R
R on T phenomenon. Arises when the R wave of a ventricular ectopic beat falls on the T wave of the preceding beat. At the middle of the T wave, the myocardium is partly depolarised and partly repolarised, and thus vulnerable to establishment of re-entrant and circulatory conduction, leading to VF or VT.
R wave. First upward deflection of the QRS complex of the ECG (see Fig. 59b; Electrocardiography). Tends to increase in size from V1 to V6, with an accompanying reduction in size of S wave across these leads. Loss of this ‘R wave progression’, with a sudden increase in R wave size in V5 or V6, may indicate old anterior MI. In V1–6, at least one normally exceeds 8 mm, but none exceeds 27 mm.
Rabeprazole sodium. Proton pump inhibitor; actions and effects are similar to those of omeprazole.
Rabies. Infection caused by a lyssavirus of the rhabdovirus family, eradicated from Britain in 1902; however, occasional cases thought to have originated outside the UK have occurred in animals, e.g. dogs and bats. Fewer than 5 cases occur annually in Europe and the USA. Spread mainly via domestic dogs and cats, but also by foxes, bats and other wildlife. Transmitted via infected saliva penetrating broken skin or intact mucosa; the virus replicates in local muscle then migrates proximally along peripheral nerves to dorsal root ganglia and the CNS, eventually causing lethal encephalitis. Incubation period is usually 20–90 days in humans, but may be 4 days to several years.
Radford nomogram. Diagram showing the relationship between tidal volume, patient’s weight and respiratory frequency. Used to aid appropriate selection of ventilator settings for children and adults. Now rarely used.
Radial artery. Terminal branch of the brachial artery. Arises in the antecubital fossa, level with the radial neck, and runs distally on the tendons and muscles attached to the radius (biceps tendon, supinator, pronator teres, flexor digitorum superficialis, flexor pollicis longus, pronator quadratus). Lies deep to brachioradialis muscle in the upper forearm, but subcutaneous in the lower forearm and easily palpable, especially over the distal quarter of the radius. Runs deep to abductor pollicis longus and extensor pollicis brevis tendons at the radial styloid, entering the anatomical snuffbox. Then enters the palm between the first and second metacarpals, forming the deep palmar arch. Branches include a superficial palmar branch (enters the palm superficial to the flexor retinaculum), which supplies the muscles of the thenar eminence before anastomosing with the superficial palmar arch. At the wrist, it is a common site for palpation of the pulse and for arterial cannulation.
Radial nerve (C5–T1). Terminal branch of the posterior cord of the brachial plexus. Descends in the posterior upper arm, passing laterally behind the middle of the humerus in the radial groove. Crosses the antecubital fossa anterior to the elbow joint, between brachialis and brachioradialis. Descends under brachioradialis lateral to the radial artery in the forearm, passing posteriorly proximal to the wrist to end on the dorsum of the hand as digital branches.
axillary: to deltoid, teres minor and skin of the posteromedial upper arm.
– to triceps, brachioradialis and extensor carpi radialis longus.
See also, Brachial plexus block; Elbow, nerve blocks; Wrist, nerve blocks
Radiation. Emission of energy in the form of waves or particles. Includes emission of electromagnetic waves (e.g. light), most of which is non-ionising (does not have sufficient energy to overcome electron binding energy). Ionising radiation may result in displacement of electrons in organic material with the potential for tissue damage, and includes:
γ-rays and X-rays: electromagnetic waves emitted from (γ-rays) or outside (X-rays) the nuclei of excited atoms. Have extremely high penetration of matter and thus pose a health hazard requiring radiation safety precautions. γ-Rays are used in radiotherapy and imaging, and X-rays in imaging.
Exposure to ionising radiation is kept to a minimum with appropriate storage and handling of radioisotopes, minimal use of X-rays and appropriate use of shielding. Formal training is required for those performing or directing radiology procedures.
Radiography in intensive care. Increasingly used as the range and quality of techniques and equipment available increase. Consultation with radiologists aids the proper selection and interpretation of many imaging techniques. In most cases, the use of mobile equipment results in less than optimal results but may be acceptable given the difficulty of transporting critically ill patients from the ICU; subtle changes between sequential films may be misleading if this is not taken into account. Investigations include CXR, ultrasound and CT and MRI scanning; bedside CT scanners are now available but MRI requires transport to the imaging department. Radioisotope scanning usually requires transfer from the ICU.
