SHORT ANSWER QUESTIONS IN ANAESTHESIA SIMON BRICKER PDF
Management - Short Answer Questions in Anaesthesia - by Simon Bricker. Simon Bricker, Countess of Chester Hospital, Chester . PDF; Export citation. Cambridge University Press. - Short Answer Questions in Anaesthesia: An Approach to Written. (and Oral) Answers. Simon Bricker. Köp Short Answer Questions in Anaesthesia av Simon Bricker på PDF-böcker lämpar sig inte för läsning på små skärmar, t ex mobiler.
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Simon Bricker Short Answer Questions
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Problems associated with gas insufflation Gas embolism. May occur in about 1 in laparoscopies and is. Will cause circulatory collapse. CO, is safer in this regard than the alternative gas N20 which is less soluble and will remain within the circulation longer.
Impaired cardiac function. Pneumoperitoneum will cause diaphragmatic splinting. For this reason. Vagally mediated bradycardia from peritoneal distension. More a theoretical than an actual problem as absorption across the peritoneum is relatively slow.
Surgical emphysema and pneumothorax have been reported after. Postoperative pain. May be related to formation of H2CO3 in the peritoneal. Referred shoulder pain is common. Problems associated with position Patient may be head up laparoscopic cholecystectomy with risks of hypotension and cerebral hypoperfusion. Patient may be head down gynaecological and surgical laparoscopy with risks of cerebral oedema and retinal detachment prolonged surgery.
What signs would lead you to suspect that a patient under general anaesthesia was developing malignant hyperthermia?
Describe your immediate management. Malignant hyperthermia MH is a rare clinical syndrome which is usually triggered by drugs used in the course of a general anaesthetic. The fall is due largely to earlier diagnosis and to rapid treatment with dantrolene, and it remains vital that anaesthetists have a high index of suspicion for early recognition of the condition.
These clinical features reflect the fact that MH is a hypermetabolic state which results from decreased control of intracellular calcium. Recognition Preoperatively: Musculoskeletal abnormalities: At induction: During early maintenance of anaesthesia: Tachypnoea if breathing spontaneously. Increasing ETCO2 and rapid exhaustion of soda lime.
Biochemistry at this stage shows high Pso, and elevated K. May get brief hypertension, but sympathetic influence on BP is opposed by tissue mediated vasodilatation and BP may be unchanged. As anaesthesia continues: Rising patient temperature. Later signs: Continuing pyrexia may reach 43C. Hypoxia and hypercapnia. Myoglobinuria rhabdomyolysis.
Multiple ventincular premature beats VBS. Generalised muscle rigidity muscle ATP exhaustion. Hypotension; circulatory failure; cardiac arrest. Management Discontinue all triggers particularly the volatile agents and obtain volatile-free breathing system if practicable.
Hyperventilate with 02 to prevent hyperpania. Dantrolene 1. Early administration is crucial, but the drug is time consuming to prepare. Partially correct acidosis with iv NaHCO, 0. What is the pathophysiology of malignant hyperthermia? How does dantrolene affect the process? How would you investigate a patient in whom the diagnosis is suspected and who presents for non-urgent surgery? Malignant hyperthermia MH is a rare syndrome which is usually triggered by drugs used in the course of a general anaesthetic.
Pathophysiology Following depolarisation Ca" is released from the sarcoplasmic reticulum SR: Contraction and relaxation are energy-dependent processes requiring ATP. MH is a disorder of Ca" control. In skeletal muscle cells exposure to triggering agents such as suxamethonium and volatile anaesthetic agents initiates abnormal release of Ca" from the SR. The site of this abnormality appears to be at the Ca" release channel of the SR, where and this is a simplification of a complex process the ryanodine receptor fails.
The ryanodine receptor protein incorporates the Ca" release channel and spans the cytoplasmic gap between the sarcolemma of the T-tubule and the membrane of the SR. Increased intracellular Ca" has both direct and indirect stimulatory effects on metabolism. Hyperstimulation of aerobic and anaerobic metabolism increases the production of CO, lactic acid and FP ions.
Dantrolene Prevents the release of Ca" from the terminal cisternae of the SR of striated muscle. It does not affect Ca" reuptake. Investigation preoperatively History and family history MH is an autosomal dominant, but genetically heterogeneous. Commonest protocol uses in vitro muscle contracture tests IVCTs in which living skeletal muscle is exposed separately to caffeine and to halothane. Newer techniques: What features would lead you to suspect that a patient undergoing surgery had suffered venous air embolism?
