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Biomedical subjects

N Kissoon

Publications and source records attributed to N Kissoon.

At least 55 records · Page 3Linked to original sources
PubMed1994

Pharmacokinetics from multiple intraosseous and peripheral intravenous site injections in normovolemic and hypovolemic pigs.

OBJECTIVES: To examine: a) the rate and extent of delivery of radioactive tracers to the central circulation from the tibial, medial malleolar, distal femoral, and humeral intraosseous sites, as well as from a peripheral intravenous site; and b) the end-tidal CO2 response to injected sodium bicarbonate at these sites. DESIGN: Prospective, descriptive study. SETTING: Animal laboratory at a university medical center. SUBJECTS: Twenty anesthetized and mechanically ventilated piglets were cannulated with 18-gauge bone marrow needles at intraosseous sites and 22-gauge Teflon catheters in peripheral veins. A 22-gauge angiocath was placed in the right carotid artery of each subject. Drug kinetics were studied in the normovolemic and hypovolemic (acute bleeding of 25 mL/kg) states. INTERVENTIONS: Sodium bicarbonate (1 mEq/kg) was injected into each of the three intraosseous and one intravenous sites with simultaneous monitoring of end-tidal CO2. A 10-min period for stabilization was allowed between injections. Aliquots of 99mtechnetium were injected at randomly selected sites and blood samples were obtained at 1.5-sec intervals via carotid artery for radioactive counts. Experiments were repeated after withdrawal of 25 mL/kg of blood. MEASUREMENTS AND MAIN RESULTS: Assessment by end-tidal CO2 monitoring after 1-mEq/kg injections of bicarbonate demonstrated a mean initial end-tidal CO2 increase at 12.8 secs and a mean maximal end-tidal CO2 increase of 8 torr (1.06 kPa), with no significant site differences noted. Radioactive tracer injections were detected in the carotid artery after 15.4 secs in normovolemic animals and after 21.4 secs in hypovolemic animals, with no significant site differences detected. The proportion of injected tracer at 2, 5, 10, 20, 30, and 40 mins identified no significant differences between various intraosseous and intravenous sites. CONCLUSIONS: Our study demonstrated similar rapid transit and proportion of bicarbonate and radioactive tracers, reaching the central circulation from multiple intraosseous sites and a peripheral intravenous site. This finding suggests that adjustments in drug dosage may not be required, using various intraosseous locations as an alternative to peripheral intravenous drug therapy.

Animals↗
PubMed1994

Comparison of pH and carbon dioxide tension values of central venous and intraosseous blood during changes in cardiac output.

OBJECTIVE: To compare the pH and PCO2 values determined from of simultaneously corrected samples of central venous and intraosseous blood during sequential changes in cardiac output. DESIGN: Prospective, descriptive study. SETTING: An animal laboratory in a university medical center. SUBJECTS: Fourteen mixed breed 4-wk-old piglets. INTERVENTIONS: Animals were anesthetized with ketamine hydrochloride and neuromuscular blockade was induced by the administration of pancuronium bromide. After endotracheal intubation and the institution of mechanical ventilation, a 4-Fr pulmonary artery catheter and a carotid artery cannula were inserted via a cutdown into the right neck of each piglet. A 16-gauge intraosseous needle was inserted into the anteromedial surface of the right tibia. MEASUREMENTS AND MAIN RESULTS: Central venous and intraosseous blood gas samples were obtained simultaneously with thermodilution cardiac output measurements. Cardiac output measurements were as follows: during steady state (0.80 +/- 0.14 L/min), after volume loading of 15 mL/kg (1.00 +/- 0.25 L/min), after three successive bleeds of 15 mL/kg each at 30-min intervals (0.70 +/- 0.28, 0.54 +/- 0.22, and 0.43 +/- 0.16 L/min, respectively) and at exsanguination (unrecordable). Paired t-tests demonstrated no significant differences in pH and PCO2 values between intraosseous and central venous samples under all study conditions. Limits of agreement for difference in PCO2 between sites, within the range of cardiac outputs studied, were -12.86 to 11.38 torr (-1.71 to 1.46 kPa) and for pH were -0.09 to 0.15. CONCLUSIONS: Intraosseous blood samples can be obtained without difficulty even during extreme hypovolemia. The pH and PCO2 values of intraosseous and central venous blood samples were similar under all study conditions. Intraosseous blood may be a useful alternative to central venous blood to assess tissue acid-base status during hemorrhagic shock and other low-flow states.

