Seeking a way to promote the use of constructed wetlands for domestic wastewater treatment in developing countries.

The aim of this study was to evaluate the domestic wastewater treatment efficiency as well as the survivability of commercially valuable ornamental plants in subsurface flow wetlands (SSFW) for domestic wastewater (DWW) treatment in laboratory and pilot wetland studies. The laboratory scale study included five different species (Zantedeschia aethiopica, Strelitzia reginae, Anthurium andreanum, Canna hybrids and Hemmerocallis dumortieri) that were evaluated in horizontal flow subsurface treatment cells. All the plants survived during the 6-month experimental period demonstrating high wetland nutrient treatment efficiency. In order to validate and expand these preliminary results, a pilot-scale wetland study was carried out in SSFWs under two different flow regimes (horizontal and vertical flow). Four ornamental species were tested during a 1-year period: Zantedeschia aethiopica, Strelitzia reginae, Anthurium andreanum and Agapanthus africanus. The removal efficiencies were significantly higher in the vertical subsurface-flow constructed wetlands (VFCW) for all pollutants, except for nitrate (NO(3)-N), total nitrogen (TN) and total suspended solids (TSS). These results show that it is feasible to use select non-wetland plants with high market value in SSFWs without reducing the efficiency of the wastewater treatment system, although future work should continue in order to apply this technology in a large scale. The added value of floriculture in treatment wetlands can help to promote the use of constructed wetlands (CW) for domestic wastewater treatment in developing countries where economical resources are scarce and water pollution with DWW is common.

Effect of prosthetic material on adhesion formation after laparoscopic ventral hernia repair in a porcine model.

Intraperitoneal placement of prosthetic mesh causes adhesion formation after laparoscopic incisional hernia repair. A prosthesis that prevents or reduces adhesion formation is desirable. In this study, 21 pigs were randomized to receive laparoscopic placement of plain polypropylene mesh (PPM), expanded polytetrafluoroethylene (ePTFE), or polypropylene coated on one side with a bioresorbable adhesion barrier (PPM/HA/CMC). The animals were sacrificed after 28 days and evaluated for adhesion formation. Mean area of adhesion formation was 14% (SD+/-15) in the PPM/HA/CMC group, 40% (SD+/-17) in the PPM group, and 41% (SD+/-39) in the ePTFE group. The difference between PPM/HA/CMC and PPM was significant ( P=0.013). A new visceral layer of mesothelium was present in seven out of seven PPM/HA/CMC cases, six out of seven PPM cases, and two out of seven ePTFE cases. Thus, laparoscopic placement of PPM/HA/CMC reduces adhesion formation compared to other mesh types used for laparoscopic ventral hernia repairs.

Hand-assisted laparoscopic splenectomy for giant spleens.

BACKGROUND: Laparoscopic splenectomy for massive splenomegaly is technically difficult, and the morcellated splenic tissue may be inadequate for histologic study. A hand-assisted technique may provide a technical advantage and allow removal of larger pieces of spleen. METHODS: Patients who underwent hand-assisted laparoscopic splenectomy for massive splenomegaly were reviewed. Demographic information, operative data, and outcomes data were tabulated. RESULTS: Sixteen patients met these criteria. Mean age was 56 years (range, 35-78 years). Operating time averaged 240 min (range, 165-360 min), and median blood loss was 425 cc (range, 100-1800 cc). There were no conversions to an open procedure. Mean weight of extracted spleens was 2008 g (range, 543-4090 g). Postoperative length of stay averaged 3.3 days (range, 2-7 days). There was one postoperative complication (6.25%) and no mortality. CONCLUSIONS: Hand-assisted laparoscopic splenectomy for massive splenomegaly is feasible and safe while preserving the recovery benefits of minimal access surgery. It provides an adequate specimen for histologic study.

Results of laparoscopically assisted colon resection for carcinoma.

