Calculate cardiac compliance
change in end-diastolic volume (ΔEDV)/change in end-diastolic pressure (ΔEDP)
When is end-diastolic pressure not representative of preload?
when ventricular compliance is abnormal
what are the most common causes of decrease in ventricular compliance? (2)
ventricular hypertrophy and ischemic heart disease
define cardiac afterload
in the intact heart, afterload force is equal to the peak tension in the ventricle during systole
how is ventricular tension calculated?
T = Pr, P = pressure at the end of systole, r = radius of the ventricle at the end of diastole
Effects of negative thoracic pressure on ventricular function
impedes ventricular emptying by opposing contraction during systole
define pulsus paradoxus
effect responsible for the exaggerated transient decrease in systolic blood pressure in excess of 15mmHg occurring during spontaneous inspiration
What is the effect of positive-pressure mechanical ventilation on arterial blood pressure?
increases, increasing stroke volume and cardiac output
What is the principal determinant of ventricular afterload?
Impedence, made up of compliance (elasticity of larger arteries) and resistance (opposition to steady flow in smaller arteries/arterioles)
define the formula for vascular resistance
Resistance (R) = Pressure differential (ΔP)/rate of blood flow (Q)
define the formula for systemic vascular resistance
Systemic vascular resistance (SVR) = mean systemic arterial pressure (SAP) - mean right atrial pressure (RAP)/cardiac output (CO)
define the formula for pulmonary vascular resistance under normal circumstances
Pulmonary vascular resistance (PVR) = mean pulmonary artery pressure (PAP) - mean left arterial pressure (LAP)/cardiac output (CO)
How is afterload measured/calculated indirectly?
Changes in the slow of ventricular function is used
What outside factors (2) should be considered when measuring afterload indirectly?
Ventricular compliance and myocardial contractility
What is the standard measure of contractility?
Ventricular pressure acceleration can be measured during cardiac catheterization by measuring the time from the onset of systole to the opening of the aortic valve
When does vascular compression become a problem in patients on positive-pressure mechanical ventilation?
When alveolar pressure exceeds hydrostatic pressure in pulmonary capillaries
Define the formula for pulmonary vascular resistance when the alveolar pressure exceeds average left atrial pressure
PVR = mean pulmonary artery pressure (PAP) - alveolar pressure (Palv)/CO
What is the principal determinant of whole blood viscosity?
Concentration of erythrocytes (hematocrit)
What is normal average hematocrit?
45%
What is the ratio of the viscosity of blood to plasma?
3:1
Describe changes that occur in flow as blood passes through capillaries smaller than 0.3mm
shear thinning: viscosity decreases and velocity increases (plasma > erythrocytes)
Calculate arterial O2 content
1.34 x Hb x ratio of arterial oxygenated hemoglobin to total hemoglobin (SaO2)
What is the principal determinant of the oxygen content of the blood?
Hemoglobin concentration
What measure should be used to evaluate the efficiency of gas exchange in the lungs?
PaO2
Given the amount of oxygen stored in the AV system, how long can aerobic metabolism be maintained just from stored oxygen?
3-4 minutes
What is the maximal oxygen extraction from systemic capillaries?
40-50%
What ratio of oxygen delivery rate (DO2) to oxygen dissociation rate(VO2) is required to avoid anaerobic metabolism?
DO2:VO2 = 4:1
What are imidazole groups?
They buffer hemoglobin and are effective in the pH range 6-8
What is the buffer range of bicarbonate, why is this important?
5.1-7.1, this is important because hemoglobin is a more effective buffer than bicarbonate
What is the name for the increase in CO2 binding and buffering affinity that occurs after desaturation?
The Haldane effect
What is the most frequently isolated bacteria on the hands of ICU personnel?
Staph epidermidis
What is the most important consideration in using iodine as a germicide?
It must be left in contact with the skin for a few minutes
What is the most effective germ prevention method for C. Difficile?
Gloved hands, hand washing, no antiseptics work
Sterile or non-sterile gloves: central venous catheterization
sterile
Sterile or non-sterile gloves: peripheral venous catheterization
nonsterile, as long as the hands don’t touch the catheter
Sterile or non-sterile gloves: peripherally inserted central catheter (PICC)
sterile
Sterile or non-sterile gloves: arterial catheterization
sterile
Sterile or non-sterile gloves: closed space drain placement
sterile
Sterile or non-sterile gloves: insertion of epidural catheter
sterile
Surgical mask or Negative pressure isolation: Hemophilus influenza (type b) epiglottitis, pneumonia or meningitis
surgical mask
Surgical mask or Negative pressure isolation: mycobacterium tuberculosis (pulmonary or laryngeal TB)
negative-pressure isolation
Surgical mask or Negative pressure isolation: Neisseria meningitides pneumonia or meningitis
surgical mask
Surgical mask or Negative pressure isolation: measles
negative-pressure isolation
Surgical mask or Negative pressure isolation: diphtheria (pharyngeal)
surgical mask
Surgical mask or Negative pressure isolation: respiratory mycoplasma
surgical mask
Surgical mask or Negative pressure isolation: Varicella or disseminated zoster
negative-pressure isolation
Surgical mask or Negative pressure isolation: group A strep pharyngitis or pneumonia
surgical mask
Surgical mask or Negative pressure isolation: viral respiratory infections
surgical mask
What is the average blood exchange of a puncture wound with a hollow needle?
One microliter
What is the risk of HIV seroconversion from a single needlestick?
0.30%
What is the risk of HIV seroconversion from a single exposure of broken skin or mucous membranes?
0.09%
What is the follow up protocol after Hepatitis B vaccination?
Serum anti-HBs level should be measured 2 months afterwards. If it is <10mIU/mL, the 3-dose series should be repeated.
What is the risk of HCV seroconversion from a single needlestick?
1.80%
What is the protocol for follow up after confirmed HCV needlestick injury?
Serial testing monthly for 6 months.