Practical considerations include the requirement for sedation and adequate monitoring during transport or the procedure itself, the interference of the procedure with background therapy including the requirement for moving the patient (e.g. to place films underneath), and the potentially adverse effects of radiological contrast media.
Radioisotope scanning. Use of radioisotopes to label certain parts of the body in order to investigate organ function, either directly or attached to circulating cells. Includes the following:
assessment of blood flow: cerebral blood flow, renal blood flow, lung perfusion scans (e.g. combined with ventilation scans in suspected PE).
localisation of lesions: PE, bone metastases/infection/fracture, intra-abdominal sepsis.
The radiation contained within the body after scanning is negligible, posing no risk to staff.
Radioisotopes. Isotopes of elements that undergo disintegration; i.e. the nucleus emits α, β or γ radiation either spontaneously or following a collision. Used clinically as labels to determine fluid compartments, blood flow, pulmonary 
distribution and sites of infection. Technetium-99 m and xenon-133 are often suitable because they are easy to use and their half-lives are short. Also used to label metabolically active substances which are taken up by certain tissues, allowing imaging of the tissue concerned, e.g. fibrinogen labelled with iodine-123 accumulates in a clot and may be used to detect DVT. Therapeutic use includes radiotherapy.
Radiological contrast media. Contain large molecules that absorb X-rays (e.g. barium [enteral] or iodine [enteral or iv]) or have paramagnetic properties (e.g. gadolinium) for MRI scanning. Adverse reactions may follow iv injection:
related to high osmolality (up to 7× that of plasma):
– initial hypervolaemia followed by osmotic diuresis and hypovolaemia.
– damage to red blood cells and vascular endothelium.
– reactions range from mild symptoms to cardiovascular collapse and death.
– adverse reactions are most likely to be due to direct histamine release or complement activation. ‘True’ anaphylaxis is not thought to occur.
direct toxicity: myocardial depression and systemic vasodilatation.
Thus initial hypertension may be followed by prolonged hypotension. Renal failure may result from cardiovascular changes plus direct toxicity.
Incidence of reactions and renal failure is decreased by using low osmolar, non-ionic media. Other measures to prevent renal injury include adequate hydration and administration of N-acetylcysteine. Resuscitation equipment and drugs must always be available.
Radiology, anaesthesia for. Most radiological procedures require neither general anaesthesia nor sedation. Anaesthesia may be required for the very young, confused or agitated patients and those with movement disorders. Procedures include CT scanning, MRI, angiography and invasive procedures, e.g. embolisation of vascular lesions in neuroradiology.
• Main anaesthetic considerations:
remote location, often cramped conditions, with poor lighting.
old or incomplete anaesthetic/monitoring equipment.
Preoperative assessment and preparation should be as for any anaesthetic procedure.
Radiotherapy. Use of ionising radiation to treat neoplasms. May involve:
implantation of internal sources (brachytherapy), e.g. in gynaecological or CNS tumours.
administration of radioactive radioisotopes, e.g. iodine-131 in hyperthyroidism, phosphorus-32 in polycythaemia.
general condition of the patient: features of malignancy, site and nature of the neoplasm and drug therapy. Haematological abnormalities are common.
Techniques used include sedation or general anaesthesia using TIVA with propofol, or intermittent boluses of ketamine (especially in children).
McFadyen JG, Pelly N, Orr RJ (2011). Curr Opin Anaesthesiol; 24: 433–8
Randomisation. Technique for allocating subjects (e.g. patients to treatment groups in clinical trials) that reduces allocation bias when samples are compared. Ensures that factors such as age, sex and weight are randomly distributed amongst the groups; i.e. any difference in these factors is due to chance alone.
Ranitidine hydrochloride. H2 receptor antagonist; better absorbed and more potent than cimetidine, with fewer side effects. Does not inhibit hepatic enzymes or interfere with metabolism of other drugs. Oral bioavailability is about 50%. Plasma levels peak within 15 min of im injection and 2–3 h after oral administration; effect lasts about 8 h. Half-life is about 2 h. Undergoes hepatic metabolism and is excreted via urine, hence the dose is reduced in renal failure.
• Dosage:
150–300 mg orally bd. For prophylaxis against aspiration pneumonitis, 150 mg orally qds (e.g. in labour), or 2 h preoperatively (preferably preceded by 150 mg the night before).
• Side effects: blood dyscrasias, impaired liver function and confusion; all are rare.
