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Macewen, William (1847–1924). Eminent Scottish surgeon; Professor at Glasgow University, knighted in 1902. Advocated and practised tracheal intubation, usually oral, for laryngeal obstruction, e.g. due to diphtheria; he performed this by touch without anaesthetic. Was the first to advocate tracheal intubation instead of tracheotomy for head and neck surgery, in 1880. The tube was inserted before introduction of chloroform, and the patient allowed to breathe spontaneously. Packing around the tube achieved a seal.
Macintosh, Robert Reynolds (1897–1989). New Zealand-born anaesthetist, he became the first British Professor of Anaesthetics in Oxford in 1937. Lord Nuffield, a friend of Macintosh, had insisted that such a chair be set up as a precondition for endowing further chairs in Medicine, Surgery and Obstetrics and Gynaecology. Established Oxford as a centre for anaesthesia, and helped to establish anaesthesia as a medical specialty. Wrote books and articles about many aspects of local and general anaesthesia, and designed many pieces of equipment, including his laryngoscope, spray, endobronchial tube, vaporisers and devices for locating the epidural space. Also helped research the hazards of aviation and seafaring. Knighted in 1955, and received many other medals and awards.
McKesson, Elmer Isaac (1881–1935). US anaesthetist, practising in Toledo, Ohio. Founder and member of many US and international anaesthetic bodies. Also inventor and manufacturer of expiratory valves, pressure regulators, flowmeters, suction equipment, vaporisers and intermittent flow anaesthetic machines. A major proponent of the use of N2O in modern anaesthesia.
McMechan, Francis Hoeffer (1879–1939). US anaesthetist, practising in Cincinnati. A pioneer of the development of anaesthesia in the USA. Founded the American Association of Anesthetists in 1912, and instrumental in founding the National Anesthetic Research Society (subsequently the International Anesthesia Research Society) whose publication (which became Anesthesia and Analgesia) he edited.
Macrolides. Group of antibacterial drugs containing a lactam ring but distinct from β-lactams. Interfere with RNA-dependent protein synthesis. Includes erythromycin, azithromycin, clarithromycin and telithromycin. All have similar antibacterial activities (Gram-positive and some Gram-negative bacteria, mycoplasma, rickettsia and toxoplasma) but varying properties otherwise; thus the latter three drugs have longer durations of action than erythromycin and cause less nausea and vomiting.
Macrophage colony-stimulating factor, see Granulocyte colony-stimulating factor
Magill breathing system, see Anaesthetic breathing systems
Magill, Ivan Whiteside (1888–1986). Irish-born anaesthetist, responsible for much of the innovation in, and development of, modern anaesthesia. With Rowbotham in Sidcup after World War I, he developed endotracheal anaesthesia as an alternative to insufflation techniques, originally for facial plastic surgery. Introduced his own anaesthetic breathing system, forceps, laryngoscope and connectors, and developed blind nasal intubation. A pioneer of anaesthesia for thoracic surgery, he developed one-lung anaesthesia, endobronchial tubes and bronchial blockers. Also introduced bobbin flowmeters, portable anaesthetic apparatus and other equipment.
Co-founder of the Association of Anaesthetists of Great Britain and Ireland, he also helped establish the DA examination, the Faculty of Anaesthetists and the FFARCS examination. Worked at the Westminster and Brompton Hospitals, London. Knighted in 1960, and received many other medals and awards.
Magnesium. Largely intracellular ion, present mainly in bone (over 50%) and skeletal muscle (20%); the remainder is found in the heart, liver and other organs. 1% is in the ECF. Normal plasma levels: 0.75–1.05 mmol/l (although the value of measurement has been questioned, since most magnesium is intracellular). Deficiency is common in critical illness. Required for protein and nucleic acid synthesis, regulation of intracellular calcium and potassium, and many enzymatic reactions, including all those involving ATP synthesis/hydrolysis. Inhibits voltage-gated calcium channels, acting as a physiological antagonist; also an antagonist at NMDA receptors.
