Acute Liver Failure Following Minocycline Treatment – A Case Report and Review of the Literature

We present the case of a 23-year-old female patient with acute liver failure following intake of minocycline. This patient had severe hypereosinophilia and massively increased IgE levels. Experimental studies in this case revealed elevated IFN-γ-, as well as TNF-α-producing CD4+ and CD8+ T-cells after in vitro stimulation with minocycline, indicating a type I/IgE-mediated as well as type II/cytotoxic reaction in the pathogenesis of minocycline-induced liver failure. Although mild forms of liver involvement are well known side effects of minocycline, only 8 cases with acute liver failure have been reported, and we present a review of all cases.

Extracellular pH Controls NHE1 expression in epidermis and keratinocytes: implications for barrier repair

We have previously shown that the Na+/H+ antiporter (NHE1) is an essential endogenous pathway responsible for stratum corneum (SC) acidification. Since the epidermis must re-establish its epidermal barrier after acute barrier perturbations, we asked whether the NHE1 was, in turn, regulated by changes in barrier status. We found that in vivo epidermal NHE1 expression was upregulated within hours of barrier disruption. We next asked whether NHE1 was regulated by barrier status per se, or by the SC alkalinization that accompanies barrier perturbation. NHE1 was upregulated by alkalinizing SC pH, whereas this antiporter was downregulated by acidifying SC pH, independent of changes in barrier status. Moreover, acidifying SC pH overrode the effects of barrier break in regulating NHE1 expression, suggesting that SC alkalinization is the major stimulus for increased NHE1 expression. Finally, we confirmed that the keratinocyte NHE1 antiporter is regulated by extracellular pH independent of barrier status, by demonstrating that NHE1 was upregulated in cultured keratinocytes exposed to pH 8.3 medium and downregulated in cultured keratinocytes exposed to pH 6.3 medium. These data suggest that the keratinocyte NHE1 is regulated by extracellular pH. SC barrier break also upregulates NHE1 expression, but this response seems to be mediated by concomitant changes in SC pH.

The ENaC channel is required for normal epidermal differentiation

Ionic fluxes are important for critical aspects of keratinocyte differentiation, including synthesis of differentiation-specific proteins, enzymatic catalysis of protein cross-linking, post-transcriptional processing of profilaggrin, and lipid secretion. The epithelial sodium channel is expressed in epidermis and the expression of its alpha and beta subunits is enhanced as keratinocytes differentiate. In order to ascertain the role of the epithelial sodium channel in epidermal differentiation, we examined skin of mice in which the epithelial sodium channel alpha subunit had been deleted. Newborn -/- mice, in which the alpha subunit had been completely inactivated, demonstrated epithelial hyperplasia, abnormal nuclei, premature secretion of lipids, and abnormal keratohyaline granules. In addition, immunohistochemistry demonstrated that expression of the differentiation markers K1, K6, and involucrin were abnormal. These data suggest that the epithelial sodium channel modulates ionic signaling for specific aspects of epidermal differentiation, such as synthesis or processing of differentiation- specific proteins, and lipid secretion.

Vitamin C stimulates sphingolipid production and markers of barrier formation in submerged human keratinocyte cultures

Human keratinocytes differentiate in vitro in response to a variety of stimuli, but neither the levels nor the spectrum of ceramides approach those seen in vivo. Ceramide production increases when human keratinocytes are grown at an air-liquid interface, and alterations in ceramide content occur when vitamin C is added to air-exposed, organotypic culture systems (Ponec et al. J Invest Dermatol 109:348, 1997). Here, we assessed whether vitamin C stimulates sphingolipid production in human keratinocytes independent of differentiation and air exposure. When submerged, human keratinocytes were grown in 1.2 mM calcium and serum-containing medium with vitamin C (50 microg per ml) for 9 d, total lipid content remained unchanged, but both glucosylceramide and ceramide content increased. Moreover, selected ceramide and glucosylceramide species: i.e., nonhydroxy ceramide 2 and both alpha- and omega-hydroxylated sphingolipids, increased preferentially [ceramide 4 (6-hydroxy-acylceramide), ceramide 5 (alpha-hydroxyceramide), ceramide 6 (4-hydroxy-alpha-hydroxyceramide), and ceramide 7 (6-hydroxy-alpha-hydroxyceramide); and acylglucosylceramide, glucosylceramide-B, and glucosylceramide-D], whereas ceramide 1, ceramide 3, glucosylceramide-C, and sphingomyelin remained unchanged. Synthesis of the corresponding ceramide and glucosylceramide fractions was enhanced by vitamin C, attributable, in part, to increased ceramide synthase activity (over 2-fold, p = 0.01); both serine palmitoyltransferase and glucosylceramide synthase activities remained unaltered. Finally, increased vitamin C-stimulated sphingolipid production correlated with the presence of lamellar bodies with mature internal contents, an increase in covalently bound omega-hydroxyceramide, and the appearance of prominent, corneocyte-bound lipid envelopes, whereas cornified envelope formation was unchanged. Thus, in submerged human keratinocytes, vitamin C induces both increased sphingolipid production and enhancement of permeability barrier structural markers.

Prophylactically-administered rectal acetaminophen does not reduce postoperative opioid requirements in infants and small children undergoing elective cleft palate repair

Rectal acetaminophen (Ac) is often administered prophylactically at anesthesia induction for postoperative pain management in small children and is thought to have an opioid-sparing effect. We assessed in this double-blinded, prospective, randomized study early opioid requirements after three doses of Ac (10, 20, and 40 mg/kg versus placebo) in 80 children (ASA physical status I, age 11.4 +/- 9.9 mo) undergoing cleft palate repair. Single Ac plasma concentrations were measured. Pain scores assessed in the postanesthesia care unit of > or = 4 of 10 resulted in the IV administration of 25 microg/kg piritramide, a popular European mu receptor agonist (lockout time, 10 min; maximum 0.125 mg/kg). There were no significant differences between groups with regard to the early postoperative pain scores and the overall cumulative IV opioid requirements. Maximal plasma concentrations achieved were only subtherapeutic (Ac 10 mg/kg: 8 microg/mL; Ac 20 mg/kg: 13 microg/mL; Ac 40 mg/kg: 21 microg/mL after 122, 122, and 121 min, respectively). We conclude that rectal Ac up to 40 mg/kg has no opioid-sparing effect, does not result in analgesic Ac plasma concentrations, and lacks proof of its efficacy in infants and small children undergoing cleft palate repair, whereas titrated IV opioid boluses produced rapid and reliable pain relief.

IMPLICATIONS

Acetaminophen is widely used prophylactically for postoperative analgesia in children and is thought to have an opioid-sparing effect. We showed that rectal acetaminophen up to 40 mg/kg administered at anesthesia induction lacked proof of efficacy, whereas IV opioid boluses resulted in reliable pain relief in children undergoing cleft palate repair.

