Random Flashcards
How do electrosurgical devices work?
What is the difference between the “cut” and “coag” settings?
Electrosurgery uses radio frequency (RF) alternating current to heat the tissue by RF induced intracellular oscillation of ionized molecules that result in an elevation of intracellular temperature.
If tissue is heated to 60-99 degrees C, the simultaneous processes of tissue desiccation (dehydration) and protein coagulation occur. If the intracellular temperature rapidly reaches 100 degrees C, the intracellular contents undergo a liquid to gas conversion, massive volumetric expansion, and resulting explosive vaporization.
As waveforms of the electrosurgical devices change, so do the tissue effects; “pure-cut” is a uniform waveform resulting in rapid vaporization. Intermittent high voltage waveforms such as “coag” produce less heat and more coagulant.
Define sensitivity, specificity, postive predictive value, and negative predictive value.
- Sensitivity is the proportion of true positives who are correctly identified as such
- Specificity is the proportion of true negatives who are correctly identified as such
- Positive predictive value is the probability that subjects with a positive test truly have the disease.
- Negative predictive value is the probability that subjects with a negative test truly don’t have the disease.
How is disinfection classified?
What methods of sterilization can you describe?
Disinfection is classified as
- Critical
- A device that normally enters sterile tissue or the vascular system
- Such devices must be sterilized, defined as the destruction of all microbial life.
- e.g. biopsy forceps, sphincterotomes
- Semi-critical
- A device that comes into contact with intact mucous membranes and does not ordinarily penetrate sterile tissue.
- These devices require high-level disinfection, defined as destruction of all vegetative microorganisms, mycobacteria, viruses, fungal and some bacterial spores, as represented by a 6-log-reduction in mycobacteria.
- Non-critical
- Devices in contact with intact skin
- Require low-level disinfection.
- Steam autoclave at 120° under 2atm up to 60 min.
- Dry heat at 170° for up to 4 hours
- Ethylene oxide gas (endoscopy)
- Peroxyacetic acid (endoscopy)
- Hydrogen peroxide gas
Discuss surgical drains.
Classified by
Type:
- Passive
- Penrose, Yates post lap chole
- Active
- Blake’s drain post mastectomy
- Irrigating/sump
- Malecot in rectal post Hartmann’s
Indication
- Therapeutic
- Controlled drainage for fistula
- Indicative
- Bile leak
- Prophylactic
- Around revisited anastamosis
Provide an overview of the pathophysiology of sepsis.
The normal response to infection serves to localise and control microbiological invasion. This occurs through the chemotaxis of neutrophils and macrophages, which in turn release inflammatory mediators.
When these inflammatory mediators (IL-1, IL-6, TNF-a) initiate a generalised repsonse, sepsis ensues. Sepsis is characterised by systemic vasodilation and resultant hypotension, increased vascular permeability and resultant oedema, and microcirculatory dysfunction and resultant tissue hypoxia. This downward spiral trend continues unless the anti-SIRS mediators (IL-10, IL-4) compensate to a sufficient degree.
Describe assessment of perioperative risk.
Assessment of perioperative risk fasciliates decision making and informed consent. It also stratifies patients into risk categories, which is helpful for research purposes and audit of morbidity and mortality.
- Gross measurements
- End-of-bed assessment by surgeon
- 0-10m test or “get-up-and-go”
- 6 minute walk test (cheap CPEX)
- Metabolic equivalents (METs)
- Predictive scoring systems
- POSSUM (12 physiological, 6 operative parameters)
- P-POSSUM, V-POSSUM, CR-POSSUM, O-POSSUM - more studies needed.
- ASA
- POSSUM (12 physiological, 6 operative parameters)
- Measurement of physiological reserve
- CPEX testing
Describe the physiology of fever.
Afferent limb
- Exogenous and endogenous pyrogens trigger release of IL-1, TNF-a, IL-6 from monocytes.
- Thermoregulating neurons in hypothalamus stimulated.
