Sublingual capnometry: a new noninvasive measurement for diagnosis and quantitation of severity of circulatory shock

OBJECTIVE

To investigate the feasibility and predictive value of sublingual Pco2 (P(SL)CO2) measurements as a noninvasive and early indicator of systemic perfusion failure.

DESIGN

A prospective, criterion study.

SETTING

Emergency department and medical and surgical intensive care units of an urban community medical center.

PARTICIPANTS AND PATIENTS

Five normal human volunteers and 46 patients with acutely life-threatening illness or injuries.

INTERVENTIONS

Intra-arterial or automated cuff blood pressure and arterial blood lactate (LAC) were measured concurrently with P(SL)CO2.

RESULTS

P(SL)CO2 in five healthy volunteers was 45.2 +/- 0.7 mm Hg (mean +/- sD). Twenty-six patients with physical signs of circulatory shock and LAC >2.5 mmol/L had a P(SL)CO2 of 81 +/- 24 mm Hg. This contrasted with patients admitted without clinical signs of shock and LAC of <2.5 mmol/L who had a P(SL)CO2 of 53 +/- 8 mm Hg (p < .001). The initial P(SL)CO2 of 12 patients who died before recovery from shock was 93 +/- 27 mm Hg, and this contrasted with 58 +/- 11 mm Hg (p < .001) in hospital survivors. Increases in P(SL)CO2 were correlated with increases in LAC (r2 = .84; p < .001). When P(SL)CO2 exceeded a threshold of 70 mm Hg, its positive predictive value for the presence of physical signs of circulatory shock was 1.00. When it was <70 mm Hg, it predicted survival with a predictive value of 0.93.

CONCLUSION

P(SL)CO2 may serve as a technically simple and noninvasive clinical measurement for the diagnosis and estimation of the severity of circulatory shock states.

Detection of histamine-induced capillary protein leakage and hypovolaemia by determination of indocyanine green and glucose dilution method in dogs

OBJECTIVE

The plasma volume of histamine-induced protein capillary leakage may be overestimated when this is determined using the indocyanine green (ICG) dilution method (Vd-ICG), since this dye binds to plasma proteins. The initial distribution volume of glucose (IDVG) has been shown to indicate the central extracellular fluid volume including plasma. Accordingly, the overestimation would be detected by a higher Vd-ICG/IDVG ratio. Our study was intended to examine whether the simultaneous measurement of these two variables can evaluate histamine-induced protein leakage and associated hypovolaemia.

DESIGN

Prospective animal study.

SETTING

Institutional animal research laboratory.

SUBJECTS

Twenty-four anaesthetized and ventilated mongrel dogs.

INTERVENTIONS

Anaesthetized animals were mechanically ventilated and received infusions of normal saline (n = 8), histamine 50 microg/kg per h (n = 8), or histamine 100 microg/kg per h. The Vd-ICG and IDVG were calculated using a one-compartment model by simultaneous administration of ICG 0.5 mg/kg, and glucose 100 mg/kg followed by serial arterial blood sampling.

MEASUREMENTS AND RESULTS

In both histamine groups, a significant elevation of haematocrit and a decrease of plasma albumin concentration were found (p<0.05). Although the IDVG decreased following histamine administration (p<0.05), the Vd-ICG remained unchanged. The Vd-ICG/IDVG ratio increased in a dose-dependent manner after histamine administration (p<0.05), but remained unchanged following normal saline administration.

CONCLUSION

The results suggest that the Vd-ICG/IDVG ratio and the IDVG are useful in evaluating the magnitude of the leakage and hypovolaemia.

Management of vasodilatory shock after cardiac surgery: identification of predisposing factors and use of a novel pressor agent

BACKGROUND

Cardiopulmonary bypass can be associated with vasodilatory hypotension requiring pressor support. We have previously found arginine vasopressin to be a remarkably effective pressor in a variety of vasodilatory shock states. We investigated the incidence and clinical predictors of vasodilatory shock in a general population of cardiac surgical patients and the effects of low-dose arginine vasopressin as treatment of this syndrome in patients with heart failure.

METHODS

Patients undergoing cardiopulmonary bypass (n = 145) were studied prospectively. Preoperative ejection fraction, medications, and perioperative hemodynamics were recorded, and postbypass serum arginine vasopressin levels were measured. Vasodilatory shock was defined as a mean arterial pressure lower than 70 mm Hg, a cardiac index greater than 2.5 L/min/m2, and norepinephrine dependence. Predictors of vasodilatory shock were investigated by logistic regression analysis. The hemodynamic responses of patients who received arginine vasopressin infusions for vasodilatory shock after cardiopulmonary bypass for left ventricular assist device placement or heart transplantation were analyzed retrospectively.

RESULTS

Eleven of 145 general cardiac surgery patients (8%) met criteria for postbypass vasodilatory shock. By multivariate analysis, an ejection fraction lower than 0.35 and angiotensin-converting enzyme inhibitor use were independent predictors of postbypass vasodilatory shock (relative risks of 9.1 and 11.9, respectively). Vasodilatory shock was associated with inappropriately low serum arginine vasopressin concentrations (12.0 +/- 6.6 pg/mL). Retrospective analysis found 40 patients with postbypass vasodilatory shock who received low-dose arginine vasopressin infusions, resulting in increased mean arterial pressure and decreased norepinephrine requirements.

CONCLUSIONS

Low ejection fraction and angiotensin-converting enzyme inhibitor use are risk factors for postbypass vasodilatory shock, and this syndrome is associated with vasopressin deficiency. In patients exhibiting this syndrome after high-risk cardiac operations, replacement of arginine vasopressin increases blood pressure and reduces catecholamine pressor requirements.

Neutrophil signaling alteration: an adverse inflammatory response after burn shock

The inflammatory response syndrome in shock-like states might frequently be accompanied by an oxidative cell/tissue damage in one or more organ-systems in the body. The inflammatory response related hyperactivation of neutrophils can contribute to oxidative cell/tissue damage. Studies discussed in this review examined the role of cell signaling pathways in the hyperactivation of neutrophils in an early stage of burn injury shock. The studies were carried out in peripheral blood neutrophils isolated from rats with a 25% body surface area scald burn. Neutrophil cell signaling responses were evaluated by measuring cytosolic [Ca2+] and protein kinase C activity, and were correlated with neutrophil superoxide production. The cytosolic [Ca2+] and protein kinase C responses were highly upregulated along with enhanced superoxide production in the early phase of burn injury. The treatment of burn-injured rats with the calcium antagonist diltiazem abrogated enhanced Ca2+ and protein kinase C signaling and superoxide generation. The signaling upregulation in neutrophils could result from potentiation of actions of burn-injury induced chemotactic mediators on the leukocytes. The neutrophil signaling upregulation leading to increased superoxide generation could thus be responsible for the oxidative cell/tissue damage. The organ-system dysfunction/failure accompanying burn shock may be initiated with the oxidative cell/tissue damage.

Detection of ferritin in the plasma of guinea pigs in experimental shock

Guinea pigs were subjected to shock by hemorrhage or by infusion of either E. coil or S. enteritidis endotoxin, and changes in levels of plasma-bound iron and ferritin were assayed. Of 12 bled animals, all showed increases in plasma-bound iron and half gave a positive test for ferritin. Of 12 guinea pigs treated with LD 80 doses of E. coli endotoxin, only 4 showed an elevation in plasma-bound iron. Of these only one was positive for ferritin. Of 10 guinea pigs treated with LD 80 doses of S. enteritdis endotoxin, only five showed elevations in plasma-bound iron, and three of these also showed detectable increases in plasma ferritin. Immunologically detect able increases in plasma ferritin were not found in any of the endotoxin-infused animals showing decreases in plasma-bound iron.

It was concluded: (a) that, in the guinea pig (as in the rabbit), hyperferremia is more frequent after hemorrhage than after the in fusion of Gram-negative bacterial endotoxin (b) that significant increases in ferritin do not appear simultaneously with decreases in total plasma-hound iron in endotoxic guinea pigs; and (c) that hyperferremia and hyperferritinemia do not play a direct role in the lethal progression of endotoxic shock in the guinea pig.

