Transtracheal high frequency jet ventilation and iatrogenic injury

Editor—We read with interest the article by Bourgain andcolleagues,¹ who reported an 8.4% incidence of subcutaneousemphysema and 1% incidence of pneumothoraces with jet ventilationvia the transtracheal route. Transtracheal catheter placementis an extremely useful technique for patients with significantglottic pathologies such as obstructing glottic tumours, andcan be lifesaving. We do, however, have concerns over its usein     

Thrombocytosis in intensive care

We conducted a retrospective study of platelet count in 226patients admitted for critical care over a 5-month period, toexplore the incidence of thrombocytosis and its relation toadmission category, duration of ICU stay and outcome. Our findingsindicate that thrombocytosis is not rare in ICU patients. Atleast one platelet count greater than 450x10⁹ litre^–1was found in 21.7% of patients and was associated with lowerICU mortality (P=0.003), lower hospital mortality (P=0.006),but longer duration of ICU stay (P<0.0001). Thrombocytosismay serve as an independent predictor of favourable outcomein ICU patients. Br J Anaesth 2001; 87: 926–8     

Changes in intensive care admissions with an interval of 5 years: a case-matched comparison

Severity scoring systems, such as the Acute Physiology and ChronicHealth Evaluation II (APACHE II)¹, are used to predict the outcomeof patients admitted to the intensive care unit (ICU). Despiteimprovements in knowledge, equipment and skills, there is littleconvincing evidence from standardised mortality ratios (SMR:predicted hospital mortality/observed hospital mortality) thatintensive care outcome has improved over a period of time.²The inability to detect changes in ICU outcome over time maybe a result of limitations in severity scoring methods,³ orchanges in patient characteristics and severity of illness.A case-matched study of ICU admissions over two separate timeperiods is one way of investigating this issue. Data on ICU admissions with a diagnosis of isolated head injury,chronic obstructive airway disease (COAD) or asthma were extractedfrom the North Thames ICU database.² Where possible each admissionin 1992/1993 was matched for diagnosis, age and sex with oneadmission 5 yr later in 1997/1998. Differences between the timeperiods were examined using the Wilcoxon test. A P<0.05 wastaken to be significant. A total of 350 admissions were matched. From each time periodthere were 52 matched patients with isolated head injury, 86with COAD and 37 with asthma (Table 30). Average age was 52.6( 18.9, range 17–85) and 62% were male. No significant differences were found between selected matchedpatients admitted to ICU 5 years apart. The results suggestthat there have been no marked changes in either the patientpopulation or outcome over this time period.     

Incidence of adrenal insufficiency after severe traumatic brain injury varies according to definition used: clinical implications

Background. Adrenal insufficiency impacts on the haemodynamicmanagement of patients in intensive care. Very little is knownabout the incidence of adrenal insufficiency in the first 10days after traumatic brain injury. Methods. We retrospectively reviewed the charts of 113 traumaticbrain injury patients within 10 days of their injury. They allhad a high-dose corticotropin stimulation test performed becauseof haemodynamic instability. Blood cortisol concentrations weremeasured at baseline, 30 and 60 min after the administrationof high-dose corticotropin. The incidence of adrenal insufficiencywas determined according to various definitions used in theliterature. Results. The baseline cortisol concentration was <414 nmollitre^–1 (15 µg dl^–1) in 78% of patients and<690 nmol litre^–1 (25 µg dl^–1) in all patients.The cortisol concentration did not rise above 500 nmol litre^–1(18 µg dl^–1) at 30 and 60 min in 49 and 22% of patients,respectively. The cortisol concentration did not rise by 250nmol litre^–1 (9 µg dl^–1) at 30 and 60 minin 48 and 25% of patients respectively. Primary adrenal insufficiencydefined by an abnormal baseline cortisol concentration and anabnormal response to the high-dose corticotropin stimulationtest was present in 13–28% of patients according to thecut-off values used. Conclusions. The incidence of adrenal insufficiency varies from25 to 100% in the first 10 days after traumatic brain injury.The range of incidences reported illustrates the need for standardizationof the definition of adrenal insufficiency. This has a directimpact on treatment. Sampling at 60 min after the high-dosecorticotropin stimulation test seems to correlate better withthe maximum secreting capacity of the adrenal glands.      

