General Flashcards
Cyclosporin
Inhibits IL-2 from T cells-inhibits proliferation
AIDs defining illness
CD4 300-PCP
CD4 200-Toxoplasmosis and cryptosporidium
CD4
C.Diff causing antibiotics
Clindamycin
Cephalosporins
Augmentin
Tumour markers
CA-125: Ovarian epithelial
CA-19-9: Pancreatic Ca and colon
AFP: liver and yolk sac and testicular teratoma
CEA: Colon and head and neck
HCG: Ovarian, testicular teratoma and seminoma
Amiloride
Non-competitive aldosterone antagonist at the distal convoluted tubule-potassium sparing
Bupivicaine
2mg/kg max safe dose
0.25% contains 2.5mg/ml
therefore safe dose in 70kg (140mg/2.5)=56mls
lidocaine
with adrenaline 3mg/kg
without adrenaline 7mg/kg
Bier’s block
Prilocaine-least toxic and greatest therapeutic index
6mg/ml safest dose
Inducers
Thiopentone sodium: anaphylaxis, bronchospasm and hypotension
Etomidate: Less myocardial depression
Propofol: Care in patients with hypovolaemia
Inhalational anaesthetic
Halothane: Respiratory depression and negative inotrope
Severe hepatotoxicity
malignant hyperthermia (not in NO)
nausea and vomiting
Vomiting is a complex physiological process that initiates repetitive active contraction of the diaphragm and abdominal muscles to generate a pressure gradient that leads to the forceful expulsion of gastric contents. Nausea and vomiting are primarily controlled by the vomiting centre, which receives input from: (i) the chemoreceptor trigger zone (located in the area postrema of the medulla, on the lateral walls of the fourth ventricle outside the blood–brain barrier); (ii) visceral afferents from the gastrointestinal tract, which relay information to the brain regarding gastrointestinal distension and mucosal irritation; (iii) visceral afferents from outside the gastrointestinal tract (bile ducts, peritoneum, heart and a variety of other organs) (stimulation of such afferents helps explain how ‘non-gastrointestinal’ pathology may result in vomiting); and (iv) afferents from extramedullary centres in the brain may be stimulated by certain central stimuli (eg odours, fear), vestibular disturbances (motion sickness) and cerebral trauma. Specific receptors that may be targeted include dopamine (D2), serotonin (5-HT3), histamine (H1) and muscarinic (M1) receptors in the area postrema, H1 and M1 receptors in the labyrinths, and 5-HT3 receptors on peripheral afferents. Many of the anti-emetic drugs act at the level of the chemoreceptor trigger zone. The main classes of anti-emetic agents include: anti-histamine and anti-cholinergic agents, dopamine and serotonin antagonists, and phenothiazines.
Prochlorperazine
Phenothiazine compounds, such as prochlorperazine, appear to act primarily through a central anti-dopaminergic mechanism in the chemoreceptor trigger zone. They are of considerable value in the prophylaxis and treatment of post-operative nausea and vomiting, as well as that associated with diffuse neoplastic disease and radiation sickness. Severe dystonic reactions, neuroleptic malignant syndrome and blood dyscrasias are recognised complications. By contrast, benzamide agents, such as metoclopramide, act as dopamine antagonists, not only centrally but also peripherally. In addition, they exert a prokinetic effect on the upper gastrointestinal tract that contributes to their anti-emetic action
serotonin based antiemetics
Serotonin antagonists have recently been added to the list of clinically effective anti-emetic agents. Specific 5-HT3 antagonists such as ondansetron and granisetron have been developed, and appear to act peripherally (on peripheral afferents) and centrally (on the area postrema). They are particularly useful in the treatment of post-operative and post-chemotherapy nausea and vomiting, where they have been most effective compared to placebo and other agents in large randomised trials. The only other class of anti-emetic that acts both peripherally and centrally is the benzamides, but the benzamides do not exert their peripheral effects on afferent neurones, and have a prokinetic effect, differentiating them from the serotonin antagonists
Suture material
Suture materials can be classified in three main ways:1 Absorbable or non-absorbable2 Monofilament versus braided3 Natural or synthetic.They are also categorised by size.These qualities confer different properties upon the material. Absorbable sutures give less wound support but also less foreign body reaction than non-absorbable. Monofilaments are less traumatic to tissue but are less easy to handle than braided sutures. Synthetic materials cause less tissue reaction than sutures derived from natural fibres and have generally therefore superseded them
PDS
PDSPDS is an absorbable, synthetic monofilament of polydioxanone. It has ideal qualities for use in mass tissue closure, particularly of the abdominal wall. This is because it is predictable and has high tensile strength. It is quoted that PDS retains up to 70% strength at 2 weeks and 50% strength at 4 weeks. It is then completely absorbed in 180–210 days by hydrolysis. Although many surgeons may choose to use nylon for mass closure the attendant risks of sinus formation or stitch extrusion, because of nylon’s non-absorbable properties, render this less suitable for such closure. For mass abdominal closure remember the ‘four to one’ rule. The length of suture used should be four times the length of the wound you are closing. Bites should be taken 1–2 cm apart, and 1–2 cm away from the wound edge to give good closure.
