Propranolol in the treatment of thyrotoxicosis by subtotal thyroidectomy.

Subtotal thyroidectomy was performed in 40 patients with thyrotoxicosis in whom propranolol alone was used as preparation for surgery. Propranolol was given orally in a dose of 40 mg every 6 h for a mean preoperative period of 17 days (range 4-60 days) and continued for seven days after operation. The mean +/- SE blood loss at operation was only 160 +/- 20 ml. The period of follow-up was from three to nine months. Recurrent thyrotoxicosis has not occurred in any patient. Low levels of total serum triiodothyronine (T3) and total serum thyroxine (T4) were observed in the early postoperative weeks in some patients and were associated with symptoms of mild hypothyroidism, but by six months in the presence of a raised serum thyrotropin (TSH) the thyroid hormone levels returned to normal. Permanent hypothyroidism developed in only two patients. Despite normal or low total serum T3 and T4 levels, the TSH response to thyrotropin-releasing hormone (TRH) was absent in all patients one week after operation. At four weeks and at eight weeks, the response was absent or sub-normal in 70% and 20% of the patients respectively, indicating a delay in the recovery of the hypothalamo-pituitary axis previously exposed to high levels of T3 and T4. It is considered that subtotal thyroidectomy for thyrotoxicosis in patients prepared with propranolol is an acceptable procedure which has some advantages over the conventional preparation with carbimazole and potassium iodide, not the least of which are the potential reduction in preparation time, the more flexible timing of operation, and the reduced operative blood loss.

Coupling of cardiac and locomotor rhythms.

The pressure within exercising skeletal muscle rises and falls rhythmically during normal human locomotion, the peak pressure reaching levels that intermittently impede blood flow to the exercising muscle. Speculating that a reciprocal relationship between the timing of peak intramuscular and pulsatile arterial pressures should optimize blood flow through muscle and minimize cardiac load, we tested the hypothesis that heart rate becomes entrained with walking and running cadence at some locomotion speeds, by means of electrocardiography and an accelerometer to provide signals reflecting heart rate and cadence, respectively. In 18 of 25 subjects, 1:1 coupling of heart and step rates was present at one or more speeds on a motorized treadmill, generally at moderate to high exercise intensities. To determine how exercise specific this phenomenon is, and to refute the competing hypothesis that coupling is due to vertical accelerations of the heart during locomotion, we had 12 other subjects cycle on an electronically braked bicycle ergometer. Coupling was found between heart rate and pedaling frequency in 10 of them. Cardiac-locomotor coupling appears to be a normal physiological phenomenon, and its identification provides a fresh perspective from which to study endurance.

Locomotor-respiratory coupling during wheelchair propulsion.

Visceral movement due to impact loading is believed to play a role in the locomotor-respiratory coupling (LRC) that has been detected in a number of mammalian species. In the bird and bat species in which LRC has been described, the effect of the wing muscles on the timing of respiration appears to be a dominant influence. To test the hypothesis that LRC occurs in humans propelling wheelchairs (where there is no impact loading and the arms are used for locomotion), we studied 10 wheelchair athletes on a motorized treadmill at three speeds. Each subject's data were analyzed by spectral analysis (based on the fast Fourier transform), which detected apparent LRC (rates within 1% of a single-digit integer ratio) in 12 (40%) of the 30 test settings. However, a control analysis, in which each subject's arm-thrust rates were compared with another subject's breathing rates, revealed apparent (but false) coupling in 8 (27%), not significantly less often (using the chi 2 test). These findings appear to refute the hypothesis that LRC occurs during wheelchair propulsion. These data are consistent with the theory that the visceral piston is important to LRC and suggest that rhythmic arm movements are insufficient to induce the phenomenon in this setting.

Failure of accentuated vertical body movements to induce cardiac-locomotor coupling.

Cardiac-locomotor coupling (CLC) has been reported during a variety of rhythmic human activities. One reason postulated for such coupling is that axial movements of the viscera during some activities (the "visceral piston") may enhance expulsion of blood from the heart; if so, accentuated vertical movements of the body should provide a powerful stimulus to coupling. To test this hypothesis, we studied 20 subjects hopping and 20 others skipping rope for greater than or equal to 10 min while electrocardiographic and force-platform signals were recorded, from which we derived the subjects' exercise and heart rates. The incidence and intensity of apparent coupling in the test subjects were compared with those of cross-over controls, where the heart rate of each subject was related to the hopping or skipping rate of a matched subject. Ratios consistent with coupling were seen in 10 (50%) hopping subjects under test conditions and in 13 (65%) under control conditions; among skipping subjects, the incidences were 11 (55%) and 10 (50%). In neither group of subjects was the difference in the incidences or the intensities of apparent CLC statistically significant. Our failure to detect CLC while our subjects were hopping or skipping suggests that the visceral piston is unimportant to the CLC phenomenon.

Effect of limited knee-flexion range on peak hip moments of force while transferring from sitting to standing.

