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Query: UMLS:C0020440 (hypercapnia)
 7,939 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

CPP reflects perfusion problems related to increased ICP or inadequate MAP. CPP is a most helpful and practical management tool. The relationship of CBF and CPP depends on cerebral vascular resistance (flow equals pressure divided by resistance). At present, we do not have a practical method to measure vascular resistance or CBV. A close relationship between an increase in CBV and increase in ICP exists. However, the relationship between CBF and ICP is more complex. Whereas CBV is strongly dependent on vasodilation and venous return, CBF is influenced by CPP, vascular resistance, viscosity changes, and focally or diffusely increased ICP. For instance, in hypotensive shock one finds a low CBF with an elevated CBV (and ICP) from vasodilation related to hypercapnia, anoxia, or acidosis. Nevertheless, about two thirds of patients with increased ICP after head injury have increased CBF (hyperemia) and increased CBV. This frequent hyperemia is one rationale for the wide usage of hyperventilation to treat increased ICP. It must be recognized that a group of patients may have ischemia caused by excessive hyperventilation therapy for increased ICP. The PaCO2 must not be allowed to decrease to 20 mmHg or lower, but in some patients a PaCO2 level of 21 to 25 may be predisposing to ischemia. Strong consideration is thus given to monitoring CBF and cerebral oxygen metabolism (arteriovenous oxygen content difference [AVDO2], CMRO2) in states of coma and increased ICP. In such patients, continuous infusion of mannitol may result in improved CBF, and hyperventilation therapy can be less aggressive.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Nonsurgical management of increased intracranial pressure. 270 May 10

The findings of this clinical study suggest that the ETTS/MH procedure could be safely performed upon patients with severe closed head injuries whose baseline measurements of MICP were within the range of 0 to 20 mm Hg, provided the CPP was maintained at 50 mm Hg or greater. The advantages of performing the ETTS/MH procedure upon intubated patients far outweigh the possible disadvantages. The removal of pulmonary mucus plugs and secretions, which subsequently prevents hypercarbia and hypoxemia, is very important to the patient's recovery. In most situations, stimulation of the cough reflex through ETTS or even MH can help prevent atelectasis, a frequent pulmonary complication of neurologically depressed patients. Atelectasis can result in hypoxia that may adversely affect the cerebrovascular status. In addition, the results of this study suggest that multiple MHs after the third and subsequent ETTSs should be extended to a longer time interval, perhaps 60 seconds, in order that the physiologic measurements of MABP, MICP, CPP, and HR more closely approach the baseline levels. Also it is suggested that nurses performing the ETTS/MH procedure delay initiation of levels of physiologic function used to assess cerebrovascular status are reached.
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PMID:The effects of the endotracheal tube suctioning/manual hyperventilation procedure on patients with severe closed head injuries. 656 6

The management of critically ill children with traumatic brain injury (TBI) requires a precise assessment of the brain lesions but also of potentially associated extra-cranial injuries. Children with severe TBI should be treated in a pediatric trauma center, if possible. Initial assessment relies mainly upon clinical examination, trans-cranial Doppler ultrasonography and body CT scan. Neurosurgical operations are rarely necessary in these patients, except in the case of a compressive subdural or epidural hematoma. On the other hand, one of the major goals of resuscitation in these children is aimed at protecting against secondary brain insults (SBI). SBI are mainly because of systemic hypotension, hypoxia, hypercarbia, anemia and hyperglycemia. Cerebral perfusion pressure (CPP = mean arterial blood pressure - intracranial pressure: ICP) should be monitored and optimized as soon as possible, taking into account age-related differences in optimal CPP goals. Different general maneuvers must be applied in these patients early during their treatment (control of fever, avoidance of jugular venous outflow obstruction, maintenance of adequate arterial oxygenation, normocarbia, sedation-analgesia and normovolemia). In the case of increased ICP and/or decreased CPP, first-tier ICP-specific treatments may be implemented, including cerebrospinal fluid drainage, if possible, osmotic therapy and moderate hyperventilation. In the case of refractory intracranial hypertension, second-tier therapy (profound hyperventilation with P(a)CO(2) < 35 mmHg, high-dose barbiturates, moderate hypothermia, decompressive craniectomy) may be introduced, after a new cerebral CT scan.
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PMID:Management of critically ill children with traumatic brain injury. 1831 8

Changes in the partial pressure of arterial CO2 (PaCO2) regulates cerebrovascular tone and dynamic cerebral autoregulation (CA). Elevations in PaCO2 also increases autonomic neural activity and may alter the arterial baroreflex. We hypothesized that hypercapnia would impair, and hypocapnia would improve, dynamic CA and that these changes would occur independently of any change in baroreflex sensitivity (BRS). In 10 healthy male subjects, incremental hypercapnia was achieved through 4-min administrations of 4% and 8% CO2. Incremental hypocapnia involved two 4-min steps of hyperventilation to change end-tidal PCO2, in an equal and opposite direction, to that incurred during hypercapnia. End-tidal, arterial and internal jugular vein PCO2 were sampled simultaneously at baseline and during each CO2 step. Dynamic CA and BRS was assessed at baseline and during each step change in PaCO2 using spectral and transfer-function analysis of beat-by-beat changes in mean arterial blood pressure (MAP), heart rate and flow velocity in the middle cerebral arterial (MCAv). Critical closing pressure (CCP), an estimate of cerebrovascular tone, was estimated from extrapolation of the MAP-MCAv waveforms. Hypercapnia caused a progressive increase in PaCO2 and MCAv whereas hypocapnia caused the opposite effect. Despite marked changes in CPP, there were no evident change in transfer-function gain, coherence, MAP variability or BRS; however, both MCAv variability and phase in the very-low frequency range was reduced during the most severe level of hyper- and hypocapnia (P < 0.05), and were related to elevations in ventilation (R2 = 0.42-0.52, respectively; P < 0.001). It seems that hyperventilation, rather than PaCO2, has an important influence on dynamic CA.
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PMID:Dynamic cerebral autoregulation and baroreflex sensitivity during modest and severe step changes in arterial PCO2. 1868 Jul 30