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Biomedical subjects

C D Kurth

Publications and source records attributed to C D Kurth.

At least 19 recordsLinked to original sources
PubMed2001

Impact of inspired gas mixtures on preoperative infants with hypoplastic left heart syndrome during controlled ventilation.

BACKGROUND: Management strategies for preoperative infants with hypoplastic left heart syndrome (HLHS) include increased inspired nitrogen (hypoxia) and increased inspired carbon dioxide (hypercarbia). There are no studies directly comparing these 2 therapies in humans. This study compares the impact of hypoxia versus hypercarbia on oxygen delivery, under conditions of fixed minute ventilation. METHODS AND RESULTS: Ten anesthetized and paralyzed preoperative infants with HLHS were evaluated in a prospective, randomized, crossover trial comparing hypoxia (17% FIO(2)) with hypercarbia (2.7% FICO(2)). Each patient was treated in a random order (10 minutes per condition) with a recovery period (15 to 20 minutes) in room air. Arterial (SaO(2)) and superior vena caval (SvO(2)) co-oximetry and cerebral oxygen saturation (ScO(2)) measurements were made at the end of each condition and recovery period. ScO(2) was measured by near infrared spectroscopy. Hypoxia significantly decreased both SaO(2) (-5.2+/-1.1%, P=0.0014) and SvO(2) (-5.6+/-1.7%, P=0.009) compared with baseline, but arteriovenous oxygen saturation (AVO(2)) difference (SaO(2)-SvO(2)) and ScO(2) remained unchanged. Hypercarbia decreased SaO(2) (-2.6+/-0.6%, P=0.002) compared with baseline but increased both ScO(2) (9.6+/-1.8%, P=0.0001) and SvO(2) (6+/-2.2%, P=0.022) and narrowed the AVO(2) difference (-8.5+/-2.3%, P=0.005). Both hypoxia and hypercarbia decreased the balance between pulmonary and systemic blood flow (Qp:Qs) compared with baseline. CONCLUSIONS: In preoperative infants with HLHS, under conditions of anesthesia and paralysis, although Qp:Qs falls in both conditions, oxygen delivery is unchanged during hypoxia and increased during hypercarbia. These data cannot differentiate cerebral from systemic oxygen delivery.

Administration, Inhalation↗
PubMed2001

Cerebral oxygen saturation before congenital heart surgery.

BACKGROUND: In congenital heart disease (CHD), neurologic abnormalities suggestive of hypoxia-ischemia are often apparent before cardiac surgery. To evaluate preoperative cerebral oxygenation, this study determined cerebral O2 saturation (ScO2) in CHD and healthy children. METHODS: Ninety-one CHD and 19 healthy children aged less than 7 years were studied before surgical or radiologic procedures. Arterial saturation (SaO2) and ScO2 were measured by pulse-oximetry and near infrared cerebral oximetry. Cerebral O2 extraction (CEO2) was calculated (SaO2-ScO2). SaO2, ScO2, and CEO2 were compared among diagnoses. Multivariable regression was performed between ScO2 and clinical variables. RESULTS: In healthy subjects, ScO2 (68%+/-10%) and CEO2 (30%+/-11%) were similar to patients with ventricular septal defect, aortic coarctation, and single ventricle after Fontan operation. ScO2 was significantly decreased in patients with patent ductus arteriosus (53%+/-8%), tetralogy of Fallot (57%+/-12%), hypoplastic left heart syndrome (46%+/-8%), pulmonary atresia (38%+/-6%), and single ventricle after aortopulmonary shunt (50%+/-7%), or bidirectional Glenn operation (43%+/-6%). CEO2 was significantly different only in patent ductus arteriosus (46%+/-8%) and hypoplastic left heart syndrome (38%+/-12%). In multivariable regression, only SaO2 was related to ScO2 (R = 0.63, p < 0.001). CONCLUSIONS: Cerebral oxygenation in CHD varies with anatomy and arterial saturation, and in some patients, it is very low compared with healthy subjects.

