C. K. Spiss

The level of neuromuscular block needed to suppress diaphragmatic movement during tracheal suction in patients with raised intracranial pressure: a study with vecuronium and atracurium

The effects of tracheobronchial suction before and after neuromuscular blockade with vecuronium (0.12 mg.kg−1; ED95 X 2; group A) and atracurium (0.4 mg.kg−1; ED95 X 2; group B) on intracranial pressure were studied in 18 neurosurgical patients with a Glasgow Coma Scale < 7. Despite adequate sedation, moderate to severe diaphragmatic movements (bucking and coughing) in response to carinal stimulation with significant increases in intracranial pressure (A: 18 SD 7 to 24 SD 8 mmHg; B: 19 SD 7 to 27 SD 5 mmHg) and subsequent decreases in cerebral perfusion pressure (group A: 69 SD 11 to 63 SD 8 mmHg; group B: 63 SD 11 to 59 SD 17 mmHg) could be observed without muscle relaxation. After a bolus dose of vecuronium or atracurium, profound neuromuscular paralysis quantified by the post‐tetanic count, was observed after an onset time of 253 SD 72 s (vecuronium) and 159 SD 54 s (atracurium). Slight diaphragmatic movements could be elicited in only two patients in group A and in two patients in group B during tracheal suction; intracranial pressure (group A: 20 SD 8 to 20 SD 8 mmHg; group B: 19 SD 7 to 19 SD 7 mmHg) and cerebral perfusion pressure (group A: 65 SD 13 to 65 SD 13 mmHg; group B: 66 SD 12 to 65 SD 11 mmHg) remained unchanged. When coordinating respiratory therapy in neurosurgical intensive care patients, profound neuromuscular block, quantified by a post‐tetanic count of at least 5 for vecuronium and 1 for atracurium, it is necessary to rule out any impact of diaphragmatic movement on intracranial pressure. Repeated neurological evaluation was not inhibited when utilising an intermittent bolus‐dose regimen.

Effect of sufentanil on intracranial pressure in neurosurgical patients

The effects of sufentanil on intracranial pressure, mean arterial pressure, cerebral perfusion pressure and heart rate were studied in 20 neurosurgical intensive care unit patients. Epidural intracranial pressure probes were implanted in patients who suffered head injury, intracerebral haemorrhage or underwent tumour resection. Sufentanil was given intravenously in sequential doses of 0.5, 1.0 and 2.0 μg/kg. Fifteen minutes elapsed after each dose. The patients were allocated to either group 1 (baseline intracranial pressure < 20 mmHg) or group 2 (baseline intracranial pressure > 20mmHg). Intracranial pressure did not change significantly in either group. Therefore the falls in mean arterial pressure with the highest dose in both groups and with 1.0 μg/kg in group 2, closely reflect corresponding reductions in cerebral perfusion pressure. As sufentanil in itself exerts no effects on intracranial pressure, concomitant haemodynamic changes are the critical factor for an adequate cerebral perfusion pressure.

Electroencephalographic burst suppression by propofol infusion in humans : hemodynamic consequences

The hemodynamic effects of a propofol infusion adjusted to achieve and maintain a burst-suppression pattern [episodes of depressed background activity (electrical silence) more than 4 s alternating with a high-voltage slow activity], were studied in 10 patients without cardiorespiratory disease undergoing elective neurosurgical interventions. Propofol infusion was started after a bolus dose of 1 mg/kg at a rate of 20 mg.kg-1 x h-1, reduced after 30 min to 15 mg.kg-1 x h-1, and terminated after 60 min (1926 +/- 346 mg cumulative propofol dose, maximal serum concentration 9.2 +/- 2.9 micrograms/dL; mean +/- SD). Hemodynamic data and arterial blood samples were collected during a sedated, resting control period, and then every 15 min during drug infusion. Lactated Ringers solution was infused at a rate sufficient to maintain pulmonary capillary wedge pressure at or above control levels (20-30 mL.kg-1 x h-1). Burst-suppression pattern in the electroencephalogram was achieved after 15.7 +/- 3.2 min and maintained until 10.9 +/- 2.6 min after the propofol infusion was terminated. Significant decreases (% of control, Friedman and Wilcoxon Wilcox test, P < 0.05) were found in heart rate (19%), mean arterial pressure (20%), cardiac index (23%), and left ventricular stroke work index (26%). No adverse consequences were caused by the propofol or crystalloid infusion. The results demonstrate that doses of propofol sufficient to silence the electroencephalogram are associated with venodilating and myocardial depressant properties. However, propofol can be administered with minimal hemodynamic risk in healthy patients when cardiac filling pressures are maintained by intravenous fluid administration.

Coeliac plexus block with bupivacaine reduces intestinal dysfunction in neurosurgical ICU patients.

