External pacing does not potentiate allopurinol protection of the heart from liver ischemia-reperfusion -- a study in an isolated perfused liver-heart rat model

BACKGROUND

We recently demonstrated that isolated paced hearts perfused with modified Krebs-Henseleit solution containing high dose allopurinol (1 mM) were protected from liver ischemia-reperfusion (IR)-induced reperfusion injury. The objective was to study the effects of low dose allopurinol together with external pacing in attenuating myocardial reperfusion dysfunction following liver IR in the same double organ model.

MATERIAL AND METHODS

Isolated rat livers were perfused with modified Krebs-Henseleit solution (groups 1 and 2, n=8/all groups) or underwent global ischemia (groups 3-6) for 120 minutes. Following a 15-minute conjoint reperfusion of earlier separately isolated liver+heart, the hearts were recirculated alone for additional 45 minutes. The organs of three-group donating animals (groups 2, 4, and 6) were treated with allopurinol 18 hours and 1 hour before the experiment (50 mg x kg(-1) intraperitoneally) and it was also added during perfusion (0.1 mM in Krebs). The hearts in groups 5 and 6 were paced (300 x min(-1)).

RESULTS

The hearts perfused with IR Krebs (group 3) experienced decreased myocardial left ventricular-developed pressure (LVP), heart rate (in the unpaced hearts) and later coronary flow (by 68%, 21% and 32%, respectively); LVP and coronary flow also decreased correspondingly in the IR-paced hearts (group 4). Xanthine oxidase (XO) was high in groups 3 and 4 compared to group 1. IR allopurinol-treated hearts, both unpaced and paced (groups 5 and 6) had normal, similar myocardial performance, while their circulating XO was as low as in group 2 (allopurinol-treated controls).

CONCLUSIONS

External pacing in the double organ, isolated-perfused liver-heart did not ameliorate XO-mediated dysfunction compared to low dose allopurinol. The unexpected delayed coronary insufficiency in myocardial reperfusion injury is discussed.

Perioperative care of children with nerve agent intoxication

Nerve agents (NA) present a major threat to civilian populations. When a ballistic system is used for spreading poison, multiple trauma, as well as toxic trauma could be caused. Children are more susceptible, due to their smaller physiological reserve. Urgent surgical intervention for combined intoxication in the multiple-traumatized child could be a tremendous task in view of the background of physiological instability. Nerve agents affect the autonomic, as well as the central nervous system, leading occasionally to unexpected interactions with agents normally used for resuscitation. This can cause additional instability, and possibly systemic collapse. This review presents and emphasizes points concerning treatment of a child who suffers from combined multiple and toxic traumas. The review is based on scant knowledge of a database of similar cases of pesticide organophosphate poisoning in children since these compounds are alike. We also extrapolated data from reports concerning episodic civilian exposure to NA.

Liver glutathione level influences myocardial reperfusion injury following liver ischemia-reperfusion

BACKGROUND

N-acetyl-L-cysteine (NAC) both replenishes reduced glutathione (GSH) and mitigates reperfusion injury. We hypothesized that liver content of GSH could affect remote myocardial reperfusion injury following liver ischemia-reperfusion.

MATERIAL AND METHODS

Following stabilization (30 min), isolated rat livers (6/group) were perfused with Krebs-Henseleit solution (two control groups) or made globally ischemic (two ischemia groups) for 120 min. Paired livers + paced hearts (Langendorff preparation) were then reperfused for 15 min after which the hearts were recirculated alone for 50 min. NAC was added to Krebs (2 mM) that perfused livers during stabilization and reperfusion phases in one control and one ischemia group.

RESULTS

GSH levels in the two control liver groups were identical (30.1 +/- 5.7 [SD] nmol/mg protein), and similar to that of the ischemia + NAC livers (28.6 +/- 2.8) but 2-fold that of the ischemia + 0 livers (15.8 +/- 2.4 nmol/mg protein, p<0.05). While hearts paired with control livers maintained unchanged their myocardial velocity of contraction, the contraction in the ischemia + NAC-paired hearts reduced, but was better than in the ischemia + 0-paired hearts (71 +/- 8% vs. 41 +/- 6% off baseline, p<0.05). Coronary flow also decreased dissimilarly in the two ischemia-associated groups of heart: 72 +/- 9% (ischemia + NAC) vs. 46 +/- 7% (ischemia + 0, p<0.05). Xanthine oxidase in the ischemia + 0 livers was 7.5-folds higher than in the ischemia-treated livers.

CONCLUSIONS

NAC treatment of ischemia-reperfused livers, associated with GSH replenishment, prevents remote myocardial reperfusion injury. The role of NAC and GSH in reducing liver-associated oxidative burst propagation is discussed.

Selective attenuation of acute lung ventilatory injury by methylene blue after liver ischemia-reperfusion: a drug response study in an isolated perfused double organ model

BACKGROUND

Liver transplantation-related ischemia-reperfusion (IR) is associated with the generation of stress oxidants that can spread damage remotely. Methylene blue (MB) had been shown to reduce lung neutrophils sequestration after in vivo intestinal IR and to have a dose-dependent potential for abrogating oxidant-induced ex vivo aortal ring reperfusion injury after liver IR. We now investigated MB's dose-dependent capabilities in preventing acute lung injury after the same liver IR.

METHODS

Wistar rat livers (eight replicates/group) were perfused (control) with modified Krebs-Henseleit solution or put globally in no flow (IR) conditions for 2 hr. Separately prepared lungs were then paired with livers and "reperfused" (15 min) together. The livers were then removed, and the lungs were left to recirculate alone with the accumulated Krebs for 45 min. Three additional control and three IR groups were reperfused with Krebs containing 20, 40, or 60 mg/kg MB at concentrations of 42, 86, or 128 microM.

RESULTS

All IR livers had hepatocellular and biochemical abnormalities compared with normal functions in the controls. Liver IR was associated with a 50%-75% increase in lung ventilation and perfusion pressures, vascular resistance and decreased compliance, and abnormal bronchoalveolar lavage (BAL) volume and content. Adding 42 and 86 microM MB selectively maintained normal the vascular parameters, intra-experimental lung weight gain, BAL indices, and wet-to-dry ratios. MB128 microM but not 42 or 86 microM best prevented IR-induced deterioration in lung ventilatory pressure and compliance.

CONCLUSIONS

MB selectively affords maintenance of normal lung ventilatory versus vascular measures after liver ischemia-reperfusion. Its proposed differential mechanism of action is discussed.

Methylene blue abolishes aortal tone impairment induced by liver ischemia-reperfusion in a dose response manner: an isolated-perfused double-organ rat model study

Liver ischemia-reperfusion (IR) generates remote organ reperfusion injury attributable to oxidative mediators. We tested the protective properties of methylene blue (MB) on aortal dysfunction. An ex vivo rat liver-aortal ring model was used to study the results of aortal exposure to post-ischemia (IR) hepatic effluent and its response to phenylephrine and isosorbide dinitrate in the absence or presence of increasing concentrations of MB in the effluent. Aortal incubation with IR effluents resulted in abnormal contraction. Ring's response to the vasoactive drugs was abnormally weak both during and following this exposure. Return to stabilization tone was irregular. MB (1.28 mM) best avoided overall dysfunction; 0.86 mM was partially effective, and 0.42 mM was ineffective. Nitrite/nitrate levels were similar to controls in the only IR 1.28 mM perfusate. Liver IR interferes with aortal tone and its response to vasoactive drugs, probably via oxidative interaction with nitric oxide. MB reverses these effects in a dose-dependent fashion.

Dextromethorphan attenuation of postoperative pain and primary and secondary thermal hyperalgesia

PURPOSE

To determine the effect of 90 mg dextromethorphan (DM) p.o. vs placebo 90 min preoperatively, on the immediate and delayed postoperative course.