BACKGROUND: Surgical resection is the primary treatment for colorectal carcinoma. Laparoscopically assisted colon resection technically is feasible for both benign and malignant disease. However, the role of laparoscopically assisted colon resection for carcinoma is controversial. METHODS: We prospectively studied our first 100 patients with colorectal carcinoma who successfully underwent laparoscopically assisted colon resection for the carcinoma. RESULTS: The pathologic stages were Dukes' categories A-16, B-52, C-25, and D-7. Operative mortality and morbidity were 2% and 22%, respectively. During a mean follow-up period of 40.3 months, recurrence by stage was zero patients with stage A disease, five patients with stage B disease, nine patients with stage C disease. Thirteen of these patients died as a result of their disease. At this writing, 60 patients are alive without evidence of disease, and 23 have completed the study disease free after more than 60 months. The 5-year survival probabilities by stage were 100% for stage A, 76.8% for stage B, and 51.7% for stage C. CONCLUSIONS: Laparoscopically assisted colectomy for cancer can be performed safely. The recurrence rate after laparoscopically assisted resection appears to be at least as good as after open resection. Results from ongoing prospective, randomized trials are needed to confirm these findings.

Postoperative antibiotic use of septoplasty: a survey of practice habits of the membership of the American Rhinologic Society.

Prophylactic antibiotics are used routinely in otolaryngology. Little objective data exist concerning their use in sinonasal procedures. We wished to determine the practice patterns of otolaryngologists regarding prophylactic antibiotics for septoplasty patients. A survey of 743 (60.3% responded) members of the American Rhinologic Society was used to get information about their practice habits and rationale for using antibiotics after septoplasty. Sixty-six percent of respondents routinely used antibiotics. Postoperative infection and toxic shock syndrome (TSS) were the primary indications. Forty-four percent of respondents used some form of packing and 38% used a splint. There was no relationship between the annual number of procedures and the reasons for using antibiotics. Doctors who performed more than 50 cases a year were less likely to use packing or splints (p < 0.001). Older surgeons used less younger surgeons a packing/splints (p < 0.001). Respondents who used packing/ splints were more likely to use antibiotics (p = 0.008). Older respondents used packing whereas younger respondents used splints (p = 0.002). The rationale for antibiotics varied by age; re more concerned with TSS and older physicians were more concerned with infection (p = 0.005). This survey shows great variability in the usage and rationale for antibiotics after septoplasty.

Effect of photodynamic therapy on revascularization of fasciocutaneous flaps.

OBJECTIVE: Photodynamic therapy (PDT) may be used as an adjuvant intraoperative treatment to improve locoregional control. PDT has been shown both to delay wound healing and to have a deleterious effect on flap survival after a primary ischemic insult. This delay in wound healing may make the flap dependent on its pedicled blood supply for a prolonged period. Long-term flap loss may be experienced. The effect of PDT on flap revascularization, with subsequent dependence on its vascular pedicle, is evaluated. STUDY DESIGN: Randomized controlled trial using a rodent model. METHODS: A rat fasciocutaneous flap was used. Study groups were as follows: group I received no treatment; group II received treatment with 630-nm light; groups IH and IV were given Photofrin (in group III, loupes without a fiberoptic light source were used for flap elevation, and in group IV, light source was employed); and group V was given Photofrin and 630-nm light. Primary ischemic times of 2 or 4 hours were used. Vascular pedicles were ligated on postoperative day (POD) 5, 6, or 7, and percentage of flap survival was evaluated 7 days later. RESULTS: With 2 hours of ischemia, revascularization was decreased in the PDT group on POD 6 (P < .05) and on day 7 (P < .005) when compared with the other groups. With 4 hours of ischemia, revascularization was decreased in the PDT group on PODs 5 (P < .001), 6 (P < .01), and 7 (P < .005). CONCLUSION: Intraoperative PDT decreases revascularization of a rat fasciocutaneous flap.

Differentiation of autoimmune thrombocytopenia from thrombocytopenia associated with immune complex disease: systemic lupus erythematosus, hepatitis-cirrhosis, and HIV-1 infection by platelet and serum immunological measurements.

