02 Perioperative Care

Question 1

A 72-year-old man with a history of multiple myocardial infarctions is scheduled to have an elective sigmoid resection for diverticular disease. A preoperative radionuclide ventriculography shows an ejection fraction of less than 0.35.

Answer 1

This is a “no-go” situation in which cardiac risk in noncardiac surgery is prohibitive. With this ejection fraction, the incidence of perioperative MI is 75 to 85%, and the mortality for such an event is around 55 to 90%. Probably the only option here is not to operate, but to continue with medical therapy for the diverticular disease. Should he develop an abscess, percutaneous drainage would be the only possible intervention.

Question 2

A 72-year-old chronically bedridden man is being considered for emergency cholecystectomy for acute cholecystitis that is not responding to medical management. He had a transmural MI 4 months ago, and currently has atrial fibrillation, 8 to 10 premature ventricular beats per minute, and jugular venous
distention.

Answer 2

This fellow is a compendium of almost all of the items that Goldman has compiled as predictors of operative cardiac risk. In fact he adds up to 50 points, and anything above 25 points (class IV) gives a mortality in excess of 22%. Here again the best option would be to treat the cholecystitis in a different way (percutaneous radiologic tube cholecystostomy being the obvious choice).

Question 3

A 72-year-old man is scheduled to have an elective sigmoid resection for diverticular disease. In the preoperative evaluation it is noted that he has venous jugular distention.

Answer 3

Now we have fewer items, but congestive heart failure is the worst one on the list (the other one here is his age). The failure has to be treated first: ACE inhibitors, beta-blockers, digitalis, and diuretics.

Question 4

A 72-year-old man is scheduled to have an elective sigmoid resection for diverticular disease. In the preoperative evaluation it is ascertained that he had a transmural MI 2 months ago.

Answer 4

The next worst Goldman finding is the recent MI (<6 months). Time is the best therapy for that one. Mortality is highest within 3 months of the MI (near 40%), but is brought down considerably after 6 months (6%). Waiting is the obvious choice here. If our hand is forced and earlier operation becomes mandatory, admission to the intensive care unit (ICU) the day before surgery is recommended, to “optimize” all the cardiac parameters.

Question 5

A 72-year-old man who needs to have elective repair of a large abdominal aortic aneurysm has a history of severe, progressive angina.

Answer 5

For many years it was believed that coronary revascularization prior to major surgery improved the risk of the latter. Current reviews of the available evidence suggest that it does not. The planned surgery for the aneurysm can be done first if it is more urgent than addressing the angina.

Question 6

A 61-year-old man with a 60 pack-year smoking history and physical evidence of chronic obstructive pulmonary disease (COPD) needs elective surgical repair of an abdominal aortic aneurysm. He currently smokes one pack per day.

Answer 6

Smoking is by far the most common cause of increased pulmonary risk, and the main problem is compromised ventilation (high Pco2 and low FEV1) rather than compromised oxygenation. Start the evaluation with FEV1. If it is abnormal, perform blood gases. Cessation of smoking for 8 weeks and intensive respiratory therapy (physical therapy, expectorants, incentive spirometry,
humidified air) should precede surgery.

Question 7

A cirrhotic is bleeding from a duodenal ulcer. Surgical intervention is being considered. His bilirubin is 3.5, his prothrombin time is 22 seconds, his serum albumin is 2.5, and he has ascitis and encephalopathy.

Answer 7

Please don’t! Any one of those items alone (bilirubin above 2, albumin below 3, prothrombin above 16, and encephalopathy) predicts a mortality of over 40%. If three of them are present, the number is 85%, and with all four we are talking about 100%.

Question 8

I. A cirrhotic with a blood ammonia concentration above 150 ng/dl needs an operation.
II. A cirrhotic with an albumin level below 2 needs an operation.
III. A cirrhotic with a bilirubin above 4 needs an operation.