Animals↗
PubMed1994

Transtracheal Doppler in infants and small children following surgery for congenital heart disease: rational use of an improved technology.

OBJECTIVE: To compare measurements of cardiac output utilizing an improved transtracheal Doppler technology with measurements obtained using two-dimensional echocardiography. DESIGN: Prospective, descriptive study. SETTING: Cardiovascular intensive care unit at a university medical center. PATIENTS: Fourteen children ranging in age from 14 days to 3 yrs (mean 1.3 +/- .97 yrs) following surgery for complex congenital heart disease. INTERVENTIONS: Simultaneous cardiac output determinations using transtracheal Doppler and two-dimensional echocardiography were compared. Cardiac output was determined using measurement of blood velocity and diameter of the ascending aorta following surgery. Direct aortic diameter measurements made at operation were compared with measurements obtained by transtracheal Doppler, two-dimensional echocardiography and angiography. RESULTS: The mean difference in aortic root diameter between measurements made directly at operation and transtracheal Doppler was 5%, compared with 13% by two-dimensional echocardiography, and 21% by angiography, a significant difference by analysis of variance (F[3,31],p < .007). Post hoc comparisons demonstrated significant (p < .05) differences between echocardiography and angiographic aortic diameters. The mean difference between transtracheal Doppler and echocardiographic determination of cardiac output was 10.9% (t[10] = -1.37, p = .007). CONCLUSIONS: An improved transtracheal Doppler technology compares favorably with echocardiographic determination of cardiac output in infants and young children. This improved technology may provide a useful means to assess cardiac output and may allow titration of therapy in critically ill infants and children.

Aftercare↗
PubMed1994

The utility of autopsies in a pediatric emergency department.

The role of the autopsy in verifying clinical diagnosis and as a quality assurance tool in pediatric emergency medicine has not been studied. We reviewed the charts of all children who died soon after arriving at to the pediatric emergency department between October 1985 and December 1989. Opinions as to clinical diagnoses and cause of death were obtained by presenting a summary of patient data, in a blinded fashion, to three emergency pediatricians. Clinical diagnoses were then compared with autopsy diagnoses using the Class Error System. Major diagnostic errors (Class I, Class II) were examined to determine if the autopsy was more useful in any particular patient group. There were 69 children: 36 (52%) were female, and 30 (43%) were infants. Autopsies were performed on 52 (75%) patients. Autopsy diagnoses were categorized as follows: sudden infant death syndrome (SIDS) 14 (27%); underlying disease 15 (29%); trauma 13 (25%); sepsis 8 (16%); and aspiration 2 (4%). No errors were made in 67% of cases. The autopsy confirmed the major clinical diagnosis in 85% of patients. There were no Class I errors. Class II error rate was 15%. Most Class II errors occurred in patients between one and five years of ate (57%), and in patients who had sepsis or underlying disease (95%). Our data show that autopsy is useful in determining the cause of death and may be useful for education and quality assurance in pediatric emergency medicine.

Autopsy↗
PubMed1994

Pediatric penetrating thoracic trauma: a five-year experience.

Penetrating thoracic trauma is managed nonoperatively in 85% of adult patients. We hypothesized that similar trauma in children would lead to proportionately more vital tissue damage and a higher rate of operative intervention. The pediatric penetrating thoracic trauma experience of a level one trauma center was analyzed over a five-year period. Data reviewed included circumstances of injury, Pediatric Trauma Score (PTS), interventions performed, and outcome. Of 61 children with thoracic trauma, 13 had penetrating injuries. Of these 13, seven were unintentional (five from firearms); the rest were caused by assaults. Seven patients (54%) underwent thoracotomy or laparotomy. All five patients with a PTS < 8 underwent surgical intervention, whereas only two of the eight patients with a PTS > or = 8 needed surgery (P < 0.05). There was one death. We reached the following conclusions: 1) Children with penetrating thoracic trauma are more likely to require surgical intervention than adults. 2) Penetrating thoracic trauma in children should elicit a thorough search for operative lesions. 3) About half these injuries are unintentional, and thus potentially preventable.

