AANS2000Outline of

Neurosurgery

E. R. Flotte, 2008

 

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Miscellany

 

Critical Care/Neuromedicine

Neuroradiology

Stereotaxy

Stereotactic Radiosurgery

Awake Craniotomy & Cortical Mapping

Evoked Potentials

Neuroprosthetics

Psychosurgery

Neuroregeneration and Stem Cells

 

 

 

Critical Care/Neuromedicine

 

Anesthesia

·         Sedatives: Versed, Thiopental

·         Narcotics

·         Nitrous oxide: Avoid with pneumocephalus. Stop before dural closure to prevent tension pneumocephalus.

·         Ketamine increases CBF

·         Sodium thiopental most rapidly lowers ICP (faster than other agents or hyperventilation)

·         Dexmedetomidine (Precedex): α2-agonist, anxiolytic, analgesia, “cooperative sedation”. Used in awake craniotomy, NICU. (ON7/05)

·         Paralytics

o        Succinylcholine: 1mg/kg – 3.5 to 5cc, lasts 5-10min. do not use with spinal cord injury, hyperkalemia

o        Pavulon reversal: Neostigmine (2.5-5mg IV) + atropine (0.5mg/mg neostigmine) or Robinul (0.2mg/mg neo). Takes 20 min

·         Malignant hyperthermia: Dantrolene (2.5mg/kg, up to 10mg/kg), 100% O2, D/C anesthesia & change tubing. Occurs w/ inhalational + Sux. ↑ ETCO2. 50% previous normal anesthesia. Can test preoperatively with muscle biopsy.

·         ASA Class estimates patient physical status

Air Embolism

·         Occurs when venous pressure is lower than atmospheric pressure and the venous system is open to the atmosphere. Most likely to occur in the sitting position

·         Detection: precordial doppler (most sensitive), ¯ EtCO2 (earliest), ­ FEN2, ¯ CO, ­ PAP, ­ pulmonary vascular resistance, ventilation-perfusion mismatch.

·         Treatment: Lower the head-of-bed, cover wound with wet laps, aspirate air through central line, 100% O2.

Ventilation

·         Intubation/Extubation: 100mg lidocaine IVP, 100% O2 x 5min.

·         Tube: 20-22cm at gum line, tip 5cm above carina

·         PCWP <12, PA 15-30/4-12, CI 2.8-4.2

Arrythmias

·         Afib/Aflutter: Verapamil (5mgx2), Diltiazem (0.25mg/kg 10-20mg). (adenosine, procainimide; digoxin for flutter) If unstable cardiovert 100J.

·         Other SVT: Vagal maneuver, Adenosine (6mg-12mg-12mg), verapamil, diltiazem

·         Vtach, Vfib: Pulseless: Epi (1-3-5mg); Other: Lidocaine (1mg/kg q5m x 3), procainamide (20-30mg/min to 12mg/kg), bretylium (10mg/kg q5m x 3)

·         Asystole: Epi, atropine (0.5mg x 4)

·         Bradycardia: atropine

Myocardial infarction

·         Clopidogrel with aspirin is recommended for unstable angina or minor myocardial infarction; ticlopidine is not recommended

Antihypertensives

·         Nipride: onset seconds, Follow thiocyanate levels if used >24hrs. 0.3-10mg/kg/min. Avoid in pregnancy

·         Nitroglycerin: 10-20 mg/min, 0.4mg SL q5m x 3

·         Both raise ICP.

·         Hydralazine: onset 3-5min, duration 2-4hrs. OK in pregnancy. SE: tachycardia. IM 10mg, IV 20-40mg prn.

·         Labetalol: onset 5m, duration 3-3hrs; 20-40-60-80mg IV, 200mg po bid

·         Esmolol.

·         Vasotec: 1.25-5mg q6hrs prn

Shock

·         Dopamine: 2-20 mg/kg/min, b>ab.

·         Dobutamine: 2.5-10mg/kg/min, b only (inotrope, BP unchanged). Use for cardiac failure if normotensive.

·         Palpable pulses: radial 80, femoral 70, carotid 60

Steroids

·         Cause pancreatitis

·         Addisonian crisis: hydrocortisone (Solucortef) 100mg IVP then 50mg q6h (not Solumedrol)

Anaphylaxis

·         Treatment: Epinephrine 1:1000 5ml SQ, Benadryl 50mg IM, Decadron 10mg IV

·         Urticaria: Benadryl 50mg PO/IM + Cimetadine 300mg PO/IV

·         Vasovagal reaction: hypotension, bradycardia. Tx: Atropine 0.75mg IV, q 15min to 3mg

DVT

·         Incidence in neurosurgical patients: 15-20%

·         May be increased in craniotomies due to release of brain thromboplastin

·         Calf vein thrombosis has <1% risk of PE, however they may progress to DVT