METHODS

Thirty patients undergoing laparoscopic cholecystectomy or inguinal hernioplasty under general anesthesia were studied. Half (DM) received 90 mg dextromethorphan and half received placebo 90 min before anesthesia. Intravenous Patient Controlled Aanalgesia with morphine was available for two hours within a six-hour observation period; 75 mg diclofenac i.m. prn was given later in PACU and on-ward (24 hr). Pain was assessed using the visual analogue scales. Thermal thresholds for cold and hot sensation and for pain (by limit method) were evaluated at the site of skin incision (primary-) and distantly (secondary hyperalgesia). Von Frey filaments were applied testing touch sensation. Sedation level and morphine consumption were also assessed in PACU.

RESULTS

Demographic, surgical and perioperative parameters were similar; no untoward effects were encountered. Pain intensity and sedation were lower, and the feeling of well-being was greater, in the DM patients: one vs five (median), two vs five, five vs two, respectively, P <0.01 (90 min time-point). Thermal application revealed absence of primary and secondary hyperalgesia only in the DM patients; von Frey filaments induced similar pain sensation in both groups. Mean morphine/group, morphine/weight and diclofenac injection rates were approximately 55% lower in the DM group: 2.1 +/- 1.2 (SD) vs 4.7 +/- 2.3, 0.03 +/- 0.02 vs 0.07 +/- 0.03, 1.0 +/- 0.3 vs 2.4 +/- 0.2, respectively, P <0.01.

CONCLUSIONS

Compared with placebo, DM enabled reduction of postoperative analgesics consumption, improved well-being, and reduced sedation, pain intensity and primary and secondary thermal hyperalgesia.

Lung preconditioning with N-acetyl-L-cysteine prevents reperfusion injury after liver no flow-reflow: a dose-response study

BACKGROUND

Circulating xanthine oxidase activity and the generated oxidants have been linked to lung reperfusion injury from no flow-reflow conditions in other organs after organ transplantation or surgery. N-acetyl-1-cysteine (NAC), an oxidant scavenger, promotes glutathione in its reduced form (GSH) that is depleted during ischemia. We have recently demonstrated its efficacy in protecting lungs from reperfusion injury if administered during reperfusion of postischemic liver. We now investigated whether preconditioning of lungs with NAC could attenuate lung respiratory or vascular derangement after no flow-reflow (ischemia-reperfusion, IR) and if this depends on lung GSH levels.

METHODS

Rat isolated livers were stabilized and perfused with modified Krebs-Henseleit solution (KH) (control, n=12) or made ischemic (no flow, IR-0, n=12) for 2 hr. Meanwhile, lungs were isolated, ventilated, and stabilized (KH+bovine albumin 5%). Serial perfusion (15 min) of liver+lung pairs took place followed by lung only recirculation (45 min) with the accumulated solution. Another three controls and three ischemic groups included lungs treated during stabilization with NAC at 100 mg x kg(-1), 150 or 225 mg x kg(-1) (in 2.5, 3.7 or 5.5 mmol solutions, respectively). Results. Ischemic liver damage, expressed by circulating hepatocellular constituents, was associated with pulmonary artery and ventilatory pressure increases by 70-100% of baseline, abnormal wet-to-dry weight ratio, and abnormal bronchoalveolar lavage volume and content in the IR-0 (nontreated) and the IR-100 and IR-225 pretreated lungs. NAC-150 pretreatment afforded preservation for most parameters. GSH content in the IR-150 lung tissue was only 11% higher than that of IR-225, but 2-fold that in IR-0 and IR-100 GSH lungs.

CONCLUSION

Lung preconditioning with NAC prevents reperfusion injury but not in a dose-related manner. Although enhanced GSH tissue content explains lung protection, GSH-independent NAC activity is another possibility.

Anaesthesia and critical care considerations in nerve agent warfare trauma casualties

Nerve agents (NA) (tabun, sarin, suman, VX) have been stocked around the world for some time and still present a major threat to civilian as well as to military populations. Since NA can be delivered through both an aerial spray system and a ballistic system, victims could suffer both NA intoxication and multiple trauma necessitating urgent surgical intervention followed by intensive care. These patients can be expected to be extremely precarious neurologically, respiratorily and haemodynamically. Moreover, their clinical signs can be misleading. Further exacerbating the problem is the fact that interactions of NA with the pharmacological agents used for resuscitation and/or during anaesthesia can aggravate organ instability even more and possibly cause systemic collapse. There are no protocols for perioperative critical care and early assessment or for the administration of anaesthesia for surgical interventions in such combined multiple trauma and intoxicated casualties. We propose a scheme for the administration of critical care and anaesthesia based on the scant anecdotal reports that have emerged after the occurrence of local accidents involving NA intoxication and on the neuropharmacological knowledge of the pesticide organophosphate poisoning database, these compounds being related chemical substances.

Flumazenil potentiation of postoperative morphine analgesia

OBJECTIVE

The goal of this study was to test the effect of concomitant administration of flumazenil (FL) and morphine (MO) on immediate postoperative analgesia and the MO requirement to control pain in human beings.

DESIGN AND INTERVENTIONS

Thirty-six patients undergoing inguinal hernioplasty under lidocaine epidural anesthesia were enrolled in this double-blind, randomized, controlled study. On the first complaint of pain, either MO (2 mg) only or MO (2 mg) plus FL (0.2 mg) was administered. Additional doses of the same medications administered via a patient-controlled analgesia device with a 10-minute lockout period were available thereafter. The study continued for 2 hours after the loading doses of the medications were administered, with an additional 2-hour period of observation.

RESULTS

Thirty-two patients completed the study. Both groups reached a similar satisfactory equianalgesic state (2 in a 0-10 visual analogue scale). The MO plus FL group consumed 9.5 +/- 1.1 mg of MO versus 14.1 +/- 1.1 mg of MO (p < 0.001) in the MO only group. The MO plus FL patients were subjectively (visual analogue scale) more comfortable and less sedated than the MO patients. "Fine" coordination (using an electronic maze) and "coarse" coordination (measured by transferring a pen from one hand to another as rapidly as possible with both arms placed inside an 80-cm metal frame) in the MO group were worse than in the MO plus FL group. End-tidal CO2 increased and blood pressure decreased in the MO group. There were few and insignificant side effects in the MO group. None of these patients required an MO antagonist, and recovery was prolonged in none.

CONCLUSIONS

Flumazenil afforded lower MO consumption during the immediate postoperative period. Cognitive, hemodynamic, and respiratory functions were better after MO plus FL than after MO alone.

The role of dextromethorphan in pain control

PURPOSE

To review the clinical benefits of dextromethorphan (DM) in pain management, describe its neuropharmacological properties.

SOURCE

A Medline search was made for experimental and clinical data on DM use from 1967 to date using keywords nociception, acute and chronic pain control, N-methyl-D-aspartate, antagonists, dextromethorphan.

PRINCIPLE FINDINGS

The 930 DM citations mostly described its antitussive, metabolic and toxicological aspects, animal studies and its possible role in minimizing post-brain ischemia complications in humans. The use of DM in acute pain revealed eight original studies involving 443 patients, as well as two preliminary reports and our own unpublished data on 513 patients. Most of the 956 patients had general anesthesia. Eight studies (154 patients) and one case report dealt with chronic pain management. This N-methyl-D-aspartate (NMDA) receptor antagonist binds to receptor sites in the spinal cord and central nervous system, thereby blocking the generation of central acute and chronic pain sensations arising from peripheral nociceptive stimuli and enabling reduction in the amount of analgesics required for pain control. DM attenuated the sensation of acute pain at doses of 30-90 mg, without major side effects, and reduced the amount of analgesics in 73% of the postoperative DM-treated patients. Studies in secondary pain models in healthy volunteers and in various types of chronic pain showed DM to be associated with unsatisfactory pain relief.

CONCLUSION

DM attenuates acute pain sensation with tolerable side effects. Its availability in oral form bestow advantages over other NMDA antagonists.

