Presentation on theme: "Deep Hypothermic Circulatory Arrest in Pediatric Cardiac Surgery 2009"— Presentation transcript:
1 Deep Hypothermic Circulatory Arrest in Pediatric Cardiac Surgery 2009 Nabila Fahmy, MDProfessor of AnesthesiologyAin Shams University
2 Cessation of the blood circulation for some time during surgery of the arch and repair of congenital heart defects is normally required to allow a bloodless operation field..Hypothermia is the most important mechanism for end-organ protection, particularly the brain, during such operations.Cardiopulmonary bypass is used for core cooling before deep hypothermic circulatory arrest (DHCA) is initiated .
4 DEEP HYPOTHERMIC CIRCULATORY ARREST (DHCA) Mild hypothermia – 30 C to 34 CModerate hypothermia – 25 C to 30 CDeep hypothermia – 15 C to 22 CCirculatory arrest – no flow in the blood vesselsDHCA – no blood flow during deep hypothermia
6 TECHNIQUE OF DHCA Usually planned Most protocols involving DHCA involve the following :Administration of barbiturates, usually thiopental for the reduction of cerebral metabolism.Mannitol to help reduce potential increased intracranial pressure and to reduce free radicals.Steroids to promote cell membrane integrity and reduce brain swelling.Cooling is started before CPB by simply cooling the operating room and with ice packing to the head After systemic heparinization and cannulation are performed, CPB is started and cooling is begins for at least minutes. The patient's body temperature is monitored by means of esophageal, tympanic, and rectal routes. After adequate cooling is achieved, the circulation is arrested to allow the surgeon to perform the critical part of the reconstruction. The duration of DHCA is limited to the shortest time possible. After circulation is restarted, the rest of the repair is performed during the rewarming phase.The anesthetic and surgical plan involves mutual goals of tissue and organ protection by decreasing cellular metabolism and substrate delivery during the absence of perfusion.
8 ADVANTAGES OF DHCA Bloodless operating field with improved exposure Decreased exposure to cardiopulmonary bypass with its sequelae (such as activation of white cells and endothelium, activation of cascades, consumption of coagulation factors and platelets, hemolysis, etc.)Diminished risk of embolism (solids and gases)No cannulas in the operating fieldLess distortion of heart - cannulas are not in placeDHCA offers brain protection for a period of about minutes.Reduced CMRO2 to be approximately 10%-15% of its normothermic base line.Lower plasma activated complement (C3a), interleukin 8, interleukin 6 (when compared with low-flow CPB)Bellinger DC, et al. N Engl J med. 1995;332:
9 The duration of DHCA is limited to the shortest time possible as (landmark boston circulatory arrest study, march 2007)3-5 mins of cerebral ischemia can be tolerated at 37 c.15 mins c.41 mins c.
11 CEREBRAL PHYSIOLOGY DURING CARDIAC SURGERYCLINICAL STUDIES (Greeley, Kern, Ungerdeider)HAVE BEEN UNDERTAKEN IN THE LATE 1980sTRHOUGH MID 1990s TO UNDERSTANDNEUROPHYSIOLOGY IN INFANTS AND CHILDRENDURING CARDIAC SURGERY INVOLVING CPBAND DHCACNS HAS A HIGH METABOLIC NOTE & LIMITED ENERGY STORESCNS IS THE MOST SENSITIVE ORGAN TO ISCHEMIAATTENTION HAS BEEN CENTERED ON NEUROLOGIC OUTCOME WHEN PERFUSION IS REDUCED, LEADING TO NEUROLOGIC COMPLICATIONS IN THE POSTOPERATIVE PERIOD.
