The neuroendocrinology of physical injury

The role of N6-methyladenosine modification in rodent models of neuropathic pain: from the mechanism to therapeutic potential

Neuropathic pain (NP) is a common chronic pain condition resulted from lesions or diseases of somatosensory nervous system, but the pathogenesis remains unclear. A growing body of evidence supports the relationship between pathogenesis and N6-methyladenosine (m6A) modifications of RNA. However, studies on the role of m6A modifications in NP are still at an early stage. Elucidating different etiologies is important for understanding the specific pathogenesis of NP. This article provides a comprehensive review on the role of m6A methylation modifications including methyltransferases ("writers"), demethylases ("erasers"), and m6A binding proteins ("readers") in NP models. Further analysis of the pathogenic mechanism relationship between m6A and NP provided novel theoretical and practical significance for clinical treatment of NP.

Patterns of urinary cortisol levels during ontogeny appear population specific rather than species specific in wild chimpanzees and bonobos

Compared with most mammals, postnatal development in great apes is protracted, presenting both an extended period of phenotypic plasticity to environmental conditions and the potential for sustained mother-offspring and/or sibling conflict over resources. Comparisons of cortisol levels during ontogeny can reveal physiological plasticity to species or population specific socioecological factors and in turn how these factors might ameliorate or exaggerate mother-offspring and sibling conflict. Here, we examine developmental patterns of cortisol levels in two wild chimpanzee populations (Budongo and Taï), with two and three communities each, and one wild bonobo population (LuiKotale), with two communities. Both species have similar juvenile life histories. Nonetheless, we predicted that key differences in socioecological factors, such as feeding competition, would lead to interspecific variation in mother-offspring and sibling conflict and thus variation in ontogenetic cortisol patterns. We measured urinary cortisol levels in 1394 samples collected from 37 bonobos and 100 chimpanzees aged up to 12 years. The significant differences in age-related variation in cortisol levels appeared population specific rather than species specific. Both bonobos and Taï chimpanzees had comparatively stable and gradually increasing cortisol levels throughout development; Budongo chimpanzees experienced declining cortisol levels before increases in later ontogeny. These age-related population differences in cortisol patterns were not explained by mother-offspring or sibling conflict specifically; instead, the comparatively stable cortisol patterns of bonobos and Taï chimpanzees likely reflect a consistency in experience of competition and the social environment compared with Budongo chimpanzees, where mothers may adopt more variable strategies related to infanticide risk and resource availability. The clear population-level differences within chimpanzees highlight potential intraspecific flexibility in developmental processes in apes, suggesting the flexibility and diversity in rearing strategies seen in humans may have a deep evolutionary history.

Impact of different intravenous fluids on blood glucose levels in nondiabetic patients undergoing elective major noncardiac surgeries

Background:

Intravenous (IV) fluids are an integral part of perioperative management. Intraoperative hyperglycemia is associated with poor clinical outcomes in patients undergoing major surgeries even in nondiabetics.

Aim:

This study was conducted to observe the effect of different maintenance fluid regimens on intraoperative blood glucose levels in nondiabetic patients undergoing major surgeries under general anesthesia.

Settings and Design:

Randomized double-blind study.

Materials and Methods:

One hundred nondiabetic patients of either sex were divided randomly into two Groups I and II of 50 each undergoing elective major surgeries of more than 90 min duration under general anesthesia. Both groups were given calculated dosage of IV fluids accordingly 4-2-1 formula while Group I was given Ringer lactate (RL) and Group II was given 0.45% dextrose normal saline and potassium chloride 20 mmol/L. Changes in vital parameters, % oxygen saturation, and urine output were monitored at regular intervals. Capillary blood glucose (CBG) was measured half-hourly until end of surgery. If CBG level was more than 150 mg%, then calculated dose of human insulin (CBG/100) was given as IV bolus dose.

Statistical Analysis:

Statistical analysis was done using SPSS 22.0 software (IBM Corporation, Armonk, New York, USA), paired t-test and Chi-square test.

Results:

A significant increase of CBG level and was observed during intraoperative and immediate postoperative period (P < 0.001) in Group II.

Conclusion:

RL solution is probably the alternative choice of IV fluid for perioperative maintenance and can be used as replacement fluid in nondiabetic patients undergoing major surgeries.