Brain Ischemia↗
PubMed2001

Comparison of neurologic outcome after deep hypothermic circulatory arrest with alpha-stat and pH-stat cardiopulmonary bypass in newborn pigs.

OBJECTIVE: Deep hypothermic circulatory arrest for neonatal heart surgery poses the risk of brain damage. Several studies suggest that pH-stat management during cardiopulmonary bypass improves neurologic outcome compared with alpha-stat management. This study compared neurologic outcome in a survival piglet model of deep hypothermic circulatory arrest between alpha-stat and pH-stat cardiopulmonary bypass. METHODS: Piglets were randomly assigned to alpha-stat (n = 7) or pH-stat (n = 7) cardiopulmonary bypass, cooled to 19 degrees C brain temperature, and subjected to 90 minutes of deep hypothermic circulatory arrest. After bypass rewarming/reperfusion, they survived 2 days. Neurologic outcome was assessed by neurologic performance (0-95, 0 = no deficit and 95 = brain death) and functional disability scores, as well as histopathology. Arterial pressure, blood gas, glucose, and brain temperature were recorded before, during, and after bypass. RESULTS: All physiologic data during cardiopulmonary bypass were similar between groups (pH-stat vs alpha-stat) except arterial pH (7.06 +/- 0.03 vs 7.43 +/- 0.09, P <.001) and arterial PCO (2) (98 +/- 8 vs 36 +/- 8 mm Hg, P <.001). No differences existed in duration of cardiopulmonary bypass or time to extubation. Performance was better in pH-stat versus alpha-stat management at 24 hours (2 +/- 3 vs 29 +/- 17, P = 0.004) and 48 hours (1 +/- 2 vs 8 +/- 9, P =.1). Also, functional disability was less severe with pH-stat management at 24 hours (P =.002) and 48 hours (P =.053). Neuronal cell damage was less severe with pH-stat versus alpha-stat in the neocortex (4% +/- 2% vs 15% +/- 7%, P <.001) and hippocampal CA1 region (11% +/- 5% vs 33% +/- 25%, P =.04), but not in the hippocampal CA3 region (3% +/- 5% vs 16% +/- 23%, P =.18) or dentate gyrus (1% +/- 1% vs 3% +/- 6%, P =.63). CONCLUSIONS: pH-stat cardiopulmonary bypass management improves neurologic outcome with deep hypothermic circulatory arrest compared with alpha-stat bypass. The mechanism of protection is not related to hemodynamics, hematocrit, glucose, or brain temperature.

Animals↗
PubMed2001

A comparison of oral clonidine and oral midazolam as preanesthetic medications in the pediatric tonsillectomy patient.

UNLABELLED: We compared the effects of oral clonidine (4 microg/kg) and midazolam (0.5 mg/kg) on the preanesthetic sedation and postoperative recovery profile in children during tonsillectomy with or without adenoidectomy. In a double-blinded, double-dummy study design, 134 ASA physical status I-II children aged 4-12 yr were randomized to receive a combination of either clonidine and placebo (Group A), or placebo and midazolam (Group B) at 60-90 min and 30 min, respectively, before the induction of anesthesia. Children in the clonidine group exhibited more intense anxiety on separation and during induction of anesthesia via a mask as measured by the modified Yale Preoperative Anxiety Scores. They also had significantly lower mean intraoperative arterial blood pressures, shorter surgery, anesthesia, and emergence times, and a decreased need for supplemental oxygen during recovery compared with the midazolam group. However, the clonidine group had larger postoperative opioid requirements, maximum excitement and pain scores based on the Children's Hospital of Eastern Ontario scale in the Phase 1 postanesthetic care unit. There were no differences between the two groups in the times to discharge readiness, postoperative emesis, unanticipated hospital admission rates, postdischarge maximum pain scores, and 24 h analgesic requirements. The percentage of parents who were completely satisfied with the child's preoperative experience was significantly higher in the midazolam group. There were no differences in parental satisfaction with the recovery period. We conclude that under the conditions of this study, oral midazolam is superior to oral clonidine as a preanesthetic medication in this patient population. IMPLICATIONS: We compared preanesthetic sedation and postoperative recovery after oral clonidine (4 microg/kg) and midazolam (0.5 mg/kg) in children during tonsillectomy. The clonidine group had greater preoperative anxiety and shorter surgery and anesthesia times, but required more postoperative analgesia. Delayed recovery and discharge times did not differ. Midazolam was superior to clonidine as oral preanesthetic medication for these patients.

