Effect of hypoxemia and ethacrynic acid on ABR and distortion product emission thresholds.

Various studies have shown that induction of hypoxemia in animals such that arterial blood oxygen tensions reach 20-30 mm Hg is accompanied by reversible threshold elevations of the auditory nerve-brain-stem evoked response (ABR). In this state, the endocochlear potential (EP) is depressed, causing a smaller potential difference across the hair cells and/or reduced activity of the cochlear amplifier of the outer hair cells. In order to test these possibilities, ABR threshold (an expression of the overall sensitivity of the cochlea) and changes in threshold of the cubic (2f1-f2) distortion product emissions (DPE) (an expression of activity of the cochlear amplifier) were measured in the same cats while the EP was depressed by hypoxemia or by ethacrynic acid. During the episodes of hypoxemia, DPE thresholds were elevated by 10 dB while ABR thresholds were elevated by 22.8 dB. Therefore, it seems that a normal EP is necessary both for normal cochlear transduction (inner hair cells) and for normal cochlear amplification (outer hair cells). The human fetus in utero is relatively hypoxic and there is evidence that its auditory threshold is also similarly elevated. Therefore the threshold elevation in the fetus in utero, estimated to be about 20 dB, is a consequence of both reduced transduction current through the inner hair cells (about 10 dB) and an additional 10 dB reduction in the activity of the cochlear amplifier of the outer hair cells.

Improvement in sensorineural auditory threshold of the guinea-pig fetus following delivery.

The human fetus in utero is hypoxic relative to the neonate due to differences between placental and pulmonary oxygenation. Comparable degrees of hypoxia induced in young and adult animals caused an elevation in hearing threshold of a sensorineural nature. It was hypothesised therefore that the human fetus may also have such an elevation of threshold. This was tested in this study by recording ABR thresholds to bone conducted stimuli in fetal guinea-pigs that were near full term and again in the same animals, after delivery and consequent pulmonary oxygenation. In every animal studied (n = 9), the neonatal threshold was better than that in the fetus. In those fetuses in which a response could be recorded (n = 5), the neonatal threshold was on average 20 dB better than in the fetus. These findings are probably due to a depression of the endocochlear potential induced by the relatively hypoxic state of the fetus. The hypoxic state would lead to a reduced transduction current in the hair cells in response to a stimulus and an elevated hearing threshold. At birth, with the shift to pulmonary oxygenation, the neonate becomes normoxic, the endocochlear potential rapidly reaches near maximal levels and threshold is improved.

Intracranial pressure and cerebral perfusion pressure in experimental streptococcus pneumoniae meningitis.

Clinical studies have demonstrated the prognostic importance of increased intracranial pressure in central nervous system infections. To delineate development of intracranial pressure in meningitis experiments were carried out in rabbits. Meningitis was induced by injecting streptococcus pneumoniae bacteria into the cisterna magna and blood, and intracranial pressures were continuously recorded. In the experimental model, three stages were seen: incubation period (0-8 h)--in which CSF becomes positive for the infecting organism and biochemical changes occur, but there are no hemodynamic or intracranial pressure changes; stage of slowly increasing intracranial pressure - because blood pressure remains normal, cerebral perfusion pressure is maintained adequate for cerebral metabolic need (9-24 h); terminal stage (greater than 25 h)--with hemodynamic collapse, critical reduction of cerebral perfusion pressure, cerebral ischemia, and death of the experimental animals. It is suggested that a similar sequence occurs in human disease. The clinical implication stresses the need for early recognition and treatment of intracranial hypertension as an important adjunct to antibiotic treatment of the infecting organism.

Gastrointestinal protein loss in children recovering from burns.

