Page 1527 - Hall et al (2015) Principles of Critical Care-McGraw-Hill

1046 PART 10: The Surgical Patient

CHAPTER Special Considerations CONSIDERATIONS IN CRITICALLY ILL
SURGICAL PATIENTS
110 in the Surgical Patient ■
THE ENDOCRINE RESPONSE
Aziz S. Alali The glucagon and insulin response to injury can lead to major changes
Andrew J. Baker in glucose metabolism. Hyperglycemia may occur in a patient who has
Jameel Ali previously demonstrated no evidence of abnormality in glucose levels.
This situation may also unmask a latent diabetic state in some patients,
as well as complicating the management of already established diabetes
KEY POINTS
mellitus in the critically ill surgical patient. Close monitoring of blood
• The biologic response to surgery results in fluid, electrolyte, and glucose, ketones, electrolytes, and acid-base status is essential for proper
systemic hormonal changes that must be considered in the ICU management of the surgical patient. Although strict glycemic control
management of the surgical patient. has been shown to significantly increase the risk of hypoglycemia and
• Nutritional support of the critically ill surgical patient must involve conferred no overall mortality benefit among the critically ill popula-
consideration of the effect of surgical stress on nitrogen balance tion in general, this therapy may be beneficial in patients admitted to a
and on insulin and blood glucose levels. surgical ICU after elective procedures; this has not been confirmed by
• The hypercoagulable state that follows surgery warrants consid- studies adequately examining this subgroup. 13,14
eration of prophylaxis against thromboembolic complications,
particularly in the ICU patient. ■ ANTIDIURETIC HORMONE AND ALDOSTERONE
• Prompt surgical control of the source of the pathology remains the Blood loss, pain related to surgical incisions, fasting prior to surgery,
most important goal in either bleeding or septic critically ill patients. nausea or vomiting, and various drug administrations are only a few of
• Surgery increases the demand on the cardiorespiratory system and the factors that predispose the surgical patient to release of ADH and
the likelihood that temporary mechanical ventilatory assistance aldosterone. The resulting sodium and water retention make it very dif-
will be needed. ficult to monitor the state of hydration of the patient by relying entirely
• Pulmonary edema and atelectasis characterize perioperative respi- on urine volumes, since these hormones tend to decrease urine output
ratory failure; hypoventilation and aspiration also contribute. in spite of normovolemia. Other indices of adequacy of perfusion, such
• Where possible, a reduction of pulmonary capillary hydrostatic as level of consciousness, capillary return, skin warmth, pulse, and blood
pressure in the perioperative period improves gas exchange by pressure need to be assessed. In addition, the syndrome of inappropriate
decreasing lung water. ADH release (SIADH) is relatively common in the postoperative period,
• The concept of closing volume and its relationship to functional resid- placing patients at risk of water intoxication and severe hyponatremia
when even modest water loads are administered. These problems can be
ual capacity is important in understanding perioperative atelectasis. largely avoided if treatment is guided by frequent routine monitoring of
• Risk factors for perioperative atelectasis include obesity, smoking, electrolytes and fluid volume status.
advanced age, anesthesia, recumbence, and incisional pain.
• Diaphragmatic dysfunction is a major component of perioperative ■
respiratory failure. THIRD-SPACE FLUID SEQUESTRATION
• Preoperative assessment of respiratory function makes it possible to Following surgical trauma, occult fluid loss may occur at several sites,
predict operative risk and to correct abnormalities before operation, including the area of injury, where extravascular fluid may accumulate
particularly in the patient undergoing lung resection. in the interstitial and intracellular spaces, 15,16 as well as in the retroperi-
• Early ambulation, physiotherapy, treatment of sepsis and shock, toneal space during intra-abdominal manipulation. In addition, opera-
adequate analgesia, and early operative stabilization of fractures tions involving the gastrointestinal (GI) tract or abnormalities resulting
are key elements in the treatment and prevention of perioperative from surgical diseases such as peritonitis may result in decreased motil-
respiratory failure. ity of the gut and sequestration of large volumes of fluid within the gut
lumen, the gut wall, and the entire large surface area of the peritoneal
cavity. This type of fluid depletes circulating blood volume and is not
easily measured by most available clinical methods. In the patient with
The critically ill surgical patient is at risk for developing all of the compromised cardiorespiratory reserve, close titration of fluid balance
potential problems that afflict nonsurgical patients in the intensive care is crucial. In such patients, central hemodynamic monitoring may be
unit (ICU). In addition, there are factors unique to the surgical patients required in addition to other clinical indices of normal perfusion and
that warrant special consideration if management is to be appropriately volume status.
directed in the ICU environment.
aimed at preserving the milieu intérieur. This response includes the ■ HYPERCOAGULABLE STATE
Surgical stress or injury stimulates an orchestrated biologic response
1-4
elaboration of adrenocortical hormones, catecholamines, and glucagon; The hypercoagulable state resulting from surgical trauma necessitates
a decrease in insulin release resulting in hyperglycemia; and the secre- the institution of either pharmacological and/or mechanical thrombo-
tion of antidiuretic hormone (ADH) and aldosterone, as well as the prophylaxis depending on the individual patient risk of bleeding as soon
release of cytokines and the stimulation of a hypercoagulable state. 5-10 as possible, as outlined in other parts of this text. It is important to
8,9
These responses affect the critically ill surgical patient in many ways. recognize that virtually every surgical patient is at risk for thromboem-
Acute fluid and electrolyte shifts may occur, the renal response to bolic disease, and some are at extraordinarily high risk. Pharmacological
volume infusion may be altered, and the catabolic response results in a prophylactic regimens pose a minor risk of bleeding, but can be
phase of negative nitrogen balance. 11,12 All these responses vary in employed in most surgical patients.
intensity, depending on the magnitude and duration of the injury, the
hemorrhage and sepsis. The increase in metabolic rate increases oxygen ■ NUTRITION
adequacy of resuscitation, and the presence of complications such as
requirement and consumption. The management implications of these Although there is an early phase of negative nitrogen balance follow-
responses to surgical stress are outlined in the following sections. ing surgical stress, it may be shortened or even aborted by appropriate

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