Herroeder S, Schonnher ME, De Hert SG, Hollman MW (2011). Anesthesiology; 114: 971–93
Magnesium sulphate. Drug with varied clinical indications, reflecting its numerous sites of action, e.g. non-competitive inhibition of phospholipase C-mediated calcium release; antagonism of NMDA receptors; inhibition of voltage-gated calcium channels and sodium/potassium pumps; and attenuation of catecholamine release from the adrenal glands. Its actions thus include neuronal/myocardial membrane stabilisation and bronchial and vascular smooth muscle relaxation. Magnesium chloride is also used.
as an anticonvulsant drug in pre-eclampsia and eclampsia. Thought to act by reducing cerebral vasospasm seen in the condition. Also causes systemic vasodilatation, helping to lower BP. Superior to diazepam and phenytoin in preventing primary eclampsia, as well as preventing recurrence of seizures.
severe asthma resistant to conventional bronchodilator therapy.
perioperative management of phaeochromocytoma.
cardiac arrhythmias (e.g torsade de pointes), especially those caused by hypokalaemia.
• Dosage: 2–4 g (8–16 mmol) iv over 5–15 min, followed by 1–2 g/h.
cardiac conduction defects, drowsiness, reduced tendon reflexes, muscle weakness, hypoventilation and cardiac arrest may occur with increasing hypermagnesaemia.
Overdosage may be treated with iv calcium.
Herroeder S, Schonnher ME, De Hert SG, Hollman MW (2011). Anesthesiology; 114: 971–93
Magnesium trisilicate. Particulate antacid, used in dyspepsia. Has been used to increase gastric pH preoperatively in patients at risk from aspiration of gastric contents, but may itself cause pneumonitis if inhaled. Has also been used to reduce risk of peptic ulceration on ICU, e.g. by hourly nasogastric administration to keep pH above 3–4.
Magnetic resonance imaging (MRI; Nuclear magnetic resonance, NMR). Imaging technique, particularly useful for investigating CNS, pelvic and musculoskeletal pathology, where tissue movement is minimal. By using gating techniques it can also be used in other parts of the body, including the chest; accurate measurements of the heart’s dimensions and movement have been obtained.
Involves placement of the patient within a powerful magnetic field, causing alignment of atoms with an odd number of protons or neutrons, e.g. hydrogen. Radiofrequency pulses are then applied, causing deflection of the atoms with absorption of energy. When each pulse stops, the atoms return to their aligned position, emitting energy as radiofrequency waves. Computer analysis of the emitted waves provides information about the chemical make-up of the tissue studied. MRI can provide graphic tissue slices in any plane, or may be used to analyse metabolic processes, e.g. distribution and alterations of intracellular phosphate (spectroscopy). So-called functional MRI (fMRI) techniques demonstrate regional differences in tissue oxygenation and cerebral blood flow. Interventional MRI involves surgery within the MRI suite to allow scanning during operative procedures.
• Problems and anaesthetic considerations:
sedation/anaesthesia may be required, especially in children or nervous adults, since the subject has to lie within a very small space and the scans are accompanied by loud knocking noises. Problems include those of radiology in general, in addition to the above. Scans originally took up to 2–3 h but are shorter with newer machines.
Malaria. Tropical disease caused by the protozoan plasmodium (P. vivax, P. ovale or P. falciparum), and spread by the anopheles mosquito, which carries infected blood between individuals. Although not endemic in the UK, individual cases occur not uncommonly because of widespread air travel. Usual presentation is within 4 weeks of travel from an infected area, although onset may be delayed by many months. In milder forms, periodic release of the organism from the liver and reticuloendothelial system into the bloodstream causes relapsing fever, rigors and malaise (typically cycles of pyrexia lasting 3 days [tertian] or 4 days [quartan], or having no pattern [subtertian], depending on the infecting organism).
rigors, fever, vomiting, headache.
