NUR2030 MED./SURG. 2 NURSING REVIEW ENDOCRINE DISORDERS The Thyroid: The hollow follicles of this gland store thyroxine (or T4, plus some T3) made by the follicle walls. Iodine is present in these hormones so lack of it leads to hypothyroidism. Production and release of T4 is caused by TSH (anterior pituitary). Thyroid hormones increase metabolism but strong plasma binding means thyroxine therapy is long-lasting. Negative feedback control of TSH release by T4 levels occurs. Hyperthyroidism is characterised by goitre, increased body temperature, exophthalmos (Graves' disease), tremor, weight loss, tachycardia, weakness/fatigue and emotional lability. It can be due to a thyroid tumour but usually is caused by an autoimmune antibody which causes TSH-like stimulation of the thyroid. On the other hand, hypothyroidism involves weight gain, poor appetite, cold sensitivity, bradycardia and low BP, facial oedema, and depression. It is seen in iodine deficiency (as a goitre), after thyroidectomy (without follow-up HRT), and when Hashimoto's thyroiditis (also autoimmune) destroys the thyroid. If partial thyroidectomy is necessary, the patient needs prior assessment and education as well as conversion to the euthyroid state (to lower the risk of thyroid storm due to a sudden change in negative feedback (?) and post-op. bleeding) before the surgery is performed. The operation is not without risks and common complications include laryngeal nerve damage (vocal and swallowing problems), metabolic changes, hypocalcaemia. Acute infections are another cause thyroid storm, which involves chest pain and shortness of breath, atrial fibrillation and congestive heart failure, restlessness and delirium, tremor, psychosis, flushing and sweating. There is a need for follow-up blood T4 estimations to ensure the patient is not developing myxoedema, which will be treated by thyroxine (Oroxine) therapy, probably for life. The parathyroids are embedded in the thyroid and often are lost during thyroidectomy. They rarely malfunction otherwise. They secrete PTH which raises the blood Ca++ level, mainly by osteoclastic dissolution of the bones. Hence, hyperparathyroidism or presence of a tumour that secretes PTH- related protein can weaken the bones, the high blood Ca++ levels causing kidney stones, polyuria and neurological disturbances. Conversely, loss of the parathyroids means low blood Ca++ levels with tetanic cramping, emotional instability, and cardiac problems. The pituitary gland is in a bony pocket in the skull floor and is functionally linked to the hypothalamus. It secretes at least 8 hormones, including growth-regulating (trophic) hormones like GH, TSH and ACTH and also the water-conserving hormone, ADH, the lack of which leads to diabetes insipidus. Control of secretion of the pituitary gland is mostly by a form of negative feedback. 2 Pituitary adenomas that overcrowd the pituitary space and expand upwards interfere with hormone output and brain functions. Tumours that produce pituitary ectopic ACTH and ADH also are possible. Congenital pituitary defects can influence body development and in Cushing's disease the pituitary produces an excess of ACTH. The adrenal glands have a cortex that secretes cortisol (which like synthetic corticosteroids raises the blood glucose level, mobilises body fat, and helps the body survive stress while inhibiting immune responses and wound healing), aldosterone (which conserves Na+ and promotes loss of K+), and androgens for body growth. Important disorders are Cushing's syndrome (which is like Cushing's disease and leads to the classic 'moon' face, body fat redistributions, muscle wasting, hyperglycaemia, and impaired healing and infection control) due to primary adrenocortical hypersecretion, Addison's disease (primary adrenocortical failure, with bronzing of the skin due to excess ACTH secretion), and phaeochromocytoma (a malignancy of the medulla, leading to excessive adrenaline output and a hypertensive crisis). The adrenal glands sometimes develop severe internal haemorrhage associated with meningitis (and other disorders) - the usually lethal Waterhouse-Friderichsen syndrome. Prior to surgery Cushing's syndrome, problems are reduced by avoiding trauma/infections and encouraging rest. Monitoring for post-op. Addisonian crisis (hypotension, rapid breathing and extreme weakness) is also necessary. NEUROLOGICAL DISORDERS The CNS comprises the brain stem and spinal cord. The cerebrum and cerebellum receive and transmit only through the brain stem. The input pathways involve 1st, 2nd, and 3rd order neurons and the output pathways have an upper and a lower motor neuron. Reflex controls can be purely spinal or use the involuntary (autonomic and postural responses) and cortical (voluntary) brain areas. The corticospinal tract passes down from the motor cortex through the internal capsule (often damaged in cerebral palsy) then the medullary pyramids, where decussation occurs (significant in CVA cases). Cognitive activities reside in the cerebrum, though the level of consciousness (LOC) depends on the RAS of the upper brain stem. Depending on the type and severity of disturbance to this part of the brain, the patient may exhibit, confusion, delirium, coma, seizures, etc. Association areas are needed for full understanding of perceived sensory input, and the memorising role of the hippocampus as well as the behavioural bias of the rest of the limbic system plus the prefrontal cortex (tact) all contribute to the intellectual prowess (the left hemisphere especially). Disturbances of these cognitive areas lead to amnesia, aphasia, agnosia, psychoses, and dementia (notably the Alzheimer, aged, and alcoholic types). Of course, some altered cognition is due to sensory receptor problems, as in diabetic retinopathy, tinnitus, and Meniere's disease (vertigo and nausea). 