Cardiac Failure

Anaesthesia and surgery in patients with cardiac failure carry an increased risk of morbidity and mortality. The cause of heart failure should be elucidated, and treatment instituted before surgery. Left heart failure causes pulmonary congestion and oedema, and decreases pulmonary compliance respiratory work is increased and hypoxaemia occurs. Signs indicating left ventricular failure include tachycardia, gallop rhythm, mitral regurgitation, cyanosis, tachypnoea, crepitations and wheeze. Causes...

Hypoventilation

This has been discussed in detail above. Moderate hypoventilation, with some elevation of PaC02, leads to a modest reduction in Pac> 2 (Fig. 41.3). Obstructive sleep apnoea may produce profound transient but repeated decreases in arterial oxygenation. Sac> 2 may decrease to less than 75 , corresponding to a Pa02 of less than 5 kPa (40 mmHg). These repeated episodes of hypoxaemia cause temporary, and possibly permanent, defects in cognitive function in elderly patients and may contribute to...

Tonsillectomy

Each year 80 000 adenotonsillectomies are performed in the UK, with a rate of 8 per 1000 children under the age of 15. This frequency is 40 of that 15 years ago. In 1968 there were six deaths, a mortality rate of 1 in 28 000, but this has now been reduced to less than 1 in 100 000. Most children attend for surgery on the day of operation and premedication is often not practical for these children. If premedication is required before tonsillectomy, it is administered most conveniently to the...

Airway management

The ratio of dead space to tidal volume tends to remain constant at about 0.3 throughout life in the healthy person. Anaesthetic apparatus such as connectors and humidification devices significantly increase dead space and should be kept to the minimum. This is especially important if the child breathes spontaneously during anaesthesia. The Rendell-Baker masks were developed to fit around the facial anatomy of the child in an attempt to minimize equipment dead space. In fact, the flow of gas in...

Ischaemic Heart Disease

Five per cent of patients over 35 years of age have asymptomatic ischaemic heart disease. In patients who have had a previous myocardial infarction, anaesthesia and surgery within 3 months of infarction until recently carried a 40 risk of perioperative re-infarction. This rate decreases to 15 at 3-6 months and 5 thereafter. Research findings suggest that, with intensive perioperative monitoring, much lower rates of reinfarction can be achieved (at less than 3 months and at 3-6 months)....

Myocardial Infarction

The average incidence of myocardial infarction (MI) is 1-2 in unselected patients over 40 years of age undergoing major non-cardiac surgery. Pre-existing coronary artery disease and, in particular, evidence of a previous MI result in a higher risk. Mortality in patients who suffer a perioperative MI may be as high as 60 . Perioperative MI occurs most commonly on the third postoperative day, but may happen at any time during or after surgery. A number of factors which may be detected during...

Furosemide

Furosemide is usually administered intravenously (0.1-1 mg kg l) or orally (0.75-3 mg kg l). It is well absorbed orally and about 60 of the dose reaches the central circulation within a short period, with the peak effect after 1-1.5 h. Intravenous furosemide is usually started as a slow 20-40 mg injection in adults, but higher doses or even an infusion may be required in the case of elderly patients with renal failure or severe congestive cardiac failure. Approximately 90 of the drug is bound...

Complications of diabetes mellitus

Cardiovascular disorders (coronary artery, cerebrovascular and peripheral vascular) are common in diabetics, and there is an increased risk of perioperative myocardial infarction. Careful preoperative assessment of cardiovascular function, appropriate choice of anaesthetic technique and precise perioperative monitoring are essential. Renal disease. Microvascular damage produces glomerulosclerosis with proteinuria, oedema and eventually chronic renal failure. Anaesthetic implications of renal...

Diabetes insipidus

This is caused by disease or damage affecting the hypothalamic-pos-terior pituitary axis. Common causes are pituitary tumours, craniopharyngiomas, basal skull fracture and infection, or it may occur as a sequel to pituitary surgery. In 10 of cases, diabetes insipidus is renal in origin. Dehydration with hypernatraemia follows excretion of large volumes of dilute urine. Patients require fluid replacement and treatment with vasopressin (DDAVP desmopressin 2-4 pg i.m. daily or 1 pg i.v. in the...

Assessment of baroreceptor responses

The loss of baroreceptor reflex control of arterial pressure affects normal activities of daily living, resulting, for example, in postural hypotension. During anaesthesia, the loss of these reflexes (e.g. in patients with an autonomic neuropathy secondary to diabetes mel-litus) results in impairment of the normal cardiovascular responses to events such as positive pressure ventilation of the lungs. The integrity of the baroreceptor response may be assessed simply either by the arterial...

ACE inhibitors

ACE inhibitors are used for the treatment of hypertension and cardiac failure. Their principal mechanism of action is inhibition of A-II formation, but effects on the kallikrein-kinin system are also important. All ACE inhibitors reduce arteriolar tone, peripheral resistance and arterial pressure directly by decreasing both A-II-mediated vasoconstriction and sympathetic nervous system activity. Renal blood flow increases, further inhibiting aldosterone and antidiuretic hormone secretion and...

Acupuncture And Ponv

The use of acupuncture was championed in the 1980s by the late Professor Dundee. Acupuncture for nausea is performed at the P6 (Neiguan) point which is situated between the tendons of the flexor carpi radialis and palmaris longus, 2 Chinese inches from the distal skin crease. A Chinese inch is the width of the interpha-langeal joint of the thumb. Studies using meta-analysis have con firmed that stimulation of the P6 point is indeed effective if applied before or after anaesthesia. It is less...

