2018 Feb FRCA Flashcards
1.1 Define Sedation
Sedation, also known as “monitored anesthesia care”,
is a continuum
ranging from minimally impaired conciouesness to unconciousness
Medications are given,
usually through an IV,
to make the patient feel drowsy and relaxed.
Different levels of sedation are possible, depending on the type of procedure and the patient’s preference.
1.2 What are the ASA Classifications of Sedation?
- Minimal Sedation
Anxiolysis - Moderate Sedation/Analgesia
(“Conscious Sedation”) - Deep Sedation/
Analgesia - General Anesthesia
What are the clinical criteria at each level?
- Responsiveness
- Airway
- Spontaneous Ventilation
- Cardiovascular Function
Responsiveness
- Normal response to verbal stimulation
- Purposeful** response
to verbal or tactile
stimulation - Purposeful** response
following repeated
or painful stimulation - Unarousable even
with painful stimulus
Airway
Unaffected
No intervention required
Intervention may be required
Intervention often require
Spontaneous Ventilation
Unaffected
Adequate
May be inadequate
Frequently inadequate
Cardiovascular
Function
Unaffected
Usually maintained
Usually maintained
May be impaired
1.4 Dissociative Sedation
Trancelike
cataleptic state
profound analgesia and amnesia
Maintaining protective airway reflex
spontaneous resp
CV stability
Between moderate and deep
1.5.a
What is the mechanism of action of midazolam?
Midazolam is a γ-aminobutyric acid A (GABAA) receptor agonist
This results in the sedative, hypnotic (sleep-inducing), anxiolytic (anti-anxiety), anticonvulsant, and muscle relaxant properties for which the drugs are prescribed.
1.5.b What is it’s time to peak onset
and elimination half life
IV Onset ~2 min
Maximum effect is in about 5 to 10 minutes.
The elimination half-life of midazolam is between 1.5 - 2.5 hours
What adverse errors can occur with sedation and causes of same
Dose
Inappropriate dose given - causing over sedation
Respiratory compromise
Certain agents - ie midazolam can affect respiratory effort - in extreme may require advanced resp support
HD compromise
Propofol can lead to decrease in CO / drop in SVR - may cause hypotension
Aspiration
Deeply sedated patient may lose protective airway reflexes and are at risk of aspiration of gastric contents
Delirium
Increased risk of delirium in older age group
Agitation / hyperactivity
Midazolam can cause a paradoxical hyperactivity in some patients
2.1 Define counter -pulsation
Counter-pulsation is a term that describes
balloon inflation in diastole
and deflation in early systole.
2.2 Physiological mechanism of IABPs
Inflation: >> Forces blood proximally, increasing the pressure within the proximal aorta compared to the left ventricle, thus improving perfusion of coronary arteries, increasing oxygen delivery.
> > Forces blood distally,
thus augmenting the apparent
output from the left ventricle.
> > Augments Windkessel effect.
Deflation:
» Decrease in afterload reduces myocardial wall stress during systole, thus
reducing myocardial oxygen demand.
2.3 Indications for IABP
Indications:
» Cardiogenic shock due to myocardial infarction if revascularisation planned.
> > Acute mitral regurgitation or ventricular septal defect due to acute myocardial infarction.
> > Refractory ventricular arrhythmias whilst awaiting definitive treatment.
> > Refractory unstable angina if treatment option available.
> > Refractory left ventricular failure if destination treatment planned.
> > Perioperative support for high-risk coronary artery bypass surgery.
> > Perioperative support for high-risk non-cardiac surgery
2.3 ContraIndications IABP
Contraindications:
Absolute
» Aortic regurgitation, dissection or stent.
> > Chronic end-stage heart disease with no further possible intervention.
Relative
> > Uncontrolled sepsis.
> > Abdominal aortic aneurysm, severe peripheral vascular disease or arterial reconstruction surgery.
> > Uncontrolled bleeding disorder.
> > Tachyarrhythmias.
