Lab 2 - Isohydria: Acid-base balance, gasometry Flashcards
What can acid-base disturbances signifficantly impact?
case morbidity and mortality
What is isohydria
The concentration of H+ ions in the blood
PH= -log10 H+
What is the stability of isohydria essential for
Cell membranes and enzyme activity
What can a change in PH result in
electrolyte imbalance,
change in muscle irritability too
Why is intracellular and extracellular buffers importaint
If the rate of H+ production is too rapid for elimination for the body
What is the function of the buffer solution
It can resist PH changes
What is the most importaint physicochemical buffer system in all fluid compartments?
Carbonic acid - bicarbonate system
Besides Carbonic acid - bicarbonate system, what are the other systems
Primary - Seccondary phosphate system
Protein-Proteinate buffer system
What form the vital buffer system
Lungs and kindey
How does the lung regulate the PH acticity
by retaining or excreeting CO2
What happens with the equation in the lung when the `H+ is increased
Equation moves to the left generating extra CO2
Leading to hypercapnia stimulating the ventilation and lungs can eliminate the CO2
The capacity to retain CO2 is limited
True or False
True
Because of oxygen demand
Pulmonary capacity to excrete CO2 is low
False
The Pulmonary capacity to excrete CO2 is it’s HUGE
What is Kussmaul breathing
Normal frequency, but very deep inspiration and expiration
The kidneys can excrete or retain CO2
True or false
False
The kidney can excrete or retain H+
and also regenerate HCO3- via Complex tubular mechanism
How does the kidney regenerate HCO3-
via Complex tubular mechanism
How long does it take for the complex tubular mechanism to regenerate HCO3-
Long time
Hours to days
If the CO2 levels in the body increase, what happens with the EQUATION due to kidney buffer system
The equation will push to the RIGHT
- Produce excess H+ and HCO3- and then H+ can be eliminated by the KIDNEY
Acid-Base evaluation is a routine test in emergency patients. True or false
True
What can the acid-base status tell us something about
Function of the VITAL BUFFER SYSTEMS
The acid-base analyzers are simple test not complex
true or false
False
They are complex devices
What does the acid-base analyzers measure
blood-gas parameters electrolytes hemoglobin haemaocrit lactate glucose etc
Venous blood is essential for assessment of the RESPIRATORY function
True or false
False
Arterial blood is ssential for assesment of the respiratory function
Both arterial and venous sample provide usefull information about the metabolic state on the animal
True or false
True
You must avoid air contamination of the samples
True or false
True
Astrup-technique is a CO2 retaining method
False
Its a method to prevent air contamination of the sample
What will be present in aircontaminated samples
Increased pO2
Note 150 mmHg pO2 in athmospheric air
CO2 will evaporate into the air shortly after sampling, the pCO2 may be DECREASED
True or false
True
When sampling anticoagulated blood should be used
True or false
True
Ca-equilibrated Li-Heparanized syringe
In case of longer storage of sample the pCO2 will be increased
True or false
True
How long can you store the sample in room temperature
No more than 5-10min
How long can you store the sample in the refrigerator (0-4 degree)
Not more than 30min
How do you measure PH and CO2
By Analyzers utilze ion selective electrodes (ISE)
At which temp are the samples analysed under?
37 degrees
The soluibility of gasses are dependent on temseratuse
True or false
True
The measured values need to be corrected to the temperature of the patient
True or false
True
Actual PH in blood
Ph 7,35-7,45
Partial pressure
pCO2
Respiratory Parameter
40mmHg
(35-45)
Standard Bicarbonate concentration
HCO3- mmol/L
Metabolic Parameter
21-24 mmol/L
Bicarbonate conc of plasma, if the blood is equlibrated to 40mmHg pCO2 on 37 degrees its value depends on pCO2
Actual Base excess (ABE) (demand) or residue (mmol/L)
Metabolic Parameter
+-3,5 mmol/L
Titratable acidity or basicity - the amount of acid or base needed to equlibrate blood to PH 7,4 (pCO2 is stabilized at 40 mmHg/l on 37 degrees)
TCO2
Total CO2 concentration in plasma (mmol/L)
23-30 mmol/L
CO2 content of blood liberated by strong acid.