12 THE REPORTED INCIDENCE OF NEUROLOGICAL COMPLICATIONS AFTER PEDIATRIC CARDIAC SURGERYRANGES FROM 2% TO 25%Austin EH III,Edmonds HI,Auden SM et al.Benefit of neurophysiological monitoring for pediatricCardiac surgery.J Thorac Cardiovasc Surg 1997;114 :707-15Menache CC,du Plessis AJ,Wessel DL et al.Current incidence of acute neurologic complicationsAfter open heart operation in childrenAnn Thorac Surg 2002; 73:1752.8
13 Neurologic morbidity include seizuresstrokechanged tone and mental statusmotor disorders -time to recovery of EEG activity .Abnormal cognitive functionPost Pump choreoatherosis paraplegiaAreas most vulnerable to ischemic Injury :NeocortexHippocompusStriatum
14 mechanism of brain injury involves binding of glutamate to NMDA receptor , increasing the intracellular ca++ and subsequently activates proteases phospholipases and deoxyribonucleases , promotes the generation of free radicals cell injury , cell death .Hypothermia the release of glutamateDuring DHCA , microemboli can be detected .
15 THE ETIOLOGY OF NEUROLOGICAL DYSFUNCTION IN CHILDREN IS FOR THE MOSTPART ISCHEMIAPATHOPHYSIOLOGIC MECHANISMS ACCOUNTINGFOR NEUROLOGIC INJURY INCLUDE:rate and extent of cooling and rewarmingmanagement of CPBprolonged DHCAanemialow cardiac output
18 UNDER DEEP HYPOTHERMIC CPB CBF IS REDUCED BUT THERE IS AN EXPONENTIALLY GREATER REDUCTIONIN CMRO2.A STATE OF LUXURY PERFUSION EXISTSWITH AN EXCESS OF FLOW RELATIVETO OXYGEN CONSUMPTION; 1:75 (conferring cerebral protection)IN PATIENTS UNDERGOING DHCA CBF ANDCMRO2 REMAIN DECREASED AFTERREWARMING AND WEANING FROM CPBSara Lozano, MD , Emad Mossad, MD – Journal of Cardiothoracic and Vascular Anesthesia. Volume 18, Issue 5, Pages (October 2004)
21 Acid -- Base Management BLOOD GAS MANAGEMENT (a-stat vs pH-stat)DURING CPB SIGNIFICANTLY AFFECTSCEREBRAL PHYSIOLOGY AN MAY HAVEAN IMPACT ON NEUROLOGICAL OUTCOME############# من هنا
22 pH-stat strategy – adding carbon dioxide - compensates for this shift. Changes in cellular pH during hypothermia are mediated through pco2 homeostasis.When blood is cooled during cardiopulmonary bypass, pH becomes more alkaline.pH-stat strategy – adding carbon dioxide - compensates for this shift.This situation causes pH to increase as temperature decreases and electrochemical neutrality to be maintained.Carbon dioxide is a potent cerebral vasodilator.α-stat strategy – electrochemical neutrality is maintained by keeping pH normal in temperature-uncorrected gases.22
23 i.e,α-stat strategy – arterial blood measured at 37 C with pH of 7.40 and arterial pCO2 of 40 mm Hg(the hypothermic blood is alkalemic and hypocapneic)pH-stat strategy – hypothermic arterial blood at pH of 7.40 and arterial pCO2 of 40 mm Hg(blood at 37 C is acidemic and hypercapneic)
25 ADVANTAGES/DISADVANTAGES α-stat strategy: preserves autoregulation, optimizes cellular enzyme activity, but less metabolic suppressionpH-stat strategy: improves cerebral blood flow, cerebral oxygenation, and brain cooling efficiency during CPB, but greater risk of microembolism and free radical-mediated damage25
26 Higher Hematocrit Improves Cerebral Outcome After Deep Hypothermic Circulatory Arrest Extreme hemodilution (hematocrit < 10%) causes inadequate oxygen delivery during early cooling and higher hematocrit (30%) achieved with blood prime results in improved cerebral recovery after circulatory arrest.Shin’oka T, Shum-Tim D, Jonas RA, Lidov HGW, Laussen PC, Miura T and du Plessis AChildren’s Hospital Boston/Harvard Medical SchoolJ Thorac Cardiovasc Surg 1996;112:26
27 Temperature Management No difference between surface and core cooling. Provide adequate duration of cooling (> 20 min) before institution of DHCA. Avoid rapid cooling, avoid rapid rewarming and hyperthermia in postoperative period.Sharma R, et al. Neurological evaluation and intelligence testing in the childwith operated congenital heart disease. Ann Thorac Surg 2000; 70: 575–581Cottrell SM et al. Early postoperative body temperature and developmentaloutcome after open heart surgery in infants. Ann Thorac Surg 2004; 77: 66–71
29 Current recommendations and results of clinical trials DrugBasisCurrent recommendations and results of clinical trialsPre-operative use ofmethyl prednisoloneLesser inflammatory responseafter CPB;cerebral function recoversearlier.Intravenous methyl prednisolone10 mg/kg administered 8 hoursand 2 hours prior to surgery in highrisk groups like neonatesBarbituratesSuppresses EEG activity; cancause reductionin high-energy phosphateswhich isdetrimental after circulatoryarrest.Not recommended prophylacticallyAprotininBeneficial effect on recoveryof cerebral highenergy phosphates andintracellular pH.No clear evidence favoring use in pediatric CPB.