Adenoidectomy↗
PubMed2001

A randomized multicenter study of remifentanil compared with halothane in neonates and infants undergoing pyloromyotomy. I. Emergence and recovery profiles.

UNLABELLED: Pyloric stenosis is sometimes associated with hemodynamic instability and postoperative apnea. In this multicenter study we examined the hemodynamic response and recovery profile of remifentanil and compared it with that of halothane in infants undergoing pyloromyotomy. After atropine, propofol, and succinylcholine administration and tracheal intubation, patients were randomized (2:1 ratio) to receive either remifentanil with nitrous oxide and oxygen or halothane with nitrous oxide and oxygen as the maintenance anesthetic. Pre- and postoperative pneumograms were done and evaluated by an observer blinded to the study. Intraoperative hemodynamic data and postanesthesia care unit (PACU) discharge times, PACU recovery scores, pain medications, and adverse events (vomiting, bradycardia, dysrhythmia, and hypoxemia) were recorded by the study's research nurse. There were no significant differences in patient age or weight between the two groups. There were no significant differences in hemodynamic values between the two groups at the various intraoperative stress points. The extubation times, PACU discharge times, pain medications, and adverse events were similar for both groups. No patient anesthetized with remifentanil who had a normal preoperative pneumogram had an abnormal postoperative pneumogram, whereas three patients with a normal preoperative pneumogram who were anesthetized with halothane had abnormal pneumograms after. IMPLICATIONS: The use of ultra-short-acting opioids may be an appropriate technique for infants less than 2 mo old when tracheal extubation after surgery is anticipated.

Analgesics, Opioid↗
PubMed2001

A randomized multicenter study of remifentanil compared with halothane in neonates and infants undergoing pyloromyotomy. II. Perioperative breathing patterns in neonates and infants with pyloric stenosis.

UNLABELLED: Although former preterm birth infants are at risk for postoperative apnea after surgery, it is unclear whether the same is true of full-term birth infants. We evaluated the incidence of apnea in 60 full-term neonates and infants undergoing pyloromyotomy both before and after anesthesia. All subjects were randomized to a remifentanil- or halothane-based anesthetic. Apnea was defined by the presence of prolonged apnea (>15 s) or frequent brief apnea, as observed on the pneumocardiogram. Apnea occurred before surgery in 27% of subjects and after surgery in 16% of subjects, with no significant difference between subjects randomized to remifentanil or halothane anesthesia. This apnea was primarily central in origin, occurred throughout the recording epochs, and was associated with severe desaturation in some instances. Of the subjects with normal preoperative pneumocardiograms, new onset postoperative apnea occurred in 3 (23%) of 13 subjects who received halothane-based anesthetics versus 0 (0%) of 22 subjects who received remifentanil-based anesthetics (P = 0.04). Thus, postoperative apnea can follow anesthesia in otherwise healthy full-term infants after pyloromyotomy and is occasionally severe with desaturation. New-onset postoperative apnea was not seen with a remifentanil-based anesthetic. IMPLICATIONS: Abnormal breathing patterns can follow anesthesia in infants after surgical repair of pyloric stenosis. Occasionally, these patterns can be associated with desaturation. New-onset postoperative apnea was not seen with a remifentanil-based anesthetic.

