Techniques to avoid circulatory arrest in neonatal cardiac surgery

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2004.12.08
Techniques to avoid circulatory arrest in
neonatal cardiac surgery
???
2
DHCA Current status and Ix Jonas RA, Boston
Children's Hospital

• DHCA unfavorable long-term neurologic deficits
• 1953 Lewis and Tauffic, introduction of TCA
• 1970 Barratt-Boyes, application of TCA in
  early complete repair
• Advantages of DHCA
• decreased exposure to CPB with its sequelae
• improved operative field exposure
• avoidance of multiple cannulas
• reduced postoperative edema

3
Deleterious effects of CPB in small children

• 1. Particulate and gaseous emboli
• 2. Hypoperfusion
• 1) Bronchial collaterals and left heart return
• In cyanotic heart, more than 30 to 40
• pulmonary edema, myocardial injury form
  ventricular distention
• global underperfusion secondary to steal
• 2) Cannulation methods
• arterial cannula in IAA or HLHS
• venous cannula in very small babies
• occluded venous drainage from brain

4
Circulatory arrest trial

• Prospective randomized study (over 4 year to
  March 1992)
• 171 under 3 months of age, TGA with or without
  VSD
• circulatory arrest or continuous low-flow pass at
  50 cc/kg/min
• alpha stat and crystalloid hemodilution to Hct of
  20
• mean circulatory arrest duration 55 min

5
Circulatory arrest trial

• Perioperative findings
• Risk factors of seizure
• alpha-stat
• low Hct
• VSD associated with older age
• Correlation btw duration and seizure

6
Circulatory arrest trial

• 1 year of age
• 1) Developmental testing
• Fine gross motor lower, association btw long
  arrest and low score
• Cognitive function lower, VSD - lower score
  
• 2) Neurologic examination more, association
  with long arrest
• 3) MRI no relation
• 4) Btw periop. seizures 1-yr outcome
• reduction of development index and high MRI
  abnormalities
• increased neurologic abnormalities

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Circulatory arrest trial

• 4 yrs of age
• similar in IQ, though worse motor and speech
• Periop seizure lower IQ neurologic
  abnormalities
• 8 yrs of age
• No difference in full scale, verbal, or
  performance IQ
• No difference in reading, math score, or academic
  achievement
• No difference in competence scales of teacher
  report forms
• Full-scale IQ linear decline in more than 40
  min of arrest

8
Refinements of circulatory arrest

• 1. pH strategy pH stat before 1985
  alpha stat after 1985
• 1) positive correlation btw arterial pCO2 and
  developmental score
• 2) choreoathetosis
• 3) prospective randomized trial (revert to
  pH-stat)
• higher adverse events including death.
• higher CI and lower inotropic support
• worse developmental scores at 1 yr of age

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Refinements of circulatory arrest

• 2. Hematocrit
• Higher Hct improved postop CO and developmental
  scores.
• Prospective randomized trial
• 3. Oxygen strategy
• Normoxic CPB increased histologic brain damage
  more than hyperoxic CPB
• Hypoxic injury increased oxygen free radicals

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Refinements of circulatory arrest

• 4. Post-circulatory arrest hyperthermia
• 33 to 34, 37, 39C for 24 hrs postop. after 100
  min of DHCA
• worse neurologic recovery, histologic outcome in
  hyperthermia
• 5. Intermittent reperfusion
• improve in intermittent reperfusion relative to
  cerebroplegia or arrest
• Intermittent reperfusion for a few min at
  intervals of 20 to 30 min beneficial in
  increasing safe duration of DHCA

11
Circulatory arrest in the 1980s vs in 2002

• In the 1980s
• alpha-stat
• Hct of 20
• High-prime
• No arterial filter
• Long arrest of up to 60 to 75 min
• No difference in IQ at 8 yrs of age

• Todays technique
• pH-stat
• Hct of 30
• Hyperoxygenation
• Intermittent reperfusion
• Avoidance of more than 1 hr
• Highly unlikely of any difference
• in neurodevelopmental outcome

12
Current Ix for DHCA

• Neonatal repair of TAPVC
• Intracardiac repair in premature neonates less
  than 2.5kg
• Arch reconstruction of Norwood procedure
• Interrupted aortic arch
• Complete AVSD in neonate and young infant for
  more accurate reconstruction of AV valve

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Summary

• Equal attention to refine methods of continuous
  CPB including methods for avoidance of
  circulatory arrest.
• No guidelines regarding how low flow, at what
  temp. and what duration of low flow can be used
  for pH, Hct, and collateral return.
• Circulatory arrest used more safely than
  innovative but unproven continuous CPB.

