Bispectral index values and propofol concentrations at loss and return of consciousness in patients with frontal brain tumours and control patients.

BACKGROUND: The influence of frontal brain tumours on bispectral index (BIS) measurements and propofol requirements is unknown. The primary aim of our study was to determine whether BIS values recorded at loss and return of consciousness (LOC and ROC, respectively) differ between patients with unilateral frontal brain tumours and control patients. Secondary goals were to compare propofol requirements for LOC and to determine whether there were significant inter-hemispheric differences between BIS values in tumour and control patients. METHODS: We enrolled 20 patients with a frontal brain tumour and 20 control patients. Bilateral BIS measurements were done during induction of propofol anaesthesia, during recovery of consciousness, and during a second induction of anaesthesia. The isolated-forearm test was used to determine the moments of LOC1, ROC, and LOC2. Arterial blood samples were obtained every 4 min for determination of measured propofol concentrations. RESULTS: The median BIS values recorded at LOC1, ROC, and LOC2 did not differ between the groups. There were no significant inter-hemispheric differences in BIS in tumour and control patients. The median [inter-quartile range (IQR)] total propofol doses at LOC1 were 82 (75-92) and 78 (68-91) mg in tumour and control patients, respectively. The median (IQR) measured plasma propofol concentrations at LOC1 were 12 (9-14) and 13 (11-15) µg ml(-1) in the tumour and control groups, respectively. CONCLUSIONS: The presence of a frontal brain tumour did not affect ipsilateral BIS values, and so need not influence the placement of unilateral BIS electrodes if BIS monitoring is used to titrate propofol anaesthesia.

Cerebral haemodynamic physiology during steep Trendelenburg position and CO(2) pneumoperitoneum.

BACKGROUND: The steep (40°) Trendelenburg position optimizes surgical exposure during robotic prostatectomy. The goal of the current study was to elucidate the influence of this patient positioning on cerebral blood flow and zero flow pressure (ZFP), and to assess the validity of different methods of evaluating ZFP. METHODS: In 21 consecutive patients who underwent robotic endoscopic radical prostatectomy under general anaesthesia, transcranial Doppler flow velocity waveforms and invasive arterial and central venous pressure (CVP) waveforms suitable for analysis were recorded throughout the whole operative procedure in 14. The ZFP was determined by regression analysis of the pressure-flow plot and by different simplified formulas. The effective cerebral perfusion pressure (eCPP), pulsatility index (PI), and resistance index (RI) were determined. RESULTS: While patients were in the Trendelenburg position, the ZFP increased in parallel with the CVP. The PI, RI, gradient between the ZFP and CVP, and the gradient between the CPP and the eCPP did not increase significantly (P<0.05) after 3 h of the steep Trendelenburg position. Using the formula described by Czosnyka and colleagues, the ZFP correlated closely with that calculated by linear regression throughout the course of the operation. CONCLUSIONS: Prolonged steep Trendelenburg positioning and CO(2) pneumoperitoneum does not compromise cerebral perfusion. ZFP and eCPP are reliable variables for assessing brain perfusion during prolonged steep Trendelenburg positioning.

[Subtotal parotidectomy for a parotid gland tumour in two players of wind instruments, with preservation of facial nerve function]. / Subtotale parotidectomie wegens een parotistumor bij twee blaasmuzikanten, met behoud van de N.-facialisfuncties.

Two professional musicians, a 55-year-old clarinet player and a 58-year-old trumpet player, presented to the surgical outpatient clinic with a Warthin's tumour and a pleomorphic adenoma in the deep lobe of the parotid gland, respectively. The several branches of the facial nerve form the virtual plane between the superficial and deep lobes of the parotid gland. Due to the localisation of this nerve, parotid surgery entails a significant risk of neurapraxia of the facial nerve branches. Before the operation, both patients were informed carefully about both the necessity and the risks of surgical excision of parotid tumours. Even slight damage to the facial nerve during parotidectomy could have severe implications for their careers. Both underwent subtotal parotidectomy. Postoperatively, there was clinically a temporary minor marginal branch dysfunction in one patient. Pre- and postoperative electromyography did not indicate asymmetrical function of the facial muscles. A few weeks after the operations, both musicians could resume playing; subtotal parotidectomy can apparently be safely performed in players of wind instruments.