Ranking, see Statistical tests
Rapacuronium bromide. Non-depolarising neuromuscular blocking drug, introduced in the USA in 1999 and withdrawn in 2001 just before its introduction in the UK, because of reports of fatal bronchospasm. Chemically related to vecuronium, it causes rapid onset of neuromuscular blockade (tracheal intubation possible within 60 s) with fast recovery (6–30 min depending on dosage) and was thus suggested as an alternative to suxamethonium.
Rapid opioid detoxification. Technique for treating opioid addiction by precipitating withdrawal using opioid receptor antagonists, e.g. naloxone or naltrexone, supposedly reducing relapse rates compared with conventional management. Ultra-rapid opioid detoxification refers to administration of general anaesthesia or heavy sedation for prolonged periods to reduce awareness or recall of unpleasant withdrawal symptoms whilst the opioid antagonists are given. The technique is controversial (especially the ultra-rapid form) since deaths have occurred and supportive evidence for its efficacy is poor.
Rapid sequence induction, see Induction, rapid sequence
Rate–pressure product (RPP). Product of heart rate and systolic BP, used as an indicator of myocardial workload and O2 consumption. It has been suggested that RPP should be maintained below 15 000 in patients with ischaemic heart disease during anaesthesia. Its usefulness has been questioned, since a proportional increase in rate may increase myocardial O2 demand more than the same increase in BP. A pressure–rate quotient (MAP/rate) of < 1 has been suggested as being a better predictor of myocardial ischaemia.
Reactance. Portion of impedance to flow of an alternating current not due to resistance; e.g. due to capacitance or inductance. Given the symbol X, and measured in ohms.
Rebreathing techniques, see Carbon dioxide measurement
Receiver operating characteristic (ROC) curves. Curves drawn to indicate the usefulness of a predictive test, originally derived from analysis of radar signals between the World Wars (i.e. did a deflection represent a real signal or just random noise; and if the former, with what degree of certainty?). For the test to be analysed (e.g. the usefulness of ASA physical status to predict mortality after anaesthesia), each cut-off level is examined in turn, and sensitivity and specificity calculated for it. Thus, for example, an ASA grade of 1 has high sensitivity (all deaths have an ASA grade of 1 or above) but low specificity (most patients with a grade of 1 or above do not die). For an ASA grade of 2, sensitivity is a little lower (some patients who die have a grade of 1, and will not be predicted by a grade of 2) whilst specificity is higher, although still poor (a grade of 2 is better at predicting death than a grade of 1, although most patients achieving 2 or above still do not die). The process continues until grade 5, which has low sensitivity (few of the deaths have a grade of 5) but high specificity (most patients who are graded 5 do, by definition, die). Sensitivity is plotted against (1 – specificity) and a curve obtained (Fig. 133); the area under the curve (AUC) represents the usefulness of the test: a perfect test includes 100% of the available area and one where prediction is no better than chance, 50%.
ROC curves may be drawn using continuous (e.g. C-reactive protein to predict infection), ordinal (e.g. ASA system) or nominal (e.g. presence of different features on the ECG to diagnose MI) scales. They may also be drawn for different tests in the same plot, allowing comparison between the tests. They also allow selection of the best cut-off to use clinically, usually the uppermost and most left-hand part of the curve, being the best compromise between sensitivity and specificity. They are increasingly used to analyse the usefulness of tests or scoring systems in anaesthesia and intensive care, including difficult tracheal intubation and other outcomes.
Receptor theory. States that receptors are specific proteins or lipoproteins located on cell membranes or within cells that interact selectively with extracellular compounds (agonists) to initiate biochemical events within cells. The structures of the agonist and receptor determine the selectivity and quantitative response. Drugs that interact with the receptor and inhibit the effect of an agonist are antagonists. Degree of binding to receptors is affinity; ability to produce a response is intrinsic activity.
Interaction of drug and receptor may resemble Michaelis–Menten kinetics. Covalent, ionic and hydrogen bonding, and van der Waals forces may be involved.
• Different types of receptor:
ligand-gated ion channels: direct opening of membrane pores allowing passage of ions (e.g. Na+, K+, Ca2+, Cl−) across the membrane, e.g. nicotinic acetylcholine receptor. Typically fast responses (< 1 ms).
G protein-coupled receptors: binding to the receptor causes a change in the guanine binding properties of the neighbouring G protein, which then leads to the intracellular response, e.g. adrenergic receptors. Typically of the order of many milliseconds to seconds.
ligand-activated tyrosine kinases: binding at the cell surface causes activation of tyrosine kinase at the inner surface of the cell, which catalyses phosphorylation of target proteins via ATP, e.g. insulin receptors. Typically minutes to hours.
nuclear receptors: the lipid-soluble agonist passes through the cell membrane to interact with the receptor, leading to alteration of DNA transcription, e.g. corticosteroid and thyroid hormones. Typically up to several hours.
