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...

Pulmonary Lobectomy

One-lung anaesthesia allows dissection in a field disturbed only by the movement of the mediastinum. Inflation of the lung temporarily may help to identify the lung fissures. Passive insufflation of the collapsed lung either through a suction catheter or with 5 cm continuous positive airway pressure may augment oxygenation achieved by one-lung anaesthesia. Surgical traction on mediastinal structures and disturbance to the mediastinum by surgeons' hands, instruments or retractors may cause...

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...

Gastrointestinal tract

Gastrointestinal disorders are the commonest of these unwanted effects. They include dyspepsia (or oesophageal irritation) and gastric erosions, which may present with bleeding or perforation. Piroxicam reportedly causes most symptomatic bleeding perhaps because of its long half-life and cumulation in the elderly. Naproxen and diclofenac are less often implicated and ibuprofen is said to be the safest in this respect, although when equi-anti-inflammatory doses are used, endoscopic evidence of...

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...

AAdrenergic receptor antagonists

A-Adrenergic antagonists (a-blockers) selectively inhibit the action of catecholamines at a-adrenergic receptors. They are used mainly as vasodilators for the second-line treatment of hypertension or as urinary tract smooth muscle relaxants in patients with benign prostatic hyperplasia. They also have an important role in the preoperative management of phaeochromocytoma (see Ch. 55). a-Blockers diminish vaso- and venoconstrictor tone causing venous pooling and a decrease in peripheral vascular...

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...

Adequacy of ventilation

Clinical signs of inadequate ventilation and an increase in Pacc> 2 include venous dilatation, wound oozing, tachycardia, hypertension and attempts at spontaneous ventilation by the patient. Measurement of airway pressure and end-expired Pcoj with a capnograph are mandatory during relaxant anaesthesia and controlled ventilation. Monitoring expired gas volume provides useful information to adjust the degree of mechanical ventilation, and occasionally arterial Pc02 measurement may be employed.

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...

Adrenergic blockers

In most instances, P-blockade should be maintained throughout the perioperative period, although the dose of p blocker should be reduced if undue bradycardia (heart rate less than 55 beats min l) is present. Sudden preoperative cessation may be associated with rebound angina, myocardial infarction, arrhythmia or hypertension perioperatively. Intravenous atropine or glycopyrrolate may be given before induction or, if undue bradycardia occurs, intra-operatively. p-Blockers may contribute to and...

Adverse cardiac events

Over 20 years ago, Goldman and colleagues published a retrospective analysis of preoperative risk factors which were associated with an adverse cardiac event following non-cardiac surgery (Table 34.6). This topic has been re-evaluated extensively in the intervening years, with many studies agreeing broadly with Goldman's conclusions. However, conflicting opinions exist regarding identification of the most accurate predictors, prob Table 34.4 Typical features which may increase the likelihood of...

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...

Afferent Limbs Of Vomiting Reflex Gastrointestinal tract

Information from mechano- and chemoreceptors in the gastrointestinal tract is relayed via the vagus nerve to the nucleus tractus solitarius in the brain stem. Abnormal gastric or intestinal distension, increased smooth muscle contraction and abnormal or toxic gastrointestinal contents can trigger the vomiting reflex. Peripheral 5-HT3 receptors are intimately involved in this system. Radiation, chemotherapy and other toxins release 5-HT from chromaffin cells in the gut, which stimulates vagal...

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...

Amiloride and triamterene

Amiloride acts directly on the distal tubule and collecting duct. It causes potassium retention and an increase in sodium loss. After oral intake, up to 25 is absorbed, onset of its peak effect is within 6 h, and it is then excreted unchanged in the urine. Amiloride is almost always used in combination with thiazide or loop diuretics. It then has a synergistic action in terms of diuresis, although it opposes the potassium loss. Amiloride has few side-effects. Hyperkalaemia and acidosis may...

Anaesthesia For Cervical Spine Surgery

The cervical spine can be approached from either the anterior or the posterior route, depending largely upon the site of cord compression. Although the posterior approach is less likely to damage any vital structures, the patient must lie prone, and hypotension, blood loss and access, particularly in a large individual, may all cause problems. Preoperative assessment is perhaps one of the most important in neurosurgical anaesthetic practice, because an unstable cervical spine is a major reason...