[Postoperative pain therapy in pediatrics. Results of a representative survey in Germany]

The last survey addressing postoperative pain management in Germany was published in 1987, special data concerning postoperative pain management in pediatric patients had not been presented previously. The goal of this survey is to present the standard of postoperative pain management in pediatric patients in Germany. A detailed questionnaire was mailed to all German anaesthesia departments and interdisciplinary intensive care units (n = 1,500) to determine the current management of postoperative pain management in pediatric patients. After eight weeks, 42.6% of the survey had been returned. Rectally administered acetaminophen is the standard drug regimen for postoperative analgesia in children. Compared to previous surveys, the use of opioids has increased in popularity. The routine use of non-steroid antiinflammatory drugs (NSAIDs) and spasmolytics as well as the application of regional anaesthesia techniques is uncommon in pediatric postoperative pain management. Compared to other European countries, patient- or parent-controlled analgesia is more popular in Germany. Despite modern concepts of organization and a great variety of drugs available today, 71.1% of the responding anesthesiologists in this survey still believe that pediatric postoperative pain management needs to be improved.

Pharmacodynamics and tolerability of acetyl starch as a new plasma volume expander in patients undergoing elective surgery

OBJECTIVE

Acetyl starch (ACS) is a new synthetic colloid solution for plasma volume expansion and is now undergoing phase II clinical trials. We compared the pharmacodynamics and tolerability of ACS with those ofhydroxyethyl starch (HES) in 32 patients (American Society of Anesthesiologists physical status I and II) undergoing elective surgery.

SUBJECTS, MATERIAL AND METHODS

In this prospective, randomized, double-blind trial patients received either 15 ml/kg ACS 6% (average molecular weight (Mw) 200,000/molar substitution (MS) 0.5) or HES 6% (Mw 200,000/MS 0.5) i.v. up to a maximum dose of 1000 ml. Hemodynamic parameters, rheologic parameters, volume effect, acid-base status as well as effects on hemostasis were studied.

RESULTS

After infusion of ACS and HES there was a similar increase in central venous pressure and mean arterial pressure in both groups. Acid-base status was not significantly altered after the end of the colloid infusions. After ACS infusion, plasma acetate concentration increased from 0.13+/-0.16 mg/dl to 2.87+/-1.13 mg/dl, however, after 24 h there was no significant difference in plasma acetate concentration compared to HES. The volume effect ranged from 104-116%(ACS) and from 88-118% (HES) of the colloid dose administered. These differences were not statistically significant. Partial thromboplastin time (aPTT) was only slightly increased after ACS infusion (from 38.6+/-5.7 sec to 41.4+/-5.1 sec), but was significantly increased after HES infusion (from 38.7+/-5.7 sec to 46.1+/-7.0 sec).

CONCLUSION

ACS and HES are equally effective plasma volume expanders; ACS might be a new, alternative colloid solution with fewer coagulation side-effects than HES.

[The use of lithium hydroxide for carbon dioxide absorption prevents formation of compound A during sevoflurane anesthesia]

Aim of the study was the clinical investigation of sevoflurane degradation when using water-free lithiumhydroxide versus moist Drägersorb 800 for carbon dioxide absorption.

METHODS

Concentrations of Compound A in the inspiratory gas mix and serum fluoride levels were measured in two groups of 8 patients each.

RESULTS

When water-free lithiumhydroxide was used for carbon dioxide absorption, concentration of Compound A in the inspiratory gas mix was ca. 1 ppm (near minimal level of detection) as compared to ca. 20 ppm for moist Drägersorb 800. The concentration of fluoride increased during sevoflurane anesthesia (15.0 +/- 4.8 mumol/l with lithiumhydroxide versus 21.9 +/- 4.0 mumol/l with Drägersorb 800 after 60 mins).

CONCLUSIONS

When lithiumhydroxide is used, there is only minimal formation of compound A from sevoflurane degradation. Since serum fluoride levels increased in both patient groups, we conclude that this is caused mainly by metabolism of sevoflurane. Capacity of lithiumhydroxide for carbon dioxide absorption is similar to that of Drägersorb 800. Therefore, the use of lithiumhydroxide increases patient safety.

Omega-hydroxyceramides are required for corneocyte lipid envelope (CLE) formation and normal epidermal permeability barrier function

Omega-hydroxyceramides (omega-OHCer) are the predominant lipid species of the corneocyte lipid envelope in the epidermis. Moreover, their omega-esterified-derivatives (acylCer) are major components of the stratum corneum extracellular lamellae, which regulate cutaneous permeability barrier function. Because epidermal omega-OHCer appear to be generated by a cytochrome P450-dependent process, we determined the effects of a mechanism-based inhibitor of omega-hydroxylation, aminobenzotriazole (ABT), on epidermal omega-OH Cer formation and barrier function. We first ascertained that ABT, but not hydroxybenzotriazole (OHBT), a chemical relative with no P450 inhibitory activity, inhibited the incorporation of [14C]-acetate into the omega-OH-containing Cer species in cultured human keratinocytes (68.1% +/- 6.9% inhibition versus vehicle-treated controls; p < 0.001), without altering the synthesis of other Cer and fatty acid species. In addition, ABT significantly inhibited the omega-hydroxylation of very long-chain fatty acids in cultured human keratinocytes. Topical application of ABT, but not OHBT, when applied to the skin of hairless mice following acute barrier disruption by tape-stripping, resulted in a significant delay in barrier recovery (e.g., 38.3% delay at 6 h versus vehicle-treated animals), assessed as increased transepidermal water loss. The ABT-induced barrier abnormality was associated with: (i) a significant decrease in the quantities of omega-OHCer in both the unbound and the covalently bound Cer pools; (ii) marked alterations of lamellar body structure and contents; and (iii) abnormal stratum corneum extracellular lamellar membrane structures, with no signs of cellular toxicity. Furthermore, pyridine-extraction of ABT- versus vehicle-treated skin, which removes all of the extracellular lamellae, leaving the covalently attached lipids, showed numerous foci with absent corneocyte lipid envelope in ABT- versus vehicle-treated stratum corneum. These results provide the first direct evidence for the importance of omega-OHCer for epidermal permeability function, and suggest further that acylCer and/or corneocyte lipid envelope are required elements in permeability barrier homeostasis.

[Ketoacidosis in a 14 month old child caused by fasting]

Preoperative starvation in order to prevent pulmonary aspiration is mandatory in elective pediatric surgery. Hypoglycemia, thirst and unwellness have been reported as undesired side effects. The metabolic response towards decreasing blood-glucose concentrations in fasting children includes gluconeogenesis and production of ketone bodies to meet the energetic demand. Accumulation of beta-hydroxybutyrate und acetoacetate in blood can lead to ketoacidosis. We report a case of a severe intraoperative ketoacidosis in a fourteen months old child complicating 36 hours of starvation.

[Infection or SIRS--the problem of definition]

Despite the knowledge about sepsis for many years, the definition of sepsis is contested more than ever since the early 90th. Therefore, the comparability of many clinical investigations and scientific work in the past is still impaired. To define the entrance criteria for further clinical studies, in 1991 a consensus conference was held in the USA, but its recommendations have not found unequivocal acceptance. Therefore, these recommendations are presented and their meaning will be discussed.

