The American Society of Anesthesiologists (ASA) Task Force on Postanesthetic Care defines the following guidelines for discharge [3]:

>> “Interesting book, but will it help my clinical practice?” thought Dr. Finn, as he put it aside to care for the newly arriving patients from the OR. One patient had a total knee replacement, another had laparoscopic cholecystectomy, and the third had a vaginal hysterectomy; all three procedures were unremarkable and carried out under general anesthesia. Dr. Finn began caring for the patients, treating problems such as pain, nausea, and shivering. In the meantime, the wards were calling again, so Dr. Finn gave in and accepted the patient needing the epidural and planned the patient requiring the CVC for half an hour later. Charge nurse Bridgette was very annoyed with this plan and left to take a coffee break. This left only the remaining PACU nurse and Dr. Finn to take care of all of the PACU patients.

While Bridgette was gone, two new patients arrived in the PACU, one patient who had a varicose vein surgery and one patient with a femur fracture repaired using an intramedullary rod. As Dr. Finn hooked them up to monitors, the patient S/P cholecystectomy requested help due to persistent nausea. Dr. Finn gave ondansetron 4 mg IV as the patient needing the epidural placement arrived.

Now the PACU had become immensely stressful; the nauseated patient received no relief from the ondansetron and began to vomit, and the patient S/P hysterectomy was still complaining of pain after 10 mg of morphine IV. Unfortunately, coagulation study results were still pending and needed to be done before the epidural could be performed.

The only thing that was going as it should at that moment was that the total knee replacement patient was ready for discharge. Dr. Finn first wanted to check the epidural patient’s coagulation results and care for the patient with pain after the hysterectomy.

The hysterectomy patient was 68 years old, ASA 2, and 85 kg. Despite receiving metoprolol preoperatively for hypertension, her heart rate was 110/min. He again administered 5 mg morphine IV and promised her it would be better soon.

PONV is a common problem in the PACU, but can also occur many hours later, after discharge from the PACU. Patients are not only miserable, but PONV also affects the healing process, for example, by slowing the start of oral intake. Also, many patients use PONV to rate the quality of anesthesia; therefore, the importance of PONV is significant to anesthesiologists.

Many factors influence the occurrence of PONV, although some factors are controversial [1]:

Patient factors:

Influence of anesthesia:

Influence of the surgical procedure:

In cases of prolonged PONV, a gastrointestinal mobility disorder must be considered. There is a large selection of medications available for therapy and prophylaxis of PONV, many of which can be administered synergistically. For example:

Apart from pharmacological therapy and prophylaxis for PONV, acupuncture at the standard P6 (also known as Neiguan) point, located on the ventral side of the wrist, is also effective [6]. All therapeutic choices share the same NNT (number needed to treat) between five and ten. This means that in a NNT of 5, one out of five patients will benefit from the therapy. The second bit of good news is when a method fails, there is no information given about the effectiveness of other alternatives. The take-home message is that a combination of various medications or methods is useful and often clinically successful.

With PONV, it is important that patients with increased risk are identified preoperatively and prophylactic measures are begun before or during induction of anesthesia. The identification is made easier by an algorithm specific for your hospital. Figure 4.1 shows an example of a PONV algorithm. The algorithm is based on North American [5] guidelines. In addition, outpatient surgery was included as a risk factor, in order to reduce the occurrence of delayed discharge due to PONV.

>> The gallbladder patient vomited again. Dr. Finn didn’t get an emesis basin to her quickly enough; the bedding now needed to be changed as soon as possible by the remaining PACU nurse. He wondered a little about charge nurse Bridgette; she seemed to be taking a very long time at her break. The telephone rang with the coagulation results. They were normal, so he began to obtain informed consent from the epidural patient.

As charge nurse Bridgette walked in and realized what was going on, she gave Dr. Finn a scolding look. She returned to the hysterectomy patient, noting that she was still in pain, so nurse Bridgette administered 5 mg morphine IV, and due to tachycardia, she increased the rate of the Lactated Ringer’s solution. After that, she called the ward and requested pickup of the patient who had recovered from his arthroscopy, and she began to assist Dr. Finn in the epidural catheter placement. The monitor of the hysterectomy patient went off, due to an oxygen saturation of 89 %. The patient appeared agitated. Dr. Finn was in sterile drapes, so charge nurse Bridgette turned up the hysterectomy patient’s oxygen from 1 to 4 l/min. Thereafter, the saturation quickly rose to 95 %.

This patient received general anesthesia with muscle relaxation and mechanical ventilation. With general anesthesia, worse in the presence of mechanical ventilation, atelectasis occurs in the dorsal caudal areas of the lungs. The measurable results are:

These changes are still in effect after general anesthesia has worn off and can last for an unpredictable period of time. Because of the ventilation–perfusion () mismatch with increased dead space ventilation and increased intrapulmonary right to left shunt, PACU patients often have hypoxemia or hypercapnia. Other factors, such as reduced ventilation due to pain upon breathing or the respiratory depression caused by medications, can intensify the problem.

Oxygen is dissolved in blood plasma and chemically bound to hemoglobin. The amount of each form transported is dependent on the partial pressure of oxygen (P_aO₂). The oxygen saturation of blood (S_pO₂) shows the percent of hemoglobin which is saturated with oxygen. The relationship of S_pO₂ and P_aO₂ is demonstrated by the O₂ binding curve. An S_pO₂ value of 90 % correlates to a P_aO₂ value of 60 mmHg.