Chapter 3 - Pre-Op and Post-Op Care Flashcards
Ejection fraction under ___% (normal is 55%) poses prohibitive cardiac risk for non-cardiac operations. Incidence of perioperative MI is very high, with mortality for such an event between ___%.
35; 55-90
___, which dates from 1977, is no longer the preferred method of assessing cardiac risk. What is more commonly used now?
Goldman’s index of cardiac risk; functional status based on the ability to cope with life’s demands
While Goldman’s index of cardiac risk is no longer the preferred method of assessing cardiac risk, it remains useful for listing all the findings that predict trouble - list them in descending order of importance.
JVD Recent MI PVCs or any rhythm other than sinus >70 y/o Emergency surgery Aortic valvular stenosis Poor medical condition Surgery within the chest or abdomen
JVD, which indicates the presence of ___, is the worst single finding predicting high cardiac risk. If at all possible, treatment with what medications should precede surgery?
CHF; ACEIs, beta-blockers, digitalis, and diuretics
Recent transmural or subendocardial MI is the next worst predictor of cardiac complications. Operative mortality within 3 months of the infarct is ___%, but drops to ___% after 6 months. Thus, deferring surgery until then is the best course of action. If surgery is imperative sooner, what should be done?
40; 6; admission to the ICU the day before to “optimize cardiac variables”
What is the most common cause of increased pulmonary risk and why?
Smoking; compromised ventilation (high PCO2, low FEV1) NOT compromised oxygenation
What factors should lead to evaluation of pulmonary risk before surgery? What evaluation should be done?
Smoking history; presence of COPD
Start with FEV1 - if abnormal, follow with blood gases.
What should be done to mitigate pulmonary risk before surgery?
Cessation of smoking for 8 weeks and intensive respiratory therapy (PT, expectorants, IS, humidified air)
Two clinical findings and three lab values are used to predict operative mortality in patients with liver disease - what are they?
Encephalopathy and ascites; serum albumin, prothrombin time (INR), and bilirubin (only as it reflects hepatocyte function)
What is the current favorite system for predicting operative mortality in patients with liver disease and how is it stratified?
Child class
Class A - 10% mortality
Class B- 30% mortality
Class C - 80% mortality
Severe nutritional depletion is identified by what clinical factors?
Loss of 20% of body weight over a couple of months
Serum albumin <3
Anergy to skin antigens
Serum transferrin level<200 mg/dL
Discuss operative risk and pre-op support in the setting of severe nutritional depletion.
Operative risk is multiplied manyfold. As few as 4 or 5 days of pre-op nutritional support (preferably via the gut) can make a big difference. 7-10 days would be optimal if surgery can be deferred that long.
Diabetic coma is an absolute contraindication to surgery - what must be done before surgery?
Rehydration, return of urinary output, at least partial correction of the acidosis and hyperglycemia
If the indication for surgery is a septic process, complete correction of all variables will be impossible as long as the septic process is present.
Timing of onset of malignant hyperthermia in the setting of surgery? Presentation?
Develops shortly after the onset of the anesthetic (halothane or succinylcholine)
Temp >104 F
Metabolic acidosis and hypercalcemia may occur
Possible family Hx
Rx malignant hyperthermia?
IV dantrolene 100% oxygen Correction of acidosis Cooling blankets Watch for myoglobinuria
Timing of onset of fever 2/2 bacteremia in the setting of surgery? Presentation?
Seen within 30-45 minutes of invasive procedures (instrumentation of the urinary tract is classic)
Chills and temp spikes to 104+ F
Manage bacteremia s/p surgery?
Blood cultures 3x, start empiric ABX
Although rare, severe wound pain and very high fever within hours of surgery should alert you to the possibility of ___ in the surgical wound.
Gas gangrene
Post-operative fever in the usual range (___ F) is caused sequentially in time by what 6 complications?
101-103; atelectasis -> pneumonia -> UTI -> deep vein thrombophlebitis -> wound infection -> deep abscesses
What is the most common source of post-op fever on the first PO day?
Atelectasis
Management of suspected atelectasis post-op?
Rule out the other causes of fever, listen to the lungs, do a CXR, improve ventilation (deep breathing and coughing, postural drainage, IS)
Ultimate therapy if needed is bronchoscopy
Pneumonia will happen in about ___ days if atelectasis does not resolve. Presentation and management?
3; fever will persist, CXR will show infiltrates. Sputum Cx, Rx with ABX
UTI typically produces fever starting on POD ___. Work-up and Rx?
3; UA and UCx. Rx with ABX
Deep thrombophlebitis typically produces fever starting on POD ___ or thereabouts. Work-up and Rx?
