Orthopedics Flashcards
Bone cement
- polymethylmethacrylate (MMA) cement fills in gaps in bone and binds firmly to prosthetic device
Signs and symptoms of Bone cement implantation syndrome
- hypoxia (due to increased pulmonary shunt)
- hypotension
- dysrhythmias (heart block and sinus arrest)
- pulmonary HTN (due to increased PVR)
- decreased cardiac output
** When is embolization most frequent during orthopedic surgery?
- prosthetic insertion
How do you minimize the effects of bone cement (MMA)?
- increase inspired O2 prior to MMA
- maintain euvolemia
- vasopressor PRN
- Surgical methods (vent distal femur, high pressure lavage of femoral shaft)
What type of reaction causes bone cement to harden?
- exothermic reaction.
Complications associated with bone cement
- embolization of fat, bone marrow, cement and air into femoral venous channels
- residual MMA monomer produces vasodilation and decreases SVR
- tissue thromboplastin release may cause platelet aggregation, microthrombus into lungs and CV instability
Pneumatic tourniquets
- used on upper and lower extremities to create bloodless field and minimize blood loss.
What 7 problems are associated with pneumatic tourniquets?
- hemodynamic changes
- pain
- metabolic changes
- arterial thromboembolism
- pulmonary embolism
- muscle and nerve injury
- limb cooling
What hemodynamic changes are associated with pneumatic tourniquets?
- exsanguination of limb shifts blood volume to central circulation
- cuff inflation: decreased core temperature, increased HR
- prolonged cuff inflation (45-60 minutes): HTN, tachycardia, sympathetic stimulation, sweating
- cuff deflation: decreased CVP, decreased MAP
Tourniquet pain
- severe aching and burning after several minutes
- supplemental analgesia required
- ** slow conduction C-fibers are most affected
- pain less common if regional anesthesia is used
Metabolic changes associated with tourniquets
- metabolic waste products accumulate in the tissue
- cuff deflation causes rapid wash out of waste products
- increased PaCO2, etCO2, serum lactate, potassium
- increased minute volume in spontaneous breathing patients
- dysrhythmias
- reperfusion injuries from free radical formation
What cuff pressures should you use to inflate a tourniquet?
- typically cuff pressure is 100 torr above systolic pressure
- upper extremity: 250 torr
- lower extremity: 350 torr
Why does having the tourniquet inflated cause metabolic changes?
- extremity switches to anaerobic metabolism
- vasculature in the extremity will vasodilate
When is a tourniquet contraindicated?
- in an extremity with calcified arteries
Tourniquet ischemia, especially of the lower extremity, can lead to ____________
- deep venous thrombosis
Muscle and nerve injury associated with tourniquet use
- prolonged inflation (> 2 hours) can cause transient muscular injury, permanent nerve injury and rhabdomylosis
Who is responsible for monitoring tourniquet time?
- anesthetist
Fat embolism syndrome - triad of symptoms
- dyspnea
- confusion
- petechiae (chest, upper extremities, axillary and conjunctiva).
What is the classic timeframe for presentation of fat embolism syndrome?
- within 72 hours of long bone or pelvic fracture
What types of injuries and procedures are associated with fat embolism syndrome?
- long bone fractures
- CPR
- liposuction
- IV lipids
Fat embolism syndrome is ___________ and ____________.
- less frequent
- more fatal (10-20%)
Fat embolism syndrome - pathophysiology
- fat globules are released by disrupted fat cells in fractured bone and enter circulation through tears in medullary vessel
- increased fatty acid levels are toxic to capillary-alveolar membrane
- causes release of vasoactive amines and prostaglandins
- progresses to ARDS, cerebral capillary damage, edema
What 2 coagulation abnormalities are associated with fat embolism syndrome?
- thrombocytopenia
- prolonged clothing times
What changes will you see in a patient with fat embolism syndrome who is under general anesthesia?
- decline in etCO2 and SpO2
- increase in pulmonary artery pressure
Fat embolism syndrome - treatment
- supportive
What are 6 risk factors for deep vein thrombosis and PE?
- age > 60 years
- obesity
- tourniquet
- procedures > 30 minutes
- lower extremity fracture
- immobilization > 4 days
What patients are at highest risk for DVT and PE?
