lecture 1 basic concept on neuroanesthesia 2
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BASIC CONCEPT ON NEUROANESTHESIA
ISNACC
Objective
• To understand technique and anesthetic effect to reach slack brain.
• To understand technique and anesthetic effect to CBF, ICP, autoregulation, CO2 reactivity, CMRO2.
• To understand perioperative management.• To understand mechanism of brain protection and how to
give brain protection.
Cotrell J.E. : Anesthesia for Neurosurgery, 1994
New diagnostic equipment
New monitoring equipment
New anesthetics
New understanding common drugs for neuroanesthesia.
Will be improve outcome in patient with intracranial
disorder.
Anesthesiologist target in neurosurgery Control ICP and brain volume.
Brain protection from ischemia and injury.
Less bleeding
Nancye Edwards : Principles and Practice of Neuro anaesthesia, 1991
The relation ICP and mortality in brain injury
Mean ICP (mm Hg) Mortality (%)
0 - 20 19
21 - 40 28
41 - 80 79
Miller JD : Head injury and brain ischemia implication for therapy Br. J Anaesth. 57 : 120 - 129 , 1985
Figure: Idealized intracranial pressure volume relationships. From: Shapiro, H.M. Intracranial hypertension: Therapeutic and anaesthetic considerations. Anesthesiology 43: 445-471, 1975
Autoregulation:
• Keep until 1,5 MAC Sevoflurane
Gupta et al, Br.J.Anaeth,1997 Summors et al, Anesth Analg , 1999.• Autoregulation loss at 1,5 MAC Isofluran. Matta et al, Anesth Analg, 1999.• One of reasoning: effect dilatation Sevo < Iso
Lam JMK et al, J. Neurosurg, 1997
auto regulation + 5/10 Good outcome
auto regulation + 4/10 Good outcome
auto regulation – severe disability 2
death 9
Mild head injury : 9/29 impairment autoregulation
Methods of brain protection
• Basic methods• Hypothermia - low normothermia• Pharmacology Intravenous Anesthetic : pentothal Inhalation anesthetics: Sevoflurane Lidocaine Mannitol, Magnesium Erythropoietin Alpha 2 agonists dexmedetomidine
Basic methods• Control airway, adequate oxygenation, avoidance
hypoxia, hypercapnia (keep normocapnia).• Hyperventilation only if herniation present.• Control of BP/Maintenance of CPP normotension or
induce hypertension 10-20%. CPP >70 mmHg.• Control ICP (CPP = MAP – ICP). Therapy if ICP 20
mmHg.• Correction of acidosis, electrolyte imbalance,control
plasma glucose concentration
Mortality:
Head injury with : Hypoxia : 56% Hypovolemia : 64% Hypoxia + Hypovolemia : 76% Without hypoxia+Hypovolemia : 27%
Asean Congress of Anaesthesiologist, Singapore, 1995.
Anesthesia management : b
A = Clear airway B = Control ventilation, normocapnia at TBI and slight
hypocapnia at brain tumor. C = Avoid high increase or decrease of BP, avoid
increase of cerebral venous pressure. normovolemia, iso-osmoler.
D = Avoid drugs & anesthesia technique will increase ICP, give drugs with brain protection effect.
E = environment (temperature control) target 35 degree C in OR
Airway
• Clear airway at all the operation and anesthesia.• Non kinking ETT• hypoxia or hypercarbia dangerous to patient.
Ventilation to reach :
PaO2 : 100 - 200 mmHg
PaCO2 : 25 - 30 mmHg for brain tumor surgery
PaCO2 : Normocapnia in brain injury
Avoid PaCO2 < 20 mmHg
Control ventilation
Regulation BP
Hypotension :
CPP = MAP - ICP prefer systolic 90 - 100 mmHg (tumor)
Normotension (trauma)
Hypertension :
- increase CBV, ICP, edema, blood loss. - during laringoscopy/intubation, inserting head pin, skin incision, extubation
Mechanical factor which increase
cerebral venous pressure
Coughing, bucking Trendelenburg Neck large vein obstruction Abdominal pressure PEEP internal jugular vein / subclavia vein canulation
Preoperative evaluation
Similar with routine assessment
Add : - evaluation ICP, side effect therapy
- CT Scan, MRI
Premedication :
- avoid narcotic - diazepam 0,15 mg/kg po
- midazolam 0,025 - 0,05 mg/kg im
- children : midazolam 0,75 mg/kg po
Intraoperative anesthetics
1. Monitoring
2. Induction of anesthesia
3. Maintenance of anesthesia :
- inhalation anesthetics (Sevoflurane, isoflurane)
- intra venous anesthetics (pentothal)
- brain relaxation
- Fluid management
4. Emergence and immediate postoperative
Monitoring
Routine monitoring
ECG, non invasive BP, CVP, invasive BP (artery line), FiO2, pulse oximetry, temperature, peripheral nerve stimulator, catheter urine.