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Arch reconstruction without circulatory
arrestAsou T, Fukuoka Childrens Hospital

• Historical perspectives
• 1996 Asou first RLFP
• 1997 McElhinney
• 1999 Pigula similar
  techniques
• 2000 Tchervenkov
• 2000 Ishino combine
  with myocardial perfusion
• 1990 Sano and Mee
• 1992 Karl

isolated myocardial perfusion during TCA
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Access to Brain Perfusion

• 1. PTFE graft
• as prox. limb of shunt
• 3. McElhinney use of aortic arch at base of
  innominate a.
• 4. Tchervenkov from RPA to m-BT shunt into
  innominate a.

• 2. Specially designed
• thin-walled, metal-tipped cannula

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Optimal Flow Rate to Brain

• Uncertain due to lack of available data and study
• Pigula 20ml/kg/min, NIRS, cerebral oxygen
  saturation and blood volume
• Ishino 45 to 75 ml/kg/min, cerebral and
  myocardial perfusion
• Asou 50 ml/kg/min
• McElhinney 30 ml/kg/min
• Tchervenkov 0.40.8 l/min/m2 (1977 ml/kg/min,
  mean 45)
• Imoto proportion to upper lower body depends
  on systemic arterial resistance, flow to brain
  determined in physiologic way
• Tanaka perfusion pr. is important simple tool
  for adequate cerebral flow rate

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Perfusion to lt. side of brain

• Depend on circle of Willis
• Imoto pr. gradient of 4.42.2 mmHg
• Several variations of anatomy (Riggs Rupp, 994
  specimens)
• perfect pattern in only 21
• hypoplasia of communication arteries in 79
• extremely rare complete defect
• Wide spectrum of circle of Willis
• important to monitor perfusion of lt. Brain
• arterial pr. or NIRS
  

18
Optimal temperature

• Asou initially 22C
• Tchervenkov 18C
• Austin 18C
• 25C postop. renal dysfunction
• temperature is important in preserving
  subdiaphragmatic organs
• Ishino 28C
• Imoto 29 to 31C
• Warmer temp. of approximately 30C are currently
  used with lt hemisphere monitored using pressures
  NIRS
• No neurologic problem in postop. course
• Less adverse effects of deep hypothermia such as
  coagulopathy capillary leakage syndrome

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Perfusion to lower body
Imoto Y, Yasui H, Fukuoka Childrens Hospital

• Cerebral perfusion through innominate a. combined
  with cannulation of dsc aorta
• Moderate hypothermia
• High pump-flow CPB
• In neonate or infant this might be appropriate
  because dsc aorta is not excessively deep
  

Ann Thorac Surg 199968559-561
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Scientific basis for application Pigula FA,
Pittsburgh, PA.

• Primary objective of RLFP
• cerebral circulatory support
• somatic (subdiaphragmatic) circulatory support
• Ix of RLFP
• arrest time in excess of 20 min
• without compromise of repair
• 36 neonates
• 27 Norwood op.
• 9 biventricular repair
• RLPF simple and safe to arch repair in neonate
• recently liberalized to 30 to 40 cc/kg/min
  without neurologic cx with stable brain blood
  volumes

21
Experimental Studies

• Cerebral circulatory support
• minimum requirement btw 10 to 30 cc/kg/min
• Nara in dogs, flow as low as 30 cc/kg/min
  maintain cerebral oxygenation for up to 120 min
• Miyamoto in dogs, optimal rate for brain at
  20ºC 30 cc/kg/min, oxygen debt and anaerobic
  metabolism at below 15 ml/kg/min
• Swain in sheep, flows as low as 10 cc/kg/min
  preserve brain energy substrates
• Watanabe aerobic metabolism maintain at 40
  cc/kg/min of 20 mmHg

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Methodology (I)

• NIRS
• recent, noninvasive technology
• measure changes of tissue chromophores, oxyHb and
  deoxyHb
• exploits differences in absorption peaks btw
  oxygenated and deoxygenated Hb and provides
  information on changes, or relative differences,
• indication of total blood volume
• relative CrBVI and CrSO2 mainly determined by
  cerebral venous blood because it comprises 75 of
  intracranial blood volume (arterial, 20
  capillaries, 5).
• However, strong clinical correlation btw NIRS
  signal and flow in internal carotid a.