Efferent limb
- Sympathetic vasoconstriction, heat preservation, core temp increased
- Peripheral efferent motor nerves contract causing shivering, increases core temp.
What are the pro-inflammatory cytokines?
What are the anti-inflammatory cytokines?
Modulate SIRS:
IL-1, IL-2, IL-6, IL-8, TNF-a, PAF
Modulate CARS:
IL-4, IL-10, IL-13, TGF-b
What are the adrenergic receptors and their activities?
a1
- smooth muscle constriction in blood vessels
- smooth muscle constriction in gut
- glycogenolysis and gluconeogenesis in liver
a2
- smooth muscle contraction in blood vessels
- smooth muscle relaxation in gut
- increases Renin, increases plt agg., inhibits lipolysis
ß1
- chronotropic and inotropic
- intestinal relaxation
ß2
- relaxation of smooth muscle in gut and skeletal muscle
- glycogenolysis
Categorise the surgically correctable causes of hypertension.
Cardiovascular
- Coarctation of the aorta
- Renal artery stenosis
- AAA
- A-V fistula
Adrenal
- Phaeochromocytoma
- CAH
- Cushing’s
Renal
- Renin-producing tumours
- Previous injury to kidney causing Paige kidney
- Polycystic disease
Endocrine
- Acromegaly
- Hyper/hypothyroidism
Neurologic
- Mass lesions causing hypertension
Pregnancy
- Pre-eclampsia
What are the most common, and most deadly, types of cancer in New Zealand for men and women?
NZ Cancer Death
Male
- Lung
- Prostate
- CRC
Female
- Breast
- CRC
- Lung
Cancer Incidence
Male
- Prostate
- CRC
- Melanoma
- Lung
Women
- Breast
- CRC
- Melanoma
- Lung
Most deadly by mortality/diagnosis - Lung, Gastric, Liver
Provide an overview of chemotherapeutic agents.
- Antimicrotubules
- Cell arrest in metaphase
- eg Paclitaxel
- Antimetabolites
- Masquerade as purine analogues
- eg 5-FU, Gemcitabine, MTX, Azathioprine
- Anthracyclines
- Disrupt nucleic acid synthesis
- eg Doxorubicin, Mitomycin
- Alkylating agents
- Add Alkyl group to DNA strand to prevent replication
- eg Platinum agents; Cisplatin etc
- Topoisomerase inhibitors
- Inhibit topoisomerase
- eg Irinotecan
- Antibodies
- Variably affect cell surface receptors
- eg Bevacizumab, Erlotinib, Sumatinib
What are the phases of shock?
- Non-progressive phase
Reflex compensatory mechanisms are activated;
Baroreceptor reflexes, catecholamine release, RAAAS, ADH release, and sympathetic stimulation
Net effect of tachycardia, peripheral vasoconstriction, and renal conservation of fluid
- Progressive phase
With persistent oxygen deficit, intracellular aerobic respiration is replaced by anaerobic glycolysis and excessive production of lactic acid
Acidaemia results and the vasomotor response is blunted leading to vasodilation, peripheral pooling, and worsening shock
- Irreversible phase
In severe cases, widespread injury results in overwhelming lysozymal leakage and cell death
Bacterial superinfection catalyses this and multi-organ failure ensues
What is a sentinel lymph node?
A sentinel lymph node is the first node encountered by a lymphatic channel that is draining a primary site.
There are often up to 3 “sentinel nodes”, as if there is more than one lymphatic channel draining a primary, there will be more than one sentinel lymph node.
It is not necessarily the hottest or closest.
What is anaphylaxis?
Where is it commonly encountered in General Surgery?
- Anaphylaxis is an acute, potentially lethal, multisystem syndrome resulting from the sudden release of mast cell- and basophil-derived mediators into the circulation.
- It most often results from immunologic reactions to foods, medications, and insect stings, although it can also be induced through nonimmunologic mechanisms by any agent capable of producing a sudden, systemic degranulation of mast cells or basophils.
- The diagnosis is based on the involvement of multiple organ systems;
- skin and mucosa
- airway and lungs
- gut (diarrhoea or vomiting)
- cardiovascular (BP, HR, syncope)
- Most commonly encountered in General Surgery in response to perioperative medications
- Antibiotics; 50%! beta-lactams most common
- Blue dye; ~1/200
- Chlorhexidine; up to 2%
- Iodine; shellfish not transferrable
- Latex; OT precautions.
What is ARDS?
- Acute respiratory distress syndrome is an acute, diffuse, inflammatory form of lung injury that is characterised by:
- Respiratory failure with pulmonary oedema
- An antecedent trigger
- The abscence of congestive cardiac failure
- It is associated with a high mortality, usually from the underlying cause.
- Treatment of the underlying cause or inciting event is key, supportive care with escalating assisted ventilation characterises ARDS management.
Describe the disease states associated with Hepatits B
- Hepatitis B is a dsDNS virus that belongs to the hepadnavirus family.
- It is a global health problems with >250million people affected, with over 600,000 people dying each year due to Hep-B related disease.
- Infection is either acute or chronic:
- Acute infection is through transmission of bodily fluid.
- The treatment for acute Hepatitis-B infection is supportive; only 1% will suffer liver failure and only 5% become chronic carriers.
- In complicated cases patients can be treated with entecavir or tenofovir.
- Chronic infection occurs when HepBSAg remains positive for more than 6 weeks
- Most people with childhood-acquired chronic HBV infection will enter a long-term inactive phase associated with persistently normal serum ALT and low serum HBV DNA levels, which may last up to 30 years.
- However, some people will enter an active phase of infection, which is associated with persistently elevated ALT levels, high levels of viral activity, liver inflammation and progressive liver fibrosis.
- Patients with chronic Hep are at increased risk of HCC and cirrhoisis (leading cause of cirrhosis in Maori and PI) so patient require surveillance with AFP and USS.
- Recently, oral antivirals have become available at GPs for (lifelong) treatment of Hep and subsequent risk reduction.
Describe the pathogenesis of intra-abdominal adhesions
- Traumatic injury to the peritoneum (surgery) induces a similar pattern of response exhibited by most tissue
- A reactive response, characterized by coagulation, haemostasis, release of pro-inflammatory cytokines, and chemo-attractants. PAF, IL-1, IL-2, and TNF are key molecules in this phase.
- A regenerative response follows; infiltration with macrophages and fibroblasts generates a proliferative phase of recovery.
- Finally, a remodelling phase ensues where matrix metaloproteinases degrade and remodel tissue substrate.
- The early balance between fibrin deposition and degradation (ie, fibrinolysis) appears to be a critical factor in the pathogenesis of adhesions.
- The relative formation and breakdown of fibrin manifests as different phenotypes within a population, where some individuals form dense asdhesions and other, with a similar stimulus, form few if any.
What are the pathological features of Cowden syndrome?
What tumours commonly occur?
P.A.T.H. B.T.Co.R.E
P= Papilloma
A = Acral keratoses
T = Tricholemomma
H = Hamartomatous polyps
Breast (80%)
Thyroid (20%)
Colorectal cancer (~15%)
Renal cell cancer (~15%)
Endometrial cancer (~15%)
What is the in vivo half life of:
Monocryl?
PDS?
Maxon?
Prolene?
Monocryl = 2 weeks
PDS = 3 weeks
Maxon = 6 weeks
Prolene = 300 days
What is the latest evidence with regard to bowel-prep for colorectal resection?
- Paradigm shift towards giving it again…
- Polyethylene Glycol (“Moviprep”)
- Neomycin 1g (3 doses)
- Metronidazole 1g (3 doses)
- ACS-NSQIP study of ~45,000 patients
- Reduced SSI
- Reduced anastamotic leak
- Reduced overall complications
- Reduced mortality at 30 days
