Contributing factors for PONV.
Reducing the baseline risk
The management of PONV should start with prevention. After identifying patients at a higher risk for PONV, it is important that we first reduce the baseline risk that can lead to PONV. This reduction of risk in mild cases and in patients with a low risk may be sufficient to avoid PONV. These include the following.[34]
1. The use of regional anesthesia when feasible.
2. The use of propofol and TIVA in place of inhalational agents.
3. Avoidance of nitrous oxide.
4. Limiting the use of opioids in the perioperative period and the use of alternate modalities for pain control.
5. Using prophylactic anti-emetics.
6. Adequate perioperative hydration.
Medications and interventions
A clinical decision to initiate anti-emetic measures is dependent on the characteristics of the patient and the clinical scenario. The use of routine anti-emetic prophylaxis is not recommended but should be used only when the patient’s risk is sufficiently high and the benefits of therapy are clear.[34,35] The benefits may be obvious in some situations where vomiting might pose a high medical risk due to the surgical procedure (gastric or esophageal surgery, intraocular procedures), underlying medical condition (increased ICP, IOP) or when the risk of aspiration is high (wired jaws, altered mental status). We need to be aware of the benefits and side effects of the medications as the latter may outweigh their perceived benefits due to associated medical conditions (e.g., prolonged QTc). The patient’s preferences also weigh into the decision process.
Algorithm for PONV management
1. Prophylaxis in low-risk patients (1 risk factor, risk score < 10%): prophylaxis is rarely justified. The risks of treatment (sedation, headache, low BP, QT prolongations, Torsade’s de pointes, etc.) should be weighed against the patient’s preference and medical concerns due to vomiting (e.g., a middle-aged male smoker having a microlaryngoscopy).
2. Moderate-risk patients (2–3 risk factors, risk score 20–40%): consider 1 or 2 anti-emetic drugs or measures (e.g., total intravenous anesthesia [TIVA] with opioid and no other anti-emetic drugs, or 4 mg of dexamethasone and block to minimize opioid consumption). An example is a middle-aged, non-smoking female with no other known risk factors undergoing a laparoscopic gynecologic surgery.
3. High-risk patients (> 3 risk factors, risk score > 60%): consider combination treatment (e.g., regional anesthesia instead of GA, or TIVA with additional anti-emetic).
Treatment guidelines suggest that outpatients should receive longer-acting anti-emetic measures. Different mechanisms of anti-emetic strategies have additive effects. For a more detailed discussion, readers are referred to Chapters 4 and 14.
Postoperative fluid management and hydration
Postoperative hydration status should be optimized prior to discharge from the PACU. This might involve administering IV fluids or blood and blood components. An indirect way to assess the fluid status is to assess urine output. The amount and type of fluids administered will depend on the patient characteristics (age, preoperative blood count, coagulation parameters), intraoperative course (massive fluid shifts, blood loss) and postoperative hemodynamics. Normally the IV crystalloids are continued into the perioperative period until the oral intake is established and no significant nausea and vomiting exists.
Postoperative renal function and urine output
The current recommendations do not support the need to monitor urine output and voiding in the PACU routinely in all patients, but it may be useful in selected patients.[16] However, monitoring of voiding, although not considered a discharge criterion, would still be useful particularly in patients who have had instrumentation of the urogenital tract or pelvic surgery.
Drainage and bleeding
Monitoring of bleeding and discharge is recommended in the perioperative period for early detection of complications that might need admission, transfusion, or return to the operating room.
