Anna Cazzaniga ,MD
Istituto Policlinico San Donato
Milan
THE REPORTED INCIDENCE OF
NEUROLOGICAL COMPLICATIONS
AFTER PEDIATRIC CARDIAC SURGERY
RANGES FROM 2% TO 25%
Austin EH III,Edmonds HI,Auden SM et al.
Benefit of neurophysiological monitoring for pediatric
Cardiac surgery.J Thorac Cardiovasc Surg 1997;114 :707-15 Menache CC,du Plessis AJ,Wessel DL et al.
Current incidence of acute neurologic complications After open heart operation in children
THE ETIOLOGY OF NEUROLOGICAL
DYSFUNCTION IN CHILDREN IS FOR THE MOST PART ISCHEMIA
PATHOPHYSIOLOGIC MECHANISMS ACCOUNTING FOR NEUROLOGIC INJURY INCLUDE:
rate and extent of cooling and rewarming management of CPB
prolonged DHCA anemia
CEREBRAL PHYSIOLOGY DURING CARDIAC SURGERY
•CLINICAL STUDIES (Greeley, Kern, Ungerdeider)
HAVE BEEN UNDERTAKEN IN THE LATE 1980s TRHOUGH MID 1990s TO UNDERSTAND
NEUROPHYSIOLOGY IN INFANTS AND CHILDREN DURING CARDIAC SURGERY INVOLVING CPB
•CEREBRAL BLOOD FLOW IS MEASURED
BY THE XENON CLEARANCE METHOD IN PATIENTS DURING HYPOTHERMIC CPB AND CEREBRAL OXYGEN EXTRACTION IS MEASURED BY OXYGEN SATURATION IN THE ARTERIAL FLOW AND IN JUGULAR VENOUS BULB
CMRO2= CBF x (CaO2 – CjVO2)
CMRO2= cerebral metabolic rate for oxygen CaO2= Oxygen content of arterial blood
CjVO2= Oxygen content of jugular venous bulb blood
•UNDER DEEP HYPOTHERMIC CPB
CBF IS REDUCED BUT THERE IS AN
EXPONENTIALLY GREATER REDUCTION IN CMRO2
•A STATE OF LUXURY PERFUSION EXISTS
WITH AN EXCESS OF FLOW RELATIVE TO OXYGEN CONSUPTION
•CMRO2 DECREASES BY 3.65 TIMES FROM
BASELINE (37°C) TO 27°C AND DECREASES 3.65 x 3.65 AT 17°C
•FROM THESE DATA THE INVESTIGATORS
DERIVED A “SAFE” DURATION OF DHCA AT VARIOUS TEMPERATURES
11-19 minutes at 28°C 39-65 minutes at 18°C
•IN PATIENTS UNDERGOING DHCA CBF AND
CMRO2 REMAIN DECREASED AFTER
•ANOTHER IMPORTANT FACTOR IS
AUTOREGULATION OF CBF DURING COOLING
TAYLOR ET AL IN 1992 DEMONSTRATED THAT CEREBRAL AUTOREGULATION IS
PRESERVED DURING NORMOTHERMIC CPB BUT DURING BOTH MODERATE AND
PROFOUND HYPOTHERMIA FLOW BECAME PRESSURE-PASSIVE INCREASING
•CBF RESPONSE TO CHANGES IN ARTERIAL
CARBON DIOXIDE TENSION IS PRESERVED IN CHILDREN (Kern et al in 1991)
•BLOOD GAS MANAGEMENT (a-stat vs pH-stat)
DURING CPB SIGNIFICANTLY AFFECTS CEREBRAL PHYSIOLOGY AN MAY HAVE
Kern FH,Ungerdeider RM,Reves JG
Effect of altering pump flow rate on cerebral blood Flow and metabolism in infants and children
Ann Thorac Surg 1993;56:1366-72
•AT MODERATE AND DEEP HYPOTHERMIA
REDUCTION OF 35-45% FROM CONVENTIONAL FULL BYPASS FLOW RATES RESULTED IN NO
CHANGES IN CBF AND CMRO2, BUT CBF AND CMRO2 SIGNIFICANTLY DECREASE WITH AN
ASSOCIATED INCREASED IN OXYGEN EXTRACTION (SjVO2) WHEN FLOW IS REDUCED OF 45-70%
