Antiemetics

Vomiting is controlled by the area postrema lying inferior and posterior to the 4th ventricle in the medulla. There is the chemoreceptor trigger zone (CTZ) and the vomiting centre. The vomiting centre receives afferents from GI (eg mucosal irritation), extra GI (eg bile duct and other organs), extra medullary (eg vestibular and olfactory systems) and CTZ. CTZ detects blood born toxins. 

Antiemetic antihistamines (H1): eg cyclizine, cinnarizine. Used in motion sickness and vestibular disorders.  Acts on vomition centre.

Dopamine 2 antagonists: eg domperidone and metoclopramide.  Act on CTZ. Note: domperidone does not cross BBB therefore no dyskinetic side effects.

Serotonin receptor antagonists: eg ondansetron. Used in nausea and vomiting especially associated with cytotoxic medication as they act on CTZ.

Anticholinergics: eg hyoscine. Effective in motion sickness and gastric irritation. Do not act on CTZ.

Phenothiazines: eg  chlorpromazine. Act mainly on D2 receptors. Can also block histamine and muscarinic receptors.  Commonly used in severe N&V associated with vertigo.

Eye movement and associated palsies

All muscles innervated by CN 3 (occulomotor) with the exception of. 

SO= CN 4 (trochlear)

LR = CN6  (Abducens)

Therefore:

3rd nerve palsy à eye looks down and out. *

4th nerve palsy à Pt will have diplopia which is maximal when looking downwards and inwards (action of SO).

6th nerve palsy à Most common isolated palsy. Eye deviated medially and diplopia maximal on lateral gaze.

* Third nerve also carries parasympathetic fibres around the outside. Therefore damage causes a fixed dilated pupil. A third nerve palsy with pupillary sparing is often termed a medical third palsy and often has an ischaemic or diabetic aetiology. Surgical third nerve palsies include tumours or PCA aneurysms.

Vascular territories of the brain and clinical features of stroke

                                                                    http://www.vetsci.co.uk/

ACA:  The ACA runs along the midline of the brain and supplies  medial part of the motor and sensory homunculus therefore occlusion may result in contralateral motor and sensory loss in the legs. Not common to get isolated ACA involvement. 

MCA:  Most commonly involved in strokes. Supplies motor and sensory cortex. In the dominant hemisphere it supplies Broca’s and Wernicke’s points (expression and comprehension of speech respectively). In the non dominant hemisphere it supplies visuospacial tasks. 

Therefore, clinical features include:

•Contralateral hemiplegia with relative sparing of the legs (ACA territory)

• UMN signs

•contralateral hemisensory loss

•aphasia if dominant hemisphere affected

• neglect and contralateral apraxia if non dominant hemisphere affected

PCA:  Arises from the basilar artery and  supplies midbrain, thalamus, temporal and occipital lobes.

 Clinical features include: thalamic syndrome (excessive pain), homonymous hemianopia with macular sparing,  contralateral hemiplegia,  hemisensory disturbance and dyskinesias.

Lacunar infarcts: Infarcts in important small vessels which supply structures such as the internal capsule which connects spinal cord to the cortex. Small infarcts can lead to significant damage such as contralateral hemiparesis.

Pleural effusion

PLEURAL EFFUSION

Symptoms:

·         Dyspnoea

·         Sometimes pleuritic pain

Signs

·         Decreased chest expansion on affected side

·         Stony dullness to percussion

·         Diminished breath sounds

·         Reduced tactile vocal fremitus

·         Branchial breathing can sometimes be heard at upper level of the fluid.

Cause: there is a disturbance of the normal fluid dynamics. The parietal pleura is perfused by systemic circulation and the visceral by pulmonary circulation. Fluid filtration into the pleural space is dependent on high systemic capillary pressure, negative intrapleural pressure and pleural oncotic pressure. Generally, fluid is filtered by the parietal pleura and absorbed by the visceral. An effusion can result from:

Increased capillary pressure: eg left ventricular failure

Reduced plasma oncotic pressure: eg hypoalbuminaemia

Increased capillary permeability: eg pleural disease

Obstruction of lymphatic drainage: eg carcinoma of lymphatics.

Transudates

Transudates have low protein (<30g/L) and lactate dehydrogenase (<200iu/L) CAUSED BY CHANGE IN HYDROSTATIC OR OSMOTIC PRESSURE. Examples:

·         Cardiac failure

·         Renal failure

·         Hepatic cirrhosis

·         Ascites (passing through pleuroperitoneal communications)

·         Hypoproteinaemia

·         Myxoedema

Exudates

Exudates have high protein content (>30g/L) and high lactate dehydrogenase (>200iu/L) CAUSED BY DISEASE OF THE PLEURA. Examples:

·         Malignancy (metastatic carcinoma / mesothelioma)

·         Infection (TB / parapneumonic / empyema)

·         Inflammation (SLE / RA / Dressler’s syndrome / Benign asbestos effusion / Rx eg dantrolene)

·         Subdiaphragmatic disease (subphrenic abscess, ascites, pancreatitis).

Investigations

·         CXR shows dense white shadow with concave upper edge, ‘meniscus sign’. Small effusion may require lateral decubitus film to show fluid mobility.

·         CT can be helpful in detecting underlying disease

  Aspiration

o   APPEARANCE

o   Should be straw coloured. Blood suggests malignancy, infarction or severe inflammation. Pus suggests empyema. Milky white suggests chylothorax and frank blood a haemothorax.

o   BIOCHEMISTRY

o    Transudate or exudate (protein / LDH)  

o   ↓glucose suggests infection or connective tissue disease

o   ↑Amylase = pancreatitis or adenocarcinoma

o   CYTOLOGY

o   Lymphocytes (TB / malignancy)

o   Neutrophils (infection / inflammation)

o   Look for malignant cells eg mesothelioma.

o   MICROBIOLOGY

o   TB / Bacteria

·         Biopsy with abram’s needle can be sent for histology (carcinoma / mesothelioma / TB) and microbiology (TB).

