What are the analgesia options for a patient with a prosthetic hip dislocation, severe pain (9/10), and contraindication to Non-Steroidal Anti-Inflammatory Drugs (NSAIDs), who has already received maximum doses of paracetamol (acetaminophen), metamizole (dipyrone), morphine, and fentanyl?

From the Guidelines

For a patient with prosthetic hip dislocation experiencing severe pain (9/10) who has contraindications to NSAIDs and has already received maximum doses of paracetamol, metamizole, morphine, and fentanyl, the most appropriate additional analgesia option is low-dose ketamine, as it has been shown to reduce pain score and opioid consumption in the 48 h following surgery, especially in patients who have undergone major chest, abdominal, and orthopedic surgery 1.

The patient's current pain management regimen has not provided adequate relief, and considering the contraindication to NSAIDs, alternative options must be explored. Regional nerve blocks, such as a femoral nerve block or fascia iliaca compartment block, could provide targeted pain relief to the hip area without systemic side effects. However, the use of ketamine as an adjuvant analgesic is supported by recent evidence, which suggests that subanesthetic doses of ketamine have evidence of efficacy in acute pain management, with recommended doses being boluses < 0.35 mg/kg and infusions at 0.5-1 mg/kg/h 1.

Some key points to consider when using ketamine for analgesia include:

• The recommended dose for severe acute pain management using an IV-PCA is 1–5 mg 1
• Ketamine should not be used in uncontrolled cardiovascular disease, pregnancy, active psychosis, severe liver dysfunction, high intracranial, and ocular pressure 1
• The use of ketamine can reduce pain score, and opioid consumption in the 48 h following surgery, especially in patients who have undergone major chest, abdominal, and orthopedic surgery 1

Other options, such as gabapentinoids and muscle relaxants, may also be considered, but the evidence supporting their use in this specific context is less clear. Procedural sedation for hip reduction should be considered urgently, as definitive treatment of the dislocation will provide the most effective pain relief.

Key benefits of using ketamine in this scenario include:

• Reduction in pain score and opioid consumption
• Ability to provide analgesia through different pathways than opioids
• Potential to avoid respiratory depression associated with escalating opioid doses

Overall, the use of low-dose ketamine as an adjuvant analgesic is a reasonable option for this patient, given the current evidence and the need to provide effective pain relief while minimizing the risk of adverse effects.

From the FDA Drug Label

DOSAGE AND ADMINISTRATION See Full Prescribing Information for important dosage and administration instructions. (2) Induction of anesthesia: --Intravenous route: Initially, 1 to 4.5 mg/kg administered slowly (over a period of 60 seconds). Alternatively, administer a dose of 1 to 2 mg/kg at a rate of 0.5 mg/kg/min. (2.2) The most common adverse reactions are emergence reactions and elevated blood pressure and pulse (6).

The patient's severe pain (9/10) has not been adequately managed with the current medications. Considering the patient has already received maximum doses of paracetamol, metamizole, morphine, and fentanyl, and NSAIDs are contraindicated, ketamine can be considered as an analgesic option.

• The dosage of ketamine for analgesia is not explicitly stated in the provided drug labels, but the labels provide information on the dosage for induction of anesthesia.
• Caution should be exercised when using ketamine, especially considering the patient's severe pain and potential for emergence reactions and elevated blood pressure and pulse.
• It is essential to monitor vital signs and cardiac function during ketamine administration, as stated in the drug label 2.
• The use of ketamine should be carefully considered, and the patient should be closely monitored due to the potential risks, especially when combined with other CNS depressants, such as the opioids already administered 2.

From the Research

Analgesia Options for Prosthetic Hip Dislocation

The patient's severe pain (9/10) despite receiving maximum doses of paracetamol, metamizole, morphine, and fentanyl, and with NSAIDs being contraindicated, presents a challenging situation. Considering the available evidence, the following options can be explored:

• Ketamine as an Analgesic Adjuvant: Studies have shown that ketamine can be an effective analgesic adjuvant for severe pain, particularly in cases where pain is poorly responsive to opioids 3, 4, 5. Ketamine's mechanism of action, primarily as an N-methyl-D-aspartate (NMDA) receptor antagonist, makes it useful in treating neuropathic pain and opioid-resistant pain.
• Low-Dose Ketamine: Low-dose ketamine has been found to improve pain relief in patients receiving intravenous opioids for acute pain in the emergency department 6. It may be a viable adjunct to morphine for the treatment of moderate to severe acute pain.
• Patient-Controlled Analgesia (PCA) with Ketamine: There is evidence to suggest that ketamine PCA can be a viable treatment option for patients suffering from intractable central pain, allowing for significant reduction in opioid dosage 7.

Considerations for Ketamine Use

When considering ketamine as an analgesic option, the following points should be taken into account:

• Dosing: The effective dose of ketamine for analgesia can vary, but low doses (e.g., 0.15 mg/kg or 0.3 mg/kg) have been shown to be effective in some studies 6.
• Side Effects: Ketamine can cause side effects such as nausea, vomiting, dizziness, and emotional distress 4, 6. Close monitoring of vital signs and observation for signs of oxygenation of tissue are necessary.
• Combination with Opioids: Ketamine can potentiate the effects of opioids, allowing for reduced opioid doses and potentially minimizing opioid-related side effects 4, 6.