With what procedures may this complication be associated? Subclinical air embolism is common, but on occasion the anaesthetist is faced with cardiovascular collapse. This is an important critical incident which they should be able to diagnose, and part of the diagnosis is dependent on an awareness of procedures which place patients at higher risk. The question does not ask about arterial or paradoxical air embolism. Introduction The circulation can usually accommodate gas bubbles and subclinical air embolism is common.
On occasion, however, gas embolism may be associated with circulatory collapse and so early diagnosis and treatment are essential. Clinical features The venous and pulmonary circulation can accommodate moderate volumes of gas. Air enters the veins this may be audible as a hissing sound and via the right heart gains access to the pulmonary circulation: Pulmonary vascular resistance increases and left atrial filling decreases.
LV filling may decrease and cardiac output and systolic BP may fall. Ventricular ectopics ale common. If the air bubble is large it acts as an air lock and the circulation will fail. Arterial oxygenation and CO, elimination are affected. Gasping respiration if breathing spontaneously , bronchoconstriction, pulmonary oedema. Further aids to diagnosis: Marked increase in CVP if in place; aspiration may confirm presence of air. Doppler ultrasound from right atrium: Transoesophageal echocardiography better than praecordial Doppler.
Procedures implicated Patients are at risk if: Surgery is performed in the sitting position in which the pressure in veins which are higher than the heart is subatmospheric. Examples include some neurosurgical procedures and some shoulder surgery in which the patient is in the 'deck chair' position.
Surgery involving exposure of large areas of tissue, e. Gas is injected under pressure: The circulation is externalised, e.
Simon Bricker Short Answer Questions
Outline the diagnosis and management of massive venous air embolism. Introduction Small air bubbles which gain access to the venous circulation are usually innocuous, but large intravenous volumes of gas may be associated with sudden cardiovascular collapse.
Air embolism may be unexpected and a successful outcome will depend upon rapid diagnosis and immediate initiation of treatment. Diagnosis is assisted by awareness of high risk procedures Mr embolism can occur during any procedure in which-. Surgery is performed in the sitting position in which the pressure in veins which are higher than the heart is subatmospheric, e.
Diagnosis Air enters the veins this may be audible as a hissing sound and via the right heart gains access to the pulmonary circulation: Ventricular ectopics. ETCO, falls and Pco, rises. Management Prevention of further air entry: Inform surgeon of probable diagnosis.
Flood wound with NaC1 0. Compress wound site if feasible. Discontinue N20 will increase functional impact of air bubbles. Minimise possible cardiovascular impact: Change position if possible: Aspirate air from circulation: Cardiorespiratory support: Maintain cardiac output: Describe the anaesthetic arrangements involved in a gynaecology day-case list of 15 patients.
Textbooks do not usually include information on this type of subject. The question aims to assess whether you have a grasp of important skills of anaesthetic management and organisation. Introduction A large day-case surgery list is a logistic and anaesthetic challenge which depends on teamwork, communication and considerable organisation. When it goes well efficient day care is a rewarding part of anaesthetic practice, and with the increasing pressures to perform more and more surgery as day cases it is important that it should do so.
Preoperative selection Patients are unlikely to be seen by an anaesthetist prior to the day of surgery, hence the need for: Detailed selection protocols for use by surgeons and clinic nurses. Pre-admission medical and anaesthetic history questionnaire. On the day of surgery Logistical arrangements Staggered admission of patients to allow unhurried admission and preoperative anaesthetic assessment.
May need planned breaks could coincide with delays, e. Adequate nursing staff: Adequate ancillary staff for patient transport. Large list mandates careful and efficient checking procedures. Anaesthetic techniques Should allow rapid awakening with minimal hangover.
Adequate analgesia and control of postoperative nausea and vomiting PONV both causes of overnight admission. Discharge Ideally list should be arranged to allow staggered discharge by anaesthetist. Discharge protocol conscious level, accompanied, pain free, no nausea, etc.
Written discharge instructions. A patient requiring surgery claims to be allergic to latex. How would you confirm the diagnosis? Outline perioperative management. Latex is ubiquitous in the surgical environment and changes in production methods as well as increased exposure have led to an apparent increase on the number of individuals who are sensitive.