Answer 8

Another way to look at liver risk is to see if any one of the previously listed findings is deranged to an even greater degree. Any one of these three examples would carry a mortality of about 80%. A deranged prothrombin time is slightly kinder to the patient, predicting only a 40–60% mortality. Death, incidentally, occurs with high-output cardiac failure with low peripheral resistance.

Question 9

An elderly gentleman needs palliative surgery for an advanced cancer of the colon. He has lost 20% of his body weight over the past 2 months, and his serum albumin is 2.7. Further testing reveals anergy to injected skin-test antigens and a serum transferrin level of less than 200 mg/dl.

Answer 9

Any one of these four findings indicates severe nutritional depletion. All four leave no doubt as to the enormous operative risk that this man represents. Surprisingly, as few as 4 or 5 days of preoperative nutritional support (preferably via the gut) can make a big difference, and 7 to 10 days would be optimal if there is no big hurry to operate.

Question 10

An elderly diabetic man presents with a clinical picture of acute cholecystitis that has been present for 3 days. He is profoundly dehydrated, in coma, and has a blood sugar of 950, severe acidosis, and ketone bodies “all over the place.”

Answer 10

The treatment of diabetes is not within the scope of this surgical review, but we should point out that someone in overt diabetic ketoacidotic coma is not a surgical candidate, no matter how urgent the operation might be. The metabolic problem has to be addressed first in this case (although aiming for complete correction to normal values would be unrealistic as long as that rotten gallbladder is there).

Question 11

Shortly after the onset of a general anesthetic with inhaled halothane and muscle relaxation with succinylcholine, a patient develops rapid rise in body temperature, exceeding 104°F. Metabolic acidosis and hypercalcemia are also noted. A family member died under general anesthesia several years before, but no details are available.

Answer 11

A classic case of malignant hyperthermia. The history should have been a warning, but once the problem develops, treat with IV dantrolene plus the obvious support measures: 100% oxygen, correction of the acidosis, cooling blankets, watch for myoglobinuria.

Question 12

Forty-five minutes after completion of a cystoscopy, a patient develops chills and a fever spike of 104°F.

Answer 12

This early on after an invasive procedure, and this high fever, means bacteremia. Take blood cultures times 3, and start empiric antibiotic therapy.

Question 13

In the first postoperative day after an abdominal procedure, a patient develops a fever of 102°F.

Answer 13

Fever on day one means atelectasis, but all the other potential sources have to be ruled out. Management would include chest x-ray, look at the wound and IV sites, inquire about urinary tract symptoms, and improve ventilation: deep breathing and coughing, postural drainage, incentive spirometry. The ultimate therapy for major, recalcitrant atelectasis is bronchoscopy.

Question 14

In the first postoperative day after an abdominal procedure, a patient develops a fever of 102°F. The patient is not compliant with therapy for atelectasis, and by the third postoperative day he still has daily fever in the same range.

Answer 14

Now a pneumonic process has developed in the atelectatic segments. Chest x-ray, sputum cultures, and appropriate antibiotics are needed.

Question 15

I. A patient who had major abdominal surgery is afebrile during the first 2 postoperative days, but on day 3 he has a fever spike to 103° F.
II. A patient who had major abdominal surgery is afebrile during the first 4 postoperative days, but on day 5 he has a fever spike to 103° F.
III. A patient who had major abdominal surgery is afebrile during the first 6 postoperative days, but on day 7 he has a fever spike to 103° F.

Answer 15

Every potential source of post-op fever always has to be investigated, but the timing of the first febrile episode gives a clue as to the most likely source. The mnemonic used (sequentially) is the “four Ws”: wind (for atelectasis), water (for urine), walking (for the veins in the leg), and wound. Thus urinary tract infection, thrombophlebitis, and wound infection are the likely culprits in these vignettes. Urinalysis and urinary culture, Doppler studies, and physical examination are the respective tests.

Question 16

A patient who had major abdominal surgery has a normal postoperative course, with no significant episodes of fever, until the 10th day when he begins to spike temperatures up to 102 and 103°F every day.

