Summary

The history of intrathecal and epidural anaesthesia is in parallel with the development of general anaesthesia. As ether anaesthesia (1846) is considered the first modern anaesthetic since its use by Morton 157 yr ago, so Bier made history by using cocaine for intrathecal anaesthesia in 1898. The first published report on opioids for intrathecal anaesthesia belongs to a Romanian surgeon, Racoviceanu-Pitesti, who presented his experience at Paris in 1901. It was almost a century before the opioids were used for epidural analgesia. Behar and his colleagues published the first report on the epidural use of morphine for the treatment of pain in The Lancet in 1979. Epidural and intrathecal opioids are today part of a routine regimen for intra- and postoperative analgesia. Over the last 30 yr, the use of epidural opioids has became a standard for analgesia in labour and delivery, and for the management of chronic pain. Finally, epidural opioids have been shown to have a pre-emptive effect, when used before major surgery. We present the evolution of neuraxial anaesthesia and the history of intrathecal and epidural administration of opioids.

Summary

Background and objective: An inverse I : E ratio (inspiratory time > expiratory time) may have benefits in patients suffering trauma who requiring lung ventilation. However, this application may be deleterious if there is concomitant head injury. We aimed to determine the physiological effects of pressure- and volume-controlled modes of inverse ratio (I : E = 2 : 1) ventilation of the lungs, while maintaining normocapnia, in a rabbit model of raised intracranial pressure (ICP).

Methods: New Zealand White rabbits were anaesthetized with isoflurane and a tracheostomy was performed. Subarachnoid haemorrhage was simulated in two groups by injecting blood into the cisterna magna. Groups 1 and 2 (n = 6, each), controls, were compared with Groups 3 and 4 (n = 6, each) with the simulated subarachnoid haemorrhage. Each ventilation mode was used with an I : E ratio of 2 : 1 for 30 min. Mean arterial pressure (MAP), ICP, cerebral perfusion pressure (CPP), mean airway pressure (PAW) and arterial blood-gas status were measured.

Results: Both modes increased mean PAW (P < 0.02). This increase was greater with the volume-controlled mode (P < 0.02). The baseline value averaged 5.8 ± 0.4 and 5.6 ± 0.3 mmHg in Groups 3 and 4, respectively, and increased to 7.8 ± 0.3 and 10.8 ± 0.4 mmHg. Inducing subarachnoid haemorrhage increased ICP and MAP (P < 0.02). Baseline ICPs were 10.3 ± 0.5 and 10.3 ± 0.4 mmHg in Groups 1 and 2, respectively, whereas they were 25.4 ± 1.2 and 25.8 ± 0.8 mmHg in Groups 3 and 4. However, ICP, MAP and CPP did not differ significantly according to the mode.

Conclusions: An already raised ICP was altered by the application of induced mean PAW increases as a consequence of inverse ratio ventilation of the lungs with normocapnia.

Summary

Background and objective: We set out to compare the efficacy of clevidipine and sodium nitroprusside infusions in the control of blood pressure and the haemodynamic changes they produce in hypertensive patients after operation for elective coronary bypass grafting.

Methods: Thirty patients were randomly allocated to receive either clevidipine or sodium nitroprusside after their mean arterial pressure (MAP) had reached >90 mmHg for at least 10 min in the postoperative period. The MAP was continuously measured and related to time. Thus, the efficacy of the drugs in controlling arterial pressure could be inversely related to the total area under the MAP–time curve outside a target MAP range of 70–80 mmHg normalized per hour (AUCMAP mmHg min h−1). Haemodynamic variables and the number of dose-rate adjustments required to maintain MAP were also studied.

Results: There was no statistically significant difference in the efficacy (AUCMAP mmHg min h−1) of clevidipine (106 ± 25 mmHg min h−1) compared with sodium nitroprusside (101 ± 28 mmHg min h−1). Nor was any significant difference found in the total number of dose adjustments required to control MAP within the target range. The heart rate in patients receiving clevidipine increased less than in those given sodium nitroprusside. Stroke volume, central venous pressure and pulmonary artery pressure were significantly reduced upon administration of sodium nitroprusside but not of clevidipine.