Anaesthesia-related diplopia after cataract surgery

Editor—We were interested in Gomez-Arnau and colleagues’¹paper, which reported incidences of anaesthesia-related diplopiaof 0.39 and 1% following 2024 retrobulbar and 98 peribulbarblocks. Nineteen anaesthetists had performed these blocks duringa 3 yr period. Our own retrospective audit of 940 consecutiveperibulbar blocks for cataract surgery, performed personallyor directly supervised by four anaesthetists between June 1999and June 2000, found six cases of persistent postoperative verticaldiplopia—an incidence of 0.64%.² All our patients with diplopia showed an immediate postoperativehypertropia in the injected eye, and evidence of muscle weakness,which changed over the subsequent 4–6 weeks to hypotropiawith restricted elevation of the affected eye. This suggeststhat the inferior rectus was the affected muscle. All the     

Differential effects of thiopental on methacholine- and serotonin-induced bronchoconstriction in dogs

Background. Thiopental sometimes causes bronchospasm duringinduction of anaesthesia. In addition, we have reported previouslythat thiopental produced transient bronchospasm, which was blockedby atropine pretreatment, and worsened histamine-induced bronchoconstrictionin dogs. Previous in vitro reports suggest that synthesis ofcontractile cyclooxygenase products, such as thromboxane A₂,may be involved in the mechanism of bronchospasm. However, thein vivo spastic effects have not been defined comprehensively. Methods. Twenty-seven mongrel dogs were anaesthetized with pentobarbital.Bronchoconstriction was elicited with methacholine (0.5 µg kg^–1+5.0µg kg^–1 min^–1; Mch group, n=7) orserotonin (10 µg kg^–1+1 mg kg^–1 h^–1;5HT group, n=20), and assessed as percentage changes in bronchialcross-sectional area (BCA, basal=100%) using a bronchoscope.In the 5HT group, dogs were subdivided into four groups of fiveeach: S-5HT, I-5HT, 5HT-S and 5HT-A. In the S-5HT and I-5HTgroups, 30 min before serotonin infusion dogs were given salineand indomethacin respectively at 5 mg kg^–1 i.v. Inall groups, 30 min after bronchoconstrictor infusion started,dogs were given thiopental at doses between 0 (saline) and 20mg kg^–1. In the 5HT-S and 5HT-A groups, dogs weregiven saline or atropine 0.2 mg kg^–1 i.v. 5 min afterthiopental 20 mg kg^–1. Results. Methacholine and serotonin reduced BCA by about 50and 40% respectively. Thiopental 20 mg kg^–1 increasedand decreased BCA by about 20 and 10% in the Mch and 5HT groupsrespectively. Indomethacin and atropine did not attenuate thepotentiation of serotonin bronchoconstriction produced by thiopental. Conclusion. The present study indicates that thiopental mayattenuate or worsen bronchoconstriction induced by muscarinicor serotonin receptor stimulation, respectively. The synthesisof contractile cyclooxygenase products and cholinergic stimulationmay not be involved in the contractile effect of thiopentalon serotonin bronchoconstriction. Br J Anaesth 2003; 91: 379–84     

Prospective evaluation of a modified Early Warning Score to aid earlier detection of patients developing critical illness on a general surgical ward

Admissions to the intensive care unit (ICU) from the wards havea higher mortality when compared to patients admitted from theoperating theatres/recovery and accident and emergency department.¹Suboptimal care may contribute to morbidity and mortality ofpatients admitted from the ward.² Failure to appreciate physiologicalderangements of breathing and mental status has been demonstratedin patients who subsequently suffered cardiac arrest, and theseevents may have been apparent up to 8 h prior to the event.³⁴ The Early Warning Score (EWS) was developed as a simple scoringsystem to be used at ward level utilising routine observationstaken by nursing staff.⁵ Deviations from the normal score pointsand a total is calculated. The EWS was evaluated prospectively for 1 month. The score wasthen modified to include urine output, to make temperature deviationsless sensitive and to include normalised blood pressure (Table8). We then evaluated this prospectively for 9 months. A total score of 4 or more resulted in the patient being reviewedby ward medical staff and help sought from the intensive careteam if appropriate. Over a 9-month period 206 patients on twogeneral surgical wards were put on the scoring system, of these26 were admitted to the ICU. The APACHE II scores of these patientswas 16.6 (± 7.3). Eleven patients were admitted to theICU from the surgical ward who had not been monitored on themodified EWS and their admission APACHE II scores were 23.5(± 4.1). This compares with admission APACHE II scoresof 22.3 (± 5.5) in 43 patients admitted from surgicalwards in the 9-month period prior to introduction of the system.The introduction of the system has appeared to lead to earlierreferral to the intensive care unit.     

