The primary cause of postoperative shivering is perioperative hypothermia, although other, non-thermoregulatory, mechanisms may be involved. Postoperative shivering can greatly increase oxygen consumption, catecholamine release, cardiac out-put, heart rate and blood pressure, and intracerebral and intraocular pressure. It increases cardiovas-cular morbidity, especially in elderly patients, and increases length of stay in the postanesthesia care unit. Shivering is uncommon in elderly and hypoxic patients: the efficacy of thermoregulation decreases with aging, and hypoxia can directly inhibit shiver-ing. Many drugs, notably meperidine, clonidine, and tramadol, can be used to reduce postoperative shiv-ering; however, prevention of hypothermia is the most efficient strategy.
Pharmacological treatment of PONV should be promptly initiated once medical or surgical causes of PONV have been ruled out. PONV and its treat-ment are reviewed.
The scientific rationale for multimodal analgesia is to combine different classes ofmedications, having different (multimodal) phar-macological mechanisms of action and additive or synergistic effects, to control multiple periopera-tive pathophysiological factors that lead to postop-erative pain and its sequelae. Such an approach may achieve desired analgesic effects while reduc-ing analgesic dosage and associated side effects, and often includes utilization of regional analgesic techniques such as local anesthetic wound infu-sion, epidural or intrathecal analgesia, or single-shot or continuous peripheral nerve blockade. Multimodal analgesia is routinely utilized in ERPs to improve postoperative outcomes. Discus-sion here focuses on the principal analgesicinterventions that can be used in perioperative multimodal analgesia regimens.
Perioperative administration of cyclooxygen-ase-2 (COX-2) inhibitors likewise reduces postop-erative pain and decreases both opioid consumption and opioid-related side effects, and while their use has reduced the incidence of NSAID-related plate-let dysfunction and gastrointestinal bleeding, the adverse effects of COX-2 inhibitors on kidney func-tion remain controversial. Concerns have also been raised regarding their safety for patients undergoing cardiovascular surgery; these have centered on rofe-coxib and valdecoxib, specifically. Increased cardio-vascular risk associated with the perioperative use of celecoxib or valdecoxib in patients with minimal cardiovascular risk factors and undergoing nonvas-cular surgery has not been proven. Further studies are needed to establish the analgesic efficacy and safety of COX-2 inhibitors and their clinical effect on postoperative outcomes.
High thoracic epidural analgesia has been intro-duced in patients undergoing cardiac surgery based on data from small randomized clinical trials that suggested benef cial effects on postoperative outcomes. A recent meta-analysis of more than 2700 patients who underwent cardiac surgery and received high thoracic epidural analgesia showed an overall reduction of pulmonary complications (rela-tive risk 0.53) and supraventricular arrhythmias (relative risk 0.68), but no reduction in incidence of myocardial infarction, stroke, or postoperative mortality. Due to concerns about the risk of epidural hematoma and its devastating neurological conse-quences in patients fully heparinized during cardio-pulmonary bypass, the use of high thoracic epidural analgesia is understandably limited.
Local anesthetic wound infusion—The analgesicefficacy of local anesthetic wound infusion has been established for multiple surgical procedures. Incon-sistent results may be due to factors that include type, concentration, and dose of local anesthetic, catheter placement technique and type of catheter, mode of local anesthetic delivery, incision location, and dis-lodgment of the catheter during patient mobilization.
The multidisciplinary aspect of postoperative care should bring together the surgeon, the nurse, the anesthesiologist, the nutritionist, and the physio-therapist in an effort to customize individual patient care based on standardized, procedure-specific protocols. Comfortable chairs and walkers need to be made readily available near each patient bed to encourage patients to sit, stand, and walk. The ben-efits of mobilization for cardiovascular homeostasis and bowel function have been shown repeatedly. Patients should be encouraged to sit the evening fol-lowing surgery, with ambulation starting the next day for a minimum of 4–6 h each day. If patients cannot get out of bed, they should be encouraged to perform physical and deep breathing exercises.
well-organized, well-trained, highly motivated acute pain service (APS) and surgical nursing work-force, utilizing procedure-specific clinical proto-cols to optimally manage analgesia and related side effects, is critically important for fast-track surgery. The quality of pain relief and symptom control heav-ily influences postoperative recovery; optimal mobi-lization and dietary intake depend upon adequate analgesia. The anesthesiologist, in coordination with the APS, must identify and employ the optimal analgesic techniques tailored to the specific surgical procedure, and the quality of analgesia and possible presence of side effects must be closely and con-tinuously assessed. The patient must be comfortable ambulating and performing physiotherapy, with minimal side effects such as lightheadedness, seda-tion, nausea and vomiting, and leg weakness.
Postoperative ileus delays enteral feeding, causes patient discomfort, and is one of the most common causes of prolonged postopera-tive hospital stay. Because early enteral nutrition is associated with decreased postoperative morbidity, interventions and strategies aimed at decreasing postoperative ileus are required for patients in an ERP. Three main mechanisms contribute to ileus: sympathetic inhibitory reflexes, local inflamma-tion caused by surgery, and postoperative opioid analgesia. The nasogastric tube, frequently inserted after abdominal surgery, does not speed the recov-ery of bowel function and may increase pulmonary morbidity by increasing the incidence of aspiration. Therefore, nasogastric tubes should be discouraged whenever possible or used for only a very short period of time, even in gastric and hepatic surgery.
Multimodal analgesia and nonopioid analgesia techniques shorten the duration of postoperative ileus. Continuous epidural local anesthetic infu-sion improves the recovery of bowel function by suppressing the inhibitory sympathetic spinal cord reflexes. Thoracic epidural analgesia with local anesthetics and small doses of opioids reduces the incidence of ileus and improves postoperative pain relief. Minimally invasive surgery decreases surgical stress and inflammation, resulting in a faster return of bowel function. Any role of epidural analgesia in accelerating the recovery of bowel function after laparoscopic surgery remains controversial, at best. Laxatives, such as milk of magnesia and bisacodyl, reduce postoperative ileus duration. Prokinetic medications such as metoclopramide are ineffec-tive. Neostigmine increases peristalsis but may also increase the incidence of PONV.
Excessive perioperative fluid administration commonly causes bowel mucosal edema and delays postoperative return of bowel function. However, results from a randomized double-blind study of lib-eral versus restricted fluid administration showed no differences with regard to recovery of bowel function in patients undergoing fast-track abdomi-nal surgery. No studies have compared crystalloid versus colloid administration in terms of their effecton the return of bowel function. Because either excessive, or excessively restricted, perioperative fluid therapy may increase the incidence and severity of postoperative ileus, a goal-directed fluid strategy (discussed earlier) should be selected to decrease postoperative morbidities and enhance recovery and should be utilized according to the type of surgery and patient comorbidities.
Postoperative chewing gum, by stimulating gas-trointestinal reflexes, may decrease ileus duration. Although its effect has not been evaluated in ERP patients, postoperative chewing gum may be included in multimodal interventions to decrease postopera-tive ileus because of its safety and low cost. Peripheral opioid μ-receptor antagonists methylnaltrexone and alvimopan have been introduced to minimize the adverse effects of opioids on bowel function without antagonizing opioid analgesia. In patients receiving large-dose intravenous morphine analgesia, alvimo-pan decreases the duration of postoperative ileus by 16–18 h, the incidence of nasogastric tube reinser-tion, postoperative morbidity, and hospital length of stay and readmission rates, especially in patients undergoing bowel resection. Nevertheless, the recov-ery of bowel function is slower when compared with patients receiving multimodal strategies in an ERP.