Perioperative glycemic status of adult traumatic brain injury patients undergoing craniotomy: a prospective observational study

BACKGROUND

Patients of traumatic brain injury (TBI) may have hyperglycemia and when they undergo craniotomy, hyperglycemia may be exacerbated and worsen outcome. However, epidemiology of perioperative hyperglycemia in these patients is unknown. The epidemiological study has been undertaken to address the correlation between intraoperative blood glucose variability in nondiabetic adult TBI patients undergoing craniotomy with the severity and type of brain trauma and patients' demographic variables.

METHODS

A total of 200 adult nondiabetic patients undergoing emergency craniotomy for TBI were recruited in this prospective single-group observational study. Baseline capillary blood glucose (CBG) measurement was performed immediately before induction of anesthesia and then at half hourly interval until the end of surgery and 1 hour after the end of surgery.

RESULTS

Incidence of at least 1 episode of intraoperative hyperglycemia (CBG≥180 mg/dL) is 20% in patients with TBI during emergency craniotomy. Independent predictors of intraoperative hyperglycemia are severe head injury (Glasgow-Coma score [GCS] <9) and acute subdural hemorrhage. Baseline CBG also correlates with subsequent intraoperative and postoperative CBG.

CONCLUSIONS

Hyperglycemia is common during emergency craniotomy in TBI patients. We recommend routine monitoring of blood glucose in the intraoperative and postoperative period at least in severe head injury patients.

Intraoperative blood glucose levels in nondiabetic patients undergoing elective major surgery under general anaesthesia receiving different crystalloid solutions for maintenance fluid

CONTEXT

The study was undertaken to observe the effect of different maintenance-fluid regimen on intraoperative blood glucose levels in non-diabetic patients undergoing elective major non-cardiac surgery under general anesthesia.

AIMS

To know the intraoperative blood glucose levels.

SETTINGS AND DESIGN

Prospective randomized parallel group study.

SUBJECTS AND METHODS

Two hundred non-diabetic patients (100 in each group) aged between 18 years and 60 years were enrolled for this prospective randomized parallel group study. Group A patients received Ringer's lactate solution and Group B patients received 0.45% sodium chloride with 5% dextrose and 20 mmol/L potassium chloride as maintenance fluid. Capillary blood glucose (CBG) level was measured immediately before initiation of intravenous fluid therapy and thereafter hourly till the end of surgery. If at any time intraoperative CBG was found to be more than or equal to 150 mg/dL calculated dose of human soluble insulin was given as intravenous bolus equal to the amount of CBG/100 units.

STATISTICAL ANALYSIS USED

For comparison of normally distributed variables independent sample t test was done. For rest of the data, i.e., CBG_0, CBG_4 and insulin consumption Mann-Whitney U test was employed.

RESULTS

63% patients in group B developed at least one episode of hyperglycemia CBG ≥ 150 mg/dL) but only 29% in the Group A did so. Insulin consumption was significantly higher in Group B than in Group A to maintain normoglycemia. The relative risk of becoming hyperglycemic in Group B patients is 2.172 (95% CI 1.544 to 3.057). Number needed to harm, i.e., hyperglycemia, in Group B is 2.941 (95% CI 2 to 5).

CONCLUSIONS

We conclude that stress induced-hyperglycemic response in patients undergoing major non-cardiac surgery is common in non-diabetic population. Maintenance-fluid therapy by dextrose containing solution as opposed to Ringer's lactate solution increases the incidence of hyperglycemia. To achieve normoglycemia by intravenous bolus dose of human regular insulin, significantly higher doses are required in patients receiving dextrose containing saline as maintenance fluid.

Neuroendocrine recovery initiated by cognitive behavioral therapy in women with functional hypothalamic amenorrhea: a randomized, controlled trial

OBJECTIVE

To determine whether cognitive behavior therapy (CBT), which we had shown in a previous study to restore ovarian function in women with functional hypothalamic amenorrhea (FHA), could also ameliorate hypercortisolemia and improve other neuroendocrine and metabolic concomitants of in FHA.

DESIGN

Randomized controlled trial.

SETTING

Clinical research center at an academic medical university.

PATIENT(S)

Seventeen women with FHA were randomized either to CBT or observation.

INTERVENTION(S)

CBT versus observation.

