Orthopedic Anesthesia Flashcards
T/F: General anesthesia and regional anesthesia present the same amount of risk for DVTs during orthopedic surgery?
False; Regional anesthesia (specifically spinal anesthesia) has a lower incidence of DVTs
What is MMA?
Polymethylmethcrylate cement that fills in the gaps in bones and binds firmly to prosthetic devices
Is MMA an exothermic or endothermic reaction when hardening?
Exothermic, but not typically enough to harm tissues
What thee things lead to a >500 mmHg of pressure on the vascular system with MMA?
- Heat
- Expansion
- Hardening
What are the 8 signs of Bone Cement Implantation Syndrome?
- Hypoxia (increased pulmonary shunt)
- Hypotension
- Dysrhythmias
- Pulmonary HTN (increased PVR)
- Decreased CO
- Vasodilation
- Decreased SVR
- Tissue thromboplastin release may cause microthrombus
What are strategies to minimize effects of MMA?
- Increase FiO2 prior to MMA
- Maintain euvolemia
- Vasopressors if needed
- Surgical methods:
a. Venting distal femur
b. High pressure lavage of femoral shaft
What are the 6 major problems with using a pneumatic tourniquet in orthopedic surgery?
- Hemodynamic changes
- Pain
- Metabolic changes
- Arterial and Pulmonary embolism
- Muscle and nerve injury
- Limb cooling
What is typical cuff pressure for tourniquet use?
100 torr above SBP
usually Upper extremities 250 torr and Lower extremities 350 torr
Which type of nerve fibers are typically most stimulated by the tourniquet?
Unmylenated, slow conduction C Fibers
Do regional anesthesia techniques decrease or increase tourniquet specific pain?
Decrease
What metabolic changes can be seen with cuff deflation?
- Increase PaCO2
- Increase EtCO2
- Serum Lactic Acidosis
- Hyperkalemia
What is the maximum time period for tourniquet inflation?
2hrs (20 mins for reperfusion, then can put tourniquet up again)
What three things are associated with prolonged tourniquet inflation time (>2hrs)?
- Transient Muscular injury
- Permanent nerve injury
- Rhabdomylysis
Who’s responsibility is the tourniquet time?
Anesthesia provider
What is the triad of Fat Embolism Syndrome?
- Dyspnea
- Confusion
- Petechiae
What typically precipitates Fat Embolism Syndrome?
Classic presentation within 72 hours of long bone or pelvic fracture.
What are the two most important times during orthopedic surgery with tourniquet use?
- Tourniquet up/down
2. During device placement/removal
What is the pathology behind Fat Embolism syndrome?
Disrupted fat cells from bone fracture enter circulation causing increase in fatty acid levels. This releases vasoactive amines and prostaglandins which progresses to ARDS, cerebral capillary damage, and edema
How is fat embolism syndrome diagnosed?
- Petechiae of chest and upper extremities.
- Fat globules in retina, urine, sputum
- Coagulation abnomalities
- Progressive pulm worsening from mild hypoxia to ARDS
- Abrupt decline in EtCO2 and spO2. and Rise in PIPs
What are the 6 major risk factors for DVT and PE?
- > 60yrs
- Obesity
- Tourniquet
- > 30min procedure
- Lower extremity fracture
- Immobilization >4days
Which two surgeries place patients at the highest risk for DVT/PE?
Knee and hip replacements
T/F: Even with prophylactic anticoagulation and pneumatic leg compression, DVT/PE incidence remains the same?
False; these two thing significantly reduce incidence of DVT/PE
What age group has the highest incidence of DVT/PE?
> 70 yrs
What is Neuraxial anesthesia’s role in DVT/PE?
- Sympathectomy induces increased venous blood flow
- Anti-inflammatory effects of LAs
- Decreased platelet activity
- Decreased rise in Factor VIII and vWF
- Less fall in antithrombin III
- Less stress hormone release
What is the timeframe for epidurals and prophylactic anticoagulation?
Placement or removal should not be undertaken within 6-8hrs of SQ minidose heparin or within 12-24hrs of LMWH
What are the two hallmark signs of hematoma surrounding neuraxial anesthesia?
- Back pain
2. Lower extremity weakness.
T/F: ASA should not be given within 6-8hrs of neuraxial anesthesia?
False; ASA by itself is not a contraindication for neuraxial anesthesia
For management of a joint manipulation, is general or regional preferred?
General Anesthesia
T/F: Muscle relaxation should never be used for joint manipulations?
False; Profound relaxation allows surgeon to distinguish anatomical limitations from patient guarding
Why might regional anesthesia be selected for joint manipulation?
- Pt with multiple medical problems
- Pt with fulls stomach
.
