Intravenous lignocaine and ketamine infusions are advanced methods for treating difficult, treatment-resistant chronic pain, particularly of a neuropathic character. Infusions are performed under controlled conditions with continuous monitoring, at sub-anaesthetic doses – the patient remains conscious and communicative throughout.

  • Intravenous lignocaine (lidocaine) infusion
  • Intravenous ketamine infusion (sub-anaesthetic dose)

INTRAVENOUS LIGNOCAINE (LIDOCAINE) INFUSION

Lignocaine administered intravenously at low (sub-anaesthetic) doses has documented analgesic action that extends beyond the classical local anaesthetic effect.

Mechanism of action

  • SODIUM CHANNEL (Na+) BLOCKADE on hypersensitised nociceptors – membrane stabilisation, reduction of spontaneous discharges
  • ANTI-INFLAMMATORY EFFECT – inhibition of IL-1β, IL-6 and TNF-α synthesis
  • NMDA AND GABA RECEPTOR MODULATION
  • REDUCTION OF CENTRAL SENSITISATION – ‘resetting’ hypersensitive pain pathways in the spinal cord
  • EFFECT ON SYMPATHETIC NERVE ENDINGS – critical in CRPS treatment

Indications

  • Peripheral neuropathies resistant to standard treatment (diabetic, post-herpetic, post-chemotherapy)
  • Refractory trigeminal neuralgia
  • Fibromyalgia
  • Complex Regional Pain Syndrome (CRPS)
  • Chronic myofascial pain
  • Refractory migraine
  • Cancer pain

Procedure

  • Dose: 5 mg/kg body weight (typically 300–500 mg) in 100 ml saline
  • Infusion time: 30–60 minutes via infusion pump
  • Continuous ECG, blood pressure and oxygen saturation monitoring
  • Patient in a comfortable position, conscious and communicative
  • Post-infusion observation: 30–60 minutes
  • Cycle: 1–3 infusions per series, at 1–2 week intervals; cycles every 1–3 months

INTRAVENOUS KETAMINE INFUSION

Ketamine is a dissociative anaesthetic with potent analgesic action that at sub-anaesthetic doses (0.1–0.5 mg/kg/h) demonstrates exceptional efficacy in neuropathic pain resistant to other treatments. The mechanism of action is complex and extends beyond classical NMDA receptor blockade.

Mechanism of action

  • NMDA RECEPTOR ANTAGONISM – the main mechanism; NMDA receptors are responsible for central sensitisation (crucial in chronic pain)
  • OPIOID RECEPTOR AGONISM (μ, δ, κ) – complementing the analgesic effect
  • MUSCARINIC AND NICOTINIC RECEPTOR MODULATION
  • GABA RECEPTOR EFFECT
  • REDUCTION OF OPIOID-INDUCED HYPERALGESIA
  • ANTI-INFLAMMATORY AND NEUROPROTECTIVE EFFECT
  • ANTIDEPRESSANT EFFECT (mediated via BDNF, glutamate) – important in patients with chronic pain and depression

Indications

  • Complex Regional Pain Syndrome (CRPS) – one of the best-documented indications (Level B per ASRA/AAPM/ASA 2018)
  • Refractory peripheral neuropathy
  • Spinal cord injury pain
  • Refractory fibromyalgia
  • Phantom pain after amputations
  • Cancer pain resistant to opioids
  • Opioid-induced hyperalgesia
  • Chronic pain with concomitant refractory depression

Procedure (CRPS protocol)

  • Dose: 0.35 mg/kg/h for 4 hours (alternative: 80 mg as a single dose over 2h for CRPS, or 0.5 mg/kg over 30–90 min for other indications)
  • Infusion via pump in 100–250 ml saline
  • Pre-treatment: midazolam (1–2 mg) and ondansetron (4 mg) – reduction of psychomimetic effects and nausea
  • Continuous monitoring: ECG, blood pressure, oxygen saturation, consciousness level assessment
  • Patient lying in a comfortable position, in a calm environment (to reduce dissociative effects)
  • Post-infusion observation: 1–2 hours until complete resolution of psychomimetic effects
  • Cycle: typically 3 infusions at 2–4 week intervals; cycle repetition every 3–6 months

Lignocaine + Ketamine Combination – Synergy

Combining lignocaine and ketamine infusions produces a synergistic effect: lignocaine blocks the peripheral component of pain (Na+ channels on nociceptors), ketamine blocks the central component (NMDA receptors in the spinal cord and brain). Together they produce a stronger effect than either drug alone, at lower doses and with lower risk of side effects.

Effects of Infusions (lignocaine, ketamine, combination)

  • First relief: during the infusion or a few hours after
  • Full effect: 1–2 weeks after the infusion
  • Duration of effect: 2–12 weeks (in CRPS after ketamine cycle: up to 12 weeks; with ‘ketamine coma’ in selected cases: effect up to 5–11 years – but this is an advanced hospital procedure, not our outpatient protocol)
  • In CRPS patients: 30–60% pain reduction, functional improvement in approximately 50%
  • In diabetic/post-herpetic/post-chemotherapy neuropathy: 30–50% pain reduction over 4–12 weeks
  • Possibility of reducing opioid consumption

Possible Side Effects

Lignocaine:

  • Perioral numbness, metallic taste (a signal to slow the infusion)
  • Dizziness, nausea
  • Very rarely (with rapid administration): cardiac arrhythmia, seizures

Ketamine:

  • Psychomimetic effects (feeling of ‘floating away’, hallucinations, perceptual disturbances) – usually mild, reduced by midazolam
  • Nausea, vomiting (prophylaxis with ondansetron)
  • Blood pressure and heart rate elevation
  • Facial flushing
  • In some patients: post-procedure feeling of relaxation and mood improvement (antidepressant effect)
  • Rarely: urinary retention, visual disturbances

Contraindications

  • Heart failure, unstable coronary artery disease, arrhythmias
  • Uncontrolled arterial hypertension (for ketamine)
  • Raised intracranial or intraocular pressure
  • Severe hepatic failure
  • Pregnancy and breastfeeding
  • Active psychosis, schizophrenia (for ketamine)
  • Drug allergy

FAQ

Will I lose consciousness during a ketamine infusion?

No – we use SUB-ANAESTHETIC doses (3–10 times lower than for anaesthesia). The patient remains conscious and communicative throughout; they may experience mild dissociative effects (feeling of ‘floating’, body lightness) which are transient and resolve after the infusion ends.

When will I feel the effect of the infusions?

The first effect is often felt during the infusion itself or a few hours after. The full effect develops over 1–2 weeks. In patients with CRPS or fibromyalgia, the effect lasts 4–12 weeks and may become stronger with each successive cycle.

Are ketamine infusions addictive?

When used medically, at controlled doses and under supervision – the risk of dependence is very low, unlike recreationally used ketamine (high doses, frequent use). In our protocol, infusions are administered at minimum 2–4 week intervals, virtually eliminating the risk of dependence.