Exam 1 Flashcards
Anaphylaxis
Clin features
Response?
Tx includes
The clinical features of anaphylaxis are cardiovascular collapse, bronchospasm, angio-oedema,
generalised oedema and cutaneous signs such as rash, erythema and urticaria.
The response to treatment may
depend on the severity of the reaction, however even severe anaphylaxis responds promptly to appropriate
treatment in most patients.
Anaphylaxis Initial Rx
Initial therapy includes:
Stop administration of suspected drug(s)
Give 100% oxygen and maintain the airway
Lay patient flat and elevate the legs
Give adrenaline:
IM0.5-1.0 mg
(0.5-1 ml of 1:1,000)
repeated every 10 minutes
IV 50- 100 mcg (0.5-1 ml of 1:10,000)
over 1 minute with titration of further doses.
In a patient with
cardiovascular collapse 0.5-1.0 mg may be required intravenously in divided doses by titration at a rate of 0.1 mg/minute until an adequate response is obtained
What is atmospheric pressure in various measures
1 atmosphere =
1 bar
760 mmHg = 76 cmHg
Hg has a relative density = 13.6 × H2O,
therefore 760 mmHg = 10.3 mH2O
15 lb/in2
DVT
What is it made up of
Is SCD a risk
What is Homans sign
The thrombus of a deep vein thrombosis (DVT) consists mainly of
red cells and fibrin (red thrombus).
Sickling in sickle cell crises leads to an increased blood viscosity which is associated with both arterial and venous thrombosis.
Homan’s sign is pain in the calf on dorsiflexion of the foot, and though present in DVT it also
occurs with other lesions of the calf.
PE most common with what DVT
Valve destruction causes what
Pulmonary embolism is most common with DVT from an iliofemoral thrombosis and is rare with those below the knee.
In DVT, deep vein valve destruction leads to a painful
swollen limb, oedema and venous eczema
What are the intracellular buffers
In a metabolic acidosis with a
decreased blood bicarbonate
the biochemical findings result from the addition of
an acid load to the extracellular compartment and this load may be endogenous or exogenous.
The body’s response to an acid load includes the titration of this load by various fixed intracellular and extracellular buffers.
The intracellular buffers consist primarily of
proteins and polypeptides
What are extracellular buffers
while the extracellular buffers
include haemoglobin, bicarbonate, albumin and creatinine.
Altitude Anaesthesia
Atmospheric pressure is linear fall with rise in altitude?
There is a non linear relationship between falling atmospheric pressure with rising altitude.
How does hyperpnoea affect O2 transport
Hyperpnoea due to hypoxia will lead to hypocarbia
This results in a left shift of the haemoglobin-oxygen dissociation curve;
although this improves the uptake of oxygen by blood in the lungs it makes its offloading in the tissues less efficient.
However the overall effect on oxygen transport is beneficial.
Analgesic effect of Nitrous @ Altitude
The analgesic effects of nitrous oxide
depend on its absolute partial pressure which will be less for the same % when at increased altitude.
Gas density affect on work of breathing
The reduced gas density at higher altitude reduces breathing resistance and therefore the work of breathing.
Is it okay to use a halothane vaporiser at altitude
Halothane vapourisers compensate for a change in atmospheric pressure and still produce the same partial
pressure of halothane in the outflow
How do NSAIDs and ACE cause Renal failure
ARF due to NSAIDs and ACE inhibitors is generally haemodynamically mediated.
They tend to cause ARF in
patients with a low renal blood flow in whom maintenance of an adequate GFR is dependent upon low afferent and high efferent arteriolar tone.
NSAIDs inhibit cyclo-oxygenase and so reduce the synthesis of locally produced prostaglandins which dilate the afferent arterioles,
while ACE inhibitors decrease the production of angiotensin-2 which constricts the efferent arterioles.
Impaired renal function and beta blockers
Beta blockers need to be given in reduced doses
due to their effect on renal blood flow
and some,
like atenolol, nadolol, pindolol and sotalol are excreted
unchanged from the kidney.
