Somatosensory evoked potentials in cerebral aneurysm surgery.

Monitoring of median nerve somatosensory evoked potentials (SSEP) during surgery for a basilar artery aneurysm under moderate hypothermia revealed an unexpected loss of the first cortical peak. This was due to compression of the middle cerebral artery under the retractor during the surgical approach to the aneurysm and would have continued unnoticed for some time in the absence of monitoring, possibly resulting in infarction in the territory of the middle cerebral artery. When the surgeon was alerted the artery was released and the evoked potential returned within about 24 min. There was no new focal neurological deficit postoperatively.

Somatosensory evoked potentials in cerebral aneurysm surgery.

Somatosensory evoked potentials (SEP) were used intraoperatively 25 cerebral aneurysm cases during the temporary occlusion of the parent artery of the aneurysm under moderate hypothermia. This technique of vascular occlusion is very useful in facilitating the dissection of difficult aneurysms as well as in reducing the risk of intraoperative rupture. Middle cerebral artery (MCA) cases in Hunt & Hess's grade III, undergoing early surgery, who had shown a transient neurological deficit at the time of subarachnoid haemorrhage or where vasospasm was evident in intraoperatively were prominent among 6 cases where the median nerve SEP was lost within 13 minutes of temporary MCA occlusion at 28.6 degrees C to 31.1 degrees C. A transient neurological deficit was seen in one of these and a permanently increased deficit in the other. In contrast, the SEP was well maintained during occlusion times of upto 52 minutes in 8 cases in the absence of any of the above circumstances. The SEP was lost after 7 minutes in one of 5 cases of internal carotid artery occlusion; this was followed by a paresis of a few hours' duration. The posterior tibial nerve SEP was absent for one minute in one of 5 cases of bilateral A1 segment occlusion; none of these cases showed a postoperative deficit. It is concluded that 1. appropriate SEP monitoring can make a major contribution to patient safety in aneurysm surgery, 2. substantially longer cerebrovascular occlusion times are permissible during hypothermia than at normal temperatures and 3. the employment of additional cerebral protective measures should be considered in cases at high risk from ischaemic damage.

Evoked potential monitoring and temporary clipping in cerebral aneurysm surgery.

Temporary occlusion of the parent artery greatly facilitates the dissection of large cerebral aneurysms, while much reducing the risk of intraoperative rupture and avoiding the use of profound arterial hypotension. Intraoperative somatosensory evoked potential (SEP) monitoring was carried out in 25 aneurysm cases where temporary clipping was employed electively under moderate hypothermia. Occlusion times ranged from 6.3 to 52 minutes at 28.7 degrees C to 32.5 degrees C. Among 15 middle cerebral artery (MCA) occlusion cases the SEP was lost within 5 or 6 minutes in two cases undergoing early surgery and in one case with marked vasospasm and was lost within 9 minutes in one case with pre-existing infarction in the territory of the MCA. The SEP persisted throughout MCA occlusion periods of 6.3 to 52 minutes in 8 cases. Occlusion of parent arteries of unruptured aneurysms was well tolerated. At least 2 minutes of MCA occlusion after loss of the SEP were tolerated without neurological sequelae, while transient new deficits were seen when MCA occlusion was continued for 4 and for 4 + 11 minutes and an increased deficit was seen when occlusion was continued for 7 minutes after loss of the SEP. In each of the internal carotid artery (ICA) occlusion and bilateral anterior cerebral artery occlusion groups the SEP was lost in one case and was absent for about one minute before reperfusion was instituted. The ICA case had a transient deficit lasting about 4 hours; no other complications were seen in these two groups. Complications were not seen in any case where the SEP was not lost during the occlusion period. Factors affecting collateral perfusion and possible means of increasing tolerance to ischaemia in this situation are discussed.(ABSTRACT TRUNCATED AT 250 WORDS)

Somatosensory evoked potential monitoring of temporary middle cerebral artery occlusion during aneurysm operation.