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Methodology (II)

• Muscle NIRS
• Measure of O2 saturation in skeletal m
  (gastrocnemius)
• Reflect change in oxyHb and deoxyHb than Hb
• Sup. assess of tissue than Hb oxygenation
• Gastric Tonometry
• pCO2 gap, difference btw arterial pCO2 and
  gastric mucosal pCO2
• Indicator of gastric mucosal ischemia
• Critical lower limit of blood flow 60
  reduction
• More appropriate than mucosal pH under low-flow
  and arrest

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Clinicial Studies

• Cerebral Circulatory Support
• NIRS use to regulate regional flow
• paucity of information in human neonates
• differences btw regional and central cannulation
• DHCA greater falls in relative CrBVI and CrSO2
  
• RLFP increase flow rate until baseline
• Reacquisition of baseline CrBVI with 20 cc/kg/min
• with reacquisition of CrBVI, CrSO2 to baseline
• lt radial a. pr. - average of 22 mmHg (16-28) at
  20 to 30 cc/kg/min
• Subdiaphragmatic support back-bleeding from dsc
  aorta, not completely isolate brain

J Thorac Cardiovasc Surg 2000119331-339
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Pigula FA, Children's Hospital of Pittsburgh
J Thorac Cardiovasc Surg 19991171023-1024
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Discussion

• For preventing cerebral hyperperfusion
• limit flow rate to baseline CrBVI
• for the human neonate, data suggest that 20 mL
  kg1 min1
• lt radial a. pr of 20 mm Hg
• collaterals intracranial connections via circle
  of Willis and extracranial collaterals, vertebral
  a., internal thoracic a., and intercostal a.
• low incidence of paraplegia encountered in
  neonatal coarctation repair
• brain, relatively low resistance organ, receives
  most of regional perfusion
• Benefits in Norwood op
• Time for performance of technically precise
  reconstruction
• 3 surgical goals
• Maintainence of satisfactory coronary perfusion
• Unobstructed and hemostatic construction of
  neoaorta
• Appropriate PBF

J Thorac Cardiovasc Surg 2000119331-339
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Somatic circulatory support

• Three techniques used to assess somatic perfusion
• abdominal aortic BP
• Abdominal aortic BP was higher (12 3 mm Hg
  versus 0 0 mm Hg)
• quadriceps blood flow (NIRS)
• quadriceps blood volumes (5 24 versus -17
  26) and O2 saturations (57 25 versus 33 12)
  were greater during regional perfusion
• gastric tonometry
• During rewarming, PCO2 gap of -3.3 0.3 mm Hg in
  DHCA compared with 7.8 7.6 mm Hg in RLFP (p
  0.03).

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Ann Thorac Surg 2001724017
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Comment

• Difference from conventional low-flow in Boston
  study
• cannulation is regional rather than central
• conventional low-flow CI of 0.75 L min-1
  m-2, RLFP CI of 0.45 L min-1 m-2
• Extensive collaterals
• During RLFP (30 to 40 ml kg-1 min-1), lt
  radial a. BP was 29 mm Hg with abdominal aortic
  BP of 12 mmHg.
• Aortic backbleeding
• Extremely low paraplegia
• Quadriceps NIRS increase muscle blood volumes and
  saturations - 5 min delay after RLFP
• PCO2 gap sensitive and specific for detection
  of gut ischemia
• Physiological importance of splanchnic blood flow
  
• due to role of GI ischemia in sepsis and
  multiorgan dysfunction
• How much of flow reaches cerebral circulation and
  perfuse lower body?
• it is possible to quantify return from IVC vs SVC