Anesthetics, Inhalation↗
PubMed2001

Desflurane confers neurologic protection for deep hypothermic circulatory arrest in newborn pigs.

BACKGROUND: Cardiopulmonary bypass (CPB) and deep hypothermic circulatory arrest (DHCA), as used for infant heart surgery, carry a risk of ischemic neurologic injury. Volatile anesthetics have neuroprotective properties against both global and focal ischemia at normothermia. The authors examined the hemodynamic and neuroprotective effects of desflurane in a piglet CPB-DHCA model. METHODS: Twenty piglets aged 5-10 days received a desflurane- (6-9% expired) or fentanyl-based anesthetic before and during CPB (before and after DHCA). DHCA lasted 90 min at 19 degrees C brain. Cardiovascular variables (heart rate, arterial pressure, blood gases, glucose, brain temperature) were monitored. On postoperative day 2, neurologic and histologic outcomes were determined. RESULTS: Cardiovascular variables before, during, and after CPB were physiologically similar between groups. The desflurane group had better neurologic performance (P = 0.023) and greater postoperative weight gain (P = 0.04) than the fentanyl group. In neocortex, the desflurane group had less tissue damage (P = 0.0015) and fewer dead neurons (P = 0.0015) than the fentanyl group. Hippocampal tissue damage was less in the desflurane group (P = 0.05), but overall, neuronal cell counts in the CA1 sector of the right hippocampus were similar to those in the fentanyl group. CONCLUSIONS: Desflurane-based anesthesia yields hemodynamics during CPB with DHCA that are similar to those with fentanyl-based anesthesia. However, desflurane-based anesthesia improves neurologic and histologic outcomes of CPB-DHCA in comparison with outcomes with fentanyl-based anesthesia.

Anesthetics, Inhalation↗
PubMed2000

A randomized, double-blinded study of remifentanil versus fentanyl for tonsillectomy and adenoidectomy surgery in pediatric ambulatory surgical patients.

UNLABELLED: We compared, in a double-blinded manner, the anesthetic maintenance and recovery properties of remifentanil with a clinically comparable fentanyl-based anesthetic technique in pediatric ambulatory surgical patients. Anesthesia was induced with either halothane or sevoflurane and nitrous oxide and oxygen. Patients were randomized (computer generated) to receive either remifentanil or fentanyl in a blinded syringe with nitrous oxide and oxygen in one of four possibilities: halothane/remifentanil, halothane/fentanyl, sevoflurane/remifentanil or sevoflurane/fentanyl. In patients receiving remifentanil, a placebo bolus was administered, and a continuous infusion (0.25 microg. kg(-1). min(-1)) was begun. In patients receiving fentanyl, a bolus (2 microg/kg) was administered followed by a placebo continuous infusion. The time from discontinuation of the anesthetic to extubation, discharge from the postanesthesia care unit (PACU), and discharge to home, as well as pain scores, were assessed by a blinded nurse observer. Systolic blood pressure and heart rate were noted at selected times, and adverse events were recorded. Remifentanil provided faster extubation times and higher pain-discomfort scores. PACU and hospital discharge times were similar. There were no statistical differences among the groups for adverse events. There were statistically, but not clinically, significant differences in hemodynamic variables. We noted that continuous infusions of remifentanil were intraoperatively as effective as bolus fentanyl. Although patients could be tracheally extubated earlier with remifentanil, this did not translate to earlier PACU or hospital discharge times. In addition, remifentanil was associated with higher postoperative pain scores. The frequent incidence of postoperative pain observed in the postoperative recovery room suggests that better intraoperative prophylactic analgesic regimens for postoperative pain control are necessary to optimize remifentanil's use as an anesthetic for children. IMPLICATIONS: This is a study designed to examine the efficacy and safety of a short-acting opioid, remifentanil, when used in pediatric patients. The frequent incidence of postoperative pain observed in the postoperative recovery room suggests that better intraoperative prophylactic analgesic regimens for postoperative pain control are necessary to optimize remifentanil's use as an anesthetic for children.

