HEMODYNAMIC AND IMMUNE CONSEQUENCES OF OPIATE ANALGESIA AFTER TRAUMA/HEMORRHAGE

Effects of ketamine analgesia on cardiorespiratory responses and survival to trauma and hemorrhage in rats

Ketamine is the recommended analgesic on the battlefield for soldiers with hemorrhage, despite a lack of supportive evidence from laboratory or clinical studies. Hence, this study determined the effects of ketamine analgesia on cardiorespiratory responses and survival to moderate (37% blood volume; n = 8/group) or severe hemorrhage (50% blood volume; n = 10/group) after trauma in rats. We used a conscious hemorrhage model with extremity trauma (fibular fracture + soft tissue injury) while measuring mean arterial pressure (MAP), heart rate (HR), and body temperature (T_b) by telemetry, and respiration rate (RR), minute volume (MV), and tidal volume (TV) via whole body plethysmography. Male rats received saline (S) or 5.0 mg/kg ketamine (K) (100 µL/100 g body wt) intra-arterially after trauma and hemorrhage. All rats survived 37% hemorrhage. For 50% hemorrhage, neither survival times [180 min (SD 78) vs. 209 min (SD 66)] nor percent survival (60% vs. 80%) differed between S- and K-treated rats. After 37% hemorrhage, K (compared with S) increased MAP and decreased T_b and MV. After 50% hemorrhage, K (compared with S) increased MAP but decreased HR and MV. K effects on cardiorespiratory function were time dependent, significant but modest, and transient at the analgesic dose given. K effects on T_b were also significant but modest and more prolonged. With the use of this rat model, our data support the use of K as an analgesic in injured, hypovolemic patients.NEW & NOTEWORTHY Ketamine administration at a dose shown to alleviate pain in nonhemorrhaged rats with extremity trauma had only modest and transient effects on multiple aspects of cardiorespiratory function after both moderate (37%) and severe (50%) traumatic hemorrhages. Such effects did not alter survival.

Fentanyl impairs but ketamine preserves the microcirculatory response to hemorrhage

BACKGROUND

Peripheral vasoconstriction is the most critical compensating mechanism following hemorrhage to maintain blood pressure. On the battlefield, ketamine rather than opioids is recommended for pain management in case of hemorrhage, but effects of analgesics on compensatory vasoconstriction are not defined. We hypothesized that fentanyl impairs but ketamine preserves the peripheral vasoconstriction and blood pressure compensation following hemorrhage.

METHOD

Sprague-Dawley rats (11-13 weeks) were randomly assigned to control (saline vehicle), fentanyl, or ketamine-treated groups with or without hemorrhage (n = 8 or 9 for each group). Rats were anesthetized with Inactin (i.p. 10 mg/100 g), and the spinotrapezius muscles were prepared for microcirculatory observation. Arteriolar arcades were observed with a Nikon microscope, and vessel images and arteriolar diameters were recorded by using Nikon NIS Elements Imaging Software (Nikon Instruments Inc. NY). After baseline perimeters were recorded, the arterioles were topically challenged with saline, fentanyl, or ketamine at concentrations relevant to intravenous analgesic doses to determine direct vasoactive effects. After arteriolar diameters returned to baseline, 30% of total blood volume was removed in 25 minutes. Ten minutes after hemorrhage, rats were intravenously injected with an analgesic dose of fentanyl (0.6 μg/100 g), ketamine (0.3 mg/100 g), or a comparable volume of saline. For each drug or vehicle administration, the total volume injected was 0.1 mL/100 g. Blood pressure, heart rate, and arteriolar responses were monitored for 40 minutes.

RESULTS

Topical fentanyl-induced vasodilation (17 ± 2%), but ketamine caused vasoconstriction (-15 ± 4%, p < 0.01). Following hemorrhage, intravenous ketamine did not affect blood pressure or respiratory rate, while fentanyl induced a slight and transient (<5 minutes, p = 0.03 vs. saline group) decrease in blood pressure, with a profound and prolonged suppression in respiratory rate (>10 minutes, with a peak inhibition of 57 ± 8% of baseline, p < 0.01). The compensatory vasoconstriction observed after hemorrhage was not affected by ketamine treatment. However, after fentanyl injection, although changes in blood pressure were transiently present, arteriolar constriction to hemorrhage was absent and replaced with a sustained vasodilation (78 ± 25% to 36 ± 22% of baseline during the 40 minutes after injection, p < 0.01).