[FK506 (tacrolimus) does not increase hepatic damage due to hypoperfusion]

Deterioration of hepatic function following liver transplantation is a known complication, sometimes attributed to the use of cyclosporin A. Reaction to tacrolimus (Prograf), a relatively new and effective immunosuppressant drug, is thought to result in a much lower grade of organ dysfunction, especially in the transplanted liver. Using the ex-vivo rat model of isolated perfused liver, we evaluated hepatocellular damage and oxygen extraction when tacrolimus was administered following liver hypoperfusion. Tacrolimus did not worsen hepatic dysfunction caused by the hypoperfusion. Therefore using tacrolimus in the perioperative period might be safer than cyclosporin A, which tends to worsen hepatic damage in the presence of hypoperfusion.

Impairment of aortal tone by no flow-reflow conditions and its partial amelioration by mannitol

BACKGROUND

Although postischemic cardiac or pulmonary dysfunction can relate to the impact of remotely generated oxygen stress mediators on the heart, their direct effect on the vascular bed remains unresolved. Thus, we tested these remote effects in an ex-vivo double organ model.

METHODS

After stabilization With Krebs-Henseleit solution, isolated rat livers were either perfused or made ischemic for 2 hours. Aortic rings were stabilized, immersed in postischemic liver perfusates and their functions were tested. Some organs originated from donors fed with tungstate, whereas others had mannitol (0.25 g/kg) in the buffer.

RESULTS

Incubation of aortic rings with postischemic hepatic effluent resulted in protracted contraction. Spasm was slightly lesser when the livers were pretreated with tungstate or exposed to mannitol, but worse in pretreated rings. The return to basal tone was abrupt in all ischemia-reperfusion aortae. The response of the rings to phenylephrine under the influence of the ischemia-reperfusion hepatic effluent was deficient. Mannitol prevented most abnormal responses.

CONCLUSIONS

Aortal tone impairment can occur by direct influence of the ischemia-reperfusion liver. It cannot be attributed entirely to xanthine oxidase, but also to other hepatic-released factors.

N-acetyl-L-cysteine for preventing lung reperfusion injury after liver ischemia-reperfusion: a possible dual protective mechanism in a dose-response study

BACKGROUND

Acute lung reperfusion injury (ALI) frequently follows an ischemic event in another organ, such as organ transplantation. We recently demonstrated that lung priming with N-acetyl-L-cysteine (NAC) prevented liver ischemia-reperfusion (IR)-induced ALI pending on reduced glutathione (GSH) amount of replenishment. We now assessed the therapeutic effect of NAC-in preventing ALI caused by liver IR-if administered to the lung during liver reperfusion.

PROCEDURES

Rat isolated livers were stabilized (30 min) and then perfused with modified Krebs-Henseleit solution (control, n=20) or made globally ischemic (IR, n=20) for 2 hr. Rat lungs were isolated separately, ventilated, and stabilized (30 min) with Krebs plus 5% bovine albumin. Pairs of liver and lung were then reperfused together for 15 min, followed by only lung recirculation with the liver effluent for another 45 min. Three more controls (n=20 each) and three ischemic groups (n=20 each) included lungs which were treated with 100, 150 or 225 mg x kg(-1) NAC (0.5, 0.74, or 1.1 mmol, respectively) during the 15-min liver and lung reperfusion period.

RESULTS

Pulmonary artery and ventilatory pressures and vascular resistance increased by 60-80% of baseline, compliance decreased, and bronchoalveolar lavage volume and content were abnormally high in the IR-nontreated and the IR-100 lungs. Most parameters in IR-150 and IR-225 lungs remained almost similar to controls. Postinsult GSH content in IR-100, -150, and -225 lungs was at 20%, 110%, and 90% above the IR-nontreated lungs, respectively.

CONCLUSIONS

Lung treatment with NAC during its reperfusion with IR liver effluent prevented ALI. Lung GSH replenishment accounted for lung protection, but its content did not correlate directly with grade of protection; NAC itself seemingly afforded lung protection as well.

Cumulative damaging effect of liver hypoperfusion and cyclosporine a on the peribiliary capillary plexus: a study in an isolated dually perfused rat model

BACKGROUND

Cyclosporine (CsA) is an essential posttransplantation immunosuppressive drug. It may cause hepatotoxicity, mostly cholestasis, by unknown mechanism. CsA causes nephrotoxicity mainly by increased vascular resistance. We investigated the effects of CsA on the peribiliary capillary plexus, in an isolated, dually perfused (i.e., via the hepatic artery and the portal vein) rat liver preparation.

METHODS

After 30 min of stabilization with optimal flow (4 ml/min/g liver), four liver groups were perfused (control, n=5 each) and four groups were hypoperfused (n=5 each, 1 ml/min/g) for 120 min. This was followed by a 30-min optimal reperfusion phase, during which the controls and the hypoperfused groups were injected (60 sec) via the hepatic artery with CsA at high (3 mg/kg body weight in 1 ml) or low dose (0.03 mg/kg), cremophore (130 mg/kg), or saline (1 ml). A ninth group (n=5) underwent 2-hr ischemia and 30-min reperfusion to standardize liver damage. Dark nonradioactive microspheres (approximately 10 microm diameter) were injected via the hepatic artery 15 min after drug or saline injection.

RESULTS

Neither of the two CsA doses, nor cremophore controls, nor hypoperfusion alone caused entrapment of microspheres in the peribiliary circulation as assessed by light microscopy; perfusion pressures and resistances were also not altered. Significant arteriolar impaction and vasculature engorgement occurred in the hypoperfused plus high-dose CsA livers; hypoperfusion plus low-dose CsA or cremophore groups were minimally tainted. Vascular notable obstruction was associated with 15-40% increase in portal and arterial perfusion pressures and resistances, 50% decrease in oxygen extraction, and increase in lactate/pyruvate ratio, hepatocellular damage, and wet-to-dry weight ratio. Such findings were superior to those detected in the ischemic livers.

CONCLUSIONS

Acute single high-dose CsA injection, but not low-dose or cremophore, if combined with decreased flow, alters hepatic microcirculatory resistance. Possible correlations between such changes and clinical implications in organ transplantation are discussed.

Multiple organ dysfunction after remote circulatory arrest: common pathway of radical oxygen species?

OBJECTIVES

Cardiovascular, respiratory, and vascular dysfunction can follow trauma-induced no-flow-reflow states: hemorrhage, blunt trauma, or neurogenic shock. Liver ischemia-reperfusion (IR) induces remote lung damage by means of xanthine oxidase (XO) pro-oxidant activity. This damage was not proven in the heart, neither was the independent role of radical oxygen species (ROS) established in such cases. We investigated whether multiple organ dysfunction after a trauma-like IR is XO and ROS related and whether clinically used ROS scavengers could be beneficial.

METHODS

A controlled, randomized trial in which isolated rat livers, hearts, lungs, and aortic rings were perfused with Krebs-Henseleit solutions. After stabilization, livers were either perfused or made ischemic (2 hours). Then, pairs of liver plus heart, lung, or ring were reperfused in series (15 minutes), and then the second organ circulated alone for 45 minutes. Remote organ protection against the pro-oxidant hepatic-induced toxicity was evaluated by using allopurinol (1 mmol/L, heart), mannitol (0.25 g/kg, lung), or methylene blue (40 mg/kg, ring).

RESULTS

IR liver effluents typically contained high lactate dehydrogenase, XO, and uric acid concentrations compared with control organs. IR was associated with doubled lung peak inspiratory pressure and reduced static compliance. Myocardial velocity of contraction and relaxation decreased by one third of baseline, and rings contracted abnormally and responded inadequately to phenylephrine. Wet-weight to dry-weight ratios in the remote organs increased as well. Most remote reperfusion injuries were attenuated by the drugs.

CONCLUSION

Liver no-flow-reflow directly induces myocardial, pulmonary, and vascular dysfunction. These are likely mediated by XO and ROS. The tested drugs protected against these pro-oxidants, even in the presence of circulating XO.