Adolescent↗
PubMed1994

Education attainment level of caregivers versus readability level of written instructions in a pediatric emergency department.

Our objectives were 1) to determine the education attainment level (EAL) of parents attending the pediatric emergency department (PED); 2) to assess the readability level (RL) of the written instructions available to these parents; and 3) to revise these instruction forms at a level of comprehension based on the EAL of parents. We used a questionnaire of EAL and RL assessment using the SMOG and FOG readability formulas. We then revised the written instructions and used parents in the PED to pretest them. The setting was a PED in a tertiary care hospital (Children's Hospital of Western Ontario). The participants were 1034 parents of children in the PED between 8 AM and 11 PM over a six-month period. Parents were chosen at 30-minute intervals on randomly selected weekdays and weekends. A total of 1022 completed the study. Seven forms commonly used in the PED were assessed for RL. Seven forms were rewritten at grade 6 to 7 RL, and each was pretested in 21 of 24 parents or guardians in the PED using a standardized questionnaire with open-ended questions. Ninety percent of respondents spoke English, and 85% had English as their first language. Forty-nine percent of parents had a grade 13 or lower EAL. This included the following EALs; < grade 12 EAL, 23%; < grade 10 EAL, 15%; and < grade 8 EAL, 4%. Of the seven forms tested, five were written at a college RL. Pretesting of revised forms elicited the following responses from parents: easy to understand (100%), understood everything (96-100%), worth remembering (77-96%), liked the form (67-100%), found it informative (52-85%), and thought it was applicable to all people (82-100%).(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1993

Comparison of fluid infusion rates among peripheral intravenous and humerus, femur, malleolus, and tibial intraosseous sites in normovolemic and hypovolemic piglets.

STUDY OBJECTIVES: To compare infusion rates from various intraosseous sites (tibial, medial malleolar, distal femoral, and humeral) and at a peripheral IV site under gravity and pressure flow in normovolemic and hypovolemic states. DESIGN AND SETTING: A piglet model was used to assess rates of infusion under varying conditions in a university hospital animal laboratory. Analysis of variance was used to evaluate site differences. PARTICIPANTS: Twenty-three Yorkshire-Landrace mix pigs (weight, 12 to 23 kg) were studied. INTERVENTIONS: Animals were anesthetized and intubated before cannulation with 18-gauge bone marrow needles at intraosseous sites and 22-gauge Teflon catheters in peripheral vessels. Infusion rates under gravity and 300 mm Hg pressure were determined. Infusion rates under similar conditions were repeated in hypovolemic animals with acute bleeding of 25 mL/kg. MEASUREMENTS AND MAIN RESULTS: Mean infusion rates (mL/min) for gravity versus 300 mm Hg pressure in normovolemic pigs were 13.1 versus 40.9 for peripheral IV, 11.1 versus 41.3 for humerus, 9.3 versus 29.5 for femur, 8.2 versus 24.1 for malleolus, and 4.3 versus 17.0 for tibia. Hypovolemia resulted in average decreased rates of 32%. Infusion rates were significantly different between sites and between normovolemia and hypovolemia (P = .0001). CONCLUSION: Intravenous access is the most efficacious method of acute volume replacement. Intraosseous sites differ in the infusion rates obtained--descending order is humerus, femur, malleolus, and tibia, but each is a reasonable alternative for short-term vascular access.

Animals↗
PubMed1993

Comparison of the acid-base status of blood obtained from intraosseous and central venous sites during steady- and low-flow states.

OBJECTIVE: To compare the acid-base status of blood obtained from the tibial intraosseous site with that status obtained from a central venous site during stead- and low-flow states in a piglet model. DESIGN: A prospective, observational study. SETTING: Animal laboratory at a university medical center. SUBJECTS: Nine 2-day-old piglets. INTERVENTIONS: Animals were anesthetized, intubated, and mechanically ventilated. A thermodilution pulmonary artery catheter was inserted via the right internal jugular vein and directed into the pulmonary artery. An arterial catheter was inserted into the right carotid artery and an intraosseous needle was inserted into the proximal tibial marrow cavity. Cardiorespiratory arrest was induced by discontinuation of ventilation. The animals were subsequently resuscitated by precordial compressions and ventilation. Blood samples were obtained from central venous and intraosseous sites during steady state and during resuscitation (low-flow state). RESULTS: No significant differences (p < .05) were found for pH, PCO2, and bicarbonate concentration when values that were obtained from the central venous and intraosseous sites were compared during steady- and low-flow states. CONCLUSIONS: The acid-base status of intraosseous blood is similar to that status of central venous blood. Intraosseous blood gas values may be an acceptable alternative to central venous blood gas values in judging central acid-base status during cardiopulmonary resuscitation.

