Neurosurgical Anesthesia Flashcards
What is the mean CSF volume?
150 mL
Where does the CSF pool?
- Cisterns
- Area where arachnoid membrane and pia mater are further apart
The region where CSF is produced
- Choroid Plexus
- Highly organize tissue that lines all the ventricles
What cells excrete CSF?
Ependymal Cells
Mostly dependent on transport of sodium ions
What structures absorb CSF?
Arachnoid Villi
Have one-way valves to prevent backflow
Describe the Pathway of CSF
- Formation of CSF in choroid plexus of lateral ventricles, excreted by ependymal cells.
- CSF will travel into the third ventricle through the Foramen of Monro (Intraventricular Foramen)
- CSF will travel along the Aqueduct of Sylvius into the fourth ventricle
- CSF will travel through foramen of Luschka and Foramen Magendie
- CSF will enter the Cisterna Magna (Cerebellomedullary Cistern)
- CSF will go through the subarachnoid space surrounding the cerebrum and be absorbed into the arachnoid villi
Where does the absorption of the CSF into the bloodstream take place?
In the Superior Sagittal Sinus through the structures called Arachnoid Villi.
What is the Monro-Kellie Doctrine
- The total volume of the brain, cerebrospinal fluid (CSF), and blood in the cranium is constant.
- If one of these components increases in volume, the other two must decrease by the same amount
A term that can be used to refer to CSF build up/obstruction
Idiopathic Intracranial HTN (Pseudotumor Cerebri)
Idiopathic Intracranial HTN (Pseudotumor Cerebri) is most common in which patient population?
Common in obese women of reproductive age
The range for normal ICP
- 7-15 mmHg
- 10 mmHg when supine
What is considered pathological/ critical ICP?
- > 20 mmHg
- Brain herniation is possible when ICP is elevated
What is the gold standard for measuring ICP?
Intraventricular Monitor
What is normal Cranial Perfusion Pressure (CPP)?
60-80 mmHg
What is the critical ischemia CPP threshold?
30-40 mmHg
When will the autoregulation of CPP be disrupted?
Pathological states
Management of CPP during intracranial pathology
ICP management
Sx of Increase ICP
- Headache
- N/V
- Blurred vision
- Somnolence
- Papilledema
- Midline shift on CT
- Hydrocephaly
- Edema
- Cushing’s Triad
Management of CPP during Hemodynamic instability/shock
MAP management
Causes of increase in ICP
- Increase Cerebral Blood Flow
- Tumor
- Intracranial hematoma
- Blood in CSF (SAH)
- Infection (meningitis/ encephalitis)
- Aquaductal stenosis
- Idiopathic
Components of Cushing’s Triad
- Bradycardia
- Widen Pulse Pressure
- Irregular Respirations
What type of position will decrease ICP?
- Elevate head of bed
- Improves venous drainage
PaCO2 of ________ mmHg quickly reduces ICP
30-35 mmHg
Achieved through hyperventilation, effects can last between 6-12 hours
What are ways to physically drain CSF?
- Ventriculostomy
- Lumbar drain
- VP shunt
Drugs used to decrease ICP
- Hyperosmotic Drug (Mannitol) 0.5-1 g/kg
- Anticonvulsants (seizures increase CMRO2, give Keppra)
- Loop Diuretic
- Corticosteroids (best given 48 hours before surgery)
- Anesthetics
What can be the negative effect of giving corticosteroids during a craniotomy?
- Corticosteroids may increase blood glucose
- Hyperglycemia can decrease elasticity of blood vessels → cerebral ischemia
Mild hyperventilation has a parallel reduction in __________
Cerebral Blood Volume
What are some concerns with hyperventilation to decrease ICP?
- Potential ischemia in some areas
- CBF and ICP lowering effect won’t be sustained long term (6-12 hours)
Management of Arterial BP for Neurosurgery
- Maintain CPP between normal-high normal
- Suggest MAP within 10-20% of average awake BP
Mannitol is usually given in incremental doses (12.5 gm) to limit ____________.
Rapid Hyperosmolarity
Neurons and glia rapidly swell d/t increase osmolarity (rebound effect). What drug can be given to inhibit the chloride channel and slow down the rebound effect?
Furosemide
What is the MOA of Keppra?
