Intraoperative Management for Patients Receiving Total Parenteral Nutrition

Whether TPN is temporarily discontinued or unchanged during the operative period, the anesthesiologist must monitor blood glucose levels meticulously to avoid hypoglycemia or hyperglycemia. Hyperosomolar, nonketotic, hyperglycemic coma has been reported in patients who fail to regain consciousness after anesthesia. ^{[17] [214] [215]}

Hagerdal and associates^[216] pointed out the effect of even 5% glucose intraoperatively on the RQ seen in the recovery room in patients after anesthesia. They demonstrated a 20% greater DVCO₂ during the first hour in the recovery room in patients who had received 5% dextrose intraoperatively compared with those who had received isotonic saline.

The anesthesiologist should also be meticulous about ensuring the presence of normal serum phosphate levels in the patient receiving TPN. Hypophosphatemia has been associated with several clinical conditions of interest to the anesthesiologist. Newman and colleagues^[217] described two cases of acute respiratory failure associated with hypophosphatemia. These patients, both with a history of alcoholism, developed profound areflexic muscle weakness such that mechanical ventilation became necessary. Serum phosphate levels were 500 and 400 mg/dL. Muscle strength returned quickly after phosphate administration.

Preoperative Anesthetic Considerations

A preoperative check should include the following evaluations ^[218] :

1. Serum sodium, potassium, chloride, and bicarbonate levels
2. Chest radiograph showing the infusion catheter's position
3. Serum phosphate level
4. Serum calcium level
5. Serum magnesium level
6. Urinary phosphate and magnesium levels
7. Blood urea nitrogen and creatinine levels
8. Forced vital capacity
9. Blood and urine glucose levels
10. Blood acid-base status and blood gases
11. Liver function tests
12. RQ (if measured)

Details of the duration and the type of TPN solutions and additives should include the following:

1. Incidence of hyperglycemia or hypoglycemia
2. Addition of insulin to regimen
3. History of chronic alcoholism
4. Presence of sepsis

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5. Central catheter functioning
6. Site for additional intravenous infusion during anesthesia

A decision must be made whether to continue TPN^[219] or to replace TPN by 10% dextrose for the perioperative period.^[220] In either event, special precautions and monitoring are essential. In most instances, it is safer to continue the patient's TPN during the operation, especially with mixed glucose-lipid solutions. The anesthesiologist must remember that the TPN volume is added to the total intravenous intake. It is important to monitor plasma glucose level, potassium level, and pH.

Intraoperative Anesthetic Management

In theory, it is possible to lessen the stress hormone response to surgery by using opioid-based anesthesia or spinal or epidural anesthesia^{[221] [222] [223] [224] [225]} (see Chapter 11 , Chapter 43 , and Chapter 44 ). One study could not demonstrate a consistent reduction in stress response to surgery when regional anesthesia was used.^[226]