It is an important cause of unexplained intraoperative collapse, and anaesthetists require both a high index of suspicion as well as a clear management plan for the treatment of a patient with this allergy. Introduction It is only in the last decade that latex has been identified as a cause of intraoperative anaphylaxis.
Individuals at risk The patient may fall into one of the following groups: Confirmed diagnosis of latex allergy by skin prick testing or radioallergosorbent RAST test. History of atopy and multiple allergy. Cross-reactivity occurs with some foods, among them avocado, kiwi fruit and chestnuts.
History of sensitivity to latex e. Repeated exposure to latex products: There are two forms of allergy: Type 1 IgE-mediated hypersensitivity anaphylaxis possible. Contact dermatitis: If the history is inconclusive skin prick testing is specific and sensitive in indicating IgE latex antibody. Perioperative management The key is the identification and thereafter avoidance of anything which may contain latex.
Hospitals should have protocols which include lists of latex free equipment: Latex is ubiquitous and is found in: Nursing equipment: Trolley mattresses, pillows, TED stockings lower leg ones are latex free.
Anaesthetic equipment: Bungs in drug vials remove before making up into solution , some giving sets, blood pressure cuffs, face masks, nasopharyngeal airways, breathing systems, electrode pads.
Surgical equipment: Gloves, elastic bandages, urinary catheters, drains. The keys to safe management are to maintain a latex-free environment, to expect to find latex-containing products everywhere, and to maintain complete familiarity with the expeditious treatment of an acute anayphylactic reaction.
What are the causes of heat loss during general anaesthesia? What are the effects of hypothermia in the perioperative period? This topic is of clinical importance, particularly in light of evidence that the maintenance of perioperative normothermia may reduce infection rates and decrease hospital stay. The question also incorporates some basic science.
Introduction The importance of maintaining normal body temperature throughout the perioperative period has been reinforced by recent work which suggests that when this is achieved surgical infection rates and hospital stay are both decreased.
The body is a highly efficient radiator, transferring heat from a hot to cooler objects.
The process is accelerated during anaesthesia if the body is surrounded by cool objects and prevented from receiving radiant heat from the environment. May lose heat internally to cold infused fluids.
Air in the layer close to the body is warmed by conduction, rises as its temperature increases and is carried away by convection currents.
Accelerated during anaesthesia if a large surface area is exposed to convection currents particularly in laminar flow theatres.
As moisture on the body's surface evaporates it loses latent heat of vaporisation and the body cools. This is a highly developed mechanism for heat loss in health, but undesirable during surgery. Accelerated during anaesthesia if there is a large moist surface area open to atmosphere especially e. Accelerated during anaesthesia only if the patient is lying unprotected on an efficient heat conductor e. Should be minimised during anaesthesia by the use of heat and moisture exchangers or use of formal humidifiers.
Anaesthesia Alteration of central thermoregulation hypothalamic. Vasodilatation will increase heat loss. Effects of hypothermia Profound hypothermia with core temperatures of C is unlikely to occur during anaesthesia unless it has been deliberately induced, but it is common to see patients whose temperatures have dropped by several degrees celsius.
The effects of these temperature falls can be summarised as follows: Cardiorespiratory systems Arrhythmias. Decreased cardiac output. Oxygen consumption increases during mild hypothermia 34C. Increase in blood viscosity Mild acidosis. Enzymatic reactions and all intermediate metabolism affected below 34C. Drug actions are prolonged: Surgical outcome There is recent convincing evidence that hypothermia compromises immune function and increases postoperative infection rates.
Wound healing is adversely affected and hospital stay may be prolonged. What hazards does a patient encounter when they are positioned in the lithotomy position for surgery? What additional hazards are introduced when the operating table is tilted head-down?
Describe briefly how these hazards may be minimised. Failure to take appropriate care to avoid morbidity leaves the anaesthetist vulnerable and this 3 an important area of practice. Introduction Me anaesthetised patient is unable to protect themselves in any way from the effects f malpositioning, and it therefore behoves the anaesthetist to ensure that none of ose structures which the awake patient would automatically protect are in any way at risk. The lithotomy position is particularly unnatural.
Lithotomy hazards Lumbar spine In lithotomy rotation of the pelvis flattens the normal convexity of the lumbar spine and places increased strain on interlumbar and lvmbosacral ligaments. This strain is reduced by the use of supporting pillows beneath tl e hips at the sides. Appendages Fingers must be protected. If the arms lie flat by the sides the digits are vulnerable to being trapped by the hinged operating table.