- Binds to a synaptic vesicle protein 2A
- SV2A mediates calcium-dependent neurotransmitter release
- Binding of Keppra to SV2A inhibits rate of vesicle release
Dose: 500 mg over 15 minutes
Surgical Positioning & Associated Complications with neuro surgery
- High risk of nerve damage and embolic complications!
- Sequential compression stockings
- Promote venous drainage; avoid contralateral jugular vein compression
- Prevent brachial plexus injury
- Avoid ischemic optic neuropathy (ION) in prone position
- Low BP, low Hct, long surgery, large volume admin
- Avoid vena cava compression
- Airway: be aware that tongue will swell in prone position; secure tube WELL
- Venous air embolism risk (when open head is above heart)
What is the IVF of choice for Neurosurgery?
Normal Saline (308 mOsm/L)
Effects of Hypothermia on the brain
- Reduces electrophysical activity in the brain
- May provide brain protection
- Not advocated in neurosurgery (increase dysrhythmias and coagulopathy)
Glucose management during Neurosurgery
- Increased plasma glucose aggravates cerebral ischemia in TBI
- Low glucose can cause seizures/ brain dysfunction
- Recommendations: 150-200 mg/dL
What is a Subdural Bolt?
A pressure transducer placed in subdural space or brain parenchyma
What is a Ventriculostomy?
- Catheter placed into the ventricle which allows for monitoring and CSF drainage
- Best way to measure ICP and control CSF drainage
What is a Lumbar Subarachnoid Catheter?
Catheter that allows CSF drainage by gravity but may be inaccurate for central CSF pressure if blockage occurs
What does a Cerebral Oximetry measure?
- Measures regional blood hemoglobin oxygenation saturation (rScO2)
- Measures balance between flow and metabolism
How does a Cerebral Oximetry work?
- Uses near-infrared spectroscopy; similar to pulse ox
- Sensor emits 2 alternating lights which pass through skin, skull, dura, and CSF to blood of cerebral cortex
Patient population that Cerebral Oximetry may be useful
- Pt at risk of stroke
- Cardiac surgery
- Vascular surgery
- Procedure that put a single hemisphere at risk
Normal Cerebral Oximetry range
70% +/- 20-30%
What is used to measure spontaneous brain activity?
Electroencephalogram (EEG)
What measures signals that result from specific stimuli?
Evoked Potentials
What is Somatosensory Evoked Potential?
- Signal generated in response to applied sensory input
- Cutaneous electrical stimulation of a peripheral sensory nerve
- Signals are received in the cerebral sensory cortex and requires an intact pathway (dorsal column of spinal cord)
What is Motor Evoked Potential (MEP)?
- Provides info about descending motor pathway
- Cortex to the neuromuscular junction
- Stimulus applied transcranial over motor cortex
Anesthesia Considerations for MEP’s
- Very sensitive to anesthetics (more so than SSEP)
- May cause patient movement/monitor derangement
- May cause patient injury (bite tongue!)
- Soft bite blocks required & documented
- Latency unreliable; 50% decrease in amplitude = significant
- No NMBD
If a patient is running SSEP/MEP what should the MAC be on the volatile anesthetic?
- 1/2 Mac of Gas with a propofol/narcotic drip
- Or just go full TIVA
- SSEP/MEP are unaffected by opioids
Classification of Cerebrovascular Accident/Stroke
- 20% are hemorrhagic (SAH, ICH)
- 80% are embolic/ ischemic
Hemorrhagic strokes are how many more times likely to cause death than embolic stories?
4x
How are strokes diagnosed?
- Clinical symptoms
- CT Scan
Common stroke symptoms
- “Worst headache of my life”/Thunderclap headache (SAH)
- Visual disturbances
- Nuchal rigidity
- Change in LOC
- Can also see ST-segment depression/T wave inversion related to catecholamine release
How does an embolic stroke occur?
- Usually caused by embolism that develops elsewhere and travels to brain
- Blocks blood flow
- Ischemia results
What is the most common comorbidity for embolic stroke
Cardiovascular Disease (Afib, Cardiomyopathy, Recent MI, Cardiac Sx, Valvular disease)
How does an embolic stroke occur from Cardiomyopathy?
Dilated LV (floppy heart) is typically capable making an emboli → Blocking large cerebral vessels or carotid arteries
How does an undiagnosed PFO (Patent Foramen Ovale) lead to an embolic stroke?
Embolism formed in the vein can pass from venous to the arterial circulation
What is the goal when treating an embolic stroke?
