Anaesthesia for supratentorial tumours

Dr. S. Parthasarathy MD., DA., DNB, MD (Acu),

Dip. Diab.DCA, Dip. Software statistics,Phd (physio)Mahatma Gandhi Medical college and research institute puducherry ,

India

What is it ??

Supratentorial means

• Cerebral hemispheres and diencephalon

Thalamus and hypothalamus

Incidence

35, 000 new cases /year in USA Majority are supratentorial – more in adults

Glioma Mengioma Astrocytoma Pitutatry adenoma Brain abscess Metastasis

• Glial tumors disrupt the blood-brain barrier• More edema • More bleeding • hypertension

• Meningiomas, • 15% of primary brain tumors,• slow growing and very vascular and can be

difficult to dissect. • They may require multiple attempts at resection

and this may be preceeded by embolisation of the tumor.

Secondaries

• secondary neoplasms arising predominantly from the lung (50%) and breast (10%).

• The incidence of secondary tumors rises with increasing age.

• Excision of solitary lesions is justified in patients in whom the underlying disease is well controlled.

brain abscesses

• local spread from sinuses or ear infections • especially common in immuno compromised• and diabetic patients, • those with right-to-left cardiac shunts, • intravenous drug abusers

Three preoperative questions

• (a) Where is the mass lesion?

• (b) Is ICP already elevated?

• (c) What is the patient’s current neurologic

status?

Question number 1 -Where is the mass lesion?

• surgical position and position of monitors

• the potential for blood loss,

• Predict Post op deficit ( if occurs ) where ?

• occasionally reveal a risk of air embolism. Risk of VAE

is quite low for most supratentorial tumors.

• However, lesions (usually convexity meningiomas)

that encroach on the sagittal sinus may convey a

substantial risk of VAE

Question no. 2 _ ICP • Headache caused by traction or distortion of cerebral

blood vessels and dura mater. exacerbated by recumbency, movement, and straining, Classically, it is worse on waking up.

• Nausea and vomiting• Papilledema• Cushing s ulcers • Hypertension , bradycardia, and widening pulse

pressure – ( cushing triad) • Neuro deficit • Respiratory changes

ICP ???

• Not all mass lesions cause increase ICP

• Not all asymptomatic patients have normal ICP

Question 3

Mental status, level of consciousness GCS Pupil size, reaction Speech defect Neuro deficit

Any concurrent diseases

Preoperative work up !! Hydration: duration of bed rest, fluid intake, diuretics,

syndrome of inappropriate secretion of antidiuretic

hormone

Medication: steroids, antiepileptic drugs

Associated illnesses, trauma

Patients with pan hypopituitarism will need hormone

replacement, including cortisol, levothyroxine, and possibly

DDAVP. These medications should be continued in the

perioperative period.

Investigations

• Routine investigations – electrolytes• Coagulation • Platelets • Drugs and their side effects • Neuro imaging • Blood grouping

Hydration • Calculate • Maintenance + Fluid loss due to urine output • 500 ml negative • No fasting calculations for adults • Glucose ( slow) + nonglucose (fast to counter

blood loss) – alternate • Add 5% dextrose to NS , RL ? is just ok • Keep hyper osmolar

Mannitol • 0.25 gm – 1 gm/ kg IV boluses • Reduce edema• Better access • Reduce ICP • But dehydration , Urine output, serum

osmolality and serum electrolytes must be monitored

• Use it in all Vs selected cases – controversial • Rebound edema due to chloride influx • Blocked by frusemide

