Annals of the Royal College of Surgeons of England (1990) vol. 72, 291-295
Postoperative muscle strength Jane McCue Surgical Registrar
FRCS
Di Newham PhD Research Fellow, Department of Medicine
Departments of Surgery and Medicine, The Rayne Institute, University College London
Key words: Muscle function; Surgery; Convalescence
This study investigates the role of motivation in voluntary strength measurements during the postoperative period. Thirty patients underwent surgery which was deemed minor, intermediate or major in severity. Before operation and on the 4th postoperative day measurement of grip strength, maximal voluntary and maximal tetanic (stimulated) contraction of adductor pollicis and assessment of mood were recorded. These investigations were also repeated on the 7th postoperative day in those who had major surgery. No patient had postoperative complications. Minor surgery had no influence on any of the values. Those who underwent major surgery showed significant reductions in grip strength, maximal voluntary contraction and mood; however, maximal tetanic contraction was unaffected. The results in the intermediate group were similar to the major group, although mood depression was less marked. Real strength of a hand muscle appears to be unaltered even by major surgery, but voluntary muscle force is decreased by intermediate and major surgery, and correlates with the patient's subjective state of well-being.
There have been numerous studies designed to investigate the effect of surgery on human muscle strength (1-9). The majority have found strength to be reduced in the immediate postoperative period (1,4-7,9). In these cases strength has been measured from voluntary contractions. It has been shown that the majority of medical patients with myopathic disease can fully activate their muscles at will (10) to produce good correlation between voluntary and stimulated muscle contraction. However, these patients generally feel well and free from discomfort, thus the results cannot be extrapolated to the postoperative situation. In the initial postoperative period patients often feel unwell and it is possible that voluntary strength measurements recorded at this time might be affected by
Correspondence to: Miss J L McCue, Professorial Surgical Unit, St Bartholomew's Hospital, West Smithfield, London ECIA 7BE
reduction in the central drive necessary for full activation, rather than representative of underlying loss of muscle force or bulk. When muscles are stimulated through their motor nerves, forces are generated which closely approximate those from maximal voluntary contractions (11), whilst the effects of motivation and central drive are eliminated. The purpose of this study was to investigate the role of these factors in voluntary strength measurements in the 1st postoperative week. We have measured the strength of both voluntary and electrically stimulated muscle contraction in patients who have undergone surgery which has been minor, intermediate and major in nature. a
Methods Patients A total of 30 patients was studied. They were divided into three equal groups according to the magnitude of the operation undergone, ie minor, intermediate or major. There were no postoperative problems. Details of the patients in each group can be seen in Table I. All tests were carried out 1 or 2 days before surgery and again 4 days after surgery. The tests are repeated on the 7th postoperative day on those patients who were still in hospital. All patients who underwent minor or intermediate surgery had been discharged by the 7th day; thus, only those who had undergone major surgery were tested on that occasion. Grip strength The patients performed three maximal grip movements on a dynamometer using the left hand. The upper arm was fully adducted, the elbow flexed to a right-angle and the hand held in mid-pronation with the wrist in the neutral position. The best of three attempts was recorded.
292
Jf McCue and D Newham Table I. Details of patients and surgical procedures Minor surgery
Age
58 41 24 46 42 50 45 38 51 42
Sex
Intermediate surgery
Procedure
Major surgery
Age
Sex
24 49 45 52 67 23 22 31 36 54
F Cholecystectomy F Cholecystectomy F Cholecystectomy M Cholecystectomy F Cholecystectomy M Vagotomy M Vagotomy M Vagotomy M Vagotomy F Close colostomy Mean age 40.3 years SEM 4.9
M Herniorrhaphy M Herniorrhaphy M Herniorrhaphy M Herniorrhaphy M Herniorrhaphy M Herniorrhaphy M Herniorrhaphy M Herniorrhaphy M Herniorrhaphy M Herniorrhaphy Mean age 43.7 years SEM 2.9
Procedure
Adductor pollicis strength Force was recorded from both voluntary and electrically stimulated contractions of the adductor pollicis muscle using the technique described by Merton (12) and later modified by Edwards (13). The fingers of the left hand were immobilised in supination. The thumb was pulled into slight abduction and restrained by an inextensible strap which was attached to a strain gauge. The signal from the strain gauge was amplified and displayed on a UV recorder. For voluntary force testing the patients were asked to make three maximal contractions, taking care not to flex the thumb and thus bring in muscles other than the adductor pollicis. The best of three attempts was measured and recorded as the maximal voluntary contraction force (MVC). The muscles were then stimulated via the ulnar nerve at the wrist, using pulses of 50 ,us duration. The electromyograph (EMG) was recorded through surface electrodes and displayed on the UV recorder simultaneously with the force signal. Stimulation at 1 Hz was
Age
66 71 56 64 68 67 64 55 63 34
Sex
Procedure