2.4 List the possible complications
of an IABP. (6 marks)
> > Haemodynamic compromise due to poor timing of counter pulsation or malposition.
> > Limb, spinal cord or visceral (especially renal) ischaemia.
> > Compartment syndrome.
> > Aortic dissection.
> > Vascular injury causing bleeding, haematoma, false
aneurysm, arteriovenous fistula.
> > Cardiac tamponade.
> > Thromboembolism.
> > Thrombocytopaenia and haemolysis.
> > Infection.
> > Balloon rupture resulting in gas embolus.
3.1 Abdominal Compartment Syndrome
Define Intra Abdominal Hypertension
Intra-abdominal hypertension is a sustained or repeated IAP > than 12 mmHg
Define Abdominal Compartment Syndrome
Abdominal compartment syndrome is defined
as a sustained IAP greater than 20 mmHg
with a new organ dysfunction or
failure regardless of
abdominal perfusion pressure (APP)
3.3 Systemic effects of Abdominal Compartment Syndrome
CVS
Resp
Systemic effects of intra-abdominal hypertension
Cardiovascular effects of increased intra-abdominal pressure
1 Reduced venous return
2 Reduced cardiac output
3 Increased systemic vascular resistance
Pulmonary effects of increased intra-abdominal pressure:
1 Reduced PaO2/FiO2 ratio
2 Hypercarbia
3 Increased inspiratory pressure
3.3 Systemic effects of Abdominal Compartment Syndrome
Renal
CNS
GI
Renal effects of increased intra-abdominal pressure
1 Reduced glomerular filtration
2 Oliguria
CNS
Acute elevations of IAP may also increase intracranial pressure.
Gastrointestinal effects
Gut mucosal ischaemia, independent of changes in cardiac output,
occurs with an increase in IAP
3.3 - Pathphpysiology of AC
Pathophysiology
Chronic increase in intra-abdominal volume
can be compensated by changes
in the abdominal wall compliance.
In situations where the volume of the
abdominal contents increases rapidly or the
abdominal wall compliance reduces,
IAP increases.
Initially, the abdominal wall distends but, eventually,
a critical volume is reached and the compartment syndrome occurs.
Factors such as the rapidity of the increase and the presence of muscle spasm secondary to peritonism can affect the critical volume.
A rapid increase in the volume of the
abdominal contents occurs in many situations such
as haemorrhage or blunt abdominal trauma.
Also, capillary leak, interstitial oedema and disseminated intravascular coagulation may result in ascites, ileus and bowel wall oedema.
Gas, whether inside or outside the bowel, faeces and foreign bodies, e.g
. surgical packs, can all contribute to the
increase in pressure.
3.4
Anaesthetic considerations for patient coming to theatre for treatment of
Abdominal Compartment Syndrome
Anaesthetic management for abdominal decompression
1 Severe instability may preclude the transport of the patient to the operating theatre.
2 Although concerns have been raised about the potential difficulty of managing haemorrhagic complications,
many centres now routinely perform decompression within the Intensive Care Unit.
3 The pharmacokinetics and pharmacodynamics of anaesthetic agents may be altered in the presence of intra-abdominal hypertension.
4 Patients with ACS may be more sensitive to the cardio- vascular depressant effects of anaesthetic agents; changes in organ blood flow and altered volumes of distribution may increase their potency
3.4 Anaesthetic considerations for patient coming to theatre for treatment of
Abdominal Compartment Syndrome
The abdominal decompression syndrome
During abdominal decompression, three potentially dangerous physiological changes occur.
- A sudden drop in systemic vascular resistance
Although the use of epinephrine has been advocated inthis situation, most centres use an approach of aggressive preloading with fluids.
- A fall in intrathoracic pressure Many patients with ACS require ventilatory pressures of
approximately 50 cm H 2 O together with high levels of
PEEP.
Sudden decreases in intrathoracic pressure may
result in the administration of inappropriately large tidal
volumes and alveolar over-distension, producing both
barotrauma and volutrauma.