Recovery and pharmacokinetic parameters of desflurane, sevoflurane, and isoflurane in patients undergoing urologic procedures

STUDY OBJECTIVE

To compare the pharmacokinetics and the speed of recovery after inhalation anesthesia with desflurane, sevoflurane, and isoflurane in elective surgery.

DESIGN

Prospective, randomized study.

SETTING

University medical center.

PATIENTS

30 ASA physical status I and II adults presenting for elective surgery.

INTERVENTIONS

Anesthesia was induced with etomidate and maintained with desflurane (n = 10), sevoflurane (n = 10), or isoflurane (n = 10) and nitrous oxide. The inhalation drugs were titrated until an adequate clinical depth of anesthesia was reached. At the end of anesthesia, the patients breathed oxygen via the endotracheal tube and after extubation via a face mask.

MEASUREMENTS AND MAIN RESULTS

The groups were similar with respect to age, weight, duration of anesthesia, and mean arterial pressure. Mean end-tidal concentration (FA = FA0) at the end of anesthesia was 6.34 +/- 1.15% after desflurane, 1.85 +/- 0.42% after sevoflurane, and 1.10 +/- 0.24% after isoflurane. FA/FA0 decreased significantly faster with desflurane than with isoflurane, while there was little difference between desflurane and sevoflurane. As for the terminal half-life (t1/2), there were no differences among the groups (8.16 +/- 3.15 min after desflurane, 9.47 +/- 4.46 min after sevoflurane, and 10.0 +/- 5.57 min after isoflurane). The time until a command was followed for the first time was the same in all three groups (13.0 +/- 4.7 min after desflurane, 13.4 +/- 4.4 min after sevoflurane, and 13.6 +/- 3.4 min after isoflurane). There was no significant correlation between duration of anesthesia and the time until recovery.

CONCLUSIONS

There are only minor differences with regard to the recovery phase in premedicated patients who receive clinically titrated inhalation anesthesia with desflurane, sevoflurane, or isoflurane.

Carbon dioxide absorption: toxicity from sevoflurane and desflurane

The degradation of volatile anaesthetics by desiccated carbon dioxide absorbents can result in adverse outcomes. Desiccated carbon dioxide absorbent reacting with desflurane can cause potentially life-threatening intraoperative carbon monoxide exposure; the reaction with sevoflurane can cause the formation of several toxic breakdown products, e.g. compound A. Compound A-related renal toxicity in humans is still a matter of controversy.

[Inhalation of nitric oxide in severe lung failure]

Despite intensive therapeutic efforts, adult respiratory distress syndrome (ARDS) is still associated with a lethality ranging from 50 to 80%. Besides hypoxemia, fatal outcome is caused by myocardial insufficiency due to a progressive decrease in pulmonary vascular conductance. Inhalation of NO can selectively dilate pulmonary vessels in ventilated lung regions, thus increasing mean pulmonary artery conductance and decreasing venous admixture. This study determines the effects of NO inhalation in patients with severe ARDS on pulmonary gas exchange, haemodynamics and mortality. Twenty surgical patients (mean age 50.3 +/- 9.25 years) with severe ARDS (Murray score 3.4 +/- 0.3) were treated with variable concentrations of NO during mechanical ventilation with continuous positive pressure. Pulmonary artery catheters were used to measure pressures, flow and venous admixture. Mortality with NO inhalation was compared with that of previous ARDS patients (n = 20) who had not received NO. Mean duration of NO inhalation was 120.1 +/- 33.12 hours (n = 20) (range 40 to 254 hours). Mean NO concentration during the first hour of delivery was 18.5 +/- 3.88 ppm. Sixteen patients had FiO2 of 1.0 when NO was started. Within the first hour of NO inhalation, the PaO2/FiO2 ratio increased from 82.1 +/- 10.28 to 124.6 +/- 28.18. Eighteen patients were responders. Mean ventilatory pressure was lowered. Oxygenation improvement was most marked during the first 36 hours and then gradually declined. Despite the significant increase in NO related oxygenation, pulmonary artery pressures did not consistently decrease. Sixteen patients in the NO group died. In the group without NO 15 patients died. Compared with ARDS patients of similar severity not receiving NO, the NO-treated patients had the same lethality. In severe ARDS, oxygenation significantly improves with the initiation of NO inhalation, but this effect declines over time. With NO, FiO2 and ventilatory pressures can be lowered. Whether the theoretically reduced oxygen toxicity and the reduced invasiveness of mechanical ventilation with NO reduces patient mortality must be determined in larger patient groups.

[Exposure of recovery room personnel to inhalation anesthetics]

Both desflurane and sevoflurane have a favourable blood/gas distribution coefficient. There is concern, however, that environmental contamination is higher when these agents are employed since they must be used in relatively high concentrations. Our study seeks to determine the degree of exposure of recovery room staff to trace amounts of these two agents. Two hundred and seven surgical patients were included in the study. The recovery room studied had a volume of 243 cubic metres. The hourly fresh air supply for this room was 1,845 cubic metres, which results in 7.6 air exchanges per hour without air return. Measurements of trace concentrations of the inhalational agents were taken for 12 days. Concentrations of these anaesthetics were assessed in the recovery room with a real-time infrared spectrometer every 90 seconds. Mean exposure to nitrous oxide in the recovery room was 11.5 +/- 3.97 ppm and to isoflurane 1.4 +/- 0.31 ppm. All measured values were below the standard German threshold values. Trace concentrations of desflurane were 2.8 +/- 0.84 ppm and of sevoflurane 3.2 +/- 0.62 ppm. We conclude that the exposure to the inhalational anaesthetics in the climatised recovery room was low. The threshold values of 100 ppm for nitrous oxide and 10 ppm for isoflurane recommended by German law were not exceeded. When the new volatile anaesthetics are used, exposure of recovery room staff to trace concentrations of these agents is higher, but the concentrations do not exceed the levels allowed applicable German health regulations.

Clinical pharmacokinetics of sevoflurane

Sevoflurane is a comparatively recent addition to the range of inhalational anaesthetics which has been recently released for clinical use. In comparison to older inhalational agents such as isoflurane or halothane, the most important property of sevoflurane is its low solubility in the blood. This results in a more rapid uptake and induction than the 'older' inhalational agents, improved control of depth of anaesthesia and faster elimination and recovery. The more rapid pharmacokinetics are a result of the low blood/gas partition coefficient of 0.69. With an oil/gas partition coefficient of 47.2, the minimum alveolar concentration (MAC) of sevoflurane is 2.05%. Two to 5% of the drug taken up is metabolised by the liver. The pharmacokinetics of sevoflurane do not change in children, obese patients or patients with renal insufficiency. The pharmacokinetics and pleasant odour of sevoflurane make mask induction feasible, which is an obvious advantage in paediatric anaesthesia. The hepatic metabolism of sevoflurane results in the formation of inorganic fluoride. Upon contact with alkaline CO2 absorbent, a small amount of sevoflurane is degraded and a metabolite (compound A) is formed and inhaled in trace amounts. Whether inorganic fluoride or compound A are nephrotoxic is presently a matter of controversy.

