Updated: 10/11/2016

Anesthesia

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Anesthesia
  •  Components of anesthesia
    • amnesia
    • anxiolysis
    • analgesia
    • akinesia
    • attenuation of autonomic repsonses to noxious stimuli
General Anesthesia
  • Pharmacologically induced, reversible loss of conciousness, irrespective of airway management
    • inhalational anesthesia
      • by volatile liquids vaporized in a carrier gas including
        • isoflurane
        • sevoflurane
        • desflurane
        • nitrous oxide
          • associated with increased gaseous abdominal distension
          • leads to increased difficulty with fluoroscopic identification during pelvic and spinal procedures 
    • intravenous anesthesia
      • non-opioids
        • propofol
        • etomidate
        • benzodiazepines
        • dexmedetomidine
        • ketamine
      • opioids
        • fentanyl, alfentanil, sufentanil, remifentanil
        • morphine
        • hydromorphone
      • neuromuscular blocking agents
        • depolarizing agents
          • bind to, depolarize, and transiently block ACh receptor
            • short-acting: succinylcholine
            • no intermediate or long-acting agents
        • non-depolarizing agetns
          • bind to and transiently block ACh receptor, but do not depolarize
            • no short-acting agents
            • intermediate-acting: rocuronium, vecuronium, atracurium, cisatracurium
            • long-acting: pancuronium
Local Anesthesia - Upper Extremity
  • Interscalene regional block 
    • indications
      • commonly used for shoulder/upper arm/elbow surgery
    • technique
      • performed by injecting local anesthetic to the nerves of the brachial plexus as it passes through the groove between the anterior and middle scalene muscles at the level of the cricoid cartilage
    • complications
      • sensory neuropathy is most common complication 
  • Supraclavicular block
    • indications
      • ideal for operations involving the arm and forearm, from the lower humerus down to the hand.
    • technique
      • targets brachial plexus superior to the clavicle
    • complications
      • nerve injury and intravascular injection
      • pneumothorax, dyspnea damage to the subclavian artery
  • Infraclavicular block  
    • indications
      • ideal for operations involving the arm and forearm, from the lower humerus down to the hand.
    • technique
      • targets brachial plexus inferior to the clavicle
  • Axillary block
    • indications
      • postoperative analgesia for surgery to the elbow, forearm, wrist and hand
  • Bier block  
    • indications
      • short (< 60 mins) operative procedures (i.e., carpal tunnel release) in the hand and forearm
    • technique
      • Esmarch exsanguination and tourniquet inflation
      • inject lidocaine through a small, distal (hand) intravenous catheter on the surgical side
      • deflate tourniquet after a minimum of 30 minutes to avoid venous release of local anesthetic and potential local anesthetic systemtic toxicity (LAST)
Local Anesthesia - Spinal
  • Spinal
    • indications
      • often used for knee and hip arthroplasty
    • technique
      • a single injection with a small 24 or 27-gauge needle
      • combination of morphine and bupivacain is often used
    • complications
      • spinal headache (decreased with small gauge needle), hematoma and opioid side effects (nausea, vomiting, purities, respiratory depression)
  • Epidural
    • indication
      • often used for knee and hip arthroplasty
    • technique
      • similar to spinal anesthesia, except an indwelling catheter is placed
      • combination of opioid and local anesthetic
    • complications
      • postoperative hypotension and motor impairment
      • spinal headache, hematoma and opioid side effects (nausea, vomiting, pruritus, respiratory depression)
  • Combined spinal epidural
    • indications
      • often used for knee and hip arthroplasty 
    • technique
      • an epidural needle is placed into the epidural space and spinal anesthesia is administered through a spinal needle followed by placing an epidural catheter
    • complications
      • postoperative hypotension and motor impairment
      • spinal headache, hematoma and opioid side effects (nausea, vomiting, purities, respiratory depression)
