Bovine hemoglobin increases skeletal muscle oxygenation during 95% artificial arterial stenosis

BACKGROUND

This study investigates the effect of a stroma-free ultrapurified bovine hemoglobin solution (HBOC) on skeletal muscle tissue oxygenation in comparison with hetastarch during nearly complete arterial stenosis.

METHODS

Fourteen foxhounds were intravenously anesthetized and mechanically ventilated with 30% oxygen in air. Catheters were inserted into the right femoral artery and vein for measurements of hemodynamic parameters and blood gas sampling. Arterial blood flow of the left popliteal artery was measured by means of an electromagnetic flow probe. Skeletal muscle tissue oxygen tension (tpO2) was measured in the left gastrocnemius muscle by using a stepwise driven polarographic needle probe creating histograms from 200 single tpO2 measurements. After isovolemic hemodilution with Ringer's lactate solution to a hematocrit of 25%, a 95% artificial stenosis of the popliteal artery was established. The animals then randomly received two applications of either 50 ml HBOC (molecular weight, 32,000 to 500,000; hemoglobin, 13 +/- 1 gm/dl-1) or 200 ml 6% hetastarch 200,000/0.5. Variables were measured at baseline, after hemodilution, 30 minutes after stenosis, and 15 minutes after two applications of the respective compound.

RESULTS

Demographic data, muscle temperature, and arterial blood gases did not differ between groups. With the exception of higher mean arterial and mean pulmonary artery pressures in HBOC-treated animals, hemodynamics did not differ between groups. In both groups oxygen delivery and oxygen consumption of the muscle decreased in parallel to the decreasing blood flow during arterial stenosis. In contrast, oxygen extraction ratio increased after infusion of HBOC and was higher after the second application when compared with hetastarch-treated animals (p < 0.05). During stenosis tpO2 was decreased in both groups when compared with baseline (p < 0.001). Mean tpO2 remained at decreased levels after administration of hetastarch but increased to nearly baseline values after HBOC treatment (p < 0.001).

CONCLUSIONS

The data suggest that increased oxygen extraction in the HBOC group is associated with improved skeletal muscle tissue oxygenation during severe arterial stenosis.

[Special anesthesiological aspects in patients with Niikawa-Kuroki ("Kabuki Make-Up") syndrome]

The Niikawa-Kuroki ("Kabuki Make-up") syndrome (NKS) is a rare disease with a characteristic array of multiple congenital anomalies. The syndrome is characterised by distinct craniofacial dysmorphias, moderate mental retardation, skeletal abnormalities, cardiovascular and urogenital disorders, growth retardation and skeletal muscle abnormalities. The inheritance of NKS is not completely clear. However, the available data are compatible with an autosomal dominant mutation with variable expressivity. There is no specific treatment for NKS. The patients require intensive support for the development of their mental and physical capabilities. Furthermore, therapy includes operative correction of the multiple anomalies. The risk of anaesthesia is increased in these patients because of a possible difficult airway, cardiovascular and urogenital diseases, and abnormalities of the skeletal muscles. Special problems associated with the anaesthetic management in patients with NKS are discussed in this case report.

Continuous spinal analgesia. Comparison between patient-controlled and bolus administration of plain bupivacaine for postoperative pain relief

BACKGROUND AND OBJECTIVES

Adequate postoperative pain relief has been achieved in orthopedic patients by subarachnoid bolus administration of plain bupivacaine. This prospective randomized study compares bolus injections of bupivacaine with a patient controlled infusion via subarachnoid 28-gauge microcatheters for postoperative analgesia after elective hip replacement.

METHODS

Forty-two patients (mean age, 69 +/- 11 years) were randomly allocated to one of two groups. Group. 1 patients received a constant subarachnoid infusion of 0.6 mg/h of bupivacaine by a patient-controlled device and were allowed to self-administer 0.6 mg every 30 minutes Group 2 patients received a nurse-administered bolus of 3.75 mg of plain bupivacaine on request. Pain was assessed by patients and nurses by a visual analog scale (VAS) every hour. The degree of motor block and the level of analgesia were documented every 4 hours. Hemodynamic and respiratory parameters were recorded hourly. Differences between groups were tested by analysis of variance for repeated measurement.