Dissociation between the state of leukocyte adhesiveness/aggregation in the peripheral blood and the availability of the CD11B/CD18 and CD62L antigens on the surface of the cells in patients with stress

We adopted whole blood flow cytometry and direct labeling of the CD11b/CD18 and the CD62L antigens to study the relationship between their expression on the surface of peripheral leukocytes and the state of leukocyte adhesiveness/aggregation (LAA) as revealed by the leukergy test. We examined patients with infection/inflammation, acute stress and controls. The mean +/- S.D. channel fluorescence intensity of CD11b/CD18 antigen did not differ between patients with infection/inflammation (173 +/- 78) and controls (167 +/- 72). However, a significant (p < 0.0001) difference between these groups was noted regarding LAA state. There was a significant (p = 0.04) reduction in CD11b/CD18 in stress (135 +/- 60) and a significant (p < 0.001) increment in LAA. In both study groups, there was a significant reduction in CD62L. Patients were divided into those with CD11b/CD18 above and below the control's average. No correlation was found between the antigens and LAA. We assume that LAA in patients with stress state is CD11b/CD18 and CD62L independent.

Cross-sensitivity between isoflurane and diazepam: evidence from a bidirectional tolerance study in mice

We examined in mice the effect of chronic diazepam treatment on the sensitivity to isoflurane, and that of repeated isoflurane exposure on the sensitivity to diazepam. Mice were divided into four groups: group 1, treated with diazepam, 10 mg/kg i.p. twice daily; group 2, vehicle-treated controls; group 3, exposed to 3% isoflurane for 25 min twice daily; and group 4, untreated controls. After 14 days the effect of the treatment was assessed. Twenty-four hours after the last 10 mg/kg diazepam treatment, groups 1 and 2 received diazepam, 5 mg/kg i.p., and were subjected to the horizontal wire test (HWT). All control mice but only 10% of the diazepam-treated mice failed the HWT. Groups 1 and 2 were then exposed to increasing concentrations of isoflurane. Diazepam-treated mice (group 1) lost the HWT at 0.7+/-0.7%, compared with 0.6+/-0.1% in controls (group 2) (P<0.001); the ED50 was 0.75% vs. 0.65%. Group 1 mice lost the righting reflex at 0.94+/-0.07% isoflurane vs. 0.87+/-0.06% in group 2 (P<0.01); the ED50 was 0.93% vs. 0.82%. Recovery time was 175+/-161 s in group 1 vs. 343+/-275 s in group 2 (P<0.02). Twenty-four hours after the last of the repeated exposures to isoflurane, we examined the responses of groups 3 and 4 to increasing concentrations of isoflurane. Mice in group 3 lost the righting reflex at 1.0+/-0.06% isoflurane vs. 0.9+/-0.04% in controls (group 4) (P<0.001); the ED50 was 0.96% vs. 0.85%. Recovery time was 113+/-124 s vs. 208+/-126 s in groups 3 and 4 (P<0.09). Diazepam, 3 mg/kg i.p. administered to groups 3 and 4, caused loss of the HWT reflex in 33% of group 3 mice and in 82% of controls (group 4) (P<0.001). It appears that prolonged exposure to both diazepam and isoflurane caused reduced sensitivity to each drug separately, as well as to the other drug. This finding may strengthen the theory that inhalational anesthetics may act via the same mechanism as the benzodiazepines.

Antinociceptive effect induced by the combined administration of spinal morphine and systemic buprenorphine

We evaluated the antinociceptive effect of combined spinal administration of morphine and systemic administration of buprenorphine. Experiments were performed on male Wistar rats. Nociception was measured using the tail immersion test. Buprenorphine was injected intraperitoneally (IP) and morphine was injected intrathecally (IT) via a catheter implanted in the subarachnoid space. Interaction of drugs was analyzed using a dose addition model. Both IT (1-5 microg) morphine and IP (50-500 microg/kg) buprenorphine increased the latencies of nociceptive responses in a dose-dependent manner. IT morphine (4 microg) and IP buprenorphine (100 microg/kg) produced 62.9+/-6.3 and 48.8+/-6.6 percent of the maximal possible effect (%MPE), respectively. The combined administration of 2 microg of IT morphine and 50 microg/kg IP buprenorphine produced a %MPE of 97.1+/-3.4. The analysis of drug interaction revealed that IT morphine interacted with IP buprenorphine in a supraadditive manner while producing a potent antinociceptive effect.

IMPLICATIONS

The concurrent administration of spinal morphine and systemic buprenorphine produces an antinociceptive effect that is greater than what could have been predicted from individual dose-response curves. This mode of interaction allows maintenance at a significant level of analgesia with reduced doses of opioids, which minimizes the incidence of undesirable side effects.

Permissive hypercapnia ventilation in patients with severe pulmonary blast injury

OBJECTIVES

To describe our experience with the use of limited peak inspiratory pressure (PIP), volume-controlled ventilation, and permissive hypercapnia in patients with severe pulmonary blast injury.

METHODS

Patients with pulmonary blast injury were ventilated using volume-controlled, synchronized intermittent mandatory ventilation. Whenever PIP exceeded 40 cm H2O, the tidal volume was decreased to maintain PIP at less than 40 cm H2O. Whenever the arterial pH fell below 7.2, the ventilator rate was increased in increments of 2 breaths per minute until the arterial pH rose to 7.25.

RESULTS

Between 1994 and 1996, 17 patients with severe pulmonary blast injury (10 from enclosed space explosions and seven from open space ones), requiring mechanical ventilatory support were admitted to our intensive care unit. Four patients developed increasing PaCO2 levels (to 93 +/- 12 mm Hg) associated with the reduction in arterial pH that was corrected by increasing the ventilator rate. There was evidence of ventilator-induced pulmonary barotrauma. Of the 17 patients, 15 patients (88%) survived.

CONCLUSIONS

Limited PIP in a volume-controlled ventilation is a useful and safe mode of mechanical ventilation in patients with pulmonary blast injury.

Midazolam versus propofol for long-term sedation in the ICU: a randomized prospective comparison

OBJECTIVE

To compare the efficacy, safety, and cost of midazolam and propofol in prolonged sedation of critically ill patients.

DESIGN

Randomized, prospective study.

SETTING

General intensive care unit (ICU) in a 1100-bed teaching hospital.

PATIENTS

67 critically ill, mechanically ventilated patients.

INTERVENTIONS

Patients were invasively monitored and mechanically ventilated. A loading dose [midazolam 0.11 +/- 0.02 (SEM) mg.kg-1, propofol 1.3 +/- 0.2 mg.kg-1] was administered, followed by continuous infusion, titrated to achieve a predetermined sedation score. Sedation was continued as long as clinically indicated.

MEASUREMENTS AND RESULTS

Mean duration of sedation was 141 and 99 h (NS) for midazolam and propofol, respectively, at mean hourly doses of 0.070 +/- 0.003 mg.kg-1 midazolam and 1.80 +/- 0.08 mg.kg-1 propofol. Overall, 68% of propofol patients versus 31% of midazolam (p < 0.001) patients had a > 20% decrease in systolic blood pressure after the loading dose, and 26 versus 45% (p < 0.01) showed a 25% decrease in spontaneous minute volume. Propofol required more daily dose adjustments (2.1 +/- 0.1 vs 1.4 +/- 0.1, p < 0.001). Nurse-rated quality of sedation with midazolam was higher (8.2 +/- 0.1 vs 7.3 +/- 0.1 on a 10-cm visual analog scale, p < 0.001). Resumption of spontaneous respiration was equally rapid. Recovery was faster after propofol (p < 0.02), albeit with a higher degree of agitation. Amnesia was evident in all midazolam patients but in only a third of propofol patients. The cost of propofol was 4-5 times higher.