INTERACTION OF CYCLOSPORIN AND ITS SOLVENT, CREMOPHOR, WITH ATRACURIUM AND VECURONIUM

Interactions between Sandimmun (formulated as cyclosporin (CyA)in Cremophor and ethanol) and atracurium or vecuronium wereinvestigated inanaesthetizedcats. Duringstable50% blockade andwith a constant rate of infusion of the neuromuscular blockingdrugs, Sandimmun 0.8 mg kg^–1 or an equivalent amount ofits solvent moiety was injected over 5 min. Sandimmun potentiatedthe blockade induced by vecuronium (median infusion rate 110µg kg^–1 h^–1) from 50.7% before injection tomaximum 95.2% 17.3 min after injection (median values), whereasthe median blockade in cats receiving atracurium (median 250pig kg^–1 h^–1) increased from 51.3% to 72.4% after32.9 min. At 45 min after the injection the median blockadeswere 93.1% and 69.8%, respectively. In cats receiving vecuronium(median 104 µg kg^–1 h^–1) the solvent producedan increase in effect of from 51.1% to maximum 78.0% blockadeafter 5.4min and 61.5% after 45 min (median values). Interactionwith solvent was negligible in cats receiving atracurium. Weattribute the effect of the solvent to the Cremophor component.The mechanism of the interaction related to the cyclosporinis unknown. ^*Present address: Apothekernes Laboratorium A. S, Harbnitzalleen3, N-0275 Oslo 2, Norway.     

NEUROMUSCULAR BLOCK WITH DOXACURIUM (BW A938U) IN PATIENTS WITH NORMAL OR ABSENT RENAL FUNCTION

The characteristics of neuromuscular block inducedby doxacuriumwere compared in patientswith and without renal function. Seventeenpatientswith end stage chronic renal failure and18 patients with normalrenal function were anaesthetized with 0.5% halothane and nitrousoxidein oxygen and received doxacurium in aninitial dose of 25 µgkg^–1 (estimated from availabledata as an ED95 dose), withincremental doses of 5 µg kg^–1. At the end of surgery,residualneuromuscular block was antagonized witheither edrophonium1.0 mg kg^–1 or neostigmine 0.08 mg kg^–1. There wasno significant difference between the mean maximum blocks achievedwith doxacurium: 17.4% (renal failure group)and 11.6% (controlgroup) of control twitch heights, or between the mean timesto achieve maximum block (10.9 min and 10.8 min, respectively).Themean duration of action of doxacurium, indicated by the timefor twitch height to recover to 25% of control, was longerinthe renal failure group (120.8 min vs 66.7 minin the controlgroup) (ns). Similarly, the meanduration of action of incrementswas longer inthe renal failure group (27.4 min vs 20.5 min inthecontrol group). The rate of spontaneous recovery from doxacuriumas indicated by the time for twitch height to recover from 0to 5%, 5 to 10% and 10 to 25%, was not significantly differentin the two groups. Antagonism of doxacurium was achieved morereliably with neostigmine than with edrophonium in bothgroups.The administration of doxacurium was associated with minimalcardiovascular effects. ^*Department of Anaesthetics, St George's Hospital, BlackshawRoad, London SW17 OQT     

Does low-volume inter-scalene block attenuate the severity of diaphragmatic paresis?

Editor—I commend Riazi and colleagues¹ on their importantstudy demonstrating that the analgesic effect of an interscalenebrachial plexus block (ISBPB) may be achieved with an extremelylow volume (5 ml) of local anaesthetic, while simultaneouslyreducing the incidence of phrenic nerve palsy (from 100% to     

Comparison of articaine and bupivacaine/lidocaine for single medial canthus peribulbar anaesthesia