CONCLUSION

Ketamine affects neither systemic nor microcirculatory compensatory responses to hemorrhage, providing preclinical evidence that ketamine may help attenuate adverse physiological consequences associated with opioids following traumatic hemorrhage. Microcirculatory responses are more sensitive than systemic response for evaluation of hemodynamic stability during procedures associated with pain management.

A novel rat model of extremity trauma for prehospital pain management research

BACKGROUND

Pain management is important in prehospital care of patients with extremity trauma (ET). The goal of this study was to establish a rat model of ET for prehospital pain research and validate it using pain behaviors and analgesics.

METHODS

Rats were anesthetized using isoflurane, and ET was induced in one hindlimb via clamping retrofemoral tissues for 30 seconds, followed by closed fibula fracture. Rats regained consciousness after ET. Pain responses in the injured hindlimb to thermal hyperalgesia (paw withdrawal latency [PWL]), mechanical allodynia (paw withdrawal pressure [PWP]), and weight bearing (WB) were determined before and 90 minutes after ET. Morphine (2 mg/kg), fentanyl (10 μg/kg), sufentanil (1 μg/kg), ketamine (5 mg/kg), or vehicle (saline) were then administered via intravenous (i.v.) injection, followed by PWL, PWP, and WB assessments at 10 minutes, 40 minutes, 80 minutes, and 120 minutes after analgesia.

RESULTS

After ET, PWL, PWP, and WB were significantly decreased by 61 ± 4%, 64 ± 8%, and 65 ± 4%, respectively, compared with pre-ET values. These pain behaviors were maintained for 3 hours to 4 hours. Compared with the saline group, opioid analgesics significantly increased PWL for at least 80 minutes, with sufentanil exhibiting the highest analgesic effect. An increase in PWL was only observed at 10 minutes after ketamine. The PWP was transiently increased with opioid analgesics for 10 minutes to 40 minutes, but was not changed with ketamine. Weight bearing was improved with opioid analgesics for at least 2 hours, but only for up to 80 minutes with ketamine.

CONCLUSION

Our ET model includes long bone fracture and soft tissue injury, but no fixation surgery, mimicking prehospital ET. Our model produces acute, steady, and reproducible trauma-related pain behaviors, and is clinically relevant regarding the pain behaviors and established responses to common analgesics. This model of acute pain due to ET is ideal for prehospital pain management research.

Sphingosine-1-Phosphate Treatment Can Ameliorate Microvascular Leakage Caused by Combined Alcohol Intoxication and Hemorrhagic Shock

Fluid resuscitation following hemorrhagic shock is often problematic, with development of prolonged hypotension and edema. In addition, many trauma patients are also intoxicated, which generally worsens outcomes. We directly investigated how alcohol intoxication impacts hemorrhagic shock and resuscitation-induced microvascular leakage using a rat model with intravital microscopic imaging. We also tested the hypothesis that an endothelial barrier-protective bioactive lipid, sphingosine-1-phosphate (S1P), could ameliorate the microvascular leakage following alcohol intoxication plus hemorrhagic shock and resuscitation. Our results show that alcohol intoxication exacerbated hemorrhagic shock and resuscitation-induced hypotension and microvascular leakage. We next found that S1P effectively could reverse alcohol-induced endothelial barrier dysfunction using both cultured endothelial cell monolayer and in vivo models. Lastly, we observed that S1P administration ameliorated hypotension and microvascular leakage following combined alcohol intoxication and hemorrhagic shock, in a dose-related manner. These findings suggest the viability of using agonists that can improve microvascular barrier function to ameliorate trauma-induced hypotension, offering a novel therapeutic opportunity for potentially improving clinical outcomes in patients with multi-hit injuries.