Impaire renal function
Cephalosporins
Loop diuretics
Most cephalosporins need to be given in reduced dosage in renal impairment.
Loop
diuretics are used in the treatment and prevention of ARF and have the theoretical advantage of reducing
oxygen consumption in the ascending loop of Henle by inhibiting active sodium reabsorption. However they
potentiate the nephrotoxicity of many other drugs and if used relatively large doses are required
Difference between DCCV and Defib
The major difference between cardioversion and defibrillation is that the former is synchronised so that the
shock occurs during the downstroke of the QRS complex.
In asystole, cardioversion is not indicated unless ventricular fibrillation cannot be excluded.
Atrial flutter and fibrillation (of onset less than 1 year) are indications for cardioversion.
Digoxin toxicity may lead to ventricular arrythmyias or asystole following cardioversion.
Therapeutic digoxin levels do not increase the risks of this but it is conventional to omit digoxin
several days prior to planned cardioversion
Murmurs in MS
TS
PHTN
ASD
MR
In mitral stenosis theres a mid diastolic mumur heard best at the apex.
The diastolic mumur in tricuspid stenosis is heard best along the lower sternal edge.
In pulmonary hypertension and atrial septal defect the
systolic mumur is heard best in the pulmonary area
wheras in mitral regurgitation it is at the apex.
Adrenaline affect on glucose
Adrenaline increases
glucagon and stimulates gluconeogenesis.
Patients on beta blockers are at risk of
hypoglycaemia under general anaesthesia, whilst thiazide diuretics commonly precipitate NIDDM
Diathermy
Current & freq
Current density
Which type requires more current
Diathermy employs
alternating current with a frequency of 1 MHz. The high current density at the intended site
is what causes the tissue damage. Bipolar diathermy requires less power than unipolar and is used for delicate
tissues eg in neurosurgery and ophthalmic surgery.
Pacemakers and diathermy
Diathermy is not contraindicated if the patient has a
pacemaker, but should be avoided if at all possible. Where unavoidable, bipolar diathermy is preferable to
unipolar. If unipolar diathermy must be used then the plate should be placed as distant as possible from the
pacemaker box. Diathermy can interfere with pacemaker function causing arrhythmias, triggering sensing and
even
Carotid Endarterectomy
Is there a shift in autoregulation curve in these patients?
Does CBF vary with PaO2
Hypertension is often present in patients
with carotid stenosis.
This shifts the autoregulation curve to the right.
CBF does not vary directly with
arterial oxygen content,
Does Hypoxia affect CBF
affected by anything?
How is the relationship between CBF /
PaCO2
What else affects CBF
hypoxia increases CBF
and this response is enhanced
in the presence of hypercarbia.
CBF is related to PaCO2 in a linear fashion and affected by cerebral metabolic rate, age, blood viscosity and temperature
AEP
How does it work
What about bg potentials
can this work every second
AEPs involve the use of auditory stimuli
(clicks) to
generate an electric potential
that can be measured over the
auditory area of the brain.
In order to cut out the effect of
background potentials,
including those produced by
outside noises multiple responses are summed.
Summation requires a number of consecutive signals so the AEP cannot be updated as frequently as every second.
The AEP can be divided into three:
Will it be useful for anaesthesia?
- Brainstem AEP (0-10 msec)
Posterior fossa surgery and hearing tests - Middle Latency AEP (20-80 msec)
Depth of anesthesia monitoring - Late Cortical AEP (>100 msec)
Conscious perception of sound
Use of AEP as a monitor of depth of anaesthesia is felt to show great promise partly because it is mostly
independent of the agent in use.