They must not be in direct contact with the metal of the lithotomy poles with which they are commonly level. This is prevented by supporting the arms in a neutral position away from the sides. If thighs and legs are externally rotated, or if the knees are extended, the sciatic nerve may be stretched between its points of fixation sciatic notch and neck of fibula. May follow prolonged lithotomy in flexion of thighs, abduction and external rotation of thighs. May kink the nerve at the inguinal ligament Avoid both of these by minimising these excessive movements.
Common peroneal lateral popliteal. Classic lower limb nerve injury. May be stretched against the head of the fibula by flexion of hips and knees in lithotomy, or may be pressed against the supporting straps. Avoid by padding and by minimising stretch. Posterior tibial. May be compressed against lithotomy stirrup which supports posterior part of the knee.
Avoid such stirrups. At risk of pressure against vertical poles. Ensure adequate padding. Vessels Calf compression may result in venous thrombosis. Compartment syndrome after prolonged surgery has been reported. Circulation and cardiac function Lithotomy has the effect of diverting blood that would have pooled in the lower limbs back to the core.
Rarely, in a patient with precarious cardiac function this effective transfusion can precipitate ventricular failure and pulmonary oedema. More commonly this transfusion can mask the severity of blood loss by increasing venous return. Hazards associated with head-down Trendeienburg position Circulation Head-down tilt exaggerates the circulatory effects already described. Pressure of viscera on diaphragm increases work of breathing. Gas exchange may deteriorate as dosing volume exceeds FRC.
These effects can be attenuated by IPPV. Central nervous system. CSF pressure and cerebral venous pressure increase and so cerebral perfusion pressure decreases.
Cerebral oedema hydrostatic has been described. Retinal detachment has also been described as a complication Intraocular pressure IOP increases. Shoulder retainers which prevent the patient moving backwards may cause pressure injury to the brachial plexus if the Trendelenburg is steep.
What factors predispose a patient to aspirate gastric contents into the lungs during general anaesthesia? How can the risk be minimised? How should pulmonary aspiration be treated? Pulmonary aspiration was implicated by Simpson in the first reported anaesthetic death in and years later the topic is of enduring importance to anaesthetists.
This question tests your knowledge about a core topic related to anaesthetic safety Introduction Prevention of pulmonary aspiration of gastric contents is one of the central tenets of safe anaesthetic practice. The process requires passive regurgitation or active vomiting in the presence of depressed laryngeal reflexes and there are a large number of patients who potentially are at risk. Predisposing factors Gastric volumes May be high in the patient who is not fasted prior to surgery.
Mai be high in presence of outlet obstruction pyloric stenosis or intestinal obstruction. May be high if emptying is delayed by pain, trauma acute gastric dilatation , labour contentious , opioid analgesia, high-fat and high-solid content of a recent meal. May be distended by air insufflated during manual bag and mask ventilation. Oesopliogeal sphincter and lower oesophagus Usually remains tonically constricted.
Distal oesophagus is intra-abdominal and is constricted by 'pinchcock action' of diaphragmatic crura.
Many causes of sphincter incompetence: Tumours or strictures. Laryngeal incompetence Anaesthesia drug induced. Tracheal intubation mechanical effect which may impair competence for up to 8 hours. Head injury and cerebrovascular accident. Postictal also in edampsia with additional confounding features of pregnancy. Coma metabolic or drug-induced. Bulbar problems: Guillain-Barre , motor neurone disease, muscular dystrophies. Prevention Adequate fasting at least 4 hours for solids; 2 hours for fluids.
Longer if high fat. Antacid therapy as premedication: H2 receptor antagonists typically ranitidine ; sodium citrate, proton pump inhibitors typically orneprazole. Rapid sequence induction as standard anaesthetic technique in high risk subjects. High index of suspicion: Emptying of stomach contents. Not currently poplar and success is uncertain.
Avoid general anaesthesia and sedation in favour of regional techniques. Treatment Prompt recognition: No evidence to support use of pulmonary lavage acid damage occurs within 20 seconds. No evidence to support corticosteroids: If no symptoms after -2 hours respiratory problems are unlikely to supervene. Prophylactic antibiotics are not indicated. If earlier symptoms appear patient requires supportive therapy and observation. What factors contribute to postoperative cognitive deficits in elderly surgical patients?