Adenoidectomy↗
PubMed2000

Anesthesia for fetoscopic fetal surgery: twin reverse arterial perfusion sequence and twin-twin transfusions syndrome.

IMPLICATIONS: Twin reversed arterial perfusion sequence and twin-twin transfusion syndrome can be managed by fetoscopic fetal surgery. It is important to consider the fetal, uteroplacental, and maternal issues when choosing an anesthetic technique. We report on three patients with differing anesthetic issues using fetoscopic surgery for umbilical cord coagulation.

Adult↗
PubMed2000

Arterial and venous contributions to near-infrared cerebral oximetry.

BACKGROUND: Cerebral oximetry is a noninvasive bedside technology using near-infrared light to monitor cerebral oxygen saturation (Sco2) in an uncertain mixture of arteries, capillaries, and veins. The present study used frequency domain near-infrared spectroscopy to determine the ratio of arterial and venous blood monitored by cerebral oximetry during normoxia, hypoxia, and hypocapnia. METHODS: Twenty anesthetized children aged < 8 yr with congenital heart disease of varying arterial oxygen saturation (Sao2) were studied during cardiac catheterization. Sco2, Sao2, and jugular bulb oxygen saturation (Sjo2) were measured by frequency domain near-infrared spectroscopy and blood oximetry at normocapnia room air, normocapnia 100% inspired O2, and hypocapnia room air. RESULTS: Among subject conditions, Sao2 ranged from 68% to 100%, Sjo2 from 27% to 96%, and Sco2 from 29% to 92%. Sco2 was significantly related to Sao2 (y = 0. 85 x -17, r = 0.47), Sjo2 (y = 0.77 x +13, r = 0.70), and the combination (Sco2 = 0.46 Sao2 + 0.56 Sjo2 - 17, R = 0.71). The arterial and venous contribution to cerebral oximetry was 16 +/- 21% and 84 +/- 21%, respectively (where Sco2 = alpha Sao2 + beta Sjo2 with alpha and beta being arterial and venous contributions). The contribution was similar among conditions but differed significantly among subjects (range, approximately 40:60 to approximately 0:100, arterial:venous). CONCLUSIONS: Cerebral oximetry monitors an arterial/venous ratio of 16:84, similar in normoxia, hypoxia, and hypocapnia. Because of biologic variation in cerebral arterial/venous ratios, use of a fixed ratio is not a good method to validate the technology.

Brain↗
PubMed2000

Use of intranasal fentanyl in children undergoing myringotomy and tube placement during halothane and sevoflurane anesthesia.

BACKGROUND: Many children are restless, disoriented, and inconsolable immediately after bilateral myringotomy and tympanosotomy tube placement (BMT). Rapid emergence from sevoflurane anesthesia and postoperative pain may increase emergence agitation. The authors first determined serum fentanyl concentrations in a two-phase study of intranasal fentanyl. The second phase was a prospective, placebo-controlled, double-blind study to determine the efficacy of intranasal fentanyl in reducing emergence agitation after sevoflurane or halothane anesthesia. METHODS: In phase 1, 26 children with American Society of Anesthesiologists (ASA) physical status I or II who were scheduled for BMT received intranasal fentanyl, 2 microg/kg, during a standardized anesthetic. Serum fentanyl concentrations in blood samples drawn at emergence and at postanesthesia care unit (PACU) discharge were determined by radioimmunoassay. In phase 2, 265 children with ASA physical status I or II were randomized to receive sevoflurane or halothane anesthesia along with either intranasal fentanyl (2 microg/kg) or saline. Postoperative agitation, Children's Hospital of Eastern Ontario Pain Scale (CHEOPS) scores, and satisfaction of PACU nurses and parents with the anesthetic technique were evaluated. RESULTS: In phase 1, the mean fentanyl concentrations at 10 +/- 4 min (mean +/- SD) and 34 +/- 9 min after administering intranasal fentanyl were 0.80 +/- 0.28 and 0.64 +/- 0.25 ng/ml, respectively. In phase 2, the incidence of severe agitation, highest CHEOPS scores, and heart rate in the PACU were decreased with intranasal fentanyl. There were no differences between sevoflurane and halothane in these measures and in times to hospital discharge. The incidence of postoperative vomiting, hypoxemia, and slow respiratory rates were not increased with fentanyl. CONCLUSIONS: Serum fentanyl concentrations after intranasal administration exceed the minimum effective steady state concentration for analgesia in adults. The use of intranasal fentanyl during halothane or sevoflurane anesthesia for BMT is associated with diminished postoperative agitation without an increase in vomiting, hypoxemia, or discharge times.

