TY  - CHAP
M1  - Book, Section
TI  - Chapter 20. Evaluation of Children
A1  - Wetzel, Randall C.
A2  - Longnecker, David E.
A2  - Brown, David L.
A2  - Newman, Mark F.
A2  - Zapol, Warren M.
Y1  - 2012
N1  - 
T2  - Anesthesiology, 2e
AB  - Children  have  significantly  different  physiology  and  psychology  and  behavior  to  necessitate  a  comprehensive  pediatric  approach  for  the  child  and  the  family  based  on  their  requirements.The  percentage  of  total  body  composition  that  is  water  decreases  with  age;  intracellular  fluid  increases,  whereas  extracellular  fluid  decreases.Fat  and  muscle  mass  increase  from  13%  to  22%  and  20%  to  50%,  respectively,  with  age.The  distribution  of  blood  flow  varies,  with  a  decreased  percentage  of  flow  going  to  the  vessel-rich  groups  with  increased  age.Infants  have  a  large  tongue  and  relatively  small  jaw.  Infants  usually  are  described  as  having  an  anterior  and  cephalad  displacement  of  the  airway,  with  the  narrowest  segment  at  the  level  of  the  cricoid.  The  epiglottis  generally  is  large  and  floppy  compared  with  that  of  adults.Younger  children  tend  to  experience  airway  closure  and  alveolar  collapse  with  atelectasis  because  the  end-expiratory  lung  volume  from  which  tidal  breathing  occurs  is  close  to  closing  capacity.Although  the  functional  residual  capacity  in  milliliters  per  kilogram  is  smaller  in  infants  compared  with  adults  (30  vs  34),  increased  oxygen  consumption  is  the  major  factor  in  the  rapid  desaturation  of  infants.The  perioperative  risk  of  reversion  to  a  transitional  circulation  is  related  to  pulmonary  hypertension  triggered  by  hypoxemia,  hypercarbia,  hypothermia,  acidosis,  and  increased  catecholamines.Cardiac  output  depends  on  heart  rate  in  infants  and  young  children.  Infants  have  parasympathetic  hypertonia,  decreased  sympathetic  innervation,  and  a  ventricle  with  less  muscle  and  more  noncontractile  mass  per  unit  volume.  These  all  lead  to  a  myocardium  that  is  less  able  to  generate  adequate  force  than  in  adults.A  hematocrit  nadir  of  approximately  35  at  approximately  age  3  months  is  the  so-called  physiologic  anemia  of  infancy.The  glomerular  filtration  rate/1.73  m2  increases  from  40  to  130  mL/min  with  age.  Ability  to  concentrate  urine  is  limited,  and  maximal  osmolarity  may  be  only  700  mOsm.Slack  lower  esophageal  sphincter  tone  with  reflux  is  common  in  infants  younger  than  6  months,  but  the  maintenance  of  low  gastric  volumes  by  nothing-by-mouth  (NPO)  regulations  should  be  balanced  by  awareness  of  the  risk  of  hypoglycemia.The  liver  is  functionally  immature  in  children,  affecting  synthetic  and  metabolic  function.Defending  the  thermoneutrality  of  infants  is  a  cornerstone  of  pediatric  anesthesia.Cold  stress  in  neonates  can  increase  oxygen  consumption  and  decrease  oxygen  delivery,  leading  to  increased  hydrogen  ion  concentration  and  decreased  glycogen  and  glucose.  This  may  result  in  respiratory  distress,  disseminated  intravascular  coagulation,  shock,  and  persistent  fetal  circulation.The  large  surface-area-to-mass  ratio  in  children  and  decreased  subcutaneous  tissue  mass  lead  to  increased  heat  loss  via  conduction,  convection,  radiation,  and  evaporation.The  large  volume  of  distribution  noted  in  neonates  is  related  to  decreased  protein  binding  and  a  greater  proportion  of  extracellular  water.In  preoperative  evaluation,  the  anesthesiologist  should  prepare  himself  or  herself,  the  family,  and  the  child  for  the  procedure.  The  primary  objective  is  to  ensure  that  the  child  is  in  optimal  condition.  Developmental  milestones  and  growth  charts  should  be  reviewed  to  assist  in  the  general  assessment  of  well-being.  Optimal  drug  levels  (eg,  anticonvulsants  and  theophylline)  should  be  ensured.Many  congenital  anomalies  are  associated  with  airway  and  cardiac  abnormalities.In  children  with  known  cardiopulmonary  disease,  it  is  imperative  that  the  anesthesiologist  be  completely  familiar  ...
SN  - 
PB  - The McGraw-Hill Companies
CY  - New York, NY
Y2  - 2024/04/19
UR  - accessanesthesiology.mhmedical.com/content.aspx?aid=56626481
ER  -