M Hemigastrectomy F Gastrectomy F Gastrectomy M Gastrectomy M Hemicolectomy F Hemicolectomy M Hemicolectomy M Colectomy F Colectomy F Gastroplasty Mean age 60.9 years SEM 3.4
used to locate the optimal electrode position and then to determine the supramaximal voltage. The nerve was then stimulated at this voltage at a frequency of 100 Hz for approximately 2 s. The EMG signal was used to ensure that the signal was maintained. Any tests in which supramaximal stimulation was not achieved or maintained have not been included in the results. The force generated by stimulation at 100 Hz was recorded as the maximal tetanic contraction force (MTC). Mood state
An assessment of the patient's subjective well-being was recorded on a visual analogue scale. The patients were presented with an unmarked, horizontal 10 cm line. They were told that 'the left end of the line represents the worst you could feel and the right end the best'. They were asked to mark the line at a site to indicate their current overall mood. The position of the patient's mark was measured from the left in centimetres so that the lowest mood would score 0 and the highest 10.
Table II. Results of muscle forces before and after surgery in the three groups. All forces in Newtons. Mood on analogue scale with 0 as worst and 10 as best Grip strength
Minor Mean SEM Intermediate Mean SEM
MVC force
MTC force
Mood
Preop
+Day 4
Preop
+Day 4
Preop
+Day 4
Preop
+Day 4
397.6 25.3
374.2 35.4
70.8 2.1
69.1 2.5
59.4 3.4
58.2 3.3
6.2 0.5
6.5 0.8
345.8 39.2
299.9* 39.6
65.3 8.4
55.4t
57.5 7.8
55.9
8.1
7.7
6.7 0.7
5.2 0.7
291.0 26.0
237.0O: 27.6
54.5 5.4
48.9* 5.7
49.1 4.7
50.8 5.0
6.4 0.4
3.0: 0.5
Major Mean SEM
Significantly different from paired preoperative values * P
Postoperative muscle strength Jane McCue Surgical Registrar
FRCS
Di Newham PhD Research Fellow, Department of Medicine
Departments of Surgery and Medicine, The Rayne Institute, University College London
Key words: Muscle function; Surgery; Convalescence
This study investigates the role of motivation in voluntary strength measurements during the postoperative period. Thirty patients underwent surgery which was deemed minor, intermediate or major in severity. Before operation and on the 4th postoperative day measurement of grip strength, maximal voluntary and maximal tetanic (stimulated) contraction of adductor pollicis and assessment of mood were recorded. These investigations were also repeated on the 7th postoperative day in those who had major surgery. No patient had postoperative complications. Minor surgery had no influence on any of the values. Those who underwent major surgery showed significant reductions in grip strength, maximal voluntary contraction and mood; however, maximal tetanic contraction was unaffected. The results in the intermediate group were similar to the major group, although mood depression was less marked. Real strength of a hand muscle appears to be unaltered even by major surgery, but voluntary muscle force is decreased by intermediate and major surgery, and correlates with the patient's subjective state of well-being.
There have been numerous studies designed to investigate the effect of surgery on human muscle strength (1-9). The majority have found strength to be reduced in the immediate postoperative period (1,4-7,9). In these cases strength has been measured from voluntary contractions. It has been shown that the majority of medical patients with myopathic disease can fully activate their muscles at will (10) to produce good correlation between voluntary and stimulated muscle contraction. However, these patients generally feel well and free from discomfort, thus the results cannot be extrapolated to the postoperative situation. In the initial postoperative period patients often feel unwell and it is possible that voluntary strength measurements recorded at this time might be affected by
Correspondence to: Miss J L McCue, Professorial Surgical Unit, St Bartholomew's Hospital, West Smithfield, London ECIA 7BE
reduction in the central drive necessary for full activation, rather than representative of underlying loss of muscle force or bulk. When muscles are stimulated through their motor nerves, forces are generated which closely approximate those from maximal voluntary contractions (11), whilst the effects of motivation and central drive are eliminated. The purpose of this study was to investigate the role of these factors in voluntary strength measurements in the 1st postoperative week. We have measured the strength of both voluntary and electrically stimulated muscle contraction in patients who have undergone surgery which has been minor, intermediate and major in nature. a
Methods Patients A total of 30 patients was studied. They were divided into three equal groups according to the magnitude of the operation undergone, ie minor, intermediate or major. There were no postoperative problems. Details of the patients in each group can be seen in Table I. All tests were carried out 1 or 2 days before surgery and again 4 days after surgery. The tests are repeated on the 7th postoperative day on those patients who were still in hospital. All patients who underwent minor or intermediate surgery had been discharged by the 7th day; thus, only those who had undergone major surgery were tested on that occasion. Grip strength The patients performed three maximal grip movements on a dynamometer using the left hand. The upper arm was fully adducted, the elbow flexed to a right-angle and the hand held in mid-pronation with the wrist in the neutral position. The best of three attempts was recorded.