What are the mortality rates of hip fx in the hospital and at 1 year?
10% during initial hospitalization.
25% at 1 year
What are two major reasons to delay hip fracture repair?
- Coagulopathy
2. Uncompensated heart failure
What are the 5 predictors of peri-operative mortality with hip fractures?
- Age >85yrs
- Hx Cancer
- Baseline/pre-op alteration in neuro status
- Post-op chest infection
- Post-op wound infection
Which baricity of LA would be used for broken hip up neuraxial anesthesia?
Hypobaric solution
What are the benefits of regional over general for hip fx repair?
- Reduced blood loss
- Reduced DVT/PE
- Quicker return to baseline neuro
List the hip fractures in order of most blood loss to least blood loss associated with it?
- Subtrochanteric
- Intertrochanteric
- Base of femoral neck
- Transcervical
- Subcapital
What four measures reduce post-op cognitive impairment for hip fx repair?
- Minimize use of midazaolam in older pt
- Maintain oxygenation
- Maintain hemoglobin
- Maintain normal capnea
What are the benefits of arthroscopy?
- Less blood loss
- Less post-op pain
- Less rehab time
T/F: Knees, shoulders, and wrist arthroscopy should all be done with LMA?
False; shoulder should be done with ETT
Why do some surgeons not like Toradol given?
- Decreased bone growth
2. Bleeding risk increases
What 4 factors need to be considered with a patient with Rheumatoid Arthritis?
- Immune mediated joint destruction with synovial inflammation
- Systemic involvement w/ significant deformity
- Atlantoaxis (C1-C2) subluxation and TMJ involvement
- Use of steroids, anti-inflammatories, methotrexate
What are the 3 major indications for THA?
- Osteoarthritis
- Rheumatoid Arthritis
- Vascular necrosis
At what time is an embolic event most likely during THA?
Most frequent at insertion of femoral component
What is typical blood loss for THA? Revision THA?
THA= 700-800 (400-1500ml)
THA Revision=2000ml
Which ortho procedure has the highest rate of DVT?
Total Knee Arthroplasty
T/F: EBL for TKA is much higher (>2000ml) than THA?
False; 100-200ml limited by tourniquet
What is significant to remember about blood pressure management for upper extremity surgeries?
Typically will be in beach chair, head up position. Remember to Maintain BP at the level of their brain
Which block is helpful for shoulder surgery?
Interscalene block, but only 80% of pain
Why might GA be a better option for length upper extremity surgeries?
Regional may block pain well enough but patient unable to sit their without moving for that length of time.
T/F: Foot/ankle surgery cases are not considered good candidates for regional anesthesia?
False; excellent candidates.
Would a tourniquet work better at limiting blood flow on the upper leg or lower leg and why?
Upper leg because only 1 bone to compress
Why would regional anesthesia benefit patients with limb amputation?
Not well documented, but may be d/t decreasing phantom limb pain.
What are 4 things to do in order to maintain good blood flow during re-implantation surgeries?
1. Thin blood by optimizing Hct at 28- 30% 2. Keep warm 3. Avoid vasoconstrictors 4. Dextran and heparin infusion intraop
Which upper extremity block targets brachial plexus cords?
Infraclavicular
Which upper extremity block targets brachial plexus trunks?
Intrerscalene
Which upper extremity block targets brachial plexus divisions?
Supraclavicular.
Which upper extremity block targets brachial plexus branch(es)?
Axillary
Which upper extremity block has highest risk of pneumothorax?
Supraclavicular
What branches of the brachial plexus are blocked with an axillary PNB?
Medial, ulnar, and radial nerves
not the axillary or musculocutaneous nerves
Which block typically blocks 100% ipsialateral phrenic nerve?
Interscalene
How to assess axillary PNB?
Wrist flexion=median nerve
Wrist extension=radial nerve
Thumb opposition=ulnar nerve
Interscalene will block what areas of the upper extremity?
Shoulder to hand.
Is the supraclavicular block good for shoulder surgery?
No; mostly upper arm to hand.
How to check for infraclavicular block success?
Forearm flexion=lateral cord
Wrist extension=posterior cord
Fingers and thumb movement=Medial cord
Which branch would need blocked for bicep repair?
Musculocutaneous
Why are femoral nerve blocks not used often?
Loss of quad function creates a higher risk of falls
What PNB would be ideal for foot and ankle sugrery
Popliteal-sciatic nerve block.
What nerve covers the lateral aspect of the foot?
Sural nerve
What nerve covers the medial aspect of the ankle?
Saphenous nerve
What nerve would cover most of the great toe and underside of the front of the foot?
Plantar nerve