Postoperative wound dehiscence: Predictors and associations

The Agency for Healthcare Research and Quality patient safety indicators (PSI) were developed as a metric of hospital complication rates. PSI-14 measures postoperative wound dehiscence and specifically how often a surgical wound in the abdominal or pelvic area fails to heal after abdominopelvic surgery. Wound dehiscence is estimated to occur in 0.5-3.4% of abdominopelvic surgeries, and carries a mortality of up to 40%. Postoperative wound dehiscence has been adopted as a surrogate safety outcome measure as it impacts morbidity, length of stay, healthcare costs and readmission rates. Postoperative wound dehiscence cases from the Nationwide Inpatient Sample demonstrate 9.6% excess mortality, 9.4 days of excess hospitalization and $40,323 in excess hospital charges relative to matched controls. The purpose of the current study was to investigate the associations between PSI-14 and measurable medical and surgical comorbidities using the Explorys technology platform to query electronic health record data from a large hospital system serving a diverse patient population in the Washington, DC and Baltimore, MD metropolitan areas. The study population included 25,636 eligible patients who had undergone abdominopelvic surgery between January 1, 2008 and December 31, 2012. Of these cases, 786 (2.97%) had postoperative wound dehiscence. Patient-associated comorbidities were strongly associated with PSI-14, suggesting that this indicator may not solely be an indicator of hospital safety. There was a strong association between PSI-14 and opioid use after surgery and this finding merits further investigation.

Haemodynamic changes in trauma

Trauma is the leading cause of death during the first four decades of life in the developed countries. Its haemodynamic response underpins the patient's initial ability to survive, and the response to treatment and subsequent morbidity and resolution. Trauma causes a number of insults including haemorrhage, tissue injury (nociception) and, predominantly, in military casualties, blast from explosions. This article discusses aspects of the haemodynamic responses to these insults and subsequent treatment. 'Simple' haemorrhage (blood loss without significant volume of tissue damage) causes a biphasic response: mean arterial blood pressure (MBP) is initially maintained by the baroreflex (tachycardia and increased vascular resistance, Phase 1), followed by a sudden decrease in MAP initiated by a second reflex (decrease in vascular resistance and bradycardia, Phase 2). Phase 2 may be protective. The response to tissue injury attenuates Phase 2 and may cause a deleterious haemodynamic redistribution that compromises blood flow to some vital organs. In contrast, thoracic blast exposure augments Phase 2 of the response to haemorrhage. However, hypoxaemia from lung injury limits the effectiveness of hypotensive resuscitation by augmenting the attendant shock state. An alternative strategy ('hybrid resuscitation') whereby tissue perfusion is increased after the first hour of hypotensive resuscitation by adopting a revised normotensive target may ameliorate these problems. Finally, morphine also attenuates Phase 2 of the response to haemorrhage in some, but not all, species and this is associated with poor outcome. The impact on human patients is currently unknown and is the subject of a current physiological investigation.

Combat Casualty Care research programme

The Combat Casualty Care research programme is an integrated suite of projects designed to address Defence Medical Services' research needs for casualty care. The programme covers a broad spectrum of topics ranging from the pathophysiological and immunological impact of military relevant injuries to the effects of these disturbances on the response to early treatment. Dstl Porton Down has a long history of studying military injuries and has developed models, both in vivo and physical, to address the research needs. The work is conducted in close collaboration with clinical colleagues at the Royal Centre for Defence Medicine who have direct experience of the clinical issues faced by combat casualties and insights into the potential clinical implications of emerging strategies. This article reviews progress in research areas spanning forward resuscitation, with a particular focus on blast-related injuries, trauma coagulopathy, effects of drugs on the response to haemorrhage and deployed research. A significant 'value added' component has been the underpinning of higher degrees for seconded military clinicians at Dstl Porton Down who have made a valuable contribution to the overall programme.

Ethanol consumption impairs the hemodynamic response to hemorrhagic shock in rats

Alcohol intoxication can exacerbate hemodynamic instability following hemorrhagic shock. Impairment of hormonal, neurohumoral, and immune responses can contribute to such instability; however, the relationship between blood alcohol levels and the progression of hemorrhagic shock accompanied with these responses has not been clearly demonstrated. Herein, we examined this relationship in rats treated with various dose of alcohol. After oral administration of alcohol and then hemorrhage, the recovery of mean blood pressure (MBP); increase in plasma level of norepinephrine, epinephrine, and vasopressin; and survival interval decreased in a dose-dependent manner as the blood alcohol level increased. There were no significant differences in the production of proinflammatory cytokines such as tumor necrosis factor (TNF)-α and interleukin (IL)-1β among the groups. The present results demonstrated alcohol aggravates hemorrhagic shock in a dose-dependent manner not by alerting the immune response, but by suppressing hormonal and neurohumoral responses, thereby inhibiting hemodynamic autoregulation and shortening the survival interval.