Acute Pain

Acute pain following trauma or surgery, with which all anaesthetists are familiar, is self-limiting and reduces as tissue damage resolves. By and large, the severity of pain reflects the degree of injury, particularly with injury to somatic structures such as bone and muscle a broken leg hurts more than a simple sprain. However, the 'pain pathway', from the pain receptor ('nociceptor') to pain awareness in the brain, is not a simple relay system but a much more complex one in which the 'pain...

Adrenergic agonists

Epinephrine has been used in the treatment of asthma since the beginning of the 20th century. In addition to increasing the intracellular concentration of cAMP, 3-agonists have other complementary effects on the airways, the most notable being inhibition of mast cell mediator release. Table 10.3 summarizes the effects of 3-agonists on the airways. These effects are mediated via subtype fij-receptors, which are spread throughout the larger and smaller airways ( -selective agents are now used...

Adverse effects

Adverse effects of methylxanthines are frequent (Table 10.7). They are more likely to occur in patients who are already receiving Table 10.5 Respiratory effects of methylxanthines Bronchodilatation by phosphodiesterase inhibition Increased mucociliary clearance Decreased mediator release Decreased microvascular leakage Decreased airway oedema Increased contraction of fatigued respiratory muscles Table 10.7 Common adverse effects of methylxanthines other -agonist bronchodilators or...

Allergic reactions

Allergy to the esters was relatively common, particularly with procaine, and was caused by pa ' -aminobenzoic acid produced on hydrolysis. Most reactions were dermal in personnel handling the drugs, but fatal anaphylaxis has been recorded. Allergy to the amides is extremely rare and most reactions result from systemic toxicity, overdosage with vasoconstrictors, or are manifestations of anxiety. The occasional genuine allergic reaction is usually to a preservative in the solution rather than the...

Anaesthesia

All volatile anaesthetic agents are bronchodilators, and are therefore well tolerated. Bronchoconstriction may be triggered by tracheal intubation or by surgical stimulation during light anaesthesia. The larynx and trachea should be sprayed with local anaesthetic and adequate depth of anaesthesia maintained. The use of the laryngeal mask airway can reduce stimulation of adverse airway reflexes. Drugs which are associated with histamine release (atracurium and morphine) are best avoided...

Anaesthetic management

The indications for general anaesthesia during MRI are similar to those for CT. In addition, the scanner is very noisy and the patient lies on a long thin table in a dark confined space within the tube. This can cause claustrophobia or anxiety-related problems which may require sedation or anaesthesia. There are other unique problems presented by MRI. These include relative inaccessibility of the patient and the magnetic properties of the equipment. The body cylinder of the scanner surrounds...

Anatomy of the cardiovascular system

Right Metacarpal Vein

A sound knowledge of anatomy is important to the anaesthetist. This chapter describes the anatomy of the heart and the great vessels. In addition, the vascular anatomy of the upper and lower limbs and the neck in relation to venepuncture is described. The heart is the muscular pump of the systemic and pulmonary circulations. Irregularly conical in shape, it lies obliquely across the lower mediastinum behind the sternum, suspended by the great vessels. The borders and surfaces of the heart may...

Haematology

Haemoglobin Men Women 10-12 years 1 year 3 months Full-term Red blood cell count (RBC) Men Women White blood cell count (WBC) Neutrophils Lymphocytes Monocytes Eosinophils Basophils Platelet count Reticulocyte count Sedimentation rate Men Women Plasma viscosity Packed cell volume (PCV) and haematocrit (Hct) Men Women Mean corpuscular haemoglobin concentration (MCHC) 11.5-14,8 g dH 11.0-13.0 g dl 1 9.5-12.5 g dH 4.5-6.0 x 1012 L-l 3.5-5.0 x 1012 L-l 4.0-11.0 x 109 L-l 40-70 20 45 2-10 1-6 0-1...

Autoregulation

Autoregulation may be defined as the ability of an organ to maintain a constant blood flow over a wide range of perfusion pressures (Fig. 6.3). The cerebral and renal circulations have highly developed autoregulatory mechanisms and have been studied extensively. Two major mechanisms, metabolic and myogenic, have been proposed for this phenomenon. The metabolic mechanism depends on the accumulation and washout of vasodilator metabolites. During periods of decreased perfusion pressure, a...

Axial Length And Eye Movements

It is good practice at the time of the preoperative visit to check the axial length of the eyeball. All patients scheduled for fitting of an intraocular lens will have an ultrasound scan and this measurement will have been recorded. There is an increased danger of global perforation in the high myope and patients with an axial length in excess of 25 mm should be treated with caution (see Figs 47.5 and 47.6). Patients scheduled for glaucoma surgery are not usually scanned preoperatively, but...

Cardiovascular effects

Hypertension may occur for several reasons. A raised plasma renin concentration secondary to decreased perfusion of the juxtaglomerular apparatus results in hypertension through increased secretion of angiotensin and aldosterone. Fluid retention also causes hypertension by increasing the circulating blood volume. Conversely, hypertension from other causes results in renal impairment. The precise cause of hypertension in these patients should be sought and the hypertension treated. Anaesthesia...

Carotid Artery Surgery

Carotid endarterectomy is performed to prevent disabling stroke in patients with atheromatous plaques in the common carotid bifurcation or internal carotid artery. Most strokes from plaques in these sites are embolic. The underlying pathology is usually atherosclerosis, and most patients are elderly, with hypertension and generalized vascular disease. Cerebral autoregulation may be impaired and cerebral blood flow is therefore proportional to systemic arterial pressure. The main risk of surgery...