The hypothesis that limiting the knee-flexion range increases the peak hip-extension moment while transferring from sitting to standing was tested by filming (100 fps) ten normal human volunteers. With the knees flexed 105 degrees from full extension (0 degrees) the mean (+/- 1 S.D.) peak hip-extension moment was 142 (+/- 37) Nm. With the knees flexed only 75 degrees subjects threw their arms and trunks forward to a greater extent, with a peak moment of 253 (+/- 65) Nm (p less than 0.0001). If the peak moments rise to a similar degree in patients with arthritis and limited knee-flexion range, they may accelerate hip joint damage or the loosening of hip endoprostheses.

The influence of foot position on standing balance.

To test the hypothesis that variations in foot position would significantly affect standing balance, we studied ten normal subjects on a Kistler force platform which measured the travel and center of pressure displacement. With the feet together there was substantially more mediolateral (ML) travel than with the axes of the feet 15, 30 or 45 cm apart and the mean ML position of the center of pressure was displaced toward the right; there was no consistent effect on anteroposterior (AP) travel or position. As the right foot was placed 10 and 30 cm forward or back, the least amount of ML and AP travel occurred with the feet even or at 10 cm either direction; the mean AP and ML position moved toward the foot which was placed more posteriorly. Of the five foot angles ranging from toes-out 45 degrees to toes-in 45 degrees, the extent of ML and AP travel was lowest in the toes-out 25 degrees position and greatest in the toes-in 45 degrees position; the mean AP and ML position was farthest forward and to the right with toes-in 45 degrees. These findings have implications for the prosthetic replacement of the lower limbs, sports, ergonomics and postural sway studies.

The effect of locomotion speed on the anterior tibial intramuscular pressure of normal humans.

We examined the hypothesis that anterior tibial intramuscular pressure increases with the speed of locomotion. A solidstate pressure transducer was placed near the tip of an intramuscular fluid-filled catheter and each of ten normal subjects walked, jogged and ran barefoot, at 1.5, 2.5 and 3.5 m s-1 respectively, on a treadmill to which they had been previously familiarized. The pressure signals during ten gait cycles from each subject were sampled at 600 Hz and were averaged at each speed. The peak pressures increased in magnitude as a function of increasing locomotion speed, while the mean pressure remained constant.

Coupling between cardiac and locomotor rhythms: the phase lag between heart beats and pedal thrusts.

During some rhythmic exercises, the heart and exercise rates may become coupled (be within 1% of each other). If the intraarterial and skeletal intramuscular pressure cycles were reciprocal, blood flow to exercising muscle should be maximized and cardiac load minimized. In this study the authors tested the hypothesis that, while coupling is present, the phase lag between the pedaling and cardiac contraction cycles is consistent and appropriate. Twenty-seven subjects pedaled, at a frequency natural to them, on an electronically braked bicycle ergometer that held the power output constant regardless of pedaling rate. To assess the phase lag between pedal thrust (two per revolution) and heart beat, pedal-gated plots of the electrocardiography signal were generated throughout the most coupled five-minute work load for each of the 9 subjects in whom the rates were within 1% of each other for at least two consecutive four-second samples taken every fifteen seconds. During this interval of thirty-seconds in which the rates were within 1% of each other, the phase lag of most subjects gradually lengthened and shortened and there was considerable variation among subjects, refuting the authors' hypothesis. The results of this study illustrate the importance of beat-by-beat analysis when studying coupling phenomena. The preliminary assumption, that the coupling between cardiac and locomotor rhythms during cycling was on the basis of a single ischemic muscle group, has apparently been disproven.

The effect of knee-flexion angle on wheelchair turning.

The increasingly popular hyperflexed knee-flexion angle was evaluated to determine its effects on wheelchair turning. Twenty able-bodied subjects were tested comparing the effect of full knee extension and full knee flexion on a number of parameters. We empirically measured the angular velocity of subjects spinning 720 degrees in place, subjects' perceived ease of wheelchair turning, the overall length of the wheelchair, the anteroposterior position of the center of mass (COM), rolling resistance, turning resistance and rear-wheel traction. The combined moment of inertia of the wheelchair and system was modeled. We found that, in comparison with full extension, fully flexing the knees increased angular velocity by 40% and was perceived to be 66% easier by subjects. Overall length decreased by 39%, COM moved rearward 38%, rolling and turning resistance decreased by 21% and 17% respectively, rear-wheel traction increased by 12% and moment of inertia decreased by 42%. All empirically tested parameters were statistically significant (p<0.007). We conclude that the knee-flexion angle has a significant effect on wheelchair turning. The implications of these findings for wheelchair design and prescription will need to be validated on actual wheelchair users and for smaller increments in knee-flexion range.

Wheelchair stability: effect of body position.

When a wheelchair user reaches and leans, the static stability decreases in the direction of the lean and increases in the opposite direction. The purpose of this study was to determine the extent of this effect. We studied 21 nondisabled subjects in a representative wheelchair, measuring the static forward, rear, and lateral stability on a tilting platform. Reaching and leaning away from the tip added stability, with mean increases ranging from 9.1% to 124.3% of the neutral-position values, whereas reaching and leaning toward the tip reduced stability, with mean decreases ranging from 25.2% to 52.3% (p < 0.0001). The stability range ("away" minus "toward") varied from 52.4% to 149.5%. Reaching forward had a greater effect on stability than did reaching back or to the side. Wheelchair users with the ability to control their body positions can profoundly affect the stability of their wheelchairs, a factor that should be considered in wheelchair selection and training.