Lipoteichoic acid-induced TNF-α and IL-6 gene expressions and oxidative stress production in macrophages are suppressed by ketamine through downregulating Toll-like receptor 2-mediated activation oF ERK1/2 and NFκB

Lipoteichoic acid (LTA), a gram-positive bacterial outer membrane component, can cause septic shock. Our previous studies showed that ketamine has anti-inflammatory and antioxidant effects on gram-negative LPS-induced macrophage activation. In this study, we further evaluated the effects of ketamine on the regulation of LTA-induced TNF-alpha and IL-6 gene expressions and oxidative stress production in macrophages and its possible mechanisms. Exposure of macrophages to a therapeutic concentration of ketamine (100 microM) inhibited LTA-induced TNF-alpha and IL-6 expressions at protein or mRNA levels. In parallel, ketamine at 100 microM reduced LTA-stimulated phosphorylation of extracellular signal-regulated kinase 1/2 (ERK1/2). Sequentially, ketamine reduced the LTA-triggered translocation of nuclear factor-kappaB (NFkappaB) from the cytoplasm to nuclei and its transactivation activity. Pretreatment with PD98059, an inhibitor of ERK, decreased LTA-enhanced NFkappaB activation and TNF-alpha and IL-6 mRNA syntheses. Cotreatment with ketamine and PD98059 synergistically suppressed the LTA-induced translocation and transactivation of NFkappaB and biosyntheses of TNF-alpha and IL-6 mRNA. Application of Toll-like receptor 2 (TLR2) small interfering RNA (si)RNA into macrophages decreased the levels of this receptor, and simultaneously ameliorated LTA-augmented NFkappaB transactivation and consequent production of TNF-alpha and IL-6 mRNA. Cotreatment with ketamine and TLR2 siRNA synergistically lowered TNF-alpha and IL-6 mRNA syntheses in LTA-activated macrophages. Ketamine and TLR2 siRNA could reduce the LTA-induced increases in production of nitrite and intracellular reactive oxygen species in macrophages, and their combination had better effects than a single exposure. Thus, this study shows that one possible mechanism involved in ketamine-induced inhibition of LTA-induced TNF-alpha and IL-6 gene expressions and oxidative stress production is through downregulating TLR2-mediated phosphorylation of ERK1/2 and the subsequent translocation and transactivation of NFkappaB.

The impact of opioid administration on resuscitation volumes in thermally injured patients

Administration of resuscitation volumes far beyond the estimates established by burn-body weight resuscitation formulas has been well documented. The reasons behind this increase are not clear. We sought to determine if our resuscitation volumes had increased and, if so, what factors were related to their increase. A retrospective chart review identified 154 patients admitted with burns greater than 20% of their BSA during the years of 1975-1976 (period 1), 1990-1991 (period 2), and 2006-2007 (period 3). Charts were reviewed for total fluids (crystalloid, colloid, and blood products) and opioids given before admission, during the first 8 hours of treatment, the next 16 hours of treatment, and the following 24 hours of treatment. Opioids were converted to opioid equivalents (OE). Multiple regression analysis was performed to determine the effects of variables of interest and control for confounders. Significance was assumed at the P < .05 level. Resuscitation fluid volumes increased significantly among adults from 3.97 ml/kg/%BSA during the first period to 6.40 ml/kg/%BSA during the third period (P < .01). The same trend in children <30 kg was not seen (P = .72). Fluid administered during the first 24 hours was significantly associated with age, BSA, intubation, latter two study periods, and opioid administration. Fluid administration was consistently associated with opioid administration at all measured time points. At 24 hours postburn, patients who received 2 to 4 OE/kg required an average of additional 3,650 +/- 1,704 ml of fluid, those receiving 4 to 6 OE/kg had required an average of 25,154 +/- 4,386 ml, and those who received >6 OE kg had required an average of 32,969 +/- 3,982 ml. In this single center retrospective study, we have shown a statistically significant increase in resuscitation fluids (from 1975 to 2007) and an association of resuscitation volumes with opioids. Opioids have been shown to increase resuscitation volumes in critically ill patients through both central and peripheral effects on the cardiovascular system. Because increased fluid resuscitation has been associated with adverse consequences in other studies, further research on alternative pain control strategies in thermally injured patients is warranted.