TCO2 is 10% higher than plasma HCO3-
True or false
False
TCO2 is 5% higher than plasma HCO3-
TCO2 gives no direct information about respiratory function.
True or false
True
TCO2 gives no direct information about respiratory function.
TCO2 may be ignored when HCO3- result is pressent
True or false
True
PH in blood during acidosis
<7,4
PH in blood during alkalosis
> 7,4
At which PH value is the Acidaemia decompensated
At PH <7,35,the Acidaemia is decompensated
At which PH value is Alkalaemia decompensated
At PH >7,45, the Alkalaemia is decompensated
What is step one in Acid-Base state analysis
Evaluate wheter Acidaemia (acidosis) or Alkalaemia (Alkalosis) is present
What is the blood PH referece range
Between 7,35-7,45
What does compensated/decompensated mean
Indications of the outcome, the effectiveness of all processes together - regardless of whether or not we see compensatory effort
Step 1 in evaluation of ABB state must not be omitted(excluded) because the shift of the other parameters are compared to the PH change
True or false
True
What is step 2 in AB state investigations
Search for the Cause = PRIMARY PROCESS of the alteration of the observed PH alteration
Acidaemia and alkalemia can occur due to metabolic or respiratory changes
True or false
True
Predominant change of pCO2 reffers primarly to
Respiratory proceses
Predominant change of HCO3- and ABE refers primarly to
Metabolic processes
Respiratory background
In case of pCO2 show a strong shift in the opposite direction as PH
True or False
False
In case of pCO2 show a strong shift in the same direction as PH
Respiratory background
What happens when pCO2 is >40mmHg
More of it binds to water and forms carbonic acid
Respiratory background
Increased pCO2 can be called a shift in alkaloid direction
False
Increased pCO2 result in acidic direction
Respiratory background
In situations of impared gass exhange, the ramaining high CO2 forms? and lead to?
Carbonic acid
Shifts PH to acidosis = RESPIRATORY ACIDOSIS
Respiratory background
When does respiratory alkaloisis happen? Exsample
When hyperventilation is pressent - to mutch CO2 is exhaled = causes elevation of the PH = RESPIRATORY ALKALOISIS
Metabolic background
When the PH alteration is caused by a metabolic process or kidney malfunction
Metabolic background
Metabolic parameters is
HCO3- and ABE
Metabolic background
In case of Lactic acid production what will occur
Metabolic acidosis
Both metabolic parameters are shifted to acidic direction
Metabolic background
What is actual base excess
It is a calculated parameter which has a defined aid correction of acid base disturbances
In alkalosis - Parameter shifts from 0 to positive range= in the lack of acids.
Negative base excess means
a lack of base
Always evaluate wheter the change (resp and metab) parameter respond to ………..
The alteration of PH
The primary process is the one that leads to the acid-base disturbance = This parameter is always shifted in the SAME direction as the PH and usually this shift is significant
True or false
True
When can you detect compensatory effects
When the shift switches in the oposite direction compared to PH
If all parameters shift in the same direction as the PH
Primary process shows signifficantly bigger shift
What i s characterized as a bigger shift
25-30% more than normal value
What is mixed acidosis
All parameters shifted in same direction as PH - mostly seen in advance acidosis
What is step 3 in AB state evaluation
Evaluate wheter compensation effort is visuable in the result or not
If either respiratory or metabolic parameters is shifted in the opposite direction than the PH - what will happen
Compensatory effect is visuable
What happens due to Compensatory effect in metabolic acidosis in the lung
Lungs try to compensate by highly effective gas exchange
= Very deep breath and longer gas exchange
= Kussmaul breathing
= excretion of lots of CO2 - PH is acidic and CO2 changes in alkaline direction
What is step 4 in AB state evaluation
Give an example what can cause the established changes
Metabolic acidaemia/Acidosis
PH
HCO3-
BE
<7,4
<20mml/L
Metabolic acidaemia/Acidosis
Causes
- HCO3- loss:
2. Increased acid intake:
Metabolic acidaemia/Acidosis
Causes of HCO3 loss
diarrhoea
Ileus
kidney tubular disturbances
Metabolic acidaemia/Acidosis
Causes of Increased acid intake:
Increased acid intake:
- Fruits
- too acidic silage
- overdose of acidifying drugs (ammonium chloride, vit C)
- Increased acid production - lactic acid prod due to anaerobic glycolysis, frequent in anorectic, weak animals
- In cattle - grain overdose, leading to volatile acid production.