Human cardiovascular variability, baroreflex and hormonal adaptations to a blood donation

1. We studied cardiovascular variability, baroreflex and blood volume regulating hormones to determine the relative roles of autonomic regulation and hormones during blood donation.2. The sympathetic response was studied by measuring the R-R interval and systolic blood pressure variability using coarse graining spectral analysis in eight blood donors. Beat-by-beat R-R intervals and blood pressure were recorded for 20 min before and 5 min after a whole-blood donation of 480+/-10 ml (about 7 ml/kg of blood volume, over 4 min). Plasma catecholamines, vasopressin, atrial natriuretic peptide, endothelin, active renin, osmolality, Na+, K+, haemoglobin and haematocrit were measured just before and after blood withdrawal.3. Blood donation led to increases in the plasma catecholamines (adrenaline, 21+/-2 versus 35+/-3 pg/ml; noradrenaline, 229+/-26 versus 323+/-37 pg/ml; dopamine, 34+/-3 versus 66+/-9 pg/ml) and in systolic blood pressure (130+/-6 versus 140+/-5 mmHg). These changes were independent of ionic or slow endocrine mechanisms. Heart rate, cardiovascular variability and the spontaneous baroreflex sensitivity did not change despite the increase in blood pressure and catecholamines. Thus the peripheral vascular control was probably involved.4. We conclude that the absence of any change in heart rate usually observed during non-hypotensive hypovolaemic stress is probably due to the sympathetic activation being counterbalanced by the high supine vagal tone at the heart and not to the heterogeneous nature of the sympathetic neural response or to changes in sympathetic and parasympathetic activity without any change in autonomic balance.

Importance of the sampling site for measurement of mixed venous oxygen saturation in shock

OBJECTIVES

To determine if oxyhemoglobin saturation in blood samples taken from the superior vena cava or right atrium can be substituted for oxyhemoglobin saturation in blood taken from the proximal pulmonary artery (SVO2) in patients in shock.

DESIGN

Prospective clinical investigation.

SETTING

Mixed surgical/medical intensive care unit in a university hospital.

PATIENTS

Thirty consecutive patients in severe circulatory shock who required insertion of a pulmonary artery flotation catheter (PAFC) immediately on intensive care unit admission. All patients fulfilled the criteria described below which were established in advance.

MEASUREMENTS AND MAIN RESULTS

Oxyhemoglobin saturation in the superior vena cava, right atrium, and pulmonary artery (SVO2) was measured by cooximetry in consecutive blood samples from each site during initial insertion of the PAFC. The mean standard deviation of values from these sites was similar: 74 +/- 12.5%, 70.+/- 13%, and 71.3 +/- 12.7%, respectively. However, when superior vena cava and right atrial oxyhemoglobin saturations and SvO2 were compared, the ranges and 95% confidence limits were found to be clinically unacceptable. The ranges were -19.3 to 23.1% and -19.7 to 16.7%, respectively, and the 95% confidence limits were -18.4 to 24.2% and -18.6 to +17.3%, respectively.

CONCLUSIONS

These wide range differences and confidence limits would lead to large errors if superior vena cava or right atrial oxyhemoglobin saturations were substituted for true mixed venous blood in oxygen transport or pulmonary venous admixture calculations, or if clinical decision making was based on individual results. In patients in shock in whom clinical decisions may be based on the value of mixed venous oxyhemoglobin, oxyhemoglobin saturation is only reliably measured in samples taken from the pulmonary artery.

Base deficit as an indicator or resuscitation needs in patients with burn injuries

The utility of base deficit (BD) as a marker of shock and as an indicator of resuscitation requirements has been recognized in the trauma population. Base deficit in thermally injured patients has not been closely examined. The purpose of this study was to evaluate the usefulness of initial BD related to other resuscitation parameters in thermally injured patients. Burn center records over a 2-year period were reviewed; patients who survived at least 24 hours and had initial arterial blood gases were included. Parkland estimated fluid requirements underestimated actual volume requirements, but Parkland-calculated fluid requirements were related (p < 0.01) to actual volume requirements. BD had a better correlation to actual volume requirements, and a BD of -6 or less correlated with larger burn size (23% +/- 2% vs 47% +/- 9% total body surface area), and markedly increased mortality rate (9% vs 72%, p < 0.001).

Oxygen-carrying macromolecules: therapeutic agents for the treatment of hypoxia

A stabilized form of hemoglobin as oxygen-carrying macromolecules was developed. It had an approximately 90,000 dalton molecular weight, and its intravascular half-life was 36 h. Its molecular size was less than 0.1 microm. Its hemoglobin concentration was 6% and its P50 value was 24 mm Hg. Oxygen carried inside plasma performs differently than oxygen carried inside red cells. Less than 0.3 cc of oxygen in 100 ml of blood is available in the plasma while 14-19 ml of oxygen is carried inside the red cells. Thus, less than 5 cc of oxygen is available inside the plasma of the entire body. When a patient develops hypovolemic shock, the red cells are bypassed and are not perfused directly inside the tissues. However, the plasma should reach hypoxic tissues. Thus, infusion of oxygen-carrying macromolecules into the plasma should be therapeutically effective even when infusing less than 100 ml of stabilized hemoglobin solution under shock conditions. The basic physiology of oxygen-carrying macromolecules is described in detail, which is different from the physiology of oxygen-carrying red cells.

[Origin of microcirculation disorders in tissue hypoxia, shock and disseminated intravascular blood coagulation]

The origin of microcirculation disorders in tissue hypoxia, shock, and disseminated intravascular coagulation is discussed with consideration for the heretofore unknown capacity of free hemoglobin and free myoglobin to cause smooth muscle convulsions and accelerate platelet destruction.

Central-peripheral temperature difference, blood pressure, and arginine vasopressin in preterm neonates undergoing volume expansion

AIM

To examine the effect of intravascular volume expansion for the treatment of hypovolaemia in sick preterm neonates.

METHODS

An intravenous infusion of 20 ml per kg of 4.5% albumin was given to 14 preterm neonates. The effects on systolic blood pressure, central peripheral temperature difference (c-pT), and plasma arginine vasopressin concentration (pAVP) were measured.

RESULTS

Thirteen babies showed a rise in systolic blood pressure. The six babies with the highest initial values of pAVP and c-pT showed a fall in both of these after infusion. The babies with lower initial pAVP (below 4 pmol/l) showed either a rise (two) or no change (six) after albumin infusion. There was a significant correlation between c-pT and log pAVP before (r2 = 0.61; p < 0.05) and after infusion (r2 = 0.45; p < 0.05).

CONCLUSIONS

Plasma AVP concentration is related to c-pT in unwell preterm newborns. This study suggests that clinical assessment of hypovolaemia in preterm newborns is poor and could be improved by using c-pT.

Hepatic ischemia/reperfusion affects leukocyte rolling and velocity

Mechanisms of injury in hepatic ischemia/reperfusion injury are poorly defined. Leukocytes are thought to be important in the final mechanism of hepatic damage. We intend to show the time course of abnormal leukocyte activity in the liver after ischemia/reperfusion (I/R) injury. Left lobar hepatic ischemia was induced for 20 min in anesthetized C57B1-6 mice. Measurements were taken at control, reperfusion, and matching sham times (no ischemia) of 2, 5, 12, and 24 h. Measurements were taken using rhodamine and fluorescein enhanced intravital microscopy. Post sinusoidal venules were evaluated for numbers of rolling leukocytes, leukocyte saltation, and leukocyte velocity. Data are expressed as number of rolling leukocytes per 100 microns venule length (2 min). Statistical analysis was by ANOVA. The number of rolling leukocytes at 5, 12, and 24 h of reperfusion (p < 0.001) was significantly higher than control and sham-operated animals. Leukocyte velocities were significantly slower in the 12 h I/R group when compared to sham animals (p < 0.001). These data show that there are definable and quantifiable changes in leukocyte kinetics in the liver after ischemia/reperfusion. These changes, which lasted for 24 h, are likely due to upregulation of various endothelial cell adhesion molecules. Delineation of these mechanisms may be important in disease states such as shock, sepsis, and hepatic transplantation.