Question 11
In patients who require carotid endarterectomy
A. Cerebral autoregulation is often shifted to the right
B. Cerebral blood flow varies directly with arterial oxygen content
C. Cerebral blood flow varies in an exponential manner with PaCO2
D. Cerebral blood flow is affected by blood viscosity and age
E. Hypoxia increases cerebral blood flow
A. Cerebral autoregulation is often shifted to the right
D. Cerebral blood flow is affected by blood viscosity and age
E. Hypoxia increases cerebral blood flow
Question 12
Auditory Evoked Potentials (AEPs)
A. Brainstem AEPs are used to monitor depth of anaesthesia
B. Because the measurement lasts 80100 msec, up to ten independent measurements can be made each second
C. Changes in AEPs are mostly independent of the anaesthetic agent in use
D. AEPs of latency 1580 msec are of value for monitoring Posterior Fossa surgery
E. AEPs require a silent operating theatre for their successful application
C. Changes in AEPs are mostly independent of the anaesthetic agent in use
Considering a frequent social user of cocaine for general anaesthesia
A. Myocardial ischaemia occurs due to contaminant induced coronary artery disease
B. Chronic use of the drug lowers the seizure threshold
C. Chronic pulmonary problems are unlikely
D. A dose of Brompton cocktail could be an ideal pre-medicant
E. Hypertension and tachycardia preoperatively should not be treated
Considering a frequent social user of cocaine for general anaesthesia
B. Chronic use of the drug lowers the seizure threshold
C. Chronic pulmonary problems are unlikely
D. A dose of Brompton cocktail could be an ideal pre-medicant
Cacaine and GA
route
sequelae
Cocaine may be taken by inhalation or sniffing as well as injection so needle marks may not be present in the chronic abuser of cocaine.
Chronic use may result in serious
cardiovascular and cerebral disease
and lead to
congenital anomalies.
Hypertension, tachycardia, arrythmias, myocardial ischemia and infarction may result
from cocaine use.
Cocaine and ischaemia
other sequela from IV use
Pulmonary disease?
CNS change?
Coronary artery disease does
not seem to be induced in cocaine
users and coronary vessel
spasm is more the cause of ischaemia.
Endocarditis may result from intravenous use.
Pulmonary disease, apart from episodic pulmonary oedema from cardiovascular reasons, is not frequent.
Central nervous system changes may lead to personality changes or more seriously to a seizure disorder which can also be induced on
withdrawal
Is the brompton cocktail useful?
Should CVS Sy be Rx preop
The Brompton Cocktail contains cocaine and so may prevent withdrawal problems in a user
presenting for anaesthesia.
Cardiovascular instability pre-operatively should be actively managed to prevent
arrythmias or myocardial ischaemia occuring
Using the ‘Tec 6’ vapouriser for desflurane
A. The sump is heated to provide a vapour pressure of 10% above atmospheric pressure
B. The vapour circuit gas flow is not determined by the fresh gas flow
C. Compensation for changes in atmospheric pressure are by manual adjustment
D. The working pressure of the vapouriser increases linearly with increased fresh gas flow
E. Is not possible in event of a power failure
Using the ‘Tec 6’ vapouriser for desflurane
B. The vapour circuit gas flow is not determined by the fresh gas flow
C. Compensation for changes in atmospheric pressure are by manual adjustment
D. The working pressure of the vaporiser increases linearly with increased fresh gas flow
E. Is not possible in event of a power failure
The ‘Tec 6’ vaporiser
what i ump heated to
The 'Tec 6' is a non-variable bypass vapouriser allowing Desflurane to be used despite its high volatility and moderate potency.
It’s sump is heated to 39C at which
its vapour pressure is twice atmospheric at sea level.
This pressure provides the
vapour circuit gas flow
which is independent
of the fresh gas flow .
Does the TEC 6 auto adjust with changes in atm pressure
The ‘Tec 6’ requires manual adjustment
for changes in atmospheric pressure to avoid a fall in absolute partial pressure of anaesthetic for a certain % setting at increased altitude.
The working pressure of the vapouriser increases
linearly with fresh gas flow to maintain an output of desflurane independent of fresh gas flow.
Question 15
In the treatment of epilepsy
A. Thiopentone is the first line drug in status epilepticus
B. Phenytoin may be administered intravenously at a rate not exceeding 100 mg/min in an adult
C. Concurrent administration of phenytoin may increase the plasma concentration of phenobarbitone
D. Lamotrigine therapy should be started with a loading dose
E. Carbamazepine may cause hypernatraemia
C. Concurrent administration of phenytoin may increase the plasma concentration of phenobarbitone
Status
phenytoin rate and consideration
what can it cause
lamotrigine bolus?
s/e
carbamazepine s/e
Phenytoin can be given as long as the rate does not exceed
50 mg/min in an adult and
ECG monitoring is being
used.