Local Anesthesia - Lower Extremity
  • Lumbar plexus/ psoas compartment nerve block
    • indications
      • surgeries involving the hip, anterior thigh and knee
      • a sciatic block can be given concomitantly to provide pain relief to the entire lower extremity 
    • technique
      • targets the lumbar plexus (L1 to L4 spinal nerves) which form the obturator nerve, lateral femoral cutaneous nerve, and femoral nerve
      • the injection is usually placed 3-5 cm lateral to the spinous process of L4 and is often guided by ultrasound and nerve stimulators
    • complications
      • nerve damage and intravascular injection
      • epidural diffusion, retroperitoneal hematomas, intrathecal injections and an increased risk of falls
  • Femoral nerve block
    • indications
      • surgeries around the knee
      • concomitant sciatic nerve block can be done to increase analgesia around the knee
    • technique
      • targets the femoral nerve (L2-L4)
      • the injection occurs just lateral to the femoral artery and on a line connecting the anterior superior iliac spine to the pubic symphysis
    • complications
      • nerve damage and intravascular injection
      • increased risk of falls, prolonged quadriceps weakness and infections
  • Sciatic nerve block
    • indications
      • surgeries involving the leg, ankle and foot
      • can be combined with the femoral or lumbar plexus block to provide analgesia to the entire lower extremity
    • technique
      • targets the sciatic nerve providing analgesia to the common peroneal and tibial nerves
      • multiple techniques have been described
        • lines are drawn between the greater trochanter and the posterior superior iliac spine (PSIS), and the greater trochanter and the sacral hiatus
        • halfway between the greater trochanter and the PSIS a perpendicular line is drawn, and the injection is placed where the perpendicular line crosses the line between the greater trochanter and the sacral hiatus
      • complications
        • nerve damage and intravascular injection
        • vascular injury, heel ulcers and a delay in diagnosis of nerve injuries after surgery
  • Obturator nerve block
    • indications
      • adductor muscle spasm, severe hip pain from osteoarthritis
      • adjuvant pain management for knee surgeries
    • technique  
      • targets the anterior and posterior branch of the obturator nerve
      • blocking the anterior branch leads to decreased sensation at the hip joint and inner thigh, where blocking the posterior branch decreases sensation around the knee
      • injection site is usually 2 cm inferior and 2 cm lateral to the pubic tubercle
    • complications
      • nerve injury and intravascular injection
      • damage to structures in the pelvic cavity
  • Popliteal nerve block
    • indications
      • used for surgery around the foot and ankle
      • often used in conjunction with the saphenous nerve block
    • technique
      • targets the sciatic nerve prior to its bifurcation
      • injection site is often 10 cm proximal to the popliteal crease
    • complications
      • nerve injury and intravascular injection
      • hematoma, persistent foot drop and pressure sores
  • Saphenous nerve block
    • indications
      • procedures around the medial aspect of the knee, leg and ankle
    • technique
      • targets the saphenous nerve
      • multiple different techniques, but it is often blocked behind the sartorius muscle
    • complications
      • nerve injury and intravascular injection
      • hematoma and infection
Blood Management
  • Risks of transfusion
    • transfusion errors
    • allergic reaction
    • infection
    • down-modulation of immune system
  • Ways to reduce postop anemia and need for allogeneic transfusion  
    • surgical
      • hemostasis
      • meticulous dissection
    • transfusion triggers
      • example of strict transfusion triggers based on hemoglobin levels
        • average patient, 8.1g/dl
        • young (<60yr) patients without co-morbidity, 6.5g/dl
        • compromised patients, 9.7g/dl
    • subcutaneous epoetin injections
      • used preop for patients with low Hb (10-13g/dl)
      • able to bring up Hb by 1.9d/dl
      • administer with supplementary PO iron
      • dosing
        • long interval to surgery
          • 600IU/kg once weekly x 3wk before surgery