confusion, convulsions, coma. 80% of deaths result from cerebral malaria.
hypoglycaemia; thought to be caused by increased insulin secretion; it may also result from quinine therapy.
bronchopneumonia, acute lung injury, pulmonary oedema.
diarrhoea, endotoxaemia from bowel bacteria.
anaemia, thrombocytopenia, intravascular haemolysis, DIC. Diagnosis is made by examining blood films, or rarely, bone marrow, for parasites.
use of insect repellents, mosquito nets over beds, etc.
drug prophylaxis, e.g. mefloquine, doxycycline or malarone.
vaccination: a vaccine has been developed that can halve the infection rate.
chloroquine and primaquine for mild infections.
quinine; usually reserved for resistant organisms or severe falciparum infection.
Malaria may be transmitted by blood transfusion; those with known infection or recent travel to an endemic area are therefore excluded from being donors.
Greenwood BM, Bojang K, Whitty CJM, Targett GAT (2005). Lancet; 365: 1487–98
– primary:
– local, e.g. pressure effects, ulceration, haemorrhage.
– systemic, e.g. anaemia, cachexia, susceptibility to infection, electrolyte disturbances (e.g. hypercalcaemia), endocrine effects (e.g. Cushing’s syndrome caused by bronchial carcinoma, carcinoid syndrome, myasthenic syndrome).
– metastatic, e.g. lung, liver, bone.
effects of previous treatment:
– surgery/radiotherapy, e.g. scarring, deformities.
– cytotoxic drugs, corticosteroids, opioid analgesic drugs and antidepressant drugs.
possible effects of anaesthesia on the immune system and cancer, e.g. administration of blood during bowel cancer resection may decrease survival.
Malignant hyperthermia (MH). Condition first described by Denborough in 1961, consisting of increased temperature and rigidity during anaesthesia. Incidence is reported between 1:5000 and 1:200 000. Results from abnormal skeletal muscle contraction and increased metabolism affecting muscle and other tissues. Susceptibility shows autosomal dominant inheritance; in 50–70% of affected families the predisposing genetic loci are found on the long arm of chromosome 19, coding for the ryanodine/dihydropyridine receptor complex at the T-tubule/sarcoplasmic reticulum complex of striated muscle. This receptor regulates calcium flux in and out of the sarcoplasmic reticulum; this control is lost in MH, resulting in a massive influx of calcium leading to uncontrolled muscle contraction. MH susceptibility is also genetically related to central core disease, a rare muscular dystrophy. Several other gene mutations have been implicated, thus reducing the sensitivity of genetic analysis as a test for MH.
MH follows exposure to triggering agents, particularly the volatile anaesthetic agents and suxamethonium, although it is thought that a single dose of the latter by itself will not cause the syndrome. It may occur in patients who have had previously uneventful anaesthetics. MH may also be triggered by stress and strenuous exercise. Thus patients’ sensitivity to triggering agents may vary at different times. Reactions have been reported up to 11 h postoperatively.
• Features are related to muscle abnormality and hypermetabolism, but not all may be present:
sustained muscle contraction; results from breakage of the normal impulse/contraction sequence (excitation/contraction uncoupling) relating to abnormal calcium ion mobilisation, and is unrelieved by neuromuscular blocking drugs. Masseter spasm may be an early sign.
muscle breakdown with release of potassium, myoglobin and muscle enzymes, e.g. creatine kinase. Hyperkalaemia may cause cardiac arrhythmias.
increased O2 consumption, leading to cyanosis.
increased CO2 production and hypercapnia. Hyperventilation may occur in the spontaneously breathing patient.
rapidly increasing body temperature (e.g. > 0.5°C every 10 min) and sweating.
dantrolene is the only available specific treatment. 1 mg/kg is given iv, repeated as required up to 10 mg/kg.
– hyperventilation with 100% O2. Anaesthesia is maintained with TIVA.
– correction of acidosis with bicarbonate, according to the results of blood gas interpretation.