Anaesthesia for ENT surgery

Two hundred and seventy thousand ear, nose and throat operations are performed in the UK each year, accounting for approximately 5 of the workload of an anaesthetic department. Patients are usually young and healthy and the average hospital stay is short (less than 3 days). Many operations are performed as day cases, thereby reducing the need for in-patient admission. Children and young adults are frequently apprehensive and require reassurance. Some may have an atopic history which influences...

Anaesthesia For Radiological Procedures

In most hospitals, the anaesthetic department is called upon to anaesthetize patients for diagnostic and therapeutic radiological procedures. These procedures include angiography, computed tomography (CT) scanning and magnetic resonance imaging (MRI). The major requirement of all these imaging techniques is that the patient remains almost motionless. Thus, anaesthesia may be necessary when these investigations are performed in children, the critically ill or the uncooperative patient. The...

Anaesthesia For Strabismus Surgery

The commonest procedure in paediatric ophthalmic surgery is correction of squint. The eye should be immobile with absent muscle tone. The use of a non-depolarizing muscle relaxant may be preferred as this prevents variation in muscle tone which may occur with an imbalance between the depth of anaesthesia and the applied surgical stimulus. Succinylcholine must be avoided. In patients who have had previous strabismus surgery or orbital trauma, the surgeon may need to differentiate between paretic...

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 history

Details of the administration and outcome of previous anaesthetic exposure should be documented, especially if problems were encountered. Some sequelae such as sore throat, headache, or postoperative nausea may not seem of great significance to the anaesthetist but may form the basis of considerable preoperative anxiety for the patient. Previous anaesthetic records should be examined if available, as more serious problems such as difficulty with tracheal intubation should have been documented....

Anaesthetic Implications Of Laparoscopic Surgery

An appropriate vein should be cannulated with a large-gauge cannula. The choice of induction and maintenance agent is not important. As there is a risk of severe bradycardia, some anaesthetists give glycopyrrolate 0.2 mg or atropine 0.3 mg at induction. There is a high incidence of postoperative nausea and vomiting (PONV) after laparoscopy, especially following gynaecological procedures. An antiemetic should be given prophylactically. In several studies of short laparoscopic procedures, there...

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...

Anaesthetic technique

TURP is frequently performed in very elderly men. These patients have a high incidence of concomitant disease, especially of the respiratory tract and cardiovascular system. There is a risk of septicaemia in those patients with urinary tract infection, stones in the bladder or an indwelling catheter. These patients should have intravenous antibiotics, as should any patient with a joint prosthesis or valvular heart disease. Spinal anaesthesia is useful particularly for patients with significant...

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...

Angiotensinconverting Enzyme Ace Inhibitors

Many patients with hypertension or cardiac failure have an increased activity of the renin-angiotensin-aldosterone system. This leads to an elevated systemic vascular resistance, further decreases in cardiac output and renal perfusion, and more sodium and fluid retention. These patients are often receiving diuretic treatment, which in itself triggers renin activity. The ACE inhibitors (e.g. captopril, enalapril, lisinopril) are being used increasingly in this scenario, in place of, or in...

Anticholinesterase drugs

These drugs (e.g. neostigmine, pyridostigmine) antagonize acetyl cholinesterase, thereby decreasing the breakdown of released ACh they exert both nicotinic and muscarinic effects. The action on the ANS tends to appear at low doses, as nicotinic effects are dose-related. They are used in anaesthesia to reverse the neuromuscular blockade of non-depolarizing muscle relaxants (see Ch. 19). Their other uses include the diagnosis and symptomatic management of myasthenia gravis, where pyridostigmine...

Antidiuretic Hormone Vasopressindesmopressinddavp

Antidiuretic hormone (ADH) is a naturally occurring hormone, produced in the hypothalamus, transported by nerve axons down to the posterior pituitary gland and, from there, secreted into the blood. The release of ADH is regulated by the osmolality of the extracellular body fluids, changes in arterial pressure and intravascular volume, and the sympathetic nervous system. An increase in blood osmolarity and hypovolemia stimulate the hypothalamic osmoreceptors and arterial baroreceptors as part of...

Any surgical procedure on the lower limbs or perineum

For patients with medical problems, low SAB may be the anaesthetic technique of choice Metabolic disease. Diabetes mellitus. Respiratory disease. Low SAB has no effect on ventilation and obviates the requirement for anaesthetic drugs with depressant properties. There is some evidence that SAB may reduce the incidence of chest infection. Cardiovascular disease. Low SAB may be valuable in patients with ischaemic heart disease or congestive cardiac failure, in whom a small reduction in preload and...