Treatment

Transudates à correct underlying cause such as heart failure, hypoproteinemia. Further investigation not usually necessary.

Exudates àmay require draining (no more than 2L daily) if symptomatic.  Can be aspirated with the diagnostic tap or a chest drain may be inserted.  Empyema should be drained with US guidance. Fibrinolytic agent may be used to improve drainage and remove adhesions. Recurrent malignant effusions can be treated with talc pleurodesis.

Drugs and Arthritis

Side effects of some common medications...

Statins: Headache, constipation or diarrhoea, dizziness, nausea, paraesthesia, nightmares, joint pain, memory loss, sexual dysfunction, hepatotoxicity, myositis, hypersensitivity reaction.

Long term steroids: Increase appetite, weight gain, mood changes, insomnia, fluid retention, osteoporosis, hypertension, diabetes, weight gain, infection, cataracts, glaucoma, thinning of the skin, purple striae, bruising, muscle weakness, adrenal insufficiency.

ACEi: Bradykinin cough, hypotension, hyperkalaemia, hepatotoxicity, renal impairment, angioedema, gynacomastia.

Beta-blockers: Bradycardia, bronchospasm, cold peripheries,  heart failure, impotence, headache, nightmares, depression, lethargy, reduced glucose.

Antiepileptic medication: Side effects can be divided into

1/Systemic eg. nausea and vomiting, rash, changes in bowel habit

2/Neurotoxic eg. drowsiness, lethargy

3/Drug specific

Following are some side effects unique to some of the more common drugs. They mostly fall under category 2 or 3 above.

Barbiturate (eg phenobarbital) à dependence and tolerance, sedation, behavioural changes and altered sleep cycles.

Carbamazapine à Blurred or double vision, agranulocytosis, aplastic anaemia, pancreatitis, hepatotoxic, stevens-johnson syndrome and serum sickness.

Ethosuxamide à sleep disturbance, drowsiness and hyperactivity

Gabapentin à ataxia, dizziness, somnolence

Lamotrigine à Gingival hypertrophy, hirsutism, lymphadenopathy, slurred speech, double vision, ataxia, osteomalacia, confusion

Sodium valproate à weight gain, hair loss, tremor, tiredness, pancreatitis, thrombocytopenia, liver failure (in children < 2). Bone loss, menstrual irregularity and PCOS seen in long term use.

Now for some radiological features: OA Vs. RA

Osteoarthritis

                 




                         Patient.co.uk                                                                        Revolutionhealth.com

I use the mnemonic NOCS (narrowing, osteophystes, cysts and sub. art. sclerosis)

Rheumatoid arthritis 

                                                                    emedicine.com

• Soft tissue swelling
• juxtaarticular Osteoporosis
• Narrowing of joint space
• Bone Erosions

Mnemonic: SONE

Parkinson's and Heart failure

OK, so the first random topic throws us deep into the basal ganglia where a host of forgotten nuclei diligently labour over our every move....

Parkinson’s disease

Idiopathic parkinson's disease is the most common of the akinetic-rigid syndromes characterised by degeneration of the basal ganglia. Other types include multiple system atrophy (shy-drager syndrome) and progressive supranuclear palsy.

·         Incidence ↑ with age (>1% in >60s), M=F

·         Pathologically there is a loss of pigmented neurones in substantia nigra and locus caeruleus and a degeneration of the dopaminergic pathway.

·         Aetiology: Idiopathic. However, less common in smokers. Dopamine receptor antagonists (eg antipsychotics and antiemetics) can precipitate parkinsonian features.

·         Clinical triad of bradykinesia, rigidity (cogwheeling in wrists and leadpipe limbs) and tremor (resting, 4-6Hz).  This is initially asymmetrical but progressive.

·         1/3 of patients develop cognitive impairment.

·         Examination reveals expressionless face, monotonous speech, flexed posture, festinating gate, no arm swinging, rigidity, bradykinesia, tremor and micrographia.

·         Diagnosis is clinical. Consider copper studies to exclude Wilson’s disease in <50s. CT/MRI indicated if suspicion of secondary disease eg tumours / ischaemic damage.

·         Tx: Levodopa + peripheral decarboxylase inhibitors (carbidopa) to avoid peripheral dopamine side effects such as nausea, vomiting, arrhythmias.

·         Other medication includes anticholinergics, dopamine agonists, amantadine, selegiline, monoamine oxidase inhibitors and COMT (catechol – O – methyltransferase) inhibitors.

·         Progressive increase in frq of levodopa is required. Dyskinesia is an important side effect and patients may alternate between parkinsonian and dyskinetic states (“on-off” fluctuation).

·         Surgical ablation or deep brain stimulation is an option if medical therapy fails.

·         Prognosis. The disease is slowly progressive. Onset in middle age is likely to shorten lifespan. However, not likely to shorten lifespan or become severe if onset > 70.

Heart failure

Something a bit lighter now... radiological features of heart failure:

·         Cardiomegaly (cardiothoracic ratio > 50%)

·         Alveolar oedema giving ‘bat wings’ appearance

·         Bilateral pleural effusions

·         Diversion of vasculature to upper lobes

·         Kerley B lines (peripheral linear opacities)

                                                             From ultramedicine.co.uk