Alcohol binge before trauma/hemorrhage impairs integrity of host defense mechanisms during recovery

BACKGROUND

Alcohol abuse, both chronic and acute, is a known modulator of immune function and is associated with increased incidence of traumatic injury. Previously, we demonstrated that acute alcohol intoxication before hemorrhagic shock impairs hemodynamic and neuroendocrine counterregulation, suppresses early lung proinflammatory cytokine expression, and increases mortality from infection during recovery. In the present study, we examined the impact of a 3-day alcohol binge on host responses during trauma/hemorrhage (T x Hem) and following overnight recovery.

METHODS

Chronically catheterized, adult male Sprague-Dawley rats were administered an intragastric bolus of alcohol (5 g/kg; 30% w/v) or isocaloric dextrose solution for 3 consecutive days, followed by a 2.5 g/kg dose on day 4 before undergoing full-thickness muscle-crush and fixed pressure (approximately 40 mmHg) hemorrhage and fluid resuscitation (2.4 x total blood volume removed).

RESULTS

Alcohol-binge produced a 16% decrease in basal mean arterial blood pressure (MABP), reduced the total blood loss required to reach and to sustain MABP of 40 mmHg, markedly blunted the increase in circulating epinephrine and norepinephrine (20-fold and 3-fold, respectively) levels, and increased immediate mortality from T x Hem. Consistent with our previous reports, significant up-regulation in lung and spleen tumor necrosis factor (TNF)-alpha and interleukin (IL)-1alpha expression was observed immediately following T x Hem and fluid resuscitation. Only the T x Hem-induced increase in lung TNF-alpha was prevented by binge alcohol administration. Following overnight recovery, significant lipopolysaccharide (LPS)-stimulated release of TNF-alpha, IL-1alpha, IL-6, and IL-10 was observed in cells isolated from blood and the alveolar and pleural compartments from all experimental groups. While T x Hem did not prevent LPS-induced release of TNF-alpha, IL-1alpha, IL-6, or IL-10 at 6 or 24 hours, alcohol binge suppressed TNF-alpha, IL-1 and IL-6 release, without altering IL-10 response in cells isolated from blood and pleural compartment. No significant modulation of alveolar macrophage response was observed following alcohol binge and T x Hem.

CONCLUSIONS

These results indicate that a 3-day alcohol binge results in hemodynamic instability associated with attenuated neuroendocrine activation and increased mortality during T x Hem as well as sustained suppression of the proinflammatory cytokine response of blood and pleural-derived cells to a "second-hit" inflammatory challenge. As a result, we speculate that the net shift toward an anti-inflammatory state may contribute to enhanced susceptibility to infection during the recovery period.

Hemodynamic responses and c-Fos changes associated with hypotensive hemorrhage: standardizing a protocol for severe hemorrhage in conscious rats

The central mechanisms underlying the transition from compensation to decompensation during severe hemorrhage (HEM) are poorly understood. Furthermore, a lack of consistency in HEM protocols exists in the current literature. This study assessed the cardiovascular response and Fos-like immunoreactivity (FLI) in specific brain regions following severe HEM at three rates (2, 1, or 0.5 ml.kg(-1).min(-1)) in conscious rats. Heart rate (HR) and arterial pressure were recorded during the withdrawal of 30% of total blood volume (TBV). Data from animals hemorrhaged at the fast (F-HEM, n = 6), intermediate (I-HEM, n = 7), or slow (S-HEM, n = 7) rates were compared with saline (SAL, n = 5) and hypotensive (hydrazaline-induced, HYDRAZ, n = 5) controls. All HEM rates produced similar degrees of hypotension at the time of 30% TBV withdrawal. All HEM rates also produced bradycardia, but the change in HR was only significant in the F-HEM and I-HEM groups. Associated with I-HEM and F-HEM, but not HYDRAZ treatment were significant increases in FLI in the caudal ventrolateral periaqueductal gray (PAG), the central lateral nucleus of the rostral parabrachial nucleus, and locus coeruleus compared with SAL treatment. I-HEM also induced significant increases in FLI in the dorsomedial PAG, A7 region, and the cuneiform nucleus compared with SAL. S-HEM did not induce any significant change in FLI. Our results suggest that HEM at a rate of 1 ml.kg(-1).min(-1) may be most useful for investigating the potential role of the rostral brainstem regions in mediating hemorrhagic decompensation in conscious rats.

