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...

Analgesia

Simple, non-opioid analgesics and or local and regional techniques should be used if possible. Non-steroidal anti-inflammatory drugs (NSAIDs) such as diclofenac and piroxicam are useful in reducing the opioid requirements following major surgery, and may be adequate on their own after minor surgery. Fifty per cent nitrous oxide in oxygen (Entonox) is useful for physiotherapy and painful procedures. Opioid analgesics are best administered, where necessary, in small i.v. doses, e.g. morphine 2...

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...

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...

Abnormal impulse conduction

Block of conduction between the SA node and ventricular cells may be partial or complete. Slowing of conduction near the AV node or in the AV bundle results in prolongation of the PR interval on the ECG (first degree heart block). If the block worsens, this can progress to a situation where some atrial beats are not followed by ventricular beats (second degree heart block). Finally a situation may develop in which no atrial impulses pass to the ventricles, which then beat at a slower...

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...

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 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...

Adverse reactions to intravenous anaesthetic ag en ts

These may take the form of pain on injection, venous thrombosis, involuntary muscle movement, hiccup, hypotension and postoperative delirium. All of these reactions may be modified by the anaesthetic technique. Hypersensitivity reactions, which resemble the effects of histamine release, are more rare and less predictable. Other vasoactive agents may also be released. Reactions to i.v. anaesthetic agents are usually caused by one of the following mechanisms Type I hypersensitivity response. The...

Aetiology

Sinus bradycardia originates from the sinoatrial node. It is common during anaesthesia in healthy patients and is associated with the use of opioids or deep levels of anaesthesia. Surgical manipulations such as eyeball traction, cervical dilatation and peritoneal traction can increase vagal tone, producing bradycardia and occasionally sinus arrest. Drugs are a common cause of bradycardia. Succinylcholine can produce a profound decrease in heart rate, especially following repeat doses....

Airway obstruction

Airway obstruction caused by the tongue, by indrawing of the pharyngeal muscles or by blood or secretions in the pharynx is ameliorated by placing the patient in the lateral or recovery position (see Fig. 37.5, p. 468). This position should be used for all unconscious patients who have undergone oral or ear, nose and throat surgery, and for patients at risk of gastric aspiration. Partial obstruction of the airway is characterized by noisy ventilation. As the obstruction increases, tracheal tug...

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

A light premedication with benzodiazepine or opioid analgesic is satisfactory. Minor procedures, e.g. to establish vascular access for dialysis, are carried out most satisfactorily under regional anaesthesia brachial plexus block for upper limb and combined femoral and sciatic block for lower limb. Patients who suffer from acute renal failure, and those receiving long-term dialysis for chronic renal failure, may require dialysis before surgery to correct fluid overload, acid-base disturbances...

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...

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...

Anticholinesterases

These agents are used in clinical practice to inhibit the action of acetylcholinesterase at the neuromuscular junction, thus prolonging the half-life of acetylcholine and potentiating its effect, especially in the presence of residual amounts of non-depolarizing muscle relaxant at the end of surgery. The most commonly used anticholinesterase during anaesthesia is neostigmine, but edrophonium and pyridostigmine are also available. These carbamate esters are water-soluble, quaternary ammonium...

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...

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...

Atrial arrhythmias

These can reduce the atrial contribution to left ventricular filling, resulting in a decrease in cardiac output. Premature atrial contractions are common and of little importance. Junctional rhythm. This bradycardia is associated usually with the use of halothane. A reduction in concentration and or a change of volatile agent are indicated. An anticholinergic drug may be required to restore sinus rhythm. Accelerated nodal rhythm. This may be precipitated by an increase in sympathetic tone in...

Atrial Pressure Changes During The Cardiac Cycle

Pressures within the right and left atrial chambers show several fluctuations during the cardiac cycle, producing characteristic waveforms, which may be seen during central venous and pulmonary artery monitoring. The waveform is described in terms of a-, c- and v-waves, and x- and y-descents. The a-wave occurs just after the P wave on the ECG and is caused by atrial contraction at the end of ventricular filling. Ventricular systole then follows, and as the ventricles contract, the AV valves are...