Indication for inserting artery line
Rapid changes of BP
Risk of rapid blood loss.
Hypotension technique
Pathologic condition
Need postoperative ventilation.
Indication for CVP monitoring
Severe blood loss
Measurement status volume
Sitting position / fossa posterior surgery
vasoactive drugs route
ICP Monitoring
still controversial
tumor > 3 cm Need ICP monitoring
Edema
Target induction of anesthesia Control of PaCO2
Control of BP
Avoid drainage obstruction of cerebral vein
Adequate oxygenation & ventilation
Avoid awareness
Induction of anesthesia O2 100% Fentanyl 1 - 3 ug/kg Pentothal 5 mg/kg 2,5 mg/kg Lidocaine 1 - 1,5 mg/kg Norcuron 0,1 - 0,15 mg/kg oropharyngeal airway eye ointment; paper tape.
Technique to avoid increase BP
Deeper anesthesia: Pentothal
Narcotic : Fentanyl, Sufentanil
Nitroprusside ?
Glyseril trinitrat ?
Lidocaine 1-1,5 mg/kg iv
Alpha 2 agonist dexmedetomidine
Hypotension during induction of anesthesia :
Elevation extremities, not trendelenburg
Give crystalloid, colloid
Vasopressor : if under lower limit of autoregulation
Choice of induction agent
Smooth induction more important than really drugs combination
Pentothal 3 - 4 mg/kg
Fentanyl 3 - 5 ug/kg
Vecuronium 0,1 - 0,15 mg/kg
or Rocuronium 0,6 - 0,8 mg/kg
or Atracurium 0,5 mg/kg
Maintenance of anesthesia
Less effect to cerebral autoregulation and response to CO2
Stable cardiovascular
Capable to decrease ICP and increase CPP
One of choice : pentothal, O2 + Sevoflurane, fentanyl, relaxant.
Choice of inhalation anesthetics
• Inhalation anesthetic should be evaluated effect on ICP and cerebral vasculature.
• All inhalation anesthetic has cerebral vasodilatation effect, will increase CBF, CBV and ICP.
• Must be know the effect on cerebral autoregulation, response to CO2 reactivity and CMRO2, brain protection effect.
Variable Halothane Enflurane Isoflurane Sevoflurane
BPVascular resistanceCardiac outputCardiac contractionCVPHeart rateSensitization of the heart to epinephrine
0 0
000 0?
000
0 0
Cardiovascular effect of volatile inhalation anesthetics at 1-1,5 MAC
0 = no change (<10%) = 10-20% decrease = 20-40% decrease = increase
Anoxia NMDA/AMPAProtect
ResponseImprove
NA+Improve
ATPImprove
Ca+Protect
Response
Thiopental (600 μM) Yes Yes No/Yes1 Yes Yes
Midazolam (100 μM) Yes - Yes Yes -
Propofol (20 μg/ml) No Yes Yes Yes No
Lidocaine (10 μM) Yes Yes Yes No -
Isoflurane (1,5%) No No No No -
Sevoflurane (4%) Yes Yes Yes Yes -
Etomidate
3 μg/ml No No No - -
30 μg/ml No Yes No - -
Nitrous oxide (50%) No No No No -
1Worsens ATP after 3.5 minutes of anoxia: improves ATP after 10 minutes of anoxia.