A method and approach are described to differentiate classic autoimmune thrombocytopenia (ATP) from immune complex-associated thrombocytopenia in systemic lupus (SLE), hepatitis/chronic liver disease (LIV-ITP) and HIV-1 related thrombocytopenia (HIV-1-ITP). The platelet immunologic profile of IgG, C3C4 and IgM was measured with a solid-phase ELISA, employing 125I-staphylococcal protein A to detect indicator antibody binding. Polyethylene glycol was employed to precipitate immune complexes (PEG-IC). Platelet-associated IgG (PAIgG) was 2.8-, 5.6- and 5.8-fold higher in SLE, LIV-ITP and HIV-1-ITP patients respectively compared to ATP patients: platelet C3C4 was 3.2-, 4.8- and 4.5-fold higher respectively; platelet IgM was 2.2-, 3.7- and 3.8-fold higher respectively; serum PEG-IC levels were 4.2-, 4.8- and 2.1-fold higher respectively. With all parameters measured, there was no overlap between the 75th percentile for ATP patients and the 25th percentile for all three cohorts. The likelihood of having a platelet C3C4 level higher than the highest ATP level was 69% for SLE, 90% for LIV-ITP and 94% for HIV-1-ITP respectively; with PEG-IC measurements the likelihood was 83%, 100% and 100% respectively. Serum IgG, C3, C4, IgM and PEG-IC were examined for a possible relationship with platelet measurements. Except for a positive correlation between serum and platelet IgM in ATP, r = 0.5, P < 0.04, there was no positive correlation with any of the parameters measured. An inverse correlation was noted between PEG-IC level and platelet C3C4 in SLE, r = 0.7, P < 0.04. Thus platelet immunologic profile and serum PEG-IC level measurements differentiated classic ATP from immune complex-associated thrombocytopenias (SLE, LIV-ITP, HIV-1-ITP). Except for IgM measurements in ATP, platelet measurements could not be attributed to their respective serum concentration.

Management paradigms for posterior epistaxis: A comparison of costs and complications.

OBJECTIVES: Posterior epistaxis is a common otolaryngologic emergency. Management is controversial because of the many treatment options available. These options vary in efficacy, rates of complications, and cost. Posterior nasal packing is the medical management most frequently used to control posterior epistaxis. It is associated with major complications, including stroke, myocardial infarction, arrhythmias, and death. Because of these potential complications, many otolaryngologists monitor patients with posterior nasal packing in the intensive care unit (ICU). However, the level of care used to monitor these patients is variable, and standards have not been established. METHODS: From 1991 to 1997, 46 patients had posterior nasal packing placed to control epistaxis. Management, complications, and hospital charges were analyzed. RESULTS: Six patients (13%) were admitted to the ICU, 2 (4%) were admitted for telemetry monitoring, and 38 (83%) were sent to the ENT ward for continuous pulse oximetry. Four major complications occurred (1 episode of syncope [emergency department], 2 arrhythmias [ICU], and 1 death [hospice]). Twenty-six patients were treated with posterior packing in the ENT ward, at a mean cost of $2988. Fourteen patients underwent intervention (5 ligations, 6 endoscopic cauterizations, and 3 angiograms), with a mean cost of $5482. Six patients spent time in the ICU, with a mean cost of $8242. Patients treated in the ENT ward had significantly lower costs than those undergoing intervention (P = 0.017) or those admitted to the ICU (P = 0.020). CONCLUSION: We propose that most patients with posterior epistaxis can be treated in specialized ENT wards. This can be done without increasing complications and with significantly decreased costs.

Pharmacodynamics and the plasma concentration of mivacurium during spontaneous recovery and neostigmine-facilitated recovery.

