Hemodynamic variables and side effects of 0.75% preservative free Ropivacaine for lower abdominal surgeries

Abstract               Bupivacaine has been shown to have selective cardiac effects related to the slow rate at which it dissociates from the sodium channel.4, 13 An important aspects of this toxicity is that it involves a significant degree of stereo specificity, with the ‘S’–isomer showing significantly less cardiotoxic effect. After institutional ethical committee approval and after informed consent of the patients, this study was undertaken on 60 patients of either sex, aged between 20 to 60 years belonging to ASA physical status grade I and II , scheduled for elective lower abdominal surgery. There was 10% decrease in Heart rate from the base line value and the maximum drop in Heart rate occurred at mean time of 26.08 ± 4.22 minutes from the time of injecting study drug in to the epidural space. No patients had bradycardia throughout the procedure. Side effects were very minimal in the present study.

Key Word: Hemodynamic variables, Ropivacaine, lower abdominal surgeries

INTRODUCTION

In 1850, about three centuries after the conquest of Peru by Pizzaro, the Austrian von Scherzer brought a sufficient quantum of coca leaves to Europe to permit the isolation of cocaine For many centuries the inhabitants of Peru and Bolivia chewed the leaves of the shrub Erythroxylum Coca along with lime ash to diminish fatigue. The active ingredient in Coca leaves was cocaine, which was isolated and named by Albert Niemann in 1860. As suggested by Pizzaro descriptions of the properties of the coca prompted the Austrian Karl Koller to perform in 1884 the first clinical operation under local anaesthesia, by administration of cocaine on the eye.¹ The use of cocaine for local and regional anaesthesia rapidly spread throughout Europe and America. The toxic effects of cocaine were soon identified resulting in many deaths among both patients and addicted medical staff. Local anaesthesia was in a profound crisis until the development of modern organic chemistry which led to the synthesis of pure cocaine 1891.The great advantage of local anaesthesia with Cocaine was, it anaesthetized only the part of the body on which the operation was to be performed. However a price was paid in toxicity and short duration of action. Which lead to continued investigation in search for a safe, long acting local anaesthetic agent.²                 New amino ester local anaesthetics were synthesised between 1891 and 1930 such as tropicaine, eucaine, holocaine, orthoform, benzocaine and many more including Bupivacaine, till 1972. All these drugs were ostensibly less toxic than cocaine, but they had differing amounts of Central nervous system and Cardiovascular toxicity. The local anaesthetic used should possess ideal characteristics like high potency and low toxicity. Bupivacaine was of special interest because of its longer duration of action and history of clinical application. Synthesized by Ekenstam in 1957 and introduced into clinical practice in 1965 by Widman became a very popular local Anaesthetic agent.³ In an editorial published in 1979 by George. A.N. Albright stated that Bupivacaine might result in almost simultaneous seizures and cardiovascular collapse without antecedent hypoxia from typical clinical doses following inadvertent intravascular administration.⁴ One of the specific features of Bupivacaine is that clinical evidence of accumulation of the drug in plasma may not be appreciated until a fairly late stage because of its high affinity for plasma protein binding sites. The free concentration of the drug in plasma remains low until all the protein – binding sites are fully occupied, after which it increase rapidly and toxicity can occur without patients exhibiting signs of CNS toxicity before cardiovascular collapse.⁵ More than that Bupivacaine has been shown to have selective cardiac effects related to the slow rate at which it dissociates from the sodium channel. An important aspects of this toxicity is that it involves a significant degree of stereo specificity, with the ‘S’ – isomer showing significantly less cardiotoxic effect.⁶ These findings generated the search for alternative to Bupivacaine. This search was concentrated on amide linked agents, which in current practice have largely suppressed the ester type drugs. With the advantage in stereoselective synthesis it was found that agents composed of single enantiomers have clinical advantages over racemic compounds.⁷ The identification of optically active isomers of the mepivacaine family led to the selection of ropivacaine a pure S-(-) enantiomer. Ropivacaine is a new amide local anaesthetic agents that has been produced as a pure S – isomer which is the propyl analogue of bupivacaine having a butyl group in same position.⁸ The parent compound of ropivacaine was first synthesized in the 1950’s¹⁶ but it was only when concerns about the cardiotoxicity of bupivacaine became apparent that ropivacaine was fully evaluated. Ropivacaine administered by intravenous infusion was found to be less toxic than bupivacaine in human Volunteers. Mild CNS symptoms and minor cardiovascular toxicity as measured by changes in contractility and conductivity occurred at lesser dosage and lower plasma concentration with bupivacaine compared to Ropivacaine.⁹ When used for epidural anaesthesia ,ropivacaine provided satisfactory surgical anaesthesia with a long duration of action. It was found to be an efficacious and potent local Anaesthetic agent when used for epidural anaesthesia¹⁰ When compared with same concentration of bupivacaine, ropivacaine produces identical sensory block. The motor block produced by ropivacaine was found to be slower in onset. Lessintense and shorter in duration. But some studies have shown similar motor effects with ropivacaine and bupivacaine. Both bupivacaine andropivacaine have been shown to have similar cardiovascular changes when used for epidural Anaesthesia.^11,12