292
Jf McCue and D Newham Table I. Details of patients and surgical procedures Minor surgery
Age
58 41 24 46 42 50 45 38 51 42
Sex
Intermediate surgery
Procedure
Major surgery
Age
Sex
24 49 45 52 67 23 22 31 36 54
F Cholecystectomy F Cholecystectomy F Cholecystectomy M Cholecystectomy F Cholecystectomy M Vagotomy M Vagotomy M Vagotomy M Vagotomy F Close colostomy Mean age 40.3 years SEM 4.9
M Herniorrhaphy M Herniorrhaphy M Herniorrhaphy M Herniorrhaphy M Herniorrhaphy M Herniorrhaphy M Herniorrhaphy M Herniorrhaphy M Herniorrhaphy M Herniorrhaphy Mean age 43.7 years SEM 2.9
Procedure
Adductor pollicis strength Force was recorded from both voluntary and electrically stimulated contractions of the adductor pollicis muscle using the technique described by Merton (12) and later modified by Edwards (13). The fingers of the left hand were immobilised in supination. The thumb was pulled into slight abduction and restrained by an inextensible strap which was attached to a strain gauge. The signal from the strain gauge was amplified and displayed on a UV recorder. For voluntary force testing the patients were asked to make three maximal contractions, taking care not to flex the thumb and thus bring in muscles other than the adductor pollicis. The best of three attempts was measured and recorded as the maximal voluntary contraction force (MVC). The muscles were then stimulated via the ulnar nerve at the wrist, using pulses of 50 ,us duration. The electromyograph (EMG) was recorded through surface electrodes and displayed on the UV recorder simultaneously with the force signal. Stimulation at 1 Hz was
Age
66 71 56 64 68 67 64 55 63 34
Sex
Procedure
M Hemigastrectomy F Gastrectomy F Gastrectomy M Gastrectomy M Hemicolectomy F Hemicolectomy M Hemicolectomy M Colectomy F Colectomy F Gastroplasty Mean age 60.9 years SEM 3.4
used to locate the optimal electrode position and then to determine the supramaximal voltage. The nerve was then stimulated at this voltage at a frequency of 100 Hz for approximately 2 s. The EMG signal was used to ensure that the signal was maintained. Any tests in which supramaximal stimulation was not achieved or maintained have not been included in the results. The force generated by stimulation at 100 Hz was recorded as the maximal tetanic contraction force (MTC). Mood state
An assessment of the patient's subjective well-being was recorded on a visual analogue scale. The patients were presented with an unmarked, horizontal 10 cm line. They were told that 'the left end of the line represents the worst you could feel and the right end the best'. They were asked to mark the line at a site to indicate their current overall mood. The position of the patient's mark was measured from the left in centimetres so that the lowest mood would score 0 and the highest 10.
Table II. Results of muscle forces before and after surgery in the three groups. All forces in Newtons. Mood on analogue scale with 0 as worst and 10 as best Grip strength
Minor Mean SEM Intermediate Mean SEM
MVC force
MTC force
Mood
Preop
+Day 4
Preop
+Day 4
Preop
+Day 4
Preop
+Day 4
397.6 25.3
374.2 35.4
70.8 2.1
69.1 2.5
59.4 3.4
58.2 3.3
6.2 0.5
6.5 0.8
345.8 39.2
299.9* 39.6
65.3 8.4
55.4t
57.5 7.8
55.9
8.1
7.7
6.7 0.7
5.2 0.7
291.0 26.0
237.0O: 27.6
54.5 5.4
48.9* 5.7
49.1 4.7
50.8 5.0
6.4 0.4
3.0: 0.5
Major Mean SEM
Significantly different from paired preoperative values * P