5; Doppler studies of deep leg and pelvic veins is the best diagnostic modality (exam is worthless); anticoagulate with heparin, transition to warfarin
Wound infection typically begins to produce fever on POD ___. Presentation and management?
7; erythema, warmth, and tenderness on exam. Rx with ABX ONLY if there is cellulitis. Otherwise, open and drain the wound if an abscess is present.
When these two cannot be easily distinguished clinically, sonogram is diagnostic.
Deep abscesses (in what 3 locations?) start producing fever around POD ___. Dx and Rx?
Subphrenic, pelvic, subhepatic; 10-15; CT scan of the appropriate body cavity is diagnostic. Percutaneous radiologically guided drainage is therapeutic
Perioperative MI may occur during the operation, triggered most commonly by ___, in which case it is detected by the EKG monitor (ST depression, T-wave flattening). When it happens post-op, it is typically within the first ___ post-op days. Presentation?
Hypotension; 2-3; chest pain in only 1/3 of cases. Otherwise, presents as complications
Dx post-op MI? Rx?
Most reliable diagnostic test is troponin; Rx complications. Clot busters cannot be used perioperatively, but emergency angioplasty and coronary stent may be used.
Pulmonary embolus typically happens around POD ___ in elderly and/or immobilized patients. Presentation?
7; sudden onset pleuritic chest pain with dyspnea. Anxious, diaphoretic, tachycardic, with prominent distended veins in the neck and forehead (CVP virtually excludes the diagnosis).
Dx post-op PE? Rx?
Standard test is a spiral CT with IV dye (CT angio); Rx with heparinization. Add an IVC filter (Greenfield) if PEs recur during anticoagulation or if anticoagulation is contraindicated.
Prevention of thromboembolism will prevent PE. How is this done?
Sequential compression devices can be used on anyone who does not have a lower extremity fracture.
High risk patients need anticoagulation. Risk factors include age >40, pelvic or leg fractures, venous injury, femoral venous cath, anticipated prolonged immobilization
Aspiration is a distinct hazard in awake intubations in combative patients with a full stomach. It can be lethal right away or lead to chemical injury of the tracheobronchial tree and subsequent pulmonary failure or secondary pneumonia. Prevention and Rx?
Prevent - NPO, antacids before induction
Rx - lavage and removal of acid and particulate matter with the help of bronchoscopy, followed by bronchodilators and respiratory support
___ can develop in patients with traumatic lungs (recent blunt trauma with punctures by broken ribs) once they are subjected to positive-pressure breathing. Presentation?
Intraoperartive tension PT; they become progressively difficult to “bag,” BP steadily declines, and CVP steadily rises
Rx intraoperative tension PT?
If the abdomen is open, quick decompression can be achieved through the diaphragm. If not, a needle can be inserted through the anterior chest wall into the pleural space (sneaking in under the drapes). Formal chest tube has to be placed later.
___ is the first thing that has to be suspected when a post-op patient gets confused and disoriented. It may be secondary to sepsis. Check ___ and provide ___ support.
Hypoxia; blood gases; respiratory
___ is seen in patients with a stormy, complicated post-op course, often complicated by sepsis as the precipitating event. Presentation?
ARDS; bilateral pulmonary infiltrates and hypoxia with no evidence of CHF
Centerpiece Rx of ARDS? Additional management?
Positive end-expiratory pressure (PEEP); must take care not to use excessive volume, which can lead to barotrauma
Source of sepsis must be sought and corrected
ECMO is becoming the new standard of care for ARDS refractory to PEEP -> main complication is intracranial bleeding, which can be minimized by using a venovenous connection to hook up the patient to the machine
___ is very common in the alcoholic whose drinking is suddenly interrupted by surgery. Presentation?
Delirium tremens; 2nd or 3rd POD, confusion, hallucinations, combative
Rx DT?
IV benzos (standard therapy); alcohol is also effective (IV 5% alcohol in 5% dextrose)…
Hyponatremia, if quickly induced by liberal administration of sodium-free IV fluids (like D5W) in a post-op patient with high levels of ADH (triggered by the response to trauma), will produce confusion, convulsions, and eventually coma and often death (“water intoxication”). Management?
Chart review confirms large fluid intake, quick weight gain, and rapidly lowering serum sodium concentration (in a matter of hours); best prevented by including sodium in the IV fluids. Once it happens, therapy is controversial and mortality is very high (young women are particularly vulnerable). Most authors use small amounts of hypertonic saline (aliquots of 100 mL of 5%, or 500 mL of 3%), perhaps add osmotic diuretics.