How may these risks be minimised? Confusion in the immediate postoperative period is common enough in the elderly patient almost to be regarded, wrongly, as routine. Thoughtful perioperative management may reduce the problem and it is this which the question seeks to test. Introduction Postoperative cognitive deficits POCD are those which relate to changes in personality, to difficulties with tasks requiring organisation of thought, to problems with soiial relationships and to short term memory lapses.
Given the heterogeneity of the elderly surgical population it is clear that the problem is likely to be multifactorial. It nay be oversimplistic to assume that it is all related to failures of cerebral oxygena! Preoperative factors Pre-existing mental infirmity Alzheimer's disease, other dementias, mild confusional states. It is hard to influence these, although it should be recognised that a simple change of environment may result in total disorientation in time and space for some elderly patients.
Pre-existing cerebrovascular and ischaemic heart disease Cu-morbidity is common. Preoperative management should aim to optimise the various conditions. Perioperative factors Hypocapnia Hyperventilation causes cerebral vasoconstriction and reduction in perfusion. Hypotension Intuitive assumption would cite blood pressure falls as significant.
This is not supported by any available evidence. Hypoxia The role of hypoxia is believed to be indirect via neurotransmitter effects. Postoperative oxygen therapy may reduce risks of cardiac and thence cerebral effects, but is not directly influential on POCD per se.
Drug effects Effect of anaesthetic agents may be mediated via effect on memory processing. Central anticholinergic syndrome. Metabolic disturbance Postoperative hyponatraemia.
Infection Pyrexia and sepsis. Specific procedures may be associated with increased POW Cardiopulmonary bypass Clear evidence that cognitive deficits occur in all age groups. Prolonged extracorporeal perfusion is deleterious. Vascular surgery Influence of aortic cross clamp times is significant. Prolonged surgery and long clamp times deleterious.
Surgery with embolism risk Joint replacement surgery: Carotid end-arterectomy. Neurosurgery Direct interference with cerebral circulation. What immunological consequences may follow homologous blood transfusion? This is a very focused question which does not therefore require any discussion of potential infection risks or The problems of massive transfusion Introduction Amongst the many possible adverse consequences of homologous blood transfusion, immunomodulation was recognised many decades ago, and it actually enjoyed early favour in renal transplant surgery as a deliberate immunosuppressive therapy.
Research has not confirmed the mechanisms by which transfusion achieves this, and there remains no consensus about the significance of its effects. Non-haemolytic febrile reactions.
Urticarial reactions accompanied by pruritus. Hypersensitivity reactions including anapyhylaxis: Major haemolytic reactions: May be immediate: Antibody level at transfusion is low, but an anam. Host attacks foreign RBCs via complement and antibody. Significance waned with advent of effective immunosuppressants ciclosporin A.
Current areas of interest Postoperative infection rates: Tumour recurrence: Studies are contradictory: Inflammatory bowel disease: Effects are more marked with repeated transfusion. Unclear, theories include: Clonal deletion: Active suppression: Outline the effoAs of old age upon morbidity and mortality in an sthesia Anaesthesia for the elderly is of perennial relevance and as the population ages it will become even more so.
This question should pose few problems but it is important to focus the many points down to those which command a high priority. Old age is associated with significant co-morbidity which is superimposed upon the normal changes of ageing, both of which have important implications for anaesthesia. Autonomic nervous system Functional decline: Temperature control is impaired: Cardiovascular system Functional decline: Respiratory system Progressive decline with age: Decreased sensitivity to hypoxia and hypercapnia.
Decreased lung compliance. The airway Edentulous, osteoporotic mandible, poor facial tissue and oropharyngeal muscle tone, cervical spondylosis and osteoarthritis. Gastrointestinal system Slower gastric emptying, parietal cell function impaired, hiatus hernia and reflux more common.
How may anaesthetic technique reduce these risks? Carotid endarterectomy is a common vascular procedure which has attracted recent interest because of the increasing use of regional blockade. The conscious level of the awake patient is an excellent monitor of cerebral blood flow, the maintenance of which must underpin any anaesthetic technique. Introduction Transient ischaemic attacks TIAs have been described as 'fragments borrowed from the stroke that is to come' and this risk is relatively high: A larger number will suffer nonfatal strokes.
Carotid endarterectomy is a prophylactic procedure which aims to reduce this toll. Patients have concomitant cerebrovascular and ischaemic heart disease: Surgery requires cross-clamping: Surgery may dislodge plaque debris.