Somatosensory evoked potentials (SEPs) in response to median nerve stimulation were used as a guide to cortical function during temporary occlusion of the distal M1 segment of the middle cerebral artery (MCA) in the surgical treatment of five large aneurysms of the MCA bifurcation. MCA occlusion times ranged from 8 to 19 minutes under moderate hypothermia at 28.8 degrees to 30.3 degrees C. SEPs were preserved for variable times during MCA occlusion, ranging from no increase in latency after 13 minutes of occlusion to severe deterioration after 6 minutes. In no case was MCA occlusion maintained for longer than 3 minutes in the presence of a severely disturbed SEP. Recovery of the SEP to its preoperative relationship with that of the nonoperated hemisphere was seen in all cases before the end of operation. All patients were awake after rewarming at the end of operation without any neurological deficit. Monitoring the SEP pertaining to the territory of a cerebral artery during its temporary occlusion can help avoid ischemic damage and will allow the surgeon to take advantage of the several benefits of this technique in aneurysm surgery.

Barbiturates for cerebral aneurysm surgery. A review of preliminary results.

Ninety-two cerebral aneurysm cases treated by clipping under moderate hypothermia are reviewed. Twenty-three of these cases received pentobarbitone during surgery in doses sufficient to render the EEG flat. The overall combined mortality and morbidity (complication rate) among 69 non-barbiturate cases was 21.7%. There were significant differences in results between aneurysms in different anatomical locations. The complication rate among eight middle cerebral artery aneurysm cases was 62.5% and among ten internal carotid artery bifurcation cases 40%, while that among nineteen internal carotid artery cases was 16% and among 27 anterior communicating complex cases 7.4%. The overall complication rate among 23 pentobarbitone cases was 17%. There were no complications among eight middle cerebral artery cases; one of two internal carotid bifurcation cases became hemiplegic following occlusion of the middle cerebral artery at is origin. The complication rate among nine internal carotid cases was 22%. No difficulties were experienced regarding haemodynamic stability or cardiac rhythm while using pentobarbitone at normothermia or at 28 degrees C. It is suggested that cerebral aneurysms involving the middle cerebral artery which appear to be most at risk may have the most to gain by the prophylactic use of pentobarbitone during surgery.

Modification of ketamine-induced intracranial hypertension in neurosurgical patients by pretreatment with midazolam.

The effect on intracranial pressure (ICP) of ketamine as an anaesthetic induction agent following pretreatment with either midazolam (ten cases) or diazepam (five cases) was investigated in unpremedicated neurosurgical patients. In all patients in the midazolam group, ICP increased following ketamine while the cerebral perfusion pressure (CPP) fell in five cases. ICP rose further after intubation by a mean of 21 mmHg (2.8 kPa) with a further drop in CPP in two cases. The changes were usually terminated after pethidine was given but were allowed to continue for 10 min or more in two cases. There was little increase in ICP after the diazepam-ketamine combination, while the CPP fell in one case and increased markedly in two cases. The mean increase in ICP following intubation was 6 mmHg (0.8 kPa) above control values. All patients required assisted ventilation after either benzodiazepine-ketamine combination. It is concluded that midazolam much more effectively suppresses the cardiostimulatory action of ketamine than the increase in ICP and that neither a midazolam-ketamine nor a diazepam-ketamine combination should be considered safe for use in patients who may have reduced intracranial compliance.

Transfrontal pituitary surgery: clinical results, intraoperative management, and postoperative monitoring.

Sixty-nine cases of pituitary tumours with suprasellar extensions are reviewed. Twenty cases were recurrent. All were removed via a frontal craniotomy and surgery was performed under moderate hypothermia in all except seven cases. In 59 cases, lumbar cerebrospinal fluid (CSF) drainage was performed in order to improve operating conditions. Amongst 42 primary cases, 29 (69%) were uncomplicated, 5 (12%) developed severe transient complications and one (2.4%) had a persistent deficit postoperatively; there were no deaths. Amongst 17 recurrent cases, 6 (35%) were uncomplicated; there were five deaths (29%) in the immediate postoperative period and one patient had a persistent deficit (6%). Acute hypertension and/or bradycardia were seen in 32 cases (54%) at the time of lumbar CSF drainage. These included all those who subsequently died and 10 of the 12 cases who developed severe complications. In 7 cases where ventricular CSF drainage was performed intraoperatively, one showed acute hypertension accompanying brain retraction but there were no postoperative complications. Two of these cases were recurrent. Postoperative intracranial pressure, measured epidurally, varied widely in both complicated and uncomplicated cases and was frequently low (less than 10-15 mm Hg) in the presence of severe complications. It is concluded that lumbar CSF drainage should not be performed in the presence of a suprasellar extension and that postoperative monitoring of the epidural pressure is of little value in these cases for the early detection of postoperative complications pertaining to the operative field.