Conclusions: There was no significant difference between clevidipine and sodium nitroprusside in their efficacy in controlling MAP. The haemodynamic changes, including tachycardia, were less pronounced with clevidipine than with sodium nitroprusside.

Summary

Background and objective: This prospective, randomized, controlled study evaluated the effects on oxygenation by applying a selective and patient-specific value of positive end-expiratory pressure (PEEP) to the dependent lung during one-lung ventilation.

Methods: Fifty patients undergoing thoracic surgery under combined epidural/general anaesthesia were randomly allocated to receive zero PEEP (Group ZEEP, n = 22), or the preventive application of PEEP, optimized on the best thoracopulmonary compliance (Group PEEP, n = 28). Patients' lungs were mechanically ventilated with the same setting during two- and one-lung ventilation (FiO2 = 0.5; VT = 9 mL kg−1, inspiratory : expiratory time = 1 : 1, inspiratory pause = 10%).

Results: Lung-chest wall compliance decreased in both groups during one-lung ventilation, but patients of Group PEEP had 10% higher values than patients with no end-expiratory pressure (ZEEP) applied – Group ZEEP (P < 0.05). During closed chest one-lung ventilation, the PaO2 : FiO2 ratio was lower in Group PEEP (232 ± 88) than in Group ZEEP (339 ± 97) (P < 0.05); but no further differences were reported throughout the study. No differences were reported between the two groups in the need for 100% oxygen ventilation (10 patients of Group ZEEP (45%) and 14 patients of Group PEEP (50%) (P = 0.78)) or re-inflation of the operated lung during surgery (two patients of Group ZEEP (9%) and three patients of Group PEEP (10%) (P = 0.78)). Postanaesthesia care unit discharge required 48 min (25th–75th percentiles: 32–58 min) in Group PEEP and 45 min (30–57 min) in Group ZEEP (P = 0.60).

Conclusions: The selective application of PEEP to the dependent, non-operated lung increases the lung–chest wall compliance during one-lung ventilation, but does not improve patient oxygenation.

Summary

Background and objective: Our hypothesis was that fenoldopam, a selective DA1 agonist, would protect against rhabdomyolysis-induced renal injury.

Methods: We studied the effects of intravenous fenoldopam (0.1–1.0 μg kg−1 min−1) or saline on renal blood flow and function in 10 anaesthetized Labrador dogs in whom rhabdomyolysis and myoglobinuric acute renal failure had been induced by administration of glycerol 50% (10 mL kg−1) intramuscularly. Haemodynamic measurements including renal blood flow and derived parameters of renal function including creatinine clearance were recorded before and for the 30 min following glycerol injection, and during the 3 h following commencement of each infusion. Serum malondialdehyde concentrations were measured before and 15 min after glycerol intramuscularly, and 30 and 150 min after commencement of the infusion.

Results: In the fenoldopam group, creatinine clearance was less than placebo at 1 and 2 h after commencing the infusion (12.7 ± 11.5 versus 31.3 ± 9.9 mL min−1, P = 0.04; 8.5 ± 5.3 versus 20.1 ± 7.4 mL min−1, P = 0.03). A 140-fold increase in serum malondialdehyde concentration occurred in one dog (fenoldopam group).

Conclusion: Fenoldopam increased the severity of the renal injury in this canine model of myoglobinuric acute renal failure.

Summary

Background and objective: Patients who require multidisciplinary intensive care after cardiac surgery have a poor prognosis. The aim was to investigate factors in the mortality of this group of patients at 6 months.

Methods: A retrospective analysis was made of the 6-month mortality rate in 301 adults who required admission to a multidisciplinary intensive care unit following cardiac surgery from 1991 to 1997. Mortality was correlated with clinical and patient characteristic variables.