Thoracoscopic microsurgical technique for vertebral surgery--anesthetic considerations

BACKGROUND

The thoracoscopic microsurgical technique (TMT) for vertebral and spinal cord surgery is associated with the benefits of reduced postoperative pain, accelerated return to physical activity and reduced complication rates. However, because of the surgeon's requirement of a non-ventilated lung, it confronts the anesthesiologist with the need for extremely long duration of single-lung ventilation (SLV).

METHODS

We describe our experiences with 82 patients, whom we anesthetised from 1993 until 1996 for TMT. Because of the potential risk of depression of hypoxic pulmonary vasoconstriction during SLV by volatile anesthetics, we primarily used a total intravenous technique (55 patients). With more experience, we also used a combination of volatile and intravenous anesthetics (16 patients) and, finally, volatile anesthetics only (11 patients). Data from patients anesthetised for TMT were compared with data from 22 patients operated with open thoracotomy from 1984 until 1992.

RESULTS

While the operating time (290.1 +/- 133.2 min for TMT vs. 312.3 +/- 113.6 for thoracotomy) and the anesthesia time (431.2 +/- 140.3 for TMT vs. 416.4 +/- 102.1 for thoracotomy) showed no significant differences, the TMT required an extremely long time of SLV (270.2 +/- 133.2 min) to gain access to the spine using left-sided double-lumen tubes. While the oxygenation index (PaO2/FiO2), as a marker for pulmonary oxygenation capacity, decreased significantly after initiation of SLV for TMT, it was markedly enhanced with increasing duration (270.2 +/- 133.2 min) of SLV. Oxygenation index showed no significant difference when comparing the different anesthetic techniques for TMT.

CONCLUSION

We conclude that despite the long duration of SLV, TMT is a reasonable alternative to open thoracotomy for thoracic neurosurgical spine procedures because of the substantial clinical benefits of accelerated return to physical activity, reduced complication rates and reduced intensive care unit and hospital stay.

[Uptake and distribution of sevoflurane]

Sevoflurane is characterized by a low blood/gas partition coefficient of 0.69, only desflurane and nitrous oxide have lower blood/gas solubilities. Alveolar equilibration is fast, a feature useful for rapid induction of anesthesia. Because of its pleasant smell, mask induction is feasible and routinely used in clinical settings. Formation of inorganic fluoride by metabolism and by compound A by degradation in CO2-absorbent has not yet been shown to be nephrotoxic in humans. Pulmonal elimination of sevoflurane is rapid because of its low blood solubility. Clinical results showed that rapidity of recovery from sevoflurane anesthesia is equal to that of desflurane anesthesia. Physicochemical properties of sevoflurane allow its application in conventional vaporizers.

The pharmacokinetics of acetyl starch as a plasma volume expander in patients undergoing elective surgery

Acetyl starch (ACS) is a new synthetic colloid solution for plasma volume expansion and is now undergoing phase 2 clinical trials. We compared the pharmacokinetics of ACS with those of hydroxyethyl starch (HES) in 32 patients (ASA physical status I and II) undergoing elective surgery. In this randomized, double-blind trial, patients received either 15 mL/kg ACS 6% (average molecular weight [Mw] 200,000/molar substitution [MS] 0.5) or HES 6% (Mw 200,000/MS 0.5) i.v. up to a maximal dose of 1000 mL. Plasma colloid concentrations were measured by repetitive arterial blood sampling over 24.5 h. Plasma colloid concentrations were detected using a high-pressure liquid chromatography controlled enzymatic test. Standard pharmacokinetics were calculated, including initial half-life (t(1/2init)), i.e., the time required for a 50% decline of the maximal plasma colloid concentration at the end of drug infusion. Whereas HES was eliminated by second-order kinetics, ACS followed first-order characteristics. In the first hours after i.v. administration, t(1/2init) and clearances were similar in both groups. However, the terminal half-life of HES was significantly longer than that of ACS (9.29 +/- 1.43 h vs 4.37 +/- 1.06 h). After 16.5 and 24.5 h, ACS showed significantly lower plasma concentrations than HES, which indicates that the final degradation of ACS by esterases and amylase was significantly more rapid. ACS might be an alternative plasma volume expander, which avoids the accumulation of persisting macromolecules.

IMPLICATIONS

We studied the pharmacokinetics of acetyl starch, a newly developed colloid solution for plasma volume substitution, compared with hydroxyethyl starch in 32 surgical patients undergoing elective major general surgical procedures. In contrast to hydroxyethyl starch, this new agent undergoes rapid and nearly complete enzymatic degradation.

Barrier recovery is impeded at neutral pH, independent of ionic effects: implications for extracellular lipid processing

Epidermal permeability barrier homeostasis requires the postsecretory processing of polar lipid precursors into nonpolar lipid products within the stratum corneum (SC) interstices by a family of lipid hydrolases. A specific requirement for beta-glucocerebrosidase (beta-GlcCer'ase), which exhibits a distinct acidic pH optimum, is particularly well documented. Therefore, we sought to determine whether the recovery of the barrier after acute insults requires acidification of the SC. We examined permeability barrier recovery by assessing changes in transepidermal water loss (TEWL), SC membrane ultrastructure utilizing ruthenium tetroxide (RuO4) postfixation, and beta-GlcCer'ase activity by in situ zymography at an acidic vs neutral pH. Barrier recovery proceeded normally when acetone-treated skin was exposed to solutions buffered to an acidic pH. In contrast, the initiation of barrier recovery was slowed when treated skin was exposed to neutral or alkaline pH, regardless of buffer composition. In addition, enhancement of the alkaline buffer-induced delay in barrier recovery occurred with Ca2+ and K+ inclusion in the buffer. Moreover, the pH-dependent alteration in barrier recovery appeared to occur through a mechanism that was independent of Ca(2+)- or K(+)-controlled lamellar body secretion, since both the formation and secretion of lamellar bodies proceeded comparably at pH 5.5 and pH 7.4. In contrast, exposure to pH 7.4 (but not pH 5.5) resulted in both the persistence of immature, extracellular lamellar membrane structures, and a marked decrease in the in situ activity of beta-GlcCer'ase. These results suggest first that an acidic extracellular pH is necessary for the initiation of barrier recovery, and second that the delay in barrier recovery is a consequence of inhibition of postsecretory lipid processing.