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...

Renal function tests

Inulin clearance - glomerular filtration Para-aminohippuric acid clearance renal plasma flow Creatinine clearance - glomerular filtration rate (overestimates low glomerular filtration rate) 100-150 ml min-1 560-830 ml min-' 104-125 ml min-1 280-300 mosmol kg-l 45-120 (tmol L-l 2.7-7.0 mmol L-l 1.6-3.3 mmol L-l 300-1200 mosmol kg-i 8.85-17.7 mmol per 24 h 50-200 mmol per 24 h SG, specific gravity U, urine P, plasma. SG, specific gravity U, urine P, plasma.

Applied Anatomy Of The Orbit

The orbit is a four-sided bony pyramid with its base pointing anteriorly and its apex posteromedially. The medial walls of the right and left orbits are parallel to each other (see Figs 47.3 and 47.4). The mean distance from the inferior orbital margin to the apex is 55 mm. This has important implications when injections are made into the orbit. The deeper the injection, the narrower is the space, and the greater the chance of causing damage to the structures within. The inferotemporal quadrant...

Arachidonic acid metabolites

Continuous infusion of PGI2 has been used in pulmonary hypertension, but systemic hypotension may be a problem. Non-steroidal anti-inflammatory drugs such as indomethacin or aspirin inhibit production of PGI2 these agents may accentuate hypoxic pulmonary vasoconstriction. Inhalation of 100 oxygen for at least 10 min is sufficient to demonstrate a change in most cases. Tolazoline hydrochloride (an a-antagonist and a directly acting vasodilator) in a dose of...

Assessment History

Of the six cardinal symptoms of respiratory disease (cough, sputum, haemoptysis, dyspnoea, wheeze and chest pain), dyspnoea provides the best indication of functional impairment. Specific questioning is required to elicit the extent to which activity is limited by dyspnoea. Dyspnoea at rest or on minor exertion clearly indicates severe disease. A cough productive of purulent sputum indicates active infection. Chronic copious sputum production may indicate bronchiectasis. A history of heavy...

Assessment Of Consciousness

Awareness, with or without pain, is an important complication of general anaesthesia and may result in litigation. It is important, Table 38.13 Uses of monitors of cerebral function Avoidance of awareness during anaesthesia therefore, that an anaesthetist strives to maintain unconsciousness. Unfortunately, at present, there is no reliable monitor and the anaesthetist relies upon administering an adequate dose of anaesthetic whilst observing for signs of light anaesthesia (excess sympathetic...

Assessment Of The Pregnant Woman Presenting For Anaesthesia And Analgesia

Successive CEMD reports highlight the problems of women with intercurrent medical disease and the fact they are at increased risk in pregnancy and labour. There are many more women with a Table 52.5 Clinical methods to assess the airway Mouth opening (5 cm interincisor gap, equivalent to two lingers Temporomandibular joint mobility (should be able to protrude lower incisors in front of upper incisors) Neck mobility (90 flexion of head on neck) Weight > 100 kg increases risk Risk of airway...

Autonomic ganglion blocking drugs

Trimetaphan is the only member of this group of drugs still in clinical use in the past, hexamethonium and pentolinium were also available. Trimetaphan acts within 2 min of the start of an infusion and is metabolized rapidly by plasma cholinesterases. It decreases the excitability of postganglionic neurones, largely at the nicotinic acetylcholine receptor sites. Its action at muscarinic receptors is minor. The major action of the drug is arterial vasodilatation, but blockade of sympathetic...

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...

Awake intubation

Although blind nasal intubation is a valuable skill, the introduction of the narrow-bore fibreoptic intubating laryngoscope has replaced it as the technique of choice in those patients who are likely to develop unrelievable airway obstruction when loss of consciousness occurs (e.g. trismus from dental abscess or a known difficult intubation). Before embarking on awake fibreoptic nasal intubation, it is necessary to render the nasopharynx and, to a greater or lesser extent, the upper airway...

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...