Premedication

• Preferably no sedatives • Inj Dexamethasone 10 mg tds 48 hours prior • Antiepileptic medication to continue • Formulate a plan • What position, surgery, blood loss, monitors

where, IV access where ?? ( micro planning) • patients with mass lesions be transported with

the head of the bed elevated 15–30

Routine monitoring during brain tumour surgery should include

• ECG,• invasive and noninvasive blood pressure, • pulse oximetry, capnography,• nasopharyngeal temperature and • urine output.• ICP monitoring.-- Currently rare for elective

neurosurgery due to improvements in peri operative ICP control

• SSEP, EEG , transcranial doppler in specific instances

Monitoring

• Glucose • Coagulation • Blood gases • Chemistry • CVP monitoring ( diabetes insipidus producing

craniopharyngomas, VAE ) • PAC – medical indications

Unilateral frontotemporal (pterional) approach

Bifrontal approach

Inter hemispheric approach

• Trans sphenoidal

• Extra cranial

Goals of GA • Smooth induction

• Hemodynamic stability

(hypotension can lead to ischemia in areas of impaired

autoregulation; hypertension increases the risk for hemorrhage

and vasogenic edema)

• Relaxed brain (for optimal surgical access and to reduce the risk

for retractor damage)

• Rapid and smooth emergence from anesthesia to allow early

neurologic assessment

• Induced hypo – no longer favourable

• NTG , SNP not preferred to decrease BP – increase CBF

• Beta blockers and ACE inhibitors preferred

Anaesthetic management

Induction • 10 degree head up

• Narcotics,

• Propofol (Hypo??)or thio in liberal doses

• Nondepolarizers but Scoline ok in difficult airways because

hypercapnia and hypoxemia worse than I ICP by scoline

• IV lignocaine or esmolol for intubation

• fix the tube, eye pad, some more monitors

• Positions

Numerous positions

Numerous positions

Maintain ??

• Air , oxygen isoflurane , sevo

• Or

• fentanyl + • propofol infusion 50 – 150 mic. gm /kg/min.• Mild hypocapnia

Intra op events

• Neurosurgical procedures are often associated with “occult” blood loss (underneath surgical drapes or on the floor).

• Nasogastric tube • Axilla auscultation after flexion of tube • Prone for DVT but ?? Chemical prophylaxis ?? • Nerve stimulator • Later part of surgery ? – painful - ? Opioids

Intra operative techniques

• Fix the tube very well – • LA and fentanyl shot before pin. • Flex or turn the head carefully • ---- tube kink • ----- ICP rise• Osmotic diuretics (mannitol, hypertonic saline); steroids

for tumor • Loop diuretics (furosemide) • No PEEP • Maintain BP

ICP reduction

Intra op key points • Increased intracranial pressure can result from

increased abdominal pressure,• venous congestion, and positioning of the head

below the level of the heart.• Venous congestion can result from venous

outflow obstruction caused by hyper rotation or hyperflexion of the neck.

• Increased PEEP and airway compromise can result from kinking of the endotracheal tube caused by neck flexion.

Brain suddenly swells • Is this a major ventilatory disaster?

• Is the brain swollen because of a disconnect, severe hypoxia,

hypercapnia?

• Is the chest moving appropriately?

• Does the patient have a reasonable expired CO2 waveform ?

• What is ETCO2 ? What is the SpO2?

• Is the swelling related to impaired cerebral venous drainage?

• Anaesthesia , analgesia ??

Brain swelling continues • Mannitol • Frusemide • Hypertonic saline : Various conc and doses

have been used 3%, 7.5%, 23.4% : all show ↓ICP and ↑CPP. No deleterious diuresis and undesired hypovolemia.

• Cannulate ventricles • NO nitrous • No agent • Thio 250 mg

Delayed awakening

Recovery

• Simple case • Small lesion • Preop and intra op period uneventful • No brain swelling

• Extubate on table – continue monitoring

Delay awakening

• Hypoxemia – less • Hypercapnia – less • Hemodynamic stability √

• But

• Less neurologic monitoring •More hypertension, catecholamine release • bleeding

“frontal lobey.”

• Bi frontal approach • Brain retraction

• immediate postoperative period

• Delayed awakening or disinhibition or both

Other post op issues

• Blood loss • Narcotics ( sedation Vs pain relief ) • Paracetomol • No cough, straining • Steroids • Antiepileptics • Normoglycemia • Other systemic illness

Summary

• Supratentorial means ?? • Preop three questions • Monitoring • Premedication• Anaesthetic techniques • Early Vs delayed awakening • Postop ventilation when ??

Thank you all