Avogadros hypothesis

Avogadro's hypothesis states that equal volumes of gases at the same temperature and pressure contain equal numbers of molecules. Avogadro's number is the number of molecules in 1 g molecular weight of a substance and is equal to 6.022 x 1023. Under conditions of standard temperature and pressure, 1 g molecular weight of any gas occupies a volume of 22.4 litres (L). These data are useful in calculating, for example, the quantity of gas produced from liquid nitrous oxide. The molecular weight of...

B

The simple barometer described by Torricelli. A. Filled with mercury. B. Filled with water. They minimize fluctuations in the pressure within an anaesthetic machine, which would necessitate frequent manipulations of flowmeter controls. Modern anaesthetic machines are designed to operate with an inlet gas supply at a pressure of 3-4 bar (usually 4 bar in the UK). Hospital pipeline supplies also operate at a pressure of 4 bar and therefore pressure regulators are not required between a hospital...

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...

Bupivacaine

The introduction of bupivacaine represented a significant advance in anaesthesia. Relative to potency, its acute central nervous sys tem toxicity is only slightly lower than that of lidocaine, but its longer duration of action reduces the need for repeated doses, and thus the risks of cumulative toxicity. Several deaths have occurred after accidental intravenous administration of large doses of bupivacaine, and some concern has been expressed that this drug might have a more toxic effect on the...

The heart

The two atria serve as reservoirs for blood and as accessory pumps to augment ventricular filling. The right and left ventricles act as pumps propelling blood around the pulmonary and systemic circulations. To function effectively, the full heart chambers must be excited rhythmically and in the proper sequence. The ventricular muscle cells must contract synchronously, with the cells at the apex of each ventricle contracting first to squeeze blood into the...

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 Arrest And Resuscitation

The results of treating cardiac arrest in children are poor. If resuscitation results in survival, the incidence of significant neurological Table 53.10 Paediatric resuscitation chart Size (4 + age 4) cm Length (oral) cm Epinephrine 1 10 000 i.v. i.o. e.tJ 0.1 ml kg-t repeated as necessary Sodium bicarbonate 8.4 1 ml kg-' i.v. Atropine 500 ftg in 5 ml 0,2 ml kg' i.v. e.t. .v., intravenous i.o., intraosseous e.t., endotracheal. 3 For endotracheal administration, give 10 times .v. dose. N.B. All...

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...

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...

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...

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...

Cerebrospinal Fluid

Cerebrospinal fluid (CSF) is formed by secretory cells of the choroid plexus which project into the lateral, third and fourth ventricles (Fig. 12.12). CSF then flows via the third ventricle through the aqueduct and fourth ventricle to escape by two lateral foramina of Luschka and the median foramen of Magendie into the subarachnoid space around the brain and spinal cord. The total volume of CSF is approximately 140 ml in the adult approximately 50 is intracranial, and the remainder occupies the...

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...

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 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...

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...

Clinical uses

Dopamine is often used to preserve regional blood flow, but its perceived effectiveness is based largely on anecdotal reports and experimental data. Improved haemodynamics, renal vasodilatation and increase in renal blood flow do have diuretic and natriuretic effects. Because the urine output of the critically ill patient is considered a good marker of tissue perfusion by many clinicians, the diuretic properties of dopamine are valued. However, clinical studies have not demonstrated any benefit...

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...

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...

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...

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...

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...

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 Used To Modify The Progress Of Disease

Methotrexate modifies the disease process of rheumatoid arthritis, but affects both liver function and leucocyte production. Both methotrexate and steroids reduce immune competence, and sterile techniques for invasive anaesthetic procedures should be used. Patients who take steroids regularly to control inflammatory conditions may be unable to increase endogenous steroid production in the postoperative period because of suppressed adrenocortical function. Partly because of unwanted effects,...

