Electrosurgery

Who first demonstrated the principles of electrosurgery?

Alex d'Arsonval, a French physicist

Who first produced an electrosurgical unit designed for human use?

William Bovie, a Harvard biophysicist

Who popularized the use of "the Bovie"?

Harvey Cushing, MD, the father of modern neurosurgery

Cushing is reknown for developing surgical techniques that reduced the mortality rate of brain surgery from 90% to under 10%.

What is Cushing's Disease?

Secondary hypercortisolism, from a pituitary tumor leading to ACTH-hypersecretion.

Cushing's Syndrome is a more general term, referring to any form of symptomatic glucocorticoid excess, whether from an adrenocortical tumor, or exogenous steroids.

What prestigious award did Cushing receive in his academic career?

The Pulitzer Prize, for his biography "A Life of Sir William Osler"

What is Ohm's Law?

Voltage = Current * Resistance

What is Impedance?

A measure of resistance to flow when using alternating current (AC)

A high cellular water content results in a low tissue impedance.

What is Alternating Current?

Current that cycles in direction at a specific frequency... this comes from a typical US wall outlet at rates of 60Hz.

Electrocautery utilizes direct current (i.e. battery-powered hand-held units), while electrosurgical units utilize alternating current.

What radiofrequencies cause neuromuscular stimulation?

Up to 100kHz

What radiofrequencies cause a generation of heat?

200kHz - 5MHz

What is the Joule-Lenz Law?

Heat dissipated = (Current-density)squared * Resistance * time

Current-density is current divided by cross-sectional area.
Thus, heat generated with electrosurgery is inversely proportional to the area of the electrode and proportional to the time of contact and the impedance of the tissue.

What is monopolar current?

Electricity flowing from a single electrode to the patient.

Monopolar units typically utilize a pencil-type probe that is hand operated. Laparoscopic monopolar cautery may be operated by a foot pedal.

What is a dispersive electrode?

A ground or grounding pad.

Why is a ground pad placed on the patient when using monopolar cautery?

It allows completion of the electric circuit through the patient back to the electrosurgical unit.

Does the size of the ground pad matter?

By being large, it disperses current over a greater surface area. If it were small (i.e. detached/poor contact), it could cause generation of enough heat to create a local burn.

What is bipolar current?

Electricity flows in a closed circuit between two closely placed electrodes (i.e. bipolar forceps or scissors). Current flow and injury to tissue is limited to the region between the electrodes.

Bipolar units typically allow the use of a lower voltage waveform than monopolar units to acheive hemostasis.

What are common modes used by monopolar electrosurgical units?

1. Cutting
2. Coagulation
3. Blend

What are the properties of a cutting waveform?

It uses a continuous (pure sine-wave), low voltage, high-frequency waveform (500kHz) that concentrates energy on a small area.
Instantaneous heating (100 degrees C) results in cellular evaporation at contact, with minimal damage to surrounding tissues.

What are properties of a coagulation waveform?

It uses a pulsed, higher-voltage waveform that allows for dispersal of energy deeper into tissue.
Heating is less (37- 60 degrees C), causing tissue dessication and protein denaturing, allowing for sealing of blood vessels.

What is fulgaration?

Surface coagulation, accomplished by a non-contact method of electrocautery.

What are the properties of a blend mode?

This is a combination of cutting and coagulation waveforms. The higher the blend, the higher the coagulation effects.

What happens to tissue impedance during coagulation?

As water evaporates and tissue dessicates, the tissue impedance increases, leading to increased coagulative effect.

This can also increase the potential of arcing of the current to a lower impedance tissue, leading to iatrogenic injury.

Remember, current flows in the path of least resistance.

What are special hazards seen with laparoscopic electrosurgery?

1. Insulation failure
2. Direct coupling
3. Capacitor coupling

Injury can occur to non-target tissue out of view of the surgical team!

What is insulation failure?

When a defect in the covering of the active electrode allows current to contact non-target tissue.

What is direct coupling?

When the tip of the active electrode comes into contact with another metal instrument in the surgical field.

What is capacitor coupling?

When stray current from an electrode develops by a storage of charge. This can be minimized by activating the active electrode only when it is in contact with target tissues and limiting the amount of time on the coagulation setting.

This can sometimes occur with devices that contain both plastic and metal, allowing for insulation of charge by the instrument or trocar.

For a resource that has some pretty decent illustrations, consider this online course at Valleylab.

Late... SG

Sources:
O'Leary's Physiologic Basis of Surgery, 3rd ed.
Jones CM, Pierre KB, Nicoud IB, Stain SC, Melvin WV. Electrosurgery. Curr Surg 2006; 63: 458-463.

Aphorisms and Quotations

Here's a book for any quote enthusiast:

Aphorisms & Quotations for the Surgeon. Edited by Moshe Schein. tfm Publishing, Ltd. : Shrewsbury, UK; 2003.

For those of you who have been looking for a convenient resource to pepper your next powerpoint presentation with a breath of surgical history, this is the book for you. Even better if you are looking for a little inspiration at the end of the day. In addition to instilling the text with witticisms of his own, Moshe Schein has organized the numerous quotes into 94 different subject headings, ranging from the ubiquitous organ systems, to topics such as academics, dogma, greatness, love, money, politics, gimmicks, fame, ethics, empathy, and errors.

Here are a few:

There are 4 degrees of intra-operative hemorrhage:
1. "Why did I get involved in this operation?"
2. "Why did I become a surgeon?"
3. "Why did I study to become a doctor?"
4. "Why was I born?"
-Alexander A Artemiev

When I am carrying out a big, unusual, or difficult operation, I never plan anything later that day.
-Francis D. Moore

It is a most gratifying sign of the rapid progress of our time that our best textbooks become antiquated so quickly.
-Theodor Billroth

I would like to see the day when somebody would be appointed surgeon somewhere who had no hands, for the operative part is the least part of the work.
-Harvey W. Cushing

Medical examinations: they are no tests of the man. They are only tests for his memory for facts. They tell us nothing of his judgement, tact, energy, enthusiasm, idealism, reason, observation, temperament, disposition, honesty, loyalty, courage, truthfulness, or intelligence. Memory of facts means little. The other things mean nearly all.
-J. Chalmers Da Costa

The pleasure of a physician is little, the gratitude of patients is rare, and even rarer is material reward, but these things will never deter the student who feels the call within him.
-Theodor Billroth

You must always be students, learning and unlearning till your life's end, and if, gentlemen, you are not prepared to follow your profession in this spirit, I implore you to leave its ranks and betake yourself to some third-class trade.
-Joseph Lister

Late... SG

Pancreatic Transplantation

Who discovered insulin?

Banting and Best (1921)

Sir Frederick Banting of the University of Toronto was awarded the Nobel Prize for Medicine/Physiology along with John MacCleod in 1923. He initially refused to accept the award until his research assistant Charles Best's work was acknowledged, but ultimately ended up sharing his portion of the award with Best.

What are the secondary complications of diabetes mellitus?

Retinopathy
Nephropathy
Neuropathy
Enteropathy
Vasculopathy

Diabetes is the leading cause of kidney failure, blindness, nontraumatic amputation, and impotence.

Exogenous insulin can prevent the acute metabolic complications and decrease the secondary complications of diabetes, but cannot maintain a homeostatic environment.

What is the benefit of pancreatic transplantation?

It can establish normoglycemia and insulin independence and can halt the progression of secondary complications of diabetes

What is the drawback of pancreatic transplantation?

Immunosuppression

What are the methods of pancreatic transplantation?

1. PAK - pancreas after kidney transplantation
2. SPK - simultaneous pancreatic/kidney transplantation
3. PTA - pancreas transplant alone

Often PAK and SPK is performed because immunosuppression is already required for a kidney transplant.
PTA may be performed for nonuremic diabetics with a poor quality of life from ketoacidosis, labile glycemic control, or progression of secondary complications of diabetes.

When was the first pancreatic transplant performed?

1966 as an SPK. This was three years after the first kidney transplant.

What techniques are used in the drainage of the pancreas?

1. Enteric drainage (requires creatinine monitoring, for PAK or SPK)
2. Bladder drainage (requires monitoring of urine amylase)

Enteric drainage was performed in the 1970's but was superceded by ureteral, then bladder drainage. Bladder drainage became common in the 1980's, but in the 1990's enteric drainage became repopularized. Enteric drainage has been thought to be more physiologic, but requires a kidney transplant to monitor for rejection.

What are elements of the preoperative evaluation for pancreatic transplantation?

1. Assessment of degree of kidney dysfunction
2. Evaluation of secondary complications of diabetes
3. Coronary Angiography
4. Evaluation of peripheral arterial disease and iliac vessel patency
5. Rule out Malignancy
6. Rule out Infection

Why is coronary angiography often routinely performed?

Because severe diabetics are at risk for coronary arterial disease without angina.

What are the options based on kidney function?

1. PTA if Cr<2.0mg/dL with minimal proteinuria
2. PAK or SPK with moderate kidney insufficiency

What are the donor possibilities for kidney/pancreas transplants?

1. Deceased-donor SPK
2. Living-donor kidney transplant followed by deceased-donor PAK
3. SPLK: Simultaneous deceased-donor pancreas and living-donor kidney transplant
4. Living-donor SPK

What are the elements of preparation of the pancreas graft?

1. Removal of the spleen and excess duodenum
2. Ligation of the vessels at the root of the mesentery.
3. Reconstruction of the arterial system of the graft (Y-graft)

What is a pancreatic Y-graft reconstruction?

The donor SMA and splenic artery are connected using a reversed segment of donor iliac artery.

This creates a common arterial inflow channel for the pancreatic graft

What is the outflow of the pancreatic graft?

Portal vein

What are the components of the pancreatic transplant?

1. Heterotopic placement of pancreatic graft (right iliac fossa or mid-abdomen)
2. Arterial anastomosis: Y-graft to common iliac artery or distal aorta
3. Venous anastomosis: donor portal vein to recipient iliac vein (systemic) or recipient SMV (portal)
4. Drainage procedure: duodenocystostomy or duodenoenterostomy (i.e. Roux en Y)

What are complications associated with bladder drainage?

Dehydration, chronic refractory metabolic acidosis, recurrent UTI, hematuria, bladder calculi, urethritis, urinary leaks

10-20% with bladder drainage are converted to enteric drainage secondary to complications

When is bladder drainage commonly used?

With PTA (allows for rejection monitoring via urinary amylase levels), or when the kidney and pancreas are from different donors.

What are signs of rejection after pancreatic transplants?

-increased creatinine (kidney/pancreas transplants)
-decreased urinary amylase (bladder drainage)
-increased serum amylase
-increased serum glucose

What are other complications of pancreatic transplantation?

1. Infections (10%)
2. Thrombosis (6%)
3. Hemorrhage (<1% of graft loss)
4. Pancreatitis
5. Urologic complications (see bladder drainage)

What are the reported graft survival rates after pancreatic transplantation?

SPK - 90% at 1yr
PAK - 85% at 1yr
PTA - 75% at 1yr

What is a pancreatic islet cell transplant?

Cells are extracted from the islets of Langerhans of donor pancreas and injected into a diabetic patient's portal vein.

This potentially avoids a major surgical procedure, but the patient will still need long-term immunosuppression (use is still often limited to patients needing kidney transplants).

What are problems with Islet cell transplantation?

Islet cell rejection is difficult to monitor and diagnose
Complications such as hepatic abscesses, bacteremia, and portal hypertension can occur
Poor results (<5% insulin-independence at 1yr)

Late... SG

Source:
Schwartz' Principles of Surgery, 8th ed.

Breast MRI

Last week's edition of NEJM had a report on the ability of MRI to detect clinically occult breast cancers in the contralateral breast of patients diagnosed with breast cancer. The link can be accessed here...

This multi-institutional study assessed patients with unilateral breast cancers with a normal mammogram performed in the the contralateral breast. 1007 patients were enrolled at 25 sites; 987 patients were eligible, and 969 participatated with the study. Among index lesions, 58% had infiltrating ductal carcinoma, 20% had DCIS, and 10% had lobular carcinoma.

After evaluation of the contralateral breast using MRI, 33/969 women were diagnosed with breast tumors within the following year; 30 of these lesions were identified by MRI.

Overall, the sensitivity of breast MRI in this population was 91% (CI 76-98%), the specificity was 88% (CI 86-90%), the negative predictive value was 99% (CI 99-100%), and the positive predictive value was 21% (14-27%). The specificity and PPV were significanly higher for postmenopausal women than premenopausal or perimenopausal women.

Positive MRIs resulted in recommendation for biopsy in 135 women; biopsies were performed in 121/969 women (12%). Among the 30 cancers detected, 40% were DCIS and 60% were infiltrating ductal carcinomas (94% T1, 6% T2).

So overall, there was a 3% rate of detection of occult cancers, and a negative biopsy rate of 9%. 25% of biopsies were cancers... It is uncertain how this data would translate to survival benefit.

However, because of this and other reports, the American Cancer Society has provided new recommendations for the use of screening MRI in high risk populations. Here's the open access pdf!

Here, MRI would be recommended as an adjunct to screening mammography. It also shouldn't be performed unless the facility has the capacity to perform MRI-guided biopsies.

In what populations does the ACS recommend Screening Breast MRI based on evidence?

BRCA mutation
First-degree relative (untested) of BRCA positive patient.
Life-time risk calculation >20-25%

In what populations does the ACS recommend Screening Breast MRI based on expert / consensus opinion?

Radiation to the chest between ages 10-30
Li-Fraumeni Syndrome and 1st degree relatives
Cowden Syndrome and 1st degree relatives
Bannayan-Riley-Ruvalcaba Syndrome and 1st degree relatives

What is Li-Fraumeni Syndrome?

An autosomal dominant disease caused by p53 mutation, resulting in predisposition to sarcomas, breast cancers, brain tumors, adrenocortical tumors, as well as numerous others (gastric, pancreatic, ovarian, melanomas, lymphomas...)

What is Cowden Syndrome?

An autosomal dominant disease caused by PTEN mutation, resulting in multiple hamartomatous neoplasms.

What is Bannayan-Riley-Ruvalcaba Syndrome?

Another disease caused by PTEN mutation, resulting in neonatal overgrowth, macrocephaly, lipomas, hemangiomas, lymphangiomas, and hamartomatous polyposis.

In what populations does the ACS not recommend screening Breast MRI?

Women at less than 15% lifetime risk of breast cancer.

They recommended the BRCAPRO and Claus models for calculating the risk, which should be based primarily on family history and genetics for breast and ovarian cancer syndromes. The Gail model was not recommended for determining risk for MRI purposes because it doesn't take account an early age of onset of family members, or 2nd degree relatives with breast cancer.


Late... SG

Sources:
Lehman CD, Gatsonis C, Kuhl CK, Hendrick RE, Pisano ED, Hanna L, Peacock S, Smazal SF, Maki DD, Julian TB, DePeri ER, Bluemke DA, and Schnall MD for the ACRIN Trial 6667 Investigators Group. MRI Evaluation of the Contralateral Breast in Women with Recently Diagnosed Breast Cancer. NEJM 2007; 356(13): 1295-1303.
Smith RA. The Evolving Role of MRI in the Detection and Evaluation of Breast Cancer. NEJM 2007; 356(13): 1362-1364.
Saslow D, Boetes C, Burke W, Harms S, Leach MO, Lehman CD, Morris E, Pisano E, Schnall M, Sener S, Smith RA, Warner E, Yaffe M, Andrews KS, and Russell CA for the American Cancer Society Breast Cancer Advisory Group. American Cancer Society Guidelines for Breast Screening with MRI as an Adjunct to Mammography. CA Cancer J Clin 2007; 57: 75-89.

Clinical Trials

What is a Phase I Clinical Trial?

An experimental study that is designed to evaluate the safety of a treatment.

For pharmacotherapeutics, this often is a trial that escalates a drug to determine dose-limiting toxicities.

What is a Phase II Clinical Trial?

An experimental study that evaluates the biologic response of a treatment.

The results of this kind of trial are often compared to historical controls.

How are responses often categorized for cancer therapeutics?

CR - Complete Response
PR - Partial Response
SD - Stable Disease
PD - Progressive Disease

What is a Phase III Clinical Trial?

An experimental study that evaluates the efficacy of a treatment.

This is typically a randomized, controlled trial.

What is blinding?

A method to minimize bias from the investigators and/or the participants where the individuals are not made aware of treatment assignments.

What are eligibility criteria?

These may be inclusion or exclusion criteria that specify the type of patients that can or cannot be enrolled in the study.

Studies typically exclude minors and pregnant women for ethical reasons.
Studies may also limit participation to people without certain medical problems (i.e., coagulopathy, renal insufficiency).
Studies may try to include only certain patients (i.e. Blunt Trauma patients with a GCS less than 8)

What are some clinical endpoints commonly studied in oncology Phase III trials?

Overall survival
Disease-free survival

Distant disease-free survival may describe the proportion of patients who were alive and did not develop metastatic disease, while disease-free survival describes patients who were alive and did not develop any recurrence (locoregional/distant).

What are methods typically used for survival analysis?

1. Kaplan-Meier Analysis
2. Cox Proportional Hazard Models

Kaplan-Meier curves provide estimates of survival based on the length of follow-up for each individual patient. Patients who are lost to follow-up are censored, while patients who do not survive will cause the curve to go down in proportion to the total number of patients followed at that time interval.

A Cox Proportional Hazard Model is a form of multivariate analysis that allows the investigator to control for known variables (i.e. age, gender,..) that might influence an outcome.

What is the Intention-to-Treat Principle?

The investigators analyze the data keeping patients in their original treatment assignment groups, regardless if patients crossed-over to the other treatment group.

If you designed a study that randomized patients to stenting versus surgical revascularization, and some patients in the stent group ended up having surgery, their outcomes would still be analyzed in the stent group. By not following the intention-to-treat principle, the outcomes of the stent group may be biased against stent failures.

What is clinical equipoise?

The balance between evidence of an experimental therapeutic's efficacy and the degree of uncertainty surrounding the evidence.

This allows for an ethical deliberation leading an investigator to decide to start a study, or to stop a study early.

What is an interim analysis?

A planned preliminary assessment of data to allow for monitoring of various outcome measures.

Stopping rules may terminate a trial early if the data show harm to patients.

What is the Hawthorne effect?

The concept that the knowledge of being observed will affect the behavior of the participants.

While this was initially described in reference to studies on worker productivity under different lighting conditions, patients may avoid unhealthy behaviors if they know they are participating in a clinical trial.

What is a Phase IV Clinical Trial?

After FDA approval of a therapeutic, this is a study that evaluates its effectiveness in a wider population, as well as follows for late adverse events.

So to recap the types of clinical trials:

I - Safety
II - Response
III - Efficacy (RCT)
IV - Effectiveness

Late... SG

Source:
Essentials of Surgical Oncology, Mosby (2007).

Trust in Defecation

April Fools... SG