CONCLUSIONS

Both drugs afforded reliable, safe, and controllable long-term sedation in ICU patients and rapid weaning from mechanical ventilation. Midazolam depressed respiration, allowed better maintenance of sedation, and yielded complete amnesia at a lower cost, while propofol caused more cardiovascular depression during induction.

Direct induction of acute lung and myocardial dysfunction by liver ischemia and reperfusion

OBJECTIVES

To investigate whether liver ischemia and reperfusion (IR) directly affect functions of remote organs.

BACKGROUND

Cardiovascular and respiratory dysfunction follows hemorrhage, spinal shock, or trauma as a result of no-flow-reflow phenomena. Hepatic IR induces remote organ damage probably by xanthine oxidase and oxygen species.

MATERIALS AND METHODS

Isolated rat livers, lungs, and hearts were perfused with Krebs-Henseleit solutions. After stabilization, livers were either perfused or made ischemic. Then, livers and hearts or livers and lungs were reperfused in series, and the liver was disconnected and the second organ continued to perfuse with the accumulated effluents.

MEASUREMENTS AND MAIN RESULTS

Ischemic and reperfused liver effluent contained high lactate dehydrogenase and uric acid concentrations compared with controls; xanthine oxidase increased 60 to 100 times. Ischemic and reperfused lung peak inspiratory pressure almost doubled; airway static compliance halved; myocardial contractility decreased to 70% of baseline; wet weight-to-dry weight ratios of lungs and livers increased.

CONCLUSION

Ischemic and reperfused liver can directly induce myocardial and pulmonary dysfunction, presumably by oxidant-induced injury.

A risk-benefit assessment of flumazenil in the management of benzodiazepine overdose

The worldwide expansion in the use of benzodiazepines has led to their frequent, and often inappropriate, use and to increase in their involvement in self-induced poisoning and iatrogenic overdosing. Flumazenil is a specific and competitive antagonist at the central benzodiazepine receptor, reversing all effects of benzodiazepine agonists without tranquillising or anticonvulsant actions. Incremental intravenous bolus injections of flumazenil 0.1 to 0.3 mg are the most effective and well tolerated in the diagnosis and treatment of pure benzodiazepine overdose; additional boluses or an infusion (0.3 to 0.5 mg/h) can be given to prevent patients from relapsing into coma. Intravenous flumazenil 10 to 20 micrograms/kg is effective in neonates and small children. Intramuscular, oral (20 to 25 mg 3 times daily or as required) and rectal administration may be used as alternatives in long term regimens. Patients with mixed-drug overdose require higher doses (up to 2 mg bolus, approximately equal to 1 mg/h infusion) to regain consciousness. Children and the elderly, chronically ill patients, and pregnant women and their fetuses all respond satisfactorily to flumazenil, but the usefulness of the drug in patients with hepatic encephalopathy and alcohol overdose is debatable. The use of flumazenil results in complete awakening with restoration of upper airway protective reflexes, thus enabling gastric lavage to be performed and transfer of the patient from the emergency room to another hospital department. Resumption of effective spontaneous respiration allows for expeditious extubation, weaning off mechanical ventilation or the avoidance of endotracheal intubation. While flumazenil is not associated with haemodynamic adverse effects, caution should be exercised when using this agent in patients who have co-ingested chloral hydrate to carbamazepine or whose ECG shows abnormalities typical to those seen after overdose with tricyclic antidepressants (TCAs); the use of flumazenil in the presence of these drugs can sometimes induce treatable cardiac dysrrhythmia. Flumazenil per se does not induce adverse effects. Coma reversal by flumazenil may cause mild, short-lived reactions caused by sudden awakening. Withdrawal symptoms in long term benzodiazepine users and seizures in patients who have taken an overdose of TCA or carbamazepine and a benzodiazepine can occur with flumazenil; these symptoms are avoidable by utilising slow flumazenil dose titration.

Gut decontamination reduces bowel ischemia-induced lung injury in rats

OBJECTIVE

To evaluate the effects of gut decontamination on endotoxin, tumor necrosis factor (TNF) levels, and the associated lung injury in a rat model of bowel ischemia.

SUMMARY BACKGROUND DATA

Gut ischemia induces disruption of the intestinal mucosal barrier, allowing translocation of bacteria and endotoxin into the blood, which may trigger a systemic inflammatory response and lung injury.

METHODS

Thirty anesthetized rats were randomized into three groups: (1) ischemia-reperfusion (I/R) alone (a 60-min superior mesenteric artery occlusion and 4 h of reperfusion, n=10); (2) rats that underwent gut decontamination prior to ischemia (I/R+GD, n=10); and (3) control rats (sham operated, n=10). Serum levels of lipopolysaccharide (LPS) and TNF were measured at the end of the experiment. Lung permeability was measured using bovine serum albumin labeled with 125I, and organ injury was assessed histologically.

RESULTS

One hour of bowel ischemia and 4 h of reperfusion (I/R) led to elevations of blood LPS and TNF levels of 0.33+/-0.005 EU/mL and 173+/-56 pg/mL, which were higher than the sham group (p<0.01). Gut decontamination (I/R+GD) significantly attenuated the LPS and TNF generation, 0.09+/-0.005 and 56.2+/-6 pg/mL (p<0.01). Lung injury as assessed by pulmonary permeability index was also reduced by gut decontamination, 2.1+/-0.42 vs 5.3+/-0.82 in the control group (p<0.03). Surprisingly no difference was detected in the number of pulmonary neutrophils in sequestration between the groups.

CONCLUSIONS

Our data suggest that gut decontamination can reduce the generation of LPS, TNF, and the severity of lung damage that often follows ischemia and reperfusion of the intestine in rats.

The isolated post ischaemic rat heart is more vulnerable to protamine sulphate than the non-ischaemic heart

Protamine sulphate is currently used for the reversal of heparin anticoagulation but is known to cause direct myocardial depression. The purpose of this study was to compare the effects of protamine sulphate on the isolated heart with and without cardioplegic ischaemia. Isolated rat hearts (Langendorff preparation) were electrically paced at 300 beats/min and perfused with Krebs-Henseleit solution. Five groups were tested: (1) control: no ischaemia, no protamine; (2) no ischaemia, protamine; (3) no ischaemia, protamine (time-matched control to groups 4 and 5); (4) control: ischaemia, no protamine; and (5) ischaemia, protamine. Protamine sulphate was infused for 15 min at 10 microg/ml. In groups 4 and 5, cardioplegic ischemia was maintained for 30 min at 30 degrees C before protamine exposure. Protamine decreased myocardial performance in a time- and dose-dependent manner. Protamine depressed mean (s.d.) myocardial left ventricular pressure in both non-ischaemic hearts (groups 2 and 3, to 49(4)% and 50(4)% from baseline, respectively) and post ischaemic hearts (group 5, to 28(8%). Mean (s.d.) left ventricular-developed pressure only partially recovered after protamine in post-ischaemic hearts (to 55(13)% of baseline) compared with full recovery of the non-ischaemic group. Protamine depressed coronary flow to 70(5)% and 74(8)% in non-ischaemic hearts (groups 2 and 3, respectively) and to 58(7)% in group 5. Coronary flow recovered completely at the end of the experiments in all protamine-treated groups. In conclusion, isolated rat hearts subjected to cardioplegic ischaemia are more vulnerable to protamine than are non-ischaemic hearts.

