Single-dose spinal anaesthesia versus incremental dosing for lower limb vascular surgery.

BACKGROUND: In patients scheduled for vascular surgery, atherosclerotic disease is highly prevalent. Haemodynamic reactions are often aggravated when spinal analgesia is used in this population. No randomized studies have been conducted comparing single shot (SS) with continuous spinal analgesia (CSA) for vascular patients. We did a prospective randomized study comparing haemodynamics when SS versus CSA was performed. METHODS: Sixty patients were randomized to have SS or CSA. The power of the study was 0.90. Patients in the SS group received 17.5 mg bupivacaine and in the CSA group 5 mg was given initially and incremental doses of 2.5 mg were given until an analgesic level of T-11 was reached. Mean arterial pressures (MAP) were measured invasively. ST-analysis was done continuously. Postoperatively, the patients were interviewed using a standardized questionnaire. Back pain, neurologic sequelae and post-dural puncture headache (PDPH) were investigated. RESULTS: There was no significant difference between the analgesic levels (T-7/T-8), the decrease in MAP, the number of patients needing ephedrine and the total amount of ephedrine given in the two groups. The motor blockade was more pronounced in the SS group (P < 0.001) and the total amount of bupivacaine used was 17.5 mg compared to 7.5 mg (5-17.5) in the CSA group (P < 0.001). One patient suffered PDPH which was slight and responded to a nonsteroidal anti-inflammatory drug. Two patients in each group had transient paraesthesias in the legs. There were technical problems with the spinal catheter in 4 patients, and these were excluded from the study. CONCLUSION: In this study we found no difference in the haemodynamic response to SS or CSA in patients scheduled for vascular surgery of the legs. SS is easier to apply and is recommended when the duration of surgery allows for it.

[Perioperative salvage and use of autologous blood]. / Perioperativ opsamling og brug af autologt blod.

Pre-operative blood donation gives ready availability of large volumes of patient compatible blood, up to four units and five when erythropoietin is used. It is recommended that autologous pre-donated blood is leucocyte depleted immediately after the donation. During normovolaemic haemodilution it is mandatory to monitor haemodynamics during the donation. Usually 1-2 units are removed pre-operatively and returned during or after the operation. Intra and postoperative salvage and recycling is performed either with washing and haemoconcentration of the blood or with salvage and immediate retransfusion. When salvaged blood is retransfused unwashed there are high levels of free haemoglobin, degradation products of fibrin/fibrinogen, interleukin-6 and activated complement. Clinically, this has not been shown to be of importance. Taking the patient's health status into account, we suggest that a level of B-haemoglobin should be determined pre-operatively to indicate use of transfusions both with autologous and allogeneic blood.

[Atraucan, a new needle for spinal analgesia]. / Atraucan, en ny kanyle til spinal analgesi.

One hundred and six consecutive patients, aged below 40 years, scheduled for surgery in the lower part of the body were chosen for this study. Patients were allocated randomly to have spinal analgesia with either a Sprotte 24G or an Atraucan 26G spinal needle. Incidences of insufficient blocks were higher after dural puncture with the Atraucan needle. Nineteen patients reported post dural puncture headache (PDPH) with a significantly higher proportion in the Atraucan group (two patients suffered mild (4%) and 14 severe (98%) PDPH) compared to the Sprotte group (three patients suffered mild (6%) PDPH. Eight patients (16%), all in the Atraucan group, required an epidural blood patch. Ease of needle insertion and number of puncture attempts were the same for both needles. We conclude that due to the high incidence of PDPH the Atraucan 26G spinal needle cannot be recommended for spinal analgesia in young patients.

[Solcotrans, a new autotransfusion system]. / Solcotrans, et nyt autotransfusionssystem.

Thirty-one patients scheduled to undergo aortic reconstruction were studied. 16 had aortic aneurysms and 15 required aortobifemoral grafts. The solcotrans unit comprises a rigid plastic container with an inner lining bag, into which blood is aspirated. When the bag is full (500 ml), the unit is inverted and blood is re-infused through a 40 micron filter. Sixty-three percent of the blood transfused per-operatively and 41% peri-operatively was given with the solcotrans unit. Only minor changes in the coagulation parameters were seen. Blood cultures from ten solcotrans units were all negative. Two patients contracted pneumonia, and one cystitis. We conclude that the solcotrans system is safe to use when two-to four units of blood are transfused. Further studies are required to define its role when multitransfusions of blood are needed.

[24 G Sprotte spinal cannula for anesthesia in young patients]. / Sprotte's 24 G spinalkanyle til anaestesi af yngre patienter.

We studied 75 patients aged 15-40 years who received spinal anaesthesia with the Sprotte 24-gauge spinal needle. The incidence of post dural puncture headache was 4%. Other types of headache occurred in 8% of the patients. The patient acceptance was high. We conclude that spinal anaesthesia is easy to perform with a 24-gauge Sprotte needle and is associated with a low incidence of post dural puncture headache.

Flexible fibreoptic bronchoscopy via the laryngeal mask.