Coeliac plexus block, an established method of treatment for pain associated with pancreatitis and cancer, was used in neurosurgical patients with gastrointestinal dysfunction. The study was performed in 16 patients whose gastric reflux volume exceeded 600 ml per day for 3 consecutive days. Patients were allocated to a block group (n = 8) or a control group (n = 8). Coeliac plexus block was accomplished with a modified Moore technique using 50 ml bupivacaine 0.25%. In the block group, gastric reflux volumes for 3 days preceding coeliac plexus block and 3 consecutive days following coeliac plexus block were analysed. In the control group, gastric reflux volumes were observed over a period of 6 days. Mean (Sem) gastric reflux volume decreased significantly following coeliac plexus block from 770 (50) ml to 60 (30) ml (p > 0.01). In the control group, gastric reflux remained unchanged over the corresponding periods (730 (60) ml c.f. 670 (50) ml). The response of gastric reflux volume to coeliac plexus block suggests that the mechanism is related to inhibition of sympathetic activity in patients whose sympathetic drive is increased due to the underlying neurological disease, and possibly due to sedation withdrawal symptoms.

Comparative analysis between epidural (Gaeltec) and suboural (Camino) intracranial pressure probes

The new fiberoptic Camino system has recently been introduced for clinical intracranial pressure (ICP) monitoring. We compared the subdural Camino system with the well-established epidural Gaeltec system in both in vitro and clinical conditions. In the in vitro experiments the intracranial vault was simulated by a tightly closed, fluid-filled box (0.9% sodium chloride) with the two probes inside. We simulated pulsating waveforms with a jet ventilator. No difference between the simulated curve patterns and values could be detected. In the clinical studies, both probes were implanted in 10 patients who had either head injuries, subarachnoid hemorrhage, or intracerebral hemorrhage. The in vivo comparison revealed no significant difference between the two systems in the recorded pressures in group 1 (ICP<20 mm Hg). The subdurally placed Camino probe showed insignificantly lower ICP values than did the extradural Gaeltec probe. Although group 2 (ICP>20 mm Hg) waveforms were nearly identical, significant differences (p<0.01) in pressure measurements (systolic, diastolic, and mean) occurred (Camino, 18±3 mm Hg; Gaeltec, 27±3 mm Hg). Correlation coefficients for mean ICP values were 0.82 in group 1 and 0.49 in group 2. Problems with the Camino probe were usually mechanical and occurred in 2 patients. The problems were either easy to recognize or manifested as an ostensibly pathologic curve. No infection occurred with either system during or following implantation. The dissimilar characteristics of the two probes can be ascribed to their different extradural and subdural implantation sites. The Gaeltec probe was more durable over the period of implantation, which averaged 98 hours and ranged from 44 to 298 hours. Intracranial pressure values measured subdurally seemed to be more true to life in the high-pressure ranges. Both probes can be used for routine, continuous ICP monitoring. While subdural ICP probes can give correct values without delay and in vivo show more detail and change with ventilation, the epidural system was more durable.

Sufentanil does not increase cerebral blood flow in healthy human volunteers

The effect of sufentanil on human cerebral blood flow (CBF) was studied in seven unpremedicated, healthy volunteers 31 +/- 3.5 yr of age (mean +/- SD) and either sex. CBF (ml.100 g-1.min-1) was measured noninvasively with the 133Xe clearance technique and a scintillation camera before and after sufentanil 0.5 micrograms/kg administered intravenously. This technique provides values for global blood flow and for gray and white matter blood flow, and from 13 preselected regions in one hemisphere. After the administration of sufentanil, the volunteers were stimulated verbally in order to prevent their loss of consciousness and hypercarbia. Heart rate (HR), arterial pressure, oxyhemoglobin saturation, and end-tidal CO2 (ETCO2 were recorded during the measurements. Neither global CBF (46.1 +/- 1.6 control and 43 +/- 1.9 after sufentanil, mean +/- SEM) nor gray (76.5 +/- 3.2 and 70.9 +/- 6.1) or white (22.7 +/- 1.5 and 24.2 +/- 1.6) matter blood flow changed significantly after sufentanil administration. As well, no significant differences in HR (72 +/- 4 control and 79 +/- 4 beats per min after sufentanil) and ETCO2 (39.8 +/- 1.4 and 41.1 +/- 1.1 mmHg) were observed. It is concluded that sufentanil has no significant effect on CBF in healthy human volunteers.

Detection of graft nonfunction after liver transplantation by assessment of indocyanine green kinetics

I ndocyanine green dye (ICG) has been used in tests for a global measure of liver perfusion and excretory function for more than three decades (1) and has shown good correlation with the severity of hepatic disease as well as with outcome in liver transplant recipients (2-5). We report a case of the early detection of graft nonfunction after orthotopic liver transplantation (OLT) using a bedside monitoring device for fiberoptic assessment of ICG plasma disappearance rate (ICG PDR) (normal value 20%-30%) (2) in a 43-yr-old woman who underwent OLT because of cholangiocellular carcinoma. Retransplantation was performed, and the patient was dismissed from the hospital 3 wk after the first OLT.

