Geriatric Anesthesia Flashcards
FRC Changes?
INCREASES
Susceptibility to stress & disease
Functional reserve can be measured for some organ systems (cardiac) but for others (hepatic/renal) more difficult to quantify.
Stochastic model
Stochastic model: random errors of protein synthesis accumulate
Cellular evidence of defects within mitochondrial DNA
Reduction in scavenging of free radicals
Non Stochastic, Biological clock or life pacemaker: neuroendocrine, immune focus
Individual rates of decline vary and decline in specific organ function varies.
Body changes with aging
Loss of lean body mass
Increased total body fat
Decreased metabolic rate
Decreased total body water
Decreased blood volume (20-30%)
T
Thermoregulation
Impair function of hypothalamus in elderly
Hypothermia last longer due to low metabolic rate
Hypothermia causes slower elimination of anesthetics and longer recovery
Shivering increases O2 consumption by 400% (hypoxia, acidosis and cardiac compromise)
Respiratory: dead space & MV
Increase in dead space requires increase in MV to maintain a normal PaCO2
Resp: compliance, elasticity, & RV
Lung compliance increases = Lungs are easier to inflate
Chest wall compliance DECREASES
Decreased Lung elasticity, promotes small airway collapse
Aged Lung is easy to inflate (high compliance) but low elasticity makes it harder to return to its original shape.
RV increases as a result
Other anatomical resp changes
Calcified joints
Flatten diaphragm
Increased AP diameter
Decreased intervertebral disc height
Decreased respiratory muscle strength
Decreased elastic recoil
WOB change?
THE WORK OF BREATHING INCREASES
Resp: hypercarbia and hypoxia
Decreased response to hypercarbia and hypoxia
Chemoreceptors
Chemoreceptors are less sensitive to changes in pH,PaCO2, and PaO2
Airway Reflexes
Decreased Protective airway reflexes
Increased aspiration risk
Airway tone and muscle strength
Decreased upper airway tone
Decreased respiratory muscle strength
Common Age related Anatomic and Physiologic Changes: Decreases
Decreased forced expiratory volume
Decreased resting arterial oxygen tension
Common age related anatomic and physiologic changes: increases
Increased residual volume and closing capacity
Increased Ventilation-perfusion mismatch
Increased alveolar-arterial gradient
Increased functional residual capacity
Lung changes with aging summary
Cardiac: compliance
Arterial and venous compliance decrease
Decreased myocardial compliance and impaired relaxation can cause diastolic dysfunction
Cardiac: arterial
Arterial = Increase SVR and afterload –> increased BP
Cardiac: venous
Venous = Changes in blood volume cause major changes in preload
Cardiac: filling pressures & atria
Heart requires higher pressures to fill and filling pressures overestimate volume
Atrial kick important to prime non-compliant ventricles
Cardiac: EF, eletrical changes
Ventricular hypertrophy reduces ventricular compliance and impairs relaxation and prolongs ejection time
Fibrosis of cardiac conduction system and loss of SA node tissue
Increased likelihood of atrial fibrillation, first degree heart block second degree HB and Sic sinus syndrome
Cardiac: BP and SV changes
Increased BP = reduced arterial compliance increases SVR
Increased pulse pressure = arterial stiffness increases systolic pressure more than diastolic pressure
Systolic function is unchanged
Diastolic function decreased = reduced compliance and increased wall stiffness impairs relaxation
Stroke volume decreases and decreased ability to increase SV reduces exercise tolerance
Cardiac: HR changes
Heart Rate decreases
Decreased responsiveness to catecholamine’s
Decreased ability to respond to hypotension, hypovolemia and hypoxia
Decreased CO, prolongs circulation time, reduced exercise tolerance and cardiac reserve
AFib
AF increases morbidity and mortality (Framingham Heart Study)
Women with AF are three times more likely to suffer stroke as women without
Men have a 2.5 times increased risk
All patients with AF are 3.5 times more likely to suffer symptoms of CHF
Cardiac Consequences
Loss of atrial synchrony
Irregular ventricular response
Impaired coronary blood flow
Loss of atrial kick in the setting of diastolic dysfunction can lead to a 20-50% decrease in cardiac output
Afib management
Preoperative patient presents with AF
Is the rhythm acute change or chronic
For chronic AF check rate control and coagulation status and proceed
New onset evaluate hemodynamic status and recommend cardiac workup rule out MI protocol and evaluate thrombus formation
Must evaluate the urgency of the procedure
Metabolic Equivalent (MET)
1 MET is equal to an oxygen consumption of 3.5ml/kg/min
Inability to achieve 4 METS is associated with increased perioperative risk of cardiac complications