Prophylaxis against thromboembolism in neurosurgical patients: a survey of current practice in the United Kingdom.

Venous thromboembolism is a life threatening, but preventable complication of major surgery. Many neurosurgical patients are at high risk of developing thromboembolic disease. A postal survey was undertaken of 44 UK neurosurgical centres to assess the use of physical and pharmacological methods of prophylaxis against thromboembolism. Thirty-five replies were received from 31 centres. Seventy-seven per cent of units used antiembolism stockings (TEDs) for elective surgery and 37% for emergency surgery; in approximately two-thirds of these units TEDs constituted the sole method of prophylaxis used during both elective and emergency surgery. Intermittent pneumatic compression (IPC) was utilized in 37 and 11% of units for elective and emergency surgery, respectively. Subcutaneous heparin was used in 32% of units perioperatively including 6% of emergency cases. These findings suggest that neurosurgical patients, who are at moderate to high risk of developing thromboembolic complications, may not receive effective prophylaxis; those undergoing emergency neurosurgery are less likely to receive any form of prophylaxis.

Profound hypotension following intravenous codeine phosphate. Three case reports and some recommendations.

Three adults are described who developed life-threatening hypotension following intravenous codeine phosphate. It is recommended that codeine phosphate should not be given intravenously to adults.

Noninvasive intraoperative monitoring of motor evoked potentials under propofol anesthesia: effects of spinal surgery on the amplitude and latency of motor evoked potentials.

We present the results of intraoperative monitoring of motor evoked potentials from 34 patients undergoing spinal surgery under total anesthesia with intravenously administered propofol. Intraoperative recording was performed with transcranial electrical stimulation. Two groups of patients were studied: 1) a control population of 26 patients undergoing lumbar discectomy for prolapsed intervertebral disc, all of whom had normal preoperative motor conduction; and 2) a population of 8 patients undergoing neurosurgical procedures for spinal tumor (5 patients) and spinal arteriovenous malformation (3 patients), all of whom had abnormal preoperative neurological signs and abnormal preoperative motor conduction. In the first group, electromyographic responses were recorded intraoperatively either from the 2nd dorsal interosseous muscle of the hand (5 patients) or from the 1st dorsal interosseous muscle of the foot (21 patients). In the second group, responses were recorded intraoperatively either from the 1st dorsal interosseous muscle of the foot (7 patients) or from the anterior tibial muscle (1 patient). Intraoperative monitoring of motor function was successful in 88.5% of the patients in the control group. Propofol anesthesia caused a reduction in response amplitude to 7% of baseline values obtained from conscious relaxed subjects. Intraoperative monitoring was successful in 87% of the patients in the pathological group. We observed significant changes in both amplitude (greater than 50%) and/or onset latency (greater than 3 ms) from the intraoperative baseline that indicated either improvement (3 patients) or deterioration (2 patients) in motor conduction within minutes of surgical maneuvers anticipated to alter spinal cord function. Only permanent complete loss of intraoperative motor conduction (1 patient) correlated with a significant change in the postoperative neurological state.(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of nitrous oxide on motor evoked potentials recorded from skeletal muscle in patients under total anesthesia with intravenously administered propofol.

The effect of nitrous oxide (N2O) on motor evoked potentials (MEPs) recorded from human subjects under total intravenous anesthesia with propofol (2,6-diisopropylphenol) was studied. MEPs were recorded from the 1st dorsal interosseous muscle of the foot in nine subjects; in two of these, simultaneous recordings were made from the 2nd dorsal interosseous muscle of the hand and from the deltoid muscle. Single transcranial electrical stimuli were used in recording the MEPs. The effects of N2O were studied at concentrations from 20 to 70%. Increasing concentrations of N2O caused a progressive increase in onset latency and a fall in the peak-to-peak amplitude of the MEPs recorded from the foot. Latency values showed a significant increase above the baseline at concentrations of N2O greater than 20% (P values, 0.05-0.005). The response amplitude showed a significant decrease from the baseline at concentrations of N2O greater than 50% (P values, 0.05-0.005). The 2nd dorsal interosseous muscle of the hand demonstrated a pattern of sensitivity to N2O similar to that of the 1st dorsal interosseous muscle of the foot. The onset latency and initial peak-to-peak amplitude of the deltoid muscle were insensitive to N2O at the concentrations used. We conclude that N2O can be used as an anesthetic adjunct without a significant deleterious effect on MEPs during intraoperative monitoring in patients under propofol anesthesia, providing concentrations are maintained below 50%.