        • short interval to surgery
          • 300IU/KG daily x 2wk
    • autologous blood donation (ABD) and acute normovolemic hemodilution (ANH)
      • ABD
        • donate 1-2 units preoperatively
      • ANH
        • collect 2-3 units at 1 hour preoperatively
        • receive crystalloid/colloid intraoperatively
        • re-infuse ABD blood postoperatively
    • COX2 inhibitors analgesia (instead of COX1 NSAIDS)
      • Avoids antiplatelet effects of
    • anti-coagulation management
      • stop anticoagulation a few days preoperatively
      • restart just before surgery
    • platelet rich plasma (PRP), fibrin sealants, anti-fibrinolytics
      • PRP
        • apply PRP to wounds might reduce capsule/subcutaneous bleeding
        • fibrin sealants
          • very low risk of infection from microbial/viral contamination during processing
        • antifibrinolytics
          • aprotinin
          • tranexamic acid (TXA)
            • topical
            • IV
    • hypotensive epidural anesthesia (HEA)
      • epidural dermatomal block from T2 distal
      • blocks cardio-accelerator fibers of sympathetic chain
        • causes bradycardia which is treated with low-dose epinephrine
        • lowers MAP to 50mmHg
        • keeps normal heart rate, CVP, stroke volume, cardiac output
        • can be used in high risk patients with
          • hypertension
          • poor cardiac function
          • chronic kidney disease
    • cell saver
      • expensive
      • intraoperative
        • washed vs unwashed (filtered)
        • indications
          • revision surgery
          • high EBL
          • contraindications
            • infection
            • malignancy
            • EBL <500ml
      • postoperative
        • filtering of shed blood (trap clots and debris)
        • within 6h of end of surgery to avoid bacterial contamination, febrile reaction
        • after 6h, converted to vacuum drain (not retransfused)
Complications
  • Malignant hyperthemia
    • rare (1:15,000 to 1:50,000) life-threatening condition
    • autosomal dominant transmission
      • abnormalities in the ryanodine receptor (RYR1) gene
    • triggers
      • volatile inhalational anesthetic agents 
      • succinylcholine 
    • symptoms
      • hypermetabolic state 
        • increased skeletal muscle contraction and metabolism
          • rigidity
          • masseter spasm
        • rapid oxygen depletion
      • increased carbon dioxide concentration (EtCO2) and body temperature
    • outcome 
      • if untreated, leads to circulatory collapse and death
    • treatment
      • provide antidote
      • active cooling
    • antidote
      • dantrolene (calcium blocker)  
  • Local anesthetic systemic toxicity (LAST) 
    • intravascular bupivicaine 
      • effect
        • CNS
          • seizures, coma, respiratory arrest
        • CVS
          • asystole, ventricular fibrillation, cardiac arrest
      • antidote
        • intravenous 20% lipid emulsion
  • Bone cement implanation syndrome
    • associated with use of bone cement during joint arthroplasty procedures
    • symptoms
      • hypotension
      • hypoxemia
    • treatment
      • intravenous fluids
      • vasopressors
      • 100% inspired oxygen
 

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(OBQ07.95) A surgeon recommends an interscalene regional block to a patient undergoing shoulder arthroscopy. When asked about potential complications, which of the following is most likely to occur? Review Topic

QID: 756
1

Persistent motor neuropathy

3%

(17/513)

2

Sensory neuropathy

61%

(312/513)

3

Complex regional pain syndrome

2%

(12/513)

4

Pneumothorax

33%

(167/513)

5

Cardiac arrythmia and arrest

1%

(4/513)

ML 3

Select Answer to see Preferred Response

PREFERRED RESPONSE 2

(OBQ08.141) Nitrous oxide has which of the following important effects when used during orthopedic procedures? Review Topic

QID: 527
1

Potential interaction with oral contrast material

1%

(23/2060)

2

Slow induction times

15%

(309/2060)

3

Interferes with self-passivation of titanium implants

13%

(265/2060)

4

Gaseous abdominal distension

59%

(1209/2060)

5

Increases risk of metal ion release from stainless steel implants

12%

(243/2060)

ML 3

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PREFERRED RESPONSE 4
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