- Increased ketogenesis, leading to ketosis due to relative or objective starvation or DIABETES MELLITUS
- Decreased acid excretion: RENAL FAILURE
- Ion exchange: HYPER KALAEMIA (H/K PUMP)
- Some Xenobiotic- ethylene-glycol toxicosis:
Metabolites are acidic molecules leading to metabolic acidosis and finally remal failure will worsen it
What are the effects of Metabolic acidaemia/Acidosis
- Kussmaul breathing = hyperventilation (not panting)
- Hypercalcaemia - increased mobilation from bones in case of long term acidosis.
- Vomiting, depression
- Hyperkalaemia: decreased cardiac muscle activity.
SA, AV block, Bradycardia - in urine- titrable acidity increases(not process of renal origin)
Treatment of Metabolic acidaemia/Acidosis
Providing adequate ventilation
If PH <7,2 = Infusion therapy involving alkaline fluid
(amount is calculated by using ABE)
Treatment of Metabolic acidaemia/Acidosis
ABE formula
Required amount of base (mmol) = ABEBwtK
K is a coeffesient
K in small animals: 0,3
K in large animals: 0,2
Half of amount given first
1-2 hours control = is the other half nessessary
Treatment of Metabolic acidaemia/Acidosis
ABE formula - Half of the calculated amount shold be given first
True or false
True
What is the anion gap
The anion gap is a usefull parameter when attempting to determine the cause of metabolic acidaemia
The anion gap describes the difference between the….
Commonly measured cations in plasma, and the commonly measured anions
How do you maintain the electronneutrallity
By keeing the concentration of cations and anions equal in the plasma
Unmeasured cations (UC+) include
- Proteins that are positively charged + at physiologic ph
2. Free or ionized forms of calcium (Ca2+) and magnesium (Mg2+) (Not seen in high concentration)
Unmeasuref anions (UA-) include
- Proteins that are negatively charged - at physiologic ph (Albumin mostly)
- Acids that are produced during physiologic and pathologic processes. (Lactate, Phosphates, Sulphates and ketones)
- Some toxins and drugs: Methanol, salicylate, ethylene glycol.
UA- are found in lower concentration and are therefore hasn’t got a great impact on the anion gap
True or false
False
They are found in higer concentration and has a greater impact on the anion gap.
What is the reference range for anion gap
8-16mmol/L
Why is the anion gap usefull for us to determine
Because its useful to determine wheter metabolic acidaemia is due to primary HCO3- loss or accumulation of organic acids
To maintain electronneutrality, how do youbalance a decrease in HCO3-
By an increase of Cl- or UA-. If CL- replaces the HCO3- it usually happen due to direct HCO3- loss (eg. Diarrhoea), the anion gap will be normal.
= Hyperchloraemic metabolic acidose
What happens if the reduction of HCO3- is due to accumulation of UA- (lactate, bhb)
The Cl- stays normal
= Normochloraemic metabolic acidosis.
Name cases of NORMAL ANION GAP
HYPERCHLORAEMIC
- Diarrhoea (HCO3- loss)
- Early kidney failure
(H+ retention, decreased ammonia excretion) - Renal tubular acidosis
(Proximal (FANCONI SYNDROME) or distal tubular effect) - Acidifying substances (NH4Cl)
Name cases of INCREASED ANION GAP
NORMOCHLORAEMIC
- Azotaemia or uraemia
( Advanced kidney failure - organic acid accumulation) - Lactacidosis
(Shock, hypovolaemia, poor tissue perfusion, tissue necrosis) - Ketoacidosis
( Diabetic ketoacidosis - increased hepatic production of ketone bodies) - Toxicosis
(Ethylene gycol toxicosis - also alcohol)
Metabolic alkalemia/ alkalosis
PH
HCO3-
BE
PH >7,4
HCO3- >28mmol/l
BE >+3,5mmol//L
Metabolic alkalemia/ alkalosis
Causes
- Increased allkaline intake
= Overdose of bicarbonate, or feeding rotten food - Increased ruminal alkaline production
= High protein intake, Low carbohydrate intake, anorexa, hypomotility - Decreased hepatic ammonia catabolism (liver failure)
- Increased acid loss
= vomiting, gastric dilation volvulus syndrome, abomasal displacement - Ion exchange
= hypokalemia - due to henle loop diuretics remember H+/K+ pump.
