Post-operative muscle pain and serum potassium changes following self-taming of succinyl choline-induced fasciculations.
The excellent muscular relaxation produced by succinylcholine provided ideal conditions for endotracheal intubation and for very short surgical procedures where good muscular relaxation for brief periods is required. However, such a popular and extensively used short acting muscle relaxant is not devoid of several undesirable side effects which may not be only harmful but even fatal under certain conditions. These side effects are postoperative muscle pains, and rise in serum potassium,, ,  intra-ocular tension and intragastric pressure. In order to alleviate or minimise these side effects, various pre-treatment methods have been extensively tried. These included pre-treatment with a small dose of non-depolarising type of relaxant, lignocaine and the administration of vitamin IG in the pre-, per- and post-operative periods.
Although these methods were helpful to certain extent, each, one had drawbacks of its own. In the present study, we have tried. to evaluate the effectiveness of a relatively new method of pre-treatment "self-taming of succinylcholine-induced fasciculations" with a small subparalytic dose of succinylcholine (0.15 mg/kg) after induction with thiopentone, about 45 seconds before the full paralytic dose of succinylcholine is administered. The observations include the incidence and intensity of muscular pains in the postoperative period and the changes in serum potassium during induction of anaesthesia.
To find out the effectiveness of "taming," a small subparalytic dose of suxamethonium (015 mg/kg) after induction with thiopentone about 45 seconds before the full paralytic dose of suxamethonium (1 mg/kg) is given.
A total of 125 patients were investigated in the present study. They were divided into two groups. Group I consisted of 75 patients who received a small subparalytic dose of succinylcholine for taming as described above. Group II consisted of 50 patients who were induced by conventional method but did not receive any pre-treatment measures.
The pre-medication was kept uniform in both groups of patients. The selected patients belonged to an age group of 2050 years and none had fluid or electrolyte imbalance, endocrine disease, neuromuscular disease or uraemia.
The following observations were made in both group:
1. Incidence and intensity of fasciculations.
2. Serum potassium changes. For this, venous blood samples were collected prior to induction and after complete muscular relaxation was achieved.
3. Any change in the cardiac rhythm or blood pressure.
4. Inquiries were made regarding the post-operative muscle pains by visiting the patients on the day of surgery and on the 2nd post-operative day.
The severity of fasciculations was graded as follows:
1. Minimal: Fine fasciculations confined only to the face, neck and fingers.
2. Moderate: Coarse and wide-spread fasciculations all over the body.
3. Severe: Marked contractions of various muscle groups resulting in gross movements of extremities.
The severity of the post-operative muscle pains was assessed during the post-operative visits to the patients in the evening on the day of surgery and on the next day. The pains were considered severe if the patients complained spontaneously during conversation. Postoperative pain due to surgery was differentiated by finding the site of pain, its relation with respiration or whether it was a generalised body ache suggestive of post-suxamethonium muscle pains.
Muscle pains were considered mild when patients did not complain of bodyache voluntarily but only after direct questioning.
In the self-taming group, 70% of patients did not have any muscle fasciculations at all and 15%, 11% and 4% of patients had minimal, moderate and severe fasciculations respectively [Table - 1]. In the control group, however, 70% patients had severe fasciculations and only 3% patients did not have any.
Muscle pains were absent in 55 out of 75 patients (75%) of the self-taming group, whereas it was absent in only 9 out of 50 (18%) of the control group. In 20 patients of the self-taming group, the muscle pain was only mild but was moderate or severe in 41 out of 50 patients of the control group.
Changes in serum potassium
The change in the serum potassium concentration was between 0 and 0.4 mEq/l in all patients of the self-taming group. Actually, 78% showed a change of only 0 to 0.1 mEq/l. In the control group, however, the change in the serum potassium varied between 0.1 and 1.0 mEq/l and only 4% of patients showed a change of 0 to 0.1 mEq/l [Table - 2].
There were no significant changes in the pulse rate, rhythm and blood pressure when patients of both the groups were compared.