– cooling with cold iv fluids, fans, sponging and irrigation of body cavities. Other causes of hyperthermia should be considered.
– treatment of hyperkalaemia if severe.
– diuretic therapy (mannitol or furosemide) and urinary alkalinisation to reduce renal damage caused by myoglobin.
– treatment of any arrhythmias as they occur.
– corticosteroids (e.g. dexamethasone 4 mg) have been advocated.
– close monitoring in an ICU for 36–48 h postoperatively. Creatine kinase levels should be measured 12-hourly for 36–48 h, and the urine analysed for myoglobin.
– acute kidney injury and DIC are treated as necessary.
Treatment with dantrolene should be instituted as soon as the diagnosis is suspected. Arterial blood gas interpretation and measurement of plasma potassium should be performed early to detect acidosis and hyperkalaemia.
serum creatine kinase elevation and myoglobinuria are suggestive, but not diagnostic. The former is not reliable as a screening test. Creatine kinase and myoglobin may both increase after suxamethonium administration in normal patients.
muscle biopsy may appear normal histologically.
pretreatment with oral dantrolene is now thought to be unnecessary.
sedative premedication is sometimes given to reduce ‘stress’, but this is controversial.
avoidance of known triggering agents: volatile agents and suxamethonium. N2O is considered safe. Many other drugs have been implicated at some time, but the above are the only definite triggers. TIVA is a useful technique. Local anaesthetic techniques may be used, but MH may still occur. All local anaesthetic agents are considered as safe as each other. Some would avoid phenothiazines and butyrophenones because of the neuroleptic malignant syndrome, but there is no evidence that the two conditions are related.
dantrolene and supportive treatments should be readily available.
Mallampati score, see Intubation, difficult
Malnutrition. Nutrient deficiency, usually of several dietary components. Protein depletion with near-normal energy supply may lead to kwashiorkor, with hypoproteinaemia and oedema. Protein and energy depletion may lead to marasmus, with normal plasma protein concentration.
• Body reserves during total starvation under basal conditions:
carbohydrate: about 0.5 kg, mainly as liver and muscle glycogen; lasts < 1 day.
protein: 4–6 kg, mainly as muscle; lasts 10–12 days.
fat: 12–15 kg, as adipose tissue; lasts 20–25 days.
Protein breakdown is reduced by even small amounts of glucose, possibly via resultant insulin secretion, inhibiting protein catabolism.
• Malnutrition is common to some degree in hospital patients. It may be associated with:
decreased intake, e.g. vomiting, malabsorption, anorexia, poor diet, nil-by-mouth orders.
decreased utilisation, e.g. renal failure.
increased basal metabolic rate, e.g. trauma, burns, severe illness, pyrexia.
Thus common perioperatively, especially in severe chronic illness, GIT disease/surgery, alcoholics, the elderly and the mentally ill. May result in impaired wound healing, bedsores, increased susceptibility to infection, weakness, anaemia, hypoproteinaemia, electrolyte disturbances and dehydration, vitamin deficiency disorders and predisposition to hypothermia. Respiratory muscle weakness may predispose to respiratory complications.
Long-term nutrition, via enteral or parenteral routes, is thought to be beneficial preoperatively (at least 14 days). The place of short-term feeding is less certain. Progress may be monitored by weight or skin thickness measurements.
Managing Obstetric Emergencies and Trauma course (MOET course). Training programme, devised in 1998, designed for medical staff working within obstetrics, obstetric anaesthesia, and accident and emergency medicine. Similar to other acute life support courses in its systematic approach and structure.
Mandatory minute ventilation (MMV). Ventilatory mode used to assist weaning from ventilators. The required mandatory minute ventilation is preset, and the patient allowed to breathe spontaneously, with the ventilator making up any shortfall in minute volume. Thus with the patient breathing adequately, the ventilator is not required. However, a minute ventilation made up of rapid shallow breaths will also ‘satisfy’ the ventilator, despite alveolar ventilation being inadequate. In addition, not all ventilators allow spontaneous minute ventilation to exceed the preset one (extended mandatory minute ventilation; EMMV). Thus MMV is less popular than IMV.