[Safety aspects of bronchoalveolar lavage in risk patients in childhood--continuous end-expiratory pCO2 monitoring]

Although bronchoalveolar lavage (BAL) is a useful tool even in childhood pulmonary diseases, only little is known about the problems attendant to its use. Hence, we investigated from a total of 212 rigid bronchoscopy procedures 22 patients of 1-10 years of age. General inhalation anaesthesia was performed and BAL was carried out using a paediatric standardised protocol. BAL volume was adjusted to body weight. Before BAL and 2, 7 and 20 minutes after BAL capillary blood gas, blood pressure, heart rate and SaO2 were measured. Continuously end-tidal PCO2 (ET (PCO2) measurement was done by using a catheter placed in the main stream bronchus. Mean ET PCO2 increased from 39.6 +/- 9.5 mmHg to 45.7 +/- 6.87 mmHg. Concomitantly mean capillary PCO2 increased from 46.68 +/- 10.7 mmHg to 50.1 +/- 10.47 mmHg. Correlation of ET PCO2 compared to cap PCO2 was good (r = 0.89). One patient showed desaturation up to 72% another patient hypercapnia up to 77 mmHg. We conclude that generally speaking BAL is a safe procedure, even in high-risk patients. Complications are minor and of little consequence to the patient. However, severe unforeseen events may occur. Therefore, bronchoscopy and bronchoalveolar lavage should not be performed without availability of an intensive-care unit.

[Diagnosis of pneumonia in long-term ventilated patients. Value of digital luminescence radiography in comparison with clinical and microbiological monitoring]

PURPOSE

Pulmonary infection is one of the most feared complications in patients receiving long-term ventilation. We evaluated prospectively the diagnostic value of daily bedside chest radiography performed as digital luminescence radiography (DLR) in comparison to clinical findings and quantitative microbial culture.

MATERIAL AND METHODS

Prospective evaluation of daily bedside chest radiography (DLR) and clinical parameters such as blood count, body temperature, and microbiological monitoring (quantitative culturing, microscopy) of 20 patients receiving long-term ventilation was undertaken. Altogether 325 chest radiographs were evaluated.

RESULTS

96% of the routine radiographs showed abnormal findings. Nosocomial pneumonia was suspected in 31% of all 330 days of observation by means of clinical and microbiological findings. DLR showed correct findings in 80% of this days (right-positive interpretation); a false-positive interpretation was resulted in 16 radiographs. Most common finding in nosocomial pneumonia was an alveolar pattern with air bronchogram. Fever and leucocytosis often precede radiological evidence of pneumonia.

CONCLUSION

Daily bedside chest radiography performed as DLR shows abnormal finding in a high percentage. Bedside chest radiograph is in accordance to clinical and microbiological finding of nosocomial pneumonia in 80%.

Role of quantitative cultures and microscopic examinations of endotracheal aspirates in the diagnosis of pulmonary infections in ventilated patients

Endotracheal aspirates (EA) from 20 intubated patients in a surgical intensive care unit (mean ventilation time/patient = 16.5 days) were investigated serially by performing quantitative cultures using growth of 10(5) cfu/mL as a cut-off point. Microscopic examinations were made using Giemsa's stain for polymorphonuclear neutrophils (PMN). The spectrum of pathogens encountered was determined and compared with clinical data to distinguish colonization from infection of the lower respiratory tract. Out of 301 EA cultures, 156 (51.8%) were positive and 145 (48.2%) were below the cut-off point. Counts of PMN were significantly higher in samples which gave positive cultures. Seventy-five different bacterial strains were isolated (64% were Gram-negative bacilli). Seventeen patients (85%) were colonized with Gram-negative bacteria. Nine patients (45%) developed nosocomial pneumonia (NP), five (25%) had no signs of pneumonia, and six (30%) had an uncertain status. Main causative agents for NP were Pseudomonas aeruginosa, Enterobacteriaceae and Staphylococcus aureus. Quantitative EA cultures had a sensitivity of 81.5%, a specificity of 64.8%, a positive predictive value of 55% and a negative predictive value of 87%. Our results suggest that EA quantitative cultures (cut-off value 10(5) cfu/mL), species identification and microscopic examination of EA may help to differentiate tracheobronchial colonization and infection, especially when bronchoscopic techniques are not available.

[Principles of analgesia and sedation]

This lecture outlines the current pharmacological concepts of sedation and analgesia in the critically ill patient requiring intensive care therapy. The primary goal is to sedate such patients so that they tolerate mechanical ventilation, as well as the therapeutic and diagnostic procedures that are routinely performed on an intensive care ward. The pharmacological regimen comprises both anxiolytic and analgesic drugs. So far, no drug combination has been identified as the ideal therapy; the standard deviation of successful analgosedation is large due to an unpredictable individual response. Because the drugs currently used are free of toxic side effects, the selection made is mainly determined by factors relating to pharmacokinetic criteria, such as short half-life of action or a predictable time of elimination. So far, the selection or combination of certain drugs has not been found to influence the patient's outcome in severe disease states such as sepsis, multiple trauma, or neurotrauma. "Good quality" of sedation and analgesia is still judged by its ability to suppress tachycardia, hypertension, hyperventilation or respiratory efforts against mechanical ventilation and the absence of increases in intracranial pressure during therapeutic manoeuvres.

[Prevention of myocardial ischemia. Study following aortocoronary bypass operation with the calcium antagonist diltiazem]

The incidence of postoperative myocardial infarction (MI) is proportional to the incidence of myocardial ischaemic episodes. Therefore, the prevention of such episodes is of great clinical importance. METHODS. In 90 patients undergoing coronary artery bypass grafting (CABG), perioperative i.v. treatment with either nitroglycerin (NTG), diltiazem (DIL), or the combination of DIL/NTG was used until arrival in the intensive care unit. Myocardial ischaemic episodes were monitored with an automatic ECG-ST-trend analyser (Marquette 7010). RESULTS. Significantly less ischaemic episodes were seen in the DIL group (6.7%) compared to the NTG group (13.2%) or DIL/NTG group (13.5%). Furthermore, significantly less ischaemic episodes were associated with relevant haemodynamic alterations in the DIL group (58.1%) compared to the NTG (89.1%) or DIL/NTG group (80.0%). Increases in heart rate were markedly reduced in the DIL group. DISCUSSION. DIL results in marked haemodynamic stabilisation during CABG, especially in the period immediately after extra-corporeal circulation. This might serve as an explanation for the significant reduction in ischaemic episodes in the DIL group compared to the other two groups. Therefore, perioperative prevention of myocardial ischaemia with the calcium antagonist DIL seems to be favourable in patients during CABG.

Role of pericardial constraint for right ventricular function in humans

STUDY OBJECTIVE

To analyze the extent of pericardial constraint on right ventricular function in humans.

PATIENTS AND METHODS

Twenty patients, 59 +/- 2 (mean +/- SEM) years old, undergoing coronary bypass surgery. Right ventricular volumes and pressures were evaluated using a rapid response Swan-Ganz thermodilution catheter.

INTERVENTIONS

Parameters were determined before and after pericardiotomy, both before and during increased right ventricular systolic pressure by partial compression of the pulmonary artery (before pulmonary compression: 25 +/- 1 mm Hg; during: 39 +/- 1 mm Hg).