The efficacy of flexible fibreoptic bronchoscopy through the laryngeal mask was investigated in 20 patients under total intravenous anaesthesia with propofol, fentanyl, atropine and suxamethonium. Mask size 4 was used for men and size 3 for women. Ventilation was performed with oxygen in air, FIO2 0.6. The ventilatory pressures were median 18 (9-40) cmH2O (1.8 (0.9-3.9) kPa) before the bronchoscope was inserted. When the tip of the bronchoscope was above the vocal cords the ventilatory pressures increased to 22 (10-43) mmHg (2.2 (1.0-4.2) kPa) (P < 0.001), and when the tip was situated at the mid-tracheal level there was a further increase to 24 (12-50) mmHg (2.4 (1.2-4.9) kPa) (P < 0.001). Maximal gas leakages were median 1 (0-2) l/min-1. PEEP at the mid-tracheal level was 3 (0-7) cmH2O (0.3(0-0.7) kPa). When 15 min of the procedure had elapsed, PaO2 was 232 (112-350) mmHg (30.9 (14.9-46.6) kPa) and PaCO2 39 (33-46) mmHg (5.2(4.4-6.1) kPa). The lowest oxygen saturation was median 98 (96-100)% and the highest end-tidal CO2 34 (24-41) mmHg (4.5(3.2-5.5) kPa). It was easy to examine the laryngeal opening and a good assessment of vocal cord function was allowed when muscle relaxation ceased. We conclude that flexible fibreoptic bronchoscopy through the laryngeal mask is a safe technique provided that total intravenous anaesthesia is used. It is a valuable alternative to flexible bronchoscopy performed with topical anaesthesia.

Intramuscular low-dose ketamine versus pethidine for postoperative pain treatment after thoracic surgery.

In a double-blind prospective study the effects of low-dose intramuscular ketamine (1 mg/kg) were compared to pethidine (1 mg/kg) in the treatment of pain after pulmonary surgery. Thirty patients were admitted to the study and postoperatively randomized to either a ketamine or a pethidine group. The analgesic effect was evaluated using a scale ranging from 0 to 10, where 0 denoted no pain and 10 severe pain. We did not find any significant difference between the analgesic effect of ketamine and pethidine; however, the duration of action of ketamine appeared to be slightly longer. Throughout the study PaCO2 was significantly lower in the ketamine group. PaO2 increased through the study in both groups and was significantly higher after 2 h. Heart rates increased significantly only in the pethidine group. Mean arterial pressures remained unchanged and the respiratory frequencies were similar in the two groups. The incidence of adverse reactions was low and not significantly different between the groups. The findings indicate that low-dose intramuscular ketamine is a potent analgesic for postoperative analgesia following thoracic surgery and that it has no respiratory depressive effect.

Comparative plasma concentration profiles after i.v., i.m. and rectal administration of pethidine in children.

Plasma concentration-time curves of pethidine and norpethidine were studied in 25 children allocated after operation to three groups to receive pethidine 1 mg kg-1 i.v., i.m. or rectally. Peak concentrations occurred after 5 +/- 1, 10 +/- 2, and 60 +/- 10 min, respectively, while the maximum concentrations amounted to 2800 +/- 462, 1609 +/- 367 and 531 +/- 179 nmol litre-1, respectively. The area under the curve (0-240 min) was similarly reduced in the group with rectal administration (P less than 0.05). Compared with the i.v. data, approximately 40% systemic availability occurred after rectal application, although considerable individual variation was noted. In one child very high plasma concentrations were observed after rectal administration, possibly as a result of redistribution/recirculation phenomena. The average results are similar to those obtained when other opioids are given rectally.

Respiratory function and carbonic anhydrase inhibition.

Acetazolamide (Diamox) induced carbonic anhydrase inhibition is an efficient means of eliminating surplus water and bicarbonate in the overhydrated and alkalotic patient. Previous studies have demonstrated an unexpected and unexplained increase in arterial and venous oxygenation during acute carbonic anhydrase inhibition. In the present investigation we assessed the effect of acetazolamide 15 mg kg-1 on pulmonary gas exchange in 10 critically ill, mechanically ventilated patients. Median arterial oxygen tension increased by 0.9 kPa and central venous oxygen tension and content by 16-18% and 6-8% respectively. The improved oxygenation could, however, not be attributed to an improved pulmonary oxygen exchange as both pulmonary venous admixture (Qs Qt-1) and physiological dead space ventilation (VD VT-1) increased. The increase in arterial oxygen tension can be explained by a rightward shift of the oxyhemoglobin dissociation curve due to the increased acidity of the blood during carbonic anhydrase inhibition (Bohr effect). Acetazolamide does not depress oxygen consumption, so the increase in central venous oxygen content probably reflects an improved cardiac performance. This could conceivably be mediated via sympathetic activation in response to acetazolamide induced carbon dioxide retention.

Submandibular salivary secretion in the cat and associated potassium movements: dependence on temperature and perfusate flow rate.

Cat submandibular glands were perfused with Locke solution in a thermostated chamber and intermittently stimulated with 10(-5)M acetylcholine (ACh). In one series of experiments the perfusion pressure was varied within the range 90-60 mm Hg, and secretory flow rate, active K+-reuptake, passive K+-release, and resting and ACh-induced venous flow rates were measured. The ACh-induced secretory flow rate and the maximal K+-fluxes were related to the simultaneous ACh-induced venous flow rates. A proportionality was found between the maximal rate of ACh-induced K+-release and ACh-induced venous flow rates below 8 ml/min, while at higher flow rates the K+-release leveled off. The maximal rate of the post-stimulatory K+-reuptake increased proportionally to the ACh-induced perfusate flow rate throughout the range studied. The secretory flow rate was much less affected by changes in ACh-induced perfusate flow rate. In another series of experiments the gland temperature was varied within the range 12-37 degrees C, and the same parameters were measured. All parameters decreased with cooling being reduced to 50% of their 37 degrees C values at: 24 degrees C for secretion, 19 degrees C for K+-reuptake, and 14 degrees C for K+-release. It is concluded: that the rate of ACh-induced K+-release is limited by the ACh-induced perfusate flow rate (within the physiological range), the capacity of the K+-reuptake mechanism is at least one order of magnitude larger than the maximal rate of K+-reuptake in vivo, the marked temperature sensitivity of the secretory flow rate reflects the high complexity of the mechanisms involved.