Hemophilia A and B factor deficiencies
A: Factor 8
B: Factor 9
(Remember: Aight is followed by 9)
Hemophilia considerations
- High risk periop bleeding (especially consider bleeding into closed spaces)
- Possible contraindication neuraxial (may be considered if factor level >50%)
- optimize factors and identify factor antibodies
- blood loss conservation strategies
Hemophilia A optimization
- DDAVP for mild disease
- Recombinant factor VIII (Humate P)
- Factor VIII concentrates (fresh frozen plasma contains minimal factor VIII)
- Recombinant factor VIIa for inhibitors (approved indication)
- Cryoprecipitate if nothing else available (this is the only standard fractionated blood product containing meaningful amounts of factor VIII)
Factors in cryoprecipitate
Factor VIII
fibrinogen
von Willebrand factor
fibronectin
factor XIII
Hemophilia B optimization
- Recombinant factor IX
- Factor IX concentrates
Hemophilia severity by % factor levels
Classification by factor levels:
Mild: 5-25%
Moderate: 1-5%
Severe: <1%
Trough Factor VIII levels for different types of surgery in VWD
Key trough factor VIII levels:
Obstetric > 50%
Minor surgery > 30%
Major surgery > 50%
VWD management
- DDAVP 0.3 mcg/kg (provides 3-5 fold increase in activity); only if known responder; works by stimulating the release of vWF from endothelial cells
- Factor VIII-vWF concentrates (Humate P)
- Platelet concentrates (contains vWF)
- Recombinant factor VIII
- Recombinant factor VIIa
- Emergency: cryoprecipitate (contains vWF, FVIII, FXIII, fibronectin, fibrinogen)
What is VWD?
Quantitative or qualitative deficiency in von Willebrand factor.
VWF functions as a carrier for factor VIII to maintain its levels and help in platelet adhesion and binding to endothelial components after a vascular injury. Made by endothelial cells and secreted into the vascular lumen.
Types of VWD
Inherited:
- Type 1: AD, partial quantitative deficiency
- Type 2: AD, qualitative defects
- Type 3: AR, completely absent
Acquired:
- functional impairment in cancers, inflammatory conditions, etc.
- including high-vascular flow such as AS, VSD, VAD, ECMO, or metallic cardiac valves. (The von Willebrand factor is a large multimeric glycoprotein, susceptible to the shear stress associated with high flow states.)
Post op visual loss - types and associations
CAPO
Central retinal artery occlusion
Anterior ischemic optic neuropathy - pressure on eye
Posterior ischemic optic neuropathy - prone spinal surgery (surgery >6.5 hrs, large EBL)
Occipital stroke
Oxyhemoglobin dissociation curve - leftward shift
Increased affinity (less O2 release)
Decreased temp
Decreased 2,3-DPG
Alkalosis/hypocarbia
CO
Oxyhemoglobin dissociation curve - rightward shift
Reduced affinity (offload O2)
Increased temp
Increased 2,3-DPG
Acidosis/hypercarbia
Peds ETT size
Uncuffed = (age in years/4) + 4
Cuffed = (age in years/4) + 3
Newborn usually 3-0 uncuffed
Standard ASA monitors
Circulation, oxygenation, ventilation, and body temperature
“Non-invasive BP cuff, continuous pulse oximetry, continuous 5-lead EKG, end-tidal capnometry if patient has a secured airway, as well as temperature monitoring if clinically significant changes in temperature are anticipated.”
Circulation: BP and HR q5min minimum, continuous EKG, continuous circulation (eg pulse ox pleth)
Oxygenation: oxygen analyzer, pulse ox
Ventilation: continual EtCO2 monitoring if secure airway, disconnect alarm. If sedation, clinical signs + capnography
Body temp: body temp monitored if clinically significant changes expected
Sickle Cell Anemia: systems affected
Neuro: stroke, acute pain crisis (vaso-occlusive crisis), chronic pain
Cardiac: LVH, high-output cardiac failure, MI without CAD
Pulm: Acute chest syndrome, pulmonary fibrosis (restrictive lung disease), pulm HTN
GI: splenic sequestration and infarcts
Renal: renal failure, renal infarcts
Heme: chronic hemolytic anemia
Sickle Cell Anemia: sickle cell crisis precipitants
- Hypoxia
- Acidosis
- Hypovolemia/hypotension (avoid dehydration while NPO)
- Hypothermia
- Vascular stasis
Sickle cell disease: preoperative transfusion
- Controversial, reasonable to consider target Hct 30
- Always have blood available for any surgery
- Exchange transfusion not routinely recommended
Acute chest syndrome
- Acute respiratory syndromes + fever or new infiltrate on CXR; can progress to ARDS
- Pulmonary vaso-occlusion due to sickled cells in small pulmonary vessels
- May be precipitated by infection, atelectasis, fat embolism, or thromboembolism
Additional monitors to consider (besides standard ASA)
- Foley catheter
- CVP
- Art line
- PA catheter
- neuromuscular blockade monitor
- MEP
- SSEP
- processed EEG
- TEE
Respiratory parameters that can be used to extubate
- RR between 10-30
- TV > 5cc/kg IBW
- SpO2 >95 with FiO2 < 40%
- vital capacity > 10cc/kg IBW
What is RSBI
RR divided by TV in liters
RSBI <100 predicts successful extubation
Normal cerebral blood flow and how it is affected by CO2
Normal: 50mL/100g/min
CBF changes by 1mL/100g/min for every 1mmHg change in PaCO2 from 40. Effect plateaus when <20 or >80.
What is cerebral autoregulation?
CBF remains constant between MAP 50-150
Note: chronic HTN shifts the autoregulatory curve right