BACKGROUND: The authors examined the plasma concentrations of the isomers of mivacurium and its pharmacodynamics during spontaeous and neostigmine-facilitated recovery after a mivacurium infusion. METHODS: Sixteen patients receiving nitrous oxide-opioid anesthesia received 0.25 mg/kg mivacurium. Patient response to neuromuscular stimulation was determined using a mechanomyograph Once T1 had recovered to 25% of its baseline height, a mivacurium infusion was begun and adjusted to maintain 95-99% neuromuscular block. The infusion was discontinued after 90 min and muscle strength allowed to recover either spontaneously or after neostigmine/glycopyrrolate (0.05/0.01 mg/kg). Plasma concentrations of the isomers of mivacurium after discontinuation of the infusion were determined using an HPLC assay. Differences between the groups were determined using a one-way analysis of variance with a Bonferroni-corrected t test or Student t test as appropriate. P < or = 0.05 was considered significant. RESULTS: Differences in the times for recovery to a train-of-four ratio of 70% did not achieve statistical significance (mean+/-SD, 13.3+/-6.0 vs. 16.3+/-2.5 min for the neostigmine and spontaneous groups, respectively). Plasma cholinesterase activity decreased significantly from baseline values after administration of neostigmine (5.88+/-0.21 vs. 0.43+/-0.04 U/ml plasma). Plasma concentrations of the trans-trans isomer were significantly greater in the neostigmine group than in the spontaneous recovery group 5, 6, 8, and 10 min after discontinuation of the infusion. Differences in the plasma concentration of the cis-trans isomer did not achieve statistical significance. CONCLUSIONS: Although administration of neostigmine decreased plasma cholinesterase activity and caused the trans-trans isomer to remain in the plasma at higher concentration, it did not delay recovery from mivacurium-induced block.

Effect of photodynamic therapy on the critical primary ischemic time of fasciocutaneous flaps.

BACKGROUND: Photodynamic therapy (PDT) may be used as an adjuvant intraoperative therapy to improve locoregional control. PDT has been shown to delay wound healing. This raises concern about PDTs effect on survival of fasciocutaneous flaps. OBJECTIVE: Evaluate the effect of 1) PDT on the critical ischemic time in a rat fasciocutaneous flap model and 2) photosensitizer activation by the surgical light source. DESIGN: A fasciocutaneous flap, based on the left inferior epigastric vessels, was used. Ischemic times of 2, 4, 6, 8, 10, and 12 hours were induced by clamping the vascular pedicle. Animals were randomly divided into five groups: ischemia only, group I; light treatment to wound bed, group II; Photofrin before surgery with the flap elevated without a fiber optic head light, group III, or with a headlight, group IV; Photofrin prior to surgery with light treatment to the wound bed, group V. Flap survival was assessed on postoperative day 7. RESULTS: The critical primary ischemic time of group V (PDT) was significantly less (P < .05) than groups I, II, III, and IV. There was no statistical difference in the critical primary ischemic time when a fiber optic headlight was used (group III vs. group IV). CONCLUSION: Intraoperative PDT significantly reduces the critical primary ischemic time of the rat fasciocutaneous flap. White light illumination of the operative field does not result in photosensitizer activation and has no effect on the critical primary ischemic time.

Effect of clamp versus anastomotic-induced ischemia on critical ischemic time and survival of rat epigastric fasciocutaneous flap.

BACKGROUND: There are many models used to explore ischemic-related phenomena. The rat epigastric fasciocutaneous flap model is the one most commonly used. Critical ischemic time is the maximum ischemic insult that tissue can undergo and still remain viable. Experimentally, ischemia is induced either by clamping the vascular pedicle or by dividing the pedicle then performing microvascular arterial and venous anastomosis. We sought to determine what effect the different methods of inducing ischemia have on the critical primary ischemic time and, thus, flap survival. METHODS: A right 3 cm x 6 cm groin flap based on the inferior epigastric vessels was raised in each rat. Ischemic times of 4, 6, 8, or 10 hours were induced either by placing temporary occlusion clamps on each vessel of the vascular pedicle (island pedicle group) or by ligation and division of the pedicle with subsequent microvascular anastomosis (free flap group). Survival was assessed at 7 days. RESULTS: The primary ischemic time at which one half of free flaps are predicted to die was calculated to be 7.60 hours, compared with 6.09 hours for the island pedicle flaps (p<.05). CONCLUSIONS: Fasciocutaneous flaps undergoing ligation and anastomosis are more resistant to ischemia than are those undergoing clamping of the pedicle. Possible etiologic factors responsible for this experimental finding are discussed.