° FROM THESE DATA THE AUTHORS DERIVED MINIMAL ACCEPTABLE PUMP FLOW RATES AT VARIOUS TEMPERATURES
° PUMP FLOW RATES AT VARIOUS TEMPERATURES ARE VALIDATED IN A STUDY INVOLVING
NEONATES UNDERGOING ARTERIAL SWITCH OPERATION AND CBF WAS DOCUMENTED WITH TRANSCRANIAL DOPPLER ULTRASOUND
( Zimmermann AA,Burrows FA, Jonas RA,Hichey PR The limits of detectable cerebral perfusion by
transcranial doppler sonography in neonates undergoing deep hypothermic low-flow cardiopulmonary bypass
•EEG
it is a rough guide to anesthetic depth
it is affected by temperature,CPB,anesthetics not easy to use
•BIS (BISPECTRAL INDEX)
it is currently used to guide the depth of anesthesia easy to use
•SjVO2 (JUGULAR VENOUS BULB OXYMETRY)
it is considered the gold standard of global cerebral oxygenation
•TCD (TRANSCRANIAL DOPPLER ULTRASOUND)
it is a sensitive real-time monitor of CBFV and emboli it monitor the middle cerebral artery
•NIRS (NEAR-INFRARED SPECTROSCOPY)
it is a non-invasive optical technique
most devices utilize 2-4 wavelengths of infrared light at 700-1000 nm, where oxygenated and deoxygenated hemoglobin have distinct absorption spectra
two depth of light penetration are used to subtract out data from the skin and skull resulting in brain oxygenation value
THE DEVICE DISPLAYS A NUMERICAL VALUE THE MEASURED REGIONAL CEREBRAL
•THIS INDEX ASSUMES THAT 75% OF THE
CEREBRAL BLOOD VOLUME IS VENOUS AND 25% IS ARTERIAL
•BASELINE PREOPERATIVE VALUE IS
about 70% IN ACYANOTIC PATIENTS and 40-60% IN CYANOTIC
•NIRS VALUE DECREASE DURING HEMODYNAMIC
INSTABILITY OR ARTERIAL DESATURATION OR REWARMING
•NIRS VALUE INCREASES DURING COOLING AND
IMPROVEMENT IN CARDIAC OUTPUT
•NIRS VALUE DECREASES DURING DHCA TO A
NADIR 60-70% BELOW BASELINE AND THE NADIR IS REACHED AT ABOUT 40 MINUTES, REPERFUSION IMMEIATELY RESULTS IN AN INCREASE
CPB WITH DEEP HYPOTHERMIA WITH
CONCLUSION
•FOR THE NIRS MONITOR EACH PATIENT IS
A CONTROL FOR HIMSELF AND A RELATIVE DECREASE OF MORE THAN 20% FROM THE
BASELINE IS AN INDICATION FOR TREATMENT
•MULTIMODALITY NEUROLOGICAL MONITORING
IS THE BEST OPPORTUNITY TO DETECT AND TREAT NEUROLOGICAL DYSFUNCTION
BUT TOMORROW WHAT SHALL I DO WHEN NIRS VALUE DECREASES :
YOU HAVE TO CHECK:
•Ventilation
•Cardiac contractility
•Adequate volemia and hematocrit •Increase anesthetic depth
•Neuroprotective agents
AND IF YOU ARE ON CPB:
•Check cannula position •Cool the patient
NIRS CAN BE USEFUL ONLY
CARDIAC OUTPUT IS AFFECTED BY: PRELOAD AFTERLOAD RATE RHYTHM CONTRACTILITY PRESENCE OF SHUNT
OXYGEN DELIVERY (DO2) IS A FUNCTION OF CARDIAC OUTPUT
THE SYMPHATETIC STRESS RESPONSE IS