Answer 16

Now ≥1 deep abscess (pelvic or subphrenic) is the most likely source, and CT scans have to be done until it is found (and drained percutaneously).

Question 17

I. On the second postoperative day after an abdominoperineal resection for rectal cancer, a 72-year-old man complains of severe retrosternal pain, radiating to the left arm. He also becomes short of breath and tachycardic.
II. During the performance of an abdominoperineal resection for rectal cancer, unexpected severe bleeding is encountered, and the patient is hypotensive on and off for almost 1 hour. The anesthesiologist notes ST depression and T wave flattening in the ECG monitor.

Answer 17

Perioperative MI happens within the first 3 days, and the biggest triggering cause is hypovolemic shock. These two are fairly typical scenarios, although the classic chest pain picture is often obscured by other ongoing events. When thinking MI everybody does an ECG, but the most reliable diagnostic test is troponin.

Question 18

On the seventh postoperative day after pinning of a broken hip, a 76-year-old man suddenly develops severe pleuritic chest pain and shortness of breath. When examined, he is found to be anxious, diaphoretic, and tachycardic, and he has prominent distended veins in his neck and forehead.

Answer 18

Chest pain this late post-op is pulmonary embolus (PE). This patient is obviously at high risk, and the findings are classic. If they give you a similar vignette in which the venous pressure is low, it virtually excludes this diagnosis. Arterial blood gases are your first test, and hypoxemia and hypocapnia are the obligatory findings (in their absence, it is not a PE either). Although pulmonary angiography is the “gold standard,” it is invasive and rarely done. Spiral CT scan with intravenous dye (sometimes referred to as a “CT angio”) is the diagnostic test of choice.
Therapy starts with heparinization. The very active natural fibrinolytic mechanism in the lung makes the use of clot busters less clearly indicated, but if PEs recur during anticoagulation, a vena cava filter (Greenfield) is needed.
This man already had a PE. It is too late to think about preventive measures on him, but read the narrative portion of this book for a brief review of those.

Question 19

An awake intubation is being attempted in a drunk and combative man who has sustained gunshot wounds to the abdomen. In the struggle the patient vomits and aspirates a large amount of gastric contents with particulate matter.

Answer 19

The nightmare of every anesthesiologist. Aspiration can kill a patient right away, or produce chemical injury to the tracheobronchial tree, with subsequent pulmonary failure, and often secondary pneumonia.
Prevention is best (empty stomach, antacids before induction), but once it happens, lavage and removal of particulate matter is the first step (with the help of bronchoscopy), followed by bronchodilators and respiratory support. It is too late for steroids to help.

Question 20

A trauma patient is undergoing a laparotomy for a seat belt injury. He also sustained several broken ribs. Halfway through the case it becomes progressively difficult to “bag” him, and his blood pressure steadily declines, while the CVP steadily rises. There is no evidence of intraabdominal bleeding.

Answer 20

Intraoperative tension pneumothorax. The lung was punctured by one of the broken ribs. The best approach is immediate thoracic needle decompression. The formal chest tube can be placed later.

Question 21

Eighteen hours after major surgery, a patient becomes disoriented.

Answer 21

Very brief vignette, but out of the very long list of things that can produce post-op disorientation, the most lethal one if not promptly recognized and treated is hypoxia. So, unless it is clear from the vignette that we can blame metabolic problems (uremia, hyponatremia,hypernatremia,
ammonium, hyperglycemia, delirium tremens [DTs], or our own medications), the safest thing to ask for first is blood gases.

Question 22

In the second week of a stormy, complicated postoperative period in a young patient with multiple gunshot wounds to the abdomen, he becomes progressively disoriented and unresponsive. He has bilateral pulmonary infiltrates, and a Po2 of 65 while breathing 40% oxygen. He has no evidence of congestive heart failure.