Atypical presentations of actinomycosis.

BACKGROUND: Actinomycotic infections of the cervicofacial region are uncommon. Most major medical centers report approximately one case per year. Presenting clinical manifestations are confusing because they often mimic other disease processes. Diagnosis may be difficult due to a general lack of familiarity with the disease and the fastidious nature of the organism in culture. The cervicofacial manifestations of actinomycosis are varied, and a high index of suspicion is required to make an accurate and timely diagnosis. METHODS: Retrospective chart review with the presentation of four unusual cases of actinomycosis were performed. RESULTS: Two patients were initially seen with dysphagia from a tongue base mass. The third patient was initially seen with a 3-week history of worsening hoarseness and stridor. Examination revealed an ulcerative lesion of the left hemilarynx and pyriform sinus. All three patients were thought to have a neoplastic process. Diagnosis was made on histologic examination of a tissue biopsy. The fourth patient was initially seen with a buccal space mass that was draining externally. Culture of the purulent drainage revealed Actinomyces. In all four cases, symptoms resolved after appropriate antimicrobial therapy. CONCLUSIONS: Actinomycosis of the head and neck, although rare, is an important entity to the otolaryngologist. A confusing clinical presentation combined with the fastidious nature of the organism make for a difficult diagnosis. A high index of suspicion is required to make an accurate diagnosis and institute the appropriate antibiotic therapy.

The nature of spontaneous recovery from mivacurium-induced neuromuscular block.

UNLABELLED: The hypothesis of this study was that, in a given patient, recovery from a tracheal intubating dose of mivacurium would indicate the time course of spontaneous recovery after discontinuation of an infusion of mivacurium. Thirty-eight male patients consented to participate in the study. After induction of anesthesia and endotracheal intubation, the ulnar nerve was stimulated with train-of-four (TOF) stimuli at 12-s intervals. Patients received 0.3 mg/kg mivacurium in two evenly divided doses of 0.15 mg/kg each, separated by 30 s. Complete ablation of TOF responses occurred in most patients. Once the first twitch in the TOF (T ) had recovered to 25% of its baseline height, a mivacurium infusion was begun to maintain 95% suppression of T1. As surgery was nearing completion, the infusion was discontinued, and neuromuscular function was allowed to recover spontaneously. Data were analyzed for recovery intervals after the administration of the initial doses of mivacurium and after discontinuation of the infusion. Analysis of variance was used to determine the strength of correlation between the time from administration of the initial 0.3 mg/kg dose to 5% recovery of T1 and the times to recovery of TOF ratios of 70% and 90%. The 25%-75% recovery interval after discontinuation of the infusion ranged from 2.8 to 11.3 min. The time interval after administration of mivacurium 0.3 mg/kg to 5% recovery of T1 correlated with both the time to recovery of a TOF ratio of 70% and 90%. Recovery to a TOF of 90% after discontinuation of the infusion required approximately the same amount of time as recovery to 5% T1 after the administration of 0.3 mg/kg mivacurium. Each patient's recovery of neuromuscular function after discontinuation of a mivacurium infusion was related to his recovery after the administration of 0.3 mg/kg mivacurium. Therefore, the need for pharmacologic antagonism of block can be anticipated well before the end of an anesthetic. IMPLICATIONS: Mivacurium (0.3 mg/kg) was administered to 38 patients. As they began to recover muscle strength, a mivacurium infusion was begun and later discontinued as surgery was nearing completion. Each patient's early recovery (administration to 5% recovery of T1) after the initial dose of mivacurium correlated well with more complete recovery of muscle strength after discontinuation of an infusion. This relationship enables early prediction of recovery speed after a mivacurium infusion.

