**3. Mode of analgesia administration in ICU patients**

The mode of analgesic medication administration is an important factor for the pharmacologic management of pain in the ICU. Intravenous (IV) administration is more commonly the route of choice in critically ill patients because of altered GI tract function that could lead to unpredictable absorption of medication. Intravenous route is generally preferred over subcutaneous or intramuscular routes given potentially inadequate absorption due to regional hypoperfusion due to shock, subcutaneous oedema. The Fentanyl patch can be used for chronic pain relief in stable patients but not in ICUs or for acute pain relief because of the 12–24 h delay in peak serum levels.

The choice of intermittent versus continuous infusion administration depends on factors such as the frequency and severity of pain and the pharmacokinetics of the analgesic medication. The administration in bolus is associated with the variation in the peak plasma concentration, since the infusion maintains a more stable concentration but can lead to accumulation of medication in patients with renal or liver failure.

#### **3.1. Patient-controlled analgesia (PCA)**

It is an effective method for administering analgesic medication and gives patients a sense of control over their pain. Patients have autonomy on when and how much medication they receive. However, this technique requires awake and orientated patients which make use of PCA limited in ICU patients. In combination with intravenous paracetamol and proparacetamol, the opioid consumption is significantly less [23].

#### **3.2. Nurse-controlled analgesia (NCA)**

It is inferior to the PCA but still can be useful, as nurses can administer the analgesia quickly when required or during the procedures.

#### **3.3. Regional (nerve blocks) and neuraxial (spinal or epidural)**

Analgesia techniques are used in ICU-selected trauma patients and surgical procedures. Epidural analgesia is probably the most commonly used regional anesthetic technique in the ICU. It is more useful in critically ill postoperative thoracic, abdominal, major vascular surgery, orthopedic surgery and trauma patients. Positioning patients during catheter insertion is a challenge for using regional anesthesia in ICUs. The main disadvantages of epidural and regional analgesia are the rare but catastrophic complications such as infection, epidural hematoma formation and nerve damage, which can occur in ICU patients who have a high risk of developing these complications [24].

The combination of intravenous opioid PCA, paracetamol and regional anesthesia techniques is multimodal analgesia which decreases the total opioid analgesia consumption and hence decreasing the side effects and better patient comfort. The NCA proved to not be superior to PCA and increases the rapid response team activation.