Answer 22

The reason for the mental changes are obvious: he is not getting enough oxygen in his blood, but the rest of the findings specifically identify adult respiratory distress syndrome (ARDS). The centerpiece of therapy for ARDS is PEEP, with care not to use too much volume, which may damage the lungs. Another issue is why does he have ARDS? In an older patient we can blame preexisting lung disease, and when there has been trauma to the chest, that can be the cause—but when those are not present, we have to think of sepsis as the precipitating event.

Question 23

An alcoholic man checks in to have an elective colon resection for recurrent diverticular bleeding. He swears to everyone that he has not touched a drop of alcohol for the past 6 months. In the third postoperative day he becomes disoriented and combative, and claims to see elephants crawling up the walls. The wife then reveals that the patient actually drank heavily up until the day of hospital admission.

Answer 23

These are obviously DTs. The standard management relies on benzodiazepines. In the past surgeons used intravenous alcohol (5% alcohol/5% dextrose but this is most uncommon today).

Question 24

Twelve hours after completion of an abdominal hysterectomy, a 42-year-old woman becomes confused and lethargic, complains of severe headache, has a grand mal seizure, and finally goes into a coma. Review of the chart reveals that an order for D5W, to run in at 125 ml/h, was mistakenly implemented as 525 ml/h.

Answer 24

A classic example of water intoxication. The laboratory finding that will confirm it will be a very low serum sodium concentration. Mortality for this iatrogenic condition is very high, and therapy very controversial. Very careful use of hypertonic saline is probably a reasonable answer.

Question 25

Eight hours after completion of a trans-sphenoidal hypophysectomy for a prolactinoma, a young woman becomes lethargic, confused, and eventually comatose. Review of the record shows that her urinary output since surgery has averaged 600 ml/h, although her IV fluids are going in at 100 ml/h.

Answer 25

The reverse of the previous vignette. Large, rapid, unreplaced water loss from surgically induced diabetes insipidus. The lab will show significant hypernatremia, and the safest therapy would use one-third or one-fourth normal saline to replace the lost fluid, although in this acute setting D5W would be acceptable.

Question 26

A cirrhotic patient goes into coma after an emergency portocaval shunt for bleeding esophageal varices.

Answer 26

Brief but obvious: the culprit here will be ammonium. If there is also hypokalemic alkalosis and high cardiac output–low peripheral resistance, overt liver failure has occurred.

Question 27

Six hours after undergoing a hemorrhoidectomy under spinal anesthesia, a 62-year-old man complains of suprapubic discomfort and fullness. He feels the need to void but has not been able to do so since the operation. There is a palpable suprapubic mass that is dull to percussion.

Answer 27

By far the most common post-up urinary problem is inability to void, and men are the likely victims. In-and-out bladder catheterization is the answer. Some authors recommend leaving an indwelling Foley catheter if catheterization has to be repeated in 6 hours, others wait until it has been done twice before suggesting it.

Question 28

A man has had an abdominoperineal resection for cancer of the rectum, and an indwelling Foley catheter was left in place after surgery. The nurses are concerned because even though his vital signs have been stable, his urinary output in the last 2 hours has been zero.

Answer 28

In the presence of renal perfusing pressure, an output of zero invariably means a mechanical problem. In this case the catheter is plugged or kinked. More ominous—but much more rare—possibilities include both ureters having been tied off or thrombosis of the renal vessels.

Question 29

Several hours after completion of multiple surgery for blunt trauma in an average-size adult, the urinary output is reported in three consecutive hours as 12 ml/h, 17 ml/h, and 9 ml/h. His blood pressure has hovered around 95 to 130 systolic during that time.

Answer 29

His kidneys are perfusing, but he is either behind in fluid replacement, or has gone into renal failure. A fluid challenge would suggest which one (a bolus of 500 ml given in 10 or 20 minutes should produce diuresis in the dehydrated patient, but not in renal failure), but the more elegant way (and the answer in the exam) is to look at urinary sodium. The dehydrated patient will be retaining sodium, and the urine will have less than 10 or 20 mEq/L. In renal failure the figure will be >40. An even more elegant calculation is the fractional excretion of sodium, which in renal failure exceeds 1.