Clonidine : an adjunct in isoflurane N2O/O2 relaxant anaesthesia : effects on EEG power spectra, somatosensory and auditory evoked potentials

We investigated the effect of clonidine in 19 patients having lumbar disc surgery under nitrous oxide/isoflurane/relaxant anaesthesia. The EEG, spinal and cortical somatosensory evoked potentials, and the brainstem auditory evoked potentials were recorded. After equilibration of the general anaesthetic, two successive infusions of clonidine (5μg.kg‐1) were given. After the second infusion of clonidine, the plasma concentration increased from 0.2(SEM 0.05) to 6.4(SEM 0.06) ng.ml‐1 (p < 0.05). In the EEG, δ‐activity was maintained, but the β‐fraction, and the 95% and 50% spectral frequencies were reduced. Total EEG power progressively decreased from 296(152‐397) μV2 to 108(51‐240) μV2. The somatosensory evoked spinal potential (N13) decreased in amplitude, (1.77(SEM 0.35) μV to 1.59(SEM 0.35) μV, p < 0.05) and increased in latency (14.37(SEM 0.29)ms to 14.69(SEM 0.31)ms, p < 0.05). The central conduction time increased from 6.47(SEM 0.16)ms to 6.92(SEM 0.25)ms, ns. There was no effect on the cortical somatosensory potentials, or the brainstem auditory evoked potentials. According to the EEG spectral indices, anaesthesia appeared to deepen despite a reduction in the end expiratory isoflurane concentration from 0.53(SEM 0.07) to 0.28(SEM 0.06)vol%, which indicated a reduction in anaesthetic requirements following clonidine.

Intrathoracic fluid volumes and pulmonary function during orthotopic liver transplantation

BACKGROUND Impaired pulmonary function is a frequent finding in patients undergoing orthotopic liver transplantation (OLT). Experimental data suggest an essential contribution of splanchnic ischemia and reperfusion as a result of intraoperative volume shifts, i.e., the accumulation of extravascular lung water (EVLW). Increases of intrathoracic blood volume (ITBV) and pulmonary blood volume (PBV) might additionally influence pulmonary capillary fluid filtration. The main objective of this study was to determine the intrathoracic volume changes during OLT and to test whether there were any relationships between intra- and extravascular volume shifts and pulmonary function, as determined by the calculation of venous admixture (QS/QT) and alveolar-arterial oxygen gradient (AaDO2). METHODS Twenty-five patients undergoing OLT were studied. Using the transpulmonary double indicator dilution method, ITBV, PBV, and EVLW were determined from the mean transit times and exponential decay times of the indocyanine green and the thermal indicator curves recorded simultaneously with a fiberoptic catheter in the descending aorta. Recordings were made after induction of anesthesia, at the end of the anhepatic stage, immediately after reperfusion, and 1 and 4 h postoperatively. RESULTS Significant increases in QS/QT related to changes of ITBV were observed after reperfusion. Only a minor impact on AaDO2 was perceived. EVLW remained constant during the study period. CONCLUSIONS Postreperfusion increases of ITBV influence pulmonary function, as demonstrated by the increase in QS/QT. However, they need not be associated with greater EVLW levels, and impact on oxygenation is less severe than assumed. Hence, sufficient mechanisms protecting oxygenation and stalling increased EVLW seem to be present during uncomplicated human OLT.

Continuous beta-lactam antibiotic therapy in a double-lung transplanted patient with a multidrug-resistant Pseudomonas aeruginosa infection.

Background. It is well known that the bactericidal effect of &bgr;-lactam antibiotics is closely related to the time which the serum concentration of the antibiotic remains above the minimal inhibitory concentration of the target pathogen. Thus, the optimal administration of &bgr;-lactam antibiotics would be the continuous infusion of the drug. Methods. We present a case report with a critically ill double-lung transplanted patient with pneumonia due to a multidrug- resistant Pseudomonas aeruginosa who received continuously 8 g meropenem/24 hr. Based on a previous pharmacokinetic study showing that continuous infusion of meropenem is at least equivalent to intermittent administration this case report is reported to demonstrate the clinical efficacy of continuous infusion. Results. C-reactive protein and pneumonia decreased rapidly when clinical conditions were improved significantly. Continuous administration of meropenem did not interfere with cyclosporine, no side effects were seen, and the patient’s renal function was not impaired during the whole period of treatment. Conclusion. The continuous administration of &bgr;-lactam antibiotics is a powerful application in critically ill patients to intensify antimicrobial therapy.