ch 21 Flashcards
acids and bases
acids are H+ donors
base is a proton acceptor
BE
base excess less than 0 is metabolic acidosis
value greater than 0 is metabolic alkalosis
used in clinical practice to determine lactic acidosis and determine adequacy of intravascular volume resusciation
pka
the strength of an acid
bilateral carotid endarterectomies…
abolish the peripheral chemoreceptor response and these patients have no hypoxic ventilatory drive.
peripheral chemoreceptors
located at the carotid arteries and surrounding the aortic arch. carotid bodies are principle and are sensitive to changes in pa02, pac02, ph and arterial perfusion pressure. most sensitive to pa02
central chemoreceptors
in the medulla and respond to changes in cerebrospinal fluid ph. co2 goes up -chemoreceptors are activated- and alveolar ventilation increases. this works except for very very high or very very low pac02
renal response compensation during acidosis
- reabsorption of the filtered HC03
- excretion of titratable acids
- formation of ammonia.
sampling delay
can lead to oxygen consumption and carbon dioxide generation by the metabolically active white blood cells.
oxygenation
p02 decreases 6% for every 1C degree
p02 increases 6% for every 1C degree
rapid c02 increase
myocardial dysfunction then metabolic acidosis leading to confusion and loss of consciousness. due to the abrupt decrease in ph.
chronic increases are well tolerated
causes of respiratory alkalosis
increased minute ventilation (tvxbpm) hypoxia- high altitude low fi02 severe anemia iatrogenic (mechanical ventilation) anxiety and pain cos disease (tumor infection trauma) fever, sepsis drugs (salicylate, progesterone, doxapram) liver disease pregnancy restrictive lung disease pulmonary embolism
causes of respiratory acidosis
increased c02 production
malignant hyperthermia
hyperthyroidism
sepsis
overfeeding
decreased co2 elimination
pna, ards, fibrosis, edema
laryngospasm, foreign body, ova
lower airway obstruction asthma and cold
chest wall restriction-obesity scoliosis, burns
cns depression- anesthetics opioids cis legions
decreased skeletal muscle strength
increase co2 rebreathing or absorption
exhausted soda lima
incompetent one way valve in breathing circuit
laparoscopic surgeryanion gap
(CL+hc03) - Na
normal gap is 8-12
three main regulatory molecules control coagulation and facilitate the termination of the coagulation cascade
antithrombin
tissue factor pathway inhibitor
activated protein C
patient with less than what percent or what value are more likely to have uncontrolled intraoperative bleeding
20-30% or less than 50,000
hemophilia A & B
most common recessive inherited deficiencies.
A is deficiency in factor VIII
B is deficiency in factor IX
Prolonged PTT, normal platelet count and pt
hemophilia C or rosenthal disease
autosomal recessive disorder that can be associated with bleeding and is characterized by a prolonged ptt
thorough preoperative evaluation plus consult with hematologist is necessary to manage preoperative care.
factor XII deficiency
a prolonged putt and is associated with clotting rather than bleeding .
Factor XIII
stabilizing the fibrin clot, delayed bleeding after hemostasis, impaired wound healing, and pregnancy loss
von willebrand disease
most common inherited bleeding disorder. 1% of the general population. multiple binding sites for both platelet receptors and sub endothelial structures.
ddavp- treatment of choice for type 1.
DDAVP contraindicated in type 2b
ddavp- type 3 do not respond to this treatment- they need factor VIII and vWF concentrates
vitamin K deficiency
fat soluble vitamin that is required for carboxylation of factors II, VII, IX, and X and proteins C&S.
(leafy greens)
patients with poor dietary intake, TPN, ileus or obstruction, newborns, oral antibiotic therapy are susceptible to vitamin k deficiency
liver disease
clotting factors (except factor VIII are synthesized in the liver.
what should not be used with hemophilia B
cryoprecipitate
protein c protein s
protein c can be acquired secondary to underlying disease. seen with liver disease, severe infection, septic shock, and dic.
protein s associated with pregnancy, oral contraceptives, dic hiv, nephrotic syndrome and liver disease.
DIC
caused most commonly from sepsis
widespread systemic activation of coagulation. leads to end organ dysfunction and multi organ failure.
consumption of of circulating coagulation factors platelets and fibrinogen results in life threatening bleeding.
thrombocytopenia
elevated fibrin degradation products (d dimer)
prolonged pt and ptt
low fibrinogen
TXA-
in patients with active bleeding and suspected fibrinolysis antifibrolinitcs are administered.
ACT
used for heparin monitoring in CABG patients. ACT must be greater than 400 to start bypass.
plavix
noncompetitive irreversible antagonist. increased variability among population.
ticagrelor has much lower inter individual variability.
warfarin
disrupts the formation of factor II, VII, IX and X and proteins C&S
40hr half life.
early reductions in the anticoagulant protein c causes hyper coagulable state.
heparin
main complication of heparin is HIT. mortality rate of HIT is 30-40% suspect if platelets fall less than 100,000 or less than 50% baseline 5-10 days after initiation of heparin …if patient previously hit positive for cabg, titers to heparin should be preformed if timing allows.
low molecular weight heparin
inhibit factor Xa
do not affect the ptt
assess by factor Xa levels
longer half lives- give one or twice daily
protamine is only partially effective in reversing lmwh
protamine not effective for fondaparinux
lmwh contraindicated for HIT+
bivalirudin (angiomax)
shortest half life and is the drug of choice for renal and hepatic dysfunction.
(argatroban (a DTI) will prolong the inr the most which can complicate transition to warfarin)
ventilatory response vs renal response
ventilatory response occurs in minutes renal response can slowly provide nearly complete restoration of the pH but it can take days.
bicarbonate buffer system
co2 combines with water- makes carbonic acid- hydrogen and bicarb.