Question 30

Four days after exploratory laparotomy for blunt abdominal trauma with resection and reanastomosis of damaged small bowel, a patient has abdominal distention, without abdominal pain. He has no bowel sounds and has not passed flatus, and his abdominal x-rays show dilated loops of small bowel without air fluid levels.

Answer 30

Probably paralytic ileus, which can be expected under the circumstances. NPO and NG suction should be continued until peristaltic activity resumes. Should resolution not be forthcoming, mechanical obstruction should be ruled out with a CT scan of the abdomen that will demonstrate a transition point between the proximal, dilated bowel and the distal collapsed bowel at the site of obstruction. Hypokalemia should also be ruled out.

Question 31

An elderly gentleman with Alzheimer’s disease who lived in a nursing home is operated on for a fractured femoral neck. On the fifth postoperative day it is noted that his abdomen is grossly distended and tense, but not tender. He has occasional bowel sounds. X-rays show a very distended colon, and a few distended loops of small bowel.

Answer 31

In the elderly who were not very active to begin with and are now further immobilized, massive colonic dilatation (Ogilvie syndrome) is commonly seen. Correct fluids and electrolytes first. Neostigmine can dramatically improve colon motility, but it has significant side effects. Colonoscopy is a common successful treatment.

Question 32

On the fifth postoperative day after a laparotomy, it is noted that large amounts of salmon-colored clear fluid are soaking the dressings.

Answer 32

The classic presentation of a wound dehiscence. Patient must go to the operating room for repair.

Question 33

The nurses report that a patient on his fifth postoperative day after a laparotomy has been draining clear pink fluid from his abdominal wound. A medical student removes the dressing and asks the patient to sit up so he can get out of bed and be helped to the treatment room. When the patient complies, the wound opens widely and a handful of small bowel rushes out.

Answer 33

This one is evisceration, a rather serious problem. Put the patient back in bed, cover the bowel with large moist dressings soaked in warm saline (moist and warm are the key), and make arrangements to rush him to the OR for reclosure.

Question 34

On the seventh postoperative day, the inguinal incision of an open inguinal herniorrhaphy is found to be red, hot, tender, and boggy. The patient reports fever for the past 2 days.

Answer 34

Wound infection. This far advanced there is sure to be pus, and the wound has to be opened. If it were just a bit of redness early on, antibiotics might still be able to abort the process. If there is doubt as to the presence or absence of pus, a sonogram is diagnostic.

Question 35

Nine days after a sigmoid resection for cancer, the wound drains a brown fluid that everybody recognizes as feces. The patient is afebrile, and otherwise doing quite well.

Answer 35

A fecal fistula, if draining to the outside, is inconvenient but not serious. It will close eventually with little or no therapy. If feces were accumulating on the inside, the patient would be febrile and sick, and would need drainage and probably a diverting colostomy.

Question 36

Eight days after a difficult hemigastrectomy and gastroduodenostomy for gastric ulcer, a patient begins to leak 2–3 L of green fluid per day through the right corner of his bilateral subcostal abdominal wound.

Answer 36

If he is febrile, with an acute abdomen, and sick, he needs to be explored. But if all the gastric and duodenal contents are leaking to the outside, further surgery right away is not the answer. The problem is serious, though. Massive fluid and electrolyte replacement will be needed, and nutritional support will have to be provided with elemental nutrients delivered into the upper jejunum
(total parenteral nutrition [TPN] is a poor second choice), hoping for eventual healing without having to operate again. The abdominal wall has to be protected from the digestion caused by the leaking GI fluids. Somatostatin or octreotide may diminish the volume of GI fluid loss.