Investigation of plasma membrane-associated apolipoprotein E in primary macrophages

Our previous studies identified the lysosome as the compartment for degradation of newly synthesized apoE in primary macrophages. Lysosomal degradation of newly synthesized apoE is extensive and rapid (> 50% in 60 min). In the present study we tested the hypothesis that the macrophage cell surface is part of the itinerary of apoE in its path to the lysosomes. We therefore examined the existence and size of the apoE pool associated with the macrophage cell surface. Such a pool may not only provide a mechanism of targeting apoE for lysosomal degradation, by endocytosis, but also have important implications for the metabolism of lipoproteins by macrophages. Treatment of macrophages with heparin (10 micrograms/ml and 5 mg/ml) and heparinase I (1 U/ml), which releases substantial amounts of apoE from HepG2 cells, results in no additional release of apoE from macrophages. Treatment of macrophages with xyloside (1 mM) or GRGDTP (500 micrograms/ml) does not decrease the extent of cell-associated apoE. Both immunogold labeling, followed by electron microscopy, and immunofluorescent labeling and light microscopy further confirm the lack of significant amounts of cell surface-associated apoE in macrophages. In contrast, immunolabeled apoE is readily observed in permeabilized cells. Taken together, these data indicate the absence of significant apoE-glycosaminoglycan interaction at the macrophage cell surface. The lack of such an interaction is likely due to paucity of heparan sulfate proteoglycans on the macrophage cell surface, when compared to hepatocytes. Along with our previous observations. (Deng. J., V. Rudick, and L. Dory, 1995. J. Lipid Res. 36:2129-2140), these results suggest direct targeting of a portion of newly synthesized apoE from trans-Golgi network to lysosomes for degradation, without involving the plasma membrane and endocytosis.

[Isolated limb perfusion with tumor necrosis factor for malignancies of the limbs]

Tumor necrosis factor (TNF) induces rapid necrosis in a variety of experimental neoplasms. However, its clinical application is limited by life-threatening systemic toxicity. Isolated limb perfusion (ILP) enables administration of large doses of TNF and cytotoxic drugs directly to the affected limb, avoiding systemic toxicity. We describe our experience in 20 consecutive patients (10 with melanoma and 10 with soft tissue sarcoma) treated with high-dose TNF and melphalan via ILP. ILP was performed via the external iliac (10 cases), femoral (2), popliteal (5) or brachial (3) vessels. Patients received 3-4 mg TNF to an upper, and 1-1.5 mg/kg to a lower extremity. Isolation efficiency was determined by injection of radiolabelled albumin. The procedure was successful in all 20 patients. Local complications included wound infection in 6 cases and hematoma in 2. 1 patient developed sepsis secondary to extensive necrosis of a large, secondarily infected tumor. The first 6 patients who underwent high-flow perfusion experienced systemic side-effects, mainly hypotension. These side-effects were eliminated when low-flow perfusion was introduced. The response rate was 100%. In the sarcoma group, 5/10 had complete response, and 5 partial response. Amputation or mutilating surgery was avoided in 9/10. Of the 10 with melanoma, 7 had complete, and 3 partial response. We conclude that administration of TNF via ILP is a safe and effective modality for treating advanced neoplasms of the limbs.

Administration of amphotericin B in lipid emulsion decreases nephrotoxicity: results of a prospective, randomized, controlled study in critically ill patients

OBJECTIVES

To evaluate the differences in efficacy and in clinical and biochemical tolerance to amphotericin B administered in a lipid emulsion compared with amphotericin B administered in 5% dextrose in water in the treatment of Candida albicans infection in intensive care unit (ICU) patients.

DESIGN

Prospective, controlled, randomized study, conducted during a 2.5-yr period, comparing the two treatment protocols.

SETTING

General ICU of a university-affiliated municipal hospital.

PATIENTS

Sixty consecutive critically ill patients with confirmed or suspected Candida infection.

INTERVENTIONS

Patients received amphotericin B (1 mg/kg/24 hrs), administered randomly in 5% dextrose in water (group A), or in lipid emulsion (20% intralipid) (group B).

MEASUREMENTS AND MAIN RESULTS

Clinical tolerance (fever, chills, hemodynamics), hepatorenal tolerance, and biological tolerance (serum electrolytes and coagulation profile) were evaluated. Patients receiving amphotericin B in lipid emulsion experienced a lower frequency rate of drug-associated fever (61.4% vs. 5.8%, p < .003) rigors (54% vs. 8.5%, p < .004), hypotension (17% vs. 0%), and nephrotoxicity (increase of serum creatinine concentration 66.7% vs. 20%, p < .0002). Significant (264,500 +/- 71,460 to 163,570 +/- 34,450 mm3, p < .01) thrombocytopenia, not associated with active bleeding, occurred in patients receiving amphotericin B lipid in emulsion but not in patients receiving the drug in dextrose.

CONCLUSIONS

Treatment with amphotericin B in a lipid emulsion when given to critically ill patients with Candida sepsis seems to be safer and as effective as the conventional mode of administration.

Use of flumazenil in the treatment of drug overdose: a double-blind and open clinical study in 110 patients

OBJECTIVES

To assess the efficacy, usefulness, safety, and dosages of flumazenil required when flumazenil is used in the diagnosis of benzodiazepine-induced coma (vs. other drug-induced coma), and to reverse or prevent the recurrence of unconsciousness.

DESIGN

A two-phase study: a controlled, randomized, double-blind study followed by a prospective, open study.

SETTING

An 800-bed, teaching, university-affiliated hospital.

PATIENTS

Unconscious patients (n = 110) suspected of benzodiazepine overdose, graded 2 to 4 on the Matthew and Lawson coma scale, were treated with flumazenil, the specific benzodiazepine receptor antagonist. The first 31 patients were studied in a double-blind fashion, while the rest of the patients were given flumazenil according to an open protocol. INTERVENTIONS; All patients received supplemental oxygen; endotracheal intubation was performed, and synchronized intermittent mandatory ventilation was initiated whenever it was deemed necessary. A peripheral intravenous cannula was inserted, as were indwelling arterial and urinary bladder catheters. Blood pressure, electrocardiogram, respiratory rate, end-tidal CO2, and core temperature were continuously monitored. The first 31 double-blind patients received either intravenous flumazenil (to a maximum of 1 mg) or saline, while the rest of the patients were given flumazenil until either regaining consciousness or a maximum of 2.5 mg was injected. Patients remaining unconscious among double-blind patients or those patients relapsing into coma after the first dose were later treated in the open phase of the study. Treatment continued by boluses or infusion as long as efficacious.

MEASUREMENTS AND MAIN RESULTS

Fourteen of 17 double-blind, flumazenil-treated patients woke after a mean of 0.8 +/- 0.3 (SD) mg vs. one of 14 placebo patients (p < .001). Seventy-five percent of the aggregated controlled and uncontrolled patients awoke from coma scores of 3.1 +/- 0.6 to 0.4 +/- 0.5 (p < .01) after the injection of 0.7 +/- 0.3 mg of flumazenil. These patients had high benzodiazepine serum blood concentrations. Twenty-five percent of the patients did not regain consciousness. These patients had very high serum concentrations of nonbenzodiazepine drugs. Sixty percent of the responders who had primarily ingested benzodiazepines remained awake for 72 +/- 37 mins after flumazenil administration; 40% relapsed into coma after 18 +/- 7 mins and various central nervous system depressant drugs were detected in their blood in addition to benzodiazepines. Seventy-one percent of the patients had ingested tricyclic antidepressants. Seventy-eight percent of the responders were continually and efficaciously treated for < or = 8 days. Fourteen (25%) of the intubated patients were extubated safely while 12 patients, who had shown increased respiratory insufficiency, resumed satisfactory respiration after flumazenil injection. Five cases of transient increase in blood pressure and heart rate were encountered. There were 27 mildly unpleasant "waking" episodes, such as anxiety, restlessness, and aggression, but no patient had benzodiazepine withdrawal signs, convulsions, or dysrhythmia, most noticeably absent in tricyclic antidepressant-intoxicated patients.

CONCLUSIONS

Flumazenil is a valid diagnostic tool for distinguishing pure benzodiazepine from mixed-drug intoxication or nondrug-induced coma. Flumazenil is effective in preventing recurrence of benzodiazepine-induced coma. Respiratory insufficiency is reversed after its administration. Flumazenil is safe when administered cautiously, even in patients with coma caused by a mixed overdose of benzodiazepine plus tricyclic antidepressants.

