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...

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...

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...

Airwaybreathing

The first priority for the anaesthetist when confronted with an unconscious trauma victim is to establish the patency of the patient's airway whilst assuring immobilization of the cervical spine. If upper airway obstruction is present, the pharynx is cleared of any debris and the jaw displaced forward (jaw thrust). Neck tilt and chin lift are avoided as these manoeuvres could displace an unstable cervical spine. Early establishment of a patent airway is paramount to successful resuscitation and...

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 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 Thoracolumbar Decompressive Surgery

In most instances, patients are placed in the prone position, either supported on chest and iliac crest blocks or in the 'jack-knife' position. A technique employing IPPV is essential because these procedures often take a long time. However, because raised ICP is not a problem, it is often sufficient to ventilate the lungs with a volatile anaesthetic agent unless this causes a decrease in systemic arterial pressure. A balanced anaesthetic technique is normally quite satisfactory, with 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...

Arterial Bleeding

Incised arterial vessels do not vasoconstrict readily therefore the normal haemostatic responses are incapable of controlling bleeding. The flow from damaged arterioles is related to the size of the vessels and the intraluminal pressure reductions in vascular resistance or cardiac output (or both) reduce arterial pressure. Elevation of the cut end of the artery above the aortic root leads to a decrease in blood flow from the vessel. Arterial pressure decreases by approximately 1 mmHg for every...

Ascending Tracts And Supraspinal Systems

Most dorsal horn neurones project to higher centres in the brain by ascending several segments in the spinal cord before crossing over to the opposite ventrolateral side. They then join one of three major spinal systems Spinothalamic tract - probably the most important for pain transmission, this tract projects to several nuclei in the thalamus. The spinothalamic tract is the target for treating intractable cancer pain by cordotomy. Spinoreticular tract - terminates in the reticular nuclei in...

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...

Balanced Multimodal Analgesia

The concept of balanced analgesia is analogous to that of balanced anaesthesia. It is possible to block the development of pain by the use of a combination of different drugs acting at different sites peripherally, on somatic and sympathetic nerves, at spinal cord level, and centrally. The benefit of this technique is that not only may superior analgesia be achieved by a combination of drugs but their individual doses may be reduced, thereby decreasing the incidence of side-effects. For...

Benzodiazepines

Although not endogenous substances, these drugs act at specific synapses in the CNS (including the spinal cord) at which GABA is the transmitter. Benzodiazepines selectively facilitate GABA action at synapses. Aminophylline may reverse diazepam sedation by its adenosine-blocking effect at GABA receptors. Adenosine is as potent a CNS-depressant mediator as GABA, and may have an amplifying effect on the GABA-receptor complex. Flumazenil is a benzodiazepine antagonist. Benzodiazepines exert their...

Cardiac catheterization

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

Cardiac glycosides

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

Cardiopulmonary resuscitation

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

Cardiovascular effects

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

Cardiovascular System

The process of growth demands a high metabolic rate. It should therefore come as no surprise that infants and children have a Table 53.1 Lung mechanics of the neonate compared Table 53.2 Respiratory variables in the neonate Table 53.2 Respiratory variables in the neonate Dead space ( J j) ( Vt) x 0.3 ml Respirator)'rate 32 breaths min-1 higher cardiac index (compared with the adult) so that oxygen and nutrients can be delivered to actively growing tissues. The ventricles of neonates and infants...

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...

Central Venous Pressure

The pressure in the superior vena cava is usually measured to guide fluid replacement in situations such as major blood loss or where Table 38,3 Advantages of direct arterial pressure Beat-by-beat observation of changes where blood pressure is variable or where vasoactive drugs are used Ability to obtain frequent blood samples myocardial function is impaired. In normal individuals, the central venous pressure (CVP) is 0-5 cmE O. It is reduced in hypo-volaemia and increased by heart failure,...

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...

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...

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...

Complications Acute

Significant hypotension should be anticipated with SAB. Changes in position, e.g. turning the patient from the supine to the prone position, may result in a sudden increase in the height of block, with consequent extension of sympathetic blockade. This may occur even after 15-20 min. Treatment (Table 43.3) may not be necessary moderate hypotension may help to reduce operative blood loss and is tolerated well by most patients. Severe or unwanted hypotension may be treated by i.v....

Complications Intraoperative

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

Conduct of anaesthesia

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,...

Cse

There are various techniques for this, although the 'needle through needle' technique described above is probably the most popular. A full description of the other techniques is outside the remit of this chapter. The CSE allows increased flexibility by combining an epidural and a spinal. The spinal anaesthetic is a singleshot technique and while most of the time this is no problem, delay in starting surgery, a difficult, long operation or failure of the block may occur. The epidural may not...

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...

