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Biomedical subjects

G Bellinzona

Publications and source records attributed to G Bellinzona.

At least 19 recordsLinked to original sources
PubMed2004

Near infrared spectroscopy monitoring during carotid endarterectomy: which threshold value is critical?

OBJECTIVES: Retrospectively to verify which decreasing percentage in regional oxygen saturation (rSO(2)) identified patients with good collateralisation during carotid artery cross clamp. MATERIALS AND METHODS: During 594 endarterectomies under general anaesthesia the decreasing percentage from preclamp value to value detected in the first 2 min after clamping the CCA and/or ICA was calculated in real time. No temporary shunt was placed in any case. ROC analysis was performed to determine the optimal cut-off for rSO(2) decrease to identify the occurrence of neurological complications. RESULTS: A cut-off of 11.7% was identified as optimal. Sensitivity and specificity were 75% (95% CI 71-78) and 77% (95% CI 74-80), respectively. The cut-off of 20% had a lower sensitivity (30%) and a higher specificity (98%) to identify patients with complications, with positive and negative predictive value of 37 and 98%, respectively. CONCLUSIONS: The study suggest that a relative decrease in rSO(2) of <20% from preclamp to early cross clamp value has a high negative predictive value, i.e. if rSO(2) does non decrease more than 20%, ischemia by hypoperfusion is unlikely and a shunt should not be necessary. Moreover, a relative decrease >20% may not always indicate intraoperative neurological complications.

Aged↗
PubMed2001

Brain oxygen tension, oxygen supply, and oxygen consumption during arterial hyperoxia in a model of progressive cerebral ischemia.

We investigated the changes in brain oxygen tension (ptiO2) after ventilation with pure O2 in order to (1) clarify the pathophysiology of O2 exchange in the cerebral microcirculation; and (2) investigate the relationship between brain O2 tension, O2 delivery, and consumption in steady-state conditions during stepwise cerebral blood flow (CBF) reductions. A swine model was developed to reduce CBF in three stable steps: (1) baseline (CBF 100%), (2) CBF of 50-60% of baseline, and (3) CBF of <30% of baseline. CBF was reduced by infusing saline into the left lateral ventricle through a catheter connected with an infusion pump. At each step, hyperoxia was tested by increasing the inspired oxygen fraction up to 100%, PtiO2 reflected the CBF reductions, since it was respectively 27.95 (+/-10.15), 14.77 (+/-3.58), and 3.45 (+/-2.89) mm Hg during the three CBF steps. Hyperoxia was followed by an increase in ptiO2, although the increase was significantly lower when hyperoxia was applied during progressive ischemia. O2 supply to the brain did not change during hyperoxia. Arteriovenous oxygen difference (AVDO2) decreased during the phases of intact CBF and moderate impairment, but not during the phase of severe CBF reduction. In conclusion, ptiO2 reductions closely reflect the imbalance between oxygen delivery and demand; this implies a link between low ptiO2 and defective O2 supply due to impaired CBF. However, this relation is not necessarily reciprocal, since manipulating brain oxygen tension does not always influence brain oxygen delivery, as in the case of ventilation with pure oxygen.

Animals↗
PubMed2000

Oxygen delivery and oxygen tension in cerebral tissue during global cerebral ischaemia: a swine model.

UNLABELLED: Interest in tissue oxygen (PtiO2) monitoring is increasing. However the exact interactions between ptiO2, systemic and cerebral variables are a matter of debate. Particularly, the relationship between ptiO2, cerebral oxygen supply and consumption needs to be clarified. We designed a model to achieve progressive Cerebral Blood Flow (CBF) reduction through 3 steps: 1. baseline, 2. CBF between 50-60% of the baseline, 3. CBF < 30% of the baseline. In 7 pigs, under general anaesthesia, Cerebral Perfusion Pressure (CPP) and CBF were reduced through the infusion of saline in a lateral ventricle. PtiO2 and CBF were monitored respectively through a Clark electrode (Licox, GMS) and laser doppler (Peri-Flux). Blood from superior sagittal sinus and from an arterial line was simultaneously drawn to calculate the artero-venous difference of oxygen (AVDO2). Brain oxygen supply was calculated by multiplying relative CBF change and arterial oxygen content. PtiO2 reflected CBF reductions, as it was 27.95 (+/- 10.15) mmHg during the first stage of intact CBF, declined to 14.77 (+/- 3.58) mmHg during the first CBF reduction, declined to 3.45 (+/- 2.89) mmHg during the second CBF reduction and finally fell to 0 mmHg when CBF was completely abolished. CBF changes were also followed by a decline in O2 supply and a parallel increase in AVDO2. CONCLUSION: This model allows stable and reproducible steps of progressive CBF reduction in which ptiO2 changes can be studied together with oxygen supply and consumption.

