Acid Base Disorders Flashcards

Question

What are the 2 measures of bicarbonate? Which one is often used?

Answer 1

1. main lab bicarbonate 2. standard bicarbonate main lab bicarbonate is most commonly used

Answer 2

it is sometimes called "total CO₂" as it is an approximation of bicarbonate calculated, in part, from CO₂ Normal range **22 - 29 mmol/L**

Answer 3

**22 - 26 mmol/L**

Answer 4

standard bicarbonate removes the respiratory contribution

Answer 5

**normal standard bicarbonate:** the disorder is ALL respiratory **abnormal standard bicarbonate:** this disorder has a metabolic component

Answer 6

it is the amount of acid or alkali needed to titrate blood pH to 7.40 it takes into account all buffers, not just bicarbonate it tells us if there is a **metabolic component** to a disorder

Answer 7

**- 2.3 to + 2.3 mmol/L**

Answer 8

**negative BE** (\< -2.3 mmol/L): there is metabolic acidosis (a base deficit) **positive BE** (\> 2.3 mmol/L): there is a metabolic alkalosis (a base excess)

Answer 9

the difference between the sum of *measured* anions and cations normal range = **8 - 16 mmol/L** anion gap is not zero in healthy patients as not all anions are measured

Answer 10

( [Na⁺] + [K⁺] ) - ( [Cl^-] + [HCO₃^-] )

Answer 11

there are significant amounts of unmeasured anions present e.g. ketones, lactate, salicylate, proteins etc.

Answer 12

1. nausea, vomiting and anorexia 2. subjective sense of dyspnoea caused by stimulation to the respiratory centre 3. Kussmaul breathing

Answer 13

a deep laboured breathing pattern

Answer 14

1. increased acid formation 2. decreased acid excretion 3. loss of bicarbonate 4. acid ingestion

Answer 15

these are **increased anion gap** metabolic acidoses (plus uraemia) 1. ketoacidosis 2. lactic acidosis 3. poisoning 4. inherited organic acidoses

Answer 16

1. diabetic ketoacidosis 2. alcoholic ketoacidosis 3. starvation

Answer 17

1. type A - caused by tissue hypoxia 2. type B - metabolic and toxic causes

Answer 18

1. salicylate poisoning 2. toxic alcohols - e.g ethylene, glycol, methanol, ethanol

Answer 19

1. uraemia due to renal failure 2. RTA type 1 (renal tubular acidosis)

Answer 20

**GI causes:** diarrhoea and fistulas **Renal causes:** RTA type 2 (proximal) carbonic anhydrase inhibitors (e.g. acetazolamide)

Answer 21

* an acute increase in [H⁺] is resisted by bicarbonate buffering, causing decreased HCO₃^- * protein buffering is important in chronic acidosis

Answer 22

* stimulation of the respiratory centre leads to hyperventilation * this blows off CO₂ * this process is self-limiting as it generates additional CO₂

Answer 23

* urine H⁺ excretion is maximised * there is an increased rate of bicarbonate regeneration

Answer 24

**sodium bicarbonate** **IV sodium bicarbonate:** this is only given if pH \< 7.00 **oral bicarbonate:** this is given in CKD and RTA types 1 and 2

Answer 25

1. rapid correction impairs O₂ delivery 2. rebound alkalosis is possible

Answer 26

they are usually related to an underlying disorder

Answer 27

it increases protein binding of Ca²⁺, leading to **hypocalcaemia** this causes headache, lethargy and neuromuscular excitability sometimes with delirium, tetany and seizures it lowers the threshold for arrhythmias

Answer 28

1. administration of bicarbonate 2. loss of H⁺ (usually through vomiting) 3. potassium depletion

Answer 29

excretion of H⁺ is favoured in order to spare K⁺ at aldosterone-controlled renal transporter

Answer 30

K⁺ ions are transported out of RBCs to increase plasma concentration H⁺ ions move into the RBC to maintain electroneutrality This leads to a decrease in plasma [H⁺]

Answer 31

there is release of H⁺ from buffers

Answer 32

reduced respiratory rate in order to retain CO₂ this is self-limiting, as an increase in pCO2 stimulates the respiratory centre

Answer 33

Decreased GFR leads to inappropriately high bicarbonate reabsorption potassium deficiency contributes to persistence of alkalosis

Answer 34

1. treat the underlying cause 2. treat factors that sustain alkalosis e. g. replace potassium

Answer 35

1. they are usually related to an underlying disorder 2. some patients complain of dyspnoea

Answer 36

1. defective **control** of respiration 2. defective respiratory **function**

Answer 37

1. CNS depression 2. CNS disease 3. Neurological disease

Answer 38

anaesthetics and sedatives narcotics and opiates

Answer 39

1. trauma 2. haemorrhage 3. infarction 4. tumour 5. infection

Answer 40

1. spinal cord lesions 2. motor neurone disease 3. Guillain-Barre

Answer 41

1. myopathies 2. pneumothorax 3. pleural effusion 4. inadequate mechanical ventilation

Answer 42

1. COPD, severe asthma, etc. 2. impaired perfusion

Answer 43

there is limited buffering by haemoglobin

Answer 44

an increase in pCO2 stimulates the respiratory centre, but disease prevents an adequate response

Answer 45

1. there is maximal bicarbonate reabsorption 2. almost all phosphate is excreted as **H₂PO₄^-**(rather than HPO₄^2-) 3. there is a marked increase in urinary NH₄⁺

Answer 46

1. treat underlying cause 2. maintain adequate arterial pO₂, but avoid loss of hypoxic stimulus to respiration 3. avoid rapid correction of pCO₂as this increases risk of alkalosis

Answer 47

1. usually related to an underlying disorder 2. more severe alkalosis leads to hypocalcaemia

Answer 48

1. central 2. pulmonary 3. iatrogenic (excessive mechanical ventilation)

Answer 49

1. head injury 2. stroke 3. hyperventilation 4. drugs (e.g. salicylates) 5. sepsis (cytokines) 6. chronic liver disease (toxins)

Answer 50

1. pulmonary embolism 2. pneumonia 3. asthma 4. pulmonary oedema

Answer 51

there is release of H⁺ from non-bicarbonate buffers

Answer 52

the inhibitory effect of decreased pCO2 is overwhelmed by the primary cause

Answer 53

there is decreased renal regeneration of bicarbonate as CO₂ is a substrate, this means it is preserved

Answer 54

1. treat the underlying cause 2. rapid symptomatic relief by re-breathing 3. sedation or prevention of hyperventilation by mechanical ventilation

Answer 55

**full compensation:** occurs if compensation returns the pH to normal **partial compensation:** occurs when the pH has not returned to normal **over-compensation** does not occur in any acid-base disorder

Answer 56

two or more primary acid-base disorders presenting in the same patient they can either be **additive** or **counterbalancing**

Answer 57

**additive** * respiratory acidosis - increased pCO₂ * AND metabolic acidosis - increased lactic acid

Answer 58

**additive** * metabolic alkalosis - loss of H⁺ * AND respiratory alkalosis - increased respiratory rate

Answer 59

**counterbalancing** * metabolic acidosis * AND respiratory alkalosis - increased respiratory rate

Answer 60

**counterbalancing** * metabolic alkalosis - loss of H⁺ * AND metabolic acidosis (decreased renal H⁺ excretion)