Acid-Base Equilibrium↗
PubMed1993

An evaluation of the physical and functional characteristics of infant resuscitators.

Self-inflating resuscitators (SIRs) are commonly used to assist ventilation in the newborn. Despite their widespread use, there is limited information available on the functional and physical characteristics of SIRs. We studied five new infant bag-valve units to compare their physical characteristics, including reservoir, accumulator, and dead space volumes (VD), pressure relief mechanism (PRM), inspiratory resistance (RI), and functional mechanics including stroke volume (SV), fraction of delivered oxygen (FDO2), and cycle frequency at -5 degrees C, 20 degrees C, and 49 degrees C, using a test lung apparatus and experienced respiratory therapists. In addition, deficiencies and features that may render them less than ideal were sought. All SIRs met minimum standards for reservoir and accumulator volumes, RI (< 20 cmH2O/L/sec), SV (20-70 ml), and FDO2 (> 90%) as determined by the Canadian Standards Association (CSA) and the American Society for Testing of Materials (ASTM). However, the following deficiencies were noted: 1) MPR and Pulmanex had no PRM (ASTM requirement); 2) MPR could not cycle at -5 degrees C; 3) the VDs for Pulmanex (10 ml) and MPR (15 ml) were high; 4) the CPR connector broke during normal use, and the MPR connector frequently disconnected; 5) the Laerdal expiratory valve was incompetent; and 6) the Laerdal and CPR could be misassembled for use. Our study shows that some commercially available SIRs do not meet all CSA and ASTM standards and may not be ideal in specific clinical situations. The choice of a SIR may be dictated by the clinical situation in which its use is intended.

Equipment Design↗
PubMed1993

Appropriateness of hospitalization in a Canadian pediatric hospital.

Allocation of limited resources in the Canadian health care system is hampered by a lack of studies addressing the appropriateness of the pediatric patient days in hospital. The authors retrospectively reviewed one hospital day per month in 1988, using a Pediatric Appropriateness Evaluation Protocol previously used in the United States. Of 878 inpatients, 852 charts were reviewed, and 26 charts were unavailable for study. The patients ranged in age from premature newborns to 20 years old. There were 475 medical days, 359 surgical days, and 18 patients to other services. Statistical significance was tested using the chi 2 test for contingency tables. Twenty-four percent of patient days were inappropriate. Younger children and shorter lengths of stay were more likely to result in appropriate hospital days. For infants younger than 60 days, 11% of days in hospital were inappropriate, 21% of days for infants between 2 months and 1 year of age, 25% for children between 1 and 5 years, and 36% for children older than 5 years of age. Children hospitalized 2 days or less had inappropriate hospital days accounting for 16% of the reviewed days. This increased to 33% for 3 to 14 days of hospitalization. Inappropriate hospital days did not vary significantly from month to month. Surgical patients had more appropriate hospital days than medical patients. Admission route (elective, emergency, or transferred from another hospital) did not affect the appropriateness of the subsequent day reviewed. It is concluded that inappropriate hospitalization in a Canadian pediatric hospital occurs only slightly more frequently than in an American pediatric hospital.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1992

Relationship of cross-brain oxygen content difference, cerebral blood flow, and metabolic rate to neurologic outcome after near-drowning.