RESULTS

Pericardiotomy alone did not significantly affect right ventricular end-diastolic volume (before: 79 +/- 4 mL m-2; after: 78 +/- 3 mL m-2), right ventricular ejection fraction (before: 48 +/- 1%; after: 48 +/- 2%), and right atrial pressure (before: 4.3 +/- 0.8 mm Hg; after: 4.3 +/- 0.7 mm Hg). Before pericardiotomy, the increase in right ventricular afterload significantly increased right atrial pressure (to 5.5 +/- 0.7 mm Hg, p < 0.05) and reduced right ventricular ejection fraction (to 43 +/- 2%, p < 0.01). Right ventricular end-diastolic volume remained unchanged. After pericardiotomy, the increase in right ventricular afterload significantly increased right ventricular end-diastolic volume (to 85 +/- 3 mL m-2, p < 0.01) and also reduced right ventricular ejection fraction (to 42 +/- 2%, p < 0.01), while right atrial pressure was not significantly changed. During increased right ventricular afterload, the right ventricular diastolic pressure-volume relation was shifted rightward.

CONCLUSIONS

At normal levels of right ventricular diastolic filling, the pericardium does not exert constraining effects on right ventricular function. However, with increasing levels of right ventricular preload, pericardial constraint significantly influences right ventricular function in humans.

Midazolam does not antagonize fentanyl-mediated analgesia in surgical patients

STUDY OBJECTIVE

To determine whether midazolam possesses a clinically significant antianalgesic action in surgical patients.

DESIGN

Randomized, controlled study.

SETTING

Inpatient anesthesia at a university department of neurosurgery.

PATIENTS

2 groups of 10 patients each who were scheduled for supratentorial brain surgery, did not have elevated intracranial pressure, and were free from systemic disease.

INTERVENTIONS

Patients underwent anesthesia induction with hexobarbital, succinylcholine, and pancuronium; anesthesia was maintained with injections of droperidol-fentanyl (Group 1) or with midazolam-fentanyl (Group 2) following a predetermined repetitive dosing schedule, such that fentanyl 0.1 mg was injected upon predominant increases in heart rate, whereas droperidol 2.5 mg or midazolam 2.5 mg was injected upon increases in blood pressure.

MEASUREMENTS AND MAIN RESULTS

Duration of anesthesia and invasiveness of surgery were similar in both groups. The amount of fentanyl required was 0.55 +/- 0.18 mg/hr (mean +/- SD) in Group 1 and 0.53 +/- 0.17 mg/hr in Group 2. Injections of droperidol 7.5 +/- 3.4 mg/hr (Group 1) and midazolam 5.9 +/- 2.3 mg/hr (Group 2) were administered intraoperatively. This redosing regimen was associated with uninterrupted hemodynamic stability, indicating comparable and adequate anesthetic depth. Plasma concentrations of metabolites and hormones indicative of humoral stress activation did not differ between groups.

CONCLUSION

Under these clinical conditions, the administration of midazolam, when compared with droperidol, was not associated with signs of any antagonistic or antianalgesic action toward fentanyl-mediated analgesia.

Droperidol causes a dose-dependent prolongation of the QT interval

To further investigate possible prolongation of the frequency-corrected QT interval (QTc interval) after administration of droperidol (DRO), we studied 40 surgical patients who were randomly assigned to one of three groups, receiving an intravenous (IV) injection of either 0.1 mg/kg (Group 1, n = 10), 0.175 mg/kg (Group 2, n = 10), or 0.25 mg/kg (Group 3, n = 20) of DRO at induction of anesthesia. The QTc interval, heart rate, and arterial pressure were registered before and 1, 2, 3, 4, 5, 7.5, and 10 min after the respective dose injection. Significant prolongations of the median QTc interval were found in patients from all groups, ranging from 37 ms (8.0%) in Group 1, to 44 ms (10.6%) in Group 2, to 59 ms (14.9%) in Group 3, when compared with control. The heart rate showed a significant increase in all groups. Mean arterial pressure (MAP) was slightly but significantly decreased in Groups 1 and 3. Prolongation of the QTc interval is a predictable and dose-dependent side effect after injection of high-dose DRO.

[Effectiveness of preventing hypotension with H1/H2 antagonists before protamine administration]

BACKGROUND

This prospective randomized study was undertaken to evaluate the effects of prophylactic administration of H1/H2 receptor blockers on histamine release and hemodynamic changes after administration of protamine in two groups of patients (n = 20) undergoing elective coronary artery bypass graft surgery.

PATIENTS AND METHODS

Group 1 (n = 10) patients were pretreated intravenously with 1 mg/kg ranitidine and 0.1 mg/kg dimetinden 15 min before termination of the extracorporeal circulation; group 2 patients (n = 10) received no medication. After termination of the extracorporeal circulation, heparin was neutralized by administration of 350 U/kg protamine, injected during 4 min via a peripheral vein. Hemodynamic measurements were carried out before the administration of protamine and at 1-min intervals up to 10 min after the injection. Before administration of protamine and 2, 4, 6, 8, and 10 min thereafter, plasma histamine levels were measured using central venous blood samples.

RESULTS

In group 1 patients, who were treated prophylactically with H1/H2 receptor blockers, the plasma histamine concentration was 0.21 +/- 0.15 ng/ml (mean +/- SD) and reached a peak value of 0.30 +/- 0.17 ng/ml within 4 min. In group 2 patients, the plasma histamine concentration increased from 0.17 +/- 0.15 to 0.26 +/- 0.24 ng/ml after 10 min. The hemodynamic reactions were comparable in both groups (group 1: decrease in systolic arterial pressure from 118 +/- 16 to 104 +/- 15 mm Hg; group 2: from 111 +/- 19 to 108 +/- 21 mm Hg; differences statistically not significant). The Spearman rank correlation revealed no statistically significant relationship between the slight plasma histamine release and clinically severe decreases of blood pressure that were observed in single patients.

CONCLUSION

Histamine release appears unlikely as the mechanism of protamine-induced hypotension. Therefore, general prophylaxis using H1/H2 receptor antagonists does not seem to be justified and cannot be recommended.

Prolongation of the QT-interval during induction of anesthesia in patients with coronary artery disease

During induction of anesthesia in 60 patients undergoing coronary artery bypass grafting (CABG), we measured the QT-interval (QTI) in the ECG, heart rate (HR) and mean arterial pressure (MAP). Based on the HR, we corrected the QT-interval (QTcI). Prior to induction, six patients (10%) already had abnormal prolongation of QTcI (> or = 440 ms). After injection of fentanyl and vecuronium, the QTcI increased significantly (P < 0.01); to a far lesser extent after injection of hypnotics (i.e. etomidate, midazolam or propofol). Orotracheal intubation caused significant shortening of QTcI (P < 0.01). HR decreased markedly after injection of fentanyl. MAP decreased, however, only after injection of hypnotics. In the immediate post intubation period, HR and MAP increased significantly. The various hypnotics produced no significant difference in HR and QTcI at any measurement point. MAP changed only after injection of hypnotics. The decrease of HR and MAP during induction of anesthesia is thought to result from a corresponding reduction of adrenosympathetic stimulation. We believe that QTcI is similarly influenced.