RESULTS

Technical problems occurred in six patients were more frequent in group 1 but none in group 2. Patient-controlled analgesia resulted in lower pain scores than bolus application during 18 postoperative hours (VAS score 19 +/- 19 mm in group 1 and 39 +/- 30 mm in group 2; P < .01). Lower total doses of bupivacaine were required in group 1 (17.6 +/- 4 mg) than in group 2 (22.3 +/- 7 mg; P < .05). The groups did not differ with respect to the degree of motor block (Bromage score 3.5 +/- 0.5), the sensory level (L1-2 +/- 1), or hemodynamic or respiratory parameters.

CONCLUSION

In spite of a higher incidence of technical problems, patient-controlled analgesia with a continuous background infusion via microspinal catheters provides more effective postoperative analgesia, without hemodynamic or respiratory side effects, than bolus administration.

[Single-dose spinal anesthesia with a mixture of isobaric bupivacaine 0.5% and hyperbaric mepivacaine 4%]

BACKGROUND

Single-dose spinal anaesthesia with hyperbaric local anaesthetic provides profound analgesia and motor blockade and allows exact assessment of the analgesic level. The present prospective, randomised study compares a mixture of plain 0.5% bupivacaine and hyperbaric 4% mepivacaine with hyperbaric 0.5% bupivacaine with regard to onset time of analgesia and duration of the sensory and motor blockade.

METHODS

One hundred and twenty-two orthopaedic patients (69 m/53 f, aged 20-91 years) scheduled for elective lower limb surgery under spinal anaesthesia were randomly allocated to one of two groups. In group 1, 67 patients received a 1:1 mixture of plain 0.5% bupivacaine and hyperbaric 4% mepivacaine (density: 1,015 kg/m3, 37 degrees C). In group 2, 55 patients received hyperbaric 0.5% bupivacaine (density: 1,021). The lumbar puncture was performed between L3 and L5 using a 26 G Quincke needle through a 20 G introducer with the patients either in the sitting or lateral position. The local anaesthetic was administered with an injection speed of 1 ml per 5 s. Patients with a body height < 160 cm received 2.0 ml, those 160-180 cm 3.0 ml, and those > 180 cm 4.0 ml. The level of analgesia was registered every minute by pin-prick until the maximal analgesic level was reached. The time of regression of analgesia to the level of T 12 and regression of the motor block to Bromage scale 3 was registered. The data were analysed using Student's t-test with P < 0.05 considered as significant.

RESULTS

Demographic data did not differ between groups. In group 1, the onset time of analgesia was faster than in group 2 (8 +/- 3 vs. 14 +/- 5 min, P < 0.001). While in group 1 the onset time of analgesia was faster in patients injected sitting compared to those in the lateral position (p < 0.05), there was no position-related difference in group 2. The groups also did not differ with respect to the maximal level of analgesia and the duration of sensory and motor blockade.

CONCLUSIONS

The local anaesthetic mixture may be preferred to hyperbaric 0.5% bupivacaine in patients requiring a fast onset of analgesia associated with a 2-3 h duration of sensory and motor block.

[Acute theophylline intoxication as differential diagnosis of pneumothorax in an asthma patient]

The ambulance was called to a known asthmatic patient. On arrival, the team found a massively dyspnoeic, diaphoretic, non-cyanotic and somnolent patient. His medication consisted of oral theophylline (unknown dosage), fenoterol (metered-dose inhaler), as well as 8 mg oral prednisolone. On the day of emergency, the patient had been treated by two physicians who applied two doses of i.v. theophylline and one dose of s.c. terbutaline because of bronchoconstriction (dosage not documented). The patient's pulse was frequent with 200 beats/min, the blood pressure not measurable. Careful i.v. titration of metoprolol was started to decrease the patient's heart rate and increase diastolic filling and stroke volume. However, the patient showed a progressive circulatory collapse. Following diagnostic thoracocentesis to rule out a left-side pneumothorax, the patient required intubation and mechanical ventilation because of increasing cardiovascular instability. A tension pneumothorax developed immediately after mechanical ventilation and required rapid treatment with a chest tube. Nevertheless, CPR and intravenous infusion of catecholamines were necessary before the patient was referred to a medical intensive care unit where he died the same day in cardiogenic shock. Clinical signs and symptoms associated with an elevated theophylline plasma level make theophylline toxicity the probable causative event for the patient's emergency condition of acute theophylline intoxication.

[Does propofol have advantages over isoflurane for sufentanil supplemented anesthesia in children for strabismus surgery?]