Cellular physiology pharmacology relevant to anaesthesia

This chapter is divided into four main sections a description of receptors (including second messengers) representation of drug-receptor interaction (receptor pharmacology) intracellular Ca2+ as a vital signalling molecule and, finally, potential targets(s) for anaesthetic action are discussed. Receptors recognize specific small signalling molecules to produce a biological effect. In the unbound state, a receptor is functionally silent. Excluding the intracellular receptor for inositol(l,4,5)...

Chronic Obstructive Pulmonary Disease

Chronic bronchitis is characterized by the presence of productive cough for at least 3 months in two successive years. Airways obstruction is caused by bronchoconstriction, bronchial oedema and hypersecretion of mucus. In the postoperative period, pulmonary atelectasis and pneumonia result if sputum is not cleared. COPD may be classified into two groups - the bronchitis group (blue bloaters) and the emphysematous group (pink puffers) -although in practice most patients have mixed pathologies....

Chronic Pain

Chronic pain is often defined in simple temporal terms as pain present for more than 6 months. This is oversimplistic, and in many ways chronic pain is different from acute pain. Acute pain has a useful physiological role, in that it serves to protect the injury from further damage until healing is complete. Chronic pain often has no useful physiological role. The impact of chronic-pain on function and quality of life is often disproportionately greater than may be explained by the underlying...

Class 1 antiarrhythmics Class la

These drugs are used for the treatment and prevention of ventricular and supraventricular arrhythmias. Their use in the prevention of atrial fibrillation has declined because of pro-arrhythmic effects and increased mortality in several large studies, in particular in patients with ischaemic heart disease or poor LV function. However, torsade de pointes (a form of polymorphic ventricular tachycardia) may be induced even in patients without structural heart disease. Quinidine is an isomer of...

Class 3 antiarrhythmic drugs

Class 3 antiarrhythmics prolong the action potential in conducting tissues and myocardial muscle. In particular, they prolong repolarization by K+ channel blockade, decreasing outward K+ conduction in the bundle of His, atrial and ventricular muscle, and accessory pathways. They are used for the treatment of supraventricular and ventricular tachyarrhythmias, including those associated with accessory conduction pathways. Some drugs have other actions (e.g. sotalol also produces p-blockade, and...

Clomethiazole

Clomethiazole is an anticonvulsant with a limited place in the management of status epilepticus. It was used extensively in the past to manage acute alcohol withdrawal states. In addition to its anticonvulsant properties, it is a powerful sedative. Respiratory depression, airway obstruction and hypotension may follow rapid infusion. Prolonged infusion may be associated with a decreasing level of consciousness. Clomethiazole has a short half-life, but although the rate of infusion may...

Coagulation Control

When the bypass cannulae have been removed, residual effects of heparin are antagonized with protamine. Protamine 1 mg (or less) is given for each 100 units of heparin the dosage may be titrated using the ACT. The drug should be given slowly, especially if there is residual hypovolaemia or raised pulmonary vascular resistance. Protamine may produce systemic hypotension rapidly, as a result of peripheral vasodilatation, but may also cause pulmonary vasoconstriction. In excessive dosage, it has...

Conduct of anaesthesia

Sudden, severe hypertension (due to systemic release of catecholamines) may occur during tumour mobilization and handling, and severe hypotension may occur after ligation of the venous drainage of the tumour, particularly if preoperative preparation has been inadequate. Marked fluctuations in arterial pressure may also occur during induction of anaesthesia and tracheal intubation. Sedative and anxiolytic premedication is useful agents used for induction and maintenance should be selected on the...

Conduct of laryngoscopy

The position of the patient's head and neck is important. The neck should be flexed and the head extended with the support of a pillow thus the oral, pharyngeal and tracheal axes are brought into alignment (Fig. 37.4). The laryngoscope is designed for left hand use and is introduced into the right side of the mouth while the right hand opens the mouth, parting the lips to avoid interposing them between laryngoscope and teeth. The teeth may be protected from blade trauma with the fingers or the...

Day Surgery

Day-case surgery confers many advantages in children. Children who are admitted to hospital often develop behavioural problems perhaps as a result of separation from parents and disruption of family life. These problems manifest as an alteration of sleep pattern, bedwetting and regression of developmental milestones. Most children make excellent candidates for day-case surgery. They are usually healthy and the procedures performed are usually of short to intermediate duration. Only experienced...

Dosage and administration

Inhalation is the method of choice because systemic side-effects are minimized. An inhaled drug may also be more effective because it reaches the surface cells (mast cells and epithelial cells) which are relatively inaccessible to a drug administered systemi-cally. Salbutamol may be administered from a pressurized aerosol (100 pg per puff dose 1-2 puffs). The effect lasts for 4-6 h. The drug may also be nebulized to be delivered with oxygen-enriched air using a face mask, or with inspiratory...

Drugs inhibiting gastric acid production

These drugs include the H2-receptor antagonists (e.g. cimetidine, ranitidine), proton pump inhibitors (PPIs, e.g. omeprazole, lansoprazole) and prostaglandin analogues (e.g. misoprostol). The last also increase mucosal blood flow and enhance mucus and bicarbonate production. They are often prescribed in association with non-steroidal anti-inflammatory drugs. H2-receptor antagonists inhibit acid secretion by competitive and reversible inhibition of H2-receptors on the parietal cell surface,...

Emergence And Recovery

After completion of surgery anaesthetic agents arc withdrawn and oxygen 100 is delivered. Following removal of the tracheal tube or LMA, the patient's airway is supported until respiratory reflexes are intact. The patient's muscle power and coordination are assessed by testing hand grip, tongue protrusion or a sustained head lift from the pillow in response to command. Return of adequate muscle power must be ensured before the patient leaves theatre. Full monitoring of the patient should not be...