3 The washout of toxic products
Ischaemic metabolism causes accumulation of lactic acid, adenosine and potassium within the tissues. Following the restoration of circulation, these products rapidly return to the general circulation producing arrhythmia, myocardial depression and vasodilatation.
Asystolic cardiac arrest has been reported in up to 25% of patients undergoing decompressive laparotomy and is reported as being universally fatal.
The decompression syndrome may be ameliorated by the prior administration of a ‘reperfusion cocktail’.
This consists of 2l of 0.45% normal saline containing 50 g of mannitol and 50 milliequivalents of sodium bicarbonate.
3.4 Anaesthetic considerations for patient coming to theatre for treatment of
Abdominal Compartment Syndrome
Management after decompression
Closure of abdomen after decompression may not be possible for several days because of bowel oedema.
Fluid requirements in a patient with an open abdomen are massively increased (up to 10–20 l day1 ).
Hypothermia remains a risk and core temperature monitoring is required.
Despite decompression, ACS may recur.
Therefore, intravesical pressure monitoring should continue after decompression.
Enteral feeding is well tolerated by patients with an open abdomen and may speed the resolution of gut oedema.
Reperfusion injury to the gut and kidneys may also occur after delayed decompression with subsequent development of multi-organ dysfunction
4.1 3 Chemicals in Cigarettes
- Nicotine
- Carbon Monoxide
- Arsenic
- Ammonia
- Methanol
4.2 a Cardiovascular system effects of cigarette smoking
Cardiovascular
- Hypertension Peri-operative ischaemia
- Ischaemic heart disease Myocardial infarction
- Hypercoagulation Thrombosis
Worst outcome after coronary artery bypass graft surgery and vascular
surgery
Smokers are prone to hypertension, ischaemic heart disease, cerebrovascular disease and heart failure.
All of these are risk factors for postoperative cardiovascular morbidity and mortality.
Smokers also have higher resting plasma catecholamine concentrations than
non-smokers and an exaggerated sympathetic response to desflurane anaesthesia.
The electrocardiograms of smokers are more
likely to show ST segment depression during general anaesthesia, implying impaired coronary perfusion that, together with hypoxaemic effects of COHb,
reduces myocardial O2 supply during the
peri-operative period, especially when the demand is increased.
This phenomenon is reflected in the reduced time of onset of exercise-induced angina and the increased incidence of ventricular dysrhythmia and dysfunction in the awake subject with COHb values
of as little as 4.5–6%.
Myocardial ischaemia itself promotes carboxymyoglobin formation reducing myocardial O2
supply still further,
which, together with the effect of CO on cytochrome oxidase
may explain the known negative inotropic effect of CO.
4.2 b Respiratory system effects of cigarette smoking
Respiratory
Decreased oxygen carriage
Hypoxaemia
Irritable upper airways
Laryngospasm
Irritable lower airways
Bronchospasm
Depressed ciliary function
Retained secretions and
infection
Decreased FEV 1
Increased closing capacity
4.2 b - O2 Carriage detail
Oxygen carriage in blood
Oxygen and haemoglobin (Hb) interact in a characteristic fashion to give the well-known
oxygen–haemoglobin dissociation curve.
Under normal circumstances, after blood has passed
through the lungs, Hb is almost fully saturated
with O2 even when the concentration of O2
in the lungs (and, therefore, in arterial blood) is slightly
reduced.
In tissues, where pH is lower and CO2
concentration and temperature are greater, the
characteristics of Hb favour O2 release.
In smokers, several changes occur. Blood con-
centration of carbon monoxide (CO) is increased
to as much as 10% (normal 2%). This has two
effects on O2 carriage.
First, Hb has 250 times more affinity for
CO than for O2, so the total amount of Hb available for O2 carriage is markedly decreased.
Secondly, CO shifts the dissociation
curve to the left, which reduces the ability of Hb to release O2.
To make matters worse, CO also inhibits cytochrome oxidase, the enzyme that is needed for the final oxygen dependent synthesis of ATP in the mitochondria.