In a single-centre, randomized, double-blind study, we comparedthe efficacy of 2% articaine with that of a mixture of 0.5%bupivacaine and 2% lidocaine for peribulbar anaesthesia in cataractsurgery, using a single medial canthus injection technique.Eighty-two patients were allocated randomly to receive 7–9 mlof a mixture of 0.5% bupivacaine and 2% lidocaine or an equalvolume of 2% articaine with 1:200 000 epinephrine. Hyaluronidase30 iu ml^–1 was added to both solutions. Thedegree of akinesia was scored 1, 5 and 10 min after theblock, at the end of surgery and at discharge from the day caseunit. Primary outcome measures were the difference in ocularmovement scores 5 min after block and the need for supplementaryinferolateral injections. There was greater akinesia in thearticaine group at 5 min (P=0.01). Ten patients (24%) inthe articaine group and 21 patients (51%) in the bupivacaine/lidocainegroup required a supplementary injection (P=0.02). The mean(SD) volume of local anaesthetic required to achieve adequateblock for surgery was 9.7 (2.1) ml in the articaine group and11.0 (2.2) ml in the bupivacaine/lidocaine group (P=0.01). Therewas a faster offset of akinesia after surgery in the articainegroup (P=0.01). There were no differences between groups inthe incidence of reported pain or of minor complications. Inour study, 2% articaine with 1:200 000 epinephrine wassafe and efficacious for single medial canthus peribulbar anaesthesia. Br J Anaesth 2001; 87: 584–7     

Thenar muscle blood flow and neuromuscular effects of vecuronium in patients receiving balanced or isoflurane anaesthesia

We have tested the hypothesis that isoflurane potentiates non-depolarizingneuromuscular block via an increase in muscle blood flow. Anaesthesiawas induced with thiopentone 4–5 mg kg^–1 in 30 adultmale patients of ASA physical status I or II and was maintainedwith 70% nitrous oxide in oxygen supplemented with either abolus dose of fentanyl 4µg kg^–1 followed by an infusionof 1 7µg kg^–1 h^–1 (balanced anaesthesia group,n=15) or 1.1% end-tidal isoflurane (isoflurane group, n=15).Vecuronium 0.1 mg kg^–1 was given for neuromuscular block.The force of contraction of the adductor pollicis of the thumbin response to ulnar nerve stimulation was recorded. Thenarmuscle blood flow was measured continuously with a laser Dopplerflowmeter. Times required for the first twitch in the train-of-four(T1) to recover to 25%, 75% and 90% of its control value weremean 26.3 (SD 5), 35.3 (10), 43.5 (7) min and 39.2 (15), 53(12.5), 61.2 (10) min in the balanced anaesthesia and isofluranegroups, respectively (P<0.01). Recovery index (time betweenT1 25% and 75%) was prolonged significantly in the isofluranegroup. Administration of thiopentone significantly increasedthenar muscle blood flow from 2.6 (1.9) and 2.2 (1.5) ml min^–1/100g to 19.2 (14) and 21.7 (16) ml min^–11100 g in the balancedanaesthesia and isoflurane groups, respectively (P<0.001).The addition of fentanyl (balanced) or isoflurane to the anaestheticmixture produced further increases in thenar muscle blood flowto reach, respectively, 26.2 (16) and 26.8 (13.6) ml min^–1/1100g during steady state anaesthesia. Thenar muscle blood flowwas comparable in the two groups throughout the study. We concludethat isoflurane prolonged vecuronium-induced neuromuscular block.This prolongation was not related primarily to increase in muscleblood flow.     