Restore blood flow as quickly as possible
Treatment for an embolic stroke
- tPA: Tissue Plasminogen Activator (Alteplase)
- Endovascular Thrombectomy (IR)
- TCAR (Trans-Carotid Artery Revascularization)
- Carotid endarterectomy (if carotid blockage or high risk for carotid blockage)
How does tPA work?
What is the window of time to use tPA for an embolic stroke?
- Catalyzes conversion of plasminogen to plasmin
- Breaks down blood clots
- Only effective if administered within ~2 hours of symptoms
What is a Subarachnoid Hemorrhage (SAH)
- Accumulation of blood between arachnoid space and pia mater
- Requires immediate attention
Symptoms of a SAH
- Characteristic “thunderclap headache”
- N/V
- Vision disturbances
- Cranial nerve deficits can occur
- Meningitis-like symptoms if blood spreads down and irritates spinal nerves
- Coma
What is an Intracerebral Hemorrhage (ICH)
Bleeding in the parenchyma
What are the common causes of an ICH?
- HTN
- Arteriovenous malformation
- Aneurysm rupture/leak
- Trauma
- Coagulopathy
Treatment for Hemorrhagic Stroke
- Find and stop source of bleeding
- Craniotomy (clipping or removal of AVM)
- IR Coiling
- Burr hole (usually for SDH)
Craniotomy: Aneurysm Clipping Procedure
- Open skull (bone flap) & dura
- Retract brain tissue
- Isolate aneurysm from circulation
- Clip is placed across the base/neck of the aneurysm
- Clips are permanent
- During surgery, temporary clips may be placed to control bleeding
Endovascular: Aneurysm Coiling IR Procedure
- Vascular access obtained at groin site
- Small catheter inserted into the aneurysm
- Aneurysm filled with soft wire coils to prevent blood from flowing into it
- May be balloon-assisted, stent-assisted, or use of flow diverters
Considerations to take into account with Clipping vs Coliling
- Clipping is more invasive, but lower re-treatment rate.
- Not all patients can tolerate clipping (elderly, unstable)
- Not all aneurysms can be coiled (size, shape, patient)
- Coiling requires blood thinning therapy afterward
- Coiling is relatively new (Fewer studies on outcomes/rebleeds)
Anesthesia for Stroke: Induction Considerations
- Must have tight control of blood pressure/MAP
- Pre-induction arterial line
- Gentle/slow induction (Esmolol, Intubate DEEP)
- Rebleeding at induction is often fatal
Anesthesia for Stroke: Maintenance Considerations
- Approx 7% rupture rate intra-op toward late stages of dissection
- Maintain appropriate anesthetic depth
- NO MOVING
- Burst suppression if required
- Maintain CPP
- Mild hyperventilation
- Communication with surgeon
- May need emergent induced hypotension: have prepped and ready… (ex: adenosine)
Anesthesia for Stroke: Emergence Considerations
- Free of coughing, straining, and arterial hypertension
- Consider using lidocaine, esmolol, labetalol
- Good amounts of narcotic/timing of narcotic gtt cessation
- Time emergence with dressing, not final suture
- Neuro check
What is thought to be the cause of cerebral vasospasm?
Breakdown products of Hbg and NO
How is vasospasm treated?
- Treat with calcium channel blockers
- Nimodipine/verapamil/nicardipine
How is Cerebral Vasospasm prevented?
- Triple H Therapy
- Hypertension (20-30mmHg above baseline) Use Phenylephrine or dopamine gtt
- Hypervolemia (really euvolemia)
- Hemodilution (Hct low ~30)
What medication can improve endothelial function and decrease oxidative stress and inflammation?
Statins
What is the function of magnesium?
Inhibits calcium-channel smooth muscle contraction and mitigate cerebral vasospasm
MOA of Cilostazol
- Phosphodiasterase inhibitor
- Antiplatelet
- Vasodilator
What is Stereotactic Neurosurgery?
- Use of MRI/CT imaging and a highly specialized 3-D coordinate system to target precise areas deep within the brain
- Typically used to guide biopsy of tumor, DBS, Focal seizure/lesion ablation
Deep Brain Stimulators are typically use to treat what type of movement disorder?
- Parkinson’s
- Essential Tremor
- Dystonia
- Tourette
What region of the brain does the DBS usually target?