Discharge criteria
The last few decades have seen an exponential increase in the number and complexity of surgical procedures done in an ambulatory environment driven by innovations in surgical technique, better anesthetic drugs, improvement in perioperative monitoring techniques, and economic and societal pressures.[36,37] The presence of a well-designed discharge criterion would help the nursing staff assess and manage the patients better, allow to quantitate the progress of recovery, avoid delay to discharge, and allow for comparison between centers. These criteria have been endorsed by and mandated by both the Joint Commission and other accrediting and regulatory bodies. However, there are some limitations to standard criteria as they are not applicable to all patients, surgical procedures, anesthetic techniques, and patient-related specific factors. It is also important to have historical data available regarding baseline vital signs as they might be inaccurate on the day of surgery due to anxiety.[38]
Aldrete scoring system
Aldrete and Kroulik in 1970 proposed the Post-Anesthetic Recovery Score (PARS), a method analogous to the universally adopted APGAR score which included activity, respiration, circulation, state of consciousness, and color for evaluating patients after anesthesia for their fitness to be discharged from PACU. Numerical scores of 2, 1, or 0 were given depending on their absence or presence. The numbers given to each sign were then added. A score of 10 indicated a patient in the best possible condition. Totals of 8 or 9 were noted to be acceptable for discharge from the recovery room to a step-down unit or ASU, where phase II recovery continued. Total scores of 7 or less in most cases indicated a need for continued close observation.
After the introduction of pulse oximetry, it quickly became obvious that it provided an easy and accurate method of evaluation of the oxygenation of the patients.[1,39,40] This led to the introduction of the modified Aldrete scale, where the color index was replaced by pulse oximeter values. A cut-off of 92% was arrived at by the work of Downs et al., who showed that when the SaO2 was 92% or higher on room air, there was no need for routine supplemental oxygen.[41]
The PARS system only allowed us to transition the patient from phase I to phase II care. In order to meet the requirements for discharge to home (phase III), Aldrete proposed another modification and included five additional components, namely: appearance of the dressing, severity of pain, ability to stand and ambulate, tolerance of oral fluids, and ability to urinate to reflect “street fitness”.[1] Patients were considered fit to be discharged home when their total score is 18 or higher.[1]
However, the limitations of the above scoring system became apparent, because in cases of subarachnoid or epidural (lumbar or caudal) anesthesia, patients may be unable to void for some time, even after obtaining full recovery of sensory and motor functions.
Post-anesthetic discharge scoring system
Chung et al.[2] proposed the Post-Anesthetic Discharge Scoring System (PADSS). This discharge criterion was proposed to assess patients’ “home-readiness” prior to discharge into the care of a responsible adult. It mainly incorporated five parameters: vital signs; activity and mental status; control of pain, nausea, and vomiting; surgical bleeding; and intake and output.[2] Numerical scores of 2, 1, or 0 were given depending on set criteria and the numbers given to each sign were then added. A score of 9 or above indicated a patient to be “home-ready”.
Discharge criteria have continued to evolve and have been amended by various authors with a greater understanding of the outcome following ambulatory anesthesia and the reasons for readmission following discharge. In addition, waiting for complete resolution of blocks or neuraxial anesthesia resulted in delay. Some of the current modifications are discussed below.
| Criteria | 2 | 1 | 0 |
|---|---|---|---|
| Activity | Moves all four extremities voluntarily or on command | Moves two extremities voluntarily or on command | None |
| Respiration | Breathes normally, coughs easily | Dyspnea, shallow or limited breathing | Apneic |
| Circulation | BP ± 20 mm of baseline | BP ± 20–50 mm of baseline | BP ± 50 mm of baseline |
| Consciousness | Fully awake | Arousable | Not responding |
| Oxygen saturation* | Maintains SaO2 > 92% on room air | Maintains SaO2 > 90% on supplemental oxygen | Unable to maintain SaO2 > 90% even on supplemental oxygen |
| Color | Pink | Pale, “dusky,” or “blotchy” discoloration, as well as jaundice | Cyanotic |
| Criteria | 2 | 1 | 0 |
|---|---|---|---|
| Dressing | Dry and clean | Wet but stationary | Growing area of wetness |
| Pain | Pain free | Mild pain controlled with oral medications | Severe pain requiring parenteral medications |
| Ambulation | Able to standup and walk | Vertigo when erect | Dizziness on supine |
| Feeding | Able to drink fluids | Nauseated or still fasting | Nausea and vomiting |
| Urine output | Voided | Unable to void but comfortable | Unable to void but uncomfortable |
| Criteria | 2 | 1 | 0 |
|---|---|---|---|
| Vital signs | Within ± 20% of baseline | Within ± 20–40% of baseline | Greater than 40% of baseline value |
| Activity and mental status | Oriented × 3 and has a steady gait | Oriented × 3 OR has a steady gait | Neither |
| Pain, nausea and vomiting | Minimal | Moderate having required treatment | Severe requiring treatment |
| Surgical bleeding | Minimal | Moderate | Severe |
| Intake and output | Has had PO fluids AND voided | Has had PO fluids OR voided | Neither |
Separation of pain and nausea and vomiting
Pain and nausea and vomiting were the two most common reasons for readmission following discharge from the ambulatory center. In order to give the required weightage when considering discharge, it was realized that they had to be considered separately on their own merits.