Effect of alcohol on the utility of base deficit in trauma

OBJECTIVE

Base deficit (BD) is an indicator of metabolic acidosis and is used as an index of shock and resuscitation for trauma patients. Ethanol causes an increase in lactate production and may cause metabolic acidosis in otherwise normal patients. The effects of alcohol on BD have not been investigated. This study was performed to determine the effects of ethanol on the utility of BD for assessing shock and resuscitation among trauma patients.

DESIGN

Retrospective review of trauma registry, blood bank, and medical records data.

METHODS

Data were collected for trauma patients admitted to the University Medical Center Level I trauma service from July 1990 through August 1995 with an arterial blood gas and blood alcohol level obtained within 1 hour of admission.

MEASUREMENTS AND MAIN RESULTS

The Trauma Score and the Revised Trauma Score were slightly higher (p < 0.001), and the Injury Severity Score was significantly lower (p < 0.001) in the presence of alcohol. These changes were present until patients reached the severe BD category (< or = -10), at which point there were no significant differences across all blood alcohol levels. In spite of these changes, there was no difference in intensive care unit or hospital length of stay in any BD or blood alcohol group. In patients with a BD < or = -6, there was a decreased requirement for transfusion in the presence of alcohol (57 vs. 78%; p < 0.001, chi2), but the majority of patients in both groups required blood transfusion.

CONCLUSION

Ethanol can contribute significantly to metabolic acidosis among trauma patients and may confound the utility of BD to some degree. There was no difference in intensive care unit or overall length of stay, however, regardless of ethanol level, and the majority of patients with a BD < or = -6 still required transfusion. Even in the presence of ethanol, a BD < or = -6 remains a powerful indicator of major injury, increased length of stay, and transfusion requirement.

Circulatory resuscitation with left ventricular assist device support reduces interleukins 6 and 8 levels

BACKGROUND

Elevated tumor necrosis factor serum levels have been reported in patients with severe congestive heart failure. This study was designed to characterize the cytokine profile in patients with acute circulatory collapse.

METHODS

Blood drawn from 14 consecutive patients within 24 hours before undergoing left ventricular assist device placement and after at least 30 days of mechanical assistance or before transplantation was assayed for levels of interleukin 6, interleukin 8, and tumor necrosis factor-alpha.

RESULTS

Interleukin 6 level was elevated in 11 (79%), interleukin 8 in 10 (71%), and tumor necrosis factor in 2 (14%) of the 14 patients. After hemodynamic recovery, interleukin 6 levels decreased from 33.6 +/- 9 pg/mL to 11.3 +/- 4 pg/mL (p = 0.05) and interleukin 8 levels decreased from 122 +/- 34 pg/mL to 19.7 +/- 8 pg/mL (p = 0.005). Tumor necrosis factor-alpha levels did not vary significantly; they were associated with infection in 2 left ventricular assist device recipients and normalized after left ventricular assist device support. All patients had resolution of circulatory shock after mechanical support and had improvement in parameters of end-organ function.

CONCLUSIONS

Circulatory shock treated with left ventricular assist device placement is associated with a proinflammatory response similar to that seen in septic shock. The decrease in cytokine serum levels that follows hemodynamic recovery suggests that these cytokines may be markers of tissue damage and may modulate cardiac dysfunction.

Hypovolaemic shock after anthelmintic treatment of canine angiostrongylosis

Canine angiostrongylosis was diagnosed in a whippet with typical signs of respiratory and circulatory distress. Subclinical Angiostrongylus vasorum infections were also demonstrated in two other whippets belonging to the same owner. All three dogs were given standard anthelmintic levamisole treatment combined with corticosteroids. Two days after initiation of treatment, one of the subclinically infected dogs developed severe hypovolaemic shock that required intravenous fluid therapy and corticosteroids to save its life. The shock is believed to have been caused by an anaphylactic reaction triggered by the rapid release of a large amount of worm antigen in the blood due to the rapid death of adult worms by levamisole. Thus, dog owners should be instructed to monitor dogs undergoing levamisole treatment against A vasorum. Alternatives to levamisole treatment of canine angiostrongylosis should be considered.

Interleukin-6 and its soluble receptor during acute meningococcal infections: effect of plasma or whole blood exchange

OBJECTIVES

To determine the pattern of the soluble interleukin (IL)-6 receptor during acute meningococcal infections and recovery phase, and to measure the effect of plasma or whole blood exchange on the plasma concentrations of these mediators.

DESIGN

Prospective, descriptive patient study.

SETTING

University hospital intensive care unit.

PATIENTS

Patients with bacteriologically proven meningococcal infections were entered in the study. Three group were formed: a) patients with meningitis without shock (group A); b) patients with meningitis and shock (group B); and c) patients with shock only (group C).

INTERVENTIONS

Part (n = 9) of the patients with shock underwent plasma or whole blood exchange.

MEASUREMENTS AND MAIN RESULTS

Serum concentrations of interleukin-6 and soluble IL-6 receptors were determined sequentially during the acute and recovery phases. Peak concentrations of IL-6 were highest in group C, followed by group B and group A. Soluble IL-6 receptor concentrations showed an opposite pattern and were all below normal. Soluble IL-6 receptor concentrations were negatively correlated with the IL-6 concentrations. During recovery, IL-6 rapidly decreased and soluble IL-6 receptors increased to supranormal concentrations, after which concentrations returned to normal. Plasma or whole blood exchange did not significantly influence IL-6 concentrations but did increase the soluble IL-6 receptor concentration directly after an exchange session followed by a rapid decrease.

CONCLUSIONS

Soluble IL-6 receptor concentrations are low in acute meningococcal infections. Plasma or whole blood exchange temporarily increases these concentrations. It needs to be determined whether the effect of this therapy is beneficial to the patient.

Release of vasopressin in response to altered plasma volume and sodium concentrations following pinealectomy in the rat

Pinealectomy has been shown to alter daily rhythms of neurohypophysial hormone release, with plasma hormone concentrations being elevated in the morning, as compared to intact rats. To determine whether pineal removal also altered the response to known stimuli of hormone release, vasopressin concentrations were measured in control, sham-operated, and pinealectomized animals during extracellular fluid hypertonicity produced by an intraperitoneal (i.p.) injection of hypertonic saline or hypovolaemia produced by an i.p. injections of polyethylene glycol. In the combined sham-operated and unoperated groups, injection of hypertonic saline produced a marked increase in plasma vasopressin concentrations from 2.18 +/- 0.28 to 7.2 +/- 1.24 pmol/liter, but the response was attenuated in pinealectomized animals, concentrations increasing to only 3.4 +/- 1.2 pmol/liter. Similarly, following infusion of hypertonic saline, the increase in plasma vasopressin per unit increase in plasma sodium was lower in pinealectomized animals than the pineal intact controls. The response to hypovolaemia was also attenuated, plasma hormone concentrations following reduction in blood volume of approximately 10% increasing to only 3.6 +/- 0.6 pmol/liter as compared to 7.3 +/- 2.2 pmol/liter in the control groups. There were no significant differences in pituitary vasopressin content in any of the groups studied. Thus, the pineal may influence the vasopressin response to physiological stimuli.

