Used in text and appendices

Nomenclature for blood groups (after Landsteiner) antihaemophilic factor (factor VIII) proprionate acute physiological and chronic health evaluation activated partial thromboplastin time American Society of Anesthesiologists bone marrow-dependent (as in B cells) Boehringer Mannheim (makers of BM Stix blood glu closing capacity central conduction time coronary care unit Christiansen Douglas Haldane (effect) Confidential Enquiry into Perioperative Deaths (UK) cardiac index (cardiac output body...

Moxonidine

Moxonidine is a moderately selective imidazoline I -receptor agonist (Ii > (ij) which reduces central sympathetic drive by stimulation of medullary I -receptors. Systemic vascular resistance is reduced, but heart rate, stroke volume and pulmonary artery pressures are not affected. Cardiac output remains unchanged or increases slightly. Plasma epinephrine, norepinephrine and renin concentrations decrease. Moxonidine has minimal 02-related adverse affects (e.g. sedation, dry mouth, rebound...

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...

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...

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...

Acromegaly

Acromegaly is caused by increased secretion of growth hormone from eosinophil cell tumours of the anterior pituitary gland. If this occurs before fusion of the epiphyses, gigantism results. Problems for the anaesthetist include the following Upper airway obstruction may result from an enlarged mandible, tongue and epiglottis, thickened pharyngeal mucosa and laryngeal narrowing. Maintenance of a clear airway and tracheal intubation may be difficult, and postoperative care of the airway must be...

Acupuncture And Ponv

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

Acute Pain

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

Adrenergic agonists

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

Adverse effects

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

Allergic reactions

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

Anaesthesia

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

Anaesthetic 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

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...

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...

Arrhythmias

Ventricular failure Left or right ventricular failure may cause hypotension. Right ventricular failure is uncommon in the postoperative period and is secondary usually to acute pulmonary disease, e.g. ARDS. Left ventricular failure in the postoperative period is associated most commonly with perioperative myocardial infarction or overtransfusion. The peripheral circulation is poor. Usually, tachycardia is present and there is clinical and radiological...

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...

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...

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....

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...

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...

Cartilages

The skeleton of the larynx comprises five major cartilaginous components the thyroid, cricoid and epiglottic cartilages and the paired arytenoid cartilages. In addition, there are two smaller paired bodies the corniculate and cuneiform cartilages. The cartilages articulate at cricothyroid and cricoarytenoid joints which are acted upon by the intrinsic muscles of the larynx (see below). These cartilages and their relative positions are depicted in Figure 8.4 together with their associated...

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...

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...

Clonazepam

The usual maintenance dose is 4-8 mg daily in divided doses. It is also available as an intravenous preparation which has a place in the management of status epilepticus. Clonazepam is 90 protein-bound and undergoes hepatic metabolism with an elimination half-life of 30-40 h. The main disadvantage of clonazepam is its sedative effect. There is also a tendency to develop tolerance to its anti-epileptic activity, with an unfortunate rebound increase in seizure...

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...

Conduct of anaesthesia

If liver function is severely impaired, no premedication should be given. Otherwise, a light benzodiazepine premedication is suitable. The liver is particularly vulnerable to hypovolaemia, hypotension and hypoxia. During anaesthesia, cardiac output should be kept as stable as possible. Blood loss should be replaced promptly, and overall fluid balance maintained with CVP monitoring. Drugs which depress cardiac output or arterial pressure, including volatile anaesthetic agents and p-blockers,...

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...

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...

Dental anaesthesia

Anaesthesia and dentistry have a long historical association. Some of the first anaesthetics given were for dental extractions and the use of anaesthesia was quickly taken into dental practice in the late 19th century. Dental anaesthetic techniques have evolved in parallel with the changes in practice in other aspects of anaesthesia. The days of single operator anaesthetists and the 'black gas' induction (100 nitrous oxide) are now long gone. For many years, dental anaesthesia had been...

Distribution to other tissues

The anaesthetic effect of all i.v. anaesthetic drugs in current use is terminated predominantly by distribution to other tissues. Figure 14.1 shows this distribution for thiopental. The percentage of the injected dose in each of four body compartments as time elapses is shown after i.v. injection. A large proportion of the drug is distributed initially into well-perfused organs (termed the vessel-rich group, or viscera - predominantly brain, liver and kidneys). Distribution into muscle (lean)...

Dopamine receptors

Dopamine receptors occur in basal ganglia, the substantia nigra, corpus striatum and the limbic system. In the basal ganglia, dopamine is antagonistic to ACh. Absence of dopamine is an important aetiological factor in Parkinsonism. In the hypothalamus, dopamine is concerned with release of prolactin. Dopamine suppresses prolactin secretion and dopamine antagonists (e.g. metoclopramide) increase hyperprolactinaemia. A dopaminergic system connects the limbic cortex, basal ganglia and hypothalamus...