 METHODOLOGY

This study was a prospective study conducted in Medical college and Hospital.A written and informed consent was taken from allthe patients included in the study. Ethical clearance was taken from the hospital ethical committee as per protocol. After institutional ethical committee approval and after informed consent of the patients, this study was undertaken on 60 patients of either sex, aged between 20 to 60 years belonging to ASA physical status grade I and II , scheduled for elective lower abdominal surgery.

Inclusion Criteria

• Patients aged between 20-60 years.
• Patients of either sex.
• Patients with ASA Grade I and II.

Exclusion Criteria

• Pregnant women.
• Patients with H/o Cardio-Respiratory disorders
• Patients with Hepatic and Renal disesase.
• Patients with h/o convulsions and neurological deficits.
• Patients with Spinal deformities and Psychiatric diseases.
• Patients with Aspirin ingestion / anticoagulants in the preceding week. 

Haemodynamic and vital parameters like ECG, blood pressure (Systolic, Diastolicand Mean arterial bllod pressure), heart rate, SpO₂ monitoring was done continuously every 5 minutes for 1^st hour, every 15 mins for next 2 hours and every 30 minutes later on until complete recovery from sensory block. Continuous monitoring of ECG and changes in Heart rate and rhythm noted till the patient was shifted out from post anaesthesia recovery room. In the event of fall of heart rate lessthan 60 beats/minute, it was treated with Inj: Atropine IV and Mean arterial blood pressure fall less than 60 mm of Hg, it was treated with vasopressors and intravenous fluids. Crystalloid IV fluids given intra operatively and quantity given were recorded. Side effects like Hypotension, Bradycardia, Nausea, Vomittingand Shivering in Intra-operative period were noted. Patients were educated about the verbal numerical scale to quantify pain in the post operative period. All patients were observed in the post anaehesia recover room and in the ward until complete recovery from sensory blockade and duration of post operative analgesia and any side effects if present were recorded . Rescue analgesia was given when VAS score was between 2.5 to 5 and time noted. Patients were also observed for next 24 hours after the procedure.

RESULTS

The mean age of the patients was 39.18±8.49 years. The gender distribution was equal .ie. there were 30 Male and 30 Female patients in the study. 63.3% of Male patients were in the age group of 31-50 years while 100% of Female patients were in the same age group. (Table 1) All the patients were connected to Philips Intelliviue MP20 monitors and all the haemodynamic parameters like Heart rate, Systolic blood pressure, Diastolic blood pressure and mean arterial blood pressure were recorded and monitored every 5 minutes for first hour, then every fifteen minutes for next 2 hours and later every 30 minutes till complete recovery from the sensory block. There was 10% decrease in Heart rate from the base line value and the maximum drop in Heart rate occurred at mean time of 26.08 ± 4.22 minutes from the time of injecting study drug in to the epidural space. No patients had bradycardia throughout the procedure. (Table 2) In our study, it was observed a fall of 10% in the mean systolic pressure from the base line value and the maximum decrease occurred at a mean time period of 30.41 ± 4.04 minutes.(Table 3) Even the mean Diastolic blood pressure showed a fall of 12% from the base line value and the maximum fall occurred at a mean time of 26.08 ± 4.22 minutes.(Table 4) The mean arterial blood pressure showed a similar trend like diastolic blood pressure and maximum decrease occurred at a mean time of 26.08 ± 4.22 minutes. ECG was monitored continuously for all patients and none of the patients had any significant change from pre operative period ECG. All the patients were given 100% Oxygen through plain face mask @4L/min. The mean SpO2 was 99%-100% in all the patients. All the patients were spontaneously breathing and no significant change noted. (Table 5) In the present study, all the patients were pre-loaded with Rnger’s Lactate fluid @ 10 ml/Kg over 30-60 minutes before the epidural procedure was started. The mean intra operative crystalloid requirement was1000 ± 225 ml. The Mean arterial pressure fell less than 60 mmHg in 3 patients and were treated with Inj. Mephenteramine 6 mg- one dose. All of them responded and no further dose of vasopressor agent was required. No patients developed bradycardia and none of the patient received Inj Atropine.

Table 1: Age and sex distribution

Table 2: Heart rate distribution