Subcutaneous tissue oxygen pressure: a reliable index of peripheral perfusion in humans after injury

The usual initial life-threatening effect of injury is hypovolemic shock. In the hierarchical physiologic response to hypovolemia, perfusion of peripheral tissues is sacrificed early and restored late. But the usual hemodynamic and metabolic measurements of blood pressure, urine output, and base deficit are not reliable indices of peripheral perfusion. Although the Clark electrode can quantitate tissue oxygen pressure and thereby serve as an index of perfusion, its use is compromised by several technical deficiencies. Recently, an optical method (optode) using fluorescent technology has been developed for measurement of oxygen tension in subcutaneous tissue (P sgO2). Our studies compared this device with the Clark electrode in the laboratory and tested its value in both animal and clinical studies of hypovolemic shock. The results of these several studies demonstrated that: (1) the new oximeter tracked a rapid fall or rapid rise of oxygen tension between room air (150 mm Hg) and 0 mm Hg ( a glucose oxidase/catalase solution) as well as the Clark electrode without encountering its technical problems; (2) with an acute hemorrhage to 20% of base line, the PsgO2 was found to decline rapidly in parallel with the decline of mean arterial pressure (MAP). Although the MAP rapidly returned to normal after immediate complete return of all shed blood, the PsgO2 did not reach normal levels for at least 2 hours, suggesting persistent peripheral vasoconstriction. (3) Studies in progress suggest that between 35 and 78% of trauma patients (n = 18) adequately resuscitated for hypovolemia b customary criteria have a decreased level of PsgO2 for as long as 60 hours after resuscitation for injury. If care is taken to prevent other causes of catecholamine induced vasoconstriction such as pain, fear, cold, and arterial hypoxia, these several results suggest that a certain number of injured patients are inadequately resuscitated despite the return to normal of conventional hemodynamic measurements. The serial analysis of PsgO2 may assist in managing patients and promote better understanding of the responses to injury.

The fall of cardiac output in endotoxemic rats cannot explain all changes in organ blood flow: a comparison between endotoxin and low venous return shock

During endotoxin shock mean arterial pressure (MAP) and cardiac output (CO) fall, and the latter is redistributed. To evaluate whether these changes are solely caused by the low output, or are also based on endotoxin itself, we compared regional hemodynamic changes during endotoxemia with those in a nonendotoxemic state of decreased CO in anesthetized rats. In group E (n = 10) endotoxin Escherichia coli O127:B8 (8 mg.kg-1) was infused from t = 0 till t = 60 min. In group B (n = 10) the same decrease of CO and MAP was obtained as in group E by inflating a balloon in the inferior caval vein, distal to the renal veins, from t = 0 till t = 60 min. We measured MAP, CO (thermodilution), central venous pressure, heart rate, organ blood flow, and redistribution of CO (microspheres), arterial lactate and glucose, and hematocrit. MAP and CO decreased (p < .05) in both groups (by 30 and 50%, respectively at t = 60). Heart rate, hematocrit, arterial lactate, and arterial glucose were significantly higher (p < .05) in group E (by 17, 12, 180, and 55%, respectively). Blood flow to most organs had similarly decreased in both groups. The decreased intestinal blood flow lead to macroscopic damage only in group E. Blood flows (absolute or as percentage of CO) to heart, hepatic artery, and diaphragm, however, had significantly increased in group E while blood flows to skin, skeletal muscle, and stomach had decreased more in group E. Except for the heart these differences could be explained by increased work load (detoxification: liver; hyperventilation: diaphragm, muscle) and thus to a more pronounced redistribution at the expense of skin and muscle blood flow. Regional hemodynamic changes during endotoxemia thus could largely be attributed to decrease of CO and redistribution of the circulating blood volume. In the heart, endotoxin seemed to exert effects independent of the hypodynamic state. This was also true for the intestinal damage and the rise in hematocrit and arterial lactate.

[Behavior of the lactate level in occlusion and reperfusion of the right superior mesenteric artery. An animal experiment study]

The value of lactate in the early clinical diagnosis of acute mesenteric arterial occlusion was evaluated in an animal model. The superior mesenteric artery of pigs (8-9 weeks old, 20-23 kg) was clamped for 1 h (group 2, n = 9) and 3 h (group 3, n = 6). Reperfusion was recorded for 2 h. Follow-up measurements were done in six animals (group 1). The systolic blood pressure was elevated significantly to about 18-40 mmHg in the initial phase of ischemia (P = 0.02). The intramucosal pHi measured tonometrically was decreased to below a value of 7.08 (P = 0.03), and the flow of superior mesenteric vein was reduced by about 90% ( P = 0.03) in groups 2 and 3. Within 30 min the lactate increased to about 2.05-3.8 mmol/l in the central venous blood sample and 2.8-4.8 mmol/l in the portal vein blood sample in 30 min. After 3 h of ischemia (group 3) the elevated lactate level returned to normal without any significant difference. In the reperfusion period (group 2) the systolic blood pressure stabilized at a depressed level (63-73 mmHg, P = 0.0054), and the flow of the superior mesenteric vein showed a reduction of 41% (P = 0.03). Intramucosal pHi and lactate values returned nearly completely to normal within 2 h. Reperfusion after 3 h of ischemia (group 3) caused marked shock without any sign of recovery at intramucosal pH or mesenteric vein flow. The lactate values increased for above the ischemic level. In conclusion, an elevated lactate level only correlates with the initial phase of acute mesenteric arterial occlusion. A normal lactate concentration cannot exclude the diagnosis of mesenteric ischemia. Reperfusion of the ischemic intestine is characterized by circulatory shock with secondary increased lactate concentration without predictive value for adequate intestinal perfusion.

Capillary zone electrophoresis of organic acids in serum of critically ill children

Capillary zone electrophoresis with indirect UV detection was found to be suitable for the determination of organic acids in serum. Serum can be analysed directly without any deproteination in a capillary coated with linear polyacrylamide. With 10 mM epsilon-aminocaproic acid-10 mM mandelic acid (pH 3.8) as the operational electrolyte, anions such as pyruvate, phosphate, citrate, malate, acetoacetate and lactate can be determined in 12 min. In quantitative analysis, the calibration line for lactate is linear over the range 0-10 mM. The detection limit for citrate was 8 microM. The effect of the chloride concentration on the migration times of minor peaks is discussed. The potential of the method was demonstrated by analysing sera from several critically ill children.

Serum cortisol levels in children with dengue haemorrhagic fever

Dengue Haemorrhagic Fever (DHF) is a serious and often fatal paediatric problem in Myanmar. Acute and convalescent serum cortisol levels were measured in 62 children with dengue infection to study cortisol sufficiency in this disease. Twenty-six children with non-dengue acute viral infection were also included as controls. In acute stage, highest mean serum cortisol level (655.4 +/- 72.18 nmol/l) was observed in DHF cases presenting with shock, followed by DHF non-shock cases (640.56 +/- 74.58 nmol/l) and dengue fever cases (617.2 +/- 75.38 nmol/l). Cases with DHF had significantly higher serum cortisol level (P < 0.05) than in controls (444.41 +/- 59.71 nmol/l). In cases of DHF, mean serum cortisol level during the acute stage was found to be significantly two-fold higher than the convalescent stage. We found no cortisol insufficiency in cases of dengue haemorrhagic fever during acute and convalescent stages of illness.

Clinical and biological significance of interleukin-10 plasma levels in patients with septic shock

Interleukin-10 is a potent macrophage-deactivating cytokine that inhibits lipopolysaccharide-induced tumor necrosis factor production. We determined the plasma levels of immunoreactive interleukin-10 in 16 patients with septic shock and in 11 patients with circulatory shock of nonseptic origin. In septic shock, interleukin-10 levels peaked during the first 24 h (median: 48 pg/ml) and decreased progressively till Day 5. In nonseptic shock, interleukin-10 plasma levels also increased during the first 24 h but to a lesser extent (median: 17 pg/ml). In septic shock patients, interleukin-10 plasma levels were positively correlated with tumor necrosis factor (r = 0.8, p = 0.01) and with parameters of shock severity including lactate levels (r = 0.56, p < 0.05) and correlated negatively with blood platelet counts (r = -0.65, p < 0.05). The decreased production of tumor necrosis factor-alpha and interleukin-6 after in vitro incubation of whole blood from septic shock patients with lipopolysaccharide was not influenced by in vitro neutralization of interleukin-10. We conclude that interleukin-10 is produced in patients with circulatory shock of septic and nonseptic origin and that the production of this anti-inflammatory cytokine during septic shock correlates positively with the intensity of the inflammatory response.