Effect of Anesthetics on Physiological Responses Effect of Anesthetics on Physiological Responses and Ion and Metabolite Levelsand Ion and Metabolite Levels
Cottrell JE. ESA, 2004,Lisbon
Maintenance of anesthesia :
First choice : Sevoflurane Second choice : Isoflurane TOF : 0 fluid : 2/3 diuresis Mannitol : 0,25 - 1 gr/kg Lasix : 0,5 - 1 mg/kg
Fluid
Stable circulation To avoid : hypovolemia, hypervolemia, hypoosmoler,
hyperglycaemia First choice NaCl 0,9%, avoid RL, no dextrose: 1-1,5
ml/kg/h or 2/3 diuresis. Dextrose : only for therapy hypoglycaemia (blood sugar <
60 mg%)
Extubation Be carefully : increase of BP, leading to hyperaemia,
edema, increase of ICP.
Lidocaine 1 - 1,5 mg/kg, alpha 2 agonist dexmedetomidine.
End of surgery increase TOF = 1
Et CO2 normal
Difficult to make decision criteria when extubation.
Postoperative periode
Avoid coughing, bucking, stretching, increase BP. Neurological evaluation immediately. Mostly extubated at OR Lidocaine 1,5 mg/kg, dexmedetomidine, vasodilator,
esmolol to avoid increase BP. Analgetics : avoid ketorolac
Immediate or delayed recovery?
• Delayed recovery cannot be recommended as a mechanism of limiting the metabolic and hemodynamic consequences from emergence after neurosurgery
Bruder N et al, Anesth Analg 1999; 89(3)
• Awake craniotomy have less PONV than GA. Manninen P et al. J.of Clin Anesth
2002;14(4)
• Fast-track NA including local anesthetic, combined GA and local anesthetic, GA with SAFE drug.
Advantages Early awakening
• Earlier neurological examination.• Earlier indications for further investigations.• Less hypertension, less catecholamine burst.• Lower cost
Disadvantages early awakening
• Increased risk of hypoxemia, hypercarbia• Difficult respiratory monitoring during transfer to the
ICU.• Hypothermia?
Condition for early emergence: systemic homeostasis•Normothermia (>36oC).•Normovolemia, normotension (70mmHg<MAP<120mmHg)
•Mild hypocapnia (PaCO2 35 mmHg)•Normoglycemia (glucose 4-8 mmol/l)•No hypoosmolality (285 ±5mOsm/kg)•Hematocrit > 25%•No coagulation disorder
Conditions for early emergence : brain homeostasis• Normal CMRO2 and CBF• Normal ICP at the end of surgery• Antiepileptic prophylaxis• Adequate head up position• Intact cranial nerves for airway protection
Check-list before attempting early extubationAdequate pre-operative state of consciousness.
Limited brain injury, no major brain laceration.
No extensive posterior fossa surgery involving cranial nerves IX-XII
No major AVM resection: risk of malignant post operative edema,
Normal body temperature and oxygenation, cardiovascular stability.
Suggested awakening sequence (1)
Prepare awakening (aim: avoid post operative respiratory depression).
•Discontinue middle or long acting opioid approx 60 min before planned emergence.
•Stop anesthetic administration during skin closure.
•Let neuromuscular block decrease to 2/4 if myorelaxation used. Antagonise myorelaxant before extubation.
•Progressive rise of PaCO2 to normoventilation
Suggested awakening sequence (2)
•Avoid unnecessary painful stimuli: remove head pins as early as possible, remove packing—performed adequate suctioning before the patient is fully awake.
•Treat BP bursts: treat hypertension due to nociception, goal MAP < 120 mmHg (dexmedetomidine, lidocaine, beta blocker).
•Transfer to PACU or ICU: O2, continuous monitoring (ECG,BP, SpO2)
Systemic and cerebral condition making delayed emergencesystemic cerebralHypothermia (<35,5oC)Hypertension ( SBP > 150 mmHg)Hypotension-hypovolemiaHematocrit < 25%Hypoxia or hypercapniaIneffective spontaneous ventilationHypoosmolality (<280 mOsm/kg)Disorder of coagulationResidual neuromuscular block
Preoperative altered consciousnessLarge tumor resection with midline shiftLong lasting surgery (>6 hours)Intraoperative brain swellingInjury to cranial nerves (IX,X,XII)Convulsions during emergence
Summary
1. Avoiding secondary brain injury will decrease morbidity and mortality.
2. Choice of anesthetics and technique of anesthesia will improve outcome.
3. knowledge neurophysiology and neuropharmacology fully help in patient management.
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