Comparison of EMLA and lidocaine iontophoresis for cannulation analgesia.

BACKGROUND AND OBJECTIVE: Eutectic mixture of local anaesthetic cream and lidocaine iontophoresis are effective in providing analgesia for peripheral venous cannulation with small gauge cannulae in adults and children. The objective of this study was to compare the analgesic efficacy of the two techniques directly in patients using larger cannulae. METHODS: In a double-blind, randomized, controlled study we compared the two techniques directly. Twenty-eight patients had the eutectic mixture of local anaesthetic cream applied to the dorsum of one hand for 60 min followed by sham iontophoresis (group EMLA); the other hand had a sham cream applied for 60 min followed by 10 min of 2 mA iontophoresis with lidocaine 4% and epinephrine 1 in 50,000 (group iontophoresis). Within 5 min of completion of iontophoresis an anaesthetist, unaware of treatment allocation, inserted 18-G venous cannulae into veins of both hands. The patient then scored the amount of pain on cannulation using a 10 point verbal rating scale. RESULTS: Eight patients were excluded from analysis due to failed cannulation (two group EMLA, two group iontophoresis), intolerable burning sensation from iontophoresis (one), protocol violation (one), and changes in surgical schedule (two). Pain scores were lower for the EMLA treated hand than for the iontophoresis side (median (range) 1 (0-7) vs. 3 (0-6); P = 0.023). Erythema and paraesthesia were common but short lived on the iontophoresis side. CONCLUSIONS: Although lidocaine iontophoresis is effective more quickly than the eutectic mixture of local anaesthetic cream, the superior quality of analgesia produced by the eutectic mixture in this study should be borne in mind if these treatments are used electively.

Association between dynamic cerebral autoregulation and mortality in severe head injury.

The objective of the study was to test the hypothesis that dynamic cerebral pressure-autoregulation is associated with the outcome of patients with severe head injury and to derive optimal criteria for future studies on the predictive value of autoregulation indices. Repeated measurements were performed on 32 patients with severe head injury. Arterial blood pressure (ABP) was measured continuously with an intravascular catheter, intracranial pressure (ICP) was recorded with a subdural semiconductor transducer and cerebral blood flow velocity (CBFV) was measured with Doppler ultrasound in the middle cerebral artery. Transfer function analysis was performed on mean beat-to-beat values, using ABP or CBFV as input variables and CBFV or ICP as the output variables. A dynamic index of autoregulation (ARI) ranging between 0 and 9 was extracted from the CBFV step response for a change in ABP. No significant differences between survivors and non-survivors were found due to mean values of ICP, ABP, CPP, CBFV, pCO2, GCS, age or heart rate. The transfer functions between ABP-ICP and CBFV-ICP did not show any significant differences either. The median [lower, upper quartiles] ARI was significantly lower for non-survivors compared with survivors [4.8 (0.0, 5.9) v. 6.9 (5.9, 7.4), p= 0.004]. The correlation between ARI and GOS was also significant (r=0.464, p=0.011). Cohen's coefficient was optimal for a threshold of ARI= 5.86 (kappa 0.51, p=0.0036), leading to a sensitivity for death of 75%, specificity=76.5%, odds ratio =9.75 and overall precision = 75.8%. The difference in ARI values between survivors and non-survivors persisted when results were adjusted for GCS (p = 0.028). A similar analysis for the Marshall CT scale did not reach significance (p = 0.072). A logistic regression analysis confirmed that apart from the ARI, no other variables had a significant contribution to predict outcome. In this group of patients, death following severe head injury could not be explained by traditional indices of risk, but was strongly correlated to indices of dynamic cerebral pressure-autoregulation extracted by means of transfer function analysis. Future studies using a prospective design are needed to validate the predictive value of the ARI index, as estimated by transfer function analysis, in relation to death and other unfavourable outcomes.

Assessment of dynamic cerebral autoregulation based on spontaneous fluctuations in arterial blood pressure and intracranial pressure.