Closure of a cardiac sternotomy wound.
M – Steel wireSteel wire is the material of choice in the closure of sternotomy wounds. It has very high tensile strength and is inert. It may be monofilament or braided and can be very difficult to handle as it kinks easily. It can break and cause pain from sharp ends in the longer term.
prolene
J – ProleneProlene (polypropylene) is a non-absorbable, synthetic monofilament material that is the ideal suture for vascular anastomoses. It is inert, therefore causing minimal tissue reaction, and exerts minimal tissue friction on passage through the vascular endothelium. Braided nonabsorbable sutures can also be used, eg Ethibond. This material has an outer layer of polyester to render it smooth, and hence less traumatic to the arterial wall. Use the finest suture strong enough for the job: as a rough guide, 3/0 for the aorta, 4/0 for the iliac arteries, 5/0 for the femoral arteries, 6/0 for the popliteal artery and 7/0 for the tibial arteries are appropriate strengths.
prolene is an excellent choice when siting the polypropylene mesh used in inguinal hernia repairs. Its persistence allows for good positional maintenance of the mesh as patients begin to mobilise in the post-operative period.
AP resection position
Lloyd DaviesThe patient lies supine on the table, with legs in supports that flex the hips and knees to 45°. The legs can then be separated to allow surgical access to both abdomen and perineum at the same time (as is required during an abdomino-perineal excision of the rectum). To access the pelvis the patient is often also tilted head down, ie Trendelenberg. The lithotomy position is a more exaggerated version of the Lloyd Davies, where hips and knees are flexed to 90°. The lithotomy position was named after the operation that it was historically invented for; the removal of bladder stones. ‘Cutting for stone’ or lithotomy (lithos = stone) was frequently performed by travelling surgeons before the advent of anaesthesia and antisepsis (or fellowships).
A 42-year-old woman undergoing long saphenous vein high ligation, stripping and avulsions.
Table position
J – TrendelenbergIn the Trendelenberg position the patient is placed supine, with head-down tilt. This is the most appropriate patient placement for varicose vein surgery as it helps to alleviate pressure in the lower limb venous system and hence decreases intra-operative blood loss. This position can be also be used during laparoscopic pelvic surgery (eg gynaecological intervention, inguinal hernia repair, rectopexy) to keep bowel loops out of the operating field. The reverse Trendelenberg, as it is logically described, adopts a headup tilt. It is good for use in laparoscopic cholecystectomy/Nissen’s fundoplication, where the abdominal contents need to fall away from the region of intervention.
right nephrectomy-patient table position
Lateral decubitusIn the lateral decubitus position the patient is positioned on the contralateral side to their pathology, and the table is flexed in the centre. This stretches the flank of the patient that is uppermost, ie the side of the renal tumour. In this way there is better exposure of the loin between the bony prominences of the ribs and the iliac crest, clearly improving access and operating manoeuvrability.
arthroscopic rotator cuff
A – ArmchairThe seated armchair position is ideal for access to the shoulder, particularly in arthroscopic cases where dependency of the upper limb opens the subacromial space. This allows for easier insertion of scope and instruments. In difficult cases it also permits a longitudinal or transverse incision through the deltoid to more fully open up the shoulder joint.
Type II Error: In hypothesis testing: the term used to describe a situation in which we fail to reject the null hypothesis when a difference is really present.
Think false positive (T1) False negative (T2)
Type II errorThis is the definition of a term used in the context of hypothesis testing. A type I error in contrast is one in which we reject the null hypothesis when a real difference is not present. These terms are most commonly cited in the context of study design where the probability of type I and II errors can be reduced by performing a prior power analysis in which the correct sample size is estimated on the basis of setting a and ß values which represent the probabilities that a type II and type I error will be committed. NB the null hypothesis is the cornerstone of hypotheticodeductive reasoning (Karl Popper) not a term describing a negative approach to research!
An erroneous influence potentially effecting the conclusions of a trial caused by systematic differences in withdrawals from the trial.: exclusion bias
Exclusion biasThis is one of the four components of systematic bias (the others are in the list) that should be eliminated/minimised by good trial design and conduct. So-called ‘drop outs’ or exclusions from trials can occur for many reasons and can introduce bias quite easily since the tendency (even unintentially) is to exclude participants to favour the outcome of the trial. Where exclusions occur, this problem can be reduced by analysis on an ‘intention to treat’ basis (ie they are still included in the analysis).
minimisation: A method of allocation in comparative studies that provides treatment groups that are very closely similar for several variables.
MinimisationThis is an alternative to simple randomisation (the commonest method used to reduce selection bias) when this might potentially introduce large differences in the characteristics of comparison groups within a trial. Other methods include stratified randomisation but this is usually used for single binary variables such as sex.