Qualitative gastrointestinal protein loss was evaluated in 10 children with second- and/or third-degree burns covering 10% or more of their body surface area (BSA) by using fecal alpha-1-antitrypsin (FA-1-AT) as a marker. Patients were subdivided according to the extent of the burned area: group I (5 patients) had burns covering less than 20% of BSA; group II (5 patients) had burns covering more than 20% of BSA (mean, 37.2% = 24.9%). Results were compared with those of 12 healthy normal controls. Mean maximal FA-1-AT excretion in group II patients (2.71 +/- 1.35 mg/g) was significantly greater than that found in group I children (0.43 +/- 0.26 mg/g; P = .006) and in the controls (0.62 +/- 0.25 mg/g; P = .004). The mean maximal FA-1-AT excretion positively correlated to the percent of BSA covered with burns (r = 0.83). Although the mean septic score (SS) of group I patients (7 +/- 2.9) was significantly greater than that calculated for group II children (3 +/- 2.45; P = .047), only 2 patients in group II had positive microbiological cultures. Patients in both groups had received more than the recommended enteral caloric and protein allowance during the 96 hours prior to the maximal FA-1-AT measurements. Within this range, no correlation was found between the amount of FA-1-AT and the number of calories per kilogram protein consumed. By using the method of FA-1-AT quantification, this study provides the first report on postburn intestinal protein loss in children.

Effect of endotracheal suctioning on arterial blood gases in children.

The occurrence of hypoxia during endotracheal tube suctioning and its prevention was examined in 25 hemodynamically stable and non-cyanosed pediatric patients. In each patient 4 suction and treatment protocols were studied: 1. pre- and post-suction arterial blood gases (ABG) with no treatment (control). 2. ABG with pre-suction oxygenation. 3. ABG with presuction hyperinflation. 4. ABG with postsuction hyperinflation. With no presuction treatment the PO2 and saturation fell significantly after suctioning from control level of 116.6 +/- 9.4 mmHg to 93 +/- 9.3 mmHg post-suction and 97.2 +/- 0.4% to 92.8 +/- 1.4% (p less than 0.001) respectively. In 6 patients with low but adequate pre-suction PO2, hypoxic levels (PO2 less than 60 mmHg) were found post-suction. The significant fall in PO2 was completely prevented by pre-suction oxygenation. Post-suction hyperinflation induced a rapid return of the PO2 to control levels. These results suggest that severe hypoxia might occur during endotracheal suctioning and can be prevented by pre-oxygenation. We recommend 1 min oxygenation with FiO2 1.0 prior to suctioning procedures and intermittent hyperinflation with 100% oxygen during repeated endotracheal suction passes to prevent hypoxia, especially in children in respiratory failure who already have low or borderline pre-suction PO2.

Auditory brain-stem (ABP) and somatosensory evoked potentials (SEP) in an animal model of a synaptic lesion: elevated plasma barbiturate levels.

Experiments were conducted to determine whether a consistent pattern of auditory nerve brain-stem evoked synaptic lesion model in cats (elevated levels of the lesion model in cats (elevated levels of the barbiturate thiopental). The ABP in response to low (10/sec) and high (80/sec) stimulus rates was recorded. In order to differentiate between the effects of the elevated drug levels on axonal propagation and on synaptic transmission, the early components of the somatosensory evoked potential (SEP) were also recorded, with particular attention to the first SEP wave, which is solely an axonal event without any intervening synapse. Calculations showed that the effect on synapses was 3.0-9.5 times greater than the effect of the drug on axonal propagation. As the level of barbiturates increased (representing a more severe synaptic lesion), the interpeak latencies of the ABP and the SEP became progressively prolonged, more so than the dependence of the first waves of both the ABP and the SEP on drug level. In general, amplitudes were not affected. At progressively elevated drug levels, higher stimulus repetition rates did not have an increasingly greater effect than lower rates on evoked response latencies and amplitudes so that this study also shows that the use of elevated stimulus rates does not hold much promise in the diagnosis of synaptic lesions.

Prolonged electrocerebral silent barbiturate coma in intractable seizure disorders.

