilation,
for example ("protective ventilation strategies") may decrease
the elaboration of inflammatory mediators by decreasing alveolar stretch
and mechanotransductive effects on the lung. The prime reason for his
talk, however, was the important role that the coagulation system plays
in the sepsis syndrome. Even patients who do not have an overt coagulopathy
such as DIC have demonstrable abnormalities in clotting and fibrinolysis,
and it is thought that activation of endothelial cells plays an important
role in the propagation of the systemic inflammatory response. A recent
large clinical trial using activated protein C showed great promise at
decreasing mortality in sepsis syndrome without increasing the risk of
infection.
In the second session, moderated by Valerie Armstead (Jefferson
Medical College, Philadelphia), B. Craig Weldon (University of
Florida, Gainesville) discussed red cell transfusion and conservation
techniques. He first discussed the infectious and immunologic risks of
transfusion therapy, and updated the audience on the relatively recently
recognized problem of transfusion related lung injury (TRALI). While the
first two problems are perhaps more familiar to most anesthesiologists,
TRALI has become an area of increased clinical and laboratory investigation,
and might be responsible for as many as 13 percent of transfusion-related
deaths. Incited by immunologic factors such as inadvertently transfused
white cells and humoral factors, this "innocent bystander" injury
to the lungs can result in acute respiratory failure similar to ARDS.
Leukocyte reduction or irradiation may reduce the risk. The relative risks
of various transfusion-mediated infections were discussed, with current
rates from both hepatitis and HIV now below the one per 1 million mark.
The transfusion trigger- the hematocrit or hemoglobin concentration at
which one decides to transfuse- was discussed next. The concept of critical
oxygen delivery was introduced, in which the transfusion trigger is linked
to how much oxygen must be delivered to end organs. Data and lessons learned
from clinical scenarios of extreme anemia were discussed, although conclusive
data in children remain scant. Dr. Weldon also described the risks and
benefits of directed donor and autologous donor transfusions. Several
blood conservation techniques have been found to be effective in children,
including deliberate (controlled) hypotension, acute normovolemic hemodilution,
intraoperative blood salvage (Cell Saver), and perioperative recombinant
erythropoietin therapy. The relative merits, efficacy, and risks of each,
as well as the multimodal use of several strategies in combination, were
compared and contrasted.
A fascinating lecture on the search for an effective and
safe blood substitute was given by Bruce D. Spiess (Medical College
of Virginia). He first reviewed the history of blood substitutes and their
clinical trials, from stromal-free hemoglobin and other hemoglobin-based
oxygen carriers to oxygen-carrying perfluorocarbon emulsions, and noted
the political issues surrounding the development of these agents due to
their potential applications in military medicine. In addition to the
obvious use of these agents as blood substitutes, Dr. Speiss introduced
the audience to the concept of "oxygen therapeutics"- the use
of hemoglobin substitutes as oxygen delivery agents to sites that natural
blood perfusion might not be able to reach. Perfluorocarbons, for example,
could be used to provide oxygenation to regions occluded by stroke or
thrombosis, potentially preventing or ameliorating infarction in the emergency
setting. Since these agents can carry nitrogen as well, they have application
in diving medicine and the treatment of air embolism.
he afternoon session, moderated by Anne
M. Lynn (Children's Hospital and Regional Medical Center, Seattle
/ University of Washington), began with a debate on the use of the laryngeal
mask airway for tonsillectomy and adenoidectomy. Elizabeth S. Yun,
MD (University of Wisconsin) advocated for the LMA, first describing
the technique in this setting, and noted that several small studies have
suggested lower rates of coughing and laryngospasm, along with perhaps
better airway protection from aspiration than an uncuffed endotracheal
tube. She showed photographs to document that the flexible LMA does not
obstruct the surgeon's view of the field. Rita Agarwal (The Children's
Hospital, Denver / University of Colorado) took the opposing position,
arguing that in patients with obstructive sleep apnea (a common indication
for tonsillectomy) spontaneous ventilation may be more difficult to achieve,
and that an equal number of small studies showed higher rates of airway
problems with the LMA. If these occur intraoperatively, it may necessitate
changing to an endotracheal tube in the middle of the procedure, when
the oropharynx is bloody. Surgical acceptance may be a problem with introducing
the use of the LMA as well. Mark Schreiner (Children's Hospital
of Philadelphia, University of Pennsylvania, and the Children's Clinical
Research Institute) completed the session with a superb lecture on evidence-based
medicine, and how critical reading and analysis of the literature can
help in clinical decision-making. Using the case of the LMA, he discussed
the clinical investigations cited by both debaters, and noted
that none of the data in the studies provided conclusive evidence to definitively
support either position! Flawed study design and inadequate power were
mentioned as the two most common defects that limit the ability to draw
conclusions from clinical investigations.
Letty M.P. Liu (Massachusetts General
Hospital / Harvard Medical School) moderated the final session of the
day. Zeev N. Kain (Yale University School of Medicine) concluded
the pediatric anesthesia topics with a survey of issues related to family-centered
care in pediatric anesthesia. The majority of scientific data in this
field has been generated by Dr. Kain and his research group at Yale, where
rigorous methodology has been applied to studying issues that were previously
addressed only by descriptive or poorly controlled and validated techniques.
He discussed parental presence during induction, pre-medication, postoperative
behavioral disturbances, and related topics, and stressed that as pediatric
anesthesiologists we can do much to influence the behavioral and psychosocial
outcome, as well as the medical outcome, of our patients. He noted that
the consequences of these events last far longer than many of us would
expect, and also cautioned that before adopting an intervention or program,
there should be compelling evidence that it can achieve its objective.
This crucial aspect of care, often neglected when considering anesthetic
technique, is likely to come under increasing scrutiny and emphasis by
both professionals and families.
The final presentation of the meeting
was given by Warren M. Zapol (Massachusetts General Hospital /
Harvard Medical School). Dr. Zapol, the Reginald Jenny Professor and Chairman
of the Department of Anesthesia at the MGH, has had an exciting and unusual
research career that has gone far beyond the walls of the Wellman Research
Building and Respiratory Intensive Care Unit at the MGH in Boston. He
spoke about his fascinating and groundbreaking (or icebreaking??) research
on the Weddell seal, the champion diver of the Antarctic. Dr. Zapol has
spent seven austral summers on the Ross Ice Shelf and McMurdo Station
in Antarctica leading an international team of scientists studying the
diving physiology of these seals and learning how they are able to withstand
the extremes of hypoxia. He illustrated his talk with stunning photographs,
and hinted at the implications of his findings in human conditions of
hypoxia during diving.
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B. Craig Weldon, MD
Bruce D. Spiess, MD
Elizabeth S. Yun, MD
Rita Agarwal, MD
Zeev N. Kain, MD
Warren M. Zapol, MD
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