ACTIVATED IN ALL SHOCK STATES IN ORDER TO REDISTRIBUTE BLOOD FLOW TO BRAIN AND HEART
THE DISTRIBUTION OF CARDIAC OUTPUT CAN BE SIGNIFICANTLY ALTERED WITH
MESENTERIC AND SPLANCHNIC CIRCULATION BEING AT RISK FOR ISCHEMIA
COMPELLING EVIDENCE EXISTS THAT SPLANCHNIC/ MESENTERIC ISCHEMIA IS A FREQUENT COMMON PATHWAY TO MULTIORGAN DYSFUNCTION
AND DEATH
Hoffman GM, Ganayem NS, Twelled JS Noninvasive assessment of cardiac output
Semin Thorac Cardiovasc Surg Ann 2005; 8:12-21 ASSESSMENT OF CARDIAC OUTPUT:
clinical examination
Thermodilution techniques SVO2
•SvO2 (VENOUS OXYGEN SATURATION)
The saturation of mixed venous blood is commonly used to Assess the adequacy of whole body oxygenation
As it reflects the balance between oxygen delivery and consuption
SvO2 = SaO2 – VO2 / DO2
Blood from SVC is commonly used as a proxy for True mixed venous blood or when a PA catheter Is absent
Other studies confirmed that in neonates both cyanotic And acyanotic the threshold for anaerobic metabolism Occur at a SvO2 near 30%
•REGIONAL SvO2: NEAR INFRARED SPECTROSCOPY
it is a new vital sign
the sensor must be plased on the thoraco-lumbar (T10-L2) somatic (renal) region and captures the oxygenation of tissue 2.5-3 cm beneath the sensor
there are only a few instances where NIRS can be impacted: Jaundice, severe tissue edema and
MIXED SVO2 IS A FLOW-WEIGHTED AVERAGE OF REGIONAL SATURATION OF ALL ORGANS, THEN MIXED SVO2 COULD BE ACCURATELY APPROXIMATED IF MULTIPLE REGIONAL SATURATION MEASURES ARE AVAILABLE
HOFFMAN USES THE TWO SITES (CEREBRAL AND SOMATIC) NIRS TO MONITOR REGIONAL SATURATION IN PERIOPERATIVE PERIOD
THE TWO-SITE APPROCH REVEALS THE DIFFERENCE IN TISSUE OXYGENATION IN DIFFERENT ORGAN BEDS BRAIN OXYGEN EXTRACTION IS RELATIVELY HIGH
AND TIGHT FLOW-METABOLISM COUPLING IS ACHIEVED BY AUTOREGULATION RESULTING IN MINIMAL CHANGE IN CBF RELATED TO
SYMPATHETIC TONE
KIDNEY IS NORMALLY A HIGH-FLOW ,LOW-EXTRACTION ORGAN ,BUT RENOVASCULAR
RESISTANCE IS UNDER INTENSE SYMPATHETIC CONTROL
THE TWO ORGANS REPRESENT OPPOSITE POLES OF REGIONAL CIRCULATION
Hoffman GM,Ghanayem NS, Stuth ES et al
NIRS-derived somatic and cerebral saturation difference Provides non-invasive real-time hemodynamic assessment Of cardiogenic shock and risk of anaerobic metabolism Anesthesiology 2004;99:A1448
ADEQUATELY PERFUSED PATIENTS HAVE SOMATIC VALUES 10- 15 POINTS HIGHER THAN CEREBRAL
IF THE SOMATIC VALUE DROPS BELOW THIS IT MAY BE A SIGN THAT THE PERIPHERAL CIRCULATION IS SHUTTING DOWN TO
PRESERVE THE BRAIN: A POTENTIAL EARLY INDICATOR OF SHOCK
NIRS READINGS ARE NOT PULSE, PRESSURE OR TEMPERATURE DEPENDENT
NIRS CAN BE USED DURING:
•CPB •DHCA •ECMO •SHOCK