Phenytoin may increase plasma concentrations of phenobarbitone, and decrease those of clonazepam, carbamazepine, lamotrigine and valproate.
Lamotrigine should be commenced at a low
dose and increased every 2 weeks to reduce the incidence of side effects including Stevens-Johnson syndrome.
Carbamazepine may cause hyponatraemia and this side effect has been used with beneficial effects in those with nephrogenic diabetes insipidus
Concerning pulmonary embolism (PE) and its management
A. About 60 % are thought to arise in the deep veins of the lower extremities and pelvis
B. Pulmonary angiography is the diagnostic gold standard
C. Cyanosis is common
D. An associated bradycardia is a good prognostic sign
E. Frusemide should be given to aid oxygenation
Concerning pulmonary embolism (PE) and its management
A. IS FALSE BECAUSE About 90 % are thought to arise in the deep veins of the lower extremities and pelvis
B. Pulmonary angiography is the diagnostic gold standard
what percent of PE arise from LL
What are signs
is brady good
About 90% of
PEs arise from the lower limbs and pelvis.
Tachypnoea with shallow breaths is seen in 80% of
patients and cyanosis is usually restricted to cases of massive PE.
Tachycardia may relate to the site of
obstruction and the onset of bradycardia is an ominous sign.
It is imperative to maintain right heart filling
pressures to perfuse the lungs and maintain right ventricular output therefore diuretics are contraindicated.
Question 17 Renal sodium wasting may result from A. Bilateral renal vascular disease B. Nephrotic syndrome C. Diabetic nephropathy D. Addison's disease E. Lithium therapy
Question 17
Renal sodium wasting may result from
D. Addison’s disease
Renal sodium wasting may result from:
Obstructive uropathy, Polycystic kidney disease, Addison's disease, congenital adrenal hyperplasia, unilateral renal artery stenosis resulting in the 'hyponatraemic hypertensive syndrome'.
Sodium retention may result from:-
Nephrotic syndrome, glomerular disease e.g. diabetic nephropathy, chronic
renal impairment from any cause, bilateral renal vascular disease. Long term use of lithium may result in
nephrogenic diabetes insipidus resulting in hypernatraemia if access to water is impaired.
Cushings Disease is associated with A. Obesity B. Hypertension C. Distal muscle wasting D. Menorrhagia E. Depression
Cushings Disease is associated with
A. Obesity
B. Hypertension
E. Depression
Cushings obesity type
appearance
muscle weakness?
changes to menstrual cycle?
Depression affects how many
The obesity in Cushings is typically central affecting the trunk.
The associated proximal muscle wasting gives
the so called ‘‘lemon on sticks “ appearance.
Muscle weakness can also occur without wasting and is caused by potassium depletion.
Oligomenorrhoea is caused by the steroid excess.
Depression affects 20% of patients.
Considering the use of peripheral nerve stimulators
A. Force of contraction continues to rise above the maximal stimulation threshold
B. Fade is a characteristic of depolarizing blockade
C. Double burst stimulation involves the use of two consecutive trains of four stimuli
D. Double burst stimuli should be separated by 0.75 seconds
E. A train of four stimuli are normally delivered at 0.5Hz
Considering the use of peripheral nerve stimulators
A. Force of contraction continues to rise above the maximal stimulation threshold
D. Double burst stimuli should be separated by 0.75 seconds
TOF = what
Force contraction continues?
Therefore
What does TOF detect
Train of four =
4 supramaximal stimuli
at 2Hz with
a fixed pulse width of 0.2 ms.
Force of contraction continues to slightly increase above the supramaximal threshold as a result of direct muscle stimulation.
Therefore delivered current should ideally be 10-20% above the threshold.
A train of four stimuli is used to
detect fade on repetitive stimulation following non-depolarizing blockade.
What is Fade due to?
what does Post tetanic facilitation enable
What does it consist of?
what is double burst stimulation?