Barbiturate coma (BC) is a known modality for terminating resistant convulsive status epilepticus. It is usually applied until seizure activity ends. We recently adopted a modified protocol of prolonged, electrocerebral silent BC to treat patients with chronic seizure activity resistant to multiple regimens of antiepileptic drugs. Four patients, aged 4 months to 10 years, with long-standing intractable generalized seizures were treated. Seizure frequency ranged from one to two to numerous times per day. Following BC, one patient has been seizure free during 8 months of follow-up, and another has had only two seizures in 18 months. A 4-month-old infant was seizure-free for 2 weeks after BC and then died from underlying CNS disease. A 10-year-old girl died during BC from shock and hyperpyrexia. The results obtained in our patients indicate that prolonged electrocerebral silent BC may exert a beneficial long-term effect in treatment of intractable seizure disorders. This procedure might also be beneficial in other forms of epilepsy.

Arhinia revisited.

Arhinia is a rare anomaly in which a total absence of the nose and parts of the olfactory system occurs. It is frequently associated with various multiple central nervous system (CNS) and somatic anomalies of different degrees of severity, with high mortality rate. Twelve cases that have been reported in the literature are analyzed according to multiple criteria. The anomalies that have been found to be associated with arhinia are: lack of olfactory bulbs and nerves, missing paranasal sinuses, high arched or cleft palate, various eye anomalies, low set ears - all in a very high incidence. Various degrees of CNS malformations have been found in part of the cases. Somatic anomalies have been reported in 50% of the cases. In two cases chromosome 9 anomalies have been reported. A classification is suggested in which arhinia is classified into arhinia (total absence of the nose and rhinencephalon) and partial arhinia (partial absence of the nose), each may or may not be associated with other malformations (facial, CNS and somatic).

Surgical treatment of infants with esophageal atresia and VATER association.

Our surgical experience in 10 infants with esophageal atresia and the VATER association of multiple congenital anomalies is reviewed. Early recognition and evaluation of the various lesions enabled the planning of a staged surgical approach with a satisfactory outcome. Seven of the patients survived. There were no immediate postoperative deaths. Development and growth curves of the surviving patients are satisfactory. Despite multiple operative procedures infants with VATER association may lead a reasonably normal life.

The depression of the auditory nerve-brain-stem evoked response in hypoxaemia--mechanism and site of effect.

During severe hypoxaemia in the cat the ABR was depressed in 2 different patterns: if mean arterial blood pressure (MAP) was maintained then all other evoked potentials (EPs--somatosensory and visual) remained. If MAP was not maintained, all of these EPs were depressed. This study sought to document these different patterns of ABR depression and to ascertain their mechanisms. When MAP fell, the ABR loss began with the later waves and progressed to the earlier waves. These are signs of a central brain lesion. The hypoxaemia, detrimental to normal function of the cardiovascular system, leads to depression of MAP, to a fall in cerebral perfusion pressure and blood flow, to cerebral ischaemia and ABR loss. On the other hand, when MAP was maintained, severe hypoxaemia was accompanied by a depression of all of the ABR waves at the same time. The cochlear microphonic potential was also simultaneously depressed. These are signs of a peripheral, cochlear effect similar to the demonstrated depression of the positive endocochlear resting potential of the scala media and of the cochlear microphonic potential during hypoxaemia. This leads to interference with the cochlear transduction mechanism so that all of the auditory evoked potentials, including the ABR, are simultaneously depressed. These results lead to the suggestion that the ABR abnormalities seen in patients who suffered a hypoxic (anoxic) insult or an ischaemic episode (prolonged interpeak latencies, loss of later waves and finally all waves absent or only the first wave remaining) is always due to ischaemia even when the initial insult was hypoxic.

Simultaneous superior and inferior vena cava pressure recordings in giant omphalocele repair--a possible guideline for prevention of postoperative circulatory complications.