Question 37

Eight hours after completion of a trans-sphenoidal hypophysectomy for a prolactinoma, a young woman becomes lethargic, confused, and eventually comatose. Review of the record shows that her urinary output since surgery has averaged 600 ml/h, although her IV fluids are going in at 100 ml/h. A serum sodium determination shows a concentration of 152 mEq/L.

Answer 37

An elevated concentration of serum sodium invariably means that the patient has lost pure water (or hypotonic fluids). Every 3 mEq/L above the normal of 140 represents 1 L lost. This woman is 4 L shy, which fits her history of a diuresis of 500 ml/h more than the intake she is getting. As previously noted, she could be given 4 L of D5W, but many would prefer a similar amount of 5% dextrose in half normal saline, or 5% dextrose in one-third normal saline.

Question 38

Several friends go on a weekend camping trip in the desert. On day 2 they lose their way as well as all connection via electronic devices. They are rescued a week later. One of them is brought to your hospital–awake and alert–with obvious clinical signs of dehydration. Serum sodium concentration is 155 mEq/L.

Answer 38

This gentleman has also lost water, about 5 L, but has done so slowly, by pulmonary and cutaneous evaporation over 5 days. He is hypernatremic, but his brain has adapted to the slowly changing situation. Were he to be given 5 L of D5W, the rapid correction of his hypertonicity would be dangerous. Five liters of 5% dextrose in half normal saline would be a much safer plan.

Question 39

Twelve hours after completion of an abdominal hysterectomy, a 42-year-old woman becomes confused and lethargic, complains of severe headache, has a grand mal seizure, and finally goes into coma. Review of the chart reveals that an order for D5W to run in at 125 ml/h was mistakenly implemented as 525 ml/h. Her serum sodium concentration is 122 mEq/L.

Answer 39

In the surgical patient with normal kidneys, hyponatremia invariably means that water (without sodium) has been retained, thus the body fluids have been diluted. In this case a lot of IV water was given, and the antidiuretic hormone (ADH) produced as part of the metabolic response to trauma has held onto it. Rapidly developing hyponatremia (water intoxication) is a big problem (the brain has no time to adapt), and once it has occurred the therapy is very controversial. Most authors would recommend hypertonic saline (either 3% or 5%) given 100 ml at a time, and reassessing the situation (clinical and lab) before each succeeding dose.

Question 40

A 62-year-old woman comes in for her scheduled chemotherapy administration for her metastatic cancer of the breast. Although she is quite asymptomatic, the lab reports that her serum sodium concentration is 122 mEq/L.

Answer 40

In this setting, water has also been retained (by ADH produced by the tumor), but so slowly that the brain has kept up with the developing hypotonicity. Rapid correction would be lethal and ill advised. Water restriction, on the other hand, will slowly allow the abnormality to be reversed.

Question 41

A 68-year-old woman comes in with an obvious incarcerated umbilical hernia. She has gross abdominal distension, is clinically dehydrated, and reports persistent fecaloid vomiting for the past 5 days. She is awake and alert, and her serum sodium concentration is 118 mEq/L.

Answer 41

Hyponatremia means water retention, but in this case the problem began with loss of isotonic (sodium-containing) fluid from her gut. As her extracellular fluid became depleted, she has retained whatever water has come her way: tea and Coke that she still was able to drink early on, and endogenous water from catabolism. Thus she is now volume-depleted at the same time that she is hyponatremic (hypotonic). She desperately needs volume replacement, but we do not want to correct her hypotonicity too quickly. Thus lots of isotonic fluids (start with 1 or 2 L/h of normal saline or Ringer lactate, depending on her acid-base status) would be the way to go (use clinical variables to fine-tune). Once her volume is replenished, she will unload the retained water and correct her own tonicity.

Question 42

A patient with severe diabetic ketoacidosis comes in with profound dehydration and a serum potassium concentration of 5.2 mEq/L. After several hours of vigorous therapy with insulin and IV fluids (saline, without potassium), his serum potassium concentration is reported as 2.9.