The difficult airway: cardiopulmonary bypass--the ultimate solution.

BACKGROUND: Large, compressive thyroid masses are usually removed as an elective procedure. Rarely is a patient's condition allowed to progress to severe respiratory distress before surgical intervention is recommended. When allowed to progress, management of the airway can be problematic. METHODS: A case report of a patient with a neglected thyroid lymphoma is presented. RESULTS: The natural progression of the disease, leading to impending airway collapse, necessitated emergency management of the airway. Due to supraglottic edema and a large neck mass, traditional methods of securing the airway were not feasible. Initiation of femoral-femoral cardiopulmonary bypass, under local anesthesia, ensured adequate oxygenation and allowed a controlled tracheotomy to be performed. CONCLUSIONS: The result obtained suggests that this approach provides a safe solution for airway control when intubation or a surgically created airway is either unsuccessful or too hazardous.

[The clinical pharmacology of new benzylisoquinoline-diester compounds, with special consideration of cisatracurium and mivacurium]. / Die klinische Pharmakologie neuer Benzylisochinolin-Diester-Verbindungen. Unter besonderer Berücksichtigung von Cisatracurium und Mivacurium.

The benzylisochinoline muscle relaxants have a highly selective affinity to the motor endplate which is associated with an absence of autonomic side effects such as ganglionic and vagus block. The requirement of only low clinical doses also reduces histamine liberation. Muscle relaxants with high neuromuscular blocking potency have a slow onset. Both atracurium and cisatracurium undergo Hofmann-Elimination in the plasma whereas mivacurium is hydrolyzed by pseudocholinesterase. The difference in kinetics between these pathways render atracurium and cisatracurium muscle relaxants of intermediate duration of action while mivacurium is short acting. Cisatracurium, one of the ten stereoisomeres of atracurium, is 3 to 4 times as potent as atracurium, does not release histamine, has no cardiovascular side effects and, due to the small clinical doses resulting from its high neuromuscular blocking potency, produces only negligible quantities of laudanosine. Its ED95 is 0.05 mg/kg. Good intubation conditions can be expected within 1.5 to 2 min following 3- to 4-times the ED95. Thereafter is takes about 65 min for T1 to recover to 25% of control. Maintenance doses of 0.02 to 0.04 mg/kg have a duration of action of 15 to 20 min. An infusion of cisatracurium of 1.0 to 2.0 mcg/kg/min, is adequate to maintain a 90 to 95% neuromuscular block. The time of recovery is largely independent on the total dose of cisatracurium administered by either repeated injection or infusion. Mivacurium is a racemate of 3 stereoisomeres of which the trans-trans- and the cis-trans-compound account for 95% of the neuromuscular blocking effect. In adults the ED95 is 0.08 mg/kg. The ensuing recovery of T1 to 25% of control is about 15 min. Rapid injection of 3xED95 may transiently lower the arterial blood pressure and may produce skin flushing in an incidence of 30 to 40%. Larger doses should be injected slowly with 30 to 60 s. The onset of mivacurium neuromuscular block following 3xED95 is relatively slow (2 min). Maintenance doses of 0.05 to 0.1 mg/kg have a duration of action of 5 to 10 min. A 95% neuromuscular block may be maintained by an infusion of 3 to 12 micrograms/kg/min. The time of recovery does not depend on the total cumulative dose given by either repeated injection or by infusion. The duration of mivacurium neuromuscular block may be drastically prolonged in the presence of low or atypical plasmacholinesterase. Both neostigmine and edrophonium are suitable reversal agents. None of the presently available benzylisochinoline muscle relaxants has the potential to completely replace succinylcholine.