MAIN OUTCOME MEASURE(S)

Circulatory concentrations of cortisol, leptin, thyroid-stimulating hormone (TSH), total and free thyronine (T(3)), and total and free thyroxine (T(4)) before and immediately after completion of CBT or observation. (Each woman served as her own control.)

RESULT(S)

Cognitive behavior therapy but not observation reduced cortisol levels in women with FHA. There were no changes in cortisol, leptin, TSH, T(3), or T(4) levels in women randomized to observation. Women treated with CBT showed increased levels of leptin and TSH, but their levels of T(3) and T(4) remained unchanged.

CONCLUSION(S)

In women with FHA, CBT ameliorated hypercortisolism and improved the neuroendocrine and metabolic concomitants of FHA while observation did not. We conclude that a cognitive, nonpharmacologic approach aimed at alleviating problematic attitudes not only can restore ovarian activity but also improve neuroendocrine and metabolic function in women with FHA.

CLINICAL TRIAL REGISTRATION NUMBER

NCT01674426.

Brain development, environment and sex: what can we learn from studying graviperception, gravitransduction and the gravireaction of the developing CNS to altered gravity?

As man embarks on space exploration and contemplates space habitation, there is a critical need for basic understanding of the impact of the environmental factors of space, and in particular gravity, on human survival, health, reproduction and development. This review summarizes our present knowledge on the effect of altered gravity on the developing CNS with respect to the response of the developing CNS to altered gravity (gravireaction), the physiological changes associated with altered gravity that could contribute to this effect (gravitransduction), and the possible mechanisms involved in the detection of altered gravity (graviperception). Some of these findings transcend gravitational research and are relevant to our understanding of the impact of environmental factors on CNS development on Earth.

Nutrition support in the obese, diabetic patient: the role of hypocaloric feeding

PURPOSE OF REVIEW

It has previously been thought that meeting estimated caloric needs with nutrition support improves outcomes in critically ill, obese patients with diabetes. Recent data suggests that intentionally failing to match caloric expenditure may actually result in better outcomes than eucaloric feeding. This review will evaluate recent studies exploring the relationship between caloric intake and outcomes in obese patients with underlying insulin resistance or diabetes.

RECENT FINDINGS

Obese patients who receive 33-70% of their estimated caloric needs during critical illness have better clinical outcomes than patients fed eucalorically. The reasons for this are not clear, however, they do not appear to be due to improved glycemic control. It is possible that caloric restriction acts by improving insulin sensitivity in protein and glucose metabolism, reducing the risk of infection without causing severe hypoglycemia. Patients who are unable to achieve goal-feeding rates have poorer clinical outcomes but this is most likely due to severity of illness rather than caloric intake itself.

SUMMARY

It is better to err on the side of hypocaloric nutrition support in obese, diabetic patients rather than overfeeding. Hypocaloric feeding may result in improved outcomes, however, the optimal duration of hypocaloric nutrition support is not known.

Amenorrhea, pregnancy, and pregnancy outcomes in women following spinal cord injury: a retrospective cross-sectional study

OBJECTIVE

To assess the prevalence of amenorrhea and pregnancy as well as pregnancy outcomes following spinal cord injury (SCI) in women.

METHODS

In this retrospective cross-sectional study, women with SCI were interviewed regarding demographic data, details about the timing and type of SCI they sustained, whether the neurologic deficit was complete or incomplete, and reproductive history. The study was initiated in September 2001 and lasted 3 years. Measures were compared for significance with the level of injury and extent of neurologic deficit using descriptive statistics, analysis of variance, and 2-tailed t tests.

RESULTS

Of 128 women, 53 (41.4%) had postinjury amenorrhea. The amenorrhea was transient in 50 of 53 women. SCI occurred at the mean (+/- SD) age of 27 +/- 9 years. In this group the lesions were at thoracic spine in 35 (66%), cervical spine in 16 (30%), and lumbar spine in 2 (4%). Neurologic deficit was complete in 31 women (58%) and incomplete in 22 (42%). The occurrence of amenorrhea was not influenced by the extent of neurologic deficit. Of 50 women who experienced transient amenorrhea, 10 (20%) became pregnant (6 livebirths, 4 elective terminations). Mean duration of amenorrhea was 7.96 +/- 10.9 months; there was no significant difference between mean duration of amenorrhea in women who got pregnant vs those who did not (6.4 +/- 3.8 months vs 15.8 +/- 30.8 months; P = .34). Pregnancy rate was significantly higher among those who sustained injury at a younger age (21.6 +/- 5.3 years vs 28.3 +/- 9.3 years; P = .033).