Animals↗
PubMed2000

The use of hyperventilation in the treatment of plateau waves in two patients with severe traumatic brain injury: contrasting effects on cerebral oxygenation.

We present the case reports of two patients with severe traumatic brain injury who, in the absence of external stimuli, developed episodes of acute elevation of intracranial pressure (plateau waves) associated with jugular bulb oxyhemoglobin (SjO2) desaturation, severe reduction of cerebral tissue PO2 (PbrO2), and deterioration of neurological status. In all of these episodes hyperventilation was successful in extinguishing plateau waves, but in one patient it was associated with an improvement of both the global (increased SjO2) and local (increased PbrO2) cerebral perfusion, while in the other patient it was associated with a reduction of both SjO2 and PbrO2. In both patients the effects of hyperventilation (and other pharmacological treatments) were short-lived; plateau waves reappeared and the patients had to be submitted to decompressive craniotomy (first patient) and cerebrospinal fluid (CSF) drainage (second patient). We conclude that hyperventilation can be useful as a temporary measure to treat plateau waves, but cerebral oxygenation should always be monitored to avoid iatrogenic cerebral ischemia.

Accidents, Traffic↗
PubMed1998

Effects of cerebral perfusion pressure on brain tissue PO2 in patients with severe head injury.

Ischemia causes secondary brain damage after severe head injury (SHI). Cerebral perfusion is commonly estimated by monitoring CPP, but the adequacy of cerebral oxygenation requires further measurements, such as jugular oxygen saturation or, more recently, PtiO2 monitoring. In 7 patients with severe head injury, ICP, MAP, CPP, SjO2 and PtiO2 were monitored for a mean time of 9.0 +/- 2.2 days. Most of the data were in a "normal" range. Focusing on values under the thresholds of 60 mm Hg for CPP and 20 mm Hg for PtiO2, we found a relationship between CPP and PtiO2. Looking at the PtiO2 time-course, we observed a quite constant increasing trend during the first 48 hours of monitoring, then the values remained relatively constant within a normal range. Our data show that decreases of PtiO2 are not uncommon after severe head injury and therefore it seems that monitoring of PtiO2 in SHI may be useful in order to minimize secondary insults.

Adolescent↗
PubMed1998

[The hemodynamic effects of the in-vivo administration of insulin-like growth-factor I].

BACKGROUND: Recent studies have demonstrated that IGF-I has several biological activities that correlate with the GH axis, by acting as a cell protecting factor and a promoting compound in different tissues and organs. Our latest findings have demonstrated a potential application of IGF-I in the treatment of postischemic renal injury, which frequently appears after a kidney transplant. The beneficial effect of the renal postoperative recovery probably correlates with the regulation of the vascular tone, in which IGF-I plays a role with other cytokines. However, this rises the question whether IGF-I has any effect on the general hemodynamic status. This study was designed to underline the intraoperative hemodynamic effect of exogenous IGF-I in an experimental setting of renal transplantation in swine. METHODS: Twelve female swine underwent a left renal autotransplantation. At the reperfusion the animals were separated in two groups. Group one served as control. Group two received 400 micrograms of IGF-I (added to the flushing solution). The animals were kept under complete hemodynamic monitoring over the operation. RESULTS: Among the different parameters studied (mean arterial pressure, mean pulmonary arterial pressure, pulmonary wedge pressure, central venous pressure, cardiac output, oxygen extraction ratio, systemic vascular resistance, oxygen delivery and oxygen consumption), any statistically significant difference between group one and two were observed. CONCLUSIONS: While the clinical administration of IGF-I requires further studies, the in vivo administration of this peptide is apparently well tolerated, and does not cause any hemodynamic instability to the operation.