Basic Definitions

An acid is a substance that dissociates in water to produce H+ a base is a substance that can accept H+. Strong acids dissociate Tabic 39.7 Treatment of hyperkalemia Calcium gluconate 10 i,v. (0.5 ml kg-' to maximum of20 m ) given over 5 min. No change in plasma JK+ . Effect immediate but transient Glucose 50 g (0.5-1 0 g kg-1 ) plus insulin 20 units (0.3 unit kg-1) as single i.v. bolus dose. Then infusion of glucose 20 , plus insulin 6-20 units h_1 (depending on blood glucose) Sodium...

Benzodiazepines

These drugs were developed initially for their anxiolytic and hypnotic properties and largely replaced oral barbiturates in the 1960s. As parenteral preparations became available, they rapidly became established in anaesthesia and intensive care. All benzodiazepines have similar pharmacological effects their therapeutic use is determined largely by their potency and the available pharmaceutical preparations. Benzodiazepines are often classified by their duration of action as long-acting (e.g....

Blood Transfusion And Postoperative Immunocompetent

It is well recognized that blood transfusion suppresses some aspects of the immune response, causing depressed delayed hypersensitivity reactions, decreased NIC cell activity, decreased Th helper cells and decreased IL-2 production. Although there are several theories to explain these effects, the explanation is still not clear, nor is it clear which of the components of the blood transfusion are responsible for the changes. It does, however, appear that the donor leucocytes carrying foreign...

Body Fluids And Compartments

Total body water in males is approximately 60 of total body weight, i.e. 42 L for a 70 kg man. In females, total body water is approximately 10 less, because of the greater proportion of body fat compared with males fat cells have a lower water content than other cells of the body. The water is distributed in various spaces or compartments Intracellular fluid. This is the largest water compartment in the body, representing two-thirds of total body water (approximately 28 L). Extracellular...

Bronchial Carcinoma

Patients with bronchial carcinoma frequently suffer from coexisting chronic bronchitis. In addition, there may be infection and collapse of the lung distal to the tumour. Patients with bronchial carcinoma may have myasthenic syndrome (see p. 452), while oat-cell tumours may secrete a number of hormones, among the commonest being adrenocortico trophic hormone (ACTH), producing Cushing's syndrome, and antidiuretic hormone (ADH), producing dilutional hyponatraemia (syndrome of inappropriate ADH...

Burns

Death in victims of tire is usually caused by hypoxaemia, resulting either from a reduction in inspired oxygen concentration in a smoke-filled atmosphere or from poisoning by products of combustion. Carbon monoxide has an affinity for haemoglobin over 200 times greater than that of oxygen and high concentrations cause reduced oxygen carriage in the blood. The oxygen dissociation curve is distorted and shifted to the left, resulting in reduced oxygen delivery to the tissues. Inhalation of smoke...

Calcium channel blockers

These drugs (Table 35.3) block the slow influx of calcium ions which contribute to depolarization. Verapamil, which acts predominantly on the atrioventricular (AV) node, is used in the management of supraventricular tachyarrhythmias, angina, hypertension and hypertrophic obstructive cardiomyopathy. As it increases AV block, concurrent use with digoxin or p-blockers should be avoided, as should halothane and enflurane anaesthesia. Nifedipine, which acts predominantly on vascular smooth muscle,...

Capacitance And Resistance Vessels

The highly muscular layers in the peripheral arterial system enable the arterioles (defined as vessels with an internal diameter of less than 0.5 mm) to act as resistance vessels. The relationships between pressure, flow and resistance detailed below in the control of arterial pressure also hold true at the tissue level. The resistance generated in the peripheral arterioles, in the face of an adequate cardiac output, controls capillary (and therefore tissue) perfusion pressure. These vessels...

Carbon dioxide tension

This is controlled during conventional ventilation by changing the respiratory rate and or tidal volume. It is desirable to minimize the changes in Pacc> 2 (especially if initially elevated), because too rapid a reduction may lead to decreases in cerebral blood flow, cardiac output and arterial pressure. In patients with normal or low PaCC> 2 before IPPV, minute volume should be adjusted to produce a PaCO2 of 4.5-5 kPa, a value at which spontaneous ventilatory efforts should be minimal. If...

Cardiac catheterization

General anaesthesia is required mainly for children (rarely in adults as sedation is usually adequate). In children, congenital heart disease may cause abnormal circulations and intracardiac shunts, which often present with cyanosis, dyspnoea, failure to thrive and congestive heart failure. Radiological procedures include pressure and oxygen saturation measurements, balloon dilatation of stenotic lesions (e.g. pulmonary valve), balloon septostomy for transposition of the great arteries and...