Administration, Intranasal↗
PubMed2000

Neonatal cerebral oxygen regulation after hypothermic cardiopulmonary bypass and circulatory arrest.

OBJECTIVE: Despite technical advances, neurologic sequelae continue to occur in neonates after heart surgery using deep hypothermic cardiopulmonary bypass (dhCPB) and circulatory arrest (DHCA). This study sought to determine the cerebral microcirculatory responses to hypoxia, hypotension, hypocapnia, and hypercapnia after dhCPB and DHCA. DESIGN: Prospective laboratory animal trial. SETTING: Research laboratory. SUBJECTS: Twenty-eight newborn pigs. INTERVENTIONS: Piglets were divided into control, dhCPB, and DHCA groups. The control group received surgery. The dhCPB group received surgery and deep hypothermic CPB for 40 mins. The DHCA group received surgery, deep hypothermic CPB for 40 mins, and circulatory arrest for 60 mins. Two hours after the intervention, cerebral microcirculatory responses were examined. MEASUREMENTS AND MAIN RESULTS: Cerebral microcirculatory responses consisted of changes in cerebral oxygen saturation (Sco2) and pial arteriolar diameter measured by near- infrared spectroscopy and intravital microscopy, respectively. All groups experienced similar decreases in Sco2 and increases in pial arteriolar diameter in response to moderate and severe hypoxia (Pao2, 35 and 25 torr, respectively) and moderate and severe hypotension (mean pressure, 30 and 20 mm Hg, respectively). Sco2 and pial arteriolar diameter decreased to hypocapnia (Paco2, 25 torr) similarly in all groups. To hypercapnia (Paco2, 70 torr), Sco2 increased in the control group, did not change in the dhCPB group, and decreased in the DHCA group. Pial arteriolar diameter to hypercapnia increased in the control and the dhCPB groups but did not change in the DHCA group. CONCLUSIONS: Cerebral vascular and oxygenation responses to hypoxia, hypocapnia, and hypotension were preserved after dhCPB and 1 hr of DHCA. By comparison, cerebral vascular and oxygenation responses to hypercapnia were not; both vascular and oxygenation responses were altered after DHCA, but only the oxygenation response was altered after dhCPB. These data suggest a selective disturbance in the microcirculation and/or parenchymal oxygen metabolism after DHCA and dhCPB.

Animals↗
PubMed1999

Regional patterns of neuronal death after deep hypothermic circulatory arrest in newborn pigs.