Double-blind comparison of topical lignocaine-prilocaine cream (EMLA) and lignocaine infiltration for arterial cannulation in adults.

In a double-blind, double-dummy study, the efficacy of topical 5% EMLA cream was compared with that of lignocaine infiltration in alleviating the pain of arterial cannulation. Forty unpremedicated adults were allocated randomly to four groups to receive EMLA cream alone, EMLA and 0.9% saline infiltration, EMLA and 1% lignocaine infiltration or placebo cream and 1% lignocaine infiltration. Following arterial cannulation, pain was assessed by the patient using a visual analogue score and by an independent observer using a four-category verbal rating score. Significantly lower pain scores were observed in all patients receiving EMLA compared with those receiving placebo cream and lignocaine infiltration by both patient (P less than 0.01) and observer (P less than 0.001) assessments. There were no significant differences between the three EMLA groups.

Postoperative paraplegia in a patient with an unsuspected dural arterio-venous malformation.

We report a case in which laminectomy was performed in a patient with symptoms attributed to lumbar canal stenosis. The patient developed paraplegia in the early postoperative period. Further investigation revealed a dural arterio-venous malformation. This was treated surgically, producing some neurological recovery. The possible mechanisms for the perioperative deterioration and their implications for anaesthesia are discussed.

Anaesthesia for simultaneous caesarean section and clipping of intracerebral aneurysm.

A 38-yr-old woman who was 35 weeks pregnant presented with a subarachnoid haemorrhage, secondary to a ruptured anterior communicating artery aneurysm. Following initial recovery, she subsequently underwent simultaneous elective Caesarean section and clipping of the aneurysm. The anaesthetic management of the case is described and discussed.

Midazolam and flumazenil in the anaesthetic management of trigeminal nerve thermocoagulation.

A technique is described for the anaesthetic management of trigeminal nerve thermocoagulation by administration of repeated doses of midazolam and flumazenil. "Wake-up" times after administration of flumazenil in 20 patients were shorter than those reported during spontaneous recovery from methohexitone or propofol anaesthesia. The midazolam dose required for a second phase of sedation after antagonism of the first with flumazenil was significantly less than that for the first phase of sedation. There was no evidence of postoperative resedation. Reversal of sedation was associated with an increase in arterial pressure.

Neuro-anaesthesia: the present position.

Over the years the basic principles underlying the practice of neuroanaesthesia have not changed, but introduction of new anaesthetic agents and associated techniques have improved the ability of the neuroanaesthetist to "fine tune" the patients physiological state. This has improved the capacity of the neuroanaesthetist to mitigate the inevitable fluctuations which occur and prevent their ill effects. Further improvement is still desirable and possible. It takes years for the correct plan of usage of new drugs to be formulated for the clinical situation, and their relationships established to new techniques of patient monitoring. Like neurosurgery itself neuroanaesthesia shows no signs of approaching a final definitive state in the forseeable future.

The effects of halothane on somatosensory and flash visual evoked potentials during operations.

Intraoperative use of somatosensory evoked potentials (SEP's) to monitor intracranial aneurysm surgery and flash visual evoked potentials (F-VEP's) for parasellar surgery have been routinely employed in our clinic. We found that both EP modalities are sensitive to the changing concentration of our standard hypotensive agent, halothane. The prolongation of the N14-N20 interpeak latency to median nerve stimulation at the wrist, and prolongation of P100 latency with altered configuration of early VEP components to flash light stimulation, appear to be the results of direct pharmacological effects of the agent and not an effect of secondary hypotension. VEP is found easily abolished by halothane at a concentration of 2.0%, while the SEP is more resistant. Halothane is not ideal however when monitoring intraoperative VEP.

Vertebrovertebral arteriovenous fistula. A complication of internal jugular catheterisation.

A case is presented to demonstrate the complication of vertebrovertebral arteriovenous fistula following attempted internal jugular cannulation. The symptoms, incidence and treatment of such a complication are discussed and certain recommendations made.