Critical Care Kanani II Flashcards
What are the risk factors for post-operative atelectasis?
Upper abdominal and thoracic surgery: reduced lung expansion from pain and diaphragmatic splinting leads to retention of secretions and distal airways collapse
- Body mass index of
What is continuous positive airway pressure (CPAP) ventilation, and what are its physiological effects
on the respiratory system?
CPAP is an oxygen delivery system that relies on a closed cir- cuit to provide positive airways pressure throughout all phases of spontaneous ventilation. The circuit can be attached to a tracheal tube or to a tight fitting mask, which means that it may be used on the ward under supervision. Some of the physiological methods by which it improves alveolar ventilation are:
- Recruitment of collapsed alveoli, and prevention of their collapse on expiration
- Increase in the functional residual capacity (FRC): in the elderly and critically ill, collapse of the airways occurs close to the volume of the FRC. By increasing the FRC, atelectasis can be avoided or overcome
- Increased lung compliance, reducing the work of breathing
- Consequently the V/Q ratio increases, improving oxygenation
What are the disadvantages of CPAP ventilation?
The tight fitting mask is uncomfortable and may be poorly tolerated
- Causes gastric dilatation due to swallowed air
- Barotrauma to the alveoli due to high pressures (more common in neonates)
Define the blood pressure.
Blood pressure is defined as the product of the cardiac out- put and the systemic vascular resistance. The cardiac output is the product of the heart rate and stroke volume.
In which ways can blood pressure be measured?
Blood pressure can be measured non-invasively with a sphyg- momanometer, or invasively by direct cannulation of a periph- eral artery. This latter method gives a continuous waveform trace after attachment to an electronic pressure transducer.
The ‘dicrotic notch’ is a momentary rise in the arterial pressure trace following closure of the aortic valve.
How is the mean blood pressure calculated?
The area beneath the arterial pressure wave tracing represents the mean arterial pressure. For the purposes of simplicity, it may be calculated by the formula
Pd + (Ps = Pd)/3
where Pd = diastolic pressure and Ps = systolic pressure.
What are the complications of arterial lines, and what are the contra-indications to their insertion?
The complications include
- Most commonly:
- Haematoma formation
- Digital ischaemia due to vascular injury or accidental
injection of drugs
- Less commonly:
- Infection
- Pseudoaneurysm formation
- Arteriovenous fistula formation
- Exsanguination from a disconnected line
It is contra-indicated in those with digital vasculitis, and in those patients who are going to have the artery of that side harvested as a conduit for bypass surgery.
What is meant by the term ‘swing in the arterial line’ during continuous measurements, and what is its significance?
This term refers to a variation of the amplitude in the arterial tracing with the respiratory cycle. It is an indicator that the patient is underfilled and requires more fluid resuscitation.
How does the arterial pressure at the radial artery compare to that at the aortic root, what accounts for this difference?
Both the pressure values and waveform change at different levels of the circulation. In the radial artery, the systolic pressure is about 10mmHg higher and the diastolic pressure about 10 mmHg lower than in the aortic root. Consequently, although the pulse pressure is higher in the radial artery, the mean arte- rial pressure is about 5 mmHg lower than in the aortic root.
These differences are, in part, due to changes in wall stiffness along the arterial tree, and its consequent effects on the trans- mission of the pulse wave along the vessel.
How does the arterial pressure waveform differ with diseases of the aortic valve?
Aortic stenosis: Anacrotic pulse – slow to rise and of low
amplitude
- Aortic incompetence: Waterhammer pulse – rapid rise and decline, attaining high amplitude
- Mixed aortic valve disease: Pulsus bisferiens – a large amplitude pulse with a ‘double peak’, often felt as a double pulse at the brachial artery
What is pulsus paradoxus?
Pulsus paradoxus is an exaggerated (10mmHg) reduction of the arterial pressure brought on by inspiration, and may be seen in cardiac tamponade. The normal increase in the venous return brought on by inspiration coupled with a tight pericardial space leads to a reduction of the left ventricular end diastolic volume, and hence, stroke volume.
What is pulsus alterans?
Pulsus alterans is a random variation in the amplitude of the arterial pressure tracing with each cardiac cycle, and is seen with left ventricular failure.
What blood products do you know of other than red cells?
What blood products do you know of other than red cells? The other major blood products are: The other major blood products are - Plasma-derived - Fresh frozen plasma (FFP) - Human albumin solution - Immunoglobulins - Individual factor concentrates, e.g. factors VII,VIII, IX, X, prothrombin complex, antithrombin III - Cryoprecipitate Note that FFP may be fractionated into the products listed below it. - Platelet concentrates
How are platelets stored once collected?
Platelets do not function at low temperatures, so that once collected, they are stored at room temperature of 20–24°C on a special agitator.
How many platelets are obtained from each
donation?
Each platelet donation contains 55 x 109 platelets. When pooled together to form an adult dose, about 240 x 109 platelets can be obtained.