Haematological malignancy in ICU

The admission of patients suffering haematological malignancyto the intensive care unit (ICU) is controversial due to theirpoor prognosis. The dilemma regarding admission has escalatedwith the development of more aggressive forms of chemotherapy.Whilst improving survival from primary disease these treatmentsalso result in an increase in life-threatening complicationsrequiring ICU admission.¹ Analysis of patients admitted to alarge ICU over a 3-yr period and data collected from surroundingregional hospitals has allowed determination of various prognosticfactors that may assist in patient management. A retrospective observational study on patients with haematologicalmalignancy admitted to ICU between January 1996 and July 1999was conducted. Patients admitted from medical and haematologicalwards and a regional cancer centre were included, as were datafrom regional ICUs. Data included malignancy type, reason foradmission, severity and duration of leucopenia, creatinine onadmission, Logistic Organ Dysfunction (LOD) score, requirementfor invasive ventilation and survival. Sixteen patients (8 male, 8 female) were admitted to the ICUwithin the specified time. An additional 13 patients were admittedto regional ICUs between January 1997 and July 1999. Haematologicaldiagnoses: Hodgkin’s lymphoma (7), non-Hodgkin’slymphoma (1), chronical lymphocytic leukaemia (3), chronic myeloidleukaemia (6), acute myelogenous leukaemia (6), acute lymphoblasticleukaemia (3), multiple myeloma (2). Admission to ICU was precipitatedby pneumonia (35%), adult respiratory distress syndrome (15%),sepsis (15%), multi-organ failure (15%), bleeding (12%) andgraft-versus-host disease (8%). On admission LOD scores rangedfrom 1–16 (average 6.5) and ICU mortality was 71%. Ofthe 30% surviving ICU, only 18% survived to long term (>6months). Survival was associated with not requiring mechanicalventilation, a normal white cell count or brief period of neutropenia.A creatinine on admission of greater than 200 µmol litre^–1was noted to be associated with mortality (P = 0.05). In logisticregression analysis haematological malignancy is significantlyassociated with in hospital mortality (P<0.005). This associationis strengthened when age is taken into account (P<0.001),but is not significant when organ severity is controlled for(P = 0.10). Relative risk of in hospital death for patientswith haematological malignancy admitted to ICU was 1.9 (OR 4.3695%CI 1.6–12.1). These results suggest that patients withhaematological malignancy are admitted to ICU with more severeillness than matched patients with other underlying disease. In conclusion it can be shown that a high mortality is associatedwith admission of such patients to ICU. Prognosis is guidedby several factors including the requirement for mechanicalventilation,² LOD score >10 and severe prolonged neutropenia.Improved prognosis is associated with normal white cell count,rapid recovery of bone marow³, normal admission creatinine andavoidance of mechanical ventilation.     

HAEMODYNAMIC EFFECTS OF THE PHOSPHODIESTERASE INHIBITOR ENOXIMONE IN COMPARISON WITH DOBUTAMINE IN ESMOLOL-TREATED CARDIAC SURGERY PATIENTS

In a randomized study, the haemodynamic effects of the new phosphodiesterase-III-inhibitor,enoximone, were compared with dobutamine in acutely ß-adrenoceptorblocked patients. Twenty patients scheduled for aorto-coronarybypass grafting suffering from tachycardia (heart rate (HR)> 100 beat min^–1) were treated by infusion of esmolol,an ultra-short acting, selective ß₁-blocker. Twentyminutes after the start of esmolo, either enoximone 0.5 mg kg^–1as a bolus (n = 10) or dobutamine 5 µg kg^–1 min^–1was administered. Haemodynamic effects were monitored for 40min, including measurement of left ventricular haemodynamics.Esmolol reduced HR (–27%) and dP/dt_max (–38%) significantlyin both groups. Cardiac index (Cl) was decreased also. Enoximoneincreased Cl (+35%) and dP/dt_max (+39%) significantly, whileno change in dobutamine-treated patients was observed. Systemicvascular resistance increased only in the dobutamine group (+44%).     

GLYCOPYRRONIUM REQUIREMENTS FOR ANTAGONISM OF THE MUSCARINIC SIDE EFFECTS OF EDROPHONIUM

We have compared, in 60 adult patients, the cardiovascular effectsof glycopyrronium 5 µg kg^–1 and 10 µg kg^–1given either simultaneously or 1 min before edrophonium 1 µgkg^–1. Significant differences between the four groupswere detected (P < 0.001). Both groups receiving 10 µgkg^–1 showed increases in heart rate of up to 30 beat min-1(95% confidence limits 28–32 beat min-1). Use of glycopyrronium5 µg kg^–1 provided greater cardiovascular stabilityand, given 1 min before the edrophonium, was sufficient to minimizeearly, edrophonium-induced bradycardias. This low dose of glycoprroniumprovided good control of oropharyngeal secretions. ^*Present address: Respiratory Unit, The Hospital for Sick Children,Great Ormond Street, London W. 1. Presented in part at the June 1987 meeting of the AnaestheticResearch Society.     