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.

Pain management: is opioid immunosuppression a clinical problem?

For more than 100 years, the use of opioid analgesic agents has been linked with modulation of the immune system in man. More recently, it has become apparent that both exogenous and endogenous opioids exert some effect upon the immune system but that this can be beneficial or deleterious depending on numerous variables. Of the strong opioid analgesics in current use, the majority are seen to cause immunosuppression in man. However, it still remains unclear whether this is clinically important in man although it would appear to be good practice to avoid such agents in patients already immunosuppressed by disease or pharmacotherapy. Powerful opioid analgesics without immunosuppressive properties can be selected and should be used in such situations and as these agents can offer additional benefits in addition to their non-immunosuppresive analgesia, it should be considered whether to use them at all times in preference to immunosuppressive opioids.

Brisk production of nitric oxide and associated formation ofS-nitrosothiols in early hemorrhage

The results of previous inhibitor studies suggest that there is some increase in nitric oxide (NO) production from constitutive NO synthase in early hemorrhage (H), but the magnitude of NO production early after H has not been previously assessed. It is generally believed that only modest production rates are possible from the constitutively expressed NO synthases. To study this, anesthetized male Sprague-Dawley rats were subjected to 90 min of isobaric (40 mmHg) H. During this period of time, the dynamics of accumulation of NO intermediates in the arterial blood was assessed using electron paramagnetic resonance spectroscopy, chemiluminescence, fluorescence imaging, and mass spectrometry. Electron paramagnetic resonance-detectable NO adducts were also measured with spin traps in blood plasma and red blood cells. H led to an increase in the concentration of hemoglobin-NO from 0.9 ± 0.2 to 4.8 ± 0.7 μM. This accumulation was attenuated by a nonselective inhibitor of NO synthase, NG-nitro-l-argininemethyl ester (l-NAME), but not by NG-nitro-d-argininemethyl ester (d-NAME) or 1400W. Administration of l-NAME (but not 1400W or d-NAME) during H produced a short-term increase in mean arterial pressure (∼90%). In H, the level of N oxides in red blood cells increased sevenfold. S-nitrosylation of plasma proteins was revealed with “biotin switch” techniques. The results provide compelling evidence that there is brisk production of NO in early H. The results indicate that the initial compensatory response to H is more complicated than previously realized, and it involves an orchestrated balance between intense vasoconstrictor and vasodilatory components.

Opioids and opiates: analgesia with cardiovascular, haemodynamic and immune implications in critical illness

Traumatic injury, surgical interventions and sepsis are amongst some of the clinical conditions that result in marked activation of neuroendocrine and opiate responses aimed at restoring haemodynamic and metabolic homeostasis. The central activation of the neuroendocrine and opiate systems, known collectively as the stress response, is elicited by diverse physical stressor conditions, including ischaemia, glucopenia and inflammation. The role of the hypothalamic-pituitary-adrenal axis and sympathetic nervous system in counterregulation of haemodynamic and metabolic alterations has been studied extensively. However, that of the endogenous opiates/opioid system is still unclear. In addition to activation of the opiate receptor through the endogenous release of opioids, pharmacotherapy with opiate receptor agonists is frequently used for sedation and analgesia of injured, septic and critically ill patients. How this affects the haemodynamic, cardiovascular, metabolic and immune responses is poorly understood. The variety of opiate receptor types, their specificity and ubiquitous location both in the central nervous system and in the periphery adds additional complicating factors to the clear understanding of their contribution to the stress response to the various physical perturbations. This review aims at discussing scientific evidence gathered from preclinical studies on the role of endogenous opioids as well as those administered as pharmacological agents on the host cardiovascular, neuroendocrine, metabolic and immune response mechanisms critical for survival from injury in perspective with clinical observations that provide parallel assessment of relevant outcome measures. When possible, the clinical relevance and corresponding scenarios where this evidence can be integrated into our understanding of the clinical implications of opiate effects will be examined. Overall, the scientific basis to enhance clinical judgment and expectations when using opioid sedation and analgesia in the management of the injured, septic or postsurgical patient will be discussed.

