Osmotic diuretics

An osmotic diuretic is a type of diuretic that inhibits reabsorption of water and sodium. They are pharmacologically inert substances that are given intravenously. They increase the osmolarity of blood and renal filtrate.

Mechanism(s) of Action

1.    Reduce tissue fluid (edema) 
2.    Reflex cardiovascular effect by osmotic retention of fluid within vascular space which increases blood volume (contraindicated with Congestive heart failure) 
3.    Diuretic effect

o    Makes H2O reabsorption far more difficult for tubular segments insufficient Na & H2O capacity in distal segments
o    Increased intramedullary blood flow (washout)
o    Incomplete sodium recapture (asc. loop). this is indirect inhibition of Na reabsorption (Na stays in tubule because water stays) 
o    Net diuretic effect: 
    Tubular concentration of sodium decreases 
    Total amount of sodium lost amount increases 
    GFR unchanged or slightly increased

Toxicity

Circulatory overload, dilutional hyponatremia,  Hyperkalemia, edema, skin necrosis

Agents
Mannitol

Mefenamic acid

Analgesic, anti‐inflammatory properties less  effective than aspirin 

Short half‐lives, should not be used for longer  than one week and never in pregnancy and in  children. 

Enhances oral anticoagulants

Used to treat pain, including menstrual pain. It decreases inflammation (swelling) and uterine contractions.

A. Sympathetic Nervous System Depressants

1. Antagonists

Both α-adrenoceptor antagonists and β-adrenoceptor antagonists are useful  antihypertensives.

• α-blocker                     Prazosin, phentolamine, phenoxybenzamine
• β-blocker                     Propranolol ,Metoprolol, atenolol
• α/β-blocker                  labetalol

2. Sympathetic depressants

a. Examples of peripherally acting agents include

• reserpine This agent interferes with the storage of norepinephrine
• quanethidine This agent interferes with the release of norepinephrine
• trimethaphan This agent blocks transmission through autonomic ganglia.

b. Examples of Centrally acting agents include

• alphamethyldopa
• clonidine. These agents act by decreasing the number of impresses along sympathetic nerves.

Adverse Effect

include nasal congestion, postural hypotension, diarrhea, sexual dysfunction, dry mouth. sedation and drowsiness.

B. Directly Acting Vasodilators

Act on vascular smooth muscle cells independently of adrenergic nerves and adrenergic receptors.

Relaxation of vascular smooth muscle which leads to a decrease in peripheral vascular resistance.

Sites of action of vasodilators are many. For example

 Calcium Channel Blocker’s  MOA

. Decrease automaticity & conduction thru SA & AV nodes

. Decreased myocardial contractility

. Decreased peripheral & coronary 

smooth muscle tone = decrease SVR

Potassium channels activators

minoxidil, cause vasodilation by activating potassium channels in vascular smooth muscle.

An increase in potassium conductance results in hyperpolarization of the cell membrane which is associated with relaxation of smooth muscle.

Nitrovasodilators, such as sodium nitroprusside,

Increase in intracellular cGMP. cGMP in turn activates a protein kinase. Directly-Acting Vasodilators are on occasion used alone but more frequently are used in combination with antihypertensive agents from other classes (esp. a β-blocker and a diuretic.)

Needle selection

Nerve blocks:

Inferior alveolar- 25 G short (LLU technique)

PSA- 25 G short

Mental/Incisive- 25 G short

Palatal- 27/30 G short/ultrashort

Gow-Gates/Akinosi- 25 G long

Infraorbital- 25 G long

Field Block:

ASA 25/27 short

Infiltration:

Infiltration/SP 25/27 short

PDL/Intraosseous

PDL 27/30 short

Intraosseous 30 short/ultrashort

Oxytetracycline

Treats Oxytetracycline is a medicine used for treating a wide range of infections including infections of the lungs, urinary system, skin and eyes. It may also be used to treat sexually transmitted infections, infections caused by lice, rickettsial infections, cholera and plague. It is very occasionally used to treat leptospirosis, gas gangrene, and tetanus.

Nitrous Oxide (N2O)

MAC 100%, blood/gas solubility ratio 0.47
- An inorganic gas., low solubility in blood, but greater solubility than N2
- Inflammable, but does support combustion.
- Excreted primarily unchanged through the lungs.
- It provides amnesia and analgesia when administered alone.
- Does not produce muscular relaxation.
- Less depressant to both the cardiovascular system and respiratory system than most of the other inhalational anesthetics.
- Lack of potency and tendency to produce anoxia are its primary limitations.
- The major benefit of nitrous oxide is its ability to reduce the amount of the secondary anesthetic agent that is necessary to reach a specified level of anesthesia.