- patients having knee or hip replacements
- ** TKA has the highest risk of all **
- patients over 70
DVT and PE - pathophysiology
- venous stasis
- hypercoagulability from inflammation
- highest incidence in patients over 70
DVT/PE and neuraxial anesthesia
- can reduce risk of DVT and PE
- sympathectomy that is induced actually INCREASES in venous blood flow
- local anesthetics have anti-inflammatory effects
- decreased platelet activity
- decreased rise in factor VIII and Von Willebrand factor
- less decrease in antithrombin III
- less stress hormone release
Neuraxial anesthesia and prophylactic anticoagulation
- risk of spinal or epidural hematoma formation after neuraxial anesthesia in patients who have been given mini-dose heparin or LMWH
- placement of epidural needle or catheter (or removal) should not be done within 6-8 hours of a SQ mini-dose of heparin or 12-24 LMWH
- do not place or removal an epidural needle or catheter in a fully anticoagulated patient
- antiplatelet drugs increase risk of spinal hematoma
Joint manipulation - management
- IV agents with short duration
- general preferred to regional
- can use LMA, mask or ETT
- profound relaxation allows surgeon to distinguish anatomical limitations from patient guarding
- muscle relaxant, succinlycholine or rocuronium may be needed
Closed reduction - management
- usually brief, but can become prolonged
- percutaneous pins
- x-ray/fluoro
- casting/splinting
Predictors of perioperative mortality in patients with hip fractures
- age > 85 years
- history of cancer
- baseline/preoperative alteration in neuro status
- postoperative chest infection
- postoperative wound infection
Hip fractures - regional anesthesia
- hypobaric technique utilized to keep patient off of fracture
- reduces risk of DVT/PE
- reduces blood loss
- quicker return to baseline neurological status
What is the mortality rate associated with hip fractures?
- 10% during initial hospitalization
- 25% in first year following surgery
What are 2 reasons that you would delay repair of a hip fracture?
- coagulopathy
- uncompensated heart failure
Hip fractures - general anesthesia
- consider arterial line and large bore IV for larger fractures
- short acting drugs
- use lower solubility agents
- minimize postoperative cognitive impairment
Arthroscopy
- done to examine interior of joint with endoscope and obtain definitive diagnosis
Arthroscopy - benefits
- less EBL
- less post-operative pain
- less rehab time
Arthroscopy - anesthesia management
- based on joint location, position of patient and tourniquet utilization
- can do general, neuraxial or regional anesthesia
- use LMA for knees and wrists
- use ETT for shoulders
- elbow airway management depends on the position of patient
- pain management: toradol and/or IV Tylenol
- intraarticular injection of bupivacaine and duramorph provide pain relief for early ambulation
What are the indications for a total hip arthroplasty?
- osteoarthritis
- rheumatoid arthritis
- vascular necrosis (from injury or drug abuse)
Total hip arthroplasty - intraoperative management
- position: lateral decubitus
- use of bone cement (MMA)
- DVT/PE prophylaxis
- blood loss: 400-1500 mL, 2000 mL for revisions (have PRBC available, 2 IVs, cell saver or autologous blood donation, regional may be advantageous)
- prevent heat loss
- consider spinal opioids for postoperative pain control
Total knee arthroplasty - intraoperative management
- similar patient population and consideration as hips
- duration: shorter than hip arthroplasty
- EBL: 100-200 mL during surgery due to tourniquet use, more blood loss in 24 hours postoperatively
- less bone cement syndrome than hip
- release of tourniquet can release emboli and increase hypotension (check BP after tourniquet goes down)
- partial knee replacement less invasive but not always shorter duration
- early mobilization
- consider epidural for bilateral total knee arthroplasty
Upper extremity surgery
- can be done open or arthroscopic
- positioning: sitting (beach chair) or lateral decubitus
- consider interscalene block of brachial plexus (very good for pain 80% of time)
Forearm/hand surgery - anesthesia considerations
- length of procedure
- tourniquet use
- consider Bier block or axillary block
- general is best option for lengthy procedures with LMA or ETT
Foot/ankle surgery - anesthesia considerations
- excellent candidates for regional anesthesia
- nerve blocks with IV sedation
- tourniquet use
- LMA with local injection for postoperative pain control
Amputations/re-implantations - anesthesia considerations
- careful attention to positioning
- maintain body temperature (want vasodilation)
- Avoid pain, hypotension, hypovolemia (anything that produces vasospasm or vasoconstriction)
- regulate fluids-go heavier to hemodilute
- maintain blood flow (avoid vasoconstrictors, optimal Hct 28-30%)
- –If you must use a vasoconstrictor, use ephedrine r/t less peripheral vasoconstriction than phenylephrine
- – Dextran or heparin infusion post-op
Interscalene block
- targets brachial plexus TRUNKS (upper arm and shoulder)
- avoid in patients with compromised respiratory status
- risks: pneumothorax, epidural/spinal/arterial injection
- 100% phrenic nerve block on ipsilateral side
- may see Horner’s syndrome, hoarseness (RLN involvement), decreased chest wall sensation
Supraclavicular block
- targets brachial plexus DIVISIONS (upper and lower arms)
- risks: pneumothorax, vocal cord palsy
- 50% phrenic nerve block
Infraclavicular block
- targets brachial plexus CORDS
- useful for surgery of elbow and distal hand
- risk: pneumothorax (1%)
Axillary block
- targets BRANCHES of brachial plexus (distal to elbow)
- injected into the axilla and hits median, ulnar and radial nerve (misses axillary nerve and musculocutaneous nerve)
- risks: hematoma, vascular injection
Femoral nerve block
- loss of quadriceps function increases fall risk
- catheters should be in place for less than 48 hours to avoid infection
- single shot block still increases fall risk
Sciatic nerve block
- can block anywhere along the sciatic nerve
- can affect hip, thigh, knee, lower leg and foot
Popliteal sciatic nerve block
- useful for foot and ankle surgery
- spares hamstring so knee can flex
- allows for easier ambulation
What are hallmarks of spinal or epidural hematoma?