Removal of the criteria for need to urinate before discharge
The risk factors for postoperative retention of urine include a history of prior postoperative urinary retention, neuraxial anesthesia (spinal and epidural), surgery on the urogenital tract, pelvis and the anal canal, anticholinergics, and underlying medical conditions.[42–46] Urinary retention may lead to bladder over-distension, resulting in atony and inability to void following discharge from the ambulatory center.
1. Thus, patients in low-risk categories should not be required to void before discharge.
2. In patients who did not have a urinary catheter placed during surgery, the IV fluids should be used judiciously in order to prevent bladder over-distension.[43]
3. It has been suggested that ultrasound monitoring can be used to facilitate the timing of catheterization in patients at high risk of retention.[42] In case scanning facilities are not available, the bladder should be evacuated if the patient has not voided by the time he has reached the other criteria for discharge.
4. Patients who have been catheterized or who have not voided by the time of discharge should be encouraged to return to the facility or the emergency room should they fail to void in 8 hours.
Removal of the criteria for need to tolerate oral feeds
The requirement of drinking clear fluids should not be part of a discharge protocol and may only be necessary for selected patients.[16] Elimination of this criterion can shorten the stay without adversely affecting outcome following ambulatory anesthesia.[47] In a large study of almost 1000 patients, Schreiner et al.[48] showed that in pediatric patients it was unnecessary to make drinking a requisite for discharge from the day surgery center. The goal for perioperative fluid management should be to administer sufficient intravenous fluids to cover the calculated preoperative deficit, the intraoperative maintenance, and the intraoperative losses, thus preventing dehydration.[48]
The current modification that is used as a discharge criterion is the modified PADSS which includes: vital signs, ambulation, nausea and vomiting, pain, and surgical bleeding.
| Criteria | 2 | 1 | 0 |
|---|---|---|---|
| Vital signs | Within ± 20% of baseline | Within ± 20–40% of baseline | Greater than 40% of baseline value |
| Activity | Steady gait, no dizziness | Able to ambulate with assistance | Unable to ambulate |
| Nausea and vomiting | None or minimal and controlled with PO medications | Moderate and treated with IV medications | Severe and poorly controlled |
| Pain | Minimal (0–3) | Moderate (4–6) required treatment | Severe (7–10) requiring treatment |
| Surgical bleeding | None or minimal | Moderate | Severe |
Patients scoring ≥ 9 for two consecutive measurements are considered fit for discharge home.
Before the discharge can be fulfilled, the patient should be free of their IV cannula and dressed in their own clothes. The patient should have an adult escort with them on the way home and at home until the next day. The patient and chaperone should have been counseled and given written information about the following:
1. Information about the surgical procedure.
2. Not driving until the next day, not operating any heavy equipment, not taking important decisions or signing documents, not drinking alcohol.
3. Advice on appropriate daily activities, rehabilitation, training, and precautions.
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