Elective repair

Consideration should be given to the collection and storage of the patient's own blood in the weeks preceding surgery. This may then be used as autologous blood transfusion perioperatively. All vasoactive medication must be continued up to the time of surgery and an anxiolytic premedication is advantageous. A 3-blocker in addition may decrease the incidence of perioperative myocardial ischaemia. An arterial and two large intravenous cannulae should be placed before induction of anaesthesia,...

Embolization procedures

The use of angiographic embolization continues to grow and become more sophisticated. It is undertaken for vascular malformations and fistulae, aneurysms, tumours, acute haemorrhage and ablation of function of an organ. Venous embolization is used to treat gastro-oesophageal varices, testicular varices and ablation of adrenal gland function. It may be performed as an alternative to surgery, particularly if the patient is unfit and the operation carries a high risk. Its use before surgery can...

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...

Field block for inguinal hernia repair

The main nerves which supply the groin are the subcostal (T12), iliohypogastric (LI) and ilioinguinal (LI). Their blockade produces good postoperative analgesia, but supplementary infiltration, especially around the internal ring and hernial sac, is usually necessary during surgery if this is the only anaesthetic employed. A needle is inserted 1.5 cm medial and inferior to the anterior superior iliac spine. Using a regional block needle,,.the external oblique aponeurosis is readily appreciated...

Fig 133

Rapidity of recovery from anaesthesia is inversely proportional to the solubility of the anaesthetic the most rapid recovery is with the least soluble anaesthetic (desflurane). The difference is amplified by duration of anaesthesia (note that the difference in time of recovery between the least (desflurane) and most soluble anaesthetic (halothane) is greater after 2 h of anaesthesia than after 0.5 h of anaesthesia). (From Weiskopf 1995 with permission.) Halothane antagonizes bronchospasm and...

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...

Fluid Therapy

An intravenous infusion delivering maintenance fluids should be in place for all neonates requiring surgery. Maintenance fluid requirements increase over the first few days of life (Tables 53.5 and 53.6). The normal infant requires of the order of 3-5 mmol kg-1 of sodium and an equivalent amount of potassium per day to maintain normal serum electrolyte concentrations. The ability of the infant's kidneys to eliminate excess sodium is limited. Exceeding this amount in the absence of loss results...

Full blood count

This provides information about the haemoglobin concentration, white blood cell count and platelet count, together with details of red cell morphology. Haemoglobin concentration tends to be of greatest interest to the anaesthetist. Patients whose ethnic origin or family history suggests that a haemoglobinopathy may be present should have haemoglobin concentration measured and haemoglobin electrophoresis undertaken if it has not been performed previously or if the result is not available. If...

Further Reading

Guyton A C, lones C E, Coleman T G 1973 Circulatory physiology cardiac output and its regulation. W B Saunders, Philadelphia Lowenstein C J, Dinerman J L, Snyder S H 1994 Nitric oxide a physiologic messenger. Annals of Internal Medicine 120 227-237 Magder S, De Varennes B 1998 Clinical death and the measurement of stressed vascular volume. Critical Care Medicine 26 1061-1064 Priebe H-J, Skarvan K 2000 Cardiovascular physiology, 2nd edn. BMJ Books, London Drugs acting on the cardiovascular and...

Gastric Secretions

Gastric glands secrete approximately 2 L day-1. Gastric secretions contain four main components hydrochloric acid, pepsin, mucus and intrinsic factor. Hydrochloric acid is necessary to release In some patients Anxiety PrcgnartCy ElectreHyte abnormalities Raised intracranial pressure Migraine Opioids 1 ail routes of administration ) (Parietal cells-HCI. intrinsic factor Chief cells-pep si nog en) (Parietal cells-HCI. intrinsic factor Chief cells-pep si nog en) Acetylcholine Gastrin Histamine...