Surgery may be complicated by perioperative bleeding aspirin treatment is common. Anaesthetic options: Paco2 control. Cerebral protective effect of barbiturates or deep volatile anaesthesia. Use of hypothermia if required. Easier for the surgeon. Potential disadvantages CVS instability associated with maneouvres to secure the airway intubation, etc. Maintenance of high normocapnia is not always easy to achieve during IPPV.
Deep volatile or barbiturate anaesthesia may compromise circulation and make neurological status more difficult to assess. The anaesthetist, therefore, can attenuate the risks of the procedure by manipulating the circulation to try to ensure that cerebral perfusion pressure is maintained.
There is, however, no reliable monitor of the adequacy of cerebral perfusion: Techniques include cervical epidural anaesthesia, local infiltration, and local infiltration together with deep cervical plexus block.
The latter is the most popular in the UK. Decreased requirement for shunting which itself carries significant morbidity. Potential disadvantages Needs cooperative and motivated patient. No airway control important if cervical epidural used. Hypothermia not an option. Myocardial morbidity is unaltered.
Generic disadvantages of the local anaesthetic techniques used. Problematic if conversion to GA is necessary. The large randomised controlled clinical trial to determine whether general or regional anaesthesia is better for carotid endarterectomy has yet to be undertaken. What is the gluc oid response to surgery? Describe your approach to steroid replacement both in patie who are currently receiving corticosteroids and in thc. The stress response to injury can be important in patients who are receiving corti- costeroids.
The traditional concern is related to the danger of precipitating an Addisonian crisis in patients whose hypothalamo-pituitary-adrenal axis is suppressed. There are those who believe the anxieties to be over-stated and certainly the use of potentially dangerous supraphysiological replacement regimens should be abandoned.
Introduction Treatment with corticosteroids has the potential to cause adrenal suppression, and the exaggerated fear of precipitating an Addisonian crisis following surgery has resulted in the common use of supraphysiological replacement regimens. A logical approach to replacement rests on an appreciation of the normal response and that provoked by differing degrees of surgical trauma. Steroid response to surgery S Autonomic nervous system: Increased medullary catecholamines.
Increased presynaptic norepinephrine noradrenaline release. Modification of visceral function renal and hepatic. Renin-angiotensin system stimulates aidosterone release: Hypothalamo-pituitary-adrenal axis Hypothalamic releasing factors stimulate anterior pituitary.
Get increases in: Cortisol ACTH stimulates adrenal glucocorticoid release specific cell-surface receptor: G- protein activation, adenyl cyclase stimulation and increased intracellular cAMP. Normal response: Cortisol output: Rationale underlying perioperative steroid replacement Administration of steroids is assumed to result in suppression and atrophy of the hypothalamo-pituitary-adrenal HPA axis via feedback inhibition of hypothalamic and pituitary function.
Replacement minimises risk of perioperative cardiovascular instability Supraphysiological doses of exogenous steroids, however, risk their numerous complications: Foments on prednisolone 10 mg daily or equivalent have a normal response to I--WA testing and require no supplementation. Patients who have received this amount within 3 months from surgery should be assumed to have some degree of HPA suppression test if possible.
Patients on high dose immunosuppressant therapy must continue this perioperatively. Continue usual dose pieoperatively. Hydrocortisone 25 mg iv at induction. Hydrocortisone mg in first 24 hours continuous infusion. Continue usual dose preoperatively. Hydrocortisone mg per day for hr continuous infusion.
What are the implications of anaesthetising a patient in the prone position? Patients are placed in the prone position both for major procedures such as spinal surgery, but also for relatively more trivial operations such as pilonidal sinus excision or short saphenous vein varicose vein surgery.
It is something that you will encounter, therefore, early in your anaesthetic career and you must be aware of the potential problems. Introduction A patient who is allowed to breathe spontaneously in the prone position has an FRC that is greater than if they were supine, and has less likelihood of aspirating gastric contents.
Those are probably the only benefits to the patient apart from the important fact of optimising surgical access: Respiratory effects FRC is greater than in the supine position an advantage if breathing spontaneously , but the usual prone position may encourage the diaphragm to move cephalad.
If the abdomen is not free from pressure breathing is compromised. Airway Less likelihood of aspiration while actually in the prone position. Access to airway is restricted: Circulation Anaesthetised patients do not tolerate changes in position well: Spinal surgery may also be associated with significant blood loss. Venous return may decrease due to pooling of blood in dependent cephalad half and legs. Abdominal compression may affect venous return via inferior vena cava: Intravenous lines may be dislodged during turning or may be inaccessible after turning: Musculoskeletal Damage can occur during turning which must be done with adequate personnel using a log roll technique.