Cardiac glycosides

Digoxin and digitoxin are cardiac glycosides whose structure consists of a cyclopentanophenanthrene nucleus, an aglycone ring (responsible for the pharmacological activity) and a carbohydrate chain made up of sugar molecules (which solubulize the drug). They are all derived from plant sources, principally digitalis purpura and digitalis lanata. Digitalis compounds have been used for over 200 years for the treatment of cardiac failure but have now been largely superseded and are principally...

Cardiopulmonary resuscitation

Cardiopulmonary resuscitation (CPR) is required when the supply of oxygen to the brain is insufficient to maintain function. Oxygen delivery is dependent upon cardiac output, haemoglobin concentration and saturation of haemoglobin with oxygen this depends predominantly on respiratory function. CPR is required most commonly after cardiac arrest, respiratory arrest or a combination of the two. The brain is more sensitive to hypoxaemia than any other organ, including the heart. It has a limited...

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...

Cardiovascular system

Peripheral resistance and cardiac output may be reduced because of residual effects of anaesthetic drugs in the absence of surgical stimulation. Hypovolaemia may be present because of inadequate fluid replacement during surgery, continued bleeding postoperatively or expansion of capacitance of the vascular system as a result of rewarming. Cardiac output may also be reduced as a result of arrhythmias or pre-existing disease. Hypertension may occur as a result of increased sympathoadrenal...

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)...

Central conduction time CCT

This is the time delay between an action potential generated in the brain stem and the first cortical potential recordable (normally less than 6.4 ms). Other times are also described, e.g. the dorsal column to cortex conduction time. CCT is independent of body size and peripheral nerve conduction velocity and is probably also independent of body temperature and barbiturate concentrations. Changes result from cortical dysfunction, abnormal synaptic delay in the thalamus or cortex (or both) and...

Central nervous system depressants

Suppression of the baroreceptor reflex and depression of the vasomotor centre cause a progressive decrease in arterial pressure. Depression of local autonomic control also leads to a decrease in arterial pressure because of vasodilatation or cardiac depression. All anaesthetic drugs depress the cardiovascular system, although they vary in their precise actions for example, halothane causes primarily depression of cardiac output, whereas isoflurane, desflu-rane and sevoflurane are predominantly...

Cerebral angiography

This may be performed to demonstrate tumours, arteriovenous malformations, aneurysms, subarachnoid haemorrhage and cerebrovascular disease. The risk of complications is generally increased in the elderly and those with pre-existing vascular disease, diabetes, stroke and transient ischaemic attacks. Many of these patients have intracranial hypertension. Therefore, control of arterial pressure and carbon dioxide tension is essential if these patients require general anaesthesia. Obtunding the...

Chemical pathology biochemical values

These values are given for example only - each reporting laboratory provides reference values for its own population and method. This is especially true of enzyme assays. Values given are those obtained from Chemical Pathology in Warwick, where these are available. No inference should be made about the molecular weight of a substance by reference to US and SI values Dibucaine number > 80 usually normal Dibucaine number < 20 usually homozygote for atypical Conversion chart - hydrogen ion...

Choice Of Anaesthesia

Ophthalmic surgery can be carried out under either local or general anaesthesia. The type of surgery, planned duration, age and fitness of the patient influence the choice (Table 47.2). Usually, local anaesthesia is preferred for older patients, as the stress response to surgery is diminished and complications such as postoperative confusion, nausea, vomiting and urinary retention are mostly eliminated. Younger patients are often too anxious for local anaesthesia and are usually managed with...

Choice Of Nsaid

NSAIDs have the potential to reduce pain, especially late postinflammatory pain, and are usually more effective for dental- and orthopaedic-generated pain than are the weak opioids. Ibuprofen is recommended as the first-line NSAID for simple analgesia because it has the lowest number of adverse reactions reported per unit number of prescriptions. Diclofenac is popular because it is available in several formulations. Ketorolac is the first choice for intravenous administration because of its...

Cholesterol metabolism

Cholesterol is a 27-carbon steroid molecule used in the synthesis of cell membranes, steroid hormones, bile acids and vitamin D. Although most cholesterol is obtained from the diet, the liver is an important site of synthesis. In health, the synthesis and excretion of cholesterol is closely controlled to avoid cholesterol accumulation. Cholesterol is synthesized in a series of reactions in the cell cytoplasm. Initially, three acetyl-CoA molecules are used to form a five-carbon isoprene unit and...