Subthalamic Region
Describe the stage 1 procedure of a DBS
1st Stage – Placement of electrodes under lighter sedation with stereotactic techniques, will wake patient up for intra-operative testing
Describe the stage 2 procedure of a DBS
2nd Stage – GETA, ~1 week later, tunneling of leads from brain to generator (implanted under skin on chest)
Anesthesia Consideration for Stage 1 DBS
- A rigid head frame is applied w/ local anesthesia
- Pt to MRI
- Patient returned to OR; prepped, draped
- MAC anesthesia provided
- Burr holes established for placement of electrodes in subthalamic nucleus
- Target tissue is stimulated with patient feedback
- Leads are sutured in place and burr holes closed
- Avoid BZD (interference)
- Avoid Remi (may suppress Parkinsonian tremor)
- Use propofol/ precedex
- Have precordial doppler (risk of VAE)
Anesthesia Consideration for Stage 2 DBS
- Electrodes are accessed and connected to 1 or 2 generators placed below the clavicle
- General anesthesia (Intubated)
- Balanced anesthesia
- Extubated on table
What drugs may be given during a focal seizure ablation to induce seizure activity?
- Ketamine
- Methohexital
- Etomidate
- Alfentanil
- Meperidine
What drug needs to be avoided for a Stereotactic Ablation?
BZD (can suppress seizure activity)
Anesthesia: Stereotactic Neurosurgery Considerations
- Ensure absence of coagulopathy
- Frame or other equipment may be in your way airway
- No/limited neck extension
- Glidescope/back-up options
- SBP <150mmHg (decreased risk for bleeding)
- Cardene gtt
- If on levodopa, morning dose will be held
- Muscle rigidity; potentially difficult IV start
- Patient anxiety
- Education, coaching, appropriate choice of sedation (nothing long-acting)
Anesthesia Consideration for Awake Craniotomy
- Patient is awake/alert for most of surgery
- Scalp block placed for incision
- Sedation/pain medication as appropriate
- The brain itself does not feel pain!
- Surgery on “sensitive areas” that control vision, speech, movement
- Surgeon will want patient to talk/perform tasks to guide surgery & ensure no damage
What kind of hematoma is largely associated with skull fractures?
Epidural Hematoma
What vessel is torn in an Epidural Hematoma?
- Tear in the middle meningeal artery.
- Associated with LOC, life-threathening.
What vessel is torn in a Subdural Hematoma?
- Tear of the saggital vein
- Slow bleed, can be acute or chronic
- Sometimes found incidentally in elderly
What is a surgical treatment for a SDH?
Burr Hole Surgery
What is a Burr Hole?
- Small holes surgically drilled into skull to drain blood and relieve pressure on brain
- Emergent procedure. Frequently an “add on” case/weekends/nights
Common for subdural bleeds
Anesthesia Considerations for Burr Hole Surgery.
- Not as invasive as a craniotomy
- Still want an a-line and 2 IV’s
- GETA
- Can be a “plain vanilla” case
- No evokes/no need for anything “fancy” with your anesthetic choice
- Get in, drain blood, get out
Anesthesia Considerations for Neuro Trauma
- Intubate if GCS 8 or less
- Full stomach
- Cervical spine stability
- Uncertain airway
- Uncertain volume status
- Increased ICP
- Combative patient
- Hypoxemic
- Minimal 18G, 2 PIV
- RSI
- A-line
- Keep paralyzed during surgery
- Measures to decrease ICP
- Extubate or keep intubated, ICU
What is hydrocephalus?
- Abnormal build of CSF in the ventricles
- Ventricles wide → Pressure on Brain structures
What can cause Hydrocephalus with a Normal ICP
Impaired CSF absorption from a previous insult
- Trauma
- SAH
- Tumor
- Infection
- Idiopathic
What triad is usually presented in hydrocephalus with a normal ICP?
- Dementia
- Gait changes
- Urinary incontinence
Usually developed over weeks to months
How is Hydrocephalus with Normal ICP diagnosed?
- LP: normal or low CSF pressure
- CT/MRI: enlarged ventricles
What can cause Hydrocephalus with an elevated ICP?
- Imbalance between production and absorption
- Often congenital
- Structural abnormalities (Chiari malformation, Tumors)
Common symptoms of hydrocephalus with elevated ICP:
- N/V
- Altered LOC
- Papilledema (swelling eyes)
- Bradycardia
- Hypertension
- Breathing pattern change
How is Hydrocephalus with Elevated ICP diagnosed?
