is necessary to ensure adequate analgesia and patient wellbeing. Pain can be challenging to assess accurately in hospitalized feline patients, as they tend to be quieter and more reserved than canine patients [100, 101].
If a patient is assessed to be in pain, analgesics should be administered as soon as possible. It is not appropriate to withhold analgesia because of concerns about creating cardiovascular or respiratory instability or masking changes in patient status. When titrated doses of cardiovascular sparing analgesics and anxiolytics are used, primary cardiovascular or respiratory depression should not result. Instead, if hypotension or respiratory changes are seen after drug administration, it is more likely that the patient's cardiopulmonary instability was uncovered by relief of pain‐induced tachycardia, tachypnea, and catecholamine release with secondary vasoconstriction [100].
Multimodal analgesia is preferred in many patients, especially those with marked pain, as the complexity of pain pathways often renders single agent therapy ineffective, irrespective of dose escalation [101]. The addition of local analgesics is often beneficial to decrease the systemic dose. The addition of anxiolytics may also be helpful to decrease the stress and agitation associated with hospitalization, recumbency, and activity restriction present in many surgical patients, and therefore decrease systemic analgesic dosing.
Opioids are often the first choice of analgesia in critical veterinary patients as they have rapid onset of action, can be titrated to an individual's needs, are reversible, and are cardiopulmonary sparing medications. They can be used alone or in combination with other analgesics and anxiolytics and administered as a bolus or constant rate infusion (CRI). Common adverse effects include initial excitatory phase, nausea, vomiting, bradycardia, decreased gastrointestinal motility, and respiratory depression at high doses. Cats tend to be more prone to developing an excitatory period, so the dose of opioids in cats is generally half the canine dose. Rapid intravenous administration of morphine or meperidine can cause histamine release, vasodilation, and hypotension. If adverse effects result from opioid administration, naloxone is a pure antagonist for opioid reversal. Naloxone will reverse both the positive and negative effects of opioids, which may result in pain, excitement, and agitation. Fentanyl transdermal patches are effective ways to provide potent analgesia in an outpatient setting, but they can become displaced or ingested, and have the potential for misuse and abuse by owners, including ingestion by small children.
Lidocaine is effective as a local anesthetic and epidural analgesic. It can also be administered as an intravenous CRI, generally combined with an opioid such as morphine or fentanyl, with or without the addition of a ketamine CRI. When given intravenously, it should be used cautiously and titrated carefully in cardiovascularly unstable patients, as it can cause cardiac arrhythmias, tachycardia, and seizures. This is especially true in cats, and some debate exists as to whether this medication should be given intravenously to cats for analgesia.
N‐methyl‐d‐aspartate (NMDA) antagonists such as ketamine are very effective, owing to their multiple sites of action and effects, including analgesia, neuroprotection, and sedation. Ketamine has limited cardiopulmonary depression but can increase cardiac output and myocardial oxygen consumption, and it can cause muscle tremor activity. Controversy exists over its use in patients with head trauma as there is concern that ketamine contributes to increased ICP. It should be used with caution in patients with hypertension and cardiovascular disease. In cats, it is renally excreted so consideration for renal function with use and dose should be given.
Alpha 2 (α2) adrenergic agonists, such as dexmedetomidine, bind central α2 receptors to result in sedation, muscle relaxation, and analgesia. Additional effects include vasoconstriction, reflex bradycardia, and diuresis. Dexmedetomidine should be used cautiously in critically ill patients and should be reserved only for patients without cardiovascular disease or compromise. At low doses (1–5 μg/kg IV), dexmedetomidine is synergistic with opioids for analgesia and can be used as a bolus or CRI. Its effects can be reversed with the α2 receptor antagonist atipamezole. The volume of atipamezole used for reversal is the same volume as the administered dexmedetomidine. Intramuscular administration of atipamezole is preferred to prevent rapid drug reversal, which can cause hypotension or aggression [102–104].
Benzodiazepines are effective for mild sedation and anxiolysis with minimal cardiovascular compromise. They are commonly combined with opioids for analgesia and sedation and can decrease the dose of opioids needed to achieve the desired effect. Midazolam and diazepam can be given intravenously, but only midazolam can be given intramuscularly and is preferred for CRI therapy due to the propylene glycol vehicle of diazepam. Reversal of both agents can be accomplished with intravenous dosing of flumazenil.
Phenothiazines, such as acepromazine, provide no analgesia but are potent anxiolytics in veterinary medicine. They must be used cautiously in cardiovascularly unstable patients as they can cause profound vasodilation and hypotension. They are especially useful in patients with respiratory distress, particularly upper airway obstruction. However, intravenous acepromazine takes approximately 15 minutes to achieve maximal effect, so this delay in onset of action should be anticipated in patients [101]. This is important in patients in respiratory distress, for whom this delay may not be tolerated, and more rapidly acting medications should be selected.
Non‐steroidal anti‐inflammatory drugs (NSAIDs) have a limited role in treating pain and inflammation in many emergency patients, especially those with gastrointestinal and renal disease or cardiovascular compromise. Even NSAIDs that can be administered parenterally should be used with extreme caution in patients with perfusion abnormalities, as they can increase the risk of gastrointestinal ulceration, hepatic insult, and kidney injury. NSAIDs are generally not recommended for cats, unless given as a single dose in healthy, hydrated, and normovolemic cats. An NSAID designed for safer use in cats (robenacoxib) is available, but extensive clinical experience is lacking. However, postoperatively, when perfusion is restored and normalized, many surgical patients benefit from control of inflammation and the analgesia achieved with NSAID therapy.
2 Operating Room Nursing Tips for Emergency Surgical Procedures
Cami Elliott1, Michelle Capps2, and Michael McCallum2
1 Nashville Veterinary Specialists and Animal Emergency, Nashville, TN, USA
2 University of Pennsylvania, School of Veterinary Medicine, Philadelphia, PA, USA
Gastrointestinal System
Most gastrointestinal procedures can be performed with routine instruments, with a few additional items supplied as needed. It may be beneficial to establish a routine soft tissue instrument set, such as the one listed in Box 2.1.
Unless otherwise noted, patients will be placed in dorsal recumbency for gastrointestinal surgeries. It is also of benefit to have a variety of sizes of containers and formalin available for biopsies taken during gastrointestinal surgery.
Esophageal Surgery
A lodged esophageal foreign body is the most common indication for esophageal surgery and the location of the foreign body will determine the approach. The cervical esophagus is exposed through a ventral midline approach and the thoracic esophagus is approached via a lateral thoracotomy. Recommended instruments will depend on the approach chosen and are listed in Box 2.2.
Gastrointestinal Foreign Bodies
When preparing the operating room for a gastric or intestinal foreign body surgery the technician should keep in mind that a gastrotomy, enterotomy, or intestinal resection and anastomosis could be performed. To prepare for these events, consider that preventing the spillage of ingesta into the abdominal cavity is of key concern. Sterile lap sponges, lavage, and suction are crucial in preventing contamination and peritonitis. Portable suction