OBJECTIVE

The present study investigates the effectivity and the incidence of side effects of sufentanil-supplemented propofol versus isoflurane anaesthesia in children undergoing elective strabismus surgery.

METHODS

130 children (aged 3-11; ASA I-II) were randomly allocated to one of four groups. In group 1 and 2, anaesthesia was induced with 2 mg/kg propofol and maintained with 15-20 mg/kg x h propofol and 30% O2 in air (group 1) or 10-15 mg/kg x h propofol in N2O (group 2). After induction with either 2 mg/kg propofol (group 3) or 5 mg/kg thiopentone (group 4), anaesthesia was maintained with 0.8-1.5 Vol% isoflurane and N2O in 30% O2 in these groups. All children were orally premedicated with midazolam and atropine and received a single dose of intravenous sufentanil (0.5 micrograms/kg) and atracurium (0.5 mg/kg) prior to intubation. Heart rate, mean arterial blood pressure and pulse oximetry were registered 5 min prior and after intubation as well as 10 min before and 5 min after extubation. The incidence of pain and involuntary movements during injection, oculocardiac reflex (OCR), laryngospasm and postoperative shivering were as well registered as the duration of the operation and the time of extubation. Episodes of nausea and vomiting were documented during 24 hours postoperatively.

RESULTS

TIVA with Propofol resulted in a decreased heart rate (p = 0.002) and a higher frequency of OCR (p = 0.01) than thiopentone/isoflurane anaesthesia with a higher sensitivity of children younger than 6 years (p = 0.007) in all groups. There were no differences in extubation time between groups. The overall incidence of nausea (p = 0.002) and vomiting (p = 0.007) was lower in group 1 and 2 when compared to group 3 and 4.

CONCLUSION

Propofol as an induction agent of balanced anaesthesia fails to show advantages over thiopentone. During total intravenous anaesthesia propofol increases the risk of bradycardia especially in younger children. However, a significantly lower incidence of postoperative nausea and vomiting after TIVA with propofol and sufentanil, irrespective of N2O administration, may be an advantage over isoflurane anaesthesia in paediatric patients after strabismus surgery.

[Acute effects of complete blood exchange with ultra-purified hemoglobin solution or hydroxyethyl starch on liver and kidney in the animal model]

OBJECTIVE

The present animal study investigates the influence of an acute and almost complete isovolaemic haemodilution with a new ultrapurified polymerized bovine haemoglobin (UPBH) on hepatic and renal function and histology in comparison to hydroxyethylstarch (HES).

METHODS

Eighteen anaesthetized dogs underwent progressive isovolaemic haemodilution with either HES (group 1) or UPBH (group 2) to haematocrit target levels of 15, 10 and < 5%. Haemodynamics, arterial and mixed-venous blood gases and blood chemistry were determined at each measurepoint. With a haematocrit value < 5%, biopsies were taken from the liver and kidneys and prepared for light and electron microscopic analysis. One dog without haemodilution figured as control animal. Statistical analysis was performed using ANOVA, with p < 0.05 considered significant.

RESULTS

In group 1, the cardiac output was increased in parallel to a decreasing vascular resistance, while in group 2 haemodynamic parameters remained unchanged. In group 1, avDO2 and final DO2 and VO2 were decreased. In contrast, avDO2 and oxygen extraction ratio were increased, while VO2 remained stable under decreasing DO2 in group 2. In both groups, coagulation values and blood chemistry showed dilution dependent changes. Colloid osmotic pressure and plasma viscosity were increased in both groups but COP was higher in group 1 compared to group 2. A lower urine output in comparison to group 1 and a maximal concentration of 0.27 g/dl of free haemoglobin in urine were seen in group 2. Liver biopsies showed no severe histological changes in both groups. Renal histology revealed severe alterations of proximal tubules after haemodilution with HES. In contrast, no histological indications for acute toxic or ischaemic lesions in the kidneys were seen after UPBH treatment.

CONCLUSION

The high degree of purification and polymerization of bovine haemoglobin associated with adequate tissue oxygenation by increased oxygen extraction resulted in normal histological and functional findings after acute and almost complete blood exchange with UPBH. In contrast, HES-treated animals showed severe histological changes of renal tubuli caused by isovolaemic anaemia.

