ANESTHESIA & ANALGESIA - IARS

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ABSTRACTS ANESTH ANALG
2004; 98; S-1–S-282
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FUNCTIONAL AND HISTOLOGIC DAMAGE OF THE NEONA-
TAL BRAIN IN A PIGLET LOW-FLOW CARDIOPULMONARY
BYPASS MODEL
AUTHORS: A. W. Loepke 1 , J. Golden 2 , J. C. McCann 1 , L. Staple 2 ,
C. D. Kurth 1 ;
AFFILIATION: 1 Institute for Pediatric Anesthesia, Cincinnati
Children's Hospital Medical Center, Cincinnati, OH, 2 Children's
Hospital of Philadelphia, Philadelphia, PA.
INTRODUCTION: Hypothermic low-flow cardiopulmonary bypass
(LF-CPB) and deep hypothermic circulatory arrest (DHCA) facilitate
surgical repair of complex congenital heart defects. Because outcome
studies have documented advantages of LF-CPB compared with
DHCA, LF-CPB is becoming more popular, but is still associated with
lower intelligence and other neurobehavioral deficits.(1) Whereas
neuropathology has been described for DHCA, it remains uncertain
after LF-CPB.(2) Our study characterized the neuropathology in a piglet
LF-CPB model.
METHODS: Piglets (n=14, age 3-5 days) were anesthetized with
fentanyl/ droperidol, intubated, ventilated, and cannulated in the carotid
artery and external jugular vein for CPB. Invasive blood pressure, pH,
blood gases, cortical blood flow (laser Doppler flowmetry), hematocrit,
and glucoses were monitored. Brain, esophageal, and rectal
temperatures were recorded. Animals underwent hypothermic CPB
with ph-stat management until 22 °C (brain), followed by LF-CPB for
150 min, followed by rewarming, separation from CPB, extubation and
recovery for 2 days. Brains were perfuse-fixed and cerebral injury was
assessed histologically after H&E staining.
RESULTS: During LF-CPB, MAP was 9±2 mmHg and pump flow of
9±4 ml/kg/min. Cooling and rewarming times were 21±6 min and 36±5
min, respectively. Cerebral cortical blood flow during LF-CPB was
12±6% (n=7) of pre-CPB. After CPB, 5 animals died prematurely: 4
from cardiovascular and 1 from neurologic cause. One day after CPB
functional impairment in survivors (n=9) was assessed as mild in 11%,
moderate in 33% and severe in 11%; 44% showed no disability. Two
days after CPB functional disability improved to mild in 22%, and
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ANTI-ENDOTOXIN-CORE ANTIBODY LEVELS IN
VOLUNTEER BLOOD DONORS
AUTHORS: M. Rashid 1 , M. Siva 1 , R. Stephens 1 , M. Grocott 1 , M.
Contreras 2 , M. Mythen 1 ;
AFFILIATION: 1 Institute of Child Health and Great Ormond
Street Hospital, London, United Kingdom, 2 H&I, National Blood
Service, Colindale, London, United Kingdom.
INTRODUCTION: Endotoxin plays a central role in sepsis and organ
dysfunction after surgery. Levels of one of our natural defences against
endotoxin, anti-endotoxin core antibody (EndoCAb), are an
independent predictor of post-operative outcome 1 ; high pre-operative
titres having been associated with a better outcome 2 . However, there is
heterogeneity in EndoCAb levels between individuals, within, and
across populations, that remains to be explained. The aim of this study
was to determine EndoCAb levels in a blood donor population.
METHODS: Blood samples were collected from consented blood
donors and the sera separated. EndoCAb levels were determined using
an ELISA protocol 3 . Briefly, 100 100µl of diluted test or standard
sample were transferred onto an ELISA plate that had been pre-coated
with endotoxins from 4 bacterial species and blocked with bovine
serum albumin for 1 hour at 37°C. The bound antibodies were then
incubated for 1 hour at 37°C with alkaline-phosphatase-conjugated
goat-anti-human IgG or IgM antibody. Between each step, the plate was
washed with PBS/Tween 20, containing sodium azide. The
chromogenic reaction was performed with para-Nitrophenyl phosphate
dissolved in a diethanolamine buffer. The reaction was terminated with
NaOH and the absorbance read at 405nm. A dual wavelength system
with subtraction of a reference wavelength (650nm) was used. The
EndoCAb levels of test samples were obtained from a standard
calibration curve.
RESULTS: The median IgG EndoCAb level for this population was
141.2 MU/ml (IQR: 84.9 - 238.4 MU/ml). The 95th centile was 576.2
MU/ml. The median IgM EndoCAb level was 226.9 MU/ml (IQR:
138.2 - 365 MU/ml). The 95th centile was 642.6 MU/ml. The cut-off
point for hyperimmune plasma in a previous study was 400 MU/ml4.
moderate in 22% animals; 56% animals showed no disability, no animal
was rated as severely impaired. Regardless of functional assessment, all
animals showed histologic brain damage by 48 hours. Brain damage
was moderate to severe in neocortex and hippocampus and mild in basal
ganglia, thalamus, white matter, and cerebellum and not observed in the
brain stem (Figure 1). Cell death appeared mainly as selective neuronal
necrosis in layers 4-6 in neocortex and CA1-4 sections in hippocampus,
less so apoptosis; no cerebral infarction was observed. Severity of
hippocampal damage inversely correlated with pCO 2 during LF-CPB
(r 2 =-0.85, p=0.003) and rewarming (r 2 =-0.83, p=0.006). Neocortical
damage inversely correlated with pCO 2 on rewarming (r 2 =-0.84,
p=0.005).
DISCUSSION: Brain damage following LF-CPB is similar yet
different from that caused by DHCA. The vulnerable areas include
neocortex and hippocampus in both, appearing as selective neuronal
death and rarely infarction. Neuronal death after LF-CPB appeared as
necrosis most often in deep gray matter (layer 4-6), a watershed area.
Conversely, neuronal death after DHCA appeared apoptotic, typically
in superficial gray matter (layers 2 and 3). Even with pH-stat
management, higher pCO 2 during LF-CPB and rewarming reduces
brain damage.
REFERENCES:
1.Circulation 1999; 100(5): 526
2.J Thorac Cardiovasc Surg 1999; 118(6): 1068
Based on 4 times the median value, the cut-off point for IgG
hyperimmunity for this population was 564.8 MU/ml. We identified 27
(5.4%) IgG hyperimmune individuals.
DISCUSSION: The 501 donors screened for EndoCAb levels show a
median IgG and IgM level of 141.2 and 226.9 MU/ml, respectively.
This is higher than a reported Scottish population where the median for
both IgG and IgM was 100MU/ml. In this study individuals differ in
their IgG levels by up to 85-fold and in their IgM levels by up to 122fold.
These observed differences between individuals remain
unexplained. Possible reasons for these differences may include prior
exposure to endotoxins, differences in HLA-genotypes, particularly,
class II genes, which may affect differences in antigen presentation, and
other factors known to bind endotoxin such as high density lipoprotein
cholesterol and bactericidal permeability increasing protein. No
correlation between IgG and IgM EndoCAb levels within individuals
was observed. Within our population, 5.4% of individuals were IgG
hyperimmune.
REFERENCES: 1) Chest (1997) 112; 1189-1196.
2) Anesthesiology (2001) 94; 992-998. 3) Serodiag. Immunother.
(1990) 4; 25-38. 4) Vox Sanguinis (1996) 71; 165-169.