- back pain
- lower extremity weakness
Which type of neuraxial anesthesia has a lower risk of complications in patient’s who have received prophylactic anticoagulation?
- spinal anesthesia (due to smaller needles used vs epidurals)
When will you lose the benefit of regional anesthesia in patients with hip fractures?
- oversedation
- hypoxia
Is there any different in mortality in patients with hip fractures who received regional anesthesia versus general anesthesia?
- no difference after 2 months
What types of hip fractures are associated with the largest amount of blood loss?
- subtrochanteric (greatest)
- intertrochanteric
- base of femoral neck
- transcervical subcapital (least - because the capsule restricts blood supply by acting as a tourniquet)
How can you minimize postoperative cognitive impairment in patients with hip fractures?
- minimize use of midazolam
- maintain oxygenation
- maintain hemoglobin
- maintain normal capnea
How is an undisplaced intracapsular fracture of the hip treated?
- cannulated screws
How is a displaced intracapsular fracture of the hip treatment?
- internal fixation
- hemiarthroplasty
- total hip replacement
How is an extracapsular fracture of the hip treated?
- extramedullary (sliding plate and screws)
- intramedullary implant (gamma nail).
*** What orthopedic procedure has the highest rate of DVT occurrence?
- total knee arthroplasty
Anesthesia considerations for upper extremity surgery
- surgical positioning (beach chair)
- no tourniquet used so potential for large blood loss
- bone cement
What are 7 complications associated with upper extremity arthroplasty?
- pneumothorax
- injury to subclavian veins
- inadvertent extubation
- c-spine injury
- venous air embolism
- fat embolism
- bone embolism
What are 2 interventions that significantly reduce the risk of DVT and PE?
- prophylactic anticoagulation
- pneumatic leg compression
T/F
With pneumatic TQ’s, compartment syndrome can develop is the TQ is too tight
False
can get compartment syndrome if the TQ is NOT tight enough (arterial flow is blocked, but not venous so it builds up).
Heat, expansion, and hardening lead to ____
- Intermedullary HTN (>500 mmHg)
What effects are produced by the residual MMA monomer?
- Decreased SVR, vasodilation
- Significant hypotension
- Decrease in EtCO2
*** Bone cement Implantation Syndrome is most commonly associated with which procedure?
Hip Arthroplasty
What is the first indication of BCIS during general anesthesia?
What is the first indication of BCIS during regional anesthesia?
- Decrease in EtCO2
- Dyspnea, altered sensorium
What complication has the highest incidence with beach chair position for shoulder arthroscopy?
- Hypotensive bradycardic event (HBE)
What complication has the highest incidence with lateral decubitus position for shoulder arthroscopy?
- Temporary paresthesia
Can you use N2O during hip surgery?
No
For CV collapse associated with BCIS, treat it the same as ____
Right-side heart failure ( Aggressive fluid resuscitation, alpha-agonist for hypotension)
For a tension pneumothorax, the most desirable method to relieved increased thoracic pressure is _____
- chest tube
With limb TQ’s, abolition of SSEP’s and nerve conduction occurs within ____
30 mins
With limb TQ’s, application of more than ___ causes TQ pain and HTN
60 mins
With limb TQ’s, application of more than ___ may result in post-op neurapraxia
2 hrs
With limb TQ’s, cellular hypoxia develops within ___
2 mins
With limb TQ’s, endothelial capillary leak develops after ____-
2 hrs
For cefazolin, the preoperative time allotment is within ___ of incision time
1 hr
For vancomycin, the preoperative time allotment is within ___ of incision time
2 hr
TQ size should be ____ size of the limb diameter and the cuff should overlap by ____
- Half
- 3 to 6 inches
Which is harder to anesthetize, mylenated A-delta fibers or unmylinated C fibers?