The neck is particularly vulnerable. Pressure effects Patients are at risk at a number of sites: Eyes and globe: All tigsues must be free from pressure on electrodes, monitoring wires or iv lines. Hard pillows under the pelvis may compress the lateral cutaneous nerve of thigh.
The ulnar nerve is vulnerable at the elbow. The brachial plexus is vulnerable to traction damage if the arms are too far abducted in the forward position with the forearms flexed. What further information do you require and how will this influence your anaesthetic management? The traditional management of patients with pacemakers seemed to rely on the use of the theatre magnet which could never be found.
Modern pacemakers have long since rendered this advice redundant and the subject is now of sufficient complexity and affected patients are common enough to make it a popular examination topic. Introduction Pacemaker technology is complex and detailed information will need to be obtained about the specific unit.
It is also important to identify the underlying primary pathology. Reasons for a permanent pacemaker Complete heart block. Sick sinus syndrome. Bifascicular and trifascicular block. Pacemaker details Is it temporary or permanent? They have a three-letter classification more accurately it is a five-letter classification: Chamber that is paced: V - ventricle; A - atrium; D - dual.
Chamber that is sensed: Mode of response: Programmability and implanted Defibrillator functions make up 4th and 5th letters. Commonest example is VVI: Is it functioning?
When was it sited? When was it last serviced? Implications for anaesthesia Suxaniethonium: Surgical diathermy Cutting Demand pacemakers default to a set rhythm in presence of constant interference. External magnet is a special pacemaker magnet will bypass the sensing mode in a simple programmable demand unit.
Multiprogrammable units may be reprogrammed by diathermy, and this instability may be enhanced by an external magnet. Can reprogramme these to asynchronous fixed rate mode. A paced ventricle with neither sensing nor response modes V00 is unaffected.
Should use bipolar diathermy, minimal energies, short bursts. Indifferent electrode should be sited distant from the pacemaker unit. Otherwise defibrillation can be used if indicated. What factors would alert you to the fact that a patient might be difficult to intubate? This is a core area of knowledge, and safe patient management mandates that every anaesthetist should be familiar with the main factors that may make tracheal intubation difficult.
History Patient may be aware of previous dificulties.
Records may confirm it or document view of glottis as graded by Cormack and Lehane Grades 1 to 4. May have a condition associated with difficult intubation: There are many more. Mouth opening and oral cavity oral and pharyngeal plane Should be at least 3 cm. Note that the effective opening may be reduced by prominent upper incisors.
Actual opening is a function of the temporomandibular joint TMJ and may be affected acutely by pain or chronically by disease processes which affect the joint rheumatoid arthritis, scleroderma, aaomegaly, burns contractures. Macroglossia, high arched palate, prominent and over-riding upper incisors may increase difficulty. Jaw mobility: Extension of the head at the atlanto-occipital joint pharyngeal and laryngeal plane Can be limited by conditions such as ankylosing spondylitis, arthritis, cervical spine surgery, cervical spine injury.
It should be 35 in the normal individual. Viewing of the larynx laryngeal plane Short, thick neck. High anterior larynx. Problems at the laryngeal inlet Compression by external mass: Supraglottic obstruction: Subglottic obstruction; stenosis.
Predictive tests Mallampati test: Class 1 to 4: Less than 7 cm is an indicator of potential difficulty. Hyoid-mandibular distance in extension: Should be at least 3 cm the laryngoscope displaces the tongue into this space. None of these tests is either sensitive or specific enough to predict difficult intubation.
Various combination scores have been suggested such as that proposed by Wilson: Wilson score: Identifies and scores risk factors: Radiology A number of X-ray markers have been associated with difficult intubation: Gap between occiput and spinous process of Cl. Gap between spinous processes of Cl and C2. Occipito-Cl gap.
A patient proves ;Ipossible to intubate. What factors determine the emoglobin desaturation? What can be done to maintain oxygenation in this situation? This situation, although not particularly common 1 in intubations , is one which every anaesthetist must be able to manage safely and expeditiously.
This question explores your understanding of the underlying principles and your practical management of a potentially difficult problem.