Recommended International Non-proprietary Names (rINNs), see Explanatory Notes at the beginning of this book
Record-keeping. The first anaesthetic chart was devised by Codman and Cushing in 1894 at the Massachusetts General Hospital, for recording of respiration and pulse rate. BP charting was included in 1901 at Cushing’s insistence. FIO2 was included by McKesson in 1911.
Careful record-keeping is now recognised as essential to chart preoperative risk factors, the perioperative course of anaesthesia and postoperative events/instructions. It is particularly useful when taking over another anaesthetist’s anaesthetic, and for providing information to those administering anaesthesia subsequently. Similarly, ICU records should chart physiological data, therapy and instructions relating to the stay of any patient in an ICU. Record-keeping is also important for teaching, research and audit, and is extremely important in medicolegal aspects of anaesthesia. Although tending to include similar information, anaesthetic and intensive care charts are not standardised nationally, although this has been suggested.
Automated anaesthetic record systems are increasingly used, sometimes incorporated into anaesthetic machines or ICU monitoring systems. They provide accurate, legible and complete documents for data acquisition and subsequent scrutiny. Data from monitoring devices are incorporated with information provided by the anaesthetist/intensive care staff (e.g. drug or other interventions), although lack of familiarity with keyboards or computers may be a hindrance.
Postoperative recovery and progress may be recorded on separate charts, or on the anaesthetic chart.
Recovery from anaesthesia. Period from the end of surgery to when the patient is alert and physiologically stable. Definition is difficult because some drowsiness may persist for many hours. Recovery testing is used for more precise investigation. Time to recovery depends on the patient’s condition, drugs given, their doses, and the patient’s ability to eliminate them. For inhalational anaesthetic agents, similar considerations as for uptake are involved, plus length of operation and degree of redistribution to fat. Thus blood gas solubility is the most important factor initially, but more potent agents (e.g. isoflurane) are more extensively bound to fat after prolonged anaesthesia than less potent ones, e.g. desflurane. For iv anaesthetic agents, initial recovery is due to drug redistribution from vessel-rich to vessel-intermediate tissues; subsequent course is related to the rate of clearance from the body. Thus propofol characteristically results in rapid clear-headed emergence, whereas thiopental is more likely to produce drowsiness lasting several hours, especially after repeated dosage. Recommendations for provision of recovery care (Association of Anaesthetists):
designated recovery rooms or areas should be used.
during transfer to the recovery area O2 should be administered, and appropriate monitoring performed.
O2 should be administered at least until awake.
there should be criteria for discharge, including full consciousness, clear airway, respiratory and cardiovascular stability, adequate postoperative analgesia and control of PONV, stable temperature and prescription of postoperative drugs, including O2 and iv fluids as appropriate. There should be adequate handover during discharge from the recovery area.
children should be recovered in a designated area.
Patients are often placed on their side, e.g. the recovery position. In the ‘tonsillar position’, the pillow is placed under the loin and the trolley tipped head-down.
respiratory, e.g. hypoventilation, hypercapnia, hypoxaemia, airway obstruction, bronchospasm, aspiration of gastric contents.
cardiovascular, e.g. hypotension, hypertension, arrhythmias, myocardial ischaemia.
related to anaesthetic drugs, e.g. inadequate reversal of non-depolarising neuromuscular blockade, adverse drugs reactions, MH, dystonic reactions, emergence phenomena, central anticholinergic syndrome.
hypothermia, nausea and vomiting, shivering.
Recovery position. Position recommended for unconscious but spontaneously breathing subjects, assuming no contraindication, e.g. cervical spine injury. Encourages a clear airway and drainage of vomitus, secretions and blood away from the airway. Often used during recovery from anaesthesia.
Any recovery position is a compromise between the full prone position (better airway and drainage but more diaphragmatic splinting) and the full lateral position (less diaphragmatic splinting but less effective for the airway and less stable; also may be harmful in neck injury). Classically includes flexion of both arms with the upper hand placed under the jaw to support the airway (Fig. 134). The actual position adopted should reflect the particular circumstances of the case and the need to protect the airway, stabilise the neck and allow unhindered ventilation. It should be possible to observe the patient at all times and to turn him/her supine easily when required.