Erythropoietin

Erythropoietin is a circulating hormone secreted by the kidneys. It stimulates the bone marrow to produce red blood cells. The ability of the kidney to secrete erythropoietin deteriorates as excretory function decreases. Patients with severe chronic renal failure are unable to produce adequate quantities of erythropoietin, which leads to diminished red blood cell production. The retention of toxic substances also contributes to bone marrow depression. In addition, red cell survival is reduced...

Factors affecting duration of nondepolarizing neuromuscular block

The duration of action of non-depolarizing muscle relaxants is affected by a number of factors. Effects are most marked with the longer-acting agents, such as tubocurarine and pancuronium. Prior administration of succinylcholine potentiates the effect and lengthens the duration of action of non-depolarizing drugs. Concomitant administration of a potent inhalation agent increases the duration of block. This is most marked with the ether anaesthetic agents such as isoflurane, enflurane and...

Factors affecting spread Table 432

The most important factor which affects the height of block in SAB is the baricity of the solution, which may be made hyperbaric (i.e. denser than CSF) by the addition of glucose. The specific gravity (SG) of CSF is 1.004. The addition of glucose 5 or 6 to a Table 43.1 Techniques of subarachnoid block Table 43.1 Techniques of subarachnoid block Unilateral Not possible with hyperbaric solutions which eventu all)' affect both sides after the patient is placed supine, Hypobaric solutions, e.g....

Fig

Several other neuropeptides also present (enkephalin, neurotensin, substance P, somatostatin, nitric oxide, serotonin and catecholamines. ACh is the transmitter at all preganglionic synapses, acting via nicotinic receptors, as in the parasympathetic ganglia. At the postganglionic sympathetic endings, transmission is mediated by norepinephrine, which is present in the presynaptic terminals and also in the adrenal medulla. Activation of preganglionic nicotinic fibres to the adrenal medulla causes...

Fu Ther Reading

McQuay H, Moore A (eds) 1998 An evidence-based resource for pain relief. Oxford University Press, Oxford National Health and Medical Research Council of Australia 1999 Acute pain management scientific evidence. Commonwealth of Australia, Canberra Ogilvy A J, Smith G 1994 Postoperative pain. In Nimmo W S, Rowbotham D J, Smith G (eds) Anaesthesia, 2nd edn. Blackwell Scientific Publications, Oxford Royal College of Anaesthetists 1998 Guidelines for the use of non-steroidal anti-inflammatory drugs...

General anaesthesia

The choice of induction and maintenance agent depends upon the requirements of the patient and the preference of the anaesthetist. Any induction agent used in day-case anaesthesia should ensure a smooth induction, good immediate recovery with minimal postoperative sequelae and a rapid return to street fitness. Several intravenous induction agents have been used successfully for induction of anaesthesia in day-case patients these include methohexital, etomidate and thiopental. However, pro-pofol...

General principles of pharmacology and pharmacokinetics

Drugs have an effect because of their physicochemical properties, activity at receptors, inhibition of enzyme systems or influence on nucleic acid synthesis. Sodium citrate neutralizes acid and is given frequently to reduce the likelihood of pneumonitis after inhalation of gastric contents. Chelating agents combine chemically with metal ions, reducing their toxicity and enhancing elimination, usually in the urine. Such drugs include desferoxamine (iron, aluminium), dicobalt edetate (cyanide...

Hepatic encephalopathy

This may result from increased concentrations of false neurotransmitters, such as octopamine and 5-HT, which replace the normal dopamine and norepinephrine. GABA is produced in the gut by bacterial action on protein and may lead to coma by passing through the blood-brain barrier in liver failure. The number of binding sites for GABA, glycine and benzodiazepines on postsynaptic neurones is increased in acute liver failure present data suggest that this mechanism is the most important contributor...

History of allergy

A history of allergy to specific substances must be sought, whether it is a drug, foods or adhesives, and the exact nature of the symptoms and signs should be elicited in order to distinguish true allergy from some other predictable adverse reaction. Latex allergy is becoming an increasing problem and requires specific equipment to be used perioperatively. Atopic individuals do not have an increased risk of anaphylaxis, but may demonstrate increased cardiovascular or respiratory reactivity to...

Hyponatremia

This is defined as a plasma sodium concentration of less than 135 mmol L 1. Hyponatraemia is a common finding in hospital patients. It may occur as a result of water retention, sodium loss or both consequently, it may be associated with an expanded, normal or contracted ECFV. As in hypernatraemia, the state of ECFV is important in determining the cause of the electrolyte imbalance. As plasma osmolality decreases, an osmolal gradient is created across the cell membrane and results in movement of...

Hypopituitarism Simmonds disease

Causes include chromophobe adenoma, tumours of surrounding tissues (e.g. craniopharyngioma), skull fractures, infarction following postpartum haemorrhage and infection. Clinical features include loss of axillary and pubic hair, amenorrhoea, features of hypothyroidism and adrenal insufficiency, including hypotension, but with a striking pallor, in contrast to the pigmentation of Addison's disease (see p. 447). The fluid and electrolyte disturbances are not as marked as in primary adrenal failure...

Hypothalamic And Pituitary Function

In unicellular organisms such as bacteria, fungi and protozoa, the entire cell may respond quickly to any stimulus within its environment. Any substances released within the cell need only travel minute distances to act. However, in complicated multicellular organisms, such as humans, comprising specialized organs and cell types, there needs to be some means to coordinate responses to the environment. In mammals, this integration of responses is achieved by the nervous and endocrine systems,...