Descending Systems

Injuries sustained during sporting events or even on the battlefield are often reported as being relatively painless, at least until the individual has completed the sporting event, or reached the safety of a first aid unit in the field. In these circumstances, attention on survival or winning exerts a powerful effect on pain intensity. This is a result of influence of the descending inhibitory pathways from the brain to the spinal cord and is referred to as 'central control' in the gate...

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...

Dosage and administration

Flumazenil is usually administered intravenously. An initial dose of 0.2 mg is appropriate in adults. Additional doses of 0.1 mg can be given every 15 min. The maximum recommended dose is 1.0 mg, although massive doses of up to 100 mg have been administered safely. The effect of each dose is short-lived (15-45 min) and Table 10.1 Adverse effects of doxapram unpredictable. The half-life is shorter than those of the benzodiazepine agonists, and sedation and depression of ventilation may recur,...

Drug interactions

Interactions with other drugs do occur, although they rarely cause clinical problems. Therapy with anticholinesterases for myasthenia, or the concomitant administration of other drugs hydrolysed by plasma cholinesterase, increases the toxicity of the ester drugs, and competition for plasma protein binding sites may occur with the amides. Of more practical importance is that heavy sedation with anticonvulsants (e.g. benzodiazepines) may mask the early signs of toxicity. These drugs may even...

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...

Elective Caesarean Section

Regional anaesthesia is the technique of choice for elective caesarean section. Although most women presenting for elective caesarean section expect to be awake for the delivery of their baby, they still need careful preoperative explanation of the procedure with explanation of the risks. As many hospitals admit women on the day of surgery, it may be difficult to give sufficient time to the preoperative visit, and therefore it is advisable to have an information sheet for the woman before...

Erythropoietin

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

Factors affecting 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

Fetal Monitoring

Recent developments have made it possible to assess fetal well-being in the antenatal period. An obstetric anaesthetist is often involved when a decision to deliver the baby early is made on the outcome of these assessments. The most commonly used tests are Indication for induction or augmentation Onset of second Effect of drug Patient's general condition

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

The metabolites (metabolized by MAO and COMT) of endogenous catecholamines are excreted in the urine as 3-methoxy-4-hydroxymandelic acid, metanephrine (from epinephrine) and normetanephrine (from norepinephrine). MAO monoamine oxidase COMT catechol-o-methyl transferase. thetic nerves and in the adrenal gland. Stimulation of presynaptic DA2 receptors inhibits dopamine release by negative feedback. Postganglionic sympathetic fibres supplying sweat glands and arterioles in some areas of skin and...

Flumazenil

Flumazenil is a very high-affinity competitive antagonist for all other ligands at the benzodiazepine receptor. It rapidly reverses all the CNS effects of benzodiazepines and also the other potentially dangerous adverse physiological effects, including respiratory and cardiovascular depression and airway obstruction. Flumazenil has only very slight intrinsic activity at high dose and is very well tolerated, with minimal adverse effects. Flumazenil is rapidly cleared from plasma and metabolized...

Gastric Emptying

The circular, longitudinal and oblique arrangement of muscle in the stomach wall is more complex than in other parts of the GI tract. Three types of motility patterns can be detected in the stomach receptive relaxation and contraction, peristaltic propulsion and mixing, and the migrating motor complex. During feeding, smooth muscle in the wall of the proximal stomach relaxes to accommodate the food with little increase in intragastric pressure (receptive relaxation). This is followed by...

Gate Theory Of Pain

Up until the 1960s, pain was considered to arise from peripheral nerves and reach the brain cortex via a direct route with no modulation on the way. It was clear to many workers that this theory did not explain many clinical cases such as phantom pain, hyperalgesia and allodynia, and the effect of past experience. The gate theory of pain, proposed by Ronald Melzack and Patrick Wall in 1965, was a major shift in thinking about pain mechanisms, and forms the basis of our current understanding....

General principles of pharmacology and pharmacokinetics

Printable Radius Template Machining

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...

Histamine release and pruritus

Morphine releases histamine from mast cells, unrelated to the action on opioid receptors. It is related to speed of injection and concentration. Local effects include urticaria and itching and systemic effects include bronchoconstriction and hypotension. Pethidine and other phenylpiperidino opioids are unlikely to produce this effect. Pruritus after spinal administration is caused by all p opioid agonists and may usually be reversed by naloxone. It occurs most often after intrathecal opioids...

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...

Hydroxytryptamine 5HT serotonin

This has been isolated from the brain stem, many forebrain sites and the dorsal horns of the spinal cord. It may represent one of the descending control pathways which modulate sensitivity of the spinal cord to pain input from the periphery, and therefore plays a key role in mediating analgesic actions of morphine and related opioid analgesics. In the forebrain, this system may be responsible for control of sleep and waking, central temperature regulation and control of aggressive behaviour.

