20110218

Anesthesia for Orthopedic Surgery

Anesthesia for Orthopedic Surgery
Backgroynd
Diversity
Minor to major procedure
Full of risks
Healthy patients to very sick patients
Lokal, regional or general anesthesia
Indication or contraindication

Consideration for orthopedic patients
Age
Trauma or non trauma
Diagnosis
Tipe of surgery or procedure
Co-existing disease
ODS or in admittance
Choose anesthetic technique
Intraoperative issues
Postoperative care

Pre-operative Visit
Patient data : age, gender, jobs,etc
History of disease: current illness, co-existing disease, allergy
Physical examination: anatomy (airway, spine, chest), physiology
Other examination: Laboratory, ECG, PFT, ABGs, Radiology
Premedication

Age
Neonate to geriatric
Congenital disease or degenerative disease
Conjunction to other diseases: rheumatoid arthritis, myocarditis, tuberculosis, osteoporosis
Reconstruction, repair or supportive

Trauma Patients
Airway and ventilation à oxygen delivery
Major blood loss à circulatory
Resuscitation
Other trauma
Set priority
Anesthetic concerns

Tipe of surgery or procedure
Minor or major surgery
Location of surgery
Positioning
Tourniquet inflation/deflation
Methylmetacrylate use

Choose anesthetic technique
General vs Regional
Site of operation
Patient condition
Positioning
Relaxation
Hemodynamic stability
Somatic and viscera pain
Monitoring

Intraoperative Issues
Massive blood loss
Metylmethacrylate allergy
Embolization
Tourniquet pain

Special Considerations in Orthopedic Surgery
Bone Cement
Pneumatic Tourniquets
Fat Embolism Syndrome
Deep Venous Thrombosis & Thromboembolism

Bone cement, polymethylmethacrylate
required for joint arthroplasties
binds the prosthetic device to the patient's bone
exothermic reaction
intramedullary hypertension (> 500 mm Hg) à embolization of fat, bone marrow, cement, and air into the femoral venous channels
vasodilation and a decrease in systemic vascular resistance
platelet aggregation, microthrombus formation in the lungs, and cardiovascular instability

Bone cement implantation syndrome
Hypoxia
Hypotension
Dysrhythmias
Pulmonary hypertension
Decreased cardiac output
Emboli

Strategies to minimize the effects
increasing FiO2 prior to cementing
maintaining euvolemia
creating a vent hole in the distal femur to relieve intramedullary pressure
performing high-pressure lavage
using an uncemented femoral component

Pneumatic Tourniquets
creates a bloodless field that greatly facilitates surgery
shift of blood volume into the central circulation
potential problems : hemodynamic changes, pain, metabolic alterations, arterial thromboembolism, pulmonary embolism
Inflation pressure 100 mm Hg + SBP
Prolonged inflation (> 2 h) à transient muscle dysfunction , permanent peripheral nerve injury or even rhabdomyolysis
contraindicated in patients with significant calcific arterial disease.

Tourniquet pain
Unmyelinated, slow-conduction C fibers
gradually becomes so severe over time
increasing MAP ¾ to 1 h after cuff inflation
progressive sympathetic activation
Influenced by anesthetic technique (intravenous regional > epidural > spinal > general anesthesia), intensity and level of regional anesthetic block, choice of local anesthetic and supplementation of the block with opioids

Cuff deflation
relieves tourniquet pain and hypertension
fall in CVP and ABP
HR usually increases and core temp decreases
increases PaCO2, ETCO2, and serum lactate and potassium levels
metabolic alterations can cause an increase in minute ventilation in the spontaneously breathing patient and, rarely, dysrhythmias
worsen ischemic tissue injury due to the formation of lipid peroxides.

Fat Embolism Syndrome
some degree of fat embolism probably occurs in all cases of long-bone fracture
potentially fatal (10–20% mortality)
within 72 h
triad of dyspnea, confusion, and petechiae
fat globules are released by the disruption of fat cells in the fractured bone and enter the circulation through tears in medullary vessels.
Neurological manifestations (agitation, confusion, stupor, or coma) represent capillary damage to the cerebral circulation and cerebral edema and exacerbated by hypoxia.

Diagnosis and Treatment
Diagnosis : petechiae on the chest, upper extremities, axillae, and conjunctiva. Fat globules may be found in the retina, urine, or sputum.
Coagulation abnormalities, serum lipase activity elevated, pulmonary involvement progresses from mild hypoxia and a normal chest radiograph to severe hypoxia and a chest film diffuse patchy pulmonary infiltrates.
Classic signs and symptoms occur 1–3 days after the precipitant event.
Signs during general anesthesia : decline in ETCO2 and arterial oxygen saturation or a rise in pulmonary artery pressures.
ECG ischemic-appearing ST-segment changes and right-sided heart strain.
Treatment is 2-fold: prophylactic and supportive

Deep Venous Thrombosis & Thromboembolism
major causes of morbidity and mortality
obesity, age > 60 years, procedures lasting > 30 min, use of a tourniquet, lower extremity fracture, and immobilization for more than 4 days
undergoing hip surgery and knee reconstruction
venous stasis and a hypercoagulable state due to localized and systemic inflammatory responses to surgery
Prophylactic anticoagulation and use of intermittent pneumatic (leg) compression

Anesthetic technique
implementation of contemporary surgical and anesthetic management strategies, eg, routine DVT prophylaxis, early rehabilitation, and more frequent use of regional anesthesia.
Neuraxial anesthesia alone or combined with general anesthesia reduce thromboembolic complications by several mechanisms : sympathectomy-induced increases in lower-extremity venous blood flow, systemic antiinflammatory effects of local anesthetics, decreased platelet reactivity, attenuated postoperative increases in factor VIII and von Willebrand factor, attenuated postoperative decreases in antithrombin III, and alterations in stress hormone release.
Intravenous lidocaine : enhance fibrinolysis, and decrease platelet aggregation.

Anticoagulation or fibrinolytic therapy
spinal or epidural hematoma
Placement of an epidural needle or catheter not be undertaken within 6–8 h of a subcutaneous "minidose" of unfractionated heparin
high-risk patients, low-dose heparin, 5000 U every 8 h, IPC, warfarin, or low-dose molecular weight heparin (LMWH)

Postoperative issue
Pain management
Volume replacement
DVT prophylactic
Neurologic status
Position neuropathy
Out patient status: ambulation, pain control
Other complications

Summary
Orthopedic surgery challenges the anesthesiologist with its diversity.
The degree of surgical trespass varies from minor finger surgery to hemipelvectomy.
Orthopedic patients range from neonates with congenital anomalies to healthy young athletes to immobile geriatric patients with end-stage multiorgan failure
Patients are at risks for complication even for a small procedure.

Thank You
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