Gastrointestinal Physiology And Antacid Therapy

Changes in smooth muscle tone occur early in pregnancy as a result of an increase in progesterone. This leads to a decrease in the tone of the lower oesophageal sphincter and, combined with the increased abdominal mass, results in an increased possibility of regurgitation and pulmonary aspiration of gastric contents. The pH of the gastric contents is lower, and therefore there is an increased incidence of heartburn in pregnancy. Gastric emptying is not delayed during pregnancy but is delayed in...

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...

Globulins

These are serum proteins which are classified into a-globulins, (3-globulins and y-globulins. The Y-globulins are immunoglobulins synthesized by plasma cells, but the liver synthesizes many a- and p-globulins. Serum globulins may be separated by serum electrophoresis. a-l-globulins include a-1-antitrypsin and a-1-acid glycoprotein. a-1-antitrypsin is a protease inhibitor and inherited disorders in its synthesis lead to cirrhosis and panacinar emphysema, a-1-acid glycoprotein is important for...

Gluconeogenesis Fig 224

Gluconeogenesis is defined as the production of glucose from non-carbohydrate sources. Maintenance of blood glucose is important, as it is the main fuel for the brain and red blood cells. In the fasted state, carbohydrate stores (in the form of liver glycogen) are depleted in 12-24 h. Therefore, alternative substrates are required for glucose synthesis by gluconeogenesis. The main substrates are amino acids (muscle breakdown), glycerol (triacylglyc-erol) and lactate (anaerobic metabolism in...

Glycogenesis Fig 225

Excess dietary glucose is converted into a readily accessible carbohydrate store in the liver and skeletal muscle termed glycogen. Glycogen is a highly branched polymer of glucose present in cell cytosol as granules. Because of its branched structure, it may be broken down rapidly by enzymes to glucose. Following a meal, liver and muscle glycogen stores increase, and are then used as a continual supply of glucose between meals. However, only liver glycogen may be used to increase blood glucose...

Heart block

This is discussed in Chapter 35 (p. 435). HYPOTENSION In healthy patients, hypotension during anaesthesia may be defined as a mean arterial pressure less than 60 mmHg. A systolic blood pressure 25 less than the patient's preoperative value also indicates hypotension, especially in patients with pre-existing hypertension. Hypotension is clinically significant if vital organ perfusion is compromised (e.g. myocardial ischaemia or oliguria). As left ventricular coronary blood flow occurs...

Hip Replacement

Most hip prostheses are of the 'cemented1 variety. The operation may be performed in either a supine or a modified lateral position. The femoral head is removed, and the new cup and femoral components are fixed to prepared bone with polymethylmethacrylate cement. Application and hardening of the cement, particularly after its insertion into the femoral shaft, are sometimes accompanied by sudden reductions in end-tidal CO2 concentration and blood pressure. Although attributable in part to toxic...

History And Examination

Thoracic patients often exhibit the respiratory symptoms of cough, sputum, haemoptysis, breathlessness, wheeze and chest pain, or oesophageal symptoms of dysphagia, pain and weight loss. Other common chest features are hoarseness, superior vena cava obstruction, pain in the chest wall or arm, Horner's syndrome, cyanosis and pleural effusion. Lung tumours may cause extratho-racic symptoms by metastatic spread, principally to brain, bone, liver, adrenals and kidneys, or by endocrine effects such...

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...

Hypercapnia

Hvpercapnia refers to carbon dioxide accumulation in the blood. During anaesthesia, this is indicated by an arterial carbon dioxide tension (kPa) or end-tidal carbon dioxide concentration ( ) greater than 6.0. Table 40.6 Causes of hypoxaemia during anaesthesia Oxygen s upply ( cylinder pipeline failure, misconnection ) Flowmeters (inaccurate settings, leak) Breathing svstem (obstruction, leak) Ventilator failure, inadequate minute volume-Breathing system (obstruction, leak, disconnection)...

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...