Immunosuppression Prednisolone and azathioprine

Corticosteroids were the first drugs to be used as immunosuppressive agents. Initially, very high doses were used, producing the typical steroid side-effects, e.g. Cushingoid appearance, hypertension, hyperglycaemia and osteoporosis. Experience and research showed that large doses were not necessary and that better results and fewer side-effects were possible with lower doses. The 'modern era' of immunosuppression started with the discovery of azathioprine. For a long period of time, the...

Induction Of Anaesthesia

Anaesthesia may be induced by the inhalation or intravenous route. Traditionally, the inhalation route has been used for young children and the intravenous route for older children and adults. The introduction of EMLA cream has allowed the intravenous route to be used more frequently. However, EMLA cream should be applied 1 h before anticipated cannulation, which may be difficult for outpatients. For many years, metho-hexital was the drug of choice for induction of anaesthesia for dental...

Intracranial tumours

The preoperative condition of patients who present for craniotomy varies enormously. The level of consciousness ranges from completely awake and orientated to comatose some patients are confused, disorientated, euphoric or aggressive. The anaesthetist must always assume that any abnormal behaviour is related to the patient's condition and not place too much reliance on what the patient says if it appears to conflict with previous history. In particular, apparently unrelated medical conditions...

Lipid breakdown lipolysis Fig 227

Fat is stored in adipose tissue as triacylglycerol, a molecule consisting of three fatty acids attached to a molecule of glycerol. The first stage of lipolysis is the hydrolysis of triacylglycerol to glycerol and free fatty acids in the adipose tissue. The reaction is catalysed by lipase. The free fatty acids circulate in the plasma bound to albumin. They are taken up by the liver and skeletal muscle, where CoA is attached in the cytosol to form acyl-CoA. Acyl-CoA then enters the mitochondria...

Liver Blood Supply

The liver has a dual blood supply from the hepatic artery and the portal vein. Total liver blood flow in the adult is between 1100 and 1800 ml min-1. Blood from the hepatic artery is highly saturated with oxygen (98 ) and, although only 30 of total liver blood flow, it is responsible for 40-55 of liver oxygen supply. The portal vein is formed by the union of the splenic and superior mesenteric veins. It consists of the venous effluent of the gut and therefore has a lower oxygen saturation (75...

Liver Disease

Hepatocellular disease (cirrhosis or acute liver failure) gives rise to a variety of abnormalities of coagulation. Diminished protein synthesis leads to low levels of vitamin K-dependent clotting factors (II, VII, IX and X), factor V, factor XIII and fibrinogen. Accumulation of fibrin degradation products results from increased fibrinolysis, as a result of increased plasminogen activator, and impaired clearance from the plasma. Platelets are often reduced in number, particularly in the presence...

Management

Management must prevent hypoxaemia and should aim to resolve the bronchospasm. Initially, give 100 oxygen, deepen anaesthesia if appropriate and remove any precipitating factors (e.g. reposition the tracheal tube, stop the operation). If further treatment is necessary, give a bronchodilator in increments according to the response. Recommended drugs include intravenous aminophylline (up to 6 mg kg-l) or salbutamol (up to 3 pg kg1). Volatile anaesthetic agents and ketamine are also effective...

Maternal circulation

Maternal and fetal blood vessels in the placenta. Chorionic villi are seen dipping down into the maternal circulation. Maternal vessels either envelop a chorionic villus or release spurts of blood directly into the intervillous space. The two circulations are separated by two layers of cells. These cells have microvilli and present a huge surface area for exchange of gases and essential nutrients. Maternal and fetal blood vessels in the placenta. Chorionic villi are seen dipping down into the...

Methylxanthines

The bronchodilator effect of strong coffee was described in the 19th century. Methylxanthines, which are related to caffeine, have been used widely to control asthma since 1930. Theophylline is the most commonly used parent compound. Aminophylline is a water-soluble salt that contains over 75 theophylline and is used as the injectable form of theophylline. Methylxanthines have widespread effects involving various organ systems. With regard to their bronchodilator effects, the following...

Mitral stenosis

This is usually a manifestation of rheumatic heart disease. Characteristic features include atrial fibrillation, arterial embolism, pulmonary oedema, pulmonary hypertension and right heart failure. Acute pulmonary oedema may follow the onset of atrial fibrillation. Patients with mitral stenosis who present for surgery are frequently receiving digoxin, diuretics and anticoagulants. Preoperative control of atrial fibrillation, treatment of pulmonary oedema and management of anticoagulant therapy...

Monitoring during transfer

It is essential that the standard of care and monitoring during transfer is as high as that applied in the operating theatre and that personnel with adequate knowledge and experience accompany the patient. The patient should be physiologically stable on departure. Appropriate monitoring must be started before transfer. The oxygen saturation, electrocardiogram and arterial pressure should be monitored in all patients. The diagnosis of arrhythmias may be very Table 38.18 Variables which may be...

Muscle relaxation

Benzodiazepines produce a mild reduction in muscle tone, which can be advantageous, e.g. during mechanical ventilation in the intensive care unit, when reducing articular dislocations or during endoscopy. However, muscle relaxation is partly responsible for the airway obstruction which may occur during intravenous sedation. The muscle relaxation is not related to any effect at the neuromuscular junction, but results from suppression of the inter-nuncial neurones of the spinal cord and...

N h U Ro Log Icat Dis Hase

There are several points of significance Respiratory impairment. Motor neuropathy from various causes, e.g. motor neurone disease, acute polyneuritis (Guillain-Barre syndrome), disorders of the neuromuscular junction and high spinal cord lesions may produce respiratory inadequacy. These patients are sensitive to anaesthetic agents, opioids and relaxants, and if intraoperative IPPV is undertaken, a period of elective postoperative ventilation may be necessary until full recovery from the effects...