Fig. 134 Recovery position
staffed by fully trained personnel.
placed near the operating suite, if possible near ICU.
open ward, allowing good patient observation.
at least two bays per operating theatre are recommended.
each bay is equipped for monitoring (ECG, BP, O2 saturation) and patient care (suction, O2).
a supply of iv equipment and fluids, blankets and airways should be available.
adequate ventilation is required to remove exhaled anaesthetic gases.
• Drugs available should include:
analgesics, antiemetics, sedatives, anticonvulsants, naloxone, flumazenil.
doxapram, bronchodilators, corticosteroids, antihistamines.
anticholinergics, antiarrhythmics, antihypertensives, diuretics, heparin.
antibiotics, anticholinesterases, neuromuscular blocking drugs, insulin, dextrose, dantrolene.
Recovery testing. Ranges from simple clinical assessment to more sophisticated methods, e.g. used for experimental comparison between anaesthetic techniques and drugs. Routine testing is usually limited to assessment of general alertness and orientation, and ability to respond, drink, dress and walk where appropriate (e.g. day-case surgery).
• Sophisticated techniques used include tests of:
– assessing speed and number of errors made whilst performing set tasks:
– moving pegs from one set of holes in a board to another set.
– deleting every letter ‘p’ from a page of text.
– tracking moving targets with a pen or light.
– recall or recognition of objects, pictures, words or word associations shown a short time before.
– orientation in time and space.
cognitive function, e.g. adding/subtracting numbers, or adding values of different coins.
physiological function, e.g. divergence of eyes caused by reductions in extraocular muscle tone.
Rectal administration of anaesthetic agents. Results in effective absorption of drugs because of a rich blood supply provided by communicating plexuses formed by the superior, middle and inferior rectal arteries and veins. Drugs undergo minimal first-pass metabolism, because the plexuses are anastomoses between portal and systemic circulations. The technique is usually restricted to children. Traditionally used more in continental Europe, e.g. France. Drugs used have included diazepam 0.4–0.5 mg/kg (widely used for treatment of convulsions in children), methohexital 15–25 mg/kg and thiopental 40–50 mg/kg as 5–10% solutions. Opioids and ketamine have also been given in this way. Diethyl ether was administered rectally by Pirogoff. Bromethol and paraldehyde were used in the 1920s to produce unconsciousness (basal narcosis).
Rectus sheath block. Performed as part of abdominal field block or alone to reduce pain from abdominal incisions. Abdominal contents are not anaesthetised.
With the patient supine, a blunted needle is introduced 3–6 cm above and lateral to the umbilicus. A gentle ‘scratching’ motion may aid identification of the tough anterior layer of the sheath, puncture of which is accompanied by a click. The needle is advanced up to the resistance offered by the posterior layer of the sheath, and 15–20 ml local anaesthetic agent injected after negative aspiration. Deposition of solution between rectus muscle and posterior layer allows spread up and down, blocking the lower 5–6 intercostal nerves within the sheath. Spread between the muscle and anterior layer is limited by the tendinous intersections along its length. Multiple injections have been suggested between intersections, to improve spread, but the posterior layer is deficient below a point halfway between the umbilicus and pubis, and peritoneal puncture is more likely below this level.
Recurarisation. Recurrence of non-depolarising neuromuscular blockade after apparent reversal with acetylcholinesterase inhibitors. Originally described with tubocurarine in patients with impaired renal function, where the duration of action of the neuromuscular blocking drug exceeds that of the acetylcholinesterase inhibitor. Has been described with other neuromuscular blocking drugs.
Red cell concentrates, see Blood products
Reducing valve, see Pressure regulators
Refeeding syndrome. Clinical syndrome seen after reintroduction of nutrition to previously starved patients, often seen on ICU. First noted after World War II, when malnourished prisoners of war inexplicably died of cardiac failure after receiving a normal diet. Associated with any condition leading to malnutrition (e.g. anorexia nervosa, alcoholism, intra-abdominal sepsis).
restoration of carbohydrates as a dietary substrate leads to increased insulin secretion and activation of anabolic pathways. Hypophosphataemia, hypomagnesaemia, hypokalaemia and vitamin deficiency (particularly thiamine) may follow due to increased intracellular uptake on a background of whole body depletion.
depletion of ATP and 2,3-DPG leads to tissue hypoxia and mitochondrial dysfunction.
hyperglycaemia and electrolyte disturbances as above.