3 The cerebral blood supply is critically important and involves the vertebral and internal carotid arteries, which join at the base of the brain as the circle of Willis, the common site of potentially catastrophic berry aneurysms. Anterior, middle and posterior cerebral arteries (and some lesser vessels) then supply different parts of the brain. When the brain is damaged, the specific area involved can often be determined by noting the pattern of signs/symptoms that results, though coup - contre coup damage (the other side of the brain) is possible. CT, MRI, angiography, EEG studies, and lumbar puncture (notably for meningitis) help evaluate the damage. The cerebral blood supply is 800 mL blood/min (autoregulated) at a BP of only 80 mm Hg. Increased intracranial pressure due to haemorrhage (epidural or subdural and secondary to head trauma, hypertension or a burst aneurysm), a tumour, or hydrocephalus compromise cerebral perfusion and reduce the LOC. Thromboemboli in the brain have the same effect and the CVA term is used for most of these disorders. The brain tolerates hypoxia for only brief intervals then infarction, necrosis, coma and death occur. The Glasgow Coma Scale uses eye responses: 1-4, responses to verbal stimuli: 1-5, and motor responses 1-6; 3-7 means brain death or at least coma. The earliest sign of raised ICP is often a reduced LOC due to cerebral ischaemia, and the systemic BP is unchanged increased decreased as the ICP rises. Low cerebral perfusion first causes Cushing's response (i.e. increased arterial pressure - protective) then Cushing's triad (i.e. bradycardia, hypertension, and bradypnoea - terminal changes). LOC reduction leads to confused, comatose, and coma states. Increased ICP is always an emergency situation and to minimise its effects the patient's head should be slightly raised in the 'neutral' position (no neck twisting) to encourage venous drainage. Some important terms associated with the effects of CVAs and other CNS disturbances are apraxia, dyspraxia, aphasia, dysphagia, hemiparesis, hemiplegia, hemianopia, paralysis (flaccid or spastic), ataxia, akinesia, bradykinesia, epileptic seizure, decorticate and decerebrate rigidity, and spinal shock with subsequent areflexia then hyperreflexia. Where the brain stem is damaged loss of the consensual pupil reflex or the presence of fixed dilated pupils are ominous signs. CVAs and other trauma-related CNS changes are mostly difficult to treat effectively so management is aimed at reducing the risk of complications and at rehabilitating the patient e.g. spinal damage above C4 means quadriplegia and no spontaneous breathing. People sometimes recover fully from CVAs but the final outcome remains uncertain for 8 weeks to 2 years. The ability of CVA patients to cope with lost abilities also needs to be dealt with by counselling and other techniques. A TIA (which is temporary with no long-term effects) and the perinatal brain damage that results in cerebral palsy (CP) have manifestations somewhat similar to those for CVAs. 4 Cerebrospinal fluid (CSF) is made from blood in the choroid plexus of the brain ventricles at 150 mL per 4 h and must flow out into the meninges and be reabsorbed there at the same rate to avoid non- communicating hydrocephalus or raised ICP. In an infant this causes swelling of the skull as well as brain compression. It is surgically controlled by the fitting of a shunt tube to take the CSF down into the trunk. The most serious form of meningitis is due to bacteria like Neisseria meningitidis and involves headache, fever, a rash, neck stiffness and photophobia. It must be treated aggressively with antibiotics and vaccinations. Degenerative disorders of the brain: Apart from Huntington's disease (inherited; progressive but mid-life start; dementia and choreiform movements), Alzheimer's disease, and motor neurone disease (idiopathic; most common in later years; rapidly progressive failure of both upper and lower neurons leading quickly to death from muscle atrophy), the major examples are Parkinson's disease and multiple sclerosis. Parkinson's disease is due to idiopathic loss of dopamine supplies in the basal ganglia, leading to a resting tremor and altered postural muscle tone. Levodopa therapy is helpful, though it may accelerate the degeneration of the substantia nigra and so is delayed as long as possible. Coping strategies in regard to postural and motility losses are also important. MS is an autoimmune disease that involves replacement of CNS white matter with scar tissue. It is sometimes relentlessly progressive but usually has alternating exacerbations and remissions. Most early signs and symptoms of MS are sensory (visual) but fasciculations, nystagmus, intention tremor, dysphagia and disturbed intellect eventually occur. MS is incurable but mostly progresses slowly and medications such as corticosteroids can slow it further. Death may be due to pneumonia. MUSCULOSKELETAL DISORDERS Somatic Muscles: Myocytes do not divide but atrophy if not used much or hypertrophy if stimulated. Thus, they develop many disorders secondary to their motor nerve supplies. These may be developmental (CP), infectious (polio), inherited (Huntington's, spinal muscular atrophy), degenerative (MS, Parkinson's) or idiopathic (motor neurone disease). There may also be peripheral nerve problems as in diabetes, Guillain-Barre syndrome and myasthenia gravis (autoimmune damage to the neuromuscular junctions). Myopathies are also possible, notably Duchenne muscular dystrophy (an X-linked recessive means no dystrophin is synthesized). Muscle trauma or an ill-fitting cast may lead to compartment syndrome (swelling occludes blood flow into a muscle 'compartment' the cells of which may die and be replaced by scar tissue, with permanent contracture). Signs of this in fracture cases are cyanotic fingers, delayed finger capillary refilling, motor weakness in the limb, swelling, and pain that is not readily relieved by medications. 