Introduction Patients die from failure to oxygenate and not from failure to intubate, and although the clinical situation may be complicated by the need for rapid sequence induction because of a full stomach or gastrointestinal pathology, it should always be retrievable. Basic principles The basal requirement for oxygen is mI min-'. The functional residual capacity FRC in an adult is ml.
Under normal circumstances, therefore, oxygen reserves will be exhausted in -2 minutes. Oxygen reserves Pre-oxygenation: If nitrogen washout has been completed then minutes may elapse before desaturation starts to take place. FRC is decreased or is exceeded by closing capacity in the following groups: Pre-existing pulmonary disease causing shunt will reduce effectiveness of pre- oxygenation.
Haemoglobin concentration: Desaturation rate also depends on oxygen consumption Increased: Maintenance of oxygenation Patients die from failure to oxygenate, not failure to intubate: Proceed to laryngeal mask airway: If ventilation is also impossible a rapid decision to proceed to cricothyroidotomy will be necessary to ensure oxygenation. What safety features should be incorporated into a patient controlled anaesthesia PCA system for adults and what is the purpose of each?
Having sent a patient to the ward with PCA what instructions would you give to the nursing staff? PCA is now widely used and should be familiar to every anaesthetist. This question on a core topic is directed overtly towards its safety aspects and is testing your appreciation of all the potential risks of a very common technique.
Introduction Patient-controlled analgesia systems always comprise a large reservoir of opioids and some means of delivering a dose as the patient demands. It is clear, therefore, that there are several areas of potential hazard. Administration of excessive dose This should be prevented by: Appropriate concentration: Appropriate lock-out time usually 5 minutes.
Electronic pumps are programmable; disposable sets rely on capillary refill to replenish the chamber. Maximum hourly dose. Of importance if a background infusion is added. Microprocessor pumps should incorporate alarms which warn of excessive dose. Anti-siphoning device. A one-way valve should be incorporated into any system which is linked via a Y-connector to a fluid infusion giving set.
Backflow otherwise can occur into the tubing of the fluid infusion which may then deliver a large bolus. As an alternative the PCA can be delivered via a separate dedicated line. The device should not be placed above the level of the patient.
Security Electronic pumps are robust and lockable so that the patient or other party can neither gain access to the syringe, which typically will contain mg morphine, nor alter the programme. Disposable devices are much more vulnerable in this respect. Safety instructions These are to ensure that should the opioid be delivered in excessive dose or have excessive effect the patient will come to no harm. Sedation scoring and respiratory rate Sedation is a more sensitive indicator of opioid overdose than respiratory rate.
Same for respiratory rate and other clinical indices. This instruction varies between units: Nursing staff should be allowed to administer the drug according to a set protocol in the absence of immediate medical help. Any discrepancy should result in discontinuation of PCA pending review. Other monitoring and instructions Location: Sp02 may be normal in presa-ice of respiratory failure, but if hypoventilation is extreme then die patient will desaturate.
Pain scoring Frequency as above. Postoperative nausea and vomiting Prescription for breakthrough anti-emetic and protocol for discontinuing PCA pending medical review. You plan to anaesthetise a patient for total hip replacement under subarachnoid block with sedation. What do you understand by the term 'sedation' in this context, and what drugs and techniques are available? Safe techniques of sedation can be difficult to achieve and this question seeks to explore your understanding of the options and their problems.
Introduction Conscious sedation is a term intended to describe a state in which a drug or combination of drugs is used to cause a modest depression of conscious level without compromising airway, breathing or circulation.
Such a sedated patient will remain cooperative, conscious and in contact with their surroundings. This state is not easy to achieve. Sedation techniques Local anaesthesia. The key to successful sedation is successful local anaesthesia.Urticarial reactions accompanied by pruritus. A concise reference with reviews from nearly 40 international specialists in diverse fields, "The Blood-Brain Barrier and Drug Delivery to the CNS" assesses the properties of the blood-brain barrier to determine and measure drug permeability in animals and humans; presents techniques to predict successful drug uptake through in vitro systems or by computation of physiochemical parameters ;examines the multidrug resistance protein P-glycoprotein as a natural transporter; analyses current drug designs to known requirements for transport; looks at drug delivery systems for the brain and much more!
Such a sedated patient will remain cooperative, conscious and in contact with their surroundings.
Dextran What is the gluc oid response to surgery? Postoperative respiratory insufficiency is an important complication of anaesthesia and surgery which all anaesthetists should be able to recognise, to diagnose and to treat.
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