Bovine haemoglobin is more potent than autologous red blood cells in restoring muscular tissue oxygenation after profound isovolaemic haemodilution in dogs

PURPOSE

This study compares the effects of stored red cells, freshly donated blood and ultrapurified polymerized bovine haemoglobin (HBOC) on haemodynamic variables, oxygen transport capacity and muscular tissue oxygenation after acute and almost complete isovolaemic haemodilution in a canine model.

METHODS

Following randomization to one of three groups, 24 anaesthetized Foxhounds underwent isovolaemic haemodilution with 6% hetastarch to haematocrit levels of 20%, 15% and 10% before they received isovolaemic stepwise augmentation of 1 g.dl-1 haemoglobin. In Group 1, animals were given autologous stored red cells which they had donated three weeks before. In Group 2, animals received freshly donated blood harvested during haemodilution. In Group 3, animals were infused with HBOC. Skeletal muscle tissue oxygen tension was measured with a polarographic 12 mu needle probe.

RESULTS

In all groups, heart rate and cardiac index were increased with decreasing vascular resistance during haemodilution (P < 0.05). Haemodynamic variables showed a reversed trend during transfusion when compared to haemodilution but remained below baseline (P < 0.05). Arterial and venous oxygen content were changed in parallel to changes of haematocrit and haemoglobin concentrations but were lower in Group 3 than in Groups 1 and 2 (P < 0.05) during transfusion. In contrast, the oxygen extraction ratio was higher in Group 3 (59 +/- 8%, P < 0.01) at the end of transfusion than in Group 1 (37 +/- 13%) and 2 (32 +/- 5%). In Group 3, mean tissue oxygen tension increased from 16 +/- 5 mmHg after haemodilution to 56 +/- 11 mmHg after transfusion (P < 0.01) and was higher than in Group 1 (41 +/- 9, P < 0.01) and Group 2 (29 +/- 11, P < 0.01). While in Group 3 an augmentation of 0.7 g.dl-1 haemoglobin resulted in restoring baseline tissue oxygenation, higher doses of 2.7 g.dl-1 and 2.1 g.dl-1 were needed in Groups 1 and 2 to reach this level (P < 0.01).

CONCLUSION

The results show a higher oxygenation potential of HBOC than with autologous stored red cells because of a more pronounced oxygen extraction.

Propofol reduces emesis after sufentanil supplemented anaesthesia in paediatric squint surgery

BACKGROUND

Squint surgery is associated with a high incidence of postoperative emesis. The purpose of this prospective study was to examine the influence of propofol and isoflurane anaesthesia on the incidence of postoperative nausea and vomiting in children.

METHODS

Ninety children aged 3-10 years were randomly allocated to one of 3 groups. In all groups, children received 2 mg/kg propofol, 0.5 microgram/kg sufentanil and 0.5 mg/kg atracurium for induction of anaesthesia. In group 1, anaesthesia was maintained with 15-20 mg/kg.h propofol and children were ventilated with 30% O2 in air. In group 2, anaesthesia was maintained with 10-15 mg/kg.h propofol and 30% O2 in N2O. In group 3, anaesthesia was maintained with 1.0-1.5 Vol% isoflurane and 30% O2 in N2O. The time of extubation, awakening and postoperative surveillance, the incidence and numbers of episodes of postoperative nausea and vomiting were registered as well as requirements of antiemetics. Statistics were made using ANOVA and Chi-square test or Kruskal-Wallis test with P < 0.05 considered as significant.

RESULTS

The overall incidence of nausea (P = 0.0001) and vomiting (P = 0.002) was higher in group 3 (70%;73%) than in group 1 (13%;23%) and 2 (20%;28%). Episodes of nausea (P = 0.0001) and vomiting (P = 0.0013) were more frequent in group 3 (74%;69%) than in group 1 (13%;15%) and 2 (13%;16%). Antiemetic requirements were higher and the time of postoperative sleep and surveillance was longer in group 3 than in group 1 and 2 (P = 0.04).

CONCLUSION

Propofol-sufentanil anaesthesia results in less emesis and treatment during the early postoperative phase irrespective of N2O administration compared with propofol-induced isoflurane anaesthesia and may be recommended in children undergoing squint surgery.