Nearinfrared Spectrophotometry

Indices of cerebral oxygenation and haemodynamics may be quantified by this technique. Concentrations of oxygenated and reduced haemoglobin, oxidized cytochromes and total haemoglobin, together with cerebral blood volume and changes in cerebral blood flow, may be measured and displayed instantaneously. Striking changes have been observed in babies with cerebral oedema after birth trauma. Some clinical aspects of neurophysiology may be investigated quantitatively, e.g. Glasgow Coma Scale. The...

Neuromuscular Monitoring

There is no clinical tool available to measure accurately neuromuscular transmission in a muscle group. Thus, neither the amount of acetylcholine released in response to a given stimulus nor the number of postsynaptic receptors blocked by a given nondepolarizing muscle relaxant may be assessed. However, it is possible to obtain a crude estimate of muscle contraction during anaesthesia using a variety of techniques. All require the application to a peripheral nerve of a current of up to 60 mA,...

Nonpharmacological analgesia Birth preparation classes

In the 1930s, Grantly Dick-Read proposed that childbirth may be painless, as it is a normal life-event, and that society had conditioned women to believe that childbirth was painful. He proposed that education of women about the process of labour and delivery and training them in relaxation therapy would obviate any need for analgesics. Active partner participation was encouraged. The goals of childbirth preparation are to fully inform women about what to expect in labour and to enhance their...

Parasympathetic receptor pharmacology

Parasympathetic receptors have been classified according to the actions of the alkaloids muscarine and nicotine. The actions of ACh at the postganglionic membrane site are mimicked by muscarine and are termed muscarinic, whereas preganglionic transmission is termed nicotinic. ACh is also the neurotransmitter at the neuromuscular junction, via nicotinic receptor sites. Five subtypes of muscarinic receptors (M1-M5) have been characterized by molecular cloning techniques, and specific antagonists...

Parathyroid Hormones And Calcium Homeostasis

Humans have four parathyroid glands, two on each side of the neck. The glands have a variable position in the neck and may even be found in the mediastinum. In common with all endocrine glands, they are richly vascularized with fenestrated capillaries. They derive their blood supply from the inferior thyroid arteries. There are two cell types in the parathyroid glands chief cells have prominent endoplasmic reticulum, Golgi apparatus and numerous secretory vesicles oxyphil cells are rich in...

Peripheral factors

The commonest peripheral factor associated with hypoventilation is residual neuromuscular blockade. This may be exaggerated by disease of the neuromuscular junction, e.g. myasthenia gravis, or by electrolyte disturbances. Inadequate reversal of neuromuscular blockade is usually associated with uncoordinated, jerky movements, although these may occur occasionally during recovery of consciousness in patients with normal neuromuscular function. Measurement of tidal volume is not a reliable guide...

Pharmacodynamic variability

Although there are widespread pharmacokinetic variations between patients in response to administration of opioids, the major reason for variation in opioid sensitivity is pharmacodynamic, i.e. a difference in the inherent sensitivity of opioid receptors. Using continuous infusions of opioids to achieve equilibrium between receptor drug concentration and plasma concentration, it is possible to define a steady-state plasma concentration of opioid at which analgesia is produced. This is termed...

Pharmacokinetics

Blood concentrations of thiopental increase rapidly after i.v. administration. Between 75 and 85 of the drug is bound to protein, mostly albumin thus, more free drug is available if plasma protein concentrations are reduced by malnutrition or disease. Protein binding is affected by pH and is decreased by alkalaemia thus the concentration of free drug is increased during hyperventilation. Some drugs, e.g. phenylbutazone, occupy the same binding sites, and protein binding of thiopental may be...

Phase Ii Induction Rapidsequence induction

This is the technique employed most frequently for the patient with a full stomach, although it contravenes one of the fundamental rules of anaesthesia, namely that muscle relaxants are not given until control of the airway is assured. The decision to employ the rapid-sequence induction technique balances the risk of losing control of the airway against the risk of aspiration. It is therefore imperative to assess carefully whether or not difficulty is likely to be encountered in performing...

Positioning The Patient

Many procedures are carried out with the patient in the lithotomy position. Care is needed to avoid damage to the common peroneal nerve because the legs may press against the lithotomy poles. The Lloyd-Davies position provides a variant of the lithotomy position. It is traditionally used for those with osteoarthritis of the hips or the lumbar spine. Before placing anaesthetized patients in these positions, they should be adequately anaesthetized, with good airway control, because it is...

Postoperative

This is more common in young adults and particularly in obstetric patients. It may present up to 2-7 days after lumbar puncture, and may persist for up to 6 weeks. Characteristically, it is worse on sitting, occipital in distribution and very disabling. The incidence is reduced by using small-gauge or pencil-point needles and ensuring that the bevel of the needle penetrates the dura in a sagittal plane. Simple analgesics may be the only treatment required, but occasionally an epidural...

Prediction Of Specific Adverse Events The difficult airway

There are specific medical or surgical conditions which are associated with potential airway problems during anaesthesia, such as obesity, the later stages of pregnancy, a large neck, mediastinal tumours and some faciomaxillary deformities. Apart from these, it requires an experienced anaesthetist to collate various physical features which can predict likely difficulty. Several classifications or scoring systems have been designed for this purpose, although none is entirely reliable they are...

Preoperative management

Detection and treatment of active infection. Amoxycillin, co-amoxiclav or ceftriaxone are usually appropriate, the common infecting organisms being Streptococcus pneumoniae and Haemophilus influenzae. Sputum for culture and sensitivities should be obtained to allow an appropriate choice of antibiotic. Chest physiotherapy and humidification of inspired gases aid expectoration. Treatment of airways obstruction. Some patients respond to bronchodilator therapy with a -agonist (e.g. salbutamol),...