Rectal examination in patients with pain in the right lower quadrant of the abdomen.

OBJECTIVE: To determine whether rectal examination provides any diagnostic information in patients admitted to hospital with pain in the right lower quadrant of the abdomen. DESIGN: Casualty officer or surgical registrar recorded symptoms and signs on admission on detailed forms. Final diagnosis was noted on discharge from hospital. SETTING: District general hospital. PATIENTS: 1204 Consecutive patients admitted to hospital with pain in the right lower quadrant of the abdomen as their major complaint; 1028 had a rectal examination on admission. MAIN OUTCOME MEASURES: Odds ratio for each symptom and sign related to final diagnosis. Results of multiple logistic regression analysis for acute appendicitis. RESULTS: Right sided rectal tenderness, present in 309 of those examined, was more common in patients with acute appendicitis (odds ratio 1.34, p less than 0.05). This odds ratio was considerably less than that for other clinical signs--namely, tenderness in the right lower quadrant (odds ratio 5.09), rebound tenderness (3.34), guarding (3.07), and muscular rigidity in the abdomen (5.03). In the logistic regression analysis of patients with acute appendicitis, when allowance was made for the presence or absence of rebound tenderness, rectal tenderness on the right lost its significance. Six patients had masses palpable rectally, of which three were palpable on abdominal examination; the other three patients had acute appendicitis. No other unexpected diagnoses were established, and no useful additional diagnostic information was obtained by routine rectal examination. CONCLUSION: If patients presenting with pain in the right lower quadrant of the abdomen are tested for rebound tenderness then rectal examination does not give any further diagnostic information.

Cardiac-locomotor coupling while finger tapping.

Coupling between cardiac and locomotor rhythms has been identified while people walk, run, hop and cycle at cadences natural to them. To test the hypothesis that cardiac-locomotor coupling occurs during finger tapping, we studied 20 normal subjects tapping a telegraph key at a comfortable rate for 10 min. 15 subjects (75%) coupled significantly at one or more single-digit integer ratio (heart/tapping rate), the most common of which was 1:2. Such coupling should be considered a potentially confounding variable when studying finger tapping in subjects with disease or medication affecting heart rate. Also, the identification of coupling during the repetitive activity of small upper-extremity muscles suggests that neither increases in cardiac load nor impact-loading, two suggested explanations for why coupling occurs, are necessary for the phenomenon.

Cardiac-locomotor coupling while finger tapping: Part II. A cross-over control study.

Cardiac-locomotor coupling (CLC) has been reported by us while people finger tap at cadences natural to them. Since then, we have developed a simple cross-over control strategy in which the heart rate of one subject is related to the finger-tapping rate of another. Of the 20 normal subjects previously studied while tapping a telegraph key at a comfortable rate for 10 min., reevaluation of their data showed that 9 (45%) and 4 (20%) of them, under test and control conditions, respectively, appeared to couple at a single-digit integer ratio. Neither the incidence nor the intensity of apparent CLC under the two conditions was significantly different. Raster plots of the most tightly related rates gave no evidence of phase locking. These results have two implications. First, previously published reports on CLC (and other entrainment phenomena) should be interpreted with caution, and cross-over controls should be considered in future research. Second, the absence of CLC during finger tapping suggests that CLC may only be functionally significant during exercise of large muscle groups (e.g., by minimization of cardiac afterload) or when impact-loading occurs (e.g., by enhancing cardiac ventricular emptying.

Visualizing the uncertainty in the relationship between seasonal average climate and malaria risk.

Around $1.6 billion per year is spent financing anti-malaria initiatives, and though malaria morbidity is falling, the impact of annual epidemics remains significant. Whilst malaria risk may increase with climate change, projections are highly uncertain and to sidestep this intractable uncertainty, adaptation efforts should improve societal ability to anticipate and mitigate individual events. Anticipation of climate-related events is made possible by seasonal climate forecasting, from which warnings of anomalous seasonal average temperature and rainfall, months in advance are possible. Seasonal climate hindcasts have been used to drive climate-based models for malaria, showing significant skill for observed malaria incidence. However, the relationship between seasonal average climate and malaria risk remains unquantified. Here we explore this relationship, using a dynamic weather-driven malaria model. We also quantify key uncertainty in the malaria model, by introducing variability in one of the first order uncertainties in model formulation. Results are visualized as location-specific impact surfaces: easily integrated with ensemble seasonal climate forecasts, and intuitively communicating quantified uncertainty. Methods are demonstrated for two epidemic regions, and are not limited to malaria modeling; the visualization method could be applied to any climate impact.

Anterior urethral injuries.

Seventeen patients are reviewed who presented at the Birmingham Accident Hospital over a 20-year period with injuries to the anterior urethra. Fourteen of the injuries resulted from isolated direct blows to the perineum, while 3 were associated with multiple injuries. The clinical features and management of these patients are discussed in conjunction with a review of the relevant literature. A protocol for the management of this type of injury is outlined.