Pretreatment with remifentanil to prevent withdrawal after rocuronium in children

Background. Pain from rocuronium injection is a common side-effectreported to occur in 50–80% of the patients. This randomized,double-blind, placebo-controlled study was designed to evaluatethe efficacy of pretreatment with i.v. remifentanil on preventionof withdrawal response during rocuronium injection in paediatricpatients. Methods. After obtaining parental consents, 70 paediatric patientswere randomly allocated into two groups to receive either i.v.remifentanil 1 µg kg^–1 (remifentanil group, n=35)or i.v. saline 5 ml (saline group, n=35). Anaesthesia was inducedwith thiopental sodium 2.5% (5 mg kg^–1) and the test drugwas injected over 30 s. One minute after the test drug injection,rocuronium 1% (0.6 mg kg^–1) was injected over 5 s andthe response was recorded. Mean arterial pressure (MAP) andheart rate were recorded on arrival in the operating theatre,before and 1 min after the tracheal intubation. Results. The overall incidence of withdrawal movements was significantlyhigher in the saline group (33 patients; 94%) than that in theremifentanil group (8 patients; 23%) (P<0.001). No patientin the remifentanil group showed generalized movement, whereas51% of patients in the saline group did. Remifentanil preventedsignificant increase in MAP after intubation. Conclusion. This study demonstrated that pretreatment with remifentanil1 µg kg^–1 provided a safe and simple method forreducing the incidence of rocuronium-associated withdrawal movementwith haemodynamic stability in children.     

Analgesic effectiveness of caudal levobupivacaine and ketamine

Background: Ketamine is used increasingly in paediatric anaesthetic practiceto prolong the action of a caudal block. This study was designedto determine if adding S(+)-ketamine 0.5 mg kg^–1 allowsa lower concentration of levobupivacaine to be used for caudalanaesthesia without loss of clinical effectiveness. Methods: One hundred and sixty-four children (ASA I or II) aged 3 months–6yr were randomly allocated to receive 1 ml kg^–1 of levobupivacaine0.15% with 0.5 mg kg^–1 S(+)-ketamine (Group 1), levobupivacaine0.175% with 0.5 mg kg^–1 S(+)-ketamine (Group 2), or levobupivacaine0.2% (Group 3) by the caudal route. Pain, motor block, sedation,and requirement for postoperative analgesia were assessed upto 6 h after operation. Results: There was no significant difference between the groups in effectivenessat first surgical incision. Significantly lower analgesic requirementswere reported in Group 2 compared with Group 3 at wakeup, 180and 360 min after operation. Time to first rescue analgesiawas longer in Group 2 compared with Group 1 or 3. Kaplan–Meiersurvival analysis of analgesia free time demonstrated a significantadvantage of Group 2 over Groups 1 and 3 (log rank P=0.05).The incidence of postoperative motor block was not significantlydifferent between the groups. No excess sedation or dysphoricreactions were observed in the ketamine groups. Conclusions: The addition of 0.5 mg kg^–1 S(+)-ketamine to levobupivacaine0.175% for caudal analgesia for lower abdominal and urologicalsurgery is significantly more effective in providing postoperativeanalgesia than levobupivacaine 0.15% with 0.5 mg kg^–1S(+)-ketamine or levobupivacaine 0.2%.     

CARDIOVASCULAR AND RENAL HEMODYNAMIC EFFECTS OF DOPEXAMINE: COMPARISON WITH DOPAMINE

We have studied the effects of dopexamine and dopamine on systemicand renal haemodynamics in 20 male patients undergoing electivecoronary artery bypass surgery. Patients were allocated randomlyto two groups (n = 10) who were treated with incremental dosesof either dopexamine 1, 2 and 4 µg kg^–1 min^–1,or dopamine 2.5 and 5 µg kg^–1 min^–1, eachdose being maintained for 15 min. Measurements were performedbefore administration of the drug and at the end of the infusionperiod at each dose. Fentanyl and midazolam were used as anaestheticagents. Renal blood flow was measured with the argon washintechnique. Dopexamine 4 µg kg^–1 min^–1 producedan increase in cardiac index of 117% caused by a 65% reductionin afterload and an increase in heart rate by 61%. Dopamine5 µg kg^–1 min^–1 caused a 40% increase in cardiacindex as a result of an increase in stroke volume. Renal vascularresistance decreased more than systemic vascular resistancewith dopamine. With dopexamine, the increase in renal bloodflow (66%) was less than the increase in cardiac index, whilerenal vascular resistance and systemic vascular resistance declinedto almost the same extent. The results show that dopexamineexerts systemic and renal effects mainly via stimulation ofß₂-receptors. An action of dopexamine at renal DA₁-receptorscould not be demonstrated in this study.     