5 Bones: These contain crystalline calcium salts deposited on collagen (production defects of which may lead to osteogenesis imperfecta and Paget's disease). Bones may be compact (strong but heavy) or spongy (weaker but lighter and used as a bone marrow site). Most bone growth is in centres of ossification such as the epiphyseal growth plates and is endochondrial. Initially, it is woven bone but this is normally rebuilt (in adults its presence is pathological). Bones are surrounded by a periosteum (for muscle insertions) and an endosteum (if hollow). Apart from fibroblasts they use osteoblasts to lay down bone Ca++ and osteoclasts (activated by PTH, infections, and bone cancers) to dissolve it again. Bones are under constant maintenance and remodelling but after full adulthood they suffer progressive loss of Ca++ leading to eventual osteoporosis. This disorder is mostly due to age and post- menopausal oestrogen loss (hence HRT) and is best managed by dietary calcium and vit. D supplements and appropriate exercise regimens. Demineralisation also occurs in instances of PTH excess, vit. D deficiency (calcitriol corrects) leading to rickets and osteomalacia, and a variety of bone cancers (notably multiple myeloma and metastases from the prostate). Some bone cancers are 'benign' but others are very aggressive, osteosarcoma perhaps being the worst. Apart from palliative methods, these tumours are treated with cytotoxics but also osteoclast inhibitors like etidronate. Fractures can be closed (skin intact) or open (compound; the skin is breached), the latter increasing the risk of an infection (osteomyelitis), which is undesirable because it readily goes systemic, forms a bone abscess that destroys bone and is hard to resolve, even with strong antibiotics. The normal healing sequence for a fracture is formation of a haematoma, debridement of the site, growth of new blood vessels and a fibrous (osteoid) callus, ossification of the callus, and finally remodelling of the fracture. When a fracture is subjected to closed reduction, a plaster cast is applied, but if open reduction occurs, traction and internal fixation of the fracture will be carried out. At a fracture site there will usually be pain, swelling, muscle shortening, deformity of the site, crepitus (grating sounds), and perhaps eventual compartment syndrome. Common complications of major fractures also include shock (since about a litre of blood can be lost at the site) and formation of fat emboli. These are globules of fat that leak from the bone marrow and can dangerously impair perfusion of the brain, lungs and kidneys 1-3 days after the fracture occurs. The risk that such emboli will form is reduced by immediate immobilisation or the area, splinting or other support, and minimising manipulation of the site. Other useful assessments of a fracture patient's neurovascular status are for pain, pallor, pulses, paraesthesia, and paralysis (the 5 P's). 6 Joints: Articulating joints are lubricated by synovial fluid which is enclosed by a joint capsule. The joint surfaces have avascular hyaline cartilage. Joint diseases include osteoarthritis (age/wear-and- tear/biochemical defects leading to erosion of the articulating cartilages), rheumatoid (RA; autoimmune inflammation of the joint structures involving both T cells and the rheumatoid factor antibody), gouty (irritation by urate crystals), infectious (e.g. Ross River arthritis) and other arthritis types. Osteoarthritis has a familial component to it and is greatly exacerbated by obesity. There are adult and juvenile forms of rheumatoid arthritis, which is perhaps the most debilitating type since effusions cause severe joint displacement and so the hands can become rigid 'claws.' Obesity exacerbates osteoarthritis and gout (for which a largely X-linked genetic predisposition exists). Surgical fitting of prosthetic joints has now become routine. Since fracture of the neck of the femur is a common occurrence in the elderly and since the hip and knee joints are major sites of arthritis and wear-and-tear problems, these are especially important sites for prosthesis insertion. Total hip replacement is a major operation and has many important post-surgery considerations, including ease of dislocation, the need for wound drainage, and the high risk of avascular necrosis, thromboembolism and infection. Prophylactic heparin therapy (used with great care to avoid complications) helps reduce the high probability of deep vein thrombosis and subsequent pulmonary embolism. Prior to discharge, the patient also needs extensive education on ways to protect the prosthesis and avoid its dislocation. Pain relief for musculoskeletal disorders depends on the specific problem. Some cases cannot be easily resolved, though NSAIDs, celecoxib and corticosteroids, etc. are widely used. The initial treatment for strained muscles and sprained joint ligaments is rest, ice, compression, and elevation (RICE), this sequence serving to minimise swelling of the injured part. Arthritic pain, especially RA, can also be managed by appropriate joint-protecting exercises and sleep-promoting measures.