Hypernatremia can also be a source of confusion, lethargy, and potentially coma - if rapidly induced by large, unreplaced water loss. Surgical damage to the posterior pituitary with unrecognized diabetes insipidus is a good example. Unrecognized osmotic diuresis can also do it. Management?
Chart review will show large, unreplaced urinary output, rapid weight loss, and rapidly rising serum concentration. Rapid replacement of the fluid deficit is needed, but to “cushion” the impact on tonicity many prefer to use D51/2 or D51/3 NS rather than D5W.
___ is a common source of comma in the cirrhotic patient with bleeding esophageal varices who undergoes a portocaval shunt.
Ammonium intoxication
Post-op urinary retention is extremely common, particularly after surgery in the lower abdomen, pelvis, perineum, or groin. Presentation?
Patient feels the need to void but cannot do it
Management of post-op urinary retention?
In-and-out bladder cath should be done at 6 hours post-op if no spontaneous voiding has occurred
Indwelling (Foley) catheter is indicated at the second (some say third) consecutive cath
Zero urinary output is typically caused by?
A mechanical problem, rather than a biologic one. Look for a plugged or kinked catheter.
Low urinary output (<0.5 mL/kg/hr) in the presence of normal perfusing pressure (i.e., not because of shock) represents either ___ or ___.
Fluid deficit; acute renal failure
Dx cause of low urinary output?
Low-tech: fluid challenge -> bolus 500 mL of IV fluid over 10-20 minutes. Dehydrated patients will respond with a temporary increase in urinary output, those in renal failure to not.
More elegant way: measure urinary sodium -> <10 or 20 in dehydrated patient with good kidneys, >40 mEq/L in renal failure
Can also do FENa (>1 in renal failure)
Paralytic ileus is to be expected in the first few days after abdominal surgery. Presentation?
Bowel sounds are absent, no passage of gas. May be mild distention, but there is no pain.
What prolongs paralytic ileus?
Hypokalemia
Early mechanical bowel obstruction because of ___ can happen during the post-op period. What was probably assumed to be paralytic ileus not resolving after 5, 6, or 7 days is most likely an early mechanical bowel obstruction. Imaging findings? Rx?
Adhesions; X-rays will show dilated loops of small bowel and air-fluid levels. Dx confirmed with abdominal CT demonstrating a transition point between proximal dilated bowel and distal collapsed bowel at the site of obstruction
Surgical intervention
What is Ogilvie syndrome?
Poorly understood but very common condition that could be described as “paralytic ileus of the colon”
Classic presentation of Ogilvie syndrome?
Does NOT follow abdominal surgery; classically seen in elderly sedentary patients (Alzheimer, nursing home) who have become further immobilized owing to surgery elsewhere (broken hip, prostatic surgery)
Develop large abdominal distension (tense but not tender)
Dx and Rx Ogilvie syndrome?
Imaging shows a massively dilated colon
Fluid and electrolyte correction
Colonoscopy, suck out the air, place a long rectal tube
IV neostigmine can theoretically be used to Rx Ogilvie syndrome, as it stimulates colonic motility. However, this drug is best avoided - why?
Lots of side effects, lethal if inadvertently given to someone whose colon is actually obstructed
If you look at vertical sections of a CT scan of the abdomen that shows dilated bowel, how can you tell if you are looking at small bowel or colon? There are three clues.
- Location - the colon hugs the outside boundaries of the image, while the small bowel tends to be in the center of it
- Size - make a circle with your index finger and thumb, and hold it right in front of your face. That is about as big as small bowel can get. Now make a circle with both hands, with index touching index, and thumb touching thumb - the colon can attain that size.
- Fine details - edges of the colon have small indentations (haustral markings), whereas the small bowel has little lines going across (“stacked coins”)
What are air fluid levels?
Everyone has air and fluid in the GI tract. But the churning motion of normal peristalsis makes a foam out of those. If the small bowel is obstructed, it eventually gets tired of trying to push the stuff, so that the liquid goes to the bottom and the air stays at the top. A horizontal line divides these, which can be seen in images taken with the patient in the upright position.
Wound dehiscence is typically seen around the ___ post-op day after open laparotomy. How does the wound appear?
5; the wound looks intact, but large amounts of pink, “salmon-colored” fluid are noted to be soaking the dressings (it is peritoneal fluid).
Manage wound dehiscence?
Wound has to be taped securely, abdomen bound, mobilization and coughing done with great care, while arrangements are made for prompt reoperation to prevent evisceration now or ventral hernia later
What is evisceration?