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Changes in cerebral and somatic oxygenation
Hoffman GM, Tweddell JS, Children's Hospital of
Wisconsin

• 9 neonates, HLHS
• Frontal cerebral thoraco-lumbar (T10-L2)
  somatic reflectance oximetry probes
• 18C-20C, pH-stat
• RLFP guided by estimated minimum flow
  requirements and measured rSO2
• After rewarming and separation from CPB, cerebral
  oxygenation was lower compared with prebypass or
  somatic values
• Cerebrovascular resistance increased after deep
  hypothermic CPB, even with continuous perfusion,
  placing cerebral circulation at risk
  postoperatively

J Thorac Cardiovasc Surg 2004127223-233
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Tissue oxygen tension during RLFPDeCampli WM,
Myung R, The Childrens Hospital of Philadelphia

• Cerebral cortical peripheral organ (liver,
  bowel, skeletal m.) tissue PO2
• 21 neonatal piglets
• DHCA
• RLFP at 20 or 40 mL/(kg x min)
• 18C, 90 min
• Alpha-stat principles
• Principle oxygen-dependent quenching of
  phosphorescence
• Lower cerebral oxygenation, but better recovery
  at 20 than 40 mL/(kg x min)
• Neither flow rate adequately oxygenated organs in
  lower torso

J Thorac Cardiovasc Surg 2003125472-80
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Tissue oxygen tension during RLFP in neonates
DeCampli WM, Myung R, The Childrens Hospital of
Philadelphia

• Cortical PO2
• similar to prebypass, declined during reperfusion
  at 40 mL/(kg x min)
• lower than prebypass, increased during
  reperfusion at 20 mL/(kg x min)
• PO2 20 mL/(kg x min)
• Peripheral PO2
• less than 10 mmHg at both 20 and 40 mL/(kg x min)
  
• Upper torso edema, metabolic acidosis, unstable
  recovery
• 3 of 6 piglets at 40 mL/(kg x min)
• none of 6 piglets at 20 mL/(kg x min)

J Thorac Cardiovasc Surg 2003125472-80
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RLFP improves neurologic outcome Myung RJ,
DeCampli WM, The Childrens Hospital of
Philadelphia

• 16 neonatal piglets
• DHCA or RLFP (10 mL kg1 min1)
• 18C, 90 min
• Alpha-stat principles
• Neurobehavioral scores
• postop. 1, 3, and 7 days
• 0 no deficit to 90 brain death
• Histopathologic scores
• injured and apoptotic neurons in neocortex and
  hippocampus
• HE
• TUNEL terminal deoxynucleotidyl
  transferasemediated deoxyuridine
  triphosphatebiotin nick-end labeling
• 0 no injury to 4 diffuse injury

J Thorac Cardiovasc Surg 20041271051-1057
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RLFP improves neurologic outcome Myung RJ,
DeCampli WM, The Childrens Hospital of
Philadelphia

• RLFP improves neurologic recovery and attenuates
  apoptotic neuronal death as compared with DHCA
• HE
• necrosis by CPB and hypothermia
• Apoptosis
• RLFP in delivering apoptotic inhibitors
• cortical remodeling
• ischemia and reperfusion
• cyanosis

J Thorac Cardiovasc Surg 20041271051-1057
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Cerebral monitoring to guide RLFPAndropoulos DB,
Fraser CD, Texas Children's Hospital

• Cerebral oxygen saturation and blood flow
  velocity by NIRS and TCD
• Prospective, 34 patients
• 17C to 22C
• Flow rate within 10 of baseline
• 63 mL/(kg x min) required
• Mean BP had poor correlation with required flow
  rate
• Risk for cerebral hyperperfusion
• cerebral oxygen saturation of 95 14 of 34
• CBF velocity adds valuable information to
  cerebral oxygen saturation data in guiding flow
• Use prevention of cerebral hyperperfusion with
  high NIRS saturation values

J Thorac Cardiovasc Surg 2003125491-499
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Flow and oxygenation to both hemispheres
Andropoulos DB, Fraser CD, Texas Childrens
Hospital

