**3.1. Intravenous PCA (IV‐PCA)**

Currently, IV‐PCA is one of the most used techniques for acute pain control. Its use is suit‐ able for virtually any patient undergoing surgery that are cursed with postoperative pain of moderate or severe intensity [18]. Many studies have demonstrated the efficacy, safety, and patient satisfaction with PCA intravenously. A meta‐analysis involving 115 randomized clinical trials demonstrated that this technique provides greater efficacy when compared to intramuscular administration of analgesics [20]. Another study showed that, among patients who received IV‐PCA, 36% experienced moderate to severe pain in the first 24 h after surgery when compared to 67% of important painful experience among patients who received intra‐ muscular opioids [21]. Moreover, it was verified that the IV‐PCA is associated with a higher rate of patient satisfaction [22].

Despite the possibility that IV‐PCA may be combined to a basal opioids infusion, it was shown that the incidence of respiratory depression with IV‐PCA was much smaller (0.19% versus 0.29%) when compared to the combination of this technique with systemic infusion of opioids (1.09–3% versus 8%) [23].

IV‐PCA is associated with potential complications inherent in the technique, which are opera‐ tor‐dependent. Errors may occur in the drug administration, usually by programming failures on infusion pump [24] and they may result in inadequate pain control, heavy sedation, respira‐ tory depression, and, eventually, death of the patient [25]. Currently, many infusion pumps feature smart devices that are equipped with an integrated software library on dosing regimens of different drugs, thus avoiding underdosing or overdosing. In these models, the smart bombs are programmed to stop operation or to alert clinicians when doses exceed the limits [26].

However, serious errors can still occur even with smart bombs. According to the Food and Drug Administration (FDA), 56,000 adverse events with these smart bombs during the period 2005–2009 have been reported [27].

Several complications may be observed from the IV‐PCA, such as clogging or dislodgement of catheters, intervals between the administrations of opiates for maintenance of analgesic effect [28]. Still, this technique implies in risk for adverse effects related to opioids [29].

Furthermore, IV‐PCA limits mobility and it reduces the comfort of the patient who is con‐ nected to the infusion pump, which can be minimized by using more modern compact equip‐ ment. Zafar et al. [30] reported that about 21% of patients who received IV‐PCA complained of reduced mobility. It is worth noting, finally, the economic aspect, as a limitation of the technique, as well as the need of equipment (infusion pump) and the discarding of remaining solutions after the PCA use, causing unnecessary costs for health services [12, 30].

The major drugs used in this system are the opioid analgesics, such as morphine, hydromor‐ phone, fentanyl, sufentanil and tramadol [31]. Meperidine is no longer considered a valid option for PCA as its toxic metabolite may be accumulated, especially in patients with abnor‐ mal kidney function [32]. Therefore, meperidine has not been recommended for acute pain [33].