Fade is due to non-depolarizer
blockade of pre-junctional ACh receptors
(which maintain ACH output with repetitive nerve stimulation).
Post tetanic facilitation enables a response to occur when none was detectable following single twitches or TO4.
The post tetanic count consists of a 5 s 50 Hz stimulus followed by a 3 s pause and then single twitches at 1 Hz.
The number of detectable twitches is inversely related to intensity of block.
Double burst stimulation = 3 × 50 Hz
stimuli separated by 0.75s
The following have autosomal dominant inheritance A. Hereditary spherocytosis B. Motor neurone disease C. Duchenne muscular dystrophy D. Myasthenia gravis E. Acute intermittent porphyria
The following have autosomal dominant inheritance
A. Hereditary spherocytosis
E. Acute intermittent porphyria
Aetiology MND & MG
Duchenne
AIP
males of females?
The aetiology of motor neurone disease and myasthenia gravis is unknown.
Duchenne muscular dystrophy is an
X linked recessive disorder.
Acute intermittent porphyria presents in early adult life usually around the age of 30,
women are affected more than men.
Concerning the diagnosis of pneumonia
A. H. influenzae is the commonest community acquired pathogen
B. Q fever is caught from farm animals
C. Endotracheal aspirates correlate poorly with LRTI
D. Recent influenza infection indicates the need for particular cover against Legionella pneumophilia
E. Ventilator acquired Pseudomonas aeruginosa infec
Concerning the diagnosis of pneumonia
B. Q fever is caught from farm animals
C. Endotracheal aspirates correlate poorly with LRTI
E. Ventilator acquired Pseudomonas aeruginosa infecion has a high mortality
what commonest ICU Infx
What defines a CAP
What are main pathogens
What should travel raise supsicion of
what can you get from birds
what about farm animals
Pneumonia is the commonest ICU infection.
If the infection is present within 48 hrs of hospital admission,
it is classified as a community acquired pneumonia.
Principal pathogens (in decreasing incidence) are Streptococcus pneumoniae,
Mycoplasma pneumoniae,
Haemophilus influenzae
and legionella species.
The latter should be suspected if there has been recent travel abroad.
Psittacosis is caught from birds and Q fever from farm
animals.
Influenza should raise suspicion of
Steroids of
Whats mortality with VAP
highest with
Other common pathogens
Recent influenza infection should
raise the possibility of Staphylococcus aureus infection
and steroid therapy the possibility of tuberculosis.
Ventilator acquired pneumonia
has a mortality above 40%,
the highest of which are in those
due to Pseudomonas aeruginosa.
Common pathogens include enterobacteriacae, P. aeruginosa and S. aureus although S. pneumoniae and H. influenzae are still encountered.
Is nosocomial Pneumonia easy to Dx
Diagnosis of nosocomial pneumonia is difficult as pyrexia, pulmonary infiltrates and purulent ET secretions may be due to other causes.
However, these signs and a
fall in the PaO2 are often
used to diagnose the condition.
ET aspirates correlate poorly w/ lower respiratory tract infection.
Blood cultures are neither
sensitive or specific in this condition.
Quantitative culture using bronchoalveolar lavage
may be useful.
Question 22
In the management of cerebral oedema
A. Mannitol is more effective than frusemide
B. Mannitol works more quickly than hyperventilation
C. Fluid restriction requires several days to have an effect
D. Steroids are of benefit in patients with tumours
E. Frusemide causes greater electrolyte abnomalities than mannito
Question 22
In the management of cerebral oedema
C. Fluid restriction requires several days to have an effect
D. Steroids are of benefit in patients with tumours
What is more effective mannitol or frusemide
how long to work
what is quicker
steroids and Head injury
Mannitol and frusemide are
equally effective and
take 15-60 mins to exert their effect.
However acute reduction
is best produced by hyperventilation.
