General Surgery

·         Waiting for intubation to be completed before initiation of Defibrillation and chest compression interventions is one of the most common mistakes in advanced life support. Children, in whom primary respiratory arrest is more common, are an exception. Restoration of ventilation in children often reveals that pulselessness was severe shock, not cardiac arrest.

·         Colloid advocates claim that the big molecules remain in the intravascular space and are more effective in elevating blood volume. Crystalloid advocates state that capillaries leak albumin, especially in the shock state. Resuscitation with crystalloid is clearly safe. Given its availability, low cost, and safety, crystalloid (lactated Ringer's solution) is the choice for initial fluid resuscitation.

·         Supraventricular origin: when an impulse originates above the AV node, it can access the ventricles only through the AV node to reach the Purkinje system, which conducts and activates the ventricles rapidly, producing a narrow-complex beat (< 2 small boxes on ECG).

Ventricular origin: when an impulse originates from an ectopic site on the ventricle, it takes longer to access the high-speed Purkinje system. A ventricular impulse activates the entire mass, slowly producing a wide-complex beat (> 2 small boxes on ECG).

To distinguish ventricular from supraventricular tachycardia, transiently block AV node with adenosine IVP. If ventricular complex persists, it is ventricular tachycardia; if the complex stops, it is supraventricular tachycardia.

·         INTRA-AORTIC BALLOON PUMP

1. Indicated for cardiogenic shock refractory to pharmacologic manipulation.
2. Triggered by QRS complex of surface ECG; inflates during diastole (T wave) and deflates on systole (R wave or at dicrotic notch on aortic pressure curve).
3. 80% of coronary blood flow occurs during diastole.
4. Mechanistically results in diastolic augmentation and systolic unloading (afterload reduction).

·         A healthy medical student expends about 3% of total oxygen consumption (energy use) on work of breathing. After injury, particularly a big burn, patients may increase fractional energy expenditure of breathing to 20% of their total energy use.

·         Intuitively an extremity incision or injury influences vital capacity least, followed sequentially by a lower abdominal incision, median sternotomy, thoracotomy, and upper abdominal incision. An upper abdominal incision is worse than a thoracotomy!

·         To make the diagnosis of ARDS, the PCWP must be <18 mmHg. Pure ARDS exists only if the PCWP is > 4 mmHg less than the COP (22).

·         Lasix sandwich: Many surgeons, give 25 g of albumin followed in 20 minutes by 20 mg of furosemide (Lasix) IV. They reason that the albumin pulls fluid out of the water-logged lung and the Lasix promotes diuresis to rid the patient of extra water. This therapeutic concept probably works only in patients who are not very sick. The sicker the patient, the faster the infused albumin leaks and equilibrates across the damaged endovascular endothelial barrier. Little water is sucked out of the sick lung in preparation for diuresis.

·         Base excess is a poor man's indicator of the metabolic component of acid-base disorders. After correcting the PCO2 to 40 mmHg, the base excess or base deficit is touted as an indirect measure of serum lactate. Although many parameters directing volume resuscitation in shock are more practical and direct, base deficit has been advertised as helpful. The base excess or deficit is calculated from the Sigaard-Anderson nomogram in the blood gas laboratory. Normally, there is no base excess or deficit. Acid-base status is "just right."

·         ION CONCENTRATIONS IN CRYSTALLOID SOLUTIONS:

1. ½ NS or 0.45% NaCl: 77 mEq of Na+, 77 mEq of Cl-
2. NS or 0.9% NaCl: 154 mEq of Na+, 154 mEq of Cl-
3. Hypertonic NS or 7.5% NaCl: 1283 mEq of Na+, 1283 mEq of Cl-
4. Lactated Ringer's: 130 mEq of Na+, 110 mEq of Cl-, 38 mEq of lactate, 4 mEq of K+, and 3 mEq Ca+

·         Minimal adequate postoperative urine output: 0.5 mL/kg/h.

·         Postoperative urine sodium: < 20 mEq/L, because surgical stress prompts mineralocorticoid (aldosterone) secretion so that the normal kidney retains sodium.

·         Polymeric enteral feedings are soy-based, lactose-free products that contain intact protein, carbohydrates, and fat. Most offer 1 kcal/mL and 37-62 g of protein per liter. Some have additional insoluble or soluble fiber. Special modifications of the standard formulas include "immune-enhancing" agents such as fish oil, arginine, glutamine, and nucleotides. "Elemental" formulas contain amino acids, di-, tri- and quatra-peptides, dextrose, and minimal fat. Several concentrated formulas (2 kcal/mL) are available for use in patients with congestive heart failure (CHF), renal failure, and hepatic failure.

·         [24 h UUN (g) + 2 g N insensible losses + 3] x 6.25 = required amount of protein (g)

·         Indirect calorimetry:

It is a bedside test in which the patient's production of carbon dioxide and consumption of oxygen are measured for approximately 30 minutes until steady state is achieved. Results are inserted into the modified Weir equation:

REE = [(3.796 x VO2) + (1.214 x VCO2)] x 1440 min/day

where REE = resting energy expenditure (kcal/day), VO2 = oxygen consumption (L/min), and VCO2 = CO2 exhaled (L/min).

·         Glutamine is the amino acid found in greatest concentration in muscle and plasma; it decreases after surgery and injury and with stress. Thus, it is considered a conditionally essential amino acid. It plays a role as a metabolic substrate for rapidly replicating cells, is thought to maintain the integrity and function of the intestinal barrier, and protects against free radical damage because of its role in maintaining GSH levels.

Glutamine is not included in standard amino acid solutions because of limited solubility and stability; in its dipeptide form bound to alanine or glycine, glutamine is more stable and soluble. Supplementation may reduce infectious complication rates and decrease length of hospital stays in surgical patients.

·         The amount dissolved is calculated by: O2 dissolved = 0.003 x PaO2

 The amount attached to hemoglobin is calculated by: O2 attached = 1.38 x [Hb] x SaO2

·         SVO2 :

1. "Poor man's" estimation of cardic output
2. Decreased SVO2: progressive anemia, cardiac failure, decreasing arterial saturation, increased basal metabolic rate
3. Increased SVO2: sepsis, cyanide toxicity, left-to-right intracardiac shunt, left-to-right peripheral shunt, inadvertent wedging of PA catheter

·         Following a major surgery, the body shows stress response resulting in:

· potassium retention

· sodium and water retention

· increased protein breakdown, decreased protein synthesis

· increased gluconeogenesis, increased glycogenolysis and decreased peripheral glucose uptake

· increased lipolysis and decreased lipogenesis