A single blind, randomized, with blinded evaluation by third parties clinical trial is carried out to assess the analgesic efficay of the addition of morphine chloride to a low dose solution of spinal local anaesthetic compared to a standard dose spinal anaesthetic in the haemorrhoid surgery.

The objective of this clinical trial is to assess if the experimental treatment is as efficacy as the standard treatment in the anesthetic and analgesic effects with less side effects, greater and earlier mobility after surgery and shortened the hospitalization.

DESIGN OF THE TRIAL:

A multicentre, randomized, single-blind, with masked evaluationby third parties clinical trial.

The Clinical Pharmacology Unit will perform a permuted blocks randomization scheme for each of the two hospitals participating in the trial. The result of this randomization will be kept in this unit and will not be accessible to investigators. Investigators will receive a series of opaque sealed envelopes with a number corresponding to the order of entry of the patients into the trial. When the patient is in the operating room, investigators must open the envelope which contains the group of treatment assigned to that patient. The patient will not know in which intervention group is included. Investigator who performs the spinal puncture and investigator who collects the data and performs the evaluation will no be the same person. This will allow a blind evaluation.

OBJECTIVES:

Main objective:

To evaluate whether the addition of morphine chloride to a low dose solution of local intradural anaesthetic in patients undergoing hemorrhoids surgery produces an anaesthetic efficacy comparable to that produced by a standard dose of local intradural anaesthetic and an improvement of postoperative analgesic efficacy.

Secondary objectives:

• Earlier mobilization of the patient.
• Minor adverse effects.
• A shorter hospital stay of the patient.

TREATMENTS:

Two groups of treatment will be formed, experimental and comparator. The experimental group will receive 3mg of Bupivacaine with addition of 50 micrograms of Morphine Chloride.

The comparator group will receive 5 mg of Bupivacaine.

RESCUE TREATMENTS

If necessary before surgery, midazolam will be administered from 0.02 to 0.05 mg / kg intravenous (IV) depending on clinical response and after the patient is set in the surgical position, if necessary, an intravenous infusion of propofol will be administered at 0.5 - 2mg / kg / h. Sedative drugs with analgesic effects as opioids, ketamine, etc, will be avoided to not interfere with the main analgesic study assessment.

After surgery and during the hospitalization stay the rescue analgesia treatment will be administered only on demand. The rescue treatment allowed by protocol will be an intravenous administration of dexketoprofen up to 50 mg / 8 h and if insufficient, a rescue of 3 mg of morphine chloride will be administered. If morphine chloride is received, these patients will be recorded in the case report forms as inefficacy of the treatment. At home, after discharge, patients will receive rescue analgesia with capsules of dexketoprofen 25 mg / 8 h. (up to 75 mg a day).

SAMPLE SIZE:

66 patients ( 33 patients in the experimental group and 33 patients in the control group)

EFFICACY ASSESSMENT

Pain will be assessed using a visual analog scale (VAS from 0 to 10) at the beginning and end of surgery, at the arrival of resuscitation unit, after 10 and 30 minutes after arrival, during hospitalization stay out of the resuscitation unit and daily at home after discharge.

Doses required of rescue analgesia and hospitalization time will be recorded.

SAFETY ASSESSMENT

Basic monitoring as usual will be perfomed in the surgery room. Motor blockage will be assessed using the modified Bromage scale as follows: 1 = complete motor blocking, 2 = able to move feet only, 3 = patient move the feet and bend the knee, 4 = straight leg raises <30 ° or > 30 ° but not against resistance, 5 = lifts leg> 30 ° against resistance. This measure will be made after surgery in the surgery room and at the arrival and at one hour after resuscitation unit admission.

All the Adverse events will be reported.

Inclusion Criteria:

• Patients undergoing hemorrhoidectomy.
• Age between 18 and 64.
• Both gender
• ASA I to III.
• With indication for spinal block.
• People capable to grant the informed consent.

Exclusion Criteria:

• Patients with allergies to the study drugs.
• Patients with any contraindication for performing a spinal technique (coagulation disorders, fever, intracraneal hypertension, abscess in the puncture site, etc..).
• Patients with previous neurological disorders.
• Pregnant women.
• Women who may be pregnant and do not have a negative pregnancy test.
• Breastfeeding women.
• Patients with uncapable to give informed consent.