[Arthrogryposis multiplex congenita: special anesthesiological aspects]

Case report on a 2.5-year old girl suffering from arthrogryposis multiplex congenita (AMC) who was admitted for an extensive orthopaedic operation of equinovarus. The patient showed typical AMC-related problems such as skin and subcutaneous tissue abnormalities, lack of veins, contractural deformities of all four limbs and microgenia. Problems associated with anaesthesia in this patient were difficult intubation and venipuncture and a potential risk of developing malignant hyperthermia when using volatile anaesthetics. For preoperative blood chemistry sampling and intravenous induction of general anaesthesia, the patient received a central venous catheter under local and N2O/O2 anaesthesia on the day before surgery. Following intravenous induction of trigger-free anaesthesia using fentanyl, thiopental and vecuronium, the child was intubated and ventilated with 30% O2 in N2O the next day. A caudal catheter was inserted for intraoperative reduction of anaesthetics and postoperative pain relief. Intraoperatively, caudal anaesthesia was performed with 2 ml of 2% mepivacaine every 90 min. No inadvertent reactions were seen during a 7 h operation. In the recovery room, the patient received 4 ml of plain 0.25% bupivacaine per 4 h via the caudal catheter and had excellent analgesia during 24 postoperative hours. The following course was uneventful and the child was discharged from hospital two weeks later. AMC-related problems concerning the management of anaesthesia are discussed.

Postoperative complaints after spinal and thiopentone-isoflurane anaesthesia in patients undergoing orthopaedic surgery. Spinal versus general anaesthesia

BACKGROUND

The present prospective study investigates the impact of a standardized technique of spinal and general anaesthesia on the incidence and consequences of postanaesthetic complaints dependent on age and sex of patients.

METHODS

433 orthopaedic patients underwent lower limb surgery in spinal (group 1) or general (group 2) anaesthesia. Spinal anaesthesia was performed with 0.5% hyperbaric bupivacaine using a 26-gauge Quincke needle. General anaesthesia was induced with i.v. injection of thiopentone, fentanyl and atracurium and maintained with 65% nitrous oxide and 1-1.5 Vol% isoflurane in oxygen. On postoperative day 4, patients were interviewed for onset and duration of postoperative complaints.

RESULTS

The overall incidence of nausea/vomiting (P = 0.025) and sore throat (P = 0.0001) was higher in group 2. In addition, nausea/vomiting was higher in patients between 20 and 60 years in group 2 compared with group 1. While the incidence of urinary dysfunction was higher in men after spinal (P = 0.04), nausea/vomiting was more frequent in women after general anaesthesia (P = 0.008). Analgetic requirements (P = 0.013), time of postoperative surveillance (P = 0.042) and frequency of treatment of postoperative complaints (P = 0.0001) was higher in group 2.

CONCLUSION

Spinal anaesthesia was associated with a lower incidence of postoperative complaints and treatments and a shorter surveillance compared to general anaesthesia. Specific complications related to spinal anaesthesia did not depend on age or sex and may allow for recommendation of this technique even in younger and female patients undergoing orthopaedic surgery.

[The effect of puncture needle on the subarachnoid catheter position in continuous spinal ansthesia]

The subarachnoid position of the microcatheter has an impact on the outcome of continuous spinal anaesthesia (CSA). The present prospective, randomised study investigated the influence of two different spinal needles on the radiographically documented subarachnoid positions of microcatheters in CSA. In addition, the influence of the subarachnoid position of the microcatheter on onset time of analgesia, dose requirement of local anaesthetics, and level of analgesia was examined. METHODS. Forty orthopaedic patients received CSA using a 28-gauge spinal catheter inserted either through a non-directional 22-gauge Quincke needle (group 1) or a directional 22-gauge Sprotte needle (group 2). After initial injection of 2 ml to a maximum of 5 ml of supplemental doses of 0.5% plain bupivacaine, onset time of analgesia at the level of T 10, dose requirement of bupivacaine, and the achieved analgesic level were registered. After surgery, a dye-enhanced AP X-ray film of the lumbar spine was performed for radiological control of the subarachnoid catheter position. RESULTS. There was a higher number of cranial catheter positions in group 2 (60%) compared with group 1 (40%, P = 0.037). In contrast to group 1, with 35% caudally directed catheters, no catheter was seen in a caudal position in group 2. Onset time of analgesia (P = 0.0002) and anaesthetic dose requirement (P = 0.037) were lower in patients with cranially directed catheters compared to patients with the catheters situated at the level of the puncture site or in a caudal position. Maximal analgesic levels were higher in cranially directed catheters compared with other localisations (P = 0.022). CONCLUSIONS. Sprotte needles provide a higher number of cranially directed microcatheters, which are associated with faster onset of analgesia, lower dose requirement of local anaesthetics, and higher analgesic levels in CSA. The results suggest more effectiveness and probably more safety in microcatheter CSA using Sprotte needles for catheter insertion.