Simultaneous in vivo comparison of two-versus three-wavelength mixed venous (Svo2) oximetry catheters

OBJECTIVE

Venous oximetry catheters provide useful realtime information about mixed venous hemoglobin saturation (Svo2). Currently available systems utilize either two or three wavelengths of light to obtain these measurements. Previous animal and clinical studies have attempted to compare the accuracy of these two devices under similar circumstances. However, the relative accuracy of the two-wavelength versus three-wavelength systems has never been assessed under identical conditions. For this purpose, we designed an animal model for simultaneous measurement of Svo2, over a wide range of physiologic and pathologic states.

METHODS

Seven anesthetized swine underwent simultaneous placement of two- and three-wavelength catheters. Paired data points consisted of values obtained from a reference oximeter and from each of the catheters. Observations were obtained every 15 min during the following manipulations: (1) eucarbic hypoxia induced by reducing FiO2 to 0.18, 0.15, and 0.12 for 15 min each; (2) stimulated surgical manipulation; and (3) hypovolemic shock produced by hemorrhage to a mean arterial pressure of 50 torr for 1 hr. Data were analyzed by calculation of mean error (bias) and precision for each system in comparison with the oximeter.

RESULTS

The overall error of the two-wavelength system was +0.15%, with a precision of +/- 2.52%. The three-wavelength system had an overall error of +3.71%, with a precision of +/- 2.30%. Overall correlation between catheter Svo2 and oximeter values was the same for both devices (r = 0.99).

CONCLUSIONS

Both currently available in vivo spectrophotometric systems are capable of producing satisfactory results over wide ranges of Svo2. In contradistinction to older reports, we found that the two-wavelength Svo2 system produced results equivalent to those obtained from the three-wavelength device. In this regard, there is no detectable advantage in accuracy to measuring in vivo Svo2 with three rather than with two wavelengths.

Oxygen uptake/oxygen supply dependency: fact or fiction?

More than a decade ago, observations of co-variance between VO2 and DO2 led to the identification of a condition known as pathological O2 supply dependency. This condition was subsequently observed in critically ill patients with sepsis and acute circulatory failure. More recently, other authors have challenged the existence of this condition, often citing methodologic problems or mathematical coupling to account for spurious observations in the earlier studies. Here, we review the evidence for and against pathological O2 supply dependency. We find that many of the arguments have some validity but only in specific circumstances. We conclude, therefore, that pathological O2 supply dependency is a hallmark of acute circulatory failure and that an effective therapeutic approach should be based on an evaluation of organ system function in each individual case. Parameters such as blood lactate, pHi and veno-arterial PCO2 may be useful in this respect.

Clinical and clinical laboratory correlates in sea otters dying unexpectedly in rehabilitation centers following the Exxon Valdez oil spill

Following the Exxon Valdez oil spill, 347 oiled sea otters (Enhydra lutris) were treated in rehabilitation centers. Of these, 116 died, 94 within 10 days of presentation. Clinical records of 21 otters dying during the first 10 days of rehabilitation were reviewed to define the laboratory abnormalities and clinical syndromes associated with these unexpected deaths. The most common terminal syndrome was shock characterized by hypothermia, lethargy, and often hemorrhagic diarrhea. In heavily and moderately oiled otters, shock developed within 48 hours of initial presentation, whereas in lightly oiled otters shock generally occurred during the second week of captivity. Accompanying laboratory abnormalities included leukopenia with increased numbers of immature neutrophils (degenerative left shift), lymphopenia, anemia, azotemia (primarily prerenal), hyperkalemia, hypoproteinemia/hypoalbuminemia, elevations of serum transaminases, and hypoglycemia. Shock associated with hemorrhagic diarrhea probably occurred either as a direct primary effect of oiling or as an indirect effect secondary to confinement and handling in the rehabilitation centers. Lightly oiled otters were less likely to die from shock than were heavily oiled otters (22% vs. 72%, respectively). Heavily oiled otters developed shock more rapidly and had greater numbers of laboratory abnormalities, suggesting that exposure to oil was an important contributing factor.

The effect of physostigmine on acid-base status in arterial and venous blood of anaesthetized rabbits following hypovolemic shock

1. The effects of physostigmine (70 micrograms kg-1, intravenously) on acid-base status in arterial and venous blood were studied in anaesthetized rabbits subjected to hemorrhagic hypovolemia. 2. Hemorrhagic shock was produced using intermittent bleeding of 50% of the estimated blood volume, during 30 min. Experimental group was treated with physostigmine (70 micrograms kg-1 body mass, intravenously) and the control group with the same volume (0.1 ml) of saline, immediately after bleeding. Blood samples were taken before and after bleeding (0, 15 and 60 min). 3. It was found that physostigmine increased the mean arterial blood pressure, did not change the heart rate, and improved survival of the animals. 4. These effects of physostigmine were associated with significant decrease in venous pH, produced mainly by increased PCO2. This can partly be explained in terms of additional vasoconstriction due to physostigmine action. 5. In arterial blood decreased pH, decreased standard bicarbonate, negative values of excess base and decreased PCO2 were observed both in physostigmine-treated and the control group of animals, indicating partly respiratory compensated metabolic acidosis. These findings indicate that the hypertensive effect of physostigmine in shock was not accompanied by more severe disturbance in arterial acid-base status than was observed in hypovolemic shock alone.

Influence of low dose allopurinol on ischaemia--reperfusion injury during abdominal aortic surgery

OBJECTIVES

To ascertain whether surgery causes ischaemia-reperfusion (I-R) related injury, if this injury is augmented by preoperative shock, and reduced with low dose allopurinol.

DESIGN

Randomised blind placebo controlled trial.

SETTING

Surgical laboratory.

MATERIAL AND METHODS

22 pigs were randomly allocated to four groups; OP = operation/placebo, OA = operation/ allopurinol, SOP = shock + operation/placebo, SOA = shock + operation/allopurinol. An aortic tube prosthesis was inserted in all. In groups SOP and SOA preoperative shock was induced by exsanguination. Allopurinol was administered in group OA on the preoperative day and peroperatively, in group SOA during shock and peroperatively.

CHIEF OUTCOME MEASURES

Perioperative blood concentrations of thiobarbituric acid reactive species (TBARS), ascorbic acid (AA), albumin, 99mTc-albumin and creatine phosphokinase (CPK) as indicators of oxidative membrane damage, antioxidant activity, microvascular permeability changes and muscular cell damage respectively.

MAIN RESULTS

In the OP and OA groups TBARS gradually increased, while AA, 99mTc-albumin and CPK remained unchanged and albumin decreased. No effect of allopurinol was observed in these groups. In the SOP group TBARS and AA were not significantly different from groups OP and OA. Yet, albumin, 99mTc-albumin and CPK decreased significantly more in the SOP group. Compared with the SOP group, allopurinol treatment (SOA) produced lower TBARS and higher AA levels, and reduced the effect of shock on albumin, 99mTc-albumin and CPK concentrations.

CONCLUSIONS

Aortic surgery causes no I-R related damage. Pre-operative shock produces I-R related damage, which is reduced by allopurinol.

Endothelin and hemodynamic responses to superior mesenteric artery occlusion shock and hemorrhagic shock in pigs

Endothelin is a novel, potent, endogenous vasoconstrictor derived predominantly from endothelium and macrophages. Release of endothelin-1 (ET-1) into biological fluids was determined by radioimmunoassay in pigs undergoing either a hemorrhagic (3 h) or superior mesenteric artery (SMA) occlusion (5 h) shock followed by reperfusion (90 min) or a control group which was observed for 8 h. After surgery, there was a significant increase in ET-1 in jugular and carotid plasma, lymph, and ascitic fluid in all three models. The portal plasma ET-1 level was significantly increased (p < .05, assessed by the Spearman rank coefficient rho) in both shock models, but no significant increase was noted in the control group. In the SMA occlusion shock model, four pigs died within 30 min of reperfusion, and these animals had a much higher level of portal ET-1 (22.3 +/- 5.5 fmol/mL) than the two pigs that were alive by the end of the observation period (11.5 +/- 1.3 fmol/mL). Reperfusion in the SMA occlusion shock model induced a critical form of circulatory shock characterized by hypotension, decreased cardiac output, and decreased left and right ventricular stroke work index, and death occurred usually within 90 min. Reperfusion of the shed blood in the hemorrhagic shock model almost normalized the hemodynamic derangements caused by the hypovolemia (with the exception of RVSWI), and the portal plasma and ascitic ET-1 levels decreased. These results indicate that ET-1 is released from the gut in response to both general hypoperfusion and selective intestinal ischemia and reperfusion.(ABSTRACT TRUNCATED AT 250 WORDS)

Does the initial distribution volume of glucose reflect plasma volume after haemorrhage in dogs?

