physiology Flashcards
Classses of hypovolemic shock
Blood loss ml <750ml 750-1500ml 1500-2000ml >2000ml
Blood loss % <15% 15-30% 30-40% >40%
Pulse rate <100 >100 >120 >140
Blood pressure Normal NormalDecreased Decreased
Respiratory rate 14-20 20-30 30-40 >35
Urine output >30ml 20-30ml 5-15ml <5ml
Symptoms Normal Anxious Confused Lethargic
anaphylactic shock treatment
Adrenaline Hydrocortisone Chlorpheniramine
< 6 months 150 mcg 25 mg 250 mcg/kg
6 months - 6 years 150 mcg 50 mg 2.5 mg
6-12 years 300 mcg 100 mg 5 mg
Adult and child 12 years 500 mcg (0.5ml 1 in 1,000) 200 mg 10 mg
nerve fibers transmission A B C
Slow transmission of mechanothermal stimuli is transmitted via C fibres.
A γ fibres transmit information relating to motor proprioception, A β fibres transmit touch and pressure and B fibres are autonomic fibres.
Peripheral nociceptors are innervated by either small myelinated fibres (A-delta) fibres or by unmyelinated C fibres.
The A gamma fibres register high intensity mechanical stimuli. The C fibres usually register high intensity mechanothermal stimuli.
Phases of gastric acid secretion
- Cephalic phase (smell / taste of food)
30% acid produced
Vagal cholinergic stimulation causing secretion of HCL and gastrin release from G cells - Gastric phase (distension of stomach )
60% acid produced
Stomach distension/low H+/peptides causes Gastrin release - Intestinal phase (food in duodenum)
10% acid produced
High acidity/distension/hypertonic solutions in the duodenum inhibits gastric acid secretion via enterogastrones (CCK, secretin) and neural reflexes.
gastric hormons
Gastrin
G cells in antrum of the stomach
Distension of stomach, extrinsic nerves
Inhibited by: low antral pH, somatostatin
Increase HCL, pepsinogen and IF secretion, increases gastric motility, trophic effect on gastric mucosa
CCK
I cells in upper small intestine
Partially digested proteins and triglycerides
Increases secretion of enzyme-rich fluid from pancreas, contraction of gallbladder and relaxation of sphincter of Oddi, decreases gastric emptying, trophic effect on pancreatic acinar cells, induces satiety
Secretin
S cells in upper small intestine
Acidic chyme, fatty acids
Increases secretion of bicarbonate-rich fluid from pancreas and hepatic duct cells, decreases gastric acid secretion, trophic effect on pancreatic acinar cells
VIP
Small intestine, pancreas
Neural
Stimulates secretion by pancreas and intestines, inhibits acid and pepsinogen secretion
Somatostatin
D cells in the pancreas and stomach
Fat, bile salts and glucose in the intestinal lumen
Decreases acid and pepsin secretion, decreases gastrin secretion, decreases pancreatic enzyme secretion, decreases insulin and glucagon secretion
inhibits trophic effects of gastrin, stimulates gastric mucous production
Cause of low magnesium
Diuretics
Total parenteral nutrition
Diarrhoea
Alcohol
Hypokalaemia, hypocalcaemia
causes and features of low magnesium
Diuretics
Total parenteral nutrition
Diarrhoea
Alcohol
Hypokalaemia, hypocalcaemia
Features
Paraesthesia
Tetany
Seizures
Arrhythmias
Decreased PTH secretion → hypocalcaemia
ECG features similar to those of hypokalaemia
Exacerbates digoxin toxicity
ST segment
Represents period which the entire ventricle is depolarized and roughly corresponds to the plateau phase of the ventricular action potential
Fluid compartment physiology
intracellular 28 L 60-65%
Extracellular 14 L 35-40%
Plasma 3 L 5%
Interstitial 10 L 24%
Transcellular 1 L 3%
SIADH causes
malignancy
especially small cell lung cancer
also: pancreas, prostate
Neurological
stroke
subarachnoid haemorrhage
subdural haemorrhage
meningitis/encephalitis/abscess
Infections
tuberculosis
pneumonia
Drugs
sulfonylureas
SSRIs, tricyclics
carbamazepine
vincristine
cyclophosphamide
Other causes
positive end-expiratory pressure (PEEP)
porphyrias
CSF circulation
Lateral ventricles (via foramen of Munro)
2. 3rd ventricle
3. Cerebral aqueduct (aqueduct of Sylvius)
4. 4th ventricle
5. Subarachnoid space (via foramina of Magendie and Luschka)
6. Reabsorbed into the venous system via arachnoid granulations into superior sagittal sinus
pancreas secretion
The cephalic and gastric phases (neuronal and physical) are less important in regulating the pancreatic secretions. The effect of digested material in the small bowel stimulates CCK release and ACh which stimulate acinar and ductal cells. Of these CCK is the most potent stimulus. In the case of the ductal cells these are potently stimulated by secretin which is released by the S cells of the duodenum. This results in an increase in bicarbonate.
secretion of different stomach cell type
Parietal cells: secrete HCl, Ca, Na, Mg and intrinsic factor
Chief cells: secrete pepsinogen
Surface mucosal cells: secrete mucus and bicarbonate
mg
Magnesium and calcium interact at a cellular level also and as a result decreased magnesium will tend to affect the permeability of cellular membranes to calcium, resulting in hyperexcitability.
jvp
hypokalemia due to vomiting
Hypokalaemia may occur in vomiting, usually as a result of renal wasting of potassium, not because of potassium loss in vomit.