Hypothalamic And Pituitary Function

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

Inguinal Hernia Repair

This is one of the commonest operations in the neonatal period. The incidence in this age group is highest amongst preterm infants. General anaesthesia is avoided preferably because of the risk of postoperative apnoea. The choice is between spinal and caudal epidural anaesthesia. Spinal anaesthesia offers the advantage of a quick onset with profound muscle relaxation in less than 2 min. Unfortunately the duration of action is very short - of the order of about 40 min. Addition of cq-agonists...

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...

Intravenous Sedation

The aim of this technique is to have a patient who is feeling no anxiety, who is cooperative though drowsy, yet who is easily reusable. The procedure starts with intravenous cannulation and attachment of a pulse oximeter. Increments of benzodiazepine, usually midazolam, are given, and the amount titrated to the patient's response. Midazolam has largely replaced diazepam as the benzodiazepine used for these procedures as it has the advantage of a shorter half-life and no active metabolites. This...

Ischaemia Of The Central Nervous System

Ischaemic injury to the central nervous system varies from minimal, focal dysfunction to stroke or death. The mechanism is related usually to hypoxaemia and or hypotension. The risk of ischaemic brain damage related to hypotension is increased if the patient has been positioned head-up during surgery. Rarely, intracerebral haemorrhage occurs during anaesthesia. Although the risk is increased if blood pressure has been very high, there have been reports of intracerebral haemorrhage during...

Laryngoscope handle

The standard handle may result in difficult laryngoscopy in obese patients, and in women with large breasts. Short handles are available for the use in these situations (Fig. 32.48). The short handle has almost replaced the use of the Polio blade (Fig. 32.49) in obstetric practice. The McCoy laryngoscope (Fig. 32.50A) is based on the standard Macintosh blade but has a hinged tip. This is operated by a lever mechanism attached to the handle. When the lever is pressed (Fig. 32.50B), the tip of...

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

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...

Management Of The Headinjured Patient

Head injuries and their subsequent treatment and rehabilitation represent a considerable proportion of neurosurgical practice. The immediate management must involve meticulous attention to the prevention of any secondary brain injury little can be done about the primary insult to the brain or spinal cord. In recent years, the awareness of both the medical profession and the general public has had a profound effect on general resuscitation simply by improving airway management in the unconscious...

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...

Mechanism of action

012-Adrenergic receptors are involved in the regulation of the release of the neurotransmitter norepinephrine. These receptors were initially classified anatomically as presynaptic, but 012-adrenoceptors are also found postsynaptically and extrasynapti-cally. The more correct pharmacological classification is based on the predominantly aj -selectivity of the antagonist yohimbine. CX2-Adrenoceptors are located peripherally and centrally, with the centrally mediated effects of particular...

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...

Method

Caudal blockade may be performed with the patient in the prone position, but the left lateral position is usually more acceptable to the patient. Palpation down the sacral spine leads to the depression of the sacral hiatus at S5, flanked by the sacral cornua, through which the needle is inserted. A 21-gauge hypodermic needle is introduced through skin and sacrococcygeal ligament in a cephalad direction at 45 to the skin (Fig. 43.7). When the membrane is penetrated, the needle hub is depressed...

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...

Minimum alveolar concentration MAC

MAC is the minimum alveolar concentration of an inhaled anaesthetic agent which prevents reflex movement in response to surgical incision in 50 of subjects. MAC values of commonly used inhalation agents are shown in Appendix II (p. 766). MAC varies little with metabolic factors but is reduced by opioid premedication and in the presence of hypothermia. MAC is higher in neonates and is reduced in the elderly (see Ch. 13). The effects of inhalation anaesthetics are additive thus 1 MAC-equivalent...

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...

Modalities of cutaneous sensation

There are four main modes of cutaneous sensation touch, cold, warmth and pain. Pain registered by stimulation of the skin has a pricking, itching quality and is well-localized. The pain threshold may be increased by one-third by distracting the subject's attention and reduced by half in sunburned skin. The first sensation of pain arises abruptly and is carried by moderately large fibres, conducting impulses at 10 ms1. The second sensation is slower and of a burning nature, probably being...

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 function and neuromuscular blockade

In the last 60 years, neuromuscular blocking drugs have become an established part of anaesthetic practice. They were first administered in 1942, when Griffith and Johnson in Montreal used Intocostrin, a biologically standardized mixture of the alkaloids of the plant Chondrodendron tomentosum, to facilitate relaxation during cyclopropane anaesthesia. Previously, only inhalation agents (nitrous oxide, ether, cyclopropane and chloroform) had been used during general anaesthesia, making surgical...

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...

Muscles

Extrinsic muscles connect the larynx to neighbouring structures and include the thyrohyoid and sternothyroid muscles (which elevate and depress the larynx, respectively, and are supplied by the hypoglossal nerve) and the inferior constrictor muscle of the pharynx (no action on the larynx, see above). Other muscles act on the larynx through their attachments to associated structures. These include the indirect elevators - the mylohyoid, stylohyoid and geniohyoid muscles - and the indirect...