Some principles of postoperative epidural pressure monitoring.

A retrospective analysis is presented of 115 cerebral tumour cases where continuous epidural pressure (EDP) monitoring was carried out postoperatively using an implantable transducer constructed on a coplanar principle. Correct implantation of the transducer is crucial to reliable measurement. The influence of transducer location on EDP is highly significant and can be accounted for at least partly by hydrostatic forces. The effect of postural changes similarly has a hydrostatic component. Clinically complicated cases were usually easily distinguishable from uncomplicated cases with a similar transducer location. EDP is usually low in the absence of complications during the first 6 to 12 hours postoperatively. For postoperative monitoring, an EDP transducer should be placed as near to the site of surgery as possible for maximum sensitivity to local pressure changes and the earliest detection of complications.

Cardiac arrest during moderate hypothermia for cerebrovascular surgery.

A case of cardiac arrest during moderate hypothermia and profound hypotension following rupture of a cerebral aneurysm is described. The patient survived with few neurological sequelae directly attributable to the period of cerebral ischaemia. The protective effect of hypothermia in the prevention of neurological damage is illustrated as are the difficulties of resuscitation.

Barbiturate therapy in cerebral ischaemia.

Experimental and clinical studies of the protective effect of barbiturates in cerebral ischaemia are reviewed. Their action in protecting the brain from the effects of ischaemia is related to their action as anaesthetic agents and probably to the depression of neuronal function and metabolism but is incompletely understood. Their effect is dose related. Early administration is likely to be crucial to the success of barbiturate therapy as secondary events following an episode of cerebral ischaemia can lead to irreversible brain damage within 2--3 h. A potential collateral circulation appears to be essential for the protective effect of barbiturates. There may be a possibility of partly overcoming time delays in administration by giving larger doses of barbiturates.

Barbiturate therapy in the management of cerebral ischaemia.

Two patients who underwent surgery for cerebral aneurysms are presented. In the first case 31 g thiopentone were given postoperatively over 20 h after the patient had already been comatose for many hours. Such high doses raise considerable problems in patient management. In the second case a loading dose of 50 mg/kg thiopentone was given prophylactically to a patient undergoing cerebral aneurysm surgery beginning at the induction of anaesthesia and before surface cooling was begun. Cerebral activity was monitored continuously with a cerebral function monitor (CFM). There was no significant cardiovascular depression, little delay in postoperative recovery and no permanent neurological sequelae. In cerebral aneurysm surgery, cerebral oedema following cerebral ischaemia, either associated with vasospasm or resulting from surgical occlusion of vessels, remains a major problem postoperatively and may be an indication for preventive treatment with barbiturates. The author contend that this technique merits further evaluation in cerebro-vascular surgery, especially in high risk cases.

Transcutaneous aortovelography: reproducibility in adults and children.

Transcutaneous aortovelography (TAV), a new ultrasonic technique for measuring instantaneous mainstream blood velocity in the aorta, is described. The technique uses the Doppler shift principle. The highest local blood velocity within the aortic arch can be recorded from a transducer placed in the suprasternal notch. Inspection of the systolic complexes recorded allows measurement of peak velocity, systolic complex area (proportional to ejected stroke volume), mean (time averaged) blood velocity and initial systolic acceleration. Formal analysis of variance was performed on measurements made by the five observers on 11 healthy adults and by 2 observers on 10 healthy children. Coefficients of variation of from 4 to 8% were found of all variables other than acceleration where the variation was up to 16%. Peak velocities in adults ranged from 97 to 130 cm/sec and were higher in children.

[Chorea minor during administration of oral contraceptives. Analogy to chorea gravidarum]. / Chorea minor unter Anwendung von Ovulationshemmern. Eine Analogie zur Chorea gravidarum.

PIP: A 19-year-old patient on oral contraceptives for 5 months experienced recurrence of Chorea minor suffered in childhood. In the literature 7 similar cases have been reported. In all but 1 of the cases the disease had occurred in childhood, and in all of the cases the symptoms disappeared a few weeks or months after discontinuation of the ovulation inhibitors. Chorea minor is only rarely observed in adults, and then only in women in (usually early) pregnancy. Apparently ovulation inhibitors produce a pregnancylike situation as a predisposing condition for this rare complication.^ieng