Hypotension

Hypotension is usually defined as a 25 decrease in systolic or mean arterial pressure or an absolute decrease of 40 mmHg. Small decreases in pressure are insignificant and may be associated with improved uteroplacental blood flow. Rapidly developing hypotension after spinal anaesthesia may cause unpleasant dizziness and nausea in about 50 of patients and should be treated with vaso pressors, e.g. ephedrine, until arterial pressure is restored, while at the same time maintaining normovolaemia...

Immunh Modulation Hy Anaesthetic Agents

Increased susceptibility to infection is common in postoperative patients, and although trauma, surgical stress and endocrine responses modify the immune response, anaesthetic agents also modulate immune function, as shown by in vitro studies of the responses of immunologically important cells to clinically relevant concentrations of anaesthetic agents. Both volatile and intravenous anaesthetic agents, and opioids such as morphine and fentanyl have been shown to suppress a variety of functions...

Immunology and body defences

The immune system in humans is a very adaptable system which has evolved to provide protection against both pathogenic invading organisms and cancer cells. This extremely complex system is able to recognize and eliminate a huge variety of foreign cells and molecules. An immune response may be classified functionally into recognition and response. Immune recognition is extremely specific, enabling discrimination between the subtle chemical differences which distinguish foreign pathogens from...

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...

Indications for the use of sedative drugs Premedication

'Sedo-analgesiaThis term describes the use of a combination of a sedative drug with local anaesthesia, e.g. in dental surgery or surgical procedures performed under regional blockade. The recent expansion in the development of minimally invasive sur gery makes this technique more widely applicable. Radiological procedures. Some patients, particularly children and anxious individuals, are unable to tolerate long and uncomfortable imaging procedures without sedation. Developments in the use and...

Indicator Dilution

An indicator is injected as a bolus into the right heart and the concentration reaching the systemic side of the circulation is plotted against time (Fig. 31.4). The average concentration is calculated from the area under the concentration-time curve divided by the duration of the curve. The cardiac output during the period of this measurement is the ratio of the dose of indicator to the average concentration. A Single injection indicator dilution curve showing distortion of downslope produced...

Indicators Of Cholestasis Bilirubin

Cholestasis is impaired excretion of bile into the duodenum. It may be caused by factors within the liver or extrahepatic causes (e.g. gallstones). laundice is present when the plasma bilirubin concentration is greater than 35 umol L l, although it is often not clinically detected until it is greater than 50 pmol L '. Two forms of bilirubin may be measured in the plasma - conjugated (water-soluble) and unconjugated (lipid-soluble) - although most laboratories report only total bilirubin...

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...

Influence Of Drugs On Renal Function

All anaesthetic agents may cause a generalized depression of renal function which is transient and clinically insignificant. However, nephrotoxic drugs can impair renal function permanently (Table 26.1). For example, they may lead to severe sodium and water depletion, reduction in renal blood supply, direct renal damage or Table 26.1 Mechanisms of drug-induced renal damage Sodium and water depletion Reduced renal perfusion Direct renal toxicity Urinary obstruction renal obstruction. Some drugs...

Influence Of Renal Disease On Pharmacokinetics

Renal disease may affect drug pharmacokinetics through several mechanisms. Acidic drugs bind mainly to albumin. In renal failure, a decrease in serum albumin, an increase in serum urea, and the competition of endogenous substrates and drug metabolites for plasma protein binding sites lead to a decrease in the plasma protein binding of drugs. Highly protein-bound drugs have an increased unbound, active, free fraction. Under these circumstances, there may be an increase in the volume of...

Lamotrigine

The usual maintenance dose is 150-200 mg daily. Lamotrigine is metabolized in the liver and has an elimination half-life of 22-36 h. Its metabolism is accelerated by enzyme-inducing anticonvulsants such as phenytoin, and its action is prolonged by the enzyme inhibition of sodium valproate. Lamotrigine does not influence the metabolism of other drugs. Adverse effects are confined largely to the CNS, and include headache, diplopia, sedation, ataxia and tremor. These develop more commonly when...