·         Prophylaxis: Heparin 5000 U SQ BID, Lovenox 30mg SQ BID. TEDs/SCDs (do not use if DVT is present)

o        ACCP guidelines: fondaparinux is a alternative to low-molecular-weight heparin (LMWH), because it is equally safe and effective but has a longer half-life, a more predictable response, and fewer adverse effects

o        Moderate-risk surgical patients: Heparin 5000mg SQ BID or LMWH (less than 3,400 U once daily)

o        High-risk surgery patients: Heparin 5,000 U SQ TID or LMWH more than 3,400 U daily

o        Aspirin is not recommended

·         Diagnosis:

o        Doppler ultrasound: Standard

o        Clinical diagnosis (calf tenderness, warmth) is unreliable.

o        The fibrinogen uptake test and impedance plethysmography have low accuracy and are not recommended

o        Contrast venography has high sensitivity but limited availability and questionable use for small distal thrombi and high patient discomfort. Use is limited to research

·         Treatment: Bedrest x 10days, then careful ambulation. 3-6 months full anticoagulation then low-dose coumadin (INR 1.5-2).

o        Three randomized trials of anticoagulants vs no anticoagulants in DVT showed no benefit with heparin and vitamin K antagonists (combined all-cause mortality: anticoagulants = 6/66, un-anticoagulated controls = 1/60, P = .07). No placebo-controlled trials of low-molecular-weight heparins or thrombolytic drugs have been done; therefore, their efficacy in VTE depends entirely on randomized comparisons with unfractionated heparin. They have not been proven safer or more efficacious than unfractionated heparin. Thrombolysis causes more major and fatal bleeds than heparin and is no more effective in preventing PE (CundiffDK 9/04).

Pulmonary Embolism

·         Diagnosis:

o        V/Q scan:

§         Normal scan rules out PE.

§         High probability (88% true positive) then treat.

§         Low or moderate probability then obtain leg dopplers and if positive then angiogram to confirm.

o        Spiral CT

o        Angiogram

·         Treatment: anticoagulation or IVC (Greenfield) filter. Massive PE causing hemodynamic compromise should be treated with anticoagulation regardless of intracranial risk.

Fat embolism

·         Occurs 12-48hrs post-injury

·         Symptoms: dyspnea, petechiae over thorax, tachycardia, tachypnea.

·         Labs: ­ serum lipase in 50%. Look for fat in blood, urine. No specific test. 

·         Cerebral embolism (causing confusion, somnolence, seizures) does not occur without lung symtoms unless a PFO or ASD exists.

·         Treatment: O2, PEEP. Steroids controversial.

Anticoagulants

·         Preoperative management

o        Mechanical Heart Valve: stop coumadin 2d preop & admit on heparin.

o        A-fib: Stop coumadin 5d preop, can restart 5d postop

Antibiotics

·         Aminoglycosides/Gentamycin: Poor CSF penetration. SE: nephrotoxic (ATN), ototoxic, vestibulitis, worsens myasthenic crises,. Coverage: Gram (-) (no strep).

·         Sinus entry: Gentamycin, Clindamycin

·         A meta-analysis of eight randomized clinical trials (RCTs) showed that prophylactic antibiotics reduce rates of postoperative infection by approximately 75% after craniotomy (Barker FG N1994)

Electrolytes

·         AG = Na – (Cl + HCO3)

·         Osm = 2(Na+K) + BUN/2.8 + Glu/18

·         Hyponatremia: 1.0-1.5 meq/L/hr, 25meq/L/d, 3% Na 25-50cc/hr + Lasix

·         SIADH

o        Diagnosis: Na<134, Osm<280, UNa >50.

o        Treatment: Fluid restriction <1L/d. 3% NaCl. Chronic: demeclocycline (300mg po q8°) or lithium

o        Versus cerebral salt wasting: ↓↓ serum Na, ↓ or wnl BUN/CR, ↑ plasma volume, ↑ CVP/PCWP, no dehydration signs

·         Diabetes Insipidus (DI)

o        Treatment: 1/2NS, DDAVP/desmopressin (0.1-0.2 μg IVq8°). Chronic: Intanasal DDAVP (10-40μg BID)

·         Hyperkalemia: 10% CaGluconate 5-10cc over 2m; 1 amp HCO3; 5-10U regular insulin + 1 amp D50; Kayexalate

·         Heparin: Reportedly no higher risk in patients with brain tumors

·         Coumadin: always pre-heparinize

Hematology

·         Estimate of pediatric blood volume: 90-100ml/kg for premature infant, 80mg/kg for term infant, 75ml/kg for 1-12mos, 70ml/kg for >1 year

·         Platelets: 1 units raises platelet counts by 5-10K. Do not use with autoimmune destruction (eg ITP).

·         Fresh Frozen Plasma

·         Vitamin K:  10mg IM. PT reversal requires 6-12 hrs. (Do not give IV)

·         Prothrombin complex concentrate reverses coumadin 5x more quickly than FFP

·         Transfusion Reactions

  • Hemolytic: Due to ABO incompatibility. Symptoms: chest pain, shock. Stop transfusion, mannitol, IV fluids.
  • Allergic: Due to plasma proteins. Causes hives. Treatment: Benadryl.
  • Febrile: Treatment: Tylenol. Send blood for analysis to rule out hemolysis

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