Respiratory effects and tolerability of Mr 2264 Cl. A new opiate partial agonist in comparison with morphine and placebo

In this double-blind, randomised, placebo-controlled cross-over study the respiratory effects of M(r) 2264 Cl 2 x 5 mg i.v., a new partial opiate receptor agonist, were investigated and compared with the respiratory effects of morphine 2 x 10 mg i.v. and placebo. As primary end-points, the slope of the rebreathing curve (dV'/dPCO2ET) and V55 (ventilation at PCO2ET = 55 mm Hg) were determined by Read's rebreathing method. The incidence of adverse events was also documented and compared. The respiratory depression after the intravenous administration of 5 mg and 10 mg M(r) 2264 Cl was comparable to the decreased sensitivity of the respiratory centre after the 20 mg morphine i.v. In contrast to morphine, a ceiling effect of M(r) 2264 Cl was found. The tolerability of M(r) 2264 Cl was comparable to that of morphine.

[Comparative study of blood and infusion heaters at various flow-through rates]

BACKGROUND

Transfusions of refrigerator-temperature blood, particularly when given very quickly, may induce severe hypothermia. In Germany, blood warmers used to avoid this danger mainly operate with dry heat.

MATERIAL AND METHODS

In the current study we compared the Fenwal BW-5 (Travenol), the Biotest BW 385 and BW 385L (Biegler) and the DW 1220 (American Pharmaseal) at different flow rates of packed cells and Ringer Lactate solution, respectively.

RESULTS

Up to flow rates of about 30 ml/min higher transfusion temperatures were reached by the Biotest BW 385L than by other warmers. Above flow rates of about 60 up to about 100 ml/min only the Fenwal BW-5 reached a transfusion temperature higher than 30 degrees C.

CONCLUSIONS

For routine transfusions and infusions the Biotest BW 385L is the most suitable warmer. If a massive transfusion is necessary, it is recommendable to use two or three Fenwal BW-5 or to apply other technologies.

[ST segment changes in the ECG. Anesthesia induction with propofol, etomidate or midazolam in patients with coronary heart disease]

Induction of anaesthesia with propofol and fentanyl can lead to marked reductions in mean arterial pressure (MAP) and heart rate (HR). Thus, the application of propofol in patients with severely reduced coronary artery perfusion is controversial. METHODS. The study group consisted of 60 patients undergoing coronary artery bypass grafting (CABG). Anaesthesia was induced over 30 s with propofol (P 1.5 mg/kg), etomidate (E 0.3 mg/kg), or midazolam (M 0.15 mg/kg) following a bolus dose of fentanyl (5 micrograms/kg). Vecuronium was used as a muscle relaxant. During induction we continuously measured MAP and HR and recorded the occurrence of myocardial ischaemia using an automatic ST-segment analyser (Marquette 7010). ST-segment deviations of more than 1 mm in leads II and V5 were interpreted as significant signs of myocardial ischaemia. RESULTS. All groups showed reductions in MAP and HR on induction that were marked in the P group. Intubation caused elevation of MAP and HR to pre-induction levels (HR: all groups) or slightly above (MAP: E, M). Four patients in the P group and 3 in each other group showed significant ST-segment deviation prior to induction. In the P group these deviations disappeared in 2 patients after injection while they remained unchanged in the M group. In the E group injection had no effect on the ischaemic ECG changes but produced another case of significant ST-segment deviation. Laryngoscopy and intubation produced no further significant ST-segment deviation in either group. DISCUSSION. Induction is a critical phase of anaesthesia, especially in patients with limited coronary reserve. Induction agents should alleviate the stress response while causing minimal haemodynamic changes. Despite marked reductions in MAP in the P group, the number of patients with ischaemic ECG changes was cut by half. Their number was unchanged or even raised in the other groups. After application of P, with an alleged reduction of coronary perfusion, a compensational reduction in myocardial oxygen consumption may occur.

[Characteristics of the QT interval in the ECG following reconstructive surgery of the common carotid artery]

In 40 patients undergoing thrombendarterectomy of the common carotid artery, the frequency-corrected QT interval in the ECG, as well as the serum sodium, potassium and total calcium were studied. Examination took place preoperatively 1.-3. hour postoperative and the 1. and 5. day postoperative. In 13 patients, pathological prolongation of QT interval (greater than 440 msec) was already found pre-operatively. Postoperative significant QT interval prolongations could not be found in any patient, independent of the site of operation or pre-operative findings. The total serum calcium concentration was postoperatively significantly reduced (P less than 0.01). There was no correlation between the reduced total serum calcium and the QT interval in the ECG. The findings contradict the assumption that clinically relevant reduction of the autonomous cardial innervation is frequent in patients undergoing thromboendarterectomy of the common carotid artery.

[The effect of flumazenil on alfentanyl-induced respiratory depression]

Use of the benzodiazepine antagonist flumazenil may inhibit the effects of benzodiazepines in a competitive manner. The only known partially agonistic effect of flumazenil is a weak anticonvulsive action at high doses. However, reports have claimed that flumazenil reduces the MAC of isoflurane in animal studies. Other reports have found that antagonizing midazolam-induced sedation or anesthesia by flumazenil led to an increase in respiratory depression. The aim of this study was to examine whether flumazenil i.v. increases fentanyl-induced respiratory depression. METHODS. In two separate sessions, ten healthy young volunteers were given either 0.0027 mg/kg fentanyl alone or 0.0027 mg/kg and 1 mg flumazenil i.v. over 4 min each time. The CO2 rebreathing method was used to determine the ventilatory response. RESULTS. Fentanyl alone brought about a significant reduction in CO2 response, characterized by a shift to the right and a decrease in the slope of the rebreathing curve (from 1.95 +/- 0.76 l.min-1.mmHg-1 to 0.86 +/- 0.53 l.min-1.mmHg-1). The infusion of additional flumazenil caused similarly significant respiratory depression (from 2.21 +/- 1.0 l.min-1.mmHg-1 to 0.77 +/- 0.38 l.min-1.mmHg-1). In both groups changes persisted for at least 120 min. No statistically significant differences between the two groups could be detected. CONCLUSION. Flumazenil does not enhance fentanyl-induced respiratory depression. Flumazenil's weak, partially agonistic action is therefore of no clinical importance.

[Life-threatening lactic acidosis during total parenteral nutrition. Successful therapy with thiamine]

Two patients, 37 and 44 years old, respectively, developed severe metabolic acidosis after abdominal surgery which was followed by three weeks of total parenteral nutrition. Septicaemia, peritonitis or hypoxia were excluded as possible causes. Both patients had very high serum lactate concentrations (24.3 and 22.8 mmol/l, respectively). Conventional treatment with buffer agents was unsuccessful. Because vitamin B1 deficiency was suspected, two doses of 400 mg thiamine were administered. In both patients the extreme lactic acidosis disappeared immediately after the injections. Both patients were later discharged without any symptoms.