Steroids should not be used in head injured patients
Question 23
Concerning the effects of a ‘massive’ transfusion
A. The commonest abnormality is an elevated INR
B. The plasma level of factor V falls in proportion to the volume transfused
C. Following a single blood volume replacement procoagulant levels are below 20% of their normal levels
D. Diffuse microvascular bleeding is related to low procoagulant levels
E. A fibrinogen level of 100 mg/dl is an indication for FFP in a bleeding patient
Question 23
Concerning the effects of a ‘massive’ transfusion
E. A fibrinogen level of 100 mg/dl is an indication for FFP in a bleeding patient
Defn of massitve tfusion
The arbitrary definition of a massive transfusion is the replacement of a patient's total blood volume by stored allogenic blood in less than 24 hours or the acute administration of more than 1.5 times the estimated blood volume.
Commonest abnormality in massive transfusion
The most common abnormality
is an absolute thrombocytopaenia,
but there is also a dilutional,
as well as an absolute,
fall in procoagulants and
other essential components of the coagulation cascade.
What changes are proportional to transfused volume
The platelet count falls in
proportion to the volume of blood transfused;
whereas plasma levels of factors V and VIII
corrrelate poorly with transfusion volumes,
and factor VII and fibrinogen levels
are unrelated to transfusion volume.
Normal haemostatic mechanisms function w/ low procoagulant?
what is diffuse microvascular bleeding related to
Predictor of microvascular bleeding
The normal haemostatic mechanism can function perfectly well with low procoagulant levels
but diffuse microvascular bleeding appears
to be mostly related to
thrombocytopaenia and severe hypofibrinogenaemia.
The most sensitive predictors of microvascular bleeding are a platelet count <50,000/dl
or a fibrinogen level < 0.5 g/l.
What causes a procoag level to fall 20%
For procoagulant levels to fall below 20% of their normal limits requires over two times blood volume replacement.
The following has been suggested as the level of abnormal coagulation tests justifying treatment with FFP in the presence of generalized microvascular bleeding:-
Prothrombin time >1.3 times control Partial thromboplastin time >1.3 times control Thrombin time >1.3 times control Fibrinogen 100 mg/dl Activated coag time >150s
Considering lactate metabolism
A. Increase in plasma lactate will be matched by an equal mmolar decrease in plasma bicarbonate
B. Fitness training does not affect the rate of rise in plasma lactate
C. Glucose metabolism to lactate releases ATP at the same rate as oxidation within the mitochondria
D. After exercise lactate is largely reconverted into glucose
E. Lactate filtered in the kidney is actively reabsorbed
Considering lactate metabolism
A. Increase in plasma lactate will be matched by an equal mmolar decrease in plasma bicarbonate
D. After exercise lactate is largely reconverted into glucose
E. Lactate filtered in the kidney is actively reabsorbed
Lactic acid
React
How does it compare to O2 consumption
Lactic acid reacts with
bicarbonate
leading to CO2 and lactate production.
At a certain level of exercise the
plasma lactate level rises sharply.
This is at between 50-80% of
maximal O2 consumption.
Lactate in an untrained person
Glucose metab to lactate atp release
In an untrained person plasma lactate
will rise at a lower level of
exercise than in the trained.
Glucose metabolism to lactate
releases ATP at least twice
as rapidly as mitochondrial metabolism
And can optimally provide
energy for 1.5
minutes of maximal muscle activity.
What happens to lactate after exercise
What happens to Filtered lactate
After exercise 80% of lactate
present is reconverted to
glucose in the liver
and restored in muscle and
20% is metabolised in the citric acid cycle.
Filtered lactate is actively
reabsorbed by the nephron to
a transport maximum of 75 mg/min
In acute pancreatitis
A. Contrast enhanced CT scans are of no use in diagnosing pancreatic necrosis
B. Infected pancreatic necrosis should be aspirated percutaneously under ultrasound control
C. Grey Turner’s sign describes umbilical ecchymoses
D. The cause is most commonly gallstones or alcohol
E. The APACHE II score should be calculated to predict mortality
D. The cause is most commonly gallstones or alcohol
Pancreatitis
d/t
Symptoms
Sx
Acute pancreatitis is most commonly
due to gallstones or alcohol,
although
viral infections,
drugs and
trauma may provoke an episode.