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...

Class lb

Class lb drugs are useful for the prevention and treatment of premature ventricular contractions, ventricular tachycardia and ventricular fibrillation, particularly associated with ischaemia. Lidocaine is the first choice drug for ventricular arrhythmias resistant to DC cardioversion. It decreases normal and abnormal automaticity and decreases action potential and refractory period duration. The threshold for ventricular fibrillation is raised, but it has minimal haemodynamic effects. The...

Clinical

Continuous direct observation of the colour of the patient and movement of the chest and the reservoir bag in the breathing system is essential for safe anaesthesia. Both anaesthetic agents and opioids are potent depressants of respiration and hypoxic brain damage can occur in a few minutes. In cases where the patient is breathing spontaneously, constant observation is needed to detect tracheal tug, paradoxical chest movement and failure of the reservoir bag to move, indicating partial or...

Clinical Effects

Calcium channel blockers differ in their selectivity for cardiac muscle cells, conducting tissue and vascular smooth muscle, but to some degree they all decrease myocardial contractility and produce coronary and systemic vasodilatation with a consequent decrease in arterial pressure. Therefore, they have been used widely for the treatment of hypertension, angina and vasospastic disorders, but have been superseded in some areas by newer drugs. Verapamil and diltiazem also decrease SA node...

Clinical effects and treatment

Metabolic acidosis results in widespread physiological disturbances, including reduced cardiac output, pulmonary hypertension, arrhythmias, Kussmaul respiration and hyperkalemia the severity of the disturbances is related to the extent of the acidaemia. Treatment should be directed initially at identifying and reversing the cause. If acidaemia is considered to be life-threatening (pH < 7.2, HCO3- < 10 mmol L-l), measures may be required to restore blood pH to normal. Overzealous use of...

Clinical Factors Affecting Drug Profile

Increasing the dose of a drug shortens its onset time and increases the duration of block. Dose may be increased by using either a higher concentration or a larger volume a large volume of a dilute solution is usually more effective. The site of injection also affects onset time and duration (in addition to potential toxicity). Onset is almost immediate after infiltration and is progressively delayed with subarachnoid, peripheral nerve and epidural blocks, respectively. The slowest onset...

Clinical features

In a severe hypersensitivity reaction, a flush may develop over the upper part of the body. There is usually hypotension, which may be profound. Cutaneous and glottic oedema may develop and may result in hypovolaemia because of loss of fluid from the circu- Tabtc 14.7 Management of allergic reactions * Restore intravascular fluid volume * Inhibit further release of chemical mediators Epinephrine (cither i.v. or i.m., depending on the severity of the reaction) 0.5 ml of 1 1000, repeated until...

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...

CNS effects

The characteristic CNS effects seen with all benzodiazepines are as follows. Anxiolysis occurs at low dosage and these drugs are used extensively for the treatment of acute and chronic anxiety states. Longer-acting oral drugs such as diazepam and chlordiazepoxide have a place in the management of acute alcohol withdrawal states. Anxiolysis is very useful in premedication and during unfamiliar or unpleasant procedures. Sedation occurs as a dose-dependent depression of cerebral activity, with...

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...

Colonic Bacteria

The are few bacteria in the jejunum, more in the ileum, but large numbers in the colon. Colonic bacteria include not only bacilli, such as Escherichia coli and Enterobacter aerojjenes, but also pleomorphic organisms such as Bacteroides fragilis and cocci of various types. They have beneficial and potentially harmful effects. Some microorganisms synthesize vitamin K and several of the B complex vitamins. Folic acid produced by bacteria is absorbed in significant amounts. Furthermore, short-chain...

Colonic Motility

The ileocaecal valve is normally closed and prevents reflux of colonic contents into the ileum. It opens when a peristaltic wave arrives, allowing ileal contents to enter the caecum. Passage into the caecum also increases when it relaxes in response o chyme leaving the stomach (gastroileal reflex). Colonic motility patterns include stationary segmental contractions, mass movement and defaection. Stationary segmental contractions are of longer duration than those in the small intestine but their...

