Nefopam vs Tramadol in the Prevention of Post Anaesthetic Shivering

Overview

Post Anaesthetic Shivering is a common complication of Subarachnoid block. It is graded based on it's severity and has been known to cause various problems like patient's discomfort, hypoxia, change in hemodynamic variables of the patient and poor wound healing. This problem has been managed via pharmacologic and non-pharmacologic means. Non-pharmacologic modalities involve options aimed at warming the patient. Pharmacologically, opioids are used more commonly to prevent and treat this condition. This then introduces the side effect of nausea/vomiting and sedation which may reduce overall patient's satisfaction on the perception of the Subarachnoid block. It is for this reason that Nefopam - a centrally acting non-opioid, non-steroidal anti-inflammatory drug (NSAID) analgesic, relatively new drug in the Nigerian market with significant anti-shivering effect is compared with a well established opioid like Tramadol. Having similar cost profile, the option of replacing Tramadol with Nefopam especially in conditions where the patient is more hemodynamically unstable is considered in this project.

STUDY LOCATION This study would be carried out in Gbagada General Hospital and other General hospitals in Lagos state. They are all secondary health care facilities with 800 bed spaces in Gbagada and about 3000 in the other centres. Gbagada is a suburban area centrally located in Lagos state and the General hospital was established in 1983. STUDY DESIGN The study would be a prospective, double-blinded, randomised control study in which both the investigator and the patient would be blinded to the study drugs. Patients would be randomised into 2 groups. In one group, patients would be given 1mg/kg of tramadol diluted with water for injection to a volume of 10mls. In the second group patients would receive 0.15mg/kg of nefopam diluted with water for injection up to a volume of 10mls. STUDY POPULATION Patients aged 18 to 45 years with American Society of Anesthesiologists (ASA) physical status II or III scheduled for Caesarean Sessions (CS) amenable to Subarachnoid block who have given written informed consent will be recruited into this study ANAESTHETIC TECHNIQUE Participants would be randomly divided into 2 groups. Nefopam and Tramadol group via a randomization system. PREPARATION Patients would be recruited the night before or the morning of surgery. They would be reviewed to allay fear, determine fitness to be part of the study and get consent to join. They would be given the information/consent papers to study and where illiterate or where they do not understand, contents would be explained to them in a language they understand. Verbal and written consent would then be obtained. After being adequately examined, routine investigations carried out and patient fasted, 2 wide bore Intravenous lines would be sited and the patient weighed. Patients would be routinely given premedication: IV Metoclopramide 10mg and IV Ranitidine 50mg RANDOMIZATION Patient would then be randomly assigned to either of two groups, the tramadol or nefopam group. A randomization schedule would be prepared with sealed envelopes with randomly generated odd and even numbers. The number would be seen only by an assistant who would prepare the chosen medication which are both colourless up to 10mls in an unmarked syringe. Nefopam would be given at 0.15mg/kg and Tramadol 1mg/kg. The patient and Administrator would both be blinded to the content of the syringes. The Assistant with the code would remain within the theatre premises in the event that there is a need to, repeat the chosen drug or break the code in the event of a drug reaction. The theatre environment would be kept at the ambient temperature of between 20 - 25oC and no active warming would be instituted. The Administrator or Researcher would assess each patient for both the primary outcome (shivering) and for the side effects of the study medication. INDUCTION Baseline vital signs of Non-Invasive Blood Pressure, Mean Arterial Pressure, Pulse Rate, Oxygen Saturation and Temperature measurements would be taken. Patient would be preloaded with I0mls/kg of Normal saline 15mins before initiation of the block. Placed in the sitting position with a pillow support, routine draping and asepsis would be maintained and using a 25 guage(G) or 26G quincke needle, 12.5mg of 0.5% heavy bupivacaine would be injected at the level of between L2/L3 to L4/L5 interspace. Patient would then be placed supine and given the pre-chosen drug via slow intravenous injection by the assistant who is not part of the study at Time 0 using a Stop Clock. After the initiation of the block, these parameters would be measured every 5minutes for the first 15mins and every 15 minutes up to 60minutes post initiation of the block. If shivering occurred, the severity would be checked by the principal investigator and a repeat dose of the drug given by the assistant. If this doesn't abate after another 5minutes, a rescue drug of 25mg Pethidine would be given to the patient. Type of surgery, Bupivacaine dose used, Highest sensory block reached at 10minutes using alcohol swab, Shivering scores, Sedation Scores and Duration of surgery would be documented. Hemodynamic parameters taken at the beginning of surgery would also be recorded every 5minutes for 60minutes. Hypotension will be defined as less than 20% of the baseline MAP or a value below 60mmHg would be treated by increasing maintenance fluid and Ephedrine using 3mg aliquots. Incidence of PAS would be determined in both groups; Duration between start of block and onset of PAS and if any other method of stopping PAS was needed to be adopted like repeating the initial dose or IV pethidine 25mg.