30 Allopurinol, NACMay reduce injury due tofree radicals. NACmay improve myocardialfunction.No clear data.NMDA antagonists(magnesium, selfotel)Reduce excitotoxicityNo benefit in human trials.Nimodipine (calcium channel antagonist)Reduces cellular injury mediatedby calcium influx during reperfusion.Negative results in human stroke trials.Erythropoetin (EPO)EPO switches off apoptosisLimits excitotoxic cell deathMediated by NMDA - RBlocks the inflammatory cascadeEPO is a cerebral vasodilatorEPO 1000 units/kg IV for 3 doses –12 hours pre-op / after CPB then 24hours after.
31 Slowing of neuronal metabolism Slow apoptosis and block iCa++ Inhaled anestheticsIsofluraneDesfluraneSlowing of neuronal metabolismSlow apoptosis and block iCa++neuronal injury and death.Be placed in the CPB sweep gas flowVasodilationIt would appear desirable to use this agents liberally on CPB.Even seeking to achieve a target blood level while cooling. Especially if DHCA or other such techniques are to be used.CPB: cardiopulmonary bypass; EEG: electroencephalograph; NAC: N-acetyl cysteine; NMDA: N-methyl D-aspartateLangley SM, et al. Eur J Cardiothorac Surg 2000.Clancy RR, et al. Pediatrics 2001.Miller SP, et al. Ann thorac Surg 2004.Bickler PE, Fahlman CS. Anesth Analg 2006, 103.
33 EEGit is a rough guide to anesthetic depthit is affected by temperature,CPB,anestheticsnot easy to useBIS (BISPECTRAL INDEX)it is currently used to guide the depth of anesthesiaeasy to use - less reliable during hypothermiaSjVO2 (JUGULAR VENOUS BULB OXYMETRY)it is considered the gold standard of global cerebraloxygenationit is invasiveUnilateral SjVO2 may not reflect contralateral events
34 TCD (TRANSCRANIAL DOPPLER ULTRASOUND) it is a sensitive real-time monitor of CBF, can detect microemboliit monitor the middle cerebral arteryAbsent signal during DHCA.S- 100B (Biochemical marker)Detects preexisting neurologic deficitMultiple sampling periods requiredNIRS (NEAR-INFRARED SPECTROSCOPY)it is a non-invasive optical techniquemost devices utilize 2-4 wavelengths of infrared lightat nm, where oxygenated and deoxygenatedhemoglobin have distinct absorption spectratwo depth of light penetration are used to subtractout data from the skin and skull resulting in brainoxygenation valueChanges in cerebral vascular composition will affect rSO2 readingUseful during DHCA.
37 ConclusionSurvival after neonatal and infant cardiac surgery has improved dramatically, but quality of life, including neurodevelopmental outcomes, still needs study and improvement. It is important to protect the brain using established strategies,and test new strategies with carefully designed follow-up studies. Potential exists for significant improvement in this area.