Drugs inhibiting gastric acid production

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

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,...

Ecg

A 12-lead electrocardiogram can demonstrate many acute or longstanding pathological conditions affecting the heart, particularly changes in rhythm or the occurrence of myocardial ischaemia or infarction. It has some value as a preoperative baseline in patients with known or potential cardiovascular disease, although in the resting state the trace may appear normal despite the presence of clinically significant coronary artery disease. More extensive investigations are available in many...

Epidural anaesthesia

Epidural anaesthesia was the regional anaesthetic of choice until pencil-point spinal needles were introduced. The disadvantages of epidural anaesthesia are that the onset of the block is longer than that for spinal anaesthesia and that the spread of the block may be patchy, often giving poor anaesthesia of the sacral roots. The cardiovascular stability that can be achieved with an epidural is excellent and this implies that the technique may be considered the anaesthetic of choice in some...

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...

Extracellular volume deficit

Assessment of extracellular fluid volume dcficit is difficult, as considerable losses must occur before clinical signs are apparent. Clinical acumen and a high index of suspicion are necessary to detect the subtle signs of lesser deficits. Guidance is obtained from the nature of the surgical condition, the duration of impaired fluid intake and the presence and severity of symptoms associated with abnormal losses (e.g. vomiting). At the time of the earliest radiological evidence of intestinal...

Factors affecting duration of nondepolarizing neuromuscular block

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

Factors affecting spread Table 432

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

Familial Periodic Paralysis

This is also associated with prolonged paralysis after administration of non-depolarizing muscle relaxants. INTERCURRENT DISEASE AND ANAESTHESIA Safety of drugs commonly used in clinical anaesthesia for patients with acute porphyrias Intravenous induction agents Inhalation agents Neuromuscular blockade reversal Local anaesthetics a-Agonists ND Sodium nitroprusside ND PS, possibly safe S, safe C, contentious ND, no data U, unsafe PL1, probably unsafe

Fig 472

Anatomy of the right orbit relationship of the four rectus muscles and the apex of the cone to the orbital nerve supply. CT scan of orbits taken in coronal view with the subject looking to the right. Note the almost parallel sides of the medial orbital walls optic nerve movement to left the optic nerve canal and optic nerve chiasma the proximity of the midbrain that the cataract has been removed from the right eye. MR, medial rectus muscle LR, lateral rectus muscle ON, optic nerve. through the...

Fig

Sagittal section of the larynx showing cartilages and'ligaments. The vestibular (quadrate) membrane joins the thyroid, epiglottic and arytenoid cartilages. At the laryngeal opening, its free upper border is contained within the aryepiglottic fold and incorporates the corniculate and cuneiform cartilages. The lower border runs between the thyroid and arytenoid cartilages and forms the framework for the vestibular fold (false vocal cord). The fissure between right and left vestibular folds is...

Fu Ther Reading

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

General principles of pharmacology and pharmacokinetics

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

Hepatic encephalopathy

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

History of allergy

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

Immunosuppression Prednisolone and azathioprine

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

Induction Of Anaesthesia

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

Intracranial tumours

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

Ligaments and membranes

Extrinsic ligaments connect the larynx to other structures. The thyrohyoid and hyoepiglottic ligaments connect with the hyoid bone above, and the cricotracheal ligament joins with the trachea below. Two paired intrinsic membranes connect the cartilaginous components within the larynx (Fig. 8.5). Superior & inferior thyroid cornua Superior & inferior thyroid cornua

Lipid breakdown lipolysis Fig 227

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

Lipid synthesis Fig 226

Fatty acids are an important fuel derived from the breakdown of stored fat. However, the liver also synthesizes fatty acids from nonlipid substances using acetyl-CoA as the primary substrate. Excess dietary glucose not required for glycogen synthesis is converted to pyruvate via glycolysis. The pyruvate is converted to acetyl-CoA and, instead of entering the TCA cycle to produce further ATP, the acetyl-CoA is used for fatty acid synthesis (lipogenesis). This involves irreversible conversion of...

Liver Blood Supply

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

Management

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

Maternal circulation

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

Membrane Stabilizers Disodium cromoglycate

This is a derivative of khellin, an Egyptian herbal remedy which was found to protect bronchi against allergens. It has no intrinsic bronchodilator effect. The main mechanism of action of disodium cromoglycate is the stabilization of the mast cell membrane, which in turn inhibits the release of mediators by allergens. It closes the calcium channels and thus prevents the entry of calcium ions, which trigger mast cell degranulation. Long-term treatment with this drug reduces hyperreactivity of...