Eleven children underwent second stage repair of giant omphaloceles containing the liver. Simultaneous SVC and IVC pressure before, during and after closure of the abdominal wall was recorded. In all patients with circulatory complications the SVC pressure decreased following surgery. The postoperative pressure ratios in IVC and SVC (Formula: see text) was found to be four times greater in the group with complications. It is suggested that this ratio might serve as an important index in the prediction of abdominal wall closure feasibility in giant omphaloceles.

Multiple hornet stings with features of Reye's syndrome.

Hornet's venom is known to possess a variety of toxic effects. A 19-mo-old girl who developed a Reye-like syndrome following multiple stings by the Oriental hornet (Vespa orientalis) is described. She presented with encephalopathy associated with hepatomegaly, elevated transaminase levels, low prothrombin time, and hyperammonemia. Liver biopsy demonstrated microvesicular fatty infiltration and diffuse mitochondrial changes. Additional features were acute renal tubular necrosis and massive hemolysis.

Scorpion sting in children. A review of 51 cases.

Scorpion sting in children is a hazardous and potentially lethal condition. Fifty-one infants and children were admitted to the Pediatric Departments at the Hadassah-Hebrew University Hospitals in Jerusalem, during a 5-year period, following scorpion sting. Fifteen (29.4%) had severe systemic signs of envenomation and two (3.9%) died. Analysis of our data showed that patients with severe toxicity were brought to the hospital after a significantly longer time lapse than were the patients with mild-to-moderate symptoms. The current management of children with scorpion envenomation consists of administration of specific antivenom and close surveillance in an intensive care unit, where vital signs and continuous cardiac monitoring enable early initiation of therapy for life-threatening complications, such as cardiac and respiratory failure, convulsions, or hypertension.

Scoring system to assess disease severity in children.

A scoring system to assess disease severity in children, based on therapeutic and diagnostic interventions, is suggested. The charts of 475 consecutive admissions to a multidisciplinary pediatric intensive care unit (PICU) were reviewed and therapeutic and diagnostic interventions (TDI) associated with more than 20% mortality identified. These were scored: TDI associated with 20-30% mortality - 1 point; 31-40% - 2 points; 41-50% - 3 points and more than 51% - 4 points. According to these values, a Pediatric Therapeutic and Diagnostic Intervention Score (PTDIS) was calculated for each patient. The study population may be divided, according to PTDIS and mortality, into three groups: moderately severe disease associated with up to 2.7% mortality and PTDIS less than 20; severe disease associated with up to 25% mortality and PTDIS less than 35; critically ill patients with more than 50% mortality and PTDIS greater than 36. PTDIS in survivors was 15.2 +/- 0.6 (mean +/- SE) and 43.6 +/- 1.1 in non-survivors. Pearson's correlation between PTDIS and mortality was R = 0.7162 at a significance level of p less than 0.0001. PTDIS and mortality were not found to be significantly correlated with sex, age or duration of hospitalization in the Unit. Sepsis, central nervous system infections and burns were the primary diseases, and shock, coma and patients after cardiopulmonary resuscitation the indications for admission to the Unit, associated with the highest mortality and PTDIS. This study demonstrates the efficacy of the suggested PTDIS system in accurately assessing severity of disease in a PICU patient population.

An unusual case of non-traumatic pneumococcal mediastinal abscess.

A 16-month old baby developed severe respiratory failure because of acute laryngitis and required mechanical ventilation. Intubation was complicated by aspiration and development of chemical pneumonia. Following 4 days of treatment the child was successfully extubated. Thirty six hours after extubation the patient again developed respiratory failure and on chest X-ray pneumomediastinum was seen and later evidence of a mediastinal abscess. Conservative treatment, with antibiotics, effected complete cure.

Pericardial tamponade complicating central venous catheterization in a newborn infant.

Complications of central venous catheterizations are divided into immediate or early complications such as haematoma, pneumothorax and haemothorax, and late complications such as infection and venous thrombosis. One of the rare but life-threatening complications of central venous catheterization is pericardial tamponade. We review the literature and add an additional case, the first reported in a newborn infant.