A comparison: the efficacy of sevoflurane-nitrous oxide or propofol-nitrous oxide for the induction and maintenance of general anesthesia.

STUDY OBJECTIVE: To compare sevoflurane-nitrous oxide with propofol-nitrous oxide for the induction and maintenance of anesthesia, and to determine the rates of recovery following each anesthetic. DESIGN: Randomized, controlled study. SETTING: Teaching hospital. PATIENTS: 50 ASA physical status I and II patients, ranging in age from 18 to 70 years. INTERVENTIONS: General anesthesia was induced with either sevoflurane or propofol and maintained with 60% to 70% nitrous oxide and either sevoflurane or a propofol infusion and supplemental fentanyl. At the conclusion of surgery, the oxygen flow was increased to 6 L/min and all anesthetics were discontinued simultaneously. Patients were monitored for the nature and speed of induction and emergency from anesthesia. MEASUREMENTS AND MAIN RESULTS: Induction of anesthesia was significantly slower in the sevoflurane group than in the propofol group (2.0 +/- 1.1 vs. 0.8 +/- 0.5 min, respectively). The ease of induction and the time required for emergence from anesthesia were the same in both study groups (eye opening: 9.0 +/- 4.4 min vs. 8.0 +/- 5.0 min; following commands: 11.2 +/- 5.0 min vs. 9.8 +/- 6.9 min; extubation: 9.1 +/- 4.5 min vs. 8.6 vs. 5.1 min in the sevoflurane and propofol groups, respectively). Patients in the sevoflurane group experienced nausea and vomiting more frequently than patients in the propofol group (13 and 5 patients vs. 3 and 0 patients in the sevoflurane and propofol groups, respectively), which were not related to the administration of neostigmine or intraoperative opioids. CONCLUSION: Sevoflurane allows for rapid inhalation induction of, and emergence from, general anesthesia.

Pharmacokinetics of cisatracurium in patients receiving nitrous oxide/opioid/barbiturate anesthesia.

BACKGROUND: Cisatracurium, one of the ten isomers in atracurium, is a nondepolarizing muscle relaxant with an intermediate duration of action. It is more potent and less likely to release histamine than atracurium. As one of the isomers composing atracurium, it presumably undergoes Hofmann elimination. This study was conducted to describe the pharmacokinetics of cisatracurium and its metabolites and to determine the dose proportionality of cisatracurium after administration of 2 or 4 times the ED(95). METHODS: Twenty ASA physical status 1 or 2 patients undergoing elective surgery under nitrous oxide/opioid/barbiturate anesthesia were studied. Patients received a single rapid intravenous bolus does of 0.1 or 0.2 mg x kg-1 (2 or 4 times the ED(95), respectively) cisatracurium. All patients were allowed to recover spontaneously to a train-of-four ratio > or = 0.70 after cisatracurium-induced neuromuscular block. Plasma was extracted, acidified, and stored frozen before analysis for cisatracurium, laudanosine, the monoquaternary acid, and the monoquaternary alcohol metabolite. RESULTS: The clearances (5.28 +/- 1.23 vs. 4.66 +/- 0.67 ml x min(-1) x kg(-1) and terminal elimination half-lives (22.4 +/- 2.7 vs. 25.5 +/- 4.1 min) were not statistically different between patients receiving 0.1 mg x kg(-1) and 0.2 mg x kg(-1), respectively. Maximum concentration values for laudanosine averaged 38 +/- 21 and 103 +/- 34 ng x ml(-1) for patients receiving the 0.1 and 0.2 mg x kg(-1) doses, respectively. Maximum concentration values for monoquaternary alcohol averaged 101 +/- 27 and 253 +/- 51 ng x ml(-1), respectively. Monoquaternary acid was not quantified in any plasma sample. CONCLUSIONS: Cisatracurium undergoes Hofmann elimination to form laudanosine. The pharmacokinetics of cisatracurium are independent of dose after single intravenous doses of 0.1 and 0.2 mg x kg(-1).