The human bone marrow response to acute air pollution caused by forest fires.

Atmospheric pollution increases cardiopulmonary morbidity and mortality by unexplained mechanisms. Phagocytosis of fine particles (PM(10)) by rabbit alveolar macrophages elevates white blood cells (WBC) by releasing precursors from the bone marrow and this could contribute to the pathogenesis of cardiopulmonary disease. The present study examined the association between acute air pollution caused by biomass burning and peripheral WBC counts in humans. Serial measurements of the WBC count made during the 1997 Southeast Asian Smoke-haze (Sep 29, Oct 27) were compared with a period after the haze cleared (Nov 21, Dec 5) using peripheral blood PMN band cells to monitor marrow release. The results showed that indices of atmospheric pollution were significantly associated with elevated band neutrophil counts expressed as a percentage of total polymorphonuclear leukocytes (PMN), with maximal association on zero and 1 lag day for PM(10) and 3, and 4 lag days for SO(2) (p value < 0.000). We conclude that atmospheric pollution caused by biomass burning is associated with elevated circulating band cell counts in humans because of the increased release of PMN precursors from the marrow. We speculate that this response contributes to the pathogenesis of the cardiorespiratory morbidity associated with acute air pollution.

Treatment of delayed partial bronchial rupture with expandable metallic stent.

Traumatic bronchial rupture is a rare entity. The severity of the trauma often causes lethal injury to other thoracic organs. The incidence in patients with blunt chest trauma admitted to the hospital ranges from 1.5% to 3%. As a rule, early diagnosis and surgical treatment are important to facilitate successful repair of the disruption. We describe an unusual case of bronchial rupture which was diagnosed 15 days after blunt chest trauma and was treated by bronchial stenting. The success of this case involving the left main bronchial rupture provides a feasible alternative to the repair of partial airway disruption and greatly reduces the morbidity.

Cerebral response to haemodilution during cardiopulmonary bypass in dogs: the role of nitric oxide synthase.

During cardiopulmonary bypass, haemodilution is standard practice and is accompanied by increases in cerebral blood flow (CBF). We investigated if changes in cerebral vascular resistance (CVR) during cardiopulmonary bypass-haemodilution are dependent on nitric oxide synthase. The cerebral response to haemodilution in nine dogs treated with the nitric oxide synthase inhibitor, N omega-nitro-L-arginine methyl ester (L-NAME), was compared with a control group (n = 8). Both groups underwent serial isovolaemic haemodilution (target packed cell volumes 0.39, 0.26, 0.19 and 0.14) using 6% dextran 70. CBF, CVR and cerebral metabolic rate for oxygen (CMRO2) were measured. While initial CVR was different in the two groups, haemodilution-dependent reductions in CVR were equivalent and the curves describing the packed cell volume-CVR relationship were parallel in control and nitric oxide synthase inhibition groups. Our data indicate that nitric oxide synthase does not play a primary role in the cerebral response to haemodilution.

Predicting the size of a double-lumen endobronchial tube using computed tomographic scan measurements of the left main bronchus diameter.

UNLABELLED: We investigated the use of chest computer tomographic (CT) scan measurement of the left mainstem bronchial diameter to predict the correct left-sided double-lumen endobronchial tube (DLT) size in Asian patients who may require smaller DLT sizes. Fifty consecutive Asian adults aged 17-80 yr with preoperative chest CT scans undergoing elective thoracic surgery were entered into the study. The measurements of the left main bronchus diameter were made by using the electronic calipers of the spiral scanner to the nearest millimeter. The sizes of DLT selected were 32F, 35F, 37F, 39F, and 41F for left main bronchus diameters of <10 mm, 10 mm, 11 mm, 12 mm, and >12 mm, respectively. All DLT placements were confirmed and positioned by using fiberoptic bronchoscopy. The tracheas of all patients were successfully intubated with the predicted DLT sizes. Thirty-four patients (68%) were predicted to require smaller DLTs (37F or smaller). Six patients were correctly predicted to receