WHAT ANESTHESIOLOGISTS DO… AN EXAMPLE ANESTHETIC

11 Oct 202028 Oct 2020THE ANESTHESIA CONSULTANT Leave a comment

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Physician anesthesiologist at Stanford at Associated Anesthesiologists Medical Group

Richard Novak, MD is a Stanford physician board certified in anesthesiology and internal medicine.Dr. Novak is an Adjunct Clinical Professor in the Department of Anesthesiology, Perioperative and Pain Medicine at Stanford University, the Medical Director at Waverley Surgery Center in Palo Alto, California, and a member of the Associated Anesthesiologists Medical Group in Palo Alto, California.
emailrjnov@yahoo.com

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Most patients have no real idea what anesthesiologists do. Most college premed students have no real idea what anesthesiologists do. Most medical students have no real idea what anesthesiologists do.

Anesthesiologists are responsible for your medical care before, during, and after surgeries. At Stanford University we’re called the Department of Anesthesiology, Perioperative and Pain Medicine. “Perioperative” means “around the time of operations.” Today I’ll walk you through an example anesthetic which shows how an anesthesiologist approaches the challenges of a difficult surgical problem: emergency non-cardiac surgery in a patient with heart disease.

John Doe is a 58-year-old man with an acute inflammation of his gallbladder (acute cholecystitis), who needs to have his gallbladder removed (cholecystectomy). For the past 24 hours, Mr. Doe has suffered fever and acute right upper quadrant abdominal pain. His general surgeon advises surgery as soon as possible. Mr. Doe’s past medical history is positive for obesity (six feet tall, 240 pounds, BMI=32.5), coronary artery disease, and a history of stable angina.

PREOPERATIVE WORK: Anesthesiologist Dr. A reviews the chart and learns that Mr. Doe has had chest pain (angina) with exercise for the past two years. His cardiologist dida heart catheterization one year ago and discovered that Mr. Doe has small vessel coronary artery narrowing. His narrowed vessels were too small to treat with coronary stents, and Mr. Doe received only medical therapy for his angina, in the form of isosorbide nitrate pills, diltiazem (calcium channel blocker pills), and nitroglycerin tablets as needed for chest pain.

Mr. Doe takes a nitroglycerin tablet about once a week. This medical regimen has been effective in avoiding unstable angina and preventing heart attacks. Mr. Doe also takes atorvastatin (Lipitor) to control his hypercholesterolemia. Dr. A speaks with the cardiologist and asks two questions: “Are there any other diagnostic tests needed before surgery, and are there any other therapeutic measures needed before surgery?” The cardiologist answers that a preoperative echocardiogram is indicated, and he orders the test. The echocardiogram shows Mr. Doe’s heart is contracting normally (ejecting 60% of its volume with every beat). The cardiologist also measures the patient’s blood troponin level. Troponin levels are elevated when a patient is having an acute heart attack. Mr. Doe’s troponin levels are within normal limits, therefore no heart damage has occurred so far. Regarding therapeutic intervention, the cardiologist advises a continuous infusion of nitroglycerin to help prevent cardiac ischemia/heart attack damage during the anesthetic.

An anesthesia machine, with the vital signs monitor screen on the left, and the electronic medical records computer screen on the right.

Dr. A meets Mr. Doe and interviews him. Mr. Doe is currently having moderately severe abdominal pain, nausea, fever, and chills. He has not had any chest pain for the past two weeks, and has no shortness of breath. His vital signs are heart rate = 100, BP = 150/80, respiratory rate = 20 breaths/minute, oxygen saturation 95% on room air, and temperature 100.2 degrees. Dr. A examines the patient and finds that the airway looks normal, the lungs are clear, the heart sounds are normal, and the abdomen is tender over the area of the gallbladder. Dr. A explains the general anesthetic plan to Mr. Doe, and informs the patient that his risk of heart complications for this acute surgery is higher than average because of the past cardiac history. Dr. A then records all pertinent preoperative information into the electronic medical record (EMR) via a computer keyboard and screen located just to the right of his anesthesia machine.

IN THE OPERATING ROOM: Mr. Doe will be asleep for the surgery, and Dr. A will be present the entire time. Mr. Doe has a preexisting intravenous (IV) line in his left arm. Prior to the surgery, Dr. A sedates the patient with 2 milligrams of IV midazolam (Versed) a benzodiazepine anxiety-reducing drug, and 100 micrograms of IV fentanyl, a narcotic.

He then inserts a second catheter into the patient’s radial artery in its location at the right wrist. (I’ll use the male pronoun “he” for Dr. A in this example case, but be aware that as of 2017, 40% of anesthesiologists under the age of 36 years are female. This arterial line is connected to an electronic monitor which shows the blood pressure wave and blood pressure value continuously throughout the anesthetic. Dr. A places five ECG monitoring stickers on the patient’s chest, and a pulse oximeter on the third finger of the patient’s right hand. Dr. A notes the pre-anesthetic vital signs are heart rate = 80 beats/minute, blood pressure (BP) = 130/80, and oxygen saturation = 96% on room air, increasing to 100% on mask oxygen. This data is automatically entered into the chart of the electronic medical record.

MONITORING SCREEN with vs

After the patient breathes oxygen via a mask for two minutes, Dr. A performs a rapid sequence induction of anesthesia by injecting propofol (a hypnotic sleep drug) and succinylcholine (a muscle paralyzing drug) into the IV. The operating room nurse presses down on Mr. Doe’s cricoid cartilage in his neck, to compress the esophagus and prevent any stomach contents from regurgitating upward into the airway.

Ten seconds after the propofol injection the patient is asleep. Forty seconds after the succinylcholine injection the patient is paralyzed. At this time Dr. A inserts a laryngoscope into the patient’s mouth and visualizes the patient’s vocal cords and the opening into the larynx or windpipe.

Under direct vision, Dr. A inserts a hollow plastic endotracheal tube (ET tube) into the patient’s windpipe, and then withdraws the laryngoscope. The cuff on the distal end of the ET tube is located just below the vocal cords, and Dr. A injects 3 milliliters of air into the cuff to inflate it and to secure the tube with a seal at the level of the windpipe.

Dr. A then uses his anesthesia machine apparatus to squeeze breaths through the ET tube into the lungs, and listens to both sides of Mr. Doe’s chest with a stethoscope to document that breath sounds are present in both lungs. Dr. A glances at his anesthesia monitoring screen, which includes a row for the carbon dioxide detected in the exhaled breathing gas. The monitor screen traces a square wave vs. time, indicating that the ventilation of carbon dioxide (CO₂) is now occurring out of the lungs with each ventilation.

Dr. A secures the ET tube to the upper lip with adhesive tape, so the critical breathing tube cannot dislodge during the surgery. He sets the ventilator to deliver a volume of 800 milliliters into the lungs, nine times every minute. He sets the mixture of the inhaled gas as 50% oxygen and 50% air, with a resultant oxygen concentration of 60% oxygen. Dr. A turns on the sevoflurane vaporizer at this point, which releases a 1.5% concentration of sevoflurane vapor into the breathing mixture.

Sevoflurane vaporizer (see yellow knob) on anesthesia machine

Sevoflurane, a potent inhaled general anesthetic drug, travels from the lungs via the blood stream to the patient’s brain, where sevoflurane molecules move from the bloodstream into the brain. This continuous delivery of sevoflurane molecules to the brain assures both sleep and amnesia. Dr. A injects an IV dose of 40 milligrams of rocuronium, a second paralyzing drug which will keep the patient motionless for approximately 30-40 minutes.

Dr. A prepares to start a central intravenous line into the right internal jugular vein. He preps the right side of the patient’s neck with Betadine iodine soap, and drapes the right neck with sterile towels. He places a probe on the patient’s neck from a device called an ultrasound machine. The ultrasound machine bounces soundwaves off the contents inside the neck, and generates a two-dimensional black and white image of the veins, arteries, muscles, and nerves found there.

Dr. A inserts a needle into the right jugular vein under ultrasound visualization, and then inserts a wire through the needle into the lumen (center) of the vein. Seconds later, Dr. A slides a hollow intravenous catheter over the wire 14 centimeters into the center of the right internal jugular vein.

Dr. A removes the wire and connects an intravenous drip to the central line catheter. He then connects a preprepared drip of nitroglycerin to a stopcock located on the central line IV, and turns on a preprogramed machine which infuses a small amount of nitroglycerin into the patient’s internal jugular vein continuously.

Dr. A steps back and surveys the patient’s vital signs. The BP is 100/50. The BP machine’s computer calculates a mean arterial blood pressure (MAP) as ((2 X diastolic BP) + systolic BP)/all divided by 3. The mean arterial pressure is thus ((2 X 100) + 50)/divided by 3 = 250/3, or 83.

The desired range of the mean arterial pressure for this case will be from 65-90, and it will be Dr. A’s job to control the blood pressure within this range. The pulse rate is 60 beats per minute, and it will be Dr. A’s job is to keep the pulse rate from getting too high or too low (60 – 80 beats per minute is a desired goal). The oxygen saturation is 100%, and it will be Dr. A’s job is to keep the oxygen saturation, or O₂sat, between 90-100%.

Dr. A administers an IV dose of an intravenous antibiotic prior to the surgical incision, and also administers two IV antinausea drugs, ondansetron (Zofran) and metoclopropamide (Reglan) prophylactically. He tapes the patient’s eyes shut so the corneas will not dry out and become scratched at any time during the surgery.

Dr. A inserts an oral gastric tube through the mouth into the patient’s stomach, and suctions out any stomach contents. He inserts a temperature probe into the patient’s nose and connects it to a temperature monitor. He assists the nurses in positioning and padding the patient’s arms adjacent to the sides of his abdomen. He then wraps a plastic Bair Hugger blanket over the patient’s upper chest and head, and connects a Bair Hugger device which blows heated air through the bag to warm the patient if necessary during the anesthetic.

The patient is now ready for the surgery to begin.

A nurse preps the abdomen by painting the skin with an antiseptic solution. The scrub technician and the surgeon drape sterile paper barriers over the perimeter of the abdomen, as well as a sterile paper vertical barrier (ether screen) between the anesthesiologist and the abdominal surgical site.

The surgeon calls for a Time Out, at which time the operating room personnel review the patient’s name, the planned surgery, the patient’s allergies, and the estimated time for the surgery. Once the Time Out has been accepted, the surgeon begins the surgery. Almost all gallbladder excisions are done through a laparoscopic approach without opening the abdomen. The surgeon inserts a sharp trocar into the abdomen, removes the central core of this device, and then inflates carbon dioxide gas through the device into the interior of the abdomen.

Once the interior of the abdomen is expanded like a balloon, an instrument with a camera on its tip is inserted into the abdomen, and the two-dimensional image of the interior of the abdomen is viewed on multiple video screens. The surgeon makes multiple small incisions and inserts additional surgical tools inside the abdomen.

The stimulus of the surgical incisions causes the blood pressure to increase. The mean arterial pressure (MAP) rises from 70 to 95. Dr. A deepens the anesthetic by injecting an additional two milliliters (100 micrograms) of IV fentanyl, which returns the MAP to 80 within two minutes. The insufflation of the abdomen with carbon dioxide is stimulating as well, because is stretches the lining of the abdomen (the peritoneum), and the MAP rises to 95 again.

This time Dr. A increases the infusion rate of the nitroglycerin drip. Nitroglycerin dilates the venous blood vessels in the body which lowers the blood pressure, and also dilates the coronary arteries. He also begins a constant infusion of propofol via an intravenous pump to deepen the anesthetic level and lower the blood pressure further. The MAP decreases to 80 once again.

The surgeon requests the operating room table be tilted so the patient’s head is higher than the feet, and the right side of the patient’s body is higher than the left. Dr. A accomplishes this positioning by pushing buttons on the table controls.

The purpose of this positioning is for gravity to move the intestines and abdominal contents downward toward the patient’s feet and toward the left side, thereby clearing the view of the gallbladder area in the right upper quadrant of the abdomen.

There are hemodynamic (blood pressure and heart rate) consequences to this change in positioning. The MAP drops to 55 and the heart rate drops to 55. Dr. A treats the heart rate drop with an IV injection of atropine, an anticholinergic medication which blocks slow heart rates, and the pulse rate climbs back to 65. He chooses to treat the low MAP by injecting a small amount (5 milligrams) of a medication called ephedrine, which acts to increase both blood pressure and heart rate. The MAP returns to 70.

There is minimal bleeding during the gallbladder resection, and the experienced surgeon completes the surgery in 45 minutes. During this time Dr. A continues the maintenance anesthesia of sevoflurane and propofol, and injects further doses of the paralyzing drug rocuronium 20 milligrams (to keep the patient paralyzed ) and the narcotic fentanyl 100 micrograms (to provide ongoing pain relief).

As the surgeons close the final incisions, Dr. A removes the oral gastric tube and weans off the anesthesia drugs. The propofol infusion is discontinued. The sevoflurane is discontinued. The operating room table is returned to a level position. The rocuronium paralysis is reversed by the IV injection of a medication called sugammadex. As the anesthesia lightens, a predictable increase in blood pressure and pulse rate occurs, as the patient’s body begins to sense the stimulation of the breathing tube within the trachea and the sensation of the completed surgical repair. Once the patient is awake enough to breathe on his own, Dr. A removes the ET tube and places an oxygen mask over the patient’s nose and mouth.

All critical care medicine is an effort to maintain Airway-Breathing-Circulation, in that order. Dr. A confirms that the patient’s airway is open in the absence of the ET tube, and that the patient is breathing adequately.

Dr. A rechecks the vital signs and sees that the oxygen saturation is 98%, the pulse rate is 110, and the MAP is 110. The elevated pulse rate and blood pressure are dangerous in terms of this patient’s known coronary artery disease. The elevated high heart rate increases the cardiac oxygen consumption and lowers the time for the coronary arteries to fill between beats. The elevated blood pressure also increases the cardiac oxygen consumption, and puts the patient at a higher risk for heart damage or a heart attack. Dr. A treats both the elevated heart rate and blood pressure by injecting 10 milligrams of labetalol (an intravenous beta-blocker drug) which lowers the heart rate to 90 and lowers the MAP to 90 within two minutes. A second dose of IV labetalol brings the heart rate to 70 and the MAP to 80 within another two minutes. At this point Dr. A is satisfied that the patient is stable, and the staff prepares to transfer the patient to the post anesthesia care unit (PACU). A hospital bed is stationed to the side of the operating room table, and the monitors are disconnected from the patient.

The orderlies, nurses, and doctors slide a roller device under the patient, and on the count of three they roll the patient onto the hospital bed. Dr. A secures an oxygen mask over the patient’s face, elevates the patient’s head to 30 degrees, and makes sure the IV line, the arterial line, and the internal jugular line tubings are all intact and not tangled for the transfer to the PACU. The baseline infusion of the nitroglycerin is continued throughout, as the cardiologist requested.

POSTANESTHESIA: In the PACU, nurses reconnect the patient to the same monitoring devices worn during the anesthetic. A registered nurse personally attends to the patient in the PACU. The anesthesiologist writes all the orders for pain medications, cardiac medications, and anti-nausea medications.

The patient will stay in the PACU for approximately one hour, before he is transferred to the intensive care unit (ICU) for continued observation of his vital signs, cardiac condition, and for ongoing administration of the IV nitroglycerin. Once the patient is transferred to the ICU, Dr. A contacts both the ICU team and the cardiologist and signs off responsibility for the patient to them. In the ICU the cardiologist orders troponin levels once again, to determine whether or not the patient suffered a heart attack during surgery. The troponin levels are found to be low, indicating no heart damage occurred. The patient wakes up in a satisfactory status, with resolution of his abdominal pain. His vital signs remain normal.

On the next day the patient’s nitroglycerin infusion is discontinued, his oxygen therapy is discontinued, and he’s discharged to a post-surgical ward bed. On the following day he’s discharged home.

This describes what an anesthesiologist does in performing a moderately difficult anesthetic. This model case is not unique to a university hospital—it could occur as described in any community hospital near you. Gallbladder surgery is not without risks, and not all gallbladder surgeries end well. In 5-10% of laparoscopic gallbladder surgeries, technical difficulties with the anatomy require the surgeon to switch to an open surgical method which requires a larger incision, and results in more postoperative pain.

As in any intraabdominal surgery, gallbladder surgery can lead to surgical complications such as:

Infection
Bleeding
Swelling
Bile leakage
Damage to the bile duct
Damage to the intestine, bowel, or blood vessels

Laparoscopic gallbladder surgery can lead to postoperative medical complications such as heart attacks, sepsis, pneumonia, pulmonary embolus (blood clot to the lungs), or rarely death. In 1987 pop icon Andy Warhol, age 58, died just hours after gallbladder surgery in a prominent New York City hospital.

No one ever disclosed what went wrong in Mr. Warhol’s case, but the anesthesia challenges for that surgery would have been similar to what was outlined above.

This is what an anesthesiologist does. Your physician anesthesiologist is much more than a “sandman” or a “gas man.” Your physician anesthesiologist is your protector when you lose consciousness and go under the knife. While your surgeon attends to the surgical repair, your anesthesiologist will attend to your heart, brain, lungs, and the rest of your body . . . before, during, and after your surgery.

Additional information on the profession of anesthesiology is available at the American Society of Anesthesiologists website.