Hydrocarbons By Dr Sk - PowerPoint Presentation

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Hydrocarbons

By

Dr

Sk

Faizan

Ali

The term hydrocarbons has been used to represent compounds derived from petroleum distillation.1. Aliphatic Hydrocarbons (Paraffins)

These comprise compounds with saturated molecules (containing

no carbon-carbon double or triple bonds)

which have straight or branched-chain arrangements.

Common

examples

include

butane, ethane, methane, and propane (

gaseous) ;

benzine

, gasoline or petrol, diesel

oil,

kerosene

, mineral seal oil, lubricating oil or mineral oil, and turpentine or pine oil (

liquids) ;

paraffin wax, petroleum

jelly or

vaseline

, grease, tar, and asphalt (

semi-liquids

or

solids

).

2. Aromatic HydrocarbonsThey contain at least one benzene ring and are unsaturated compounds. Common examples include benzene, toluene and naphthalene.

3

.

Halogenated Hydrocarbons

Most of these are clear,

colourless

liquids which have a chloroform-like

odour

.

Common examples include carbon tetrachloride, ethylene

dibromide

, ethylene dichloride,

dichloroethylene

, trichloroethylene,

methylene

chloride, propylene chloride, chloroform, methyl chloroform, methyl bromide, fluorocarbons and

organochlorine

insecticides

.

4. Cycloparaffins (Naphthenes)They are saturated hydrogen compounds which are arranged in closed rings. Common examples include

cyclohexane

and

methylcyclopentane

.

5.

Alkenes (Olefins)

These compounds contain one carbon-carbon double bond in the molecule. They are mostly used in the manufacture of other hydrocarbon products such as halogenated hydrocarbons.

ALIPHATIC HYDROCARBONS

Uses

Mode of Action■ Ingestion of aliphatic hydocarbons with high molecular weight such as paraffin wax, vaseline, grease, etc. is associated with little or no toxicity.

■ Liquid hydrocarbons are the most toxic, but symptoms generally are the result of aspiration into the airways rather than absorption from the GI tract.

■ The aspiration potential of a hydrocarbon depends on 3 properties—

viscocity

, surface tension, and volatility.

Viscocity

:It

is measured in

Saybolt

Seconds Universal (SSU). The lower the

viscocity

(i.e. below 60 SSU), the higher the tendency for aspiration

.

Surface tension: The lower the surface tension, the higher the tendency for aspiration.Volatility: The higher the volatility, the higher the tendency for aspiration.

■ Aliphatic hydrocarbons possessing high aspiration potential include gasoline, kerosene, mineral seal oil, and turpentine.

Clinical FeaturesRS: Respiratory distress from aspiration usually begins within 30 minutes of exposure, and is manifested mainly by gasping, coughing, and choking. There are 3 grades:a. Mild : coughing, choking, tachypnoea

, drowsiness,

rales

,

rhonchi

.

b. Moderate : grunting, lethargy, flaccidity,

bronchospasm

.

c. Severe : cyanosis, coma, seizures.

Choking

Flaccidity

CNS: Lethargy with depressed sensorium. Coma and convulsions are rare. Aniline, heavy metals, camphor, pesticides and other additives or contaminants in hydrocarbon preparations may produce additional

CNS toxicity.

For instance, chronic

cerebellar

degeneration may be associated with lead additives of gasoline.

GIT:

Burning of mouth, sore throat, nausea, and vomiting.

Haematemesis

may occur.

Diarrhoea

is rare.

CVS:

Arrhythmias are seen in solvent abuse but are rare in ingestions.

Skin: Acute exposure can cause dermatitis, and if this is prolonged it may result in full thickness burns. Chronic exposure to kerosene can cause severe acne.Contact with liquefied petroleum gases (e.g. propane, butane, propylene, isobutane, butenes

, n-butane), ethane, etc. can result in frostbite or effects resembling frostbite

.

Haematologic

:

Disseminated intravascular coagulation,

haemolytic

anaemia

and

pancytopenia

have occasionally been reported following

vapour inhalation, aspiration, or ingestion of hydrocarbons.

Other effects:a. Elevated liver enzyme levels and hepatosplenomegalyb. Renal effects (acute renal tubular necrosis, proteinuria

, or

haematuria

) occur infrequently following acute exposure to petroleum distillates and other

unsubstituted

hydrocarbons.

c. Straight chain hydrocarbons with few

“c”

atoms (e.g. methane, ethane, propane gases) can cause asphyxiation if exposure occurs in poorly ventilated spaces

.

d. High-pressure injection

injuries can result in necrosis and thrombosis

with amputation required in 60 to 80% of cases.e. Exposure to hydrocarbons may result in the loss of colour

vision, with the risk of impaired colour

vision increasing

with increasing exposure.

