Fiser Chapter 16 CRITICAL CARE Flashcards
Normal CO
4-8 L/min
Normal CI
2.5-4 L/min/m^2
Normal SVR
800-1400
Normal PCWP
11 +/- 4 (7-15)
Normal CVP
7 +/- 2
Normal PAP
25/10
Normal SvO2 (mixed venous O2 sat)
75
MAP equation
MAP = CO x SVR
CI equation
CI = CO/BSA
Blood flow to organs
25% kidney
15% brain
5% heart
EF equation
SV/LVEDV
(LVEDV-LVESV)/LVEDV
Anrep effect
automatic increase in contractility 2/2 increased afterload
Bowditch effect
automatic increase in contractility 2/2 increased HR
CaO2 (arterial O2 content) equation
CaO2 = Hgb x 1.34 x O2 sat + (pO2 x 0.003)
O2 delivery equation
CO x CaO2 x 10
VO2 (O2 consumption) equation
VO2 = CO x (CaO2 - CvO2)
Normal O2 delivery-to-consumption ration 5:1
CO increases to keep this constant
O2 consumption is usually supply independent
Right shift O2-Hgb dissociation curve causes (increased O2 unloading)
CADET
Increased CO2, ATP production, acidosis, 2,3-DPG production, elevation, temperature
Normal p50 (O2 at which 50% of O2 receptors saturated) = 27 mm Hg
Causes of increased SvO2 (saturation of venous blood)
Normally 75%
Increased in shunt or decreased O2 extraction (sepsis, cirrhosis, CN tox, hyperbaric O2, hypothermia, paralysis, coma, sedation)
Causes of decreased SvO2 (saturation of venous blood)
Normally 75%
Decreased in increased O2 extraction or decreased O2 delivery (decreased O2 sat, decreasedCO, malignant hyperthermia)
Wedge may be thrown off by
Pulm HTN Aortic regurgitation Mitral stenosis Mitral regurgitation High PEEP Poor LV compliance
Swan-Ganz cath placement
Zone III (lower lung)
R SCV 45 cm L SCV 55 cm
R IJ 50 cm L IJ 60 cm
PVR can be measured only with Swan-Ganz (not Echo)
Wedge pressure should be measured at end-expiration
What do you do if there is hemoptysis after flushing Swan-Ganz cath?
Increase PEEP to tamponade pulmonary artery bleed
Mainstem intubate non-affected side
Fogarty balloon down mainstem on affected side
May need thoracotomy and lobectomy
What are the relative contraindications to Swan-Ganz cath?
Previous pneumonectomy
Left bundle branch block
Primary determinants of myocardial O2 consumption
Ventricular wall tension and HR
Increase can lead to MI
Normal alveolar-arterial gradient
10-15 mm Hg in normal nonventilated patient
What blood has the lowest venous saturation?
Coronary sinus blood (30%)
Shock definition
Inadequate tissue oxygenation
Adrenal insufficiency MCC
Withdrawal of exogenous steroids
Adrenal insufficiency manifestations
CV collapse, unresponsive to fluids and pressors
nausea, emesis, abdominal pain, fever, lethargy, decreased glucose, hyperkalemia
Tx: dexamethasone
Steroid potency
1x cortisone, hydrocortisone
5x prednisone, prednisolone, methylprednisolone
30x dexamethasone
Neurogenic shock symptoms and treatment
Loss of sympathetic tone
Spine or head injury
Decreased HR, BP, warm skin
Tx: Give volume first, then phenylephrine
Hemorrhagic shock initial alteration
Increased diastolic pressure
Cardiac tamponade mechanism of hypotension
Decreased ventricular filling
Echo: impaired diastolic filling of RA
Beck’s triad
Hypotension, JVD, muffled heart sounds
Cardiac tamponade
Cardiac tamponade tx
Fluid resuscitation
Pericardial window or pericardiocentesis
Early sepsis triad
Hyperventilation
Confusion
Hypotension
Blood glucose in sepsis
Hyperglycemia often occurs just before clinically septic
Early GN sepsis: increased glucose, decreased insulin (impaired utilization)
Late GN sepsis: increased glucose and insulin (insulin resistence)
Hypovolemia neurohormonal response
Rapid: adrenergic release -> vasoconstriction and increased cardiac activity
Sustained: RAS -> renin from kidney -> vasoconstriction and water resorption; ADH from pituitary -> water reabroprtion; ACTH from pituitary -> cortisol
Sudan red stain
May show fat in sputum and urine in fat embolism
Where do most PEs arise from?
Iliofemoral region
If PE patient is in shock despite massive pressors and inotropes?