NEUROMUSCULAR AND CLINICAL EFFECTS OF MIVACURIUM CHLORIDE IN HEALTHY ADULT PATIENTS DURING NITROUS OXIDE-ENFLURANE ANAESTHESIA

We have studied the effects of mivacurium after induction ofanaesthesia with alfentanH-propofol in healthy adult oral surgicalpatients. Anaesthesia was maintained with nitrous oxide and0.75% (end-tidal) enflurane in oxygen after nasotracheal intubation.Recordings were made of the rectified compound adductor polliciselectromyogram in response to train-of-four (TOF) ulnar nervestimulation. First and fourth TOF responses were defined asT1 and T4. with T1 suppression referenced to pre-mivacuriumT1 height (Tc). Onset times (mean (SEM)) to 90% T1 suppressionwere 2.5 (0.2), 2.1 (0.3) and 1.6 (0.1) min, respectively, aftermivacurium 0.15 mg kg^–1 (n=18) and 0.2mg kg^–1 (n=18)as 5-s boluses and 0.2mg kg^–1 over 30 s (n = 9). Intubatingconditions 2 min after 0.15 mg kg^–1 were good to excellentand not improved by a further 30-s delay or by use of a 0.2-mgkg^–1 dose. Recovery to T1/Tc of 5% occurred on averagein 12–13 min irrespective of dose. Thereafter, mivacuriuminfusions commenced at 8–10 µg kg^–1 min^–1re adjusted at intervals of at least 3 min to achieve T1/Tcin the range 1–10%. Mean duration of infusion was 58 (3.4)min and mean infusion rate after a 15-min stabilization periodwas 6.6 (range 2.3–12.9) fig kg^–1min. On cessationof infusions, spontaneous recovery from T1/Tc fie 8% (1.0%)to T4:T1 = 0.7 took 17 (1.2) min. Neostigmine 0.04 mg kg^–1or edro-phonium 0.75mg kg evoked recovery from T1/Tc 9% (SEM1.2% and 1.0%, respectively) to T4:T1 = 0.7 in 11 (0.6) and8 (0.9) min (both P < 0.001 vs spontaneous recovery). Presented in part at the Anaesthetic Research Society, LondonMeeting, November 1989     

POSTOPERATIVE HYPOXAEMIA: COMPARISON OF EXTRADURAL, I.M. AND PATIENT-CONTROLLED OPIOID ANALGESIA

Arterial oxygen saturation (Sa_o2) was analysed continuouslybefore and for 24 h after lower abdominal surgery in 30 patientsbreathing air using one of three postoperative analgesic regimens:i.v. diamorphine using a patient-controlled analgesia system(PCAS), extradural diamorphine or i.m. morphine. Hypoxaemiawas defined as Sa_O2 < 94% for more than 6 min h^–1.Before operation there was no difference between the three analgesiagroups assessed by the duration when Sa_o2 was less than 94%.After operation the pattern of Sa_O2 vs time distribution waseither stable, with little variation from hour to hour withno hypoxaemia, or unstable with large variation with 30% ofpatients hypoxaemic. Thus three patterns of Sa₀₂ distributionwere seen in the postoperative period: stable without hypoxaemia(4/10 PCAS, 0/10 extradural, and 1/10 i.m. patients), unstablewithout hypoxaemia (4/10 PCAS, 5/10 extradural and 7/10 i.m.patients) and unstable with prolonged nocturnal periods withSa_o2 <94% for a mean of 17.7 min h^–1, 95% confidencelimits (CL) 10–25 min h^–1, (2/10 PCAS, 2/10 i.m.and 5/10 extradural patients). Before operation, the unstablegroup with hypoxaemia spent longer at < 94% Sa_o2 (mean 4.8min h^–1 95% CL 1.0–8.6 min h^–1) than the stablegroup (mean 0.4 min h^–1, 95% CL 0.17–0.61 min h^–1)and this was a predictor of postoperative hypoxaemia. Hypoxaemiaoccurred in all analgesia groups, but extradural diamorphinetended to cause longer periods. Some patients at risk of postoperativehypoxaemia may be predicted by preoperative monitoring of Sa_o2although extradural diamorphine boluses were associated withhypoxaemia in patients with normal preoperative values.