Most patients suffer epigastric pain,
but all upper abdominal
or chest pain should be
viewed with suspicion.
Pain may (rarely) be absent.
Grey Turner’s sign is flank bruising. Cullen’s sign describes periumbilical bruising.
Pancreatitis Rx
How deal with
What type of scan
Many sufferers recover
without high dependency care,
but in those with a severe attack,
multiple organ dysfunction often occurs.
Antibiotics are generally only
prescribed when an infected necrotic
pancreas is suspected, and in these cases the necrotic area should be debrided.
Necrotic pancreatitis can be
visualised with a contrast enhanced CT scan.
Nasogastric suction, H2 antagonists, TPN with ‘bowel rest’ and octreotide are often prescribed.
The APACHE II severity scoring system is not able to predict individual mortality risk.
The following ion compositions are correct
A. 0.9% salinesodium 131 mmol/l
B. Albumin 4.5% calcium 2 mmol/l
C. Hartmann’s solution chloride 154 mmol/l
D. Gelofusine calcium 5.1 mmol/l
E. Dextrose 4% saline 0.18% sodium 30 mmol/l
E. Dextrose 4% saline 0.18% sodium 30 mmol/l
The compositions of commonly used intravenous fluids must be known
0.9% saline contains 154 mmol of
sodium and chloride per litre.
Albumin 4.5% has no calcium and
gelofusine less than 0.4 mmol/l.
Hence they can be infused before / after blood.
Dextrose saline 4%/0.18%, contains 30 mmol/l of sodium and chloride
Hartmann’s solution has
131 mmol/l sodium, 5 mmol/l potassium, 2 mmol/l calcium and 111 mmol/l chloride.
The following are true concerning humidity and humidification of gases
A. Relative humidity is the ratio of absolute humidity to saturated humidity at a specified temperature
B. Operating theatre humidity should be maintained at no more than 30%
C. Heat and moisture exchangers can achieve 40% humidity
D. A nebuliser works on the poiseuille effect to entrain water across a pressure drop
E. The water trap for a simple bottle humidifier must be as larger as the humidifier bottle
The following are true concerning humidity and humidification of gases
A. Relative humidity is the ratio of absolute humidity to saturated humidity at a specified temperature
C. Heat and moisture exchangers can achieve 40% humidity
E. The water trap for a simple bottle humidifier must be as larger as the humidifier bottle
Absolute humidity
Rel humidity
how can humidification devices be defined
Absolute humidity is defined as
the mass of water in a volume of air.
Relative humidity is defined as
ratio of absolute humidity to saturated humidity at a specified temperature
usually presented as a %.
Humidification devices can be defined as active or passive; vapour or droplet producing; hot or cold and finally functioning in a breathing system or in the atmosphere.
Theatre humidity
why
HME achieve what humidification
How does a nebuliser work?
Bottle Humidifier water trap size
Theatre humidity should be
around 60%
as a compromise between
discomfort
(if too high) and
the increased risk of explosion
due to static electricity (if too low).
Heat and moisture exchangers can achieve 70% humidification.
A nebuliser works on the venturi or Bernoulli effect.
For a bottle humidifier the water trap should be at least the same size as the humidifier bottle
Question 28
Concerning humidification of inspired gases
A. Under normal circumstances, the relative humidity in the upper trachea is 40%
B. Ciliary clearance continues normally until the relative humidity falls below 24%
C. Heat and moisture exchangers (HMEs) are recommended for paediatric use
D. Water reservoirs are particularly at risk of contamination with Pseudomonas species
E. Ultrasonic nebulisers produce optimal humidification
D. Water reservoirs are particularly at risk of contamination with Pseudomonas species
How is inspired gased heated
Rel humidity
temp
Gas reach alveoli
Saturation
At what stage is ciliary activity affected
Inspired gas is warmed
and humidified
in the nasopharynx and
Usually has a
relative humidity of 90% and a
temperature of 32-36°C.
By the time gases have
reached the alveoli
they are fully saturated and at 37°C.
Ciliary activity ceases above 41°C and slows down if relative humidity falls below 75% at 37°C.
