CRITICAL CARE AND NEUROANESTHESIA

I. SHOCK

A. Hypovolemic—usually a 30% decrease in blood volume before impaired organ perfusion

B. Cardiogenic—due to impaired cardiac pumping

C. Septic—due to lowered peripheral vascular resistance, usually associated with gram-negative rods

D. Neurogenic—due to decreased sympathetic output causing lowered peripheral vascular resistance, with blood pooling in veins after a spinal cord injury

II. ADRENAL INSUFFICIENCY

A. Low adrenocorticotropic hormone (ACTH)—can usually be replaced with just glucocorticoid (dexamethasone)

B. Primary adrenal insuffciency (Addison disease)—must be treated with mineral and glucocorticoids (hydrocortisone or prednisone). Patients on steroids for >2 weeks must be tapered off over 2 weeks.

C. Symptomatic adrenal insufficiency—includes fatigue, hypotension, hypoglycemia, hyponatremia, hyperkalemia, and hyperthermia

III. HYPOTHYROIDISM

A. Signs/Symptoms—usually fatigue, coarse hair, cold intolerance, constipation, and possibly neurologic impairment

IV. SYNDROME OF INAPPROPRIATE ANTIDIURETIC HORMONE (SIADH)

A. Normovolemia—serum osmolarity (Osm) <280, urine Osm > serum Osm, serum Na⁺ <135 mEq/L, and urine Na⁺ >50 mEq/L

B. Urine output—usually low (~40—60 mL/h)

C. Urine Na⁺—usually close to 50 mEq/L

D. Treatment—fluid restriction 1 L/d, NaCl 3% 30 mL intravenously (IV) every hour (q1h) × 3 and Lasix to reach 125—130 mEq/L. Avoid rapid correction more than 1 mEq/L/h to avoid central pontine myelinolysis. Consider adding demeclocycline 300 mg orally (PO) q8h or lithium 300 mg PO q8h to cause nephrogenic diabetes insipidus (DI) in refractory cases.

V. CEREBRAL SALT WASTING

A. Hypovolemia—with loss of free water and Na⁺

B. Decreased weight and central venous pressure (CVP)

C. Urine output—usually high (>100 mL/h)

D. Urine Na⁺—usually around 130 mEq/L

E. Treatment—0.9% normal saline (NS) boluses

VI. DIABETES INSIPIDUS

A. Urine output—>300 mL/h × 3, specific gravity <1.005

B. Urine Na⁺—<10 mEq/L, serum Na⁺ >145. Watch to Diffentiate from normal postoperative diuresis that maintains a normal serum Na⁺

C. Treatment—fluid replacement of ½ NS and desmopressin acetate (DDAVP) 0.1 to 0.2 μg IV q8h. Long-term care may require intranasal DDAVP 10 to 40 μg twice a day (b.i.d.)

A. Hemolytic—caused by ABO blood incompatibility

1. Signs/Symptoms—lumbar pain, disseminated intravascular coagulopathy (DIC), and shock

2. Treatment—stop the transfusion and diurese with mannitol and fluids

B. Allergic—caused by antibodies to plasma proteins

1. Signs/Symptoms—hives

2. Treatment—Benadryl. The transfusion usually does not need to be stopped.

C. Febrile—caused by antibodies to donor white blood cells (WBCs)

1. Signs / Symptoms—fever

2. Treatment—Tylenol. The transfusion usually does not need to be stopped. Send off blood for analysis to rule out hemolysis.

VIII. ANAPHYLAXIS

A. Treatment—epinephrine 1:1000 0.5 mL SQ, Benadryl 50 mg intramuscularly (IM), and Decadron 10 mg IV

IX. DEEP VEIN THROMBOSIS

A. Prevent with TED (thromboembolic deterrent) hose, sequential compression devices, and heparin subcutaneously (SQ) 5000 mg b.i.d. or Lovenox 30 mg SQ b.i.d.

B. Rule out pulmonary embolus with ventilation–perfusion (V/Q) scan, spiral computed tomography (CT), or pulmonary angiogram

C. Treatment—anticoagulation or Greenfield inferior vena cava filter

X. COUMADIN

A. Weaning off for surgery

2. Patients with atrial fibrillation—stop the Coumadin 5 days before surgery. It is usually safe to resume heparin 5 days after a craniotomy.

XI. PREOP ANALGESIA

A. Decadron 10 mg IV, Toradol 30 mg IV, and Marcaine 0.5% SQ and IM

XII. PREINTUBATION TREATMENT

A. Denitrogenation with 100% O₂ for 5 minutes. Atropine to decrease the vagal cardiac response and secretions. Lidocaine 100 mg IV to decrease pharyngeal reactivity and intracranial pressure (ICP)

XIII. COMPETITIVE MUSCLE BLOCKADE

A. Reverse from pancuronium with neostigmine and atropine or glycopyrrolate

XIV. EVOKED POTENTIAL MONITORING

A. Avoid inhalation agents; nitrous oxide and narcotics preferred. Short-acting muscle relaxants are okay, but not benzodiazepines or barbiturates.

B. Turn offnitrous oxide 10 minutes before dural closure to avoid tension pneumocephalus

XV. MALIGNANT HYPERTHERMIA

A. Hypermetabolic state of skeletal muscle due to an idiopathic block of calcium reentry into the sarcoplasmic reticulum causing increased oxygen consumption

B. 50% of patients have had normal anesthesia.

D. Temperature may increase to 44°C (113°F) at 1° per 5 minutes.

E. Watch for increased pCO₂, decreased pO₂, tachycardia, DIC, acidosis, rigid limbs, increased creatine kinase (CK), and ultimately hypotension and death

F. Patients are normally hypothermic with anesthesia.

G. Treatment—stop the anesthesia; change the tubing; administer dantrolene sodium and 100% O₂; lower the core temperature with cool IV fluids; perform wound, nasogastric, and rectal irrigation; administer bicarbonate to decrease acidosis, and insulin and glucose to decrease K⁺H. Test preop with a muscle biopsy to see if it contracts to halothane or caffeine.

I. Watch for masseter spasm after injection of succinylcholine during the case