Mandibular nerve blocks. Performed for facial and intraoral procedures.
• Anatomy: the mandibular division (V3) of the trigeminal nerve passes from the Gasserian ganglion through the foramen ovale.
motor nerves to the muscles of mastication and tensor muscles of the palate and eardrum.
sensory nerves (see Fig. 76; Gasserian ganglion block):
– meningeal branch: passes through the foramen spinosum and supplies the adjacent dura.
– buccal nerve: supplies the skin and mucosa of the cheek.
– auriculotemporal nerve; supplies the anterior eardrum, ear canal, temporomandibular joint, cheek, temple, temporal scalp and parotid gland.
– lingual nerve: passes alongside the tongue to supply its anterior two-thirds, the floor of the mouth and lingual gum.
• Blocks:
mandibular: a needle is inserted at right angles to the skin between the coronoid and condylar processes, just above the bone. After contacting the pterygoid plate, it is redirected posteriorly until paraesthesiae are obtained, and 5 ml local anaesthetic agent injected (N.B. the pharynx lies 5 mm internally).
1–2% lidocaine or prilocaine with adrenaline is most commonly used. Systemic absorption of adrenaline may cause symptoms, especially if high concentrations are used, e.g. 1:80 000. Immediate collapse following dental nerve blocks is thought to result from retrograde flow of solution via branches of the external carotid artery, reaching the internal carotid; perineural spread to the medulla has also been suggested.
See also, Gasserian ganglion block; Maxillary nerve blocks; Nose; Ophthalmic nerve blocks
Mandragora (Mandrake). Plant, supposedly human-shaped, thought to hold magic powers, including the ability to induce sleep and relieve pain. Contains hyoscine and similar alkaloids. According to legend, its scream on uprooting killed all who heard it, hence the supposedly ‘safe’ method of collection: a dog is tied to the plant at midnight, whilst its owner retreats to a safe distance with ears stopped with wax. The dog is enticed to run after food, pulling out the mandrake and dying in the process.
Mannitol. Plant-derived alcohol. An osmotic diuretic; it draws water from the extracellular and intracellular spaces into the vascular compartment, expanding the latter transiently. Not reabsorbed once filtered in the kidneys, it continues to be osmotically active in the urine, causing diuresis. Used mainly to reduce the risk of perioperative renal failure (e.g. during vascular surgery, surgery in obstructive jaundice) and to treat cerebral oedema. Efficacy in the latter depends on integrity of the blood–brain barrier that may be altered in neurological disease, although some benefit is derived from the systemic dehydration produced. Has also been used to lower intraocular pressure. It may also act as a free radical scavenger. Oral mannitol has been used (together with activated charcoal) as an osmotic agent to increase intestinal removal of poisons.
Temporarily increases cerebral blood flow; ICP may rise slightly before falling, especially after rapid injection. Excessive brain shrinkage in the elderly may rupture fragile subdural veins. A rebound increase in ICP may occur if treatment is prolonged, due to eventual passage of mannitol into cerebral cells; the effect is small after a single dose. A transient increase in vascular volume and CVP may cause cardiac failure in susceptible patients.
• Dosage: 0.25–2 g/kg by iv infusion of 10–20% solution over 20–30 min. Effects occur within 30 min, lasting 6 h. 0.25–0.5 g/kg may follow 6-hourly for 24 h, unless diuresis has not occurred, cardiovascular instability ensues or plasma osmolality exceeds 315 mosmol/kg.
Available as 10% and 20% solutions with osmolality 550 and 1100 mosmol/kg respectively.
Mann–Whitney rank sum test, see Statistical tests
Manslaughter. Unlawful killing of another person; a criminal charge (as opposed to the civil charge of negligence