A directional needle improves effectiveness and reduces complications of microcatheter continuous spinal anaesthesia

The present prospective randomized study compares the impact of two different spinal needle designs--non-directional versus directional--on the effectiveness of continuous spinal anaesthesia provided via a microcatheter in orthopaedic patients. Using the midline approach, a 28-gauge spinal catheter was inserted either through a 22-gauge Quincke needle (non-directional, Group 1, n = 21) or a 22-gauge Sprotte needle (directional, Group 2, n = 21) under standardized conditions. The incidence of technical difficulties and postoperative complaints, onset time of analgesia at the level of T10 and dose requirement of plain bupivacaine 0.5% were recorded. Postoperatively, the subarachnoid position of the catheters was radiographically evaluated. There was a higher incidence of technical problems during catheter insertion in Group 1 compared with Group 2 (71% vs 19%, P < 0.05). Onset time of analgesia was shorter (P < 0.05) and anaesthetic dose requirement was lower in patients in Group 2 than in Group 1. While 40% of the catheters were found in a caudal position in Group 1, all catheters were in a cranial position or at the level of the puncture site in Group 2 (P < 0.05). There was no difference in the incidence of postoperative complaints between the groups. The faster onset of analgesia and lower dose requirement of local anaesthetics associated with a lower incidence of technical problems suggest that there is greater effectiveness and safety when microcatheters are inserted using directional needles rather than non-directional needles.

[Propofol-alfentanil reduced cerebrovascular CO2 reactivity in comparison with isoflurane]

The present study compared the effects of propofol/alfentanil versus isoflurane anaesthesia on cerebral vascular reactivity to changes in carbon dioxide (CO2) using transcranial Doppler sonography (TCD). METHODS. Seventeen ASA class I patients undergoing minor elective surgery were studied following IRB approval and informed consent. In group 1 (n = 10), anaesthesia was induced with thiopental 4 mg/kg and alfentanil 15 micrograms/kg. Endotracheal intubation was facilitated by vecuronium 0.1 mg/kg. Anaesthesia was maintained with 1% end-tidal isoflurane and nitrous oxide (N2O) in oxygen O2 (6 l/min; FiO2 0.3). In group 2 (n = 7), anaesthesia was induced with propofol 2 mg/kg, alfentanil 15 micrograms/kg, and vecuronium 0.1 mg/kg for endotracheal intubation and maintained by infusion of propofol, alfentanil, and N2O-O2 (6 l/min; FiO2 0.3) according to the following protocol: propofol: 10, 8, and 6 mg/kg.h for 10 min each followed by 4 mg/kg.h; alfentanil: 55 micrograms/kg.h. Monitoring included measurement of mean arterial blood pressure (MAP, mm Hg), heart rate (HR), body temperature (T), end-tidal CO2 (PetCO2, mm Hg), isoflurane concentrations, and arterial O2 saturation (SaO2, %). Mean blood flow velocity (Vmean, cm/s) was measured in the middle cerebral artery using a bidirectional 2-MHz TCD system (TranspectT, Medasonics). Mechanical ventilation was adjusted to achieve PetCO2 levels of 40-50-40-30 and 40 mm Hg. Ten minutes of equilibration were allowed at each PetCO2 level. The CO2 reactivity index was calculated as delta Vmean/delta PetCO2 (cm/s.mm Hg). RESULTS. MAP, HR, T, and SaO2 were constant over time and were not different between groups. The CO2 reactivity index over the CO2 range of 30-50 mm Hg was higher in isoflurane (2.32 +/- 1.51 delta cm/s.mm Hg) compared to propofol/alfentanil patients (1.15 +/- 0.77 delta cm/s.mm Hg) (mean +/- SD, P < 0.05). CONCLUSIONS. The data show that although CO2 reactivity is maintained during both isoflurane and propofol/alfentanil anaesthesia, the cerebral vascular response to CO2 was lower in propofol/alfentanil compared to isoflurane patients. This is likely due to propofol/alfentanil-induced cerebral vasoconstriction. These data suggest that CO2 reactivity is a function of the pre-existing cerebral vascular tone induced by the anaesthetic.