Catastrophic complication of wound dehiscence, where the skin itself opens up and the abdominal contents rush out. It typically happens when the patient (who may not have been recognized as having a dehiscence) coughs, strains, or gets out of bed. The patient must be kept in bed, and the bowel be covered with large sterile dressings soaked with warm saline. Emergency abdominal closure is required.
How are fistulas of the GI tract recognized?
Because bowel contents leak out through a wound or drain site
Why are fistulas of the GI tract harmful to the patient?
If they do not empty directly and completely to the outside, but leak into a “cesspool” that then leaks out, the problem will be sepsis (requiring complete drainage).
If they drain freely (patient is afebrile, no signs of peritoneal irritation), there are three potential problems - fluid and electrolyte loss, nutritional depletion and erosion and digestion of the belly wall.
Problems with GI tract fistulas are related to the location and volume of the fistula - explain.
Non-existent in the distal colon
Present but manageable in low-volume (up to 200-300 mL/day) high GI fistulas (stomach, duodenum, upper jejunum)
Daunting in high-volume (several liters/day) fistulas high in the GI tract
Management of GI tract fistulas?
Fluid and electrolyte replacement Nutritional support (preferably elemental diets delivered beyond the fistula) Compulsive protection of the abdominal wall (suction tubes, "ostomy" bags)
These things are done to keep the patient alive until nature heals the fistula
What factors can interfere with GI tract fistula healing?
Foreign bodies, epithelialization, tumor, infection, irradiated tissue, IBD, distal obstruction, steroids
In principle, ___ fluids are the equivalent of what a patient would have eaten and drunk if they were not sick. In practice, we include only 3 things for a few days - what are they?
Maintenance; water, sodium, potassium
Plain water cannot be infused - why not?
It would lyse the RBCs
To make IVF isotonic and safe, what is done?
Add dextrose at 5% concentration (D5W)
A standard adult would receive an infusion of about ___ of D5W a day, which does double duty, because it also minimizes the protein breakdown of complete starvation.
2-3 L
For sodium and potassium, what is the key amount to remember for IV fluids?
~100 mEq/day of each
Note - absent CHF or liver disease, we have enormous flexibility with sodium. It should not be zero and should not exceed a few hundred milliequivalents, but anything between 50-250 is fair game. Precision is not required.
Normal saline has ___ mEq/L of sodium, and 5% dextrose in one-half normal saline is often used as the vehicle for sodium.
154
For potassium, the guiding principle is to link the dose to caloric intake. TPN would require more than 100 mEq/day, but for just a few days of semi-starvation, ___/day suffices. We typically use ampules of potassium chloride as the source.
40-60
The most common maintenance IV fluid order reads: “___.”
“Dextrose 5% in 1/2 NS, with 20 milliequivalents of potassium chloride per L, to run in at 125 cc/hr (aka D51/2 NS with 20 mEq of KCl/L, to run in at 125 cc/hr)
What is the purpose of replacement fluids?
Replacement of abnormal fluid losses that have been measured and require infusion, cc per cc, of an appropriate fluid.
Most common causes leading to the need for replacement fluids?
From the GI tract -> vomiting, NG tube output, fistulas, massive diarrhea, malfunctioning ileostomies, etc.
How should replacement fluids be calculated?
If the aggregate loss is a small fraction of a patient’s basic, maintenance volume, we can replace today what was recorded yesterday, then provide tomorrow what we measured today, and so on. But if the abnormal losses approach or exceed half of daily basic needs, more frequent replacement is prudent - every 8 hours or even every 4.
How should the composition of replacement fluids be determined?
It should mimic what was lost
GI fluids are isotonic with plasma and rich in potassium
Fluids from beyond the pylorus are alkaline - replacement fluid?
LR with a little additional KCl (10-20 mEq/L), plus 5% dextrose
Pure gastric juice is very acidic - replacement fluid?
Half-normal saline with a little more potassium (20-40 mEq/L), plus 5% dextrose
Hypernatremia invariably means that the patient has lost water (or other hypotonic fluids) and has developed hypertonicity. Every ___ that the serum sodium concentration is above 140 represents roughly ___ of water lost.
3 mEq/L; 1 L
If hypernatremia develops slowly over several days, the brain will adapt and the only clinical manifestations will be those of ___. Therapy requires volume repletion, but it must be done so that the volume is corrected rapidly (in a matter of hours), while the tonicity is only gently “nudged” in the right direction (and goes back to normal in a matter of days). How is this achieved?
Volume depletion; D51/2 NS (rather than D5W)
Hypernatremia of rapid development (such as in osmotic diuresis or DI) will produce CNS symptoms and correction can safely be done with what type of fluid?