This compromise of O2 delivery
makes the events that ordinarily tend to reduce O
2 saturation (i.e. induction of anaesthesia, intra- and peri-operative critical incidents, postoperative hypoventilation and atelectasis)
more threatening for smokers.
With values of carboxyhaemoglobin (COHb)
approaching 10–15%, the smoker may already be near the point on the dissociation curve where any further reduction in PaO2 will lead to rapid desaturation.
The light absorbance of COHb is nearly the same as that of oxygenated Hb at the wavelengths used by bedside pulse oximeters.
Thus, they cannot differentiate COHb from oxyhaemoglobin and over-estimate O 2
saturation.
Just as reliance on oximeters in othersituations of severe CO excess (e.g. house fires) is dangerous, an
apparently normal reading can lead to a false sense of security in heavy smokers
4.2 b Airways
Smokers have ‘irritable’ upper airways and this increases the tendency for breath-holding and laryngospasm at induction of anaesthesia.
Although usually a minor inconvenience, these can be life threatening.
The commonly used volatile anaesthetics are bron-
chodilators, although some such as desflurane have a direct irritant effect on the airways.
Any bronchodilating effects of volatile
anaesthetics are obviously lost when anaesthesia ends.
Lower airway reactivity is also increased in smokers and
mucociliary transport impaired. The forced expiratory volume at 1 s (FEV 1 )
declines in smokers at a rate of around 60 ml yr–1
compared with 20 ml yr–1 in non-smokers.
Also, the closing
capacity ( i.e. lung volume at which airways collapse and trap air) is increased.
Smokers have a greater degree of shunt under
anaesthesia, even when changes in functional residual capacity and closing capacity are accounted for. This is presumably due to altered regional pulmonary mechanics.
These changes, in
addition to the changes in respiratory mechanics that occur with both surgery and anaesthesia itself, make hypoxia more likely both during and after operation.
The relative risk of postoperative pulmonary complications in smokers versus non-smokers is around six.
The absolute values vary between studies (5–25%
non-smokers, 22–57% current smokers). Passive smoking has recently been identified in kids
4.3 Stopping smoking
Years Reduction in lung cancer, chronic obstructive pulmonary disease, ischaemic heart disease, cerebrovascular disease
GP, society, government
5–6 months
Reduction of postoperative complications
GP, surgeon
1 month
Possible increased risk of postoperative pulmonary complications
GP, surgeon
2–10 days Improvements in upper airway reactivity Anaesthetist, surgeon, nurses in pre- admission clinics
12–24 h
Clearance of carbon monoxide
Anaesthetist, surgeon, nurses
5.1 Joints involved in rheumatoid arthritis and implications of these on anaesthesia
RhA is characterised by a chronic symmetrical polyarthritis of (mainly) peripheral joints, especially the fingers, elbows, ankles, but also more proximal joints, shoulders, neck, knees, hips.
Any of these may be relevant to anaesthesia as they may be the focus of an operation and so dictate the choices of anaesthetic technique.
Also, the involvement of any joint may make positioning for regional anaesthesia problematic.
> > Temporomandibular joint:
may impact on mouth opening and, hence,
ease of intubation.
May necessitate fibreoptic intubation.
> > Cricoarytenoid joint fixation:
may cause preoperative hoarseness.
Minimal oedema may therefore cause airway obstruction postoperatively.
>> Atlantoaxial subluxation: assess range of movement and symptoms whilst the patient is awake. Excessive movement (such as with airway management) can cause cord compression. May necessitate fibreoptic intubation.
> > Cervical ankylosis:
causing limited neck extension, difficult airway.
> > Costovertebral and costotransverse joints:
restrictive lung defect.
> > Small joints of hand: limited ability to manage PCA.
5.2 Which systemic features of RhA may be elicited during preoperative assessment? (10 marks)
A + B
Airway:
» Difficult airway for reasons detailed in part (a).
Respiratory:
» Fibrosing alveolitis causing restrictive defect.
> > Pleurisy with effusion.
> > Nodules.