To test the hypothesis that the initial distribution volume of glucose (IDVG) reflects plasma volume, the relationship between the IDVG and indocyanine green (ICG) assessments of plasma volume (Vd-ICG) were evaluated simultaneously both before and after induced haemorrhage (30 ml.kg-1) in eight mongrel dogs. The IDVG and the Vd-ICG were calculated with a one-compartment model from repeated measurements of plasma glucose three to seven minutes, and of plasma ICG three to nine minutes after simultaneous infusions of both glucose 100 mg.kg-1 and ICG 0.5 mg.kg-1. The IDVG calculated with a one-compartment model (IDVG-OCM) was also compared with a two-compartment model within 15 min (IDVG-TCM) on nine occasions among a total of 12 determinations. Using Bland and Altman analysis to compare the two analytical models, the IDVG-OCM tends to overestimate the IDVG-TCM by an average of 0.04 L. Although the IDVG-OCM was two to three times larger than the Vd-ICG at each corresponding point, a correlation was obtained between the IDVG-OCM and the Vd-ICG before and after induced haemorrhage (r = 0.85, n = 16, P < 0.001). We conclude that the IDVG reflects plasma volume in normal and hypovolaemic dogs, although the IDVG cannot be used directly to estimate plasma volume.

MEGX (monoethylglycinexylidide): a novel in vivo test to measure early hepatic dysfunction after hypovolemic shock

A quantitative liver test based on the formation of the lidocaine metabolite monoethylglycinexylidide (MEGX), was used to evaluate the effect of hemorrhagic shock at 40 mmHg for 90 min on Sprague-Dawley rats. After 2 h of stabilization, lidocaine was injected (2 mg/kg). A second group received volume resuscitation with Ringer's lactate over 1 h (15 mL/kg) after shock, and after 1 h of stabilization lidocaine was administered. These groups were compared to control animals. Blood samples were drawn at 0 time (baseline), prior to lidocaine injection, and at 10, 15, 30, and 60 min after lidocaine injection. MEGX values in shocked animals were significantly lower than in the control group; in animals receiving volume resuscitation, levels were higher than the shocked animals without resuscitation, but did not reach control levels. Thus, shock produced a significant depression of hepatocyte function, which was partially reversed by Ringer's lactate resuscitation. The MEGX test appears to be a suitable tool for clinical evaluation and therapeutic intervention after shock.

Accuracy of fingerstick glucose values in shock patients

BACKGROUND

Fingerstick blood glucose measurement has become widespread in both hospital and prehospital settings.

OBJECTIVE

To determine the accuracy of fingerstick blood glucose measurement in patients with poor peripheral perfusion (shock).

METHOD

Results obtained during three methods of glucose analysis (fingerstick blood glucose measurement; bedside and laboratory glucose analysis) were examined prospectively on 38 patients from inpatient medical and surgical critical care units or the emergency department of a large tertiary care referral center.

RESULTS

The means of the three glucose measurements were significantly different. Univariate analysis of the mean laboratory glucose value versus the mean fingerstick glucose value was significantly different. The mean venipuncture glucose measured by the bedside glucose meter versus the mean venous laboratory glucose was not significantly different.

CONCLUSION

These results suggest that fingerstick blood samples should not be used for bedside glucose analysis in patients who may have inadequate tissue perfusion.

Clinical, hematologic, and biochemical findings in dogs after induction of shock by injection of heartworm extract

A crude, whole-body extract of female or male heartworms was injected IV into 28 dogs with and 22 dogs without heartworm (HW) infection. The female HW extract caused shock in 22 of 24 dogs with and 12 of 20 dogs without HW infection. The male HW extract induced shock in 4 of 4 dogs with and 1 of 2 dogs without HW infection. Prevalence of shock caused by female HW extract was significantly (P < 0.05) higher in dogs with than without HW infection; shock developed 5 to 30 minutes after HW injection. These signs were observed: marked decrease in blood pressure; collapse (initial collapse); paleness of mucous membranes; weak heart sounds; dyspnea; skin coldness; intestinal hyperperistalsis, and defecation; increases in RBC count, serum total protein concentration, serum osmolality, serum Na and blood glucose concentrations; and decreases in neutrophil, eosinophil, and platelet counts. Alanine transaminase, alkaline phosphatase, and lactate dehydrogenase activities increased substantially from the time of initial collapse to 24 hours after HW injection. Of 39 dogs with shock, 29 recovered from initial collapse, but 5 of the 29 subsequently collapsed again (secondary collapse), with bloody diarrhea followed by death. Of these 39 dogs, 6 died during initial collapse without bloody diarrhea, and 4 were euthanatized during initial collapse. It was confirmed that HW extract had, in fact, induced shock. These clinical, hematologic, and biochemical findings were fundamentally similar to those associated with shock resulting from administration of drugs, such as diethylcarbamazine and milbemycin D, in microfilaremic dogs with HW infection.

Defining and achieving optimum therapeutic goals in critically ill patients

Patients who are critically ill with sepsis, shock, respiratory failure, trauma, or major surgical procedures may have reduced morbidity and mortality when hemodynamic and oxygen transport variables are augmented to values higher than those traditionally considered normal. Lactate production and suboptimum oxygen transport values are associated with anaerobic metabolism and insufficient tissue oxygenation. Since lactate can be a marker of inadequate tissue oxygenation, serial lactate measurements may be useful in individualizing therapy to reverse tissue hypoxia. Optimum hemodynamic and oxygen transport values are highly individual, and no accepted method has been established for guiding therapy. These values, together with plasma lactate concentrations, may assist in individualizing therapy in critically ill patients. No consensus can be reached at this time as to which specific therapeutic end points are optimal, how to achieve these end points, and which subset of patients will benefit from this therapy.

Blood coagulopathy in dogs with shock induced by injection of heartworm extract

A crude, whole-body extract of female heartworms was administered IV to 10 dogs with and 13 dogs without heartworm (HW) infection. Shock developed in 8 of 10 infected dogs and 11 of 13 non-infected dogs, and blood coagulopathy was observed in 12 of 19 dogs with shock. Prevalence and severity of blood coagulopathy were proportionate to prevalence and severity of shock. Platelet count decreased in all dogs with shock with or without blood coagulopathy; thus, the decrease in platelet count might be related to shock. In 4 dogs, activated partial thromboplastin time (APTT) was prolonged--192.0 seconds at 30 minutes after HW injection--and prothrombin time (PT) was increased--13.8 seconds at initial collapse. In 8 dogs, APTT was increased--200 seconds for 2 hours after HW injection--and PT was increased--200 seconds at 30 minutes after the injection. The APTT prolongation might have been caused mainly by decreases in activities of factors VIII, IX, XI, and XII of the intrinsic blood coagulation pathway. In dogs with severely prolonged PT, plasma fibrinogen concentration and factor II activity decreased slightly. Prolonged PT was corrected in vitro by addition of normal plasma at high concentration (> 80%), but prolonged APTT could not be corrected in vitro by addition of 80% normal plasma. Serum fibrin degradation products concentration was < 10 micrograms/ml, and soluble fibrin monomer complex was negative in all dogs. Thrombi were not found in blood vessels of any organ at necropsy and after histologic study. Therefore, it was suggested that blood coagulopathy resulting from inhibition of coagulation factor activities might develop in shock induced by HW extract.