After heparin and Coumadin, consider open or percutaneous (suction catheter) embolectomy
Air emboli tx
Trendelenburg, role to left (keeps air in RV and RA), then aspirate air out with central line or PA catheter to RA/RV
IABP mechanism
- Inflates on T wave (diastole): improves diastolic BP, improves diastolic coronary perfusion
- Deflates on P wave (systole): decreases afterload
IABP contraindication
Aortic regurgitation
IABP catheter location
Just distal to L subclavian (1-2 cm below top of arch)
IABP uses
Cardiogenic shock after CABG or MI
Refractory angina awaiting revasc
Alpha-1 receptor
Vascular smooth muscle constriction
Gluconeogenesis and glycogenolysis
Alpha-2 receptor
Venous smooth muscle constriction
Beta-1 receptor
Myocardial contraction and rate
Beta-2 receptor
- Relaxes bronchial smooth muscle
- Relaxes vascular smooth muscle
- Increases insulin, glucagon, and renin
Dopamine receptors
Relax renal and splanchnic smooth muscle
Dobutamine MoA
Beta-1: increases contractility mostly; tachycardia with higher doses
Milrinone MoA
Phosphodiesterase inhibitor: increases cAMP -> increased Ca flux and myocardial contractility; also vascular smooth muscle relaxation and pulmonary vasodilation
Phenylephrine MoA
Alpha-1 vasoconstriction
Norepinephrine MoA
Low dose: beta-1 increased contractility
High dose alpha-1 and alpha-2
Potent splanchnic vasoconstrictor
Epinephrine MoA
Low dose beta-1 and beta-2 increased contractility and vasodilation, but can decrease BP
High dose alpha-1 and alpha-2 vasoconstriction; increased cardiac ectopic pacer activity and myocardial O2 demand
Isoproterenol MoA
Beta-1 and beta-2 increased HR and contractility, vasodilation
SE: Very arrhythmogenic; increases heart metabolic demand, may actually decrease BP
Vasopressin MoA
V1- receptor vasoconstriction of vascular smooth muscle
V-2 receptor intrarenal water reabsorption at collecting ducts; extrarenal mediates factor VIII and vWF release
Nipride MoA
arterial vasodilator
CN toxicity; can check thiocyanate levels and metabolic acidosis
CN toxicity treatment
Amyl nitrite, then sodium nitrite
Nitroglycerin MoA
Venodilation with decreased myocardial wall tension by decreasing preload; moderate coronary vasodilator
Hydralazine MoA
alpha-blocker, lowers BP
Dopamine MoA
Dopamine receptors (renal) Higher dose beta-adrenergic (heart contractility) Higher dose alpha-adrenergice (vasoconstriction and increase BP)
Lung compliance
Change in volume/
Change in pressure
decreased in ARDS, fibrosis, reperfusion injury, edema, atelectasis
PEEP
Alveoli recruitment -> improves FRC and compliance -> best way to improves oxygenation
Pressure support
Decreases work of breathing
Prevent O2 radical toxicity by what
Keep FiO2 = 60%
When do you get barotrauma?
Plateaus > 30, peaks >50
So decrease Tv and consider pressure control ventilation
Excessive PEEP complications
- Decreased RA filling
- Decreased CO
- Decreased renal blood flow
- Decreased urine output
- Increased pulmonary vascular resistance
High frequency ventilation use
Kids
TE fistula
Bronchopleural fistula
TLC
TLC = FVC + RV
FRC
FRC = ERV + RV
Lung volume after normal exhalation
- Decreased by atelectasis, ARDS, contusion/trauma
- Improved with PEEP
Dead space
Area of lung ventilated but not perfused; normally to level of bronchiole (150 mL)
Increases with: Drop in CO, PE, pulm HTN, ARDS, excessive PEEP; can lead to hypercapnia
ARDS MoA
Neutrophils; increased proteinaceous material; increased A-a gradient; increased pulmonary shunt
MCC pneumonia
Other: sepsis, multi-trauma, severe burns, pancreatitis, aspiration, DIC
ARDS criteria
Acute onset
Bilateral pulmonary infiltrates
PaO2/FiO2 = 300
Absence of heart failure (wedge < 18 mm Hg)
Aspiration, increased damage associated with what
pH < 2.5, volume > 0.4 cc/kg
Mendelson’s syndrome
chemical pneumonitis from aspiration of gastric secretions
Most frequent site of aspiration
superior segment of RLL
Fever, tachycardia, hypoxia in first 48hr postop
Atelectasis: collapse of alveoli resulting in reduced oxygenation
Increased in patients with COPD, upper abdominal surgery, obesity
Tx: IS, pain control, ambulation
What can throw off a pulse oximeter
Nail polish Dark skin Low-flow states Ambient light Anemia Vital dyes
Causes of pulmonary vasodilation?
PGE1 Prostacyclin (PGI2) Nitric oxide Bradykinin Alkalosis
Causes of pulmonary vasoconstriction?