Complications Intraoperative

The incidence should be less than 0.5 in experienced hands. It usually occurs with the needle rather than the catheter and is immediately obvious because of the free flow of CSF. Puncture of the dura with a large epidural needle leads to a high incidence of headache. If this occurs, epidural block should be produced at an adjacent space, and 0.9 saline 40 ml hH should be infused epidurally for 36 h after surgery or labour to reduce the likelihood of headache. Simple analgesics may...

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 Extubation

This may take place with the patient supine if the anaesthetist is satisfied that airway patency can be maintained by the patient in this position and there is no risk of regurgitation. In patients at risk of regurgitation and potential aspiration, the lateral position is preferred. However, it is safer to employ the lateral recovery position after extubation (Fig. 37.5). Return of respiratory reflexes is signified by coughing and resistance to the presence of the tracheal tube....

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...

Consequences of hypernatraemia

The major clinical manifestations of hypernatraemia involve the central nervous system. Severity depends on the rapidity with which hyperosmolality develops. Acute hypernatraemia is associated with a prompt osmotic shift of water from the intracellular compartment, causing a reduction in cell volume and water content of the brain. This results in increased permeability and even rupture of the capillaries in the brain and subarachnoid space. The patient may present with pyrexia (a manifestation...

Control Of Arterial Pressure

Systemic arterial pressure is normally controlled closely in order to maintain the driving pressure needed for tissue perfusion. Normal values vary depending on both age and gender (Table 6.1), in Changes in arterial pressure, cardiac output and systemic vascular resistance with age addition to physiological changes including sleep. However, measurement of a 'normal' or even elevated arterial pressure is no guarantee of adequate tissue perfusion. Mean arterial pressure (MAP) is the average...

Control of blood glucose

This is assessed by inspection of the patient's urine-testing or BM-testing records, by random blood glucose measurements, by a 24 h blood glucose profile in patients receiving insulin, and by measurement of glycosylated haemoglobin (Hb A c). Whenever possible, blood glucose concentration should be maintained between 6 and 10 mmol L l, and insulin dosages should be adjusted to achieve this, with the introduction of twice-daily short- and intermediate-acting insulins if necessary. The serum...

Control Of Respiration

Respiration is regulated by the respiratory neurones (often known as the respiratory centre) to maintain homoeostasis. Arterial carbon dioxide tension (Pacc> 2) is regulated at about 5.3 kPa (40 mmHg) and thus under normal circumstances the main determinant of the minute ventilation (Fg) is the production of carbon dioxide (FCO2), which in turn is determined by the metabolic activity of the body and the energy substrate. Ventilation is greater on a carbohydrate-based diet respiratory quotient...

Control of urine volume and osmolality

In health, plasma osmolality is maintained between 280 and 290 mosmol kg-1, despite often large variations in daily fluid and electrolyte intake. In states of relative dehydration, the kidney minimizes water excretion, so small volumes of hyperosmolar urine are produced. Conversely, in overhydration, the kidney produces large volumes of dilute hypo-osmolar urine. The kidney is so efficient in this process that it can produce urine with an osmolality between varying 60 and 1200 mosmol kg l,...

Critical Incidents

These are incidents that could or do lead to death, permanent disability or prolongation of hospital stay. Most critical incidents in anaesthesia are detected before damage occurs their incidence is 400-500 times greater than that of death or serious injury attributable to anaesthesia. It has been estimated that a Table 33.6 Untoward an aesthetic-related events (other than death or cerebral damage) reported to the Medical Defence Union between 1970 and 1982 Table 33.6 Untoward an...

CSF shunt insertion and revision

The majority of patients who present for insertion or revision of ventriculoperitoneal shunts are children with congenital hydrocephalus, usually resulting from spina bifida. Some patients require a permanent shunt after intracranial haemorrhage or head injury, particularly the elderly. The major anaesthetic considerations lie in the presentation of a patient with severely raised ICP who may be drowsy, nauseated and vomiting, with resultant dehydration. Compensatory systemic hypertension to...

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...

Daycare Orthopaedic Procedures

Principles of anaesthesia for day-care surgery are discussed in detail in Chapter 50. They include prompt pain relief and treatment of nausea and vomiting to allow early discharge. As with many procedures, the occasional day-case anaesthetist or surgeon is well advised to adopt the techniques of the more experienced. For orthopaedic procedures, postoperative pain is minimized if a local or regional anaesthetic block is used intraoperatively, with or without sedation or general anaesthesia....