The serum osmole gap

Estimation and measurement of serum osmolality can be of value in the clinical management of certain forms of critical illness. Osmolality is a measure of the concentration of osmotically active particles, or solutes, in a solution. Only low-formula weight ions and uncharged molecules that are present in relatively high concentrations contribute significantly to serum osmolality. Serum osmolality can be easily estimated from the three major osmotic constituents of normal serum (sodium, urea, and glucose) by a simple formula. An understanding of serum osmolality, its laboratory measurement, its bedside estimation, and the concept of the osmole gap, is crucial in making a preliminary diagnosis of methanol and ethylene glycol intoxication, as well as a few other related compounds. There are important caveats to this use of the osmole gap, because under certain circumstances both false-positive and false-negative interpretations may occur. The osmole gap may also be helpful for confirming pseudohyponatremia, as a gauge for dosing mannitol and glycerol when used to treat intracranial hypertension, and as a prognostic indicator in circulatory shock.

Sex steroid hormones in circulatory shock, sepsis syndrome, and septic shock

METHODS

Estrone (E1), estradiol (E2), testosterone (T), FSH, and LH levels were daily measured during a ten day period in 50 critically ill patients (38 men, 12 post-menopausal women). Patients were separated into four groups: A) no circulatory failure, no sepsis, B) sepsis syndrome without circulatory failure, C) circulatory failure without sepsis syndrome, D) septic shock. Results of hormonal measurements were compared 1) among the 4 groups, 2) between male and female patients, 3) between septic and nonseptic patients. The potential for the infusion of the vasoactive drug dobutamine to induce sex hormonal changes was documented in ten additional septic shock patients by measuring cortisol, E1, and T at base-line and after dobutamine infusion. Changes in active renin and plasma renin activity (PRA) were used as indirect witness of the dobutamine-induced beta 2-stimulation.

RESULTS

A dramatic increase in E1 and E2 levels was observed in women of groups B and D, and only in male patients of group D. In the septic patients, estrogen levels peaked at days 1 and 2 and trended to normal from day 6 after the onset of sepsis, while FSH and LH decreased. No difference was found between survivors and non-survivors. Whatever the group, male patients had low T levels throughout the study. Dobutamine induced a significant increase in active renin levels and a decrease in the regression slope between renin and PRA. Cortisol levels remained normal. No significant change in E1 and T was observed after dobutamine.

CONCLUSIONS

High estrogen levels were specifically observed in patients with sepsis and septic shock, either males or females. Decreased LH and FSH levels were consistent with the negative feed-back effect of high estrogen levels on pituitary secretion. Circulating T levels were decreased in all male patients. We found no correlation between sequential estrogen levels and outcome. These levels were not modified by a dobutamine-induced beta-2 stimulation.

A simple method for calculating component dilution during fluid resuscitation: the Leuven approach

STUDY OBJECTIVES

To test the reliability of the Leuven approach, a balance between oversimplified empiric rules and more complex calculations requiring the use of nomograms or computers, to determine blood component dilution during large transfusions. To present schemes for blood component dilution and stabilization, as well as four examples showing the practicability of the method.

DESIGN

Prospective study.

SETTING

Orthopedic operating rooms at a university hospital.

PATIENTS

108 patients undergoing total hip replacement with expected large blood loss.

INTERVENTIONS

Component concentrations were measured after patient arrival in the recovery room. Blood loss was followed clinically.

MEASUREMENTS AND MAIN RESULTS

Preset target component concentrations [hematocrit (Hct) 31%; total serum protein (TSP) 5.0 g/dl; prothrombin time (PT) 50%; blood platelets (BLPL) 50,000/microliters)] were compared with concentrations measured on arrival in recovery after dilution and stabilization, according to the transfusion scheme. Average blood loss was 3,226 +/- 1,600 ml (mean +/- SD). End component concentrations were Hct, 33.4% +/- 3.3%; TSP, 5.2 +/- 0.5 g/dl; PT, 52% +/- 12%; BLPL, 97,000/microliters. Hct and TSP showed significant (p < 0.05) but clinically unimportant differences from target concentrations. Possible reasons for variability in end concentrations are discussed.

CONCLUSION

The Leuven approach produces reliable blood component concentrations after extensive transfusions. It allows the clinician to decide for himself or herself, in accordance with general consensus and the patient's individual needs, when to stabilize blood components.

Lactate monitoring with subcutaneous microdialysis in patients with shock: a pilot study

We describe the use of subcutaneous microdialysis for continuous sampling of lactate to monitor the plasma lactate concentration in eight patients with shock. The dialysate lactate concentrations were significantly correlated with the plasma lactate concentrations (r = 0.8229), but the linear regression lines varied between patients. Therefore, we used the individual regression line of each patient for calibration to calculate estimated plasma values from the dialysate concentrations. While the estimated values were linearly correlated to the plasma lactate values (r = 0.912), the 95% confidence interval of the estimated values was +/- 2.8 mmol/L. Thus, subcutaneous microdialysis does not allow accurate estimation of the plasma lactate concentration. In 3 of the 8 patients, there was a significant negative correlation between the dialysate/plasma lactate ratio and the plasma lactate concentration. This suggests that besides plasma lactate, other factors such as subcutaneous adipose tissue metabolism and blood flow, may influence subcutaneous sampling and dialysate lactate concentration as well. While microdialysis can be used for on-line sampling and continuous monitoring of the concentration of extracellular substances, for the purpose of plasma lactate monitoring, sampling probes should be designed that permit intravascular placement.

Pharmacokinetics from multiple intraosseous and peripheral intravenous site injections in normovolemic and hypovolemic pigs

OBJECTIVES

To examine: a) the rate and extent of delivery of radioactive tracers to the central circulation from the tibial, medial malleolar, distal femoral, and humeral intraosseous sites, as well as from a peripheral intravenous site; and b) the end-tidal CO2 response to injected sodium bicarbonate at these sites.

DESIGN

Prospective, descriptive study.

SETTING

Animal laboratory at a university medical center.

SUBJECTS

Twenty anesthetized and mechanically ventilated piglets were cannulated with 18-gauge bone marrow needles at intraosseous sites and 22-gauge Teflon catheters in peripheral veins. A 22-gauge angiocath was placed in the right carotid artery of each subject. Drug kinetics were studied in the normovolemic and hypovolemic (acute bleeding of 25 mL/kg) states.

INTERVENTIONS

Sodium bicarbonate (1 mEq/kg) was injected into each of the three intraosseous and one intravenous sites with simultaneous monitoring of end-tidal CO2. A 10-min period for stabilization was allowed between injections. Aliquots of 99mtechnetium were injected at randomly selected sites and blood samples were obtained at 1.5-sec intervals via carotid artery for radioactive counts. Experiments were repeated after withdrawal of 25 mL/kg of blood.

MEASUREMENTS AND MAIN RESULTS

Assessment by end-tidal CO2 monitoring after 1-mEq/kg injections of bicarbonate demonstrated a mean initial end-tidal CO2 increase at 12.8 secs and a mean maximal end-tidal CO2 increase of 8 torr (1.06 kPa), with no significant site differences noted. Radioactive tracer injections were detected in the carotid artery after 15.4 secs in normovolemic animals and after 21.4 secs in hypovolemic animals, with no significant site differences detected. The proportion of injected tracer at 2, 5, 10, 20, 30, and 40 mins identified no significant differences between various intraosseous and intravenous sites.

CONCLUSIONS

Our study demonstrated similar rapid transit and proportion of bicarbonate and radioactive tracers, reaching the central circulation from multiple intraosseous sites and a peripheral intravenous site. This finding suggests that adjustments in drug dosage may not be required, using various intraosseous locations as an alternative to peripheral intravenous drug therapy.

Circulating interleukin-8 concentrations in patients with multiple organ failure of septic and nonseptic origin

OBJECTIVES

Interleukin (IL)-8, a pro-inflammatory cytokine, is a potent chemoattractant factor and an activator of neutrophils produced by many cell types after stimulation by IL-1, tumor necrosis factor (TNF), or microbial products such as endotoxins. We investigated whether the presence of measurable IL-8 in plasma was associated with the clinical status of severely ill septic or nonseptic patients susceptible to the development of multiple organ failure.