OBJECTIVES: Deep hypothermic circulatory arrest (DHCA) widely used during neonatal heart surgery, carries a risk of brain damage. In adult normothermic ischemia, brain cells in certain regions die, some by necrosis and others by apoptosis (programmed cell death). This study characterized regional brain cell death after DHCA in newborn pigs. METHODS: Eighteen piglets underwent 90 minutes of DHCA and survived 6 hours, 2 days, or 1 week. Six piglets underwent surgery alone or deep hypothermic cardiopulmonary bypass and survived 2 days. Three piglets received no intervention (control). Brain injury was assessed by neurologic and histologic examination and correlated with perioperative factors. Apoptosis and necrosis were identified by light microscopic analysis of cell structure and in situ DNA fragmentation (TUNEL). RESULTS: All groups subjected to DHCA had brain injury by neurologic and histologic examination, whereas the other groups did not. DHCA damaged neurons in the neocortex and hippocampus and occasionally in the striatum and cerebellum. Damaged neurons in the neocortex were mainly apoptotic and in the hippocampus, a mixture of necrotic and apoptotic neurons. Apoptosis and necrosis were apparent in all DHCA groups even though neurologic deficits improved over the week's survival. Neocortical and hippocampal damage correlated with blood glucose, hematocrit, and arterial PO(2) during and after cardiopulmonary bypass. CONCLUSIONS: In neonates, neocortical and hippocampal neurons are selectively vulnerable to death after DHCA. Both apoptosis and necrosis contribute to neuronal death, beginning early in reperfusion and continuing for days. These data suggest the need for several neuroprotective strategies tailored to the region and death process, initiated during the operation and continued after the operation.

Analysis of Variance↗
PubMed1999

Anesthetic considerations for fetal surgery.

This article outlines the perioperative management of the parturient who presents for fetal surgery. Anesthetic considerations include the physiological changes of pregnancy, preterm labor, the consequences of tocolytic drugs, maternal and fetal anesthesia, and postoperative analgesia.

Anesthesia↗
PubMed1999

A multiwavelength frequency-domain near-infrared cerebral oximeter.

This study tests a multiwavelength frequency-domain near-infrared oximeter (fdNIRS) in an in vitro model of the human brain. The model is a solid plastic structure containing a vascular network perfused with blood in which haemoglobin oxygen saturation (SO2) was measured by co-oximetry, providing a standard for comparison. Plastic shells of varying thickness (0.5-2 cm), with a vascular network of their own and encircling the brain model, were also added to simulate extracranial tissues of the infant, child and adult. The fdNIRS oximeter utilizes frequency-domain technology to monitor phaseshifts at 754 nm, 785 nm and 816 nm relative to a 780 nm reference to derive SO2 through photon transport and Beer-Lambert equations. We found a linear relationship between fdNIRS SO2 and co-oximetry SO2 with excellent correlation (r2 > or = 0.95) that fitted the line of identity in all experiments (n = 7). The bias of fdNIRS oximetry was -2% and the precision was 6%. Blood temperature and fdNIRS source-detector distance did not affect fdNIRS oximetry. Low haemoglobin concentration (6 g dl(-1)) altered the fdNIRS versus co-oximetry line slope and intercept, producing a 15% error at the extremes of SO2. The infant- and child-like shells overlying the brain model did not alter fdNIRS oximetry, whereas the adult-like shell yielded an error as high as 32%. In conclusion, fdNIRS accurately measures SO2 in an in vitro brain model, although low haemoglobin concentration and extracranial tissue of adult thickness influence accuracy.

Brain↗
PubMed1998

Anesthesia for the micropremie.

Providing anesthesia for the micropremie involves many considerations beyond what is needed for the full-term neonate. Immaturity of the airway, lungs, cardiovascular system, liver, kidneys, and central nervous system makes the micropremie susceptible to anesthestic complications. Immature respiratory mechanisms and respiratory control increase the risk of apnea, hypoxemia, and hypercapnia intraoperatively as well as postoperatively. Anesthetic drugs depress myocardial contractility and impair baroreflexes in the micropremie to increase the risk of hypotension during anesthesia. Drug metabolism in the micropremie is slow because of the immature liver and kidneys. The micropremie brain requires less drug to achieve the anesthetized state. As a result, administration of the dose and timing of anesthetic drugs differs in the micropremie compared with the full-term neonate. This article describes anesthetic considerations for a few surgical prodedures common in the micropremie.

Anesthesia↗