Results: The intensive care mortality rate was 34% and at 6 months after patients' discharge from intensive care it was 51%. There were positive correlations with death at 6 months for ventricular failure (odds ratio of death 3.4, P = 0.002), sepsis (odds ratio 3.0, P = 0.004) and age over 80 yr (odds ratio of death 9.2, P = 0.034). Patients who had undergone isolated coronary artery graft surgery (odds ratio of death 0.28, P = 0.036) or thoracic surgery (odds ratio of death 0.22, P = 0.042) had better 6-month outcomes. Patients with respiratory or renal failure in the absence of ventricular failure or sepsis had a 6-month mortality rate of 36%; but the lower mortality rate did not achieve statistical significance.

Conclusions: The 6-month mortality rate of 51% in a group of patients requiring multidisciplinary intensive care after cardiac surgery is consistent with previous studies; mortality was particularly high in extreme old age and in patients referred with sepsis or ventricular failure. Those patients with uncomplicated respiratory or renal failure had a better outcome than the group as a whole.

Summary

Background and objective: Previous work in our department, prior to the advent of digital subtraction angiography, showed that anaesthetist-administered sedation for cerebral angiography using propofol infusion–bolus fentanyl resulted in significantly more patients with early recall than a bolus fentanyl and midazolam technique. Our present study reassessed, 10 yr after our original study, the effectiveness of sedation for neuroradiological digital subtraction cerebral angiography, using three techniques currently in use in the department.

Methods: A total of 88 adult patients were sedated for neuroradiological angiograms by one of three anaesthetist-administered regimens: propofol–alfentanil infusion; boluses of fentanyl with a propofol infusion and boluses of fentanyl and midazolam. The latter two regimens had been used in our previous sedation study. Patients were assessed for time to orientation at the completion of the procedure, and followed up the next day to determine their last memory before sedation, first memory after the angiogram and any recall of the procedure itself.

Results: All three techniques were found to give satisfactory sedation and showed minimal difference in the time to orientation at the end of the procedure (3.7, 4.3 and 5.1 min), any awareness of the procedure itself (20% of patients overall) and numbers of patients having early recall; that is, recall of still being in the radiology department before return to the ward (22/29, 16/29 and 20/30).

Conclusions: Our results show that since the introduction of digital subtraction angiography we may have a different end-point of sedation compared to our original study, as well as a shorter angiogram time. Satisfactory anaesthetist-administered sedation can be provided for cerebral angiography by either infusion or incremental techniques. We feel that the success and safety of a sedation technique depends considerably on the skill and experience of the administrator such that these sedation techniques are only suitable for safe use by an anaesthetist.

Summary

Background and objective: Intubation of the trachea has been a risky cross-contamination procedure over the past decade because no perfect decontamination procedures exist. Infectious agents found on laryngoscopic devices have the potential for devastating spread of the human immunodeficiency virus, hepatitis viruses B and C and transmissible non-conventional agents. The purpose of this prospective observational study was to assess the quality of endotracheal intubation with disposable laryngoscope blades, under normal intubating conditions.

Methods: Anaesthetists were asked to complete daily questionnaires regarding the difficulty of intubation experienced using the Vital View® disposable laryngoscope blade (Vital Signs Inc, Totowa, NC, USA). The choice of the type of blade (conventional or disposable blade) for the first attempt at intubation depended only on the operating room assignment. Glottic visualization during laryngoscopy was assessed by the modified Cormack and Lehane classification. Difficult tracheal intubation was evaluated by the intubation difficulty scale (>5, procedure involving moderate to major difficulty).

Results: The anaesthetic staff recorded 219 intubations. One hundred-and-nineteen of first attempts at laryngoscopy were with disposable blades (DB group) and another 100 with conventional blades (CB group). There were no significant differences between the two groups for Cormack and Lehane score 3, for intubation difficulty scale scores >5 and for intubation difficulty scale score 0. There were 12 blade changes before successful intubation.

Conclusions: In routine use, the Vital View® disposable laryngoscope blade appears to be an efficient device because it does not modify the ease of endotracheal intubation in most cases. Nonetheless, it may be advisable to maintain conventional laryngoscopes in reserve for difficult intubations.