CONCLUSIONS

Level of injury did not influence duration of amenorrhea or occurrence of pregnancy. Women who experience transient amenorrhea after SCI may achieve successful pregnancies.

Brewing controversies: Darwinian perspective on the adaptive and maladaptive effects of caffeine and ethanol as dietary autonomic modulators

Ethanol and caffeine are two of the oldest human drugs. Their pervasive integration into the modern human diet may reflect behavioral attempts to correct maladaptations induced by evolutionary displacement of the autonomic system. The dietary adoption of caffeine may parallel the emergence of cognition as an independent basis of competition. Enhancement of the cognitive ability to gather and process information likely evolved as a valuable adjunct to physical behavior in prehistoric fight-or-flight encounters. Caffeine effectively exploits this pre-existing association between adrenergic activity and cognitive readiness, leading to its use in the modern environment where success in competition increasingly depends on cognitive, rather than physical, prowess. Ethanol may have emerged as a dietary means to buffer the maladaptive chronic sympathetic activation and fear response associated with stressful lifestyles and the social phobias associated with the dissolution of kin networks. We explore the health implications of ethanol and caffeine use, with particular attention to their acute and chronic effects on the autonomic axis. The putative protective effects of ethanol in surviving major trauma or reducing inflammation and heart disease may relate to tempering the behavioral and cardiovascular consequences of catastrophic or chronic sympathetic activation. Acute or chronic abuse of ethanol manifests paradoxical pro-adrenergic effects such as tremors and insomnia that may partly represent compensatory responses. Compensatory remodeling may also explain why confirmation of detrimental effects related to caffeine-induced sympathetic activation has proven elusive; indeed, paradoxical pro-vagal benefits may eventually be recognized. Ethanol and caffeine are potential agents that may beneficially expand the dynamic range of the autonomic system. In an environment where the Darwinian value of knowledge has increasingly supplanted that of physical traits, the consumption of caffeine and alcohol may represent both a cause and an effect of modern human evolution.

Androstenetriol improves survival in a rodent model of traumatic shock

Trauma results in activation of the hypothalamic-pituitary-adrenal axis to mediate a cascade of neurohormonal changes as a defensive mechanism. Its prolongation, however, leads to a hypermetabolic, hypoperfused, and immunosuppressed state, setting the stage for subsequent sepsis and organ failure. Androstenetriol (5-androstene-3beta, 7beta, 17betatriol - AET), a metabolite of dehydroepiandrosterone, up-regulates the host immune response markedly, prevents immune suppression and controls inflammation, leading to improved survival after lethal infections by several diverse pathogens and lethal radiation. Such actions may be useful in improving survival from traumatic shock.

HYPOTHESIS

The neurosteroid AET will increase survival following traumatic shock.

METHODS

A combat relevant model of traumatic shock was used. Male Sprague-Dawley rats were anesthetized, catheterized and subjected to soft tissue injury (laparotomy). Animals were allowed to regain consciousness over the next 0.5 h and then bled 40% of their blood volume over 15 min. Forty-five minutes after the onset of hemorrhage animals were randomized to receive either a single subcutaneous dose of AET (40 mg/kg, sc) or vehicle (methylcellulose). Volume resuscitation consisted of l-lactated Ringer's (three times the shed blood volume), followed by packed red blood cells (one-third shed red cell volume). Animals were observed for three days.

RESULTS

A total of 24 animals were studied. Of the 12 animals randomized to receive AET, all (100%) survived compared to 9 of 12 animals (75%) randomized to receive the vehicle (p < 0.05).

CONCLUSION

AET significantly improved survival when administered subcutaneously in a single dose in this rodent model of traumatic shock. Further survival and mechanism studies are warranted.

Can the premises of the spasm of resistance vessel concept permit improvement in the treatment and prevention of ischemic heart disease?

