Pesticides and insecticides

 Pesticides vs Insecticides

Pesticides

Pesticides are substances used to prevent, destroy, repel, or control pests.

The term "pest" includes:

Insects

Weeds

Fungi

Rodents

Mites

Nematodes

Other harmful organisms

Thus, pesticide is a broad umbrella term.

Insecticides

Insecticides are pesticides specifically designed to kill or control insects.

Therefore:

All insecticides are pesticides

Not all pesticides are insecticides

Classification of Pesticides

1. Insecticides

Used against insects.

Examples:

Malathion

Parathion

Chlorpyrifos

Permethrin

Cypermethrin

DDT

2. Herbicides

Used against weeds and unwanted plants.

Examples:

Glyphosate

Paraquat

Atrazine

2,4-D

3. Fungicides

Used against fungi.

Examples:

Mancozeb

Copper sulfate

Carbendazim

Fluconazole (agricultural use is uncommon)

4. Rodenticides

Used against rats and mice.

Examples:

Zinc phosphide

Warfarin

Brodifacoum

5. Acaricides

Used against mites and ticks.

Examples:

Amitraz

Dicofol

6. Nematicides

Used against nematodes.

Examples:

Aldicarb

Carbofuran

7. Molluscicides

Used against snails and slugs.

Examples:

Metaldehyde

Niclosamide

Classification of Insecticides

A. Based on Chemical Class

1. Organophosphates

Mechanism:

Inhibit acetylcholinesterase

Examples:

Malathion

Parathion

Chlorpyrifos

Diazinon

Clinical features:

Cholinergic crisis

SLUDGE syndrome

Miosis

Bronchorrhea

2. Carbamates

Mechanism:

Reversible acetylcholinesterase inhibition

Examples:

Carbaryl

Propoxur

Aldicarb

3. Pyrethroids

Mechanism:

Prolong sodium channel opening

Examples:

Permethrin

Cypermethrin

Deltamethrin

Features:

Relatively safer in humans

Paresthesias common

4. Organochlorines

Mechanism:

Alter sodium channel function

Examples:

DDT

Lindane

Endosulfan

Features:

Neurotoxicity

Environmental persistence

5. Neonicotinoids

Mechanism:

Nicotinic acetylcholine receptor agonists

Examples:

Imidacloprid

Thiamethoxam

P pulmonale and mitrale

P pulmonale 

Ecg - Tall, peaked, and sharp P waves.

Criteria: Amplitude >2.5mm in inferior leads(Lead 2, 3 aVF), >1.5mm in leads V1 and V2.

P Mitrale

ECG-Broad, notched, or "bifid" (camel-hump-like) P waves

Criteria -P wave duration > 110 ms with a distinct notch in Lead II, and a wide, deep terminal negative component in lead V1

Cough Reflex and Neural Control

Cough Reflex and Neural Control

- Rapidly Adapting Receptors: Located in the epithelial and submucosal layers of the larger airways, these receptors produce cough and laryngeal narrowing in response to stimuli like dust, ammonia, histamine, and increases in inspiratory airflow.

Bronchial C Receptors: Located in the airway wall, these receptors project centrally through unmyelinated fibers and produce a cough when activated by capsaicin or bradykinin.

 Upper Airway Receptors: Receptors located in the pharynx initiate the cough reflex when stimulated by cold air.

 Afferent Pathway: Afferent signals originating from lung mechanoreceptors travel via the vagus nerve.

Cough Centre (Central Processing):

 *While a singular "cough centre" is not explicitly named, afferent signals from the peripheral receptors enter the pontomedullary network of the brain stem.

 * Sensory signals specifically terminate in the nucleus of the solitary tract (nTS), which is situated within the dorsal respiratory group (DRG).

 * This sensory input is processed by the respiratory central pattern generator (rCPG), a neuronal network in the central nervous system responsible for generating and modulating respiratory motor acts.

Efferents (Motor Output):

 * Neural output from the rCPG central controller drives the activity of specific motor neuron pools to execute the physical cough.

 * Efferent signals travel to brain stem motor neurons that innervate and control upper airway muscles.

 * Efferent signals also project to spinal motor neurons (phrenic, intercostal, and lumbar) to drive the respiratory pump muscles necessary for expulsion.

Cardiac asthma, renal asthma and uremic lung

 Cardiac asthma

Cardiac asthma is wheezing, cough, and breathlessness caused by left heart failure, especially acute LV failure, rather than primary bronchial asthma.

Mechanism

Left ventricular dysfunction → ↑ left atrial pressure → pulmonary venous congestion → interstitial edema around bronchioles → airway narrowing and reflex bronchoconstriction.

Clinical features

Paroxysmal nocturnal dyspnea

Orthopnea

Wheeze (“cardiac wheeze”)

Basal crackles

Pink frothy sputum in severe pulmonary edema

Often elderly with hypertension/CAD/valvular disease

Renal asthma

Renal asthma is an older clinical term describing paroxysmal dyspnea/wheezing due to pulmonary congestion from renal failure, usually because of:

Fluid overload

Severe hypertension

Heart failure secondary to kidney disease

Essentially, it is a form of cardiogenic pulmonary edema precipitated by renal dysfunction.

Pathophysiology

Renal failure → sodium and water retention → volume overload → pulmonary venous hypertension → pulmonary edema → wheeze and dyspnea.

Typical setting

Advanced CKD

Acute kidney injury with fluid overload

Missed dialysis

Important point

“Renal asthma” is not true asthma; it is pulmonary edema from renal disease.

