Portal flow decreased in all inhalation anesthetics which of them decreased portal flow most:-
1. Most anaesthetics decreases portal blood flow because of decreased cardiac output
2. total hepatic blood flow(THBF) = portal blood flow(PBF) + hepatic artery blood flow (HABF)
3. THBF, PBF, HABF is most markedly decreased by halothane than with any other inhalational agent.
4. Halothane also reduces hepatic oxygen delivery and hepatic venous oxygen saturation.
5. Halothane disturbs autoregulatory mechanism of liver that is hepatic artery buffer response.
a. Excreted unchanged in lungs b. Auto Regulation Blunted
c. No analgesiad. Tissue: Blood ratio is maximum in fat
e. Dissolves rubber f. Trichloracetic acid is found in urine
g. Drager Narco test is done for halothane
6. Causes dilation of:
7. Physical Properties
a. Colourless liquid volatile agent
b. Pleasant to smell
c. Stored in amber colour bottles (to prevent decomposition by light 0.01% thymol also added)
d. Non inflammable e. Non explosive f. Non irritant
g. stabilize by thymol (Preservative) and amber coloured bottle,
8. For Induction - 2-4% Maintenance - 0.5 to 2%
9. MAC - 0.74%
Blood gas coefficient - 2.4
10. Metabolism - 20% is metabolized , main metabolites - Trifluroacetic acid (TFA)
i. ↓C.O (Cardiac output)
iii. Direct depression of myocardium
v. Sensitizes heart to ADRENALINE (both exogenous & endogenous) arrhythmias like
Ventricular Extrasystoles, Ventricular - tachycardia & Ventricular fibrillation may occur
IMPORTANT: Halothane usually causes sinus or nodal bradycardia which is reversed by atropine.
12. Malignant Hyperthermia
a. Potent anaesthetic
b. Not a good analgesic
c. Muscle relaxation - moderate.
NOTE: Most commonly implicated drugs in malignant hyperthermia are:
1. Halothane (MCQ)
2. Suxamethonium (MCQ)
• Treatment of choice for malignant hyperthermia is intravenous dantrolene. (MCQ)
14. Respiratory system
a. Resp. depressant
b. µ tidal volume frequency
c. BRONCHODILATION - This is due to inhibition of reflexes pathways for bronchoconstriction
IMPORTANT: Halothane tends to accentuate perfusion-ventilation mismatch in lungs by causing vasodilatation in hypoxic alveoli. (MCQ)
a. Can cause uterine atony & PPH
b. Agent of choice for version & manual removal of placenta
a. Halothane hepatitis , causes centrilobular hepatitis necrosis.
b. Incidence of massive hepatic necrosis 1:35,000 patients predisposed to halothane hepatitis- middle age, female, obese, preexisting liver disease, previous exposure to halothane within 6 months
c. MOA --
i) Directly hepatocellular (its metabolite causes direct injury), or
ii) Immunologic (more acceptable theory now)
iii) Blood supply to liver
So, guidelines are
i. Avoid repeated administration at frequent interval (say 3 months)
ii. Pre- existing liver disease is not an absolute C/I, but use cautiously in acute liver diseases.