diuretics types and actions
Site of action Diuretic Carrier or channel inhibited Percentage of filtered sodium excreted
Ascending limb of loop of Henle Frusemide Na+/K+ 2Cl - carrier Up to 25%
Distal tubule and connecting segment Thiazides Na+Cl- carrier Between 3 and 5%
Cortical collecting tubule Spironolactone Na+/K+ ATP ase pump Between 1 and 2%
leptin actions
Leptin stimulates the release of melanocyte-stimulating hormone (MSH) and corticotrophin-releasing hormone (CRH). Low levels of leptin stimulates the release of neuropeptide Y (NPY)
leptin actions
Leptin stimulates the release of melanocyte-stimulating hormone (MSH) and corticotrophin-releasing hormone (CRH). Low levels of leptin stimulates the release of neuropeptide Y (NPY)
causes of hyperuricemia
‘Can’t leap’
C iclosporin
A lcohol
N icotinic acid
T hiazides
L oop diuretics
E thambutol
A spirin
P yrazinamide
drug that cuases hyperkalemia
ACE inhibitors, angiotensin 2 receptor blockers, spironolactone, ciclosporin, heparin**( inhbition of aldostrone secretion)
ileostomy water loss and jobran
In some individuals a colectomy or similar procedure results in formation of an end or loop ileostomy. Ileostomies typically lose between 500 and 1000ml over a 24 hour period and patients with high output ileostomies can rapidly become dehydrated. Ileostomy effluent typically contains 126mmol/L of sodium and 22mmol/L of potassium. Knowledge of this fluid composition should guide fluid prescribing in replacing losses.
acidosis and uric acid
Decreased tubular secretion of urate occurs in patients with acidosis (eg, diabetic ketoacidosis, ethanol or salicylate intoxication, starvation ketosis)
hypercalcemia urgent findings and treatment
Calcium > 3.5 mmol/l
Reduced consciousness
Severe abdominal pain
Pre renal failure
Airway Breathing Circulation
Intravenous fluid resuscitation with 3-6L of 0.9% Normal saline in 24 hours
Concurrent administration of calcitonin will also help lower calcium levels
Medical therapy (usually if Corrected calcium >3.0mmol/l)
Normal Gap Acidosis: HARDUP
H - Hyperalimentation/hyperventilation
A - Acetazolamide
R - Renal tubular acidosis
D - Diarrhoea
U - Ureteral diversion
P - Pancreatic fistula/parenteral saline
Raised anion gap
Lactate: shock, hypoxia
Ketones: diabetic ketoacidosis, alcohol
Urate: renal failure
Acid poisoning: salicylates, methanol
refeeding syndrome
High risk for re-feeding problems
If one or more of the following:
BMI < 16 kg/m2
Unintentional weight loss >15% over 3-6 months
Little nutritional intake > 10 days
Hypokalaemia, Hypophosphataemia or hypomagnesaemia prior to feeding (unless high)
If two or more of the following:
BMI < 18.5 kg/m2
Unintentional weight loss > 10% over 3-6 months
Little nutritional intake > 5 days
History of: alcohol abuse, drug therapy including insulin, chemotherapy, diuretics and antacids
refeeding prescription
Prescription
Start at up to 10 kcal/kg/day increasing to full needs over 4-7 days
Start immediately before and during feeding: oral thiamine 200-300mg/day, vitamin B co strong 1 tds and supplements
Give K+ (2-4 mmol/kg/day), phosphate (0.3-0.6 mmol/kg/day), magnesium (0.2-0.4 mmol/kg/day)
hypokalemia and j and delta wave
U waves
Small or absent T waves (occasionally inversion)
Prolonged PR interval
ST depression
Long QT interval
J waves are seen in hypothermia whilst delta waves are associated with Wolff Parkinson White syndrome.
if someone needs blood
Up to 4 units of SAG M Blood may be administered. Thereafter whole blood is preferred. After 8 units, clotting factors and platelets should be considered.
ypokalemc acidosis and alkalosis
Hypokalaemia with alkalosis
Vomiting
Diuretics
Cushing’s syndrome
Conn’s syndrome (primary hyperaldosteronism)
Hypokalaemia with acidosis
Diarrhoea
Renal tubular acidosis
Acetazolamide
Partially treated diabetic ketoacidosis
gamma-irradiated blood products
patients at risk of transfusion associated GVHD
auses of increased anion acidosis: MUDPILES
M - Methanol
U - Uraemia
D - DKA/AKA
P - Paraldehyde/phenformin
I - Iron/INH
L - Lactic acidosis
E - Ethylene glycol
S - Salicylates
most important urinary buffer
phosphate
cardiac inotropes and vice versa
Glucagon and theophylline are also positive inotropes (although not commonly used for this purpose). In contrast sodium thiopentone causes marked myocardial depression.
septicemia with blood products
Platelets are stored at room temperature and must be used soon after collection. This places them at increased risk of culturing gram positive organisms. Iatrogenic infection with gram negative organisms is more likely with packed red cells as these are stored at 4 degrees.
Infections with blood products of this nature are both rare.
stress respond (after surgery) decreased in which hormones
Insulin
Testosterone
Oestrogen
main IL after surgery
IL-6 main cytokine associated with surgery. Peak 12 to 24 h after surgery and increase by the degree of tissue damage Other effects of cytokines include fever, granulocytosis, haemostasis, tissue damage limitation and promotion of healing.