DiagnosisX-Ray—Changes may be as early as 30 minutes after exposure and peak at about 72

hours,.Common

radiologic findings

include

bronchovascular

markings,

bibasilar infiltrates

, and pneumonic consolidation. Early

upright X-rays

may reveal two liquid densities in the

stomach (

double bubble sign), which represents two interfaces: air-hydrocarbon, and hydrocarbon-fluid.

a. They correlate poorly with clinical symptoms.

b. They lag behind clinical improvement.

2. Arterial blood gases—There is

hypoxaemia

.

3. Blood—Leucocytosis is common during the first 48 hours.

Treatment 1. The following signs and symptoms present for pneumonitisa. Lethargy,

rhonchi

,

rales

, retractions, cyanosis, and

the development

of

leukocytosis

and fever within 4 hours.

b. The only parameter with an 80% or greater

predictive value

for NO toxicity was the absence of

tachypnoea.c. Early chest X-rays were not useful in predicting pneumonitis.2. The immediate concern is the threat of respiratory failure. The following measures are

necessary if

respiration is compromised:

a.

Endotracheal

intubation.

b. Oxygen.

c. Continuous positive airway pressure or positive end-expiratory pressure. A recent innovation is high frequency jet ventilation (HFJV), utilising high respiratory rates (220 to 260) with small tidal volumes.Extracorporeal membrane oxygenaion (ECMO) is an effective option in severe pulmonary toxicity when all other

meaures

have failed.

d. Bronchodilators—preferably inhaled

cardioselective

drugs such as

salbutamol

.

3. Decontamination:

a. If there is suspicion of dermal exposure, all

clothing should

be removed and the skin washed with

copious amounts of soap and water, since significant toxicity can result from cutaneous absorption.b. Induction of vomiting is not recommended.

c. Stomach wash may be done cautiously after intubation.d. Activated charcoal is generally considered to be ineffective in adsorbing petroleum

distillates.

4. While prophylactic administration of corticosteroids

was advocated

in the past, it is not advocated

today.

5

. Similarly, prophylactic administration of antibiotics

which was

the norm in the past is also discouraged

today.

6. Crystalloid solutions must be administered judiciously.

Pulmonary artery monitoring may help. In general, the pulmonary artery wedge pressure should be kept relatively low while still maintaining adequate cardiac output, blood pressure

and urine output.

7. Treatment of frostbite:a. Rewarming—– Do not institute rewarming unless

complete

rewarming

can be assured; refreezing thawed

tissue increases

tissue damage

.

–

Correct systemic hypothermia.

–

Rewarming

may be associated with increasing pain requiring narcotic analgesics.b. Wound Care—– Digits should be separated by sterile

absorbent cotton; no constrictive dressings should be used.

–

Perform daily hydrotherapy for 30 to 45 minutes

in warm

water 400 Celsius.

– The injured extremities should be elevated and should not be allowed to bear weight.– Clear blisters should be debrided but haemorrhagic blisters

left intact.

– Further surgical debridement should be

delayed until

mummification demarcation has occurred (

60 to

90 days). Spontaneous amputation may occur.

– Analgesics may be required during the

rewarming

phase

; however, patients with severe pain should

be evaluated

for vasospasm. Arteriography and noninvasive vascular techniques (e.g. Doppler ultrasound, digital plethysmography, isotope scanning), have been

useful in evaluating the extent of

vasospasm after

thawing

.

– Tetanus prophylaxis as indicated.– Topical aloe vera should be applied every 6 hours.– Ibuprofen is a

thromboxane

inhibitor and may

help reduce

tissue loss. Adult dose of 200–400 mg

every 12

hours is recommended.

8.

Tar and asphalt can cause distressing problems of

a different

sort. These hot hydrocarbon mixtures can

produce

severe burns on dermal contact. The material hardens quickly and becomes extremely difficult to remove Thermal injury can be minimised by immediate cooling with cold water. Removal of hardened tar can be

attempted after

application of mineral oil, petroleum jelly, or

antibacterial ointment

. Recent reports suggest that

surface-acting agents

in combination with a hydrocarbon ointment may be more effective.