Analysis of Variance↗
PubMed1997

The use of indomethacin to treat acute rises of intracranial pressure and improve global cerebral perfusion in a child with head trauma.

BACKGROUND: The use of vasoconstrictors (e.g. dihydroergotamine, indomethacin) for the treatment of increased intracranial pressure (ICP) secondary to brain trauma is controversial. In particular, it has been suggested that vasoconstrictors be employed only for intracranial hypertension secondary to hyperemia, when venous jugular bulb saturation (SjO2) is > 75%. METHOD: We administered indomethacin as a bolus i.v. (5-10 mg) on 18 occasions to a multiple-injured 3-year-old child with acute rises of ICP secondary to severe brain trauma (GCS score 7) determining a large hypodensity area in and swelling of the right hemisphere. RESULTS: Before indomethacin administration the average of mean ICP was 68.1 +/- 10.8 (SD) mm Hg (range 47-84) and the cerebral perfusion pressure (CCP) was 38.4 +/- 10.4 mm Hg (range 30-65). In response to indomethacin, ICP dropped in a few seconds to 22.7 +/- 5.6 and CCP increased to 82.4 +/- 6.1 mm Hg (P < 0.001), while the mean arterial pressure remained unchanged. On 6 occasions SjO2 was also evaluated immediately before and 5 and 10 min after indomethacin administration. Before indomethacin administration, SjO2 values were within the normal range on 2 occasions and abnormally low on four. SjO2 increased from the mean value of 45.6 +/- 15.7 to 59.8 +/- 8.9 (after 5 min) and 60.6 +/- 12.4% (after 10 min) (P < 0.01 versus pre-indomethacin). At the same time the cerebral venous pH increased from 7.43 +/- 0.01 to 7.45 +/- 0.01 (P = 0.01). These findinge suggest that the global cerebral perfusion was improved. Eighteen days after injury the child was awake and was discharged from the ICU. CONCLUSION: To our knowledge, increase of SjO2 in response to indomethacin has not been previously reported. Although great caution is necessary in the use of indomethacin for the treatment of ICP, these findings suggest that indomethacin can be useful for the treatment of acute rises of ICP compromising severely the CCP, even if SjO2 is normal or abnormally low. Under these circumstances, indomethacin can improve the global cerebral perfusion.

Cerebrovascular Circulation↗
PubMed1993

[Hemodynamic changes in liver and multi-organ transplantation].

Multivisceral transplantation is a surgical technique developed as treatment for abdominal metastatic and/or multifocal malignancies. At present its clinical employment is reduced by our fragmentary knowledge of the intraoperative and postoperative outcome. The aim of this study is to compare intraoperative hemodynamic and respiratory changes during multivisceral transplantation (MTV, n = 12) and liver transplantation (OLTX, n = 14). The observations have been carried out a 4 phases: basal (I), visceral (II), reperfusion (III), final (IV). Phase I does not show differences between MTV and OLTX. In phase II MTV presents a lower temperature (T) and pulmonary arterial pressure (PAP) (p > 0.05). Phase III is marked by increasing T differences (p < 0.05), lower cardiac frequency (CF), pH and base excess (BE) (p < 0.05). PAP and cardiac output (CO) show a higher value in MTV (p < 0.05). Phase IV reports the vital signs close to normality in both groups, except pH in MTV (p > 0.05).

Animals↗
PubMed1991

Fibrinolytic (rt-PA) therapy for superior vena cava thrombosis in a multiple trauma patient.

An adult multiple trauma patient (head injury with coma, blunt chest trauma, bone and pelvis fractures) developed superior vena cava thrombosis which extended to the right atrium as a complication of central venous catheterism. Since a four day heparin therapy was unsuccessful, the patient was treated with recombinant tissue-type plasminogen activator (rt-PA), 100 mg over three hours. Thrombolysis with rt-PA was not associated with cutaneous or internal bleeding and was partially effective (improvement of the clinical picture, disappearance of the right atrium thrombus, superior vena cava still occluded). Although our patient could have benefited from an additional administration of rt-PA, we did not start a second course because the risk of major hemorrhage increases over 100 mg. For its relative clot-selectivity rt-PA could be indicated when fibrinolytic treatment is required in multiple trauma patient, but safe and more efficacious regimens have still to be defined.

Adult↗