Effect of increased cardiac output on hepatic and intestinal microcirculatory blood flow, oxygenation, and metabolism in hyperdynamic murine septic shock

OBJECTIVE

Septic shock-associated organ dysfunction is attributed to derangements of microcirculatory perfusion and/or impaired cellular oxygen utilization. The hepatosplanchnic organs are regarded to play a pivotal role in the pathophysiology of sepsis-related organ failure. In a murine model of septic shock, we tested the hypothesis whether achieving normotensive, hyperdynamic hemodynamics characterized by a sustained increase in cardiac output would allow maintenance of regional microvascular perfusion and oxygenation and, thus, hepatic metabolic capacity.

DESIGN

Prospective, controlled, randomized animal study.

SETTING

University animal research laboratory.

SUBJECTS

Male C57Bl/6 mice.

INTERVENTIONS

Fifteen hours after sham operation (n = 11) or cecal ligation and puncture (CLP) (n = 9), mice were anesthetized, mechanically ventilated, and instrumented (central venous and left ventricular pressure-conductance catheter, portal vein and superior mesenteric artery ultrasound flow probes). Animals received continuous intravenous hydroxyethylstarch and norepinephrine to achieve normotensive and hyperdynamic hemodynamics, and glucose was infused to maintain normoglycemia.

MEASUREMENTS AND MAIN RESULTS

Measurements were recorded 18, 21, and 24 hrs post-CLP. In CLP mice, titration of hemodynamic targets were affiliated superior mesenteric artery and portal vein flow. Using a combined laser-Doppler flowmetry and remission spectrophotometry probe, we found well-maintained gut and liver capillary perfusion as well as intestinal microcirculatory hemoglobin oxygen saturation, whereas hepatic microcirculatory hemoglobin oxygen saturation was even increased. At 24 hrs post-CLP, the rate of de novo gluconeogenesis as derived from hepatic C-glucose isotope enrichment after continuous intravenous 1,2,3,4,5,6-C6-glucose infusion (condensation biosynthesis modeling after gas chromatography-mass spectrometry isotope measurements) was similar in the two experimental groups.

CONCLUSIONS

During murine septic shock achieving normotensive hyperdynamic hemodynamics with fluid resuscitation and norepinephrine, exogenous glucose requirements together with the lack of norepinephrine-induced increase in the rate of gluconeogenesis mirror impaired metabolic capacity of the liver despite well-maintained hepatosplanchnic microvascular perfusion and oxygenation.

Endogenous opiates and behavior: 2004

This paper is the 27th consecutive installment of the annual review of research concerning the endogenous opioid system, now spanning over 30 years of research. It summarizes papers published during 2004 that studied the behavioral effects of molecular, pharmacological and genetic manipulation of opioid peptides, opioid receptors, opioid agonists and opioid antagonists. The particular topics that continue to be covered include the molecular-biochemical effects and neurochemical localization studies of endogenous opioids and their receptors related to behavior, and the roles of these opioid peptides and receptors in pain and analgesia; stress and social status; tolerance and dependence; learning and memory; eating and drinking; alcohol and drugs of abuse; sexual activity and hormones, pregnancy, development and endocrinology; mental illness and mood; seizures and neurologic disorders; electrical-related activity and neurophysiology; general activity and locomotion; gastrointestinal, renal and hepatic functions; cardiovascular responses; respiration and thermoregulation; and immunological responses.

Pain management and regional anaesthesia in the trauma patient

PURPOSE OF THE REVIEW

Treatment of the trauma patient has evolved rapidly in the past decade. Nevertheless, the treatment of pain as part of overall trauma management has been relatively neglected. This update reviews recent publications related to pain relief in the trauma patient.

RECENT FINDINGS

Although recent publications suggest that the assessment and treatment of pain in trauma have improved, most studies still document inadequate analgesia. We discuss the use of different analgesia strategies in the prehospital and emergency room settings.

SUMMARY

Educating the emergency room staff to perform early routine assessment of pain and to be familiar with the administration of analgesia are key elements to improved pain management in trauma. Peripheral nerve block techniques should be practised by emergency room staff. If simple techniques are chosen, competence can be achieved with short, focused training sessions. Further developments are needed in order to provide safer and more effective analgesia to the trauma patient.