More diluted fluid (D5 1/3 NS or even D5W).
Hyponatremia means that water has been retained and hypotonicity has developed, but there are two different scenarios - what are they?
- Patient who starts with normal fluid volume and adds to it by retaining water because of the presence of inappropriate amounts of ADH (for instance, post-op water intoxication or inappropriate ADH secreted by tumors)
- Patient who is losing large amounts of isotonic fluids (typically from the GI tract) is forced to retain water if he has not received appropriate replacement with isotonic fluids
Rapidly developing hyponatremia produces CNS symptoms and requires careful use of what fluids?
Hypertonic saline (3% or 5%).
In slowly developing hyponatremia from inappropriate ADH, the brain has time to adapt and therapy should be ___.
Water restriction
In the case of the hypovolemic, dehydrated patient losing GI fluids and forced to retain water, what should be done to correct this?
Volume restoration with isotonic fluids (NS or LR) for prompt correction of hypovolemia and allowing the body to slowly and safely unload the retained water and return the tonicity to normal
Which fluid should be used in an alkalosis? An acidosis? Normal pH?
Alkalosis - NS
Acidosis and normal pH - LR
Hypokalemia develops slowly over days when potassium is lost from the GI tract or in the urine (because of loop diuretics, or too much aldosterone), and it is not replaced. When does hypokalemia develop rapidly?
When potassium moves into the cells, most notably when DKA is ocrrected
Rx hypokalemia?
K replacement - safe speed limit of IV potassium administration is 10 mEq/hr (which can be exceeded only if you know what you’re doing)
Hyperkalemia will occur slowly if the kidney cannot excrete potassium (renal failure, aldosterone antagonists), and it will occur rapidly if potassium is being dumped from the cells into the blood (crush injuries, dead tissue, acidosis). Rx?
Ultimate therapy - hemodialysis
While waiting for this, we can help by pushing potassium into the cells (50% dextrose and insulin), sucking it out of the GI tract (NG suction, exchange resins), or neutralizing its effect on the cellular membrane (IV Ca2+); the latter provides the quickest protection
Causes of metabolic acidosis?
Excessive production of fixed acids (DKA, lactic acidosis, low-flow states), loss of buffers (loss of bicarbonate-rich fluids from the GI tract), inability of the kidney to eliminate fixed acids (renal failure)
Lab findings in metabolic acidosis?
Blood pH is low (<74)
Serum bicarbonate is low (<25)
Base deficit
Rx metabolic acidosis?
Rx the cause
In all cases of long-standing acidosis of any etiology, renal loss of K+ leads to a deficit that does not become obvious until the acidosis is corrected. Thus, what should be done?
Prepare to replace potassium as part of our therapy
Causes of metabolic alkalosis?
Loss of acid gastric juice or from excessive administration of bicarbonate (or precursors)
Lab findings in metabolic alkalosis?
High blood pH (>7.4)
High serum bicarb (>25)
Base excess
Rx metabolic alkalosis?
In most cases, an abundant intake of KCl (5-10 mEq/hr) will allow the kidney to correct the problem; only rarely is ammonium chloride or 0.1 N HCl needed
Cost and indications of plain X-ray?
$20
Widely available
Several limitations:
- Cannot penetrate the skull
- Use ionizing radiation
- Superimpose the densities of all the tissues they go through
- Can only see black, white, and a few shades of gray
Useful for broken or dislocated bones and chest x-rays
Cost and indications of sonogram?
$150
Best interface of solid and liquid (perfect for gallstones, urinary tract obstruction; echocardiogram is standard way to assess morphology of the heart)
Very safe, no injection, no radiation
Enemy of sonograms is air
Limitations:
- Cannot go through bones
- Operator dependent (to conduct and read)
Cost and indication of CT?
$350
Glorified X-rays - same basic ionizing radiation, many different angles compiled by a computer
Can penetrate the skull
Black, white, hundreds of shades of grey,
Used for head trauma, cervical spine, abdomen, kidney stones, many other applications
Cost and indication of MRI?
$1500
Much more expensive, less widely available
Increased detail
First choice for looking at soft, mushy targets - spinal cord, brain tumors, structures inside the knee, herniated discs, soft tissue sarcomas
Not useful to guide interventional studies because any ferrous metal in the vicinity will go flying
Cost and indication of PET scan?
$6500
Metabolic activity
Used primarily in the work-up of lung cancer, to determine whether enlarged mediastinal nodes are old scars from back when the patient dug tunnels for a living or mets rapidly growing