DESIGN

Cohort study.

SETTING

A collaborative study between an intensive care unit and a research laboratory.

SUBJECTS

Circulating IL-8 concentrations were measured in the plasma of 27 patients with sepsis syndrome and in 16 patients with noninfectious shock because these two conditions put patients at risk for the development of multiple organ failure. Sixteen of 27 patients with severe infection and 13 of 16 patients with noninfectious pathologies developed multiple organ failure.

MEASUREMENTS AND MAIN RESULTS

A specific enzyme-linked immunosorbent assay (ELISA) for IL-8 was set up with a monoclonal and a rabbit polyclonal antihuman IL-8 using a sandwich technique. High concentrations of circulating IL-8 were found in the plasma of patients with sepsis syndrome. Among septic patients, a significant difference was observed between concentrations of IL-8 in survivors (n = 16) and nonsurvivors (n = 11) (81 +/- 13 pg/mL vs. 3326 +/- 1219 pg/mL, respectively; p = .001). A correlation was noticed between plasma IL-8 and IL-6 concentrations (r2 = .42; p = .001), while no correlation was observed between IL-8 and TNF-alpha values, or between IL-8 and IL-1 beta. Although the mortality rate of nonseptic, multiple organ failure patients was 92%, low plasma concentrations of IL-8 were found (78 +/- 34 pg/mL), while high plasma concentrations were measured in septic, multiple organ failure patients (mortality rate 69%) who were sampled at a similar stage. By contrast, increased IL-6 values were observed in both septic and nonseptic, multiple organ failure patients.

CONCLUSIONS

In septic patients, high amounts of circulating IL-8 concentrations correlate with fatal outcome, whereas only low plasma concentrations of IL-8 are present in patients with nonseptic, multiple organ failure. This finding suggests that the signals involved in the exacerbation of IL-8 production are different, depending on infectious or noninfectious etiology.

Thoracic impedance and pulmonary atrial natriuretic peptide during head-up tilt induced hypovolaemic shock in humans

Head up and down tilts were used for manipulating the central blood volume in eight volunteers. During head-up tilt thoracic electrical impedance (TI) increased from 36.7 (33.9-52.1) ohm (mean and range) to 41.9 (36.9-59.2) ohm, heart rate from 60 (49-72) to 80 (65-90) beats min-1 (P < 0.05) and decreased again to 57 (48-67) beats min-1 accompanying a fall in mean arterial pressure from 86 (76-97) to 54 (41-79) mmHg and in cardiac output from 9.2 (5.9-12.1) to 6.9 (3.4-8.8) 1 min-1 (n = 7, P < 0.07). Central venous pressure did not change significantly. Pulmonary arterial mean, 6 (3-12) mmHg, and wedge pressures, 4 (1-9) mmHg, decreased to 4 (1-11) and 1 (0-7) mmHg, respectively, and mixed, 78 (77-79%), and central venous oxygen saturations, 72 (71-73)%, fell to 62 (46-75) and 54 (44-58)%, respectively (P < 0.05). Atrial natriuretic peptide (ANP) was determined from blood of the superior vena cava and pulmonary and brachial arteries. Pulmonary artery ANP, 18.4 (7.5-30.7) pmol l-1, was higher than in vena cava, 13.3 (5.2-20.9) pmol l-1 (P < 0.05). At the time of presyncope, pulmonary artery ANP decreased from 20.8 (37.4-10.1) to 13.7 (19.7-5.7) pmol l-1, in vena cava from 13.8 (23.1-7.1) to 10.2 (17.9-6.7) pmol l-1 and in the brachial artery from 16.9 (34.1-5.2) to 11.3 (18.5-5.1) pmol l-1 (P < 0.05). Head-down tilt did not affect the recorded variables significantly. Thoracic electrical impedance, pulmonary artery pressure and venous oxygen saturations were sensitive indices of the central blood volume as reflected in the release of atrial natriuretic peptide from the right side of the heart.

Plasma lipid peroxidation in critically ill patients: importance of mechanical ventilation

Oxygen free radicals may be implicated in the pathogenesis of both ischemia-reperfusion damage and in circulatory shock. The attack on the cell membrane by free radicals leads to lipid peroxidation, which can be assessed by the plasma malondialdehyde (MDA) level. The aim of this study was to determine the importance of lipid peroxidation in critically ill patients. The MDA level was measured by the thiobarbituric acid test. Nineteen patients at an early stage of circulatory shock, 11 patients in the weaning period of ventilation, 9 gastro-enterological patients without cardio-circulatory distress or sepsis, and 9 healthy volunteers were studied. The MDA level was higher in critically ill patients than in control subjects (61% in patients with shock and 40% in patients on mechanical ventilation). No correlation was found between the MDA level and the outcome: multiple organ failure or acute respiratory distress syndrome. This proposal leads to the question of systematic antioxidant therapy in intensive care patients.

Predictors of outcome from critical illness. Shock and cardiopulmonary resuscitation

Many of our patients in ICUs suffer from shock, be it due to sepsis, trauma, arrest, or other causes. These patients continue to have a very high mortality rate in spite of very labor intensive and expensive treatment. The ability to identify patients who are likely to succumb to their illness is of utmost importance. Of the multitude of scoring systems published, the APACHE seems to accurately stratify shock patients according to severity of illness. However, these systems tend to be more useful for stratifying risk groups of patients than assessing the risk of death. Hemodynamic data can specifically assess the severity of the shock state in an individual patient. Those who maintain a relatively low cardiac index (< 4.5 L/m/M2) and oxygen delivery (< 15 mL/m/kg or 600 mL/m/M2) have persistent tissue hypoperfusion. Arterial lactate concentrations reflect the severity of this perfusion defect and correlate with outcome. Therefore, by restoring tissue perfusion, we can clearly improve mortality. CPP, although not generally obtainable during cardiac arrest, is the major physiologic determinant of outcome from CPR. ETCO2 monitoring during cardiac arrest in humans correlates with resuscitability, however, provides a rapid noninvasive monitor of cardiac output, and therefore has secured its role as an invaluable tool for assessing the effectiveness of CPR. An ETCO2 over 10 mm Hg is associated with effective CPR. A rapid rise in ETCO2 during CPR heralds recovery of spontaneous circulation. In conclusion, the use of prognostic indicators as predictors of outcome is supported as an important adjunct to the management of critically ill patients. These indicators serve as useful monitors to evaluate treatment and guide clinical management. Understanding the underlying pathophysiologic mechanisms responsible for the wide variety of illnesses associated with circulatory failure is crucial in our concerted effort to reduce mortality in these patients. As knowledge is gained, we hopefully will be able to develop more accurate and specific predictors of outcome to prudently select patients most likely to benefit.

Resuscitation from hypovolemia in swine with intraosseous infusion of a saturated salt-dextran solution

Prehospital fluid resuscitation of traumatic injury is limited by difficulty in delivering large volumes of fluid in the field and time delays associated with gaining vascular access. We addressed these limitations in 14 anesthetized swine by evaluating a highly efficient volume expander, a near-saturated salt-dextran solution (SSD) administered through a new device, which gains vascular access via intraosseous (IO) infusion into the sternal bone marrow. After a steady-state baseline was achieved, all animals were hemorrhaged to 45 mm Hg for one hour. Half of the hemorrhaged animals were infused intraosseously with either normal saline (NS) or SSD until cardiac output was restored to the baseline value. No further infusion was given and animals were monitored for 2 hours. Both regimens were able to restore cardiac output to the baseline value, but only 1.3 +/- 0.1 mL/kg of SSD was required vs. 31.6 +/- 6.3 mL/kg for NS. In addition, cardiac output was better sustained after 2 hours with SSD than with NS. No deleterious effects of IO infusion of SSD were observed. From the improvement in cardiovascular variables and the lack of significant sternal or pulmonary pathologic perturbations, these data suggest that IO infusion of SSD can effectively treat hypovolemia and may allow field treatment when logistic considerations make conventional resuscitation impractical.