Comparative study of intrathecal pethidine versus lignocaine as an anaesthetic and a postoperative analgesic for perianal surgery.LS Chaudhari, DG Kane, BB Shivkumar, SK Kamath
Department of Anaesthesiology, KEM Hospital & Seth GS Medical College, Parel, Mumbai.
100 patients with ASA risk I & II and undergoing perianal surgery were studied for anaesthetic effects and postoperative analgesia following either intrathecal pethidine or lignocaine. Saddle block was performed either with intrathecal pethidine 5% (50 mg/ml) 0.5 mg/kg or 1 ml of 5% lignocaine. Sensory and motor block postoperative analgesia, need for additional analgesia were studied. The onset of sensory and motor blockade with lignocaine was faster than pethidine. However the sensory and motor blockade lasted longer with pethidine. The duration of postoperative analgesia was 15.39 +/- 5.14 hours as against duration of postoperative analgesia with lignocaine which was 1.3 +/- 0.53 hours. Only 10% of patients in the pethidine group required intramuscular analgesic supplementation whereas 30% of patients in the lignocaine group required intramuscular analgesic supplementation.
Keywords: Adjuvants, Anesthesia, therapeutic use,Analgesics, Opioid, therapeutic use,Anesthesia, Spinal, methods,Anesthetics, Local, therapeutic use,Anus Diseases, surgery,Comparative Study, Female, Human, Lidocaine, therapeutic use,Male, Meperidine, therapeutic use,Pain Measurement, Pain, Postoperative, drug therapy,Time Factors,
Despite recent advances in surgery and anaesthesiology, many patients continue to experience unacceptable pain during early postoperative period. The primary reasons may relate to lack of information about analgesic drugs, misconception about their potency duration of action, side effects and addictive potential. A smooth course in the management of postoperative pain may be obtained by proper choice of the anaesthetic used.
Perianal surgery requires excellent intraoperative and postoperative analgesia. Besides pain and discomfort following perianal surgery, postoperative pain in perianal surgery can cause reflex inhibition of bladder evacuation with increase in sphincter tone.
With the discovery of opiate receptors in the spinal cord, postoperative pain relief has taken on a new dimension. The discovery that pethidine injected intrathecally had many local anaesthetic like properties has added impetus to the fast growing field of selective spinal analgesia with spinal opiates.
Our study consisted of 100 patients of either sex belonging to ASA risk group I & II and undergoing perianal surgery. They were randomly divided into 2 groups. All patients were premedicated with Inj.
Atropine 0.6 mg IM ½ an hour prior to surgery. Group I were given Inj. pethidine 5% (50 mg/ml) 0.5 mg/kg intrathecally while group II were given Inj. lignocaine 5% 1 ml intrathecally. Group I & II patients were kept seated for 5 minutes following which they were given lithotomy position. Sensory blockade was treated with a no. 24 G needle. The onset of analgesia was noted. End of sensory blockade was taken as time when patient could feel pinprick pain. Motor blockade was tested by testing sphincter laxity.
Hypotension was defined as fall of systolic BP >30% of pre block values. Postoperative pain was assessed one hourly and scored as follows:
0 = No pain, even on questioning
1 = Complaints of pain only on questioning specifically for it.
2 = Mild pain which is tolerable
3 = Moderate pain requiring analgesics
4 = Intolerable pain - the highest grade the patient had ever experienced.
In both groups patients with pain scores of 01 were not given any analgesics. Patients with pain scores of 2 were given oral analgesics in the form of tab. aspirin or paracetamol in both the groups. Patients with pain score 3 or more were given injectable analgesics in both groups. Group 2 patients (lignocaine group) with pain score more than 3 were prescribed injection pentazocine while group I patients (pethidine group) with pain score more than 3 were given NSAID infection i.e. Inj. diclofenac to avoid additive effects of narcotics.
The onset of sensory and motor blockade, the end of sensory blockade and duration of postoperative analgesia are seen in [Table - 1].
The comparison of pain scores in both groups are shown in [Table - 2].
The incidence of complication were higher in the pethidine group as shown in [Table - 3].
The effective control of postoperative pain remains one of the pressing problems whilst treating patients. With the discovery of opiate receptors in nervous tissue by Snyder et al keen interest has been shown in using this knowledge for relief of postoperative pain. Intrathecal opiate administration has been getting more and more attention in the past few years.
Pethidine has many physical characteristics including molecular weight and pka similar to local anaesthetic agents. The high lipophilicity reduces its cephalad spread, thus reducing the incidence of untoward effects like respiratory depression. In our study intrathecal pethidine had no effect on respiratory rate.
The mean onset of analgesia in our study with pethidine was 6.37 mins. This correlates well with study done by Acalovschi et al who reported mean onset of sensory analgesia of 5.28 mins.
The mean onset of motor blockade in pethidine group was 8.08 mins which also correlates well with study of Acaiovshi et al who reported the onset of motor blockade was achieved within 10 mins of intrathecal injection of pethidine.
In our study, the mean duration of postoperative analgesia with pethidine was 15.3 hours. 4 patients (8%) in pethidine group were pain free for periods upto 18-24 hours while none of the patients in lignocaine group were absolutely pain free. 42% of patients in pethidine group had tolerable pain that was elicitable only on questioning whereas only 20% of patients in lignocaine group had pain score of one.
38% of patients in pethidine group complained of mild pain, which required oral analgesics. 10% of patients in pethidine group required in analgesic supplementation whereas 30% of patients in lignocaine group required IM analgesic supplementation on patient (2%) in lignocaine group complained of severe pain i.e. pain score = 4, whereas no patient in pethidine group had pain score of 4.
The overall incidence of complications was higher with the pethidine group as compared to lignocaine group. The incidence of nausea was 38% in pethidine group and 22% of these patients had associated vomiting. Only 12% of patients in lignocaine group had nausea.
The incidence of hypotension was higher with the lignocaine group while in pethidine group only 2 patients (4%) had hypotension. Higher incidence of hypotension in lignocaine group may be possibly due to greater sympathetic block with lignocaine as compared to pethidine. One of these patients had Vaso-vagal attack just after spinal injection was completed. She recovered with intravenous atropine administration and intravenous fluids.
The incidence of urinary retention as per our study, in the pethidine group was 6%, which was considerably lesser than the lignocaine group where the incidence was 30%. All but 2 patients passed urine spontaneously; the two patients who required catheterisation had urinary retention for more than 6 hours and belong to the lignocaine group. The urinary retention with such a low level of spinal blockade could possibly be because of sacral blockade.
None of the patients belonging to the pethidine group showed any evidence of drowsiness or MS depression. Pethidine unlike morphine is highly lipophilic. This allows a rapid onset of action and minimal residual GSF concentration of the drug available for rostral spread to the brain.
The incidence of pruritus with intrathecal pethidine was 26%. However no patient required any intervention for this problem.
At the end of the study we arrived at the following conclusions
1. Intrathecal pethidine (preservative free) given in a dose of 0.5 mg/kg provides excellent anaesthesia for perianal surgery, though the time taken for onset of sensory and motor blockade are significantly longer than heavy lignocaine (5%).
2. The duration of sensory blockade is longer with intrathecal pethidine than lignocaine.
3. The significantly longer post-operative analgesia seen in patients given intrathecal pethidine is extremely beneficial in patients undergoing perianal surgery.
4. The lack of any serious side effects such as respiratory depression after intrathecal pethidine (0.5 mg/kg), make it an extremely safe technique.
[Table - 1], [Table - 2], [Table - 3]