Hypoxia Acidosis Histamine Serotonin TXA2
Causes of pulmonary shunting
Nitroprusside
Nitroglycerin
Nifedipine
MCC of postop renal failure
Intra-op hypotension
70% nephrons need to be damaged
FeNa
(urine Na/Cr) / (plasma Na/Cr)
Best test for azotemia
FeNa <1% in prerenal
FeNa >3% in parenchymal
Urine measurements in prerenal failure
Urine osmolarity >500 U/P osmolality >1.5 U/P creatinine >20 Urine sodium < 20 FeNa < 1%
Urine measurements in parenchymal failure
Urine osmolarity 250-350 U/P osmolality < 1.1 U/P creatinine < 10 Urine sodium > 40 FeNa > 3%
Oliguria tx
- Volume load (CVP 11-15)
- Diuresis trial
- HD
Dialysis indications
AEIOU: Acidosis Electrolytes (hyperkalemia) Ingestion (poisons) Overload Uremia (encephalopathy, coagulopathy)
CVVH compared to HD
Slower
Good for ill patients who cannot tolerate large colume shifts (septic shock)
Hct increases by 5-8 for each liter taken off
RAAS
- hypotension, hypernatremia (sensed by macula densa), beta-adrenergic stiulation, or hyperkalemia -> JG apparatus releases renin
- Renin converts Angiotensinogen (synthesized in liver) to ATI
- ACE (from lung) converts ATI to ATII
- ATII vasoconstricts and increases HR, contractility, glycogenolysis, gluconeogenesis; inhibits renin release
- ATII also causes aldosterone release from adrenal cortex -> DCT -> upregulating NaK ATPase on membrane -> water reabsorbtion, Na re-absorbed, K secreted
ANP
Atrial distention -> ANP release from atrial wall -> inhibits Na and water resorption in collecting ducts; also vasodilation
ADH
High osmolality -> posterior pituitary releases ADH -> water resorption in collecting ducts; also vasoconstrictor
Efferent limb of kidney
Controls GFR
DCT
where ATII acts to upregulate NaK ATPase and cause Na, water reabsorbtion and K secretion
Renal toxic drugs
NSAID: inhibits prostaglandin synthesis, causing renal arteriole vasoconstriction
Aminoglycosides: direct tubular injury
Myoglobin: direct tubular injury (Tx: alkalinize urine)
Contrast dyes: direct tubular injury (Tx: pre-hydration best; HCO3-, NAC)
SIRS most potent stimulus
Endotoxin (lipopolysaccharide - lipid A)
Major components: TNF-alpha and IL-1
Results in capillary leakage, microvascular thrombi, hypotension, end-organ dysfunction
SIRS definition
Temp > 38 or <36
HR > 90
RR > 20 or PaCO2 < 32
WBC >12 or <4
Shock definition
Arterial hypotension despite adequate volume resuscitation
Inadequate tissue oxygenation
Multi organ dysfunction definition
Progressive but reversible dysfunction of 2 or more organs arising from an acute disruption of normal homeostasis
Brain death preclusions
Temp <32 BP <90 Drugs (phenobarb, pentobarb, EtOH) Metabolic derangements (hyperglycemia, uremia) Desaturation with apnea test
Brain death definition
6-12 hours of:
- Unresponsive to pain
- Absent cold caloric oculovestibular reflexes
- Absent oculocephalic reflex (patient doesn’t track)
- No spontaneous respirations
- No corneal reflex
- No gag reflex
- Fixed and dilated pupils
- Positive apnea test
*Can still have deep tendon reflexes with brain death
Brain death on EEG or MRA
EEG: Electrical silence
MRA: No blood flow to brain
Apnea test
Pre-oxygenation, and CO2 should be normal prior
Catheter delivering O2 at 8L/min is placed at carina through ETT-Disconnect from vent for 10 minutes
Positive test meets brain death criteria: CO2 >60 or increase in CO2 by 20
Negative test and cannot declare brain death, so put back on vent: If BP drops <90, desaturates <85%, or spontaneous breathing occurs
Carbon monoxide poisoning
- Falsely normal oxygen saturation on pulse ox
- Binds Hgb directly, creates carboxyhemoglobin
- HA, nausea, confusion, coma, death
- Can usually correct with 100% oxygen on vent
- Abnormal carboxyhemoglobin >10% (smokers >20%)
Methemoglobinemia
- From nitrites such as Hurricaine spray
- Nitrites bind Hgb
- O2 sat reads 85%
- Tx: Methylene blue
Critical illness polyneuropathy
Motor > sensory neuropathy
Occurs with sepsis
Can lead to failure to wean from vent
Reperfusion injury
Xanthine oxidase: In endothelial cells, forms toxic oxygen radicals with reperfusion
XO also involved in the metabolism of purines and breakdown to uric acid
Most important mediator of reperfusion injury is PMNs
EtOH withdrawal
HTN, tachy, delirium, seizures after 48hr
Tx: thiamine, folate, B12, Mg, K, PRN lorazepam