Assessments of dynamic cerebral autoregulation usually measure the cerebral blood flow velocity (CBFV) response to changes in arterial blood pressure (ABP). We studied the effect of substituting ABP by cerebral perfusion pressure (CPP), expressed as the difference between ABP and intracranial pressure (ICP), in estimates of dynamic autoregulation obtained by transfer function analysis. CBFV, ABP and ICP were recorded during periods of physiological stability in 30 patients with severe head injury. Transfer function analysis was performed using the following combinations of input-output variables: ABP-CBFV, CPP-CBFV and CBFV-ICP. Frequency and time-domain (step response) functions were averaged for recordings with mean ICP < 20 mmHg (group A) and mean ICP > or = 20 mmHg (group B). The ABP-CBFV transfer function parameters and step response for group A were similar to previous studies in normal subjects, but group B showed deterioration of dynamic autoregulation. Radically different step responses were obtained from both groups for the CPP-CBFV transfer function and the coherence was not significantly improved. The CBFV-ICP transfer function had the highest values of coherence and indicates that changes in CBFV are the cause of spontaneous fluctuations in ICP. Furthermore, the ICP step response plateau was significantly higher for group B than for group A. An alternative calculation of the CBFV step response to changes in CPP resembled the corresponding responses for the ABP input. For spontaneous fluctuations in ABP, ICP and CBFV, it is not possible to calculate the CPP-CBFV transfer function directly due to the high positive correlation between ICP and CBFV, but an alternative estimate can be obtained by using the CBFV-ICP transfer function. The latter could also be useful as a method to assess intracranial compliance in head injury patients.

Secure fixation of lumbar osteotomy. Surgical experience with 50 patients.

Despite intensive conservative treatment, severe kyphotic spinal deformities may develop in patients with ankylosing spondylitis. Lumbar osteotomy can restore a horizontal visual field in these patients. Of 50 patients undergoing corrective lumbar osteotomy, there were 44 men and 6 women. A transpedicular screw and cable system was used in 37 patients. Mean correction of deformity was 38.7 degrees. Mean loss of correction was 4.8 degrees, but was 15 degrees in those cases in which transpedicular fixation was not used. All patients were able to see straight ahead after the operation. There were 2 deaths and 1 permanent sacral root lesion. Fixation failure was seen in 2 of 37 patients in whom transpedicular implants were used and in 3 of 13 in whom alternative methods of internal fixation were used.

The abbreviated injury scale as a predictor of outcome of severe head injury.

OBJECTIVE: This study examined the correlation between the worst abbreviated injury scale 1990 (AIS) intracranial severity score and outcome following severe head injury. DESIGN: The initial CT scans of 109 severely head injury patients were examined by a neuroradiologist and classified according to the worst applicable intracranial severity code from the AIS. This score was then correlated with the glasgow outcome scale (GOS) at 6 months. For comparison, the GOS was also correlated with the diffuse injury scale (DIS) described by L.F. Marshall et al. [5], the worst post-resuscitation Glasgow coma score (GCS) in the first 24 h, and the head injury outcome prediction tree described by Choi et al. [1]. RESULTS: Our results show Spearman rank correlation coefficients of 0.58 (p < 0.001), 0.47 (p < 0.001), 0.45 (p < 0.001), and 0.31 (p < 0.01) for the correlation between the AIS, prediction tree, DIS, and GCS respectively and the GOS. Independent outcome (i.e. GOS good or moderate) was strongly predicted by an AIS of 3 or less (positive predictive value 95%, specificity 98%, sensitivity 40%, likelihood ratio 25:1). Death or vegetative survival was less strongly predicted in patients with an AIS of 5 (positive predictive value 71%, specificity 75%, sensitivity 67%, likelihood ratio 2.7:1). CONCLUSION: The AIS, based on initial CT scan, provides useful prognostic information in patients with severe head injury.

Somatosensory evoked potentials in intracranial hypertension: analysis of the effects of hypoxia.

The loss of somatosensory evoked potentials (SSEP's) was investigated in a feline model of intracranial hypertension. Threshold values of cerebral perfusion pressure (CPP) and cerebral blood flow (CBF) required for maintenance of SSEP's are defined using a mathematical model. The model describes loss of amplitude of SSEP's using the form of a dose-response curve. Amplitude of the SSEP's declined to 50% of control values at a CBF of 15 ml/100 gm/min and a CPP of 20 mm Hg in the normoxic animal; in the presence of mild hypoxia (8 to 9 kPa), a significant increase in these values to 18 ml/100 gm/min and 32 mm Hg, respectively, occurred. No reliable changes in latency or central conduction time were demonstrated. It is concluded that given adequate oxygenation, evoked electrical activity is lost at too low a level of CPP for this parameter to be useful in clinical monitoring. However, even mild hypoxia, when combined with intracranial hypertension, produces a major risk to neuronal integrity.

Influence of induced hypotension and spinal distraction on feline spinal somatosensory evoked potentials.