Summary

Background and objective: Spinal cord stimulation has been used successfully for many years in the management of neuropathic pain. Nociceptive pathways are closely integrated into many autonomic reflexes. The aim was to test the hypothesis that pain relief caused by spinal cord stimulation is related to changes in peripheral skin blood flow.

Methods: Twelve patients with spinal cord stimulators implanted as a treatment for neuropathic pain were entered into the study. Laser Doppler perfusion scanning was used as a direct method for selective measurement of changes in skin (peripheral) blood flow. Measurements were taken before and after the onset of spinal cord stimulation over the site of its sensory projection. The degree of pain relief due to spinal cord stimulation and the skin temperature of each patient were also recorded.

Results: Apart from one patient, spinal cord stimulation did not change skin blood flow in a statistically significant manner.

Conclusions: Pain relief due to spinal cord stimulation is not related to changes of skin blood flow.

Summary

Background and objective: This study investigated the distribution of pressures within a model trachea, produced by five different tracheal gas insufflation devices. The aim was to suggest a suitable design of a tracheal gas insufflation device for clinical use.

Methods: Each device was tested using insufflation flow rates of 5 and 10 L min−1. For each flow rate, the pressure within the tracheal model was measured at 33 fixed points.

Results: The Boussignac tracheal tube produced the most even pressure distribution, while a reverse-flow catheter produced pressure changes of the smallest magnitude.

Conclusions: We suggest that catheters producing the lowest pressure changes are likely to be safer for clinical use.

Summary

Background and objective: The visual analogue scale (VAS) is considered as the gold standard method for postoperative pain assessment. Nevertheless, in some clinical situations, this method may not be reliable. We performed an observational study to assess the use of the VAS and other pain scales by nurses in the postanaesthesia care unit.

Methods: We studied the reasons for not using the VAS and asked if it may be less appropriate in certain age groups.

Results: Among 600 patients included in the study (16% = 70 yr), nurses used the VAS in 53%, the numerical rating scale in 30%, the verbal rating scale in 12% and the behavioural scale in 5%. In 43% of the assessments, nursed did not use the VAS; the most frequently cited reason was related to their preference for other methods. In 54% of the assessments, the reason for not using the VAS was related to the patients, mainly when they were in too much pain to use it (22%). When the patient was in too much pain, the numerical rating scale was chosen in 54% and the behavioural scale in 27%. There was no difference between young patients and elderly patients.

Conclusions: Although the VAS is the standard method to assess pain, the nurses preferred using the numerical rating scale, both spontaneously or when VAS assessment was not possible.

Summary

Background and objective: Perioperative hypothermia is generally regarded as undesirable, but its incidence rate in the elective procedures in our hospital and the effect of the preventative measures taken against it were unknown. An initial audit indicated that postoperative hypothermia occurred. Therefore, changes in practice were implemented to address the problem. A further audit was then undertaken to assess the impact of these measures.

Methods: The first audit recorded data from 177 patients undergoing major elective surgical procedures. Variables recorded were: ASA classification, duration of operation, use and description of preventative measures for hypothermia, blood loss, intravenous fluids, and core and peripheral temperatures on arrival and discharge from the recovery room. The subsequent audit included 158 patients undergoing major general, orthopaedic or vascular surgical procedures. Patients had core temperatures measured preoperatively, immediately upon arrival in the recovery room, and just before discharge back to the ward. Core temperatures in both audits were measured using an infrared temperature probe.

Results: The mean body temperature on arrival in the recovery room of patients in the initial audit was 35.5°C (range 32.2–37.2, SD ± 0.74), and in the subsequent audit 36.6°C (33.6–38.2, ±0.72). These differences reached significance (P < 0.0001). This was despite an average duration of surgery of 133.5 (25–330) min in the initial study compared with 154.7 (90–480) min subsequently.

Conclusions: We found that with simple but consistently implemented changes in practice, postoperative hypothermia in elective patients could largely be eradicated.