• Correlation of cerebral blood volume index by
  NIRS with CBF velocity by TCD
• 20 patients, 18C
• Cerebral oxygen saturations for rt and lt sides
• 95 and 87 (P 0.054)
• Median CBF velocity values did not change during
  RLFP
• Poor correlation cerebral blood volume index and
  CBF velocity
• RLFP provides comparable blood flows
  oxygenation to both hemispheres
• TCD is recommended as corroborative method with
  NIRS to guide flow

J Thorac Cardiovasc Surg 20031261712-7
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J Thorac Cardiovasc Surg 20031261712-7
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Technical Aspects of RLFP

• Advantages
• use of pump equipment/cannulas already used for
  CPB
• easy conversion from CPB
• minimization of blood by perfusion of small
  portion
• cerebral oxygenation
• mitigation of reperfusion injury
• Disadvantages
• intimal arterial injury of arch vessels
• late stenosis
• embolization of air and debris
• flow-induced injury

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Surgical techniques for RLFP

• Perfusion via PTFE graft
• Direct cerebral vessel cannulation
• Retrograde perfusion of completed shunt
• Indirect cannulation via asc aorta
• Proximal aortic arch clamping
• Direct perfusion of isolated aortic arch

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Perfusion via PTFE graft

• Used most extensively during Norwood op.
• Excellent exposure
• Arrest for transfer of cannulae
• Air embolization during cannula transfer
• Biventricular repair as primary cannulation site

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Direct cerebral vessel cannulation

• Use of thin-walled metal cannula
• Intimal injury to cerebral vessels
• Late stenosis

Ann Thorac Surg 1996611546-8
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Retrograde perfusion of completed shunt
Tchervenkov CI, The Montréal Children's Hospital

• Advantages
• reduces CPB
• improve hemodynamically during shunt
• shunt probing
• without taking out cannula
• eliminate brief arrest
• decrease cerebral air embolism
• Disadvantage impaired exposure

Ann Thorac Surg 2000701330-3
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Indirect cannulation via asc aorta
Tchervenkov CI, The Montréal Children's Hospital

• Ascending aorta is large enough
• Cannulation rt. side of distal asc aorta, near
  base of innominate a.
• Advantages
• decreased intimal damage and late stenosis
• repositioning of cannula without removal
• minimizes risk of air embolization
• Straightforward and reproducible
• Cannula not impede extent of arch augmentation

Eur J Cardiothorac Surg 200119708-710
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Proximal aortic arch clamping
Tchervenkov CI, The Montréal Children's Hospital

• Limited to distal arch
• Clamp across proximal arch just distal to
  innominate a.
• Distal arch reconstruction while maintaining
  cerebral and myocardial perfusion

Ann Thorac Surg 2001721615-1620
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Direct perfusion of isolated aortic arch
McElhinney DB, Hanley FL, University of
California, San Francisco, Calif.

• m-DKS and arch repair
• Cannula at base of innominate a.
• Perfusion flow at 30 mL/kg/min

J Thorac Cardiovasc Surg 1997114718-726
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The Montréal Children's Hospital Tchervenkov CI

• Technical challenge
• frequently diminutive ascending aorta
• use of two arterial cannulas
• direct anastomosis over significant distance btw
  dsc aorta and small asc aorta
• Venus Oxygen saturation
• continuously in venous cannula with oximeter
• lowest mixed-venous oxygen saturation 79.8
  10
• lowest oxygen saturation to venous side nearly
  80 from both SVC and IVC and suggests adequate
  oxygen delivery to upper and lower body
• useful to separate venous cannulas to measure
  difference in venous saturations btw IVC and SVC
• RLFP through innominate a. results in significant
  blood flow to lower body
• removing clamp on dsc aorta result in flooding
  with blood

Ann Thorac Surg 2001721615-1620
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Okayama University Medical School Ishino K, Sano
S

• Isolated cerebral and myocardial perfusion
• cannula to asc aorta with CoA or to PTFE graft to
  innominate a. with hypoplastic arches.
• clamp btw innominate and lt carotid a.
• flow 3050 during cerebral and myocardial
  perfusion, brain perfusion and heart beating
• 28C
• radial a. pr of 3045 mmHg