Spinal cord injury may occur during surgical correction of spinal deformity, which is performed frequently under hypotensive anaesthesia. We have investigated the interaction between pharmacologically induced hypotension and distraction on feline spinal cord function. Twelve anaesthetized cats were subjected to hypotension (mean arterial pressure (MAP) 60 mm Hg) using a mixture of sodium nitroprusside and trimetaphan (1:5). No significant changes were observed in somatosensory evoked potentials recorded at T11. In six cats distraction was applied at L2-3 in 2.5-mm increments up to 1 cm, while MAP was maintained at 100 mm Hg (normotensive group). The remaining cats were subjected to the same distraction procedure at an MAP of 60 mm Hg (hypotensive group). In the hypotensive group, a reduction in amplitude of evoked response occurred at significantly less distraction than in the normotensive group. These data indicate that the feline spinal cord is more sensitive to spinal distraction under hypotensive conditions.

Evaluation of the IVAC 560 volumetric pump. A clinical and laboratory study.

The performance of a new combined infusion pump and central venous pressure monitor, the IVAC 560, has been evaluated in laboratory and clinical studies. The pump performed accurately and reliably, and the pressure readings obtained from the pump correlated well with conventional methods of pressure measurement, although they lost accuracy when using 50% dextrose at higher venous pressures.

The effect of anaesthetic induction with etomidate on the endocrine response to surgical trauma.

In order to investigate the effects of anaesthetic induction with a single bolus dose of etomidate on the endocrine response to a standard surgical stress, five patients were randomly allocated to receive etomidate and five to receive thiopentone as an induction agent prior to elective inguinal hernia repair. The group receiving etomidate showed a significant suppression in the circulating level of cortisol at 90 and 120 min post-induction (P less than 0.001) and an elevation in their plasma adrenocorticotrophic hormone at 240 and 360 min post-induction (P less than 0.001). The effect of a bolus dose of etomidate upon circulating cortisol levels was transient and no cardiovascular instability was noted during the study. The etomidate group also showed suppression of their circulating testosterone levels at 90 min post-induction (P less than 0.001), suggesting that etomidate inhibits steroidogenesis at a site other than 11 beta-hydroxylase.

Prosthetic arthroplasty of the shoulder.

Twenty-six patients, 18 with rheumatoid arthritis, underwent arthroplasty of the shoulder between 1973 and 1980, with an average follow-up of 3 years. The Stanmore and Kessel arthroplasties and the Neer hemiarthroplasty were used. Twenty-one patients undergoing 22 elective arthroplasties considered that the operation was worthwhile. Pain was completely relieved in 12 shoulders. Movement was improved in 18 shoulders. The priority of restoring movements which improved independence and self-respect is emphasised; the results were far superior to those obtained by an arthrodesis.

Penile block for circumcision? A comparison with caudal blockade.

A prospective blind trial was conducted comparing the analgesia and adverse effects produced by caudal extradural blockade (caudal block) with blockade of the dorsal nerves of the penis (penile block) in 38 boys undergoing elective circumcision. Analgesia was assessed by senior nurses using a linear analogue scale and by the response to direct questioning over the first 7 hours after surgery. The degree and duration of postoperative analgesia was similar in the two groups. However, the caudal block group had a higher incidence of motor blockade (p = less than 0.01). One technical failure occurred in the penile block group. It is concluded that a penile block is a satisfactory alternative to caudal blockade with regard to postoperative analgesia and offers several specific advantages.

Changes in colloid osmotic pressure in patients undergoing cardiothoracic surgery.

Measurements of plasma colloid osmotic pressure (COP) were made during and for 24 h after normothermic continuous flow cardiopulmonary bypass (CPB) in 20 adults exposed to sudden haemodilution by a crystalloid pump prime solution. Haematocrit, albumin and total protein were also measured. Within 5 min of starting bypass the mean COP fell to 45% pre-bypass value and remained at this level until bypass was discontinued. Following bypass, the oncotic pressure rose rapidly during the first hour to 84% of the prebypass value, and then more slowly until it reached the pre-bypass value 24 h later. The trend seen for plasma proteins and haematocrit was similar but the fall was smaller, 65-70% of the pre-bypass values. This significant difference in fall between plasma protein concentration and directly measured COP is explained by their non-linear relationship. Three patients died soon after bypass. They all showed significantly lower values of COP than the mean for the group as a whole at some stage (P less than 0.05).