unmylenated C- fibers
Burning, aching pain correspond to activation of _____
unmyelinated C-fibers (slow conducting)
Pinprick, tingling, and buzzing sensations that frequently accompany TQ application corresponds to activation of _____
A-delta fibers (fast acting)
TQ pain is most consistent with sensation carried out by ____
unmyelinated C-fibers
The potency of bupivicaine is enhanced by ____
increase in HR
may be advantageous by lowering the incidence of TQ pain
For TQ pain associated with leg surgeries, which is more important to block…. thoracic sensory level or the sacral roots?
- Sacral roots
In the lateral decubitus position, the uppermost lung is classified as zone __ and the dependent lung is classified as zone ___
- 1
- 3
In the lateral decubitus position, the alteration ventilation-perfusion distribution is accompanied by reductions in ___ and ___
- Vital capacity
- Tidal volume
For patients undergoing major orthopedic surgeries, intermittent pneumatic compression devices (IPCD) should be used for a minimum of ____
10-14 days
For patients undergoing major orthopedic surgeries, thromboprohylaxis should be continued for up to ____
35 days
TQ should be let down for _____ in between inflations
20 mins
Definition fo hypotensive bradycardia episodes (HBE)
- decrease in HR of at least 30 bpm within a 5 minute interval
- HR less than 50 bpm
- decrease in SBP of more than 30 mmHG within a 5 minute interval
- any SBP below 90 mmHg
The most common mechanism for HBE is activation of _____
Bezold-Jarisch Reflex
What types of procedures are most common for LA toxicity?
Ortho
First sign of LA toxixity
ringing in ears
Late sign of LA toxicity
seizures (benz’s are preferred, avoid propofol)
4 medications to avoid during LA toxicity
- Vasopressin
- CCB’s
- Beta blockers
- Additional LA
Treatment protocol for lipid rescue
- Give 1.5ml/kg bolus,if not effective give few minutes and give again
- Cont infusion 0.25 ml/kg/min – double infusion to 0.5ml/kg/min if BP remains low
- Continue infusion for at least 10mins after obtaining circulatory stability
- Recommended upper limit: approx. 10ml/kg lipid emulsion over the 1st 30mins
6 nerves of ankle/foot
- Sural
- Superficial peroneal
- Saphenous
- Deep peroneal
- Plantar
- Calcaneous (for heel)
____ has the highest rate of DVT’s of all ortho procedures
Total Knee Arthoplasty
The primary concern when caring for a patient with RA is ____
Airway, check neck mobility
- Atlantoaxis (C1-C2) subluxation (main one)
- TMJ involvement
What part of the airway is the most common site for rheumatoid nodule depostion?
Cricoarytenoid joints
T/F
TKA has less bone cement syndrome than hip, but release of emboli w/tourniquet deflation may increase hypotension
True
When will you see the most blood loss from a total knee arthroplasty?
Within 24 hrs post-op
EBL is only 100-200ml, but will see a larger amount of blood loss w/i 24hrs post-op
Which procedure is longer, a total knee arthroplasty or total hip arthroplasty?
THA
What has greater loss, a total hip arthroplasty or a revision?
Revision
Anesthesia concerns for amputations
- Psychological trauma
- Phantom limb pain (regional is best option to block this)
- Regional v General (regional preferred)
T/F
ASA ALONE IS NOT A CONTRAINDICATION TO NEURAXIAL ANESTHESIA
True
Stimulating the lateral cord during a infraclavicular block would cause _____
forearm flexion
Stimulating the posterior cord during a infraclavicular block would cause _____
Wrist extension
Stimulating the medial cord during a infraclavicular block would cause _____
finger and thumb extension
Stimulating the median nerve during a axillary block would cause _____
- Forearm pronation
- Wrist flexion
Stimulating the ulnar nerve during a axillary block would cause _____
- Finger flexion
- Thumb opposition
Stimulating the radial nerve during a axillary block would cause _____
- Wrist extension
The MC nerve runs through the ____, so ask patient to ____ to assess it
- Bicep
- Flex arm
T/F
Bilateral Total Knee Replacements are best served by an epidural
True
Consider a femoral sheath catheter
** When will you see the effects of emboli occur?
When the TQ goes down
The emboli occurs during implantation, but the TQ is holding it in place. Once deflated, then you will see the effects of the emboli and hypotension occur
Mixing polymerized MMA powder with liquid MMA monomer causes _____ and ________
polymerization and cross linking of polymer chains