Uremic lung

Uremic lung refers to pulmonary edema occurring in severe uremia/advanced renal failure, classically before dialysis era.

Pathogenesis

Combination of:

Fluid overload

Increased pulmonary capillary permeability due to uremic toxins

LV dysfunction/hypertension

Reduced oncotic pressure (sometimes)

Pathology

Interstitial and alveolar edema

Fibrinous alveolar exudates may occur

Clinical features

Severe dyspnea

Tachypnea

Hypoxemia

Crackles

Sometimes wheeze

Imaging

Classic chest X-ray:

Bilateral perihilar fluffy opacities

“Bat-wing” or “butterfly” pattern

May resemble cardiogenic pulmonary edema.

Management

Urgent dialysis

Oxygen/NIV if needed

Fluid removal

Treat hypertension and heart failure

Relationship between the three

Cardiac asthma → pulmonary edema from heart failure causing wheeze.

Renal asthma → pulmonary edema from renal disease/volume overload causing wheeze.

Uremic lung → pulmonary edema and lung injury specifically associated with severe uremia.

So, renal asthma and uremic lung overlap substantially, while cardiac asthma emphasizes the wheezing phenotype from heart failure.

dyspnea aggregating factors

Common aggravating factors:

Physical exertion, like walking or climbing stairs.

Supine position, especially if orthopnea is present

Environmental triggers, such as smoke, dust, pollution, cold air, or allergens.

Respiratory infections or worsening bronchospasm.

Anxiety or panic, which can intensify the sensation of breathlessness.

Anemia

obesity, and poor fitness, which can reduce exercise tolerance and worsen symptoms 

CNS - Cardinal symptoms

Cardinal symptoms of CNS

1. Syncope

2.Dizziness

3.vertigo

4.Fatigue

5.Muscke weakness and paralysis

6.numbness

7.Tingling sensation 

8.sensory loss

9.Gait disorder 

10.Imbalance and fall

11.confusion

12.delirium

13.coma

14.dementia

15.aphasia, dysarthria

16.memory loss

17.headache

18.sleep disorders.

Hantavirus pulmonary syndrome

Hantavirus Pulmonary Syndrome (HPS) is an acute febrile illness (i.e., temperature greater than 101.0 F [greater than 38.3 C]) with a prodrome consisting of fever, chills, myalgia, headache, and gastrointestinal symptoms,and one or more of the following clinical features: Bilateral diffuse interstitial edema, or

- Clinical diagnosis of acute respiratory distress syndrome (ARDS), or

- Radiographic evidence of noncardiogenic pulmonary edema, or

- An unexplained respiratory illness resulting in death, and includes an autopsy examination demonstrating noncardiogenic pulmonary edema without an identifiable cause, or

- Healthcare record with a diagnosis of hantavirus pulmonary syndrome, or

- Death certificate lists hantavirus pulmonary syndrome as a cause of death or a significant condition contributing to death

Laboratory Criteria For Diagnosis

- Detection of hantavirus-specific immunoglobulin M or rising titers of hantavirus-specific immunoglobulin G, or

- Detection of hantavirus-specific ribonucleic acid in clinical specimens, or

- Detection of hantavirus antigen by immunohistochemistry in lung biopsy or autopsy tissues

Pleuritic chest pain - features

 Pleuritic Chest Pain — Classical Features

Pleuritic chest pain is pain arising from irritation/inflammation of the parietal pleura. It has a characteristic clinical profile:

Key Features

Sharp, stabbing pain

Often described as “knife-like” or “catching”

Worsens with respiration

Increased by:

Deep inspiration

Coughing

Sneezing

Yawning

Laughing

Localized pain

Patient can often point with one finger to the painful area

Sudden onset is common

Especially in conditions like pneumothorax or pulmonary embolism

Reduced by shallow breathing / splinting

Patients avoid deep breaths because of pain

May radiate

To shoulder or neck if diaphragmatic pleura involved (via phrenic nerve)

Associated pleural rub

A scratching/grating sound on auscultation in pleuritis

Subpulmonic effusion -Radiological sign

Radiological Signs (Erect Chest X-ray):

1.Pseudodiaphragm Appearance: The dome of the diaphragm appears elevated, often creating a smooth, "flatter" contour.

2.Lateral Diaphragmatic Peak: The peak of the diaphragm is displaced laterally rather than being in the middle, creating a "hump".

3.Increased Left Lung-Gastric Bubble Distance: On the left side, the distance between the lung base and the stomach bubble (air-fluid interface) is increased, usually > 2cm

SURFACE ANATOMY

Apex: lung apex and pleural cupola extend about 2–3 cm above the medial third of the clavicle into the root of the neck. 

Anterior margin (right): follows the right side of the sternum from about the 2nd to the 4th costal cartilages then slopes laterally to reach the 6th right costal cartilage. 

Anterior margin (left): similar but deviates laterally to form the cardiac notch and reaches approximately 3 cm lateral to the left sternal edge at the upper margin of the 6th costal cartilage (the cardiac notch produces the lingula). 

Inferior margins (costal landmark lines)

Mid-clavicular line: inferior border of lung at 6th rib (pleural reflection ~2 ribs lower). 

Mid-axillary line: inferior border of lung at 8th rib. 

Posteriorly (paravertebral): inferior border reaches roughly the 10th rib/vertebral level. 

Note: the parietal pleura extends ~2 ribs lower than the lung at these points, creating the costodiaphragmatic recess.