In this communication, the spasm of resistance vessel (S-RV) concept of ischemic heart disease (IHD) and other ischemic will be reviewed and updated, and evidence will be presented that principles of the hypothesis might improve the treatment and prevention of IHD. The S-RV concept provides a different basic pathogenetic framework for IHD, and suggestions for treatment and prevention stem from its different basic conceptualization of this disorder. The concept asserts that S-RV directly induces symptoms in IHD, and this position challenges the accepted pathogenetic mechanism for this disorder, i.e., that symptoms in IHD are due directly to obstructive occlusions of epicardial arteries secondary to coronary artery disease. The S-RV concept avers that ischemia-induced S-RV is a major factor in IHD, and evidence supporting this position is provided. Another major position of the hypothesis is that no-reflow (reduced flow after infarction and severe myocardial ischemia in the absence of infarction) is due to ischemic injury-induced S-RV, and a variety of evidences to support this position are offered.Proposed improvement in the treatment of IHD is based mainly on treating ischemia-induced S-RV. alpha-Adrenergic sympathetic blockade reverses ischemia-induced S-RV, and alpha-adrenergic blockade is suggested as therapy for acute coronary syndromes and to prevent complications of percutaneous coronary interventions. Also, angiotensin-converting enzyme inhibition, which has actions similar to alpha-adrenergic blockade, is also suggested. Proposals for the prevention of IHD are based the prevention of S-RV, and special emphasis is given to preventing exercise- and stress-related IHD.

Dissociation of osmoregulation from plasma arginine vasopressin levels following thermal injury in childhood

Although the syndrome of inappropriate anti-diuretic hormone secretion has been recognised as a complication associated with burn and other trauma in adults, relatively little is known about its incidence in children. The objective of this study was to investigate whether it is a complication associated with burn injury in children. Plasma and urine levels of arginine vasopressin (anti-diuretic hormone), sodium and osmolality were measured in samples collected from 16 burn-injured children admitted to the burns unit of the regional children's hospital. No significant correlations were found between plasma vasopressin and plasma sodium or osmolality levels, but there were significant correlations between plasma vasopressin and urine osmolality, 36 (r=0.74, p=0. 009), 60 (r=0.92, p=0.000) and 84 h (r=0.84, p=0.001) after admission, respectively. There were also significant correlations between plasma sodium and plasma osmolality, 24 (r=0.7, p=0.005), 36 (r=0.57, p=0.04) and 84 h (r=0.84, p=0.004) after admission. The data suggest dissociation between the osmolar control of vasopressin secretion and vasopressin levels after burn injury in children, but do not support the incidence of inappropriate secretion of antidiuretic hormone.

Neuroendocrine responses following graded traumatic brain injury in male adults

In an effort to characterize thyroid, gonadal and adrenal function following neurotrauma, the present study determined serum concentrations of thyroid-stimulating hormone (TSH), total triiodothyronine (T3), thyroxine (T4), testosterone and cortisol over a 7 day period in 31 patients with traumatic brain injury. The study group consisted of eight patients with mild closed head injury (Glasgow Coma Scale--GCS 13-15), 10 patients with extensive penetrating head injury (GCS 4-6) and 13 patients with blast injuries but without direct head trauma. The latter group was included in the study because the development of indirect brain trauma has previously been implicated in blast injuries. Patients with multiple injuries were not included. Following mild injury (GCS 13-15), TSH was increased up until day 3 after injury. T3 levels were elevated on days 1, 5 and 7 after injury while T4 remained unchanged throughout. While testosterone was decreased over only the first 2 days post-trauma, cortisol was increased over these first 2 days after injury. In contrast, following severe penetrating injury (GCS 4-6), there were significant declines in TSH, T3 and testosterone over the 7 day observation period post-trauma. Serum cortisol also declined in these patients between 1-3 days after injury, before increasing again on days 5 and 7 after injury. Following indirect neurotrauma, TSH was slightly decreased immediately after trauma but increased to above normal levels on days 5 and 7 post-trauma. Similarly, T3 initially declined after injury, but then increased to above normal levels between 5 and 7 days after injury. T4 and testosterone remained unchanged over the entire post-traumatic period. Serum cortisol was significantly increased after indirect neurotrauma but only up to day 2 post-trauma. In summary, patients with both direct and indirect traumatic brain injury demonstrated endocrine alterations after trauma, the dynamics of which may be a reflection of the severity of brain damage.