(Paradoxical aciduria)
Metabolic alkalemia/ alkalosis
Effects
- Breathing depression (compensory resp. acidosis)
- low breathing rate - hypoventilation - Muscle weakness - hypokalemia
- Hypocalcaemia due to increased Ca2+ bindings of ALBUMIN
- Ammonia toxicosis
- Arryhtmia, biphasic P, QT increase (AV conduction disorder), Flat T, U wave
- Paradoxical aciduria
Metabolic alkalemia/ alkalosis
Treatment
In general its enough to treat the underlying electrolyte imbalance
Respiratory acidaemia/acidosis
PH
pCO2
PO2
PH = <7,4 pCO2 = 40 mmHg pO2 = <40mmHg
Respiratory acidaemia/acidosis
Causes
- Upper airway obstruction
- Pleural cavity disease, PNEUMOTHORAX
- Pulmonary disease: SEVERE PNEUMONIA, PULMONARY OEDEMA, DIFFUSE LUNG METASTASIS, PULMONARY THROMBOEMBOLISM
- Depression of central control of respiration
DRUGS, TOXINS, BRAINSTEM DISEASE - Neuromuscular depression of respiratory muscles
- Muscle weakness, eg. muscle weakness in hypokalemia
- Cardiopulmonary arrest
Respiratory acidaemia/acidosis
Effects
- DYSPNOEA
- CYANOSIS
- SUFFOCATION
- MUSCLE WEAKNES
- TIREDNESS
Respiratory acidaemia/acidosis
Treatment
- Assisting the ventilation - providing fresh air or oxygen therapy
- Treatment of the cause - eg
- DIURETIC treatment in case of fluid accumulation in the lung, PULMONARY OEDEMA,
- Specific cardiologic treatment, in case of underlying cardiac diseases
- Treatment of pneumonia= removal of fluid from plural space etc.
Respiratory acidaemia/acidosis
Treatment
Mildly anxiolytic/sedationg drugs to decrease the fear and excitement of animals caused by hypoxia
True or false
True
Respiratory alkalaemia/alkalosis
PH
pCO2
PO2
PH >7,4
pCO2 < 40 mmHg
pO2 > 40 mmHg
Respiratory alkalaemia/alkalosis
Causes
- Increased loss of CO2 = HYPERVENTILATION
- Excitation
- Forced ventilation (anaesthesia)
- Epileptiforme seizures
- Fever, hyperthermia
- Intertitial lung disease
Respiratory alkalaemia/alkalosis
Effects
- Hyperoxia, the decreased pCO2 : pO2 ratio may lead to APNOEA
- Increased elimination of HCO3- by the KIDNEYS
Respiratory alkalaemia/alkalosis
Treatment
- Anxiolytic or mild sedative drug in case of HYPEREXCITATION
It is important to increase the pCO2 level by closing the nose or nostrils until breathing normalises (only few min)
Blood gas analysis is performed to ………
Assess effectiveness of gas exchange
= Ventilation in the lung during anaesthesia or dyspnoea
Sample and sampling for Blood Gas analysis
Where to take samples from
Arterial blood because it’s essential for PRECICE assessment of respiratory FUNCTION
= How effective the gas exchange is in the alveoli
What does venous blood gas analysis reflect
How mutch oxygen that is consumed by the body
It is not necessary to use antigoagulated blood when performing blood gas analysis
True or False
FALSE
We use anticoagulated blood
Ca-equilibrated Li-heparinised plasma, preheparinized syringe
Which sampling method shall be used when performing blood gas analysis
The Astrup-technique
- Closed sampling method
Why must the blood gas sample be stored with no air/vacum space
Because CO2 can evaporate
Air contamination causes false increased pO2 pressure
How long can you store the sample before measuring
Within 15min or place on ice to minimize changes in blood gas PARTIAL PRESSURE as a result of continuous metabolism
The blood gas analyses….