Eur J Cardiothorac Surg 200017538-542
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Eur J Cardiothorac Surg 200017538-542
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Eur J Cardiothorac Surg 200017538-542
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Eur J Cardiothorac Surg 200017538-542
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Okayama University Medical School Ishino K, Sano
S

• Advantage of decreased myocardial ischemia
• Because of flexibility of tube, extended arch
  anastomosis without interference from cannula and
  any undue tension
• Perfusion pr. at 3045 mmHg during cerebral and
  myocardial perfusion at 28C, uncertainty of flow
  distribution to two organs.
• Sano and Mee perfusion pr. at 3045 mmHg for
  isolated myocardial perfusion through asc aorta
• Uemura perfusion to dsc aorta - better U/O and
  liver enzymes
• Dr Sano perfusion to lower body help in more
  than 30 min such as Norwood op

Eur J Cardiothorac Surg 200017538-542
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Sejong General Hospital Kim WH

• pH-stat strategy
• Myocardial perfusion using T-connected line 4Fr
  cannula
• 50100 ml/kg per min
• Rt radial a. at 4050 mmHg
• Hct at 20

Eur J Cardio-thorac Surg 20032314955
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Sejong General Hospital Kim WH
Eur J Cardio-thorac Surg 20032314955
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Sejong General Hospital Kim WH
Eur J Cardio-thorac Surg 20032314955
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Sejong General Hospital Kim WH

• Flow rate 50100 ml/kg per min at rt radial a.
  pr. of 4050 mmHg
• myocardial blood flow of 15 ml/kg per min
• similar to Ishino's report 3050 of full flow
  and arterial pr. at 3045 mmHg in 28 C
• Low Hct facilitated CBF and oxygen delivery with
  rheologic benefits
• Lower temp. had beneficial effects on myocardial,
  spinal, and cerebral protection
• Direct cannulation of innominate a. neonate of
  1.6 kg 16 G angiographic catheter
• HLHS cannula change to neo-aorta and shunt at
  more distal innominate a.
• Myocardial perfusion in deep hypothermia
  extremely slow and empty beating
  no signs of dilatation
  or functional derangement

Eur J Cardio-thorac Surg 20032314955
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National Cardiovascular Center, Osaka Uemura H

Eur J Cardiothorac Surg 200120603-608
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National Cardiovascular Center, Osaka Uemura H

• Circulatory arrest avoided in 7 with more than 4
  kg.
• Perfusion to upper body and heart in asc aorta of
  greater than 6 mm
• 3.5 mm PTFE to rt subclavian a. or asc aorta
  directly using 1.8 mm tube
• Second cannula (straight 8 or 10 French tube),
  directly to dsc aorta beyond PA
• Standard perfusion for amount of flow,
  temperature

Eur J Cardiothorac Surg 200120603-608
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National Cardiovascular Center, Osaka Uemura H

• Results
• Postoperative courses were less eventful
• U/O during CPB was significantly greater
• Better results in postop lab lower CPK, GOT
• Lower Urinary ?-microglobulin
• Advantages
• Ischemia of lower body minimized by perfusion to
  dsc aorta.
• Temp. not lower than 25C - minimize coagulation
  disorders
• CPB times and op times were not longer
• 2nd cannula at distal dsc aorta at diaphragm in
  extensive aortic reconstruction
• This technique less ischemic damage and less
  invasive than arrest

Eur J Cardiothorac Surg 200120603-608
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Conclusions

• Regional perfusion techniques are safe and
  reproducible, and appear to be associated with
  low incidence of early adverse neurologic
  outcomes.
• Recent evidence suggest significant somatic
  circulatory support both above and below
  diaphragm which may also reduce non-neurologic
  morbidity.
• However, optimal flow rate, temperature, and safe
  duration of RLFP are still questionable,
  long-term data on neurodevelopmental outcomes are
  now needed to show superiority of low-flow
  techniques over DHCA in improving quality of
  life.

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Our progress in the surgical treatment congenital
heart disease has been such that survival is
expected. Our next challenge is to assure that
these patients survive uninjured, without
permanent neurological deficits. Developing
alternatives to circulatory arrest is an
important step toward meeting this challenge, and
we have the technical skills and creativity that
renders the use of circulatory arrest the
exception, rather than the rule, in neonatal
heart surgery.
-Pigula-