Depression of plasma levels of cytokines and ex-vivo cytokine production in relation to the activity of the pituitary-adrenal axis, in patients undergoing major vascular surgery

The relation between the immune and neuroendocrine response during surgery was studied. In 18 patients undergoing major vascular surgery, circulating interleukin (IL)-1beta and ex-vivo production of IL-1beta and tumour necrosis factor (TNF)-alpha were lower on day 1 after surgery compared to pre-operation values (-14+/-5%, P<0.05; -62+/-9%, P<0.05; and -31+/-54%, P<0.005, respectively). Circulating IL-1 receptor antagonist (IL-1ra) was higher on the 5th day post-operatively compared to pre-operation values (mean +640%+/-400, P<0.05). In a more detailed study in six patients, the ex-vivo production of IL-1beta and TNF-alpha started to decrease at induction of general anaesthesia and dropped to under 10% of initial values at the end of surgery. Circulating IL-1ra and ex-vivo production of IL-1ra started to increase at the end of surgery and remained elevated up to 6 days post-operatively. Plasma antidiuretic hormone (ADH) and adrenocorticotropic hormone (ACTH) increased during surgery, but cortisol remained unchanged. We demonstrate a depression of circulating pro-inflammatory IL-1beta and an increase of circulating anti-inflammatory IL-1ra during surgical stress. The ex-vivo production of IL-1beta and TNF-alpha was suppressed, indicating a downregulation of the production of these cytokines. This parallelled the hormonal reaction with high ADH and ACTH, but not of cortisol, suggesting that glucocorticoid is not the key-factor in downregulation of production and release of pro-inflammatory cytokines.

[Is the metabolic response self-limited in head trauma? Analysis of acute phase proteins and glycemia]

There are many reports supporting a self-limitation mechanism involved with hypermetabolic response after severe cranial injury. It was proposed a study with severe head injury patients, in three stages of the evolution. The first 7 days after admission (moment 1-M1), the second three days latter (M2) and the last 7 days after the first (M3). Among male patients with severe head injury, attended between January 1992 and December 1993 in University Hospital of Botucatu, UNESP, were selected 28 male patients, with Glasgow severity scale between 4 and 6, with pO2 < 70 mm Hg, weighting 60 kg or more. Among these patients, 6 finished the study, including analysis of the excretion of N, acute phase proteins, glycemia, triglycerides and amine nitrogen. During the study there were no changes in nitrogen balance and there was a decrease in protein C-reative. Glycemia tends to fall within two weeks after injury. The authors make some considerations about possible mechanisms involved in brain modulation associated with the period of dependence of hypermetabolism and hypercatabolism after closed brain injury. There are some evidences that the brain responds to head trauma with a gobal non specific way, which tends to be reorganized beyond the first two weeks after lesion. The study does not show any influence of the type and severity of head trauma.

Gynecomastia following spinal cord disorder

Gynecomastia, an excessive development of the mammary glands in men, is a known phenomenon among patients with spinal cord disorder, yet in the last 50 years it has not been fully described in relation to spinal cord disorder. Over a period of 2 years, six patients with spinal cord disorder (4 secondary to a traumatic injury, 1 to decompression sickness, and 1 to transverse myelitis) manifested gynecomastia. The onset of gynecomastia occurred between 1 to 6 months after injury. These patients are presented along with a review of the possible causes for gynecomastia and a suggested workup routine. A clinical examination for the presence of gynecomastia should be performed for every patient with spinal cord disorder and a thorough endocrinological workup should follow to rule out malignancy and reassure the anxious patient undergoing a disruption of his body image.

Time course of the early pituitary-adrenal and metabolic responses to accidental injury

We have made serial measurements of the plasma adrenocorticotrophic hormone (ACTH), cortisol, glucose, lactate, glycerol, nonesterified fatty acid (NEFA), and beta-hydroxybutyrate concentrations in 14 recently injured patients. We took 6 to 9 blood samples at about 20-minute intervals from each patient within the first 3 hours after accidental injury of moderate severity (Injury Severity Score of 9 to 13). Plasma ACTH varied greatly both with time and between patients; in the majority, it fell throughout the sampling period and in the others, the pattern varied. The changes in plasma cortisol were mostly appropriate to those in ACTH. Plasma glucose and glycerol did not change systematically with time. In contrast, plasma lactate fell, and plasma NEFA, beta-hydroxybutyrate, and the NEFA:glycerol ratio rose, throughout the sampling period. Analysis of variance for these data showed that time after injury made a contribution that was highly significant, although smaller than that arising from differences between patients.