Postoperative Evaluation of the Critically Ill Patient

Chapter 144 Postoperative Evaluation of the Critically ill Patient



Elisa Mazzaferro, MS, DVM, PhD, DACVECC



KEY POINTS



• Particular concerns in the postoperative patient are abnormalities of the respiratory, cardiovascular, thermoregulatory, and hematologic systems.

• Hypoventilation, hypoxemia, hypotension, and hypothermia are some of the most common life-threatening abnormalities seen in the postoperative patient.

• Active rewarming is essential in the postoperative patient. Once the animal’s core body temperature has been increased to 99° F, active rewarming efforts should stop, to prevent accidental hyperthermia.


INTRODUCTION


Getting a critical patient through surgery is just one of many hurdles that the clinician and animal will face before discharge from the hospital. During the immediate postsurgical period, careful patient assessment, monitoring, and nursing care can make the difference between life and death. Postoperative patients commonly have multisystem abnormalities as a result of their primary disease processes, surgical insult, and effects of anesthetic agents. Of particular concern are abnormalities of the respiratory, cardiovascular, thermoregulatory, and hematologic systems.



ANESTHETIC RECOVERY



Airway and Breathing


Careful monitoring of the patient’s airway, breathing, oxygenation, and ventilation should continue throughout the postoperative period. If possible, a Wright’s respirometer can be used to assess the animal’s tidal volume (normal 10 to 15 ml/kg). During prolonged anesthesia and recumbency, dependent lung lobes can be atelectatic, causing intrapulmonary shunting of blood. The airway should remain intubated with a cuffed endotracheal tube until the patient can actively swallow and is actively fighting the endotracheal tube. If significant respiratory compromise is evident, it may be prudent to keep the patient intubated and initiate mechanical ventilation rather than place the patient at risk by extubation.


Vomiting or regurgitation of gastric contents is common during the immediate postoperative period. If this occurs, the pharyngeal region and esophagus should be suctioned and the esophagus flushed with sterile saline to prevent aspiration pneumonia and esophagitis. Routine use of antibiotics in animals with potential aspiration pneumonia should be avoided until there is evidence of pneumonia, because empiric antibiotic use can promote development of resistant bacterial organisms in the animal and hospital environment.



Hypoventilation


Anesthetic gases and pain can predispose a patient to hypoventilation. Hypoventilation is identified by elevated partial pressure of carbon dioxide levels on blood gas evaluation. While still intubated, the animal can be assessed noninvasively for hypoventilation with end-tidal carbon dioxide monitoring.1 Hypoventilation most commonly results from increased dead space or inadequate minute ventilation. If hypoventilation is identified, the animal’s respiratory rate and character should be monitored carefully. Apnea, bradypnea, or inadequate tidal volumes may require intermittent positive-pressure ventilation by hand or machine until the patient is able to ventilate effectively unassisted. Anesthetic agents and opioid analgesics can be potent respiratory depressants and can cause hypoventilation during the early postanesthetic recovery period. Excessive apparatus dead space will also cause hypercapnia and is to be avoided. Patients with persistent severe hypercapnia (partial pressure of arterial carbon dioxide >60 mm Hg) despite therapy are candidates for mechanical ventilation.



Hypoxemia


Oxygenating ability must be monitored closely during the postoperative period. If an animal has an arterial catheter, an arterial blood gas analysis with and without supplemental oxygen should be performed to determine arterial oxygenation.2 If an arterial catheter is not available, noninvasive measures of oxygenation such as pulse oximetry should be used until the patient’s oxygen saturation exceeds 95%. If oxygenation is inadequate, supplemental oxygen should be administered by oxygen cage or hood or nasal, nasopharyngeal, or tracheal oxygen catheterization.


Hypoxemia, identified as a partial pressure of arterial oxygen less than 80 mm Hg or an oxygen saturation of less than 95%, is most commonly a result of pulmonary parenchymal disease such as pulmonary edema, pulmonary contusions, pneumonia, atelectasis, or parenchymal dysfunction secondary to pleural space disease. In the patient breathing room air, hypoventilation can cause hypoxemia that will resolve rapidly with oxygen administration. If hypoxemia is identified, it should prompt the clinician to evaluate the patient thoroughly and perform further diagnostic tests as indicated.



CIRCULATORY STATUS



Hypotension


Critical illness and anesthesia are both common causes of hypotension, making intensive blood pressure monitoring essential during the postoperative period. Continuous direct arterial blood pressure monitoring is ideal in the critically ill patient; when it is unavailable, indirect measurement is done with an oscillometric and/or Doppler technique. Hypotension may be caused by hypovolemia, vasodilation, or decreased myocardial contractility. Initial therapy generally is focused on aggressive support of intravascular volume. Measurement of central venous pressure can help guide this therapy. If primary myocardial disease is suspected, echocardiographic evaluation is indicated and positive inotropic drugs such as dobutamine may be required.


Vasodilation is a potent cause of hypotension that is unresponsive to fluid administration. It is most commonly a result of anesthetic drug effects and/or a severe systemic inflammatory response during the postoperative period. Vasopressor drugs such as dopamine, norepinephrine, and vasopressin are usually required to support blood pressure in these patients.


Bradyarrhythmias and tachyarrhythmias can also cause hypotension and should be treated appropriately. Electrocardiographic monitoring can be very useful in the postoperative patient for early detection of dysrhythmias, as well as identification of tachycardia that can be an early warning sign of cardiovascular compromise, pain, or anxiety.

Related posts:

  1. Deteriorating Mental Status
  2. Hyperthermia and Fever
  3. Ventilator-Associated Lung Injury
  4. Allergic Airway Disease in Dogs and Cats and Feline Bronchopulmonary Disease

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Sep 10, 2016 | Posted by in SMALL ANIMAL | Comments Off on Postoperative Evaluation of the Critically Ill Patient

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