Microcatheter continuous spinal anaesthesia in the post-operative period: a prospective study of its effectiveness and complications

One hundred patients (aged 22-86 years, mean 62.5), undergoing lower limb orthopaedic surgery, received continuous spinal anaesthesia using a 28 s.w.g. catheter inserted through a 22 s.w.g. Quincke needle. Post-operative pain relief was provided by bolus injections of 1-2.5 mL 4 h-1 of plain 0.25% bupivacaine. The mean dose of bupivacaine required for sufficient pain relief in 93% of patients was 1.6 +/- 0.2 (1.3-1.9) mL 4 h-1. The highest dose was needed between 4 and 8 h post-operatively. No dependence of dose on age or type of operation was found. Technical problems with the microcatheter occurred in 12%. The most frequent complaint was post-operative backache (12%). Only one patient suffered from post-dural puncture headache on the day after surgery. There was no microbiological contamination of the catheter tips after removal. In the post-operative interview, 89% of the patients were completely satisfied with CSA; 91% would prefer this technique to general anaesthesia.

Influence of the subarachnoid position of microcatheters on onset of analgesia and dose of plain bupivacaine 0.5% in continuous spinal anesthesia

BACKGROUND AND OBJECTIVES

Many factors have an impact on the outcome of continuous spinal anesthesia (CSA) with small-bore catheters. Recent publications of neurologic complications after CSA suggest that the local anesthetic as well as the microspinal catheter influence the analgesic effect in CSA. This prospective study was designed to evaluate the influence of the subarachnoid position of 28-gauge spinal catheters on the speed of onset of analgesia and on the dose of plain bupivacaine 0.5% required for a block at the level of T-10 in CSA.

METHODS

Sixty-eight patients (mean age 61.7 +/- 6.4 years) received CSA using a 22-gauge Quincke needle (Kendall, Mansfield, MA) and a 28-gauge spinal catheter. After initial injection of 2.5 mL (minimum) up to a maximum of 5 mL of supplemental doses of plain bupivacaine 0.5%, the time of onset of analgesia at the level of T-10 and the dose of local anesthetics required for this block were determined. The subarachnoid catheter position was examined radiographically by a dye supported conventional anteroposterior roentgenogram of the lumbar spine on the first day after the operation.

RESULTS

The onset time of analgesia and the dose of plain bupivacaine 0.5% required for the block at the level of T-10 were significantly dependent on the subarachnoid position of the microcatheters (P < .01), but not on the level of the lumbar dural puncture (P = .29, P = .69). In patients with cranially running catheters or catheters with the tip at the level of the puncture site, analgesia onset was faster and required doses of bupivacaine were smaller than in patients with caudally running catheters.

CONCLUSIONS

The subarachnoid position of a 28-gauge microcatheter is an important factor with regard to the effectiveness (e.g., onset time of analgesia and dose requirement) of CSA using plain bupivacaine 0.5%.

Radiological examination of the intrathecal position of microcatheters in continuous spinal anaesthesia

There have been few studies of the intrathecal position of spinal catheters in continuous spinal anaesthesia. This prospective study was designed to examine radiologically the intrathecal position of 28-gauge spinal catheters. We studied the entry into the subarachnoid space and the intrathecal position of 68 spinal catheters. In 50%, the catheters passed in a cranial direction, in 34% the catheters remained at the level of the puncture site and in 16% the catheters were directed caudally. The intrathecal position of the catheters did not depend on the level of the lumbar puncture (P = 0.6246), but was dependent on the position of the patient during insertion of the catheter (P = 0.0093), and on the depth of insertion (P = 0.0099). Our study suggests that patients should be in a sitting position during insertion of a subarachnoid microcatheter and that the depth of insertion should not exceed 4 cm.

Technical problems with 32-gauge microcatheters in continuous spinal anaesthesia

Technical problems with microspinal catheters for continuous spinal anaesthesia (CSA) are not unknown. The present case report deals with two unusual technical complications in CSA with 32-gauge spinal catheters. The first case shows a catheter with extraordinary elongation due to breakage of the embedded stylet. The second case shows a tear in the extracorporeal part of the catheter with leakage of the local anaesthetic and consequently failed spinal anaesthesia.