We evaluated the relationship of global cerebral blood flow, cross-brain oxygen content difference, cerebral metabolic rate for oxygen, intracranial pressure, and cerebral perfusion pressure to functional neurologic outcome in 12 comatose children on 2 consecutive days after near-drowning. Five children survived with functional neurologic outcome; five died and two survived with severe neurologic damage. Children who survived with functional neurologic outcome had a significantly higher cross-brain oxygen content difference (7.89 +/- 2.62 vs 3.91 +/- 1.59 ml/dl; p = 0.028) at 24 hours and a higher cerebral metabolic rate for oxygen 48 hours after admission (3.19 +/- 2.86 vs 0.96 +/- 0.45 ml/100 gm per minute; p = 0.030) compared with those who died or survived in a damaged state. There were no significant differences in global cerebral blood flow, intracranial pressure, and cerebral perfusion pressure between groups at either 24 or 48 hours. Our preliminary data suggest that a higher cross-brain content difference value is an important early variable associated with functional neurologic recovery after near-drowning. However, a single cross-brain oxygen content difference value must be interpreted with caution because considerable variability may occur among patient groups.

Adolescent↗
PubMed1992

Use of comparison radiographs in the diagnosis of traumatic injuries of the elbow.

STUDY OBJECTIVE: To determine whether comparison radiographic views of the uninjured elbow result in increased diagnostic accuracy in elbow trauma. DESIGN: Physicians were provided with a short clinical summary and asked to interpret radiographs of the injured elbow or of both the injured and the uninjured elbow in a randomized fashion. SETTING: The radiology department in a university hospital. METHODS: Fifty sets of radiographs from 25 children with elbow injuries were reviewed by two residents, two emergency physicians, and one pediatric radiologist using a standard classification of injuries. For each child, there were two sets of radiographs: one of the injured elbow and one of both the injured and the uninjured elbow. Descriptive statistics were used to report the results. kappa statistics were used to determine interobserver and intraobserver agreement. Missed diagnoses were divided into those that were clinically relevant and those that were not. RESULTS: The overall percentage of correct diagnoses (one versus two elbow radiographs) were as follows: residents, 69% versus 70%; emergency physicians, 62% versus 67%; and pediatric radiologist, 74% versus 72% (P greater than .05). kappa scores for interobserver variability and intrarater agreement were in the moderate range (.383 to .805; kappa, .08). Clinically relevant diagnoses were missed by trainees and emergency physicians regardless of whether radiographs of just the injured elbow or both the injured and the uninjured elbow were interpreted. Incorrect radiograph interpretations were due to false-positives in 17 of 23 cases. CONCLUSION: Comparison radiographs of the uninjured elbow did not improve diagnostic accuracy in elbow trauma in the pediatric emergency department.

Adolescent↗
PubMed1992

Comparison of continuous versus intermittent furosemide administration in postoperative pediatric cardiac patients.

OBJECTIVE: To compare the effects of furosemide administered by intermittent iv infusion vs. continuous iv infusion on urine output, hemodynamic variables, and serum electrolyte concentrations. DESIGN: Prospective, randomized trial. SETTING: Pediatric ICU. PATIENTS: Postoperative pediatric cardiac patients. INTERVENTIONS: Patients were assigned to either the continuous iv infusion or the intermittent infusion groups. The intermittent group received 1 mg/kg iv of furosemide every 4 hrs to be increased by 0.25 mg/kg iv every 4 hrs to a maximum of 1.5 mg/kg iv if the urine output was less than 1 mL/kg.hr. The continuous infusion group received an initial furosemide dose of 0.1 mg/kg iv (minimum 1 mg) followed by an iv infusion rate of 0.1 mg/kg.hr of furosemide to be doubled every 2 hrs to a maximum of 0.4 mg/kg.hr if the urine output was less than 1 mL/kg.hr. MEASUREMENTS AND MAIN RESULTS: Demographic variables, fluids, electrolyte and inotropic requirements were the same in both groups. A significantly (p = .045) lower daily dose of furosemide (4.90 +/- 1.78 vs. 6.23 +/- 0.62 mg/kg.day) in the continuous iv infusion group produced the same 24-hr urine volume as that of the intermittent group. There was more variability in urine output in the intermittent group as well as more urinary losses of sodium (0.29 +/- 0.15 vs. 0.20 +/- 0.06 mmol/kg.day, p = .0007) and chloride (0.40 +/- 0.20 vs. 0.30 +/- 0.12 mmol/kg.day, p = .045). CONCLUSION: Furosemide administered by continuous iv infusion is advantageous in the post-operative pediatric patient because of a more controlled and predictable urine output with less drug requirement and less urinary loss in sodium and chloride.

Cardiac Surgical Procedures↗