Lysosomal degradation and sorting of apolipoprotein E in macrophages

We previously reported that a substantial amount of newly synthesized apoE in mouse macrophages is degraded prior to secretion; a portion of this pool of apoE can be rescued by the addition of HDL3 to the incubation medium. In the present studies, the location and nature of the intracellular degradation of apoE were more closely examined. Inhibitors of protein trafficking (brefeldin A) as well as a number of protease inhibitors were used. The experiments using brefeldin A (5 micrograms/ml) clearly established that neither the endoplasmic reticulum nor the Golgi complex are the sites of apoE degradation. Using a pulse-chase design, [35S]apoE cannot be chased out in the presence of brefeldin A and remains undegraded within the cell. The accumulated apoE lacks the sialic acid residues, indicating that this final stage of processing must occur in the trans-Golgi network or later. Lysosomotropic agents, ammonium chloride and chloroquine, on the other hand, inhibit apoE degradation by over 70 and 80%, respectively, while total cell protein degradation remains unaffected. Similarly, a cocktail consisting of four lysosomal protease inhibitors (pepstatin, E-64, chymostatin, and antipain), inhibits specifically apoE degradation by over 60%. In contrast, ALLN, an inhibitor of Ca(2+)-dependent cysteine proteases, has a moderate effect on apoE degradation (30% inhibition) and a more pronounced effect on total protein degradation. These data suggest that the site of intracellular apoE degradation in the macrophage is the lysosome. These conclusions are supported by light and electron microscopy of macrophages, clearly showing the presence of immunoreactive apoE (along with cathepsin D) in the endosomal/lysosomal compartment of control and lysosomotropic agent-treated cells. In contrast, little or no labeling is seen in this compartment in brefeldin A-treated cells. At lower concentrations of the lysosomotropic agents, the extent of inhibition of apoE degradation is compensated for by its increased secretion, in a manner analogous to the effect of these agents on lysosomal enzymes. Higher concentrations of these agents, which lead to a profound inhibition of apoE degradation, also specifically block apoE secretion. The block in apoE secretion in the presence of high concentrations of chloroquine leads to undiminished or higher concentrations of immunoreactive apoE in the endosomal/lysosomal compartment, suggesting that apoE is targeted for lysosomal degradation directly, without prior secretion or surface association. These data strongly suggest pH-dependent sorting of apoE in macrophages to the degradative and secretory pathways and imply a protein-protein interaction in the process.

Soluble tumor necrosis factor receptors reduce bowel ischemia-induced lung permeability and neutrophil sequestration

OBJECTIVES

To evaluate the possible role of tumor necrosis factor (TNF) in the development of lung injury after bowel ischemia, and the ability of TNF-soluble receptors to negate TNF toxicity, using a rat small bowel ischemia and reperfusion model.

DESIGN

Prospective, randomized, controlled laboratory study.

SETTING

Research laboratory.

SUBJECTS

Forty adult male Sprague-Dawley rats weighing approximately 300 g.

INTERVENTIONS

The rats were divided equally into four groups: a) ischemia and reperfusion alone; b) those animals receiving TNF antibodies (1 mL) before reperfusion; and c) those animals receiving 200 micrograms of human recombinant TNF soluble receptors. These 30 anesthetized rats underwent 60 mins of superior mesenteric artery occlusion per 4 hrs of reperfusion. The remaining ten animals were sham operated (laparotomy), serving as controls. Lung permeability was measured using bovine serum albumin labeled with 125I, and organ injury was assessed histologically.

MEASUREMENTS AND MAIN RESULTS

Thirty and 60 mins after declamping and reperfusion, plasma TNF concentrations increased to 830 +/- 66 and 173 +/- 56 pg/mL, respectively, compared with 10 pg/mL before ischemia (p < .001). In sham-operated control rats, TNF concentrations did not increase from baseline concentrations. Four hours after reperfusion, sequestration of neutrophils in the pulmonary microcirculation was noted (319 +/- 60 vs. 84 +/- 13 neutrophils/10 high-power fields in sham-operated rats [p < .04]). Pulmonary microvascular leak also occurred, as measured by translocation of radiolabeled albumin into the bronchoalveolar space and expressed as the ratio of bronchoalveolar lavage to blood concentrations. This ratio was 5.3 +/- 0.8 in ischemic control animals compared with 1.1 +/- 0.3 in sham animals (p < .03). Treatment with antibodies to TNF before reperfusion attenuated the pulmonary injury (75 +/- 6 neutrophils/10 high-power fields, permeability index 1.6 +/- 0.1) less than in ischemic controls (p < .005). A similar protection was achieved with soluble TNF receptors, which prevented bowel ischemia-induced lung neutrophil sequestration (117 +/- 35 neutrophils/10 high-power fields, pulmonary vascular leak ratio of 2.3 +/- 0.1, p < .05).

CONCLUSIONS

The results of this study show that ischemia and subsequent reperfusion of the intestine in rats produce lung injury. This injury is mediated, at least in part, by TNF. Soluble TNF receptors are an effective tool in preventing lung TNF injury after intestinal ischemia.

Antinociception induced by simultaneous intrathecal and intraperitoneal administration of low doses of morphine

The application of morphine simultaneously into the spinal cord and brain ventricles produces a supraadditive antinociceptive effect. In this study, we attempted to determine whether combined intrathecal (IT) and intraperitoneal (IP) administration of small doses of morphine also produces such a synergistic antinociceptive effect. The experiments were performed on male Wistar rats. Nociception was measured using the tail immersion test. For IT administration morphine was injected through a catheter implanted in the subarachnoid space. Combined administration of small doses of IT (1 microgram) and IP (1 mg/kg) morphine resulted in a strong, highly significant antinociceptive effect. This effect was not only much higher than that produced by separate administration of the same doses of morphine, but also much higher than the expected effect of the combination. These results demonstrate that low doses of IT and IP morphine interact in a supraadditive fashion to produce potent analgesia.

Epidural morphine pretreatment for postepisiotomy pain

OBJECTIVE/DESIGN

A randomized double-blind controlled study was conducted on two groups of 45 parturients to evaluate the importance of the timing of epidural morphine administration for the relief of postepisiotomy pain. Both groups had preemptive analgesia by continuous lumbar epidural bupivacaine blockade. Upon completion of the episiotomy repair and before the onset of pain, the patients received epidural injections of 3 ml saline with or without 2 mg morphine in groups A and B respectively. When pain appeared, group A patients received an epidural injection of 3 ml saline while group B patients received 2 mg morphine in 3 ml saline. Postepisiotomy pain level was evaluated by a visual analogue scale.

RESULTS

The incidence of pain in group B women following epidural morphine administration was 68.6%. This was significantly higher than that of group A at 15.6% (p < 0.01). Furthermore, group B showed that the rate of effective pain relief after 2 mg epidural morphine significantly decreases as the level of pain intensity rises (p < 0.01).

CONCLUSION

Epidural morphine for postepisiotomy pain is much more effective if administered before the onset of pain.

Sternal wound infection: our experience with 200 cases

More than 200 patients with sternal wound infections have been treated in the Plastic Surgery Department of our Medical Center over the years 1984-1993. Most of these were referrals from other hospitals. In recent years, the cases have become more severe, partially due to the fact that cardiac surgeons tend to operate older and sicker patients more readily than they previously did. 80% of these were post coronary bypass surgery, and the others heart and heart-lung transplants, repair of congenital heart anomalies, valve replacements etc. Several of the cases were cardiac surgery re-do's. Risk factors for developing this complication, such as diabetes, obesity, technical errors of sternal incision, prolonged intubation, the use of aortic balloon, etc. will be discussed. Many of our earlier patients had chronic fistulae following conservative therapy with old treatment modalities. In recent years, patients are usually referred at the acute stage. Most patients undergo removal of sternum and ribs. Previously, reconstruction included mainly transfer of the rectus ahdominis muscle, whereas lately the pectoralis muscles is utilized. Omentum was used in only one case. The importance of pre-operative imaging procedures has been thoroughly studied in our series. Especially important is the definition of the extent of the infection, and localization of foreign bodies causing chronic infections, such as suture material, epicardial electrodes etc. A change in infectants has also been noticed. In the first half of the study period, Pseudomonas aeruginosa comprised at least 40%.(ABSTRACT TRUNCATED AT 250 WORDS)

Metabolic effects of continuous veno-venous haemofiltration in critically ill patients

OBJECTIVE

To evaluate the short-term metabolic and haemodynamic effects of continuous veno-venous haemofiltration (CVVH) in critically ill patients with acute renal failure (ARF).