Preoperative Preparation

For all elective surgery, it should be possible to prepare the child and family for what is to be expected in the perioperative period. This may be done in a wide variety of ways, including hospital tours, educational videotapes and pamphlets. The optimum choice depends on the age and intellectual ability of the child. Children possess great insight, and to attempt to keep forthcoming events secret is only likely to lead to mistrust and fear. All children should be visited preoperatively by the...

Prevention of haemorrhage

Patients with hypertension are more likely to bleed and optimal control of arterial pressure should be achieved before surgery is attempted. The fewer injections that are made into the orbit, the less is the chance of damaging a blood vessel. Cutting and slicing movements at the needle tip should be avoided. Fine needles are less traumatic than thicker ones. Deep intraorbital injections are more likely to cause haemorrhage than are shallow injections. The inferotemporal quadrant has fewer blood...

Prevention Of Ponv

Prevention rather than treatment of PONV should be the anaesthetist's aim. However, there is no agreed protocol as to which patients should receive preventive antiemetic therapy, but the relative indication for prophylaxis increases as the number of risk factors increase. There is an important organizational factor in the incidence of PONV. Antiemetics are often prescribed but not given. The overall incidence of PONV in a hospital is reduced if all professionals involved in the care of the...

Renal

When the renal blood flow is normal or high, little prostaglandin is released by the kidney. Where renal blood flow is reduced, when endogenous vasoconstrictors such as angiotensin and norepinephrine are released, or when cyclosporin has been given, prostaglandins are released (PGE2 in the medulla and PGI2 in the glomerulus) causing compensatory vasodilatation. NSAIDs may cause acute renal failure when given during blood loss or hypotension, cardiac failure, cirrhosis of the liver, nephrotic...

Respiratory acidosis

The cardinal features of a respiratory acidosis are a primary increase in PaCO2, a low pH and an appropriate rise in plasma bicarbonate. The extent of the acidaemia is proportional to the degree of hypercapnia. Buffering processes are activated rapidly in acute hypercapnia and may remove enough H+ from the extracellular fluid to result in a secondary increase in plasma HCOj. Usually, hypoxaemia and the manifestations of the underlying disease dominate the clinical picture, but hypercapnia per...

Sleep

The onset of sleep leads to a reduction in Vg accompanied by a small increase in PaC02 and a decrease in Pa02. The ventilatory response to hypercapnia and hypoxaemia is reduced, particularly in REM sleep. Brief periods of apnoea, both central and obstructive, are common during normal sleep in normal individuals. The diminution of upper airway muscle tone, particularly in the muscles of the tongue, commonly leads to partial airway obstruction, manifested by snoring which may progress to complete...

Smoking

Long-term deleterious effects of smoking include vascular disease of the peripheral, coronary and cerebral circulations, carcinoma of the lung and chronic bronchitis. It has been suggested that there are good theoretical reasons for advising all patients to cease cigarette smoking for at least 12 h prior to surgery, although there is little evidence to suggest that this influences patients' behaviour in this period. There are several potential mechanisms by which cigarette smok ing can...

Sore Throat

Up to 80 of patients complain of sore throat after anaesthesia and surgery. Some of the common causes include Trauma during tracheal intubation. Damage to the pharynx and tonsillar fauces may be caused by the laryngoscope blade. Trauma to the larynx. This is more likely if a red rubber tracheal rube is used rather than a plastic disposable tube, or if the tube has been forced through the vocal cords. A poorly stabilized tube causes more frictional damage to the larynx than one which is securely...

Special Problems Cerebrovascular surgery

Although aneurysm surgery is the largest component in this group, arteriovenous malformations and intracranial-extracranial anastomotic operations are also important. Meningiomas are formed from abnormal blood vessels and tend to produce symptoms related to a space-occupying lesion, rather than specific vascular problems. Nevertheless, their extreme vascularity, combined with difficult access, may make severe haemorrhage and blood volume replacement a significant factor. The current trend in...

Structure And Function

The function of the human nervous system is the acquisition of information from the external environment and its computation to produce an integrated response. The central nervous system (CNS) comprises the brain and spinal cord. The peripheral nervous system is composed of 43 pairs of nerves which contain afferent sensory fibres conducting impulses to the CNS from the periphery, and efferent motor fibres conducting in the reverse direction. There are 10y 1012 neurones in the CNS, each...

The Inflammatory Response

The inflammatory response to tissue damage or invasion by pathogenic organisms results in vasodilatation, increased capillary per- Vasoactive and chemotactic (actors released Complement, antibody and C-re active protein Major events in the inflammatory response. A bacterial infection causes tissue damage with release of various vasoactive and chemotactic factors. These factors induce increased blood flow to the area, increased capillary permeability and influxes of leucocytes from the blood...

The Lower Oesophageal Sphincter

The lower oesophageal sphincter (LOS) is an area (2-5 cm in length) of higher resting intraluminal pressure situated in the region of the cardia. The sphincter relaxes during oesophageal peristalsis to allow food into the stomach, but remains contracted at other times. The structure cannot be defined anatomically but may be detected using intraluminal pressure manometry. The LOS is the main barrier preventing reflux of gastric contents into the oesophagus and many drugs used in anaesthetic...

The skin

Intact skin prevents the penetration of most pathogens. Skin consists of two layers, the thinner outer layer, or epidermis, and the thicker dermis. The epidermis is renewed every 2-4 weeks and does not contain blood vessels. The dermis is composed of connective tissue and contains blood vessels, hair follicles, sebaceous glands and sweat glands. The sebaceous glands produce an oily substance termed sebum, made up of lactic acid and fatty acids, maintaining the pH of the skin at around 4. This...