Directly the pCO2 and pO2 with the iron spesific electrodes (ISE)
In which condition are the samples investigated under
Standarized temp 37 degrees
The dissociation of gasses is independent of temp
True or false
False
Both standard 37 degrees and the patient temp has to be accounted for
Parameters and refferance ranges
pO2 - Partial pressure of oxygen
Indicates the ability of the lung to oxygenate blood
Arterial= 88-118 mmHg
Venous= 35-45 mmHg
Parameters and refferance ranges
pCO2 - Partial pressure of carbon dioxide
Indicates the ability of the alveolar gas exchange to remove the CO2.
It is directly proportional to the rate of CO2 production, and inversely proportional to alveolar ventilation
Arterial = 35-45 mmHg
Venous = 35-45 mmHg
Parameters and refferance ranges
Oxygen saturation
SAT or SatO2
Oxygen saturation (%)= Calculated from Hb and pO2 Indicates the fraction of oxygen-saturated hemoglobin relative to total hemoglobin in the blood Arterial= 90-100% Venous= 70-80%
Parameters and refferance ranges
FiO2
Fraction of inspired oxygen
Is the assumed % of O2 concentration participating in gas exchange in the alveoli
Room air= 0,209 = 20.9%
O2 enriched= 0,21-1,0
>0,5 risk of O2 toxicity
What is the most importaint parameter to access the gas exchange capacity in animals
paO2 and paCO2
Overall effectiveness of gass exchange are catherorized into 3 groups
Normventilation - Arterial= 80-110 mmHg in room air - Hypoventilation <60 mmHG Hyperventilation - for CO2 hypocapnia or hypercapnia are used
Oxygen saturation value in room air
97-100%
Partial oxygen pressure under 40-50 mmHg - what could be visuable
Cyanosis
Hypoventilation
pCO2
> 45 mmHg (most reliable in arterial blood)
Hypoventilation
Hypoxemia depends on the degree of hypercapnea, and the FiO2
True or false
True
Hypoventilation
Low O2 saturation depends on
Blood Hb concentration, RBC cound
Hypoventilation
pCO2
Hypoxemia
Low O2 saturation
Hypoventilation causes
- Upper airway obstruction
- pleural effusion
- drugs or disorders affecting central control of respiration = general anesthesia
- Neuromuscular diseases (reacts on muscle and respiratory system, eg. HYPOKALAEMIA)
- Overcompensation of metabolic alkalosis
Hypoventilation Effects
Dyspnoea
Cyanosis
Hypoventilation treatment
- Assisting ventilation eg. assisted breathing, oxygen treatment
- Diurethic treatment - incase of fluid accumulation in lungs, pulmonary oedema> or in the thoracic cavity
- Mildly anxiolytic/ sedating treatment
Additional to hypoventilation, arterial blood gas tensions are also influenced by
Ventilation perfusion missmatch (VA/Q)
Ventilation perfusion missmatch
- Normal ventilation
- Inadequate ventilation
- Normal ventilation with inadequate perfusion
blood passes alveoli for oxygen= EMBIOLA, HEART INSUFFIENCY - Inadequate ventilation with normal perfusion
ventilation of alveoli doesn’t allow enough oxygen
Hyperventilation
PaCO2
<35 mmHg
Hyperventilation
Hyperoxaemia is usually present together with decreased SAT
True or false
False
Hyperoxaemia is usually present together with INcreased SAT
Hyperventilation
Causes
- Iatrogen
= Forced ventilation during anesthesia (high FiO2) - Seizures, epilepsy
- Excitation
(mild=frequently visiting vet. Extreme= shock after accident) - Compensation of severe metabolic acidosis
= Kussmaul breathing
Hyperventilation
Venous samples should not be used to assess directly gas exchange
True or false
True
Hyperventilation
What does oxygen saturation inform us about
It informs about tissue O2 usage
Hyperventilation
When does ISCHEMIC reaction occur
Venous saturation below 60% indicates that the body is in lack of oxygen
IMPORTAINT
acid-base or blood gas analyzers regardless which name we use include……
- ISE for pH, CO2, HCO3-
- Ions: Ca2+, Na+, K+, Cl-
WHen we interpret, all 3 barameters should be considered
- ACID BASE PARAMETER
- BLOOD GAS ANALYSIS
- INOGRAM