[Prolongation of the QT interval in the ECG following surgery of the neck (neck dissection)]

The QT interval on the ECG was determined in 40 patients undergoing major resection plus neck dissection. The readings were taken before operation, between 1 and 3 h after operation, and the 1st and the 7th day after the operation. The QT interval was prolonged significantly more often and more intensively in patients undergoing surgery on the right side (from 411 +/- 17 to 459 +/- 50 ms) than in those operated on the left side (409 +/- 14 to 431 +/- 32 ms; all values mean +/- SD). The cause of the prolongation of QT interval is thought to be either direct surgical damage to the sympathetic cardiac nerves during the operation, or a temporary disturbance of nerve function due to pressure, tension or oedema in the wound. An explanation for the observed side difference might be differing functional effects of right- and left-sided sympathetic innervation of the heart. Attention is drawn to the meaning of these findings as a predisposing factor for ventricular tachyarrhythmias.

[The plasma histamine level during anesthesia induction using midazolam]

Midazolam has not yet been investigated for its possible properties as a histamine releaser. The aim of the following study was to ascertain whether histamine release follows the i.v. injection of midazolam. METHODS. Twenty patients between 18 and 58 years of age were split into two groups at random. Either 0.15 mg/kg midazolam or 0.15 ml/kg NaCl 0.9% were injected i.v. Venous blood was drawn 2 min before and 2, 5, and 10 min after each injection. The content of histamine in plasma was determined by HPLC. RESULTS. In the midazolam group, histamine levels decreased from 0.37 ng/ml to 0.29 ng/ml after 5 min (P less than 0.05). The kinetics typical of histamine release could not be observed in any of the patients. We observed a slight decrease in the blood pressure or tachycardia in 3 patients, but even in these cases there was no increase in histamine level. In the NaCl group, the histamine level decreased from 0.34 ng/ml to 0.23 ng/ml after 2 min (P less than 0.05). The hemodynamics of these patients remained unchanged. One patient had an abnormally high histamine level prior to the injection (2.33 ng/ml). CONCLUSION. Our results show that midazolam is not a histamine releaser. The relevance of 1 patient having a high baseline level of histamine remains unclear.

[The pharmacokinetics of midazolam following intramuscular administration]

There have been conflicting reports on the pharmacokinetics of midazolam, administered i.m. The aims of this study were to determine the pharmacokinetic data of midazolam following different doses and to test whether a correlation exists between its plasma level and sedative effect. METHODS. Fifteen patients between the ages of 18 and 50 were divided into three groups for i.m. administration of midazolam 0.05 mg/kg (group 1), 0.1 mg/kg (group 2), or 0.15 mg/kg (group 3) i.m. Venous blood was drawn 6, 12, 18, 24, 30, 36, 42, 48, 54, 60 min, and 2, 3, 4, 6, 8 h after the injection. After the same times the sedative effect was estimated by the anesthetist (awake, sleeping but easy to wake, sleeping and difficult to wake, unconscious). The plasma midazolam levels were determined by gas chromatography. The following pharmacokinetic parameters were ascertained: Cmax (peak concentration), tmax (time to attain peak concentration), clearance, elimination half-life. RESULTS. The peak concentration is directly proportional to the dosage of midazolam and the relation between the two is linear. The median Cmax values were 35.3 ng/ml (group 1), 103 ng/ml (group 2) and 123.5 ng/ml (group 3). The duration of tmax was between 12 and 36 min (means = 27 min). There was no significant difference between the groups in clearance, tmax, or elimination half-life. A significant correlation was found between the plasma midazolam levels and the degree of sedation. However, we observed a considerable variability in the effect. CONCLUSION. A 95% confidence interval for the prediction of the peak concentration of midazolam after i.m. injection is stated. Midazolam should be administered at a dose of 0.05 mg/kg at the most, if unconsciousness after premedication is to be avoided.

[The pharmacokinetics of midazolam in various kinds of anesthesia]

Several authors reported a decrease in metabolism of drugs during inhalational anesthesia. In this study we investigated the influence of several kinds of anesthesia on the metabolism of midazolam. Methods. In 43 patients who underwent minor surgery, anesthesia was induced by injecting 0.2 mg fentanyl followed by 0.15 mg/kg midazolam. Anesthesia was maintained by either halothane/nitrous oxide (group 1), isoflurane/nitrous oxide (group 2), fentanyl/droperidol/nitrous oxide (group 3), or halothane/air/oxygen (group 4). Venous blood was drawn after 5, 15, 30, 60, 90, 120, 180, 240, 300 and 360 min. Using the two-compartment model we estimated distribution half-life (t1/2a), elimination half-life (t1/2el), clearance (Cl), and volumes of distribution (Vz = volume in elimination phase). Results. There were no significant differences of elimination parameters between the four groups. Elimination half-life ranged from 0.72 to 15.06 h. Cl ranged from 2.5 to 12.8 ml/min per kilogram. Four patients (= 9%) had a t1/2el of 7-15 h; in 16 cases we found secondary concentration peaks. There was no correlation between drowsiness in the postoperative period and midazolam concentration. Conclusion. Even if anesthesia should influence the metabolism of midazolam, for example by reducing liver blood flow, we did not find any difference between the four groups. In accordance with others, we found some patients with a half-life of up to 15 h, which might reflect the influence of the anesthesia itself.(ABSTRACT TRUNCATED AT 250 WORDS)

[Stomach rupture following normo-frequent jet ventilation]

We report a case of a gastric rupture following jet ventilation during laryngoscopy.

[Continuous Midazolam infusion for sedation of respirator patients]

Most intensive care (ICU) patients need pharmacological sedation during ventilatory support. The short-acting drug midazolam might be preferable to neuroleptic agents and opiates because of its anxiolytic and sedative properties. The dosage of a drug given in a continuous infusion is based upon knowledge of its clearance and of the function of concentration and effect.

METHOD

A midazolam infusion (7.5 or 15 mg/h) was given to 16 patients receiving ventilatory support for 24 h. Clearance was estimated using the rule Cl = R/C (R = rate of infusion, C = concentration in steady state). To estimate the concentration of midazolam necessary for good sedation, the amount of supplementary injected neuroleptic during midazolam infusion was compared with that of the day before. Plasma cortisol and parameters of energy metabolism, electrolytes, and liver and kidney function were measured.

RESULTS

Patients with disease of abdominal organs showed the lowest values for clearance (1.0-2.92 ml/min/kg). Some of the injured patients showed elevated values for clearance (3.0-21.36 ml/min/kg). Elimination half-life ranged from 1.5-50 h. Changes in intestinal perfusion or cardiac output might be responsible for the wide range. For good sedation, plasma midazolam concentrations had to be above 600 ng/ml. Plasma cortisol levels were not affected by midazolam, nor were metabolism, electrolytes, or liver and kidney function.

CONCLUSION

Continuous infusion of midazolam is a useful way of sedation for ICU patients, but the wide range of clearance values must be considered.