Vasodilators

Drugs which dilate arteries or veins are used alone or in conjunction with inotropic agents in the management of acute left ventricular failure (Table 7.7). Some are also used in the treatment of hypertension, angina and ischaemic heart disease, including acute myocardial infarction. Vasodilators are useful in the treatment of acute hypertensive episodes and as part of a controlled hypotensive anaesthetic technique to reduce haemorrhage during surgery (see Ch. 56). Vasodilators may reduce...

Ventilatory drive

There are several possible causes of reduced ventilatory drive during recovery from anaesthesia (Table 41.3). The presence of intracranial pathology, e.g. tumour, trauma or haemorrhage, may affect ventilatory drive in the postoperative period. Ventilation is reduced in the presence of hypothermia, although it is usually appropriate for the metabolic needs of the body. Hypoventilation occurs in the hypocapnic patient, e.g. after a period of hyperventilation until PaC02 is restored to normal, and...

Adrenal Cortex And Medulla

Polypeptide Chain Cortex

The adrenal glands are situated at the superior poles of each kidney and may be thought of as two separate glands an outer cortex and the inner medulla. Medullary tissue may also be found at extra-adrenal sites along the course of the abdominal aorta. The cortex and medulla have different embryological origins, the cortex from mesoderm and the medulla from the neural crest. In keeping with all the other endocrine glands, the adrenals are richly vascularized. The adrenal gland derives its blood...

Peripheral Nerve Injury

Pain following peripheral nerve injury may be exacerbated by sympathetic activity. In these cases, the structures distal to the injury (almost invariably in a limb) are cold, discoloured, demonstrate marked allodynia and have worse pain in a cold environment. Symptoms are improved with a sympathetic block. In these cases, a-adrenoceptors are expressed on the damaged nerve and, in the presence of norepinephrine from local sympathetic nerves or circulating epinephrine, induce peripheral...

Neuropathic Pain In The P Sto P E Rat Iv E Peri O D

The possibility of the development of neuropathic pain should be borne in mind after surgery, as it is often missed in patients with acute pain and may require specific therapy (see Ch. 61 for the management of chronic pain). A useful definition of neuropathic pain is 'pain associated with injury, disease or surgical section of the peripheral or central nervous system'. One diagnostic clue after surgery is an unexpected increase in opioid consumption, as neuropathic pain often responds poorly...

Peripheral Nerve

The reported incidence of peripheral nerve injury is about 1 in every 1000 anaesthetics. Poor positioning is a common underlying factor. The brachial plexus and superficial nerves of the limbs (ulnar, radial and common peroneal) are the most frequently affected nerves. The usual mechanism of injury to superficial nerves is ischaemia from compression of the vasa vasorum by surgical retractors, leg stirrups or contact with other equipment. Nerve injury can be part of a compartment syndrome of a...

Local anaesthetic agents

Local anaesthetic drugs act by producing a reversible block to the transmission of peripheral nerve impulses. A reversible block may also be produced by physical factors, including pressure and cold. Although nerve compression is of purely historical interest, cold (produced by the evaporation of ethyl chloride, the application of ice packs or use of a cryoprobe) still has a limited use. Many types of drug have local anaesthetic actions (e.g. (3-block-ers and antihistamines), but all those...

Hypersensitivity Reactions

A localized inflammatory reaction termed delayed type hypersensitivity (DTH) may occur when some subpopulations of activated Th cells encounter some antigens. Tissue damage is usually limited and DTH plays an important role in defence against intracellular pathogens and contact antigens. Development of a DTH response requires a sensitization episode beforehand, when Th cells are activated and expanded clonally by antigen presented with the required class II MHC molecule. A second exposure to...

Sciatic nerve block Anatomy

The sciatic nerve (L4, 5, SI 3) arises from the sacral plexus, passes through the great sciatic foramen and descends in the posterior thigh to the popliteal fossa, where it divides into the tibial and common peroneal nerves. In the thigh, it supplies muscles and the hip joint. The posterior cutaneous nerve of the thigh (SI 3) may run with the sciatic nerve or separate from it proximally this nerve supplies the skin of the posterior thigh and upper calf. The tibial and common peroneal nerves,...

Postdural puncture headache PDPH

The incidence of PDPH is 0.5-1 and is often higher in teaching hospitals. It may occur at the time of epidural insertion or be caused later by catheter migration into the intrathecal space. The clinical presentation is of an occipital headache which may radiate anteriorly, aggravated by sitting and possibly associated with nausea, photophobia and, rarely, diplopia resulting from stretching of the Vlth cranial nerve as it passes through the dura. The differential diagnosis of meningitis,...

Reduction in secretions

Ether stimulated the production of secretions from pharyngeal and bronchial glands and premedication with an anticholinergic agent was common. This problem occurs rarely with modern anaesthetic agents, and anticholinergic premedication is no longer used as a routine. However, premedication with an anticholinergic drug is advisable for patients in whom an awake fibreoptic intubation is planned (when excessive salivation can create extra difficulty), or before using ketamine. Sedation is not...

ATI receptor antagonists

Angiotensin II receptor antagonists selectively block the type 1 A-II receptor (ATj receptor). They inhibit the RAS independently from the source of A-II and block any effects of ATI resulting from com pensatory stimulation of renin, such as reflex activation of the sympathetic nervous system. Hence, they do not cause tachycardia or an increase in cardiac contractility and are used in the treatment of hypertension. However, they are ineffective in primary hyperaldos-teronism. Their...