Urinary 6 Flashcards

Question

Give the reference ranges for: pH pCO2 [HCO3-] pO2

Answer 1

pH = 7.38 - 7.42/7.46 pCO2 = 4.2 - 6.0 kPa [HCO3-] = 22 - 29 mmol.l-1 pO2 = 9.8 - 14.0 kPa

Answer 2

Decrease Normal Decrease Normal

Answer 3

Normal or Low Low Low Normal

Answer 4

High Normal High Normal

Answer 5

High/Normal High High Low

Answer 6

Low High Normal Low

Answer 7

Low/Normal High High Low

Answer 8

High Low Normal Normal/High

Answer 9

High/Normal Low Low High/Normal

Answer 10

**Total:** 3500mmol **ICF** 98% 120-150mmol/l *Mainly in skeletal muscle cells, liver, RBCs and bone* **ECF:** 2% 3.5-5mmol/l

Answer 11

Na+/K+ ATPase

Answer 12

High ICF and low ECF [K+] contributes to the resting membrane potential and allows for action potentials An increase in ECF [K+] would depolarise cells A decrease in ECF [K+] would hyperpolarise cells **These changes would have profound effects on excitability of cardiac and nuromuscular tissues:** Problems with cardiac conduction and pacemaker automaticity Alter neuronal function, skeletal and smooth muscle function Arrhhythmias, cardiac arrest, muscle paralysis

Answer 13

Intestine and colon absorb K+ Substatial amounts of K+ therefore enter the ECF (Danger!) Kidney's cannot excrete this K+ fast enough 4/5 of ingested K+ moves into ICF/cells within minutes After a slight delay K+ is released from ICF slowly as Kidney's begin to excrete K+ Excretion takes 6-12h

Answer 14

**External balance:** Adjustment of renal K+ to match intake Responsible for longer term control of total K+ **Internal balance:** Moves K+ between ICF and ECF to correct ECF levels of K+ should they rise or fall Effect is immediate (within minutes of imbalance) Responsible for moment to moment control

Answer 15

Movement of K+ into ICF via Na+/K+ ATPase Movement of K+ out of ICF into ECF via K+ channels (E.g. ROMK)

Answer 16

**Hormones (acting on Na+/K+ ATPase):** Insulin Aldosterone Catecholamines **Increased [K+] in ECF** **Alkalosis:** Low ECF [H+] causes H+ to move out of cells and correct imbalance causing a reciprocal shift of K+ into cells (maintains electrochemical balance)

Answer 17

K+ in plasma stimulates insulin release under normal physiological conditions This leads to increased K+ uptake by muscle and liver via an increase in Na+/K+ ATPase channels Administration of insulin boosts this process and lowers ECF [K+]

Answer 18

K+ in serum stimulates aldosterone secretion Which in turn stimulates uptake of K+ via Na+/K+ ATPase

Answer 19

Acts via B2 adrenoceptors which in turn stimulate Na+/K+ ATPase This increases the cells uptake of K+

Answer 20

**Low ECF [K+]** **Exercise** **Cell lysis (K+ leaks through ruptured membrane)** **Increase in ECF osmolarity** **Acidosis (Increase in ECF [H+]:** Shift of H+ into cells and reciprocal K+ shift out (to preserve electrochemical gradient)

Answer 21

Skeletal muscle contraction leads to a net loss in K+ during recovery phase of action potential Damage to muscle also releases K+ Increases are proportional to intensity of exercise Uptake of K+ into non-contracting cells + Exercise stimulation of catecholamines prevents dangerous rise Cessation of exercise leads to rapid fall in ECF [K+] (often \<3mmol/l)

Answer 22

**K+ leaks through ruptured membranes** **Rhabdomyolysis:** Trauma to skeletal muscle resulting in muscle cell necrosis **Intravascular haemolysis:** Breakdown of RBC in vascular system E.g. Incompatible blood transfusion **Cancer chemotherapy**

Answer 23

Water moves out of cells into ECF to correct osmolarity Increase in [K+] in ICF Net movement of K+ into ECF via concentration gradient (despite action of Na+/K+ ATPase)

Answer 24

K+ movement in and out of a cell causes H+ to move in opposite direction Significant K+ movement (Hypo/hyperkalaemia) can therefore lead to acidosis or alkalosis

Answer 25

K+ freely filtered at glomerulus **PCT:** Uptake via paracellular diffusion 67% of filtered load reabsorbed **Thick al of LoH:** Uptake is active (Driven by basolateral Na+/K+ ATPase and Na+/K+/2Cl- transporter in apical membrane 20% reabsorbed **Principal cells of DCT and Cortical CD:** Substantial secretion of K+ in a normal or high K+ diet Little secretion in a low K+ diet **Intercalated cells of DCT and CD:** Reabsorb 10-12%

Answer 26

Na+/K+ activity on BLM High intracellular K+ creates chemical gradient across luminal membrane Luminal ENaC allows Na+ to move down chemical gradient, producing an electrical gradient Favourable electrochemical gradient allows K+ secretion via K+ luminal channels

Answer 27

**ECF [K+]:** Stimulates Na+/K+ ATPase Increases permeability of apical K+ channels Stimulates aldosterone secretion **Aldosterone:** Increases transcription of Na+/K+ ATPase, K+ channels and ENaC **Acid/Base:** Acidosis decreases K+ channel permeability, inhibits Na+/K+ ATPase (hence decreasing K+ secretion) Alkalosis increases K+ secretion through stimulation of Na+/K+ ATPase and K+ channels **Luminal factors:** Distal tubular flow rate washes away luminal K+ hence increasing K+ secretion Increased Na+ in DCT, more Na+ absorbed hence more K+ loss

Answer 28

Active process Uptake via H+/K+ ATPase

Answer 29

[K+] = \>5.0mmol/l

Answer 30

Problems with external balance **Increased intake:** Only causes problem when there's renal impairment Unless there has been an inappropriate dose given IV **Inadequate renal excretion**

Answer 31

**AKI** **Chronic kidney injury** **Reduced aldosterone (with normal kidneys):** Adrenal insufficiency Aldosterone blockers (secretion or action) K+ sparing diuretics ACE Inhibitors

Answer 32

**Diabetic ketoacidosis:** No insulin reduces K+ intake into ICF Plasma hypertonicity (Causes shift of K+ into ECF) Metabolic acidosis causes reciprocal shift of K+ into ECF as H+ moves into ICF **Other causes of metabolic acidosis** **Cell lysis** **Exercise**

Answer 33

Raises the resting membrane potential (depolarisation) **Cardiac:** More Fast Na+ channels remain inactive and the heart is less excitable

Answer 34

**Heart:** Altered excitability - Arrhythmias, heart block **GI:** Neuromuscular dysfunction - Paralytic ileus **Acidosis**

Answer 35

**Symptoms worsen as [K+] rises as demonstrated by incresing numbers below** 1. High T wave 2. As above + Prolonged PR interval and depressed ST segment 3. P wave absent and intraventricular block 4. VFib

Answer 36

**Reduce K+ effect on heart:** IV calcium gluconate **Shift K+ into ICF:** Glucose + IV insulin Nebulised B agonists (salbutamol) **Remove excess K+:** Dialysis

Answer 37

**Treat cause** **Reduce intake** **Measures to remove excess K+:** Dialysis Oral K+ binding resins to bind K+ in gut

Answer 38

[K+] = \<3.5mmol/l

Answer 39

**Problems of external balance:** Excess GI loss (bulimia/vomiting) Excess renal loss (Diuretics, Osmotic diuresis - Diabetes, High Aldosterone) **Problems with internal balance:** Shift of K+ into ICF (Metabolic alkalosis)

Answer 40

Hyperpolarisation More fast Na+ channels active in cardiac muscle Cardiac muscle is more excitable

Answer 41

**Heart:** Altered excitability - Arrhythmias **GI:** Neuromuscular dysfunction - Paralytic Ileus **Skeletal muscle:** Neuromuscular dysfunction - Muscle weakeness **Renal:** Dysfunction of CD cells - Unresponsive to ADH causing nephrogenic diabetes insipidus

Answer 42

**Worsening degree of hypokalaemia indicated by numbers below:** 1. Low T wave 2. As above + High U wave 3. As above + Low ST segment

Answer 43

**Treat cause** **Potassium replacement (IV/Oral)** **If due to increase mineralocorticoid activity:** Potassium sparing diuretics which block action of aldosterone on principal cells