- LP: high pressure
- CT: enlarged ventricles, more pronounced
What is Chiari Malformation?
- Brain tissue bulging into the spinal canal
- The cerebellum pretty much pushes through the opening in the skull.
What is communicating hydrocephalus?
- CSF can exit the ventricles but can’t be effectively absorbed by the arachnoid villi.
- Normal pressure hydrocephalus is a form of communicating hydrocephalus
Can be caused from meningitis or other infections
What is non-communicating (obstructive) hydrocephalus?
- CSF can’t escape from the ventricular system
- Some tumors can cause obstruction
What is the most common cause of non-communicating (obstructive) hydrocephalus?
- Aqueductal stenosis
- Narrowing of the Aqueduct of Sylvius between the 3rd and 4th ventricles
What is a ventriculoperitoneal shunt (VP Shunt)?
- Surgical method to treat hydrocephalus
- Tube that connects brain ventricles to abdomen
- Drain CSF
What is the most common complication of a VP shunt?
- Blockage
- Infection
- May do “revision” surgery
Anesthesia Considerations for a VP Shunt
- Usually supine with head turned to the side
- Mild hyperventilation/control of CO2 & other techniques to decrease ICP
- A general surgeon will obtain peritoneal access (usually laparoscopic)
- Tunneling of catheter = very stimulating!
- Need profound skeletal muscle relaxation
- Need OG Tube to decompress stomach to avoid gastrostomy!
What is a primary tumor?
Tumor that arises from the brain and its coverings
Describe a meningioma
- Usually benign brain tumor; arising from coverings of brain
- Commonly near the sagittal sinus, VAE more likely during repair
What are the different types of primary tumors?
- Meningioma
- Gliomas
- Glioblastoma
Describe a glioma
- Non-aggressive primary brain tumor.
- Surgical resection successful
- Astrocytes, ependymal cells, oligodendrocytes are affected
Describe a glioblastoma
- Most aggressive and most common brain tumor
- Micro invasion, grows quickly
- Life expectancy weeks/months
Intracranial Tumors Symptoms and Treatment
- Commonly present with headache, seizures, or new neurologic deficits
- Treatment may consist of surgical resection, chemotherapy, and/or radiation
What are Pituitary Tumors
- Tumor that arise from cells of the anterior pituitary gland
- Almost always benign
- May occur with tumors of parathyroid and pancreatic islet cells (Multiple Endocrine Neoplasia-Type I)
- Surgically curative
What are the two types of Pituitary Tumors?
- Microadenomas (functional): hormone-secreting; symptoms related to hormone
- Macroadenomas (non-functional): non-hormone secreting; symptoms relate to mass itself
What hormones will be associated with functional pituitary tumors?
- Prolactin (lactation, infertility, breast tissue development)
- ACTH (adrenal hyperplasia)
- Growth Hormone (acromegaly)
What is the method of choice for resection of pituitary tumors?
Transsphenoidal Hypophysectomy
Describe a Transsphenoidal Hypophysectomy procedure
- Performed nasally to avoid complications associated with craniotomies
- Otolaryngologist reaches sphenoid sinus.
- Neurosurgeon excises tumor
CSF leaks controlled with fat or muscle graft - Otolaryngologist performs a sella floor reconstructed with bone; sphenoid sinus closed.
Transsphenoidal Hypophysectomy Anesthesia Considerations
- Acromegaly: large tongue, long neck, redundant airway tissue
- Consider fiberoptic intubation if difficult airway
- Oral Rae tube, Secure tube well!
- Standard induction and maintenance drugs
- CV issues, Arterial line
- Deliberate oropharyngeal/gastric suction prior to extubation
- No nasal cannula or nasal airway postop
- Complications: VAE, carotid injury, optic nerve injury
Complications of Transsphenoidal Hypophysectomy
- VAE
- Carotid injury
- Optic nerve injury
What is an Acoustic Neuroma?
A noncancerous tumor that grows on the vestibulocochlear nerve (CN VIII), which connects the inner ear to the brain.
When can a patient have bilateral acoustic neuroma
If they have neurofibromatosis
Symptoms involved with acoustic neuromas
- Hearing loss
- Tinnitus
- Disequilibrium
Treatment of Acoustic Neuromas
- Surgical resection common with auditory evoked potentials
- Prognosis is very good; recurrence is common
Where do most metastatic brain tumors originate from?