Methylxanthines

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

Mitral stenosis

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

Monitoring during transfer

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

Muscle relaxation

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

Nonpharmacological analgesia Birth preparation classes

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

Other antiarrhythmics

Adenosine is an endogenous purine nucleoside which mediates a variety of natural cellular functions via membrane-bound receptors. Several adenosine receptor subtypes (A1-A4) have been identified. Myocardial Ax receptors activate potassium channels and decrease cAMP by activating inhibitory Gj-proteins A2 receptors mediate coronary vasodilatation by stimulating endothelial-derived relaxing factor and increasing intracellular cAMP. Increased potassium conductance induces membrane...

Pain Pathways In Labour And Caesarean Section

The afferent nerve supply of the uterus and cervix is via A8 and C fibres that accompany the thoracolumbar and sacral sympathetic outflows. The pain of the first stage of labour is referred to the spinal cord segments associated with the uterus and the cervix, namely T10, 11, 12 and LI. Pain of distension of the birth canal and perineum is conveyed via S2-S4 nerves (Fig. 52.1). When anaesthesia is required for caesarean section, all the layers between the skin and the uterus must be...

Parathyroid Hormones And Calcium Homeostasis

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

Peripheral factors

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

Pharmacokinetics

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

Pharmacology Mechanism of action

Benzodiazepines exert their actions by specific high-affinity binding to the benzodiazepine receptor, which is part of the y-aminobutyric acid (GABA) receptor complex. GABA is the major inhibitory neurotransmitter in the central nervous system (CNS), with most neurones undergoing GABAergic modulation. The benzodiazepine receptor is an integral binding site on the GABA receptor subtype. Binding of the agonist facilitates the entry of chloride ions into the cell, resulting in hyperpolarization of...

Phase Ii Induction Rapidsequence induction

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

Postoperative

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

Preanaesthetic assessment

Patients may present with a chronic arrhythmia for elective cardioversion or as an emergency in extremis with, a life-threatening arrhythmia. They may have other serious cardiovascular pathology such as rheumatic disease, ischaemic heart disease, recent myocardial infarction or cardiac failure. Digitalis therapy predisposes to post-cardioversion arrhythmias in some centres, it is withheld for 48 before cardioversion. If DC cardioversion is required in a patient receiving digoxin, the initial DC...

Prediction Of Specific Adverse Events The difficult airway

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

Premedication

In ischaemic heart disease and hypertension, premedication should be adequate to allay anxiety. A benzodiazepine such as temazepam is usually satisfactory. In patients with low or fixed cardiac output states (e.g. mitral or aortic stenosis, constrictive pericarditis) or congestive cardiac failure, premedication should be light, and in poor-risk patients it may be preferable to omit premedication altogether. The patient's usual cardiac medications should normally be continued and be included in...

Preoperative Assessment History

Symptoms of cardiovascular disease include dyspnoea, chest pain, palpitations, ankle swelling and intermittent claudication. Severity of symptoms assessed by a history of exercise tolerance is the most useful estimate of severity of cardiovascular disease. Past medical history and previous medical records can usually reveal the nature and severity of disease. Several factors relating to history, clinical examination and proposed surgery are associated with an increased risk of perioperative...

Preoperative management

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

Preoperative preparation

Medical treatment of the effects of the tumour must be achieved before surgery. a-Adrenergic antagonists are used commonly to counteract the increased peripheral vascular resistance and reduced circulating volume, and phenoxybenzamine (non-competitive, non-selective), prazosin and doxazosin (ai-selective, competitive antagonists) have been used successfully. Noncompetitive a-antagonists are preferable, as surges of catecholamine concentrations, occurring particularly during tumour...

Prevention and treatment

The incidence of postoperative vomiting may be reduced by careful selection of drugs in the perioperative period, and the prophylactic use of antiemetic agents (see Ch. 21). Table 41.9 Minor morbidity resulting from anaesthesia Nausea and vomiting Related to operation site Females > males Sore throat Discomfort from catheters, drains, nasogastric tubes Lip to 100 of those who receive succinylcholine Shivering Drowsiness Anorexia Disorientation Thrombophlebitis at injection site Hruised or cut...

Prevention of haemorrhage

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

Renal

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

Respiration

Control of respiration in newborn infants, especially premature neonates, is poorly developed. The incidence of central apnoea (defined as a cessation of respiration for 15 s or longer) is not uncommon in this group. The likelihood of this increases when the patient is given a drug with a sedative effect. Potentially life-threatening apnoea may occur. The incidence is reduced by postoperative administration of xanthine derivatives such as caffeine and theophylline which act as central...

Respiratory acidosis

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

Respiratory effects

Benzodiazepines produce dose-related central depression of ventilation. The ventilatory response to carbon dioxide is impaired and hypoxic ventilatory responses are markedly depressed. It follows that patients with hypoventilation syndromes and type 2 respiratory failure are particularly sensitive to the respiratory depressant effects of benzodiazepines. Ventilatory depression is exacerbated by airway obstruction and is more common in the elderly. Synergism occurs when both opioids and...