> > Costochondral disease causing
reduced chest wall compliance.
5.2 Which systemic features of RhA may be elicited during preoperative assessment? (10 marks)
CVS
Cardiovascular:
» Pericarditis and pericardial effusions, rarely leading to tamponade, usually
gradually restrictive and requiring pericardectomy.
» Rheumatoid nodules in any layer of the heart, damaging valve function,
causing conduction defects, rarely congestive cardiac failure.
» Increased atherosclerosis and coronary artery disease
5.2 Which systemic features of RhA may be elicited during preoperative assessment? (10 marks)
Neurological
Neurological:
» Peripheral neuropathy due to:
• Peripheral nerve entrapment
(carpal tunnel, ulnar, lateral popliteal).
- Mononeuritis multiplex due to vasculitis.
- Drug treatment.
> > Autonomic dysfunction:
blood pressure and heart rate lability,
gastric paresis.
> > Compression of nerve roots
due to spinal involvement
(especially cervical spine).
5.2 Which systemic features of RhA may be elicited during preoperative assessment? (10 marks)
Endocrine
Chronic steroid use:
compromises glucose tolerance, may ultimately
result in diabetes.
Consider the need for perioperative replacement, effect on immune function, skin fragility.
5.2 Which systemic features of RhA may be elicited during preoperative assessment? (10 marks)
Haematology:
Haematology:
» Normochromic, normocytic anaemia of chronic disease.
> > Iron deficiency anaemia due to chronic gastrointestinal losses with NSAID treatment.
> > Thrombocytosis due to inflammation.
> > Bone marrow depression due to disease-modifying anti-rheumatic drugs (DMARDs).
5.2 Which systemic features of RhA may be elicited during preoperative assessment? (10 marks)
Immune, infection:
Cutaneoumusculoskeletal:
Immune, infection:
» Increased susceptibility to infection
due to DMARDs or TNF inhibitors.
Cutaneoumusculoskeletal:
» Friable skin (due to chronic steroid loss), risk of damage with dressings for cannulae, handling.
> > Fixed joint deformities – care with positioning
5.2 Which systemic features of RhA may be elicited during preoperative assessment? (10 marks)
Renal
Renal:
» Chronic inflammation may cause amyloidosis.
> > Drug treatments may cause CKD.
> > CKD affects metabolism of drugs used perioperatively.
Hepatic:
» Methotrexate may cause liver cirrhosis,
which will impact on drug metabolism.
c) Outline the preoperative investigations that are specifically indicated in this patient and the derangements that each may show. (6 marks)
Full blood count
Full blood count:
» Neutropaenia: should not continue with elective surgery if the patient is currently neutropaenic.
> > Anaemia: further investigations may be indicated to determine the underlying cause.
Efforts should be made to correct
anaemia before major surgery.
> > Platelet level: impacts on
feasibility of neuraxial technique.
c) Outline the preoperative investigations that are specifically indicated in this patient and the derangements that each may show. (6 marks)
Renal function:
Renal function:
> > Elevated urea, creatinine, reduced glomerular filtration rate – chronic kidney disease may occur due to drugs or the disease itself.
Liver function tests:
» Transaminases and alkaline phosphatase
may rise in active disease.
> > Derangements in all liver function tests may occur due to liver cirrhosis caused by methotrexate.
c) Outline the preoperative investigations that are specifically indicated in this patient and the derangements that each may show. (6 marks)
ECG
CXR
ECG:
» Conduction disorders.
» Left ventricular hypertrophy.
Chest x-ray:
» Indicated if there are respiratory symptoms. May reveal pleural effusions, infection, fibrotic lung disease, nodulosis.
c) Outline the preoperative investigations that are specifically indicated in this patient and the derangements that each may show. (6 marks
PFTS
» If respiratory symptoms.
Usually reveals a restrictive pattern.
Echocardiogram:
» If a murmur is noted or there are symptoms or signs to suggest poor cardiac function.
Regurgitant valves may be due
to nodulosis or pericardial fibrosis