- Lungs
- Breast
- Most likely diagnosed when more than one lesion is present
Why will metastatic brain tumor resection have a high likelihood of bleeding during a resection?
- Due to abnormal angiogenesis around the tumor
- Have blood available
Anesthesia Considerations for Craniotomy: Pre-op
- Evaluate for increase ICP
- Caution with preoperative sedatives (Hypoventilation, ↑ PaCO2 → cerebral vasodilation)
- Assess potential for blood loss
- Preoperative steroids for 24-48 hours
Anesthesia Considerations for Craniotomy: Induction
- 2 Large Bore IV’s
- For sitting posterior fossa crani, the central line should have a right heart catheter!
- Arterial line pre-induction (usually)
- Need a rapid, reliable induction without increasing ICP
- Stable BP during induction
- Adequate depth before laryngoscopy
- Adequate depth for pinning (propofol or remi bolus)
- Protect eyes! Secure tube!
- Nondepolarizing muscle relaxants as indicated (Can’t use with evokes… communicate with surgeon & evokes technician)
- May be okay to induce with NDMR and let them wear off
- Place soft bite blocks with evokes
Anesthesia Considerations for Craniotomy: Maintenance
- Combination of drugs with evokes (½ MAC, Narcotic or sedation drip)
- Propofol bolus if burst suppression is required (aneurysm clipping)
- Nitrous oxide is controversial d/t potential for venous air embolism
- No spontaneous movements!!!
- Remi works well to keep people still…
- Maintain euvolemia (PRBC)
- Retraction of dura over parietal lobe area can induce the trigeminal cardiac reflex (hypotension, bradycardia) → notify surgeon
- Traction on dura can also cause brain irritation/seizures
Anesthesia Considerations for Craniotomy: Emergence
- Surgeon will likely want to see patient follow simple commands (squeeze hand, wiggle feet) before extubation
- Will likely wake up and extubate but… depends on pre-op LOC & course of surgery
- Figure out how you want to handle HOB away
- Collaborate with surgeon
How does a VAE occur?
Air enters venous circulation and travels to right ventricle and pulmonary circulation.
VAE can occur with the following: Not just neurosurgery…central venous catheter insertion/removal, CT injector, hemodialysis, penetrating chest injuries, lung biopsy, cardiovascular surgery, angioplasty, arthroscopy, laparoscopic procedures, and hysteroscopy, ENT surgeries, among many others…
What will cause the highest risk of VAE?
- High risk when the head is positioned above the heart
- Sitting Crani/beach chair
Complications when an air embolism is lodged in the pulmonary artery
- Right heart failure
- Bronchoconstriction
Complications with an air embolism is passed through to the left side of the heart.
- Cerebral embolism
- Coronary artery embolism
VAE Cardiac s/s
- A mill-wheel murmur (loud and machinery-like) Can be heart w/doppler
- HEMODYNAMIC INSTABILITY/Sudden drop in CO2
- Tachy or bradyarrhythmias
- Myocardial ischemia
VAE Pulmonary s/s
- Rales, wheezing
- Cyanosis
- Tachypnea
- Apnea
VAE CNS s/s
- Altered mental status
- Seizures
- Coma
- Transient focal neurological deficits
What device is needed to help detect a VAE in high-risk surgeries?
Precordial Doppler
Intraoperative VAE Management
- Discontinue N2O if using (you probably shouldn’t be…)
- Operative site flooded
- Aspiration of right heart
- All sitting posterior fossa procedures must have right heart catheter
- Pure oxygen administered
- Supportive treatment
Where is ADH synthesized?
Where is ADH transported after it is synthesized?
- Synthesized in supraoptic nuclei of the hypothalamus
- Transported down supra-optic hypophyseal tract to the posterior pituitary
What syndrome can occur if the posterior pituitary is damaged during a transsphenoidal tumor excision?
- Diabetes Inspidus
- Usually occurs 12-48 hours postop
How is DI diagnosed?
- Polyuria
- Rising Serum Osmolality
- Hypo-osmolar urine
Treatment for DI
- ½ normal saline
- Hourly maintenance fluid + two-thirds previous hour’s urine output
- Desmopressin if U/O > 350-400 ml/hr