DESIGN

Prospective study of nine consecutive critically ill patients with established acute oliguric renal failure.

SETTING

A general ICU in an 800-bed university hospital.

PATIENTS

Critically ill patients, mean age 56 +/- 6 years. Four had multi-organ failure, one had acute haemolytic uraemic syndrome, one had idiopathic lactic acidosis, two had haemorrhagic pancreatitis and one had urinary sepsis.

INTERVENTIONS

All patients were mechanically ventilated with arterial and pulmonary artery catheters in situ.

MEASUREMENTS AND MAIN RESULTS

Oxygen consumption (VO2), CO2 production (VCO2) resting energy expenditure (REE), continuous blood pressure, heart rate, central venous pressure (CVP), pulmonary artery pressure (PAP), and cardiac output (CO), as well as tidal and minute volumes, end-tidal CO2 and arterial blood gases, were continuously measured for one hour prior to and one hour following the institution of CVVH. Body temperature, arterial blood pressure, heart rate, CVP and pulmonary artery catheter data remained stable throughout the study period. Prior to CVVH, VO2 was 326 +/- 33 ml/min, VCO2 was 245 +/- 27 ml/min and REE was 2241 +/- 231 kcal/24 hours. Following institution of CVVH, VO2 was 324 +/- 33 ml/min, VCO2 was 244 +/- 27 ml/min and REE was 2227 +/- 230 kcal/24 hours.

CONCLUSIONS

CVVH does not affect metabolic rate and haemodynamic stability in critically ill patients. The lack of any effect on the metabolic rate and haemodynamic parameters in such patients may have significant clinical importance and it further attests to the suitability of CVVH for the treatment of critically ill patients.

Acute poisoning treated in the intensive care unit: a case series

A retrospective study on patients with acute poisoning admitted to the Intensive Care Unit (ICU) of the Ichilov Hospital over a 3-year period (1982-84) is presented. Of 419 patients seen in the Emergency Room for intoxication during these years, 71 (17%) required intensive care upon admission. Suicide attempts accounted for 90% of the ICU admissions, with drugs of the benzodiazepine (BDZ) group being the most commonly used (51%). Mixed-drug overdose was seen in 55% of the patients. There was a poor correlation between the drugs suspected on admission and those actually detected in the blood. Although the total number of admissions due to poisoning increased in 1984 (21 in 1982 vs. 37 in 1984), mechanical ventilation was required by fewer patients (92% in 1982 vs. 51% in 1984) and for a shorter period of time (3.1 days in 1982 vs. 2.1 days in 1984), which resulted in a shorter ICU stay (4.8 days in 1982 vs. 3.1 days in 1984). The introduction of the new BDZ antagonist flumazenil may have partially accounted for this positive trend.

Mode of vaginal delivery and epidural analgesia

A study was carried out on the mode of vaginal delivery in two large groups of parturients: one group comprised 11,264, of whom 0.1% were given epidural analgesia (1977-78) and the other, 10,650, of whom 50% delivered under epidural blockade (1982-83). When the incidence and reasons for instrumental intervention in these two groups were analyzed, it was found that the rate of instrumental delivery was only 1.3% higher (P less than 0.001) in the latter group, which was mainly due to factors not attributable to the epidural blockade. It may be concluded from this survey that epidural analgesia for labor and delivery does not cause an increase in the rate of instrumental delivery.

Early clinical experience in reversing benzodiazepine sedation with flumazenil after short procedures

Flumazenil (Flu) (Ro 15-1788, Anexate) is a newly synthetized specific benzodiazepine (BZD) antagonist which was recently introduced for clinical study. The drug was intravenously injected, in titrated doses, to patients undergoing diagnostic or therapeutic procedures in order to reverse the sedative effects of BZDs. A total of 63 patients undergoing hand surgery under i.v. regional block, lower abdominal surgery under epidural anesthesia, cardiac catheterization, intracardiac catheter ablation, cardioversion, gastroscopy and bronchoscopy were studied. Flu in a dose ranging from 0.1 to 0.42 mg effectively reversed BZD-induced sedation in all patients 1-2 min following i.v. injection. Patients were fully awake and oriented yet calm and in good mood. Flu was well tolerated even in the high risk cardiac patients, with no significant changes in vital signs nor any sign of local irritation at the site of Flu injection. No significant resedation was observed. Thus Flu was very useful in reversing BZD-induced sedation or unconsciousness in a variety of clinical situations.

Augmentation of bupivacaine analgesia in labor by epidural morphine

The analgesic properties and motor effect of epidural 0.25% bupivacaine (8 mL) were compared with those of epidural morphine (2 mg in 10 mL saline) followed by 8 mL of 0.25% bupivacaine. The study was performed on two groups of parturients (30 in each group) in active labor. Pain relief in the morphine-bupivacaine group lasted for a mean of 131.1 minutes (SD +/- 49.8) as opposed to the plain bupivacaine group -57 minutes (SD +/- 15.28). Satisfaction from analgesia in the morphine-bupivacaine group was higher as well. Motor involvement was not seen in either group. Perineal pain relief in the postpartum period lasted for a mean of 16 hours and 40 minutes in the morphine-bupivacaine group. It was concluded that the concomitant use of epidural morphine augmented the analgesic effect of 0.25% bupivacaine without motor effect.

Extradural analgesia in the management of singleton breech delivery

Ninety-four singleton vaginal breech deliveries conducted under extradural analgesia were compared with 277 singleton vaginal breech deliveries conducted without extradural analgesia. Mean duration of the first stage of labour was similar in both groups. Mean duration of the second stage of labour was prolonged and mean 1-min Apgar scores were less in fetuses weighing more than 2500 g in the extradural group. Mean 5-min Apgar scores, perinatal morbidity and maternal complications were similar in both groups.

Anesthetic management of 646 consecutive cesarean section cases

A retrospective analysis of 646 consecutive cesarean deliveries during a 1-year period was performed. The indications for cesarean section, techniques of anesthesia, fetal and maternal outcome, and complications were evaluated. Of 646 cesarean deliveries, 153 (23.7%) were elective and 493 (76.3%) nonelective. Regional block was the main anesthetic technique used for the elective (88.3%) and the nonelective (79.3%) operations. Maternal complications were few and reversible. In 96% of the newborns the Apgar score was greater than or equal to 7 at 5 min. These results suggest that regional block is the preferred anesthetic technique for cesarean section.

Epidural analgesia for planned vaginal delivery following previous cesarean section

The effect of lumbar epidural on the course of labor, delivery, and outcome was studied in 115 parturients with a previous cesarean section who were given a trial of vaginal delivery. One hundred three women were multiparous and 12 were grandmultiparous. Uterine contractions and fetal heart rate (FHR) were monitored continuously in all patients. Epidural block was performed using 8 mL of 0.35% bupivacaine without adrenaline. Supplemental doses were administered through an indwelling catheter. At the beginning of the second stage, 10 mL of 0.25% bupivacaine was added in the sitting position. Forty-eight women delivered spontaneously and 54 had an assisted second stage. Thirteen women delivered by a repeat low segmental cesarean section; dehiscence was observed in only one woman. Fetal outcome was satisfactory and similar to that of the authors' general parturient population.