Chapter 87

• The biologic response to surgery results in fluid, electrolyte, and systemic hormonal changes that must be considered in the ICU management of the surgical patient.
• Nutritional support of the critically ill surgical patient must involve consideration of the effect of surgical stress on nitrogen balance and on insulin and blood glucose levels.
• The hypercoagulable state that follows surgery warrants consideration of prophylaxis against thromboembolic complications, particularly in the ICU patient.
• Timely surgical intervention, and treating and preventing hemorrhage and sepsis are crucial in determining outcome in the critically ill.
• Surgery increases the demand on the cardiorespiratory system and the likelihood that temporary mechanical ventilatory assistance will be needed.
• Pulmonary edema and atelectasis characterize perioperative respiratory failure; hypoventilation and aspiration also contribute.
• Where possible a reduction of pulmonary capillary hydrostatic pressure in the perioperative period improves gas exchange by decreasing lung water.
• The concept of closing volume and its relationship to functional residual capacity is important in understanding perioperative atelectasis.
• Risk factors for perioperative atelectasis include obesity, smoking, advanced age, anesthesia, recumbency, and incisional pain.
• Diaphragmatic dysfunction is a major component of perioperative respiratory failure.
• Preoperative assessment of respiratory function makes it possible to predict operative risk and to correct abnormalities before operation, particularly in the patient undergoing lung resection.
• Early ambulation, physiotherapy, treatment of sepsis and shock, adequate analgesia, and early operative stabilization of fractures are key elements in the treatment and prevention of perioperative respiratory failure.

The critically ill surgical patient is at risk for developing all of the potential problems that afflict nonsurgical patients in the intensive care unit (ICU). In addition, there are factors unique to the surgical patient that warrant special consideration if management is to be appropriately directed in the ICU environment.

Surgical stress or injury stimulates an orchestrated biologic response1–4 aimed at preserving the milieu intérieur. This response includes the elaboration of adrenocortical hormones, catecholamines, and glucagon; a decrease in insulin release resulting in hyperglycemia; and the secretion of antidiuretic hormone (ADH) and aldosterone, as well as the release of cytokines and the stimulation of a hypercoagulable state.5–10 These responses affect the critically ill surgical patient in many ways. Acute fluid and electrolyte shifts may occur, the renal response to volume infusion may be altered, and the catabolic response results in a phase of negative nitrogen balance.11,12 All these responses vary in intensity, depending on the magnitude and duration of the injury, the adequacy of resuscitation, and the presence of complications such as hemorrhage and sepsis. The increase in metabolic rate increases oxygen requirement and consumption. The management implications of these responses to surgical stress are outlined in the following sections.

### The Endocrine Response

The glucagon and insulin response to injury can lead to major changes in glucose metabolism. Hyperglycemia may occur in a patient who has previously demonstrated no evidence of abnormality in glucose levels. This situation may also unmask a ...

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