Answer 42

Severe acidosis (or alkalosis, for that matter) results in the loss of potassium in the urine. While the acidosis is present, though, the serum concentration is high because potassium has come out of the cells in exchange for hydrogen ion. Once the acidosis is corrected, that potassium rushes back into the cells, and the true magnitude of the potassium loss becomes evident. He obviously needs potassium. (Under most circumstances, 10 mEq/h is a safe “speed limit.” In this setting, 20 mEq/h can be justified.)

Question 43

An 18-year-old woman slips and falls under a bus, and her right leg is crushed. On arrival at the ER she is hypotensive, and she receives several units of blood. Over the next several hours she is in and out of hypovolemic shock, and she develops acidosis. Her serum potassium concentration, which was 4.8 mEq/L
at the time of admission, is reported to be 6.1 a few hours later.

Answer 43

Let’s count the ways in which potassium has been pouring into her blood: it came out of the crushed leg, it came in with the blood transfusions, and it came from the cells when she became acidotic. With low perfusing pressure (in and out of shock), the kidneys have not been doing a great job of eliminating it. We will have to do that. In addition to improving her blood pressure, we can “push potassium into the cells” with insulin and 50% dextrose. We can help dispose of it with exchange resins, and we can neutralize it with IV calcium. Hemodialysis is the ultimate weapon.

Question 44

An elderly alcoholic, diabetic man, with marginal renal function, sustains multiple trauma while driving under the influence of alcohol. In the course of his resuscitation and multiple surgeries, he is in and out of shock for prolonged periods of time. Blood gases show a pH of 7.1 and Pco2 of 36. His serum electrolytes are sodium 138, chloride 98, and bicarbonate 15.

Answer 44

This man has every reason to develop metabolic acidosis, and he will do so by retention of fixed acids (rather than by loss of bicarbonate). The main driving force in this case is the state of shock, with lactic acid production; but the diabetes, alcohol, and bad kidney are also contributing. The lab shows that indeed he has metabolic acidosis (low pH and low bicarbonate), he is trying to compensate by hyperventilating (low Pco2), and he shows the classic anion gap (the sum of his chloride and bicarbonate is 25 mEq shy of the serum sodium concentration— instead of the normal 10 to 15).
As for the therapy, the classic treatment for metabolic acidosis is either bicarbonate or bicarbonate precursors, like lactate or acetate. But in cases like this, reliance o such therapy tends to eventually produce alkalosis once the low flow state is corrected. Thus the emphasis here should be in fluid resuscitation. However, the choice of fluid is critical: a lot of saline would not be a good idea (too much chloride). A lot of Ringer lactate would be a better choice.

Question 45

A patient who has had a subtotal gastrectomy for cancer, with a Billroth 2 reconstruction, develops a “blowout” of the duodenal stump, and a subsequent duodenal fistula. For the past 10 days he has been draining 750 to 1,500 ml/d of green fluid. His serum electrolytes show a sodium of 132, a chloride of 104, and a bicarbonate of 15. The pH in his blood is 7.2, with a Pco2 of 35.

Answer 45

Again, metabolic acidosis, but now with a normal anion gap. He has been losing lots of bicarbonate out of the fistula. The problem would not have developed if his IV fluid replacement had contained lots of bicarbonate (or lactate, or acetate), but the use of those agents is indicated now for the therapy of the existing abnormality.

Question 46

A patient with severe peptic ulcer disease develops pyloric obstruction and has protracted vomiting of clear gastric contents (i.e., without bile) for several days. His serum electrolytes show sodium of 134, chloride 82, potassium 2.9, and bicarbonate 34.

Answer 46

The classic hypochloremic, hypokalemic, metabolic alkalosis secondary to loss of acid gastric juice. This man needs to be rehydrated (choose saline rather than Ringer actate), and he needs lots of potassium chloride (10 mEq/h will give him plenty, and will be a safe rate). Very rarely is ammonium chloride (or diluted, buffered hydrochloric acid) needed.