Metabolic Alkalosis
RS: shift Oxy-Hb curve to L (incr affinity of Hb for O2  tissue hypoxia); compensatory hypoventilation;
blunted resp response to incr CO2
Met: hypoK, hypoCa (causes symptoms), hypoCl  dizzy, chest tightness, anxiety, laryngospasm, tremor,
carpopedal spasm, Chovstek, Trousseau; decr lactate metabolism stimulates anaerobic glycolysis; incr production of
lactic acid and ketoacids
CV: arteriolar vasoC
NS: incr NH3 entry into CNS  hepatic encephalopathy; lethargy, confusion
pH 7.55  mortality rate 45%
pH 7.65  mortality rate 80%
Due to GI / renal loss of acid
XS alkali intake
Maintenance requires decr ability of kidney to excrete HCO3 (eg. Depletion of Cl)
Effects of
metabolic
alkalosis
Causes
Chloride sensitive: responds well to N saline
Cl and ECV loss  hypoV  Na reabsorption, K and H excretion  hypoCl (urinary Cl <10), hypoK, met
alkalosis
GI losses (most common cause in ED): Vomit (and pyloric stenosis), NGT drainage, Diarrhoea, Ileostomy,
villous adenoma, Cl wasting enteropathy, congenital chloridorrhea
Renal losses: post-diuretics (thiazide, loop)
Overdose of base (antacids, laxatives)
Post-hypercapnia; CF
Contraction alkalosis (fluid loss  decr renal perfusion  incr aldosterone  loss of H and reabsorption
of HCO3)
Chloride insensitive: not responsive to N saline resus
No hypoV; urinary Cl >10
Normotensive = Renal losses (Bartter’s, Gitelman’s, active diuretic trt in normotensive patients, severe
hypoK/Mg, hyperCa), Refeeding alkalosis
Overdose of base (milk-alkalai, massive blood/Hartmann’s transfusion, NaHCO3, Ural)
Hypertensive = Renal losses (active diuretic trt in hypertensive patients, Liddle syndrome, RAS, renal
failure)
Endocrine (hyperaldosteronism, adrenal Ca, adrenal hyperplasia, Cushings, exogenous
steroids, renin secreting tumour, licorice, chewing tobacco)
Compensation
Mng
Expected PaCO2 =
(0.9 x HCO3) + 9
Compensation may not be found if:
pain, hyperV due to pul congestion/hypoxaemia
If change in PaCO2 = change in HCO3, there is appropriate resp compensation
If PaCO2 too high, there is additional resp acidosis
If PaCO2 too low, there is additional resp alkalosis
Trt underlying cause; improve renal HCO3 excretion; O2; correct electrolyte imbalance; acetazolamide 250mg BD;
HCl rarely required
If vol deplete / Cl sensitive  give IVF
If vol overloaded / Cl insensitive  give spironolactone
Notes from:
METABOLIC ALKALOSIS:
(PC02 > 45, HCO3- , B.E. > +2)
Volume Depleted
Normal Volume or Volume Overload
(Urinary Cl < 10mmol/L)
(Urinary Cl > 15mmol / L)
1. Upper GIT losses.
2. Renal: Diuretics.
 Exception, current
diuretic treatment Cl is 
 Recently ceased
diuretics Cl is 
3. Skin loss (of NaCl)
1. Hyperaldosteronism
2. Cushings
3. Rare:
 Bartter’s syndrome.
 Severe K+ 