Till to-day, suxamethonium is the relaxant of first choice for endotracheal intubation and for very short operative procedures requiring good muscular relaxation. However, its use is associated with considerable morbidity and it is fatal under certain conditions where a dangerous rise in serum potassium may occur, e.g., spinal cord lesions with paraplegia, tetanus, burns, extensive tissue trauma.,  ,
(1) Administration of suxamethonium leads to marked muscle fasciculations and these asynchronised muscular contractions frequently lead to intense muscle pains on the day after the operation especially in young ambulatory patients. This happens because the threshold concentration for depolarisation reaches in different muscle fibres at different times, leading to a state where one muscle fibre is contracting while the muscle fibre next to it remains relaxed but may contract shortly afterwards; This asynchronous depolarisation and contraction results in a mechanical damage to the muscle cell wall leading to muscle pains and release of potassium from the damaged muscle cello., ,  The occurrence of injury to the muscle cell wall is further substantiated by an elevation of serum creatine phosphokinase levels after administration of suxamethonium.,  Sometimes the injury inflicted may be severe enough leading to myoglobinuria.,
(2) Average rise in serum potassium is 0.5 to 0.7 mEq/l in normal patients. However, the rise may be much more extensive and fatal in patients with spinal cord lesions with paraplegia, extensive burns and extensive tissue trauma. The release of potassium from denervated muscle is more because there is loss of specificity of the motor end plate to acetyl choline and suxamethonium and as a result the whole muscle membrane becomes hypersensitive and more permeable leading to a dangerous rise in serum potassium levels., ,  The risk appears to be maximum from 10-30 days following denervation but is still present upto 6 months after injury. In cases of extensive burns, there is alteration in metabolism which retards the normally rapid reflux of potassium ions back into muscle cells. The most dangerous period is upto 3 weeks after burns. In uraemic patients, even the average rise may prove dangerous.
(3) A rise in the intra-ocular tension of 7-8 mm Hg due to sustained contractions of extra ocular muscles may be dangerous in patients with perforating injuries of the eye.
(4) A rise in the intra-gastric pressure of about 18-20 mm of H2O may lead to vomiting and aspiration, especially in emergency cases with full stomach where intubation is difficult.
Almost all of the side-effects associated with the use of suxamethonium are as a result of extensive asynchronous depolarisation. This results in a mechanical damage to the muscle cell walls which may raise the serum potassium level during induction and give rise to postoperative muscle pains.,  Several preventive methods had been tried but failed to gain popularity due to various drawbacks.
The different methods extensively tried to reduce fasciculations are:
(a) Pre-treatment with a small dose of non-depolarising relaxant (e.g. d-tubocurarine 3 to 5 mg or gallamine triethiodide 20 mg) about 2-3 minutes before administration of suxamethonium. As the two types of block are antagonistic, this method reduces the intensity and duration of muscular relaxation produced by suxamethonium and may make the intubation difficult. A larger than average dose is required for intubation ,,,,,, 
(b) Pre-treatment with lignocaine (2-4 mg/kg i.v.) about 2-3 minutes before induction. There is a likelihood of prolonged suxamethonium apnoea with this method.
(c) Administration of 500 mg of Vitamin C twice daily 24 hours before, on the day of surgery and on the second postoperative day. Though simple, this has not been found much effective.
The present method of "self-taming of succinylcholine-induced fasciculations" is relatively simple and effective in minimising the side effects associated with the conventional use of suxamethonium. The theoretical background of this method is based on the fact that pre-treatment with a small subparalytic dose before the full relaxant dose brings about either induction of neuromuscular desensitisation or accommodation so that the depolarisation achieved by the relaxant dose of suxamethonium may be enough to provide a neuromuscular block without reaching the threshold necessary for electrical excitation of the end plate and muscle membrane. Thus the fasciculations and associated side-effects may be minimised. There are distinct advantages of this method when compared with older techniques.
(1) This technique seems to be more physiological since the neuro-muscular junction is influenced by only one type of muscle relaxant.
(2) The duration of relaxation is not affected.
(3) Greater degree of muscular relaxation is achieved with a relatively small relaxant dose of succinylcholine making intubation very easy.
(4) This method is effective in minimising the incidence of post-operative muscle pains (muscle pains were absent in 75% cases in our study). The rise in serum potassium was either absent or very minimal (0.1 to 0.2 mEq/l) in 78% cases.
The results of our study are encouraging in reducing the morbidity associated with routine surgery. However, its effectiveness in certain conditions, e.g. spinal cord lesion with paraplegia, tetanus, burns and extensive tissue trauma is still to be tried.
Our thanks are due to Dr. A. J. Dhruva, Head and Professor of Anaesthesiology, Seth G. S. Medical College for his encouragement and guidance in carrying out the present study. We are also thankful to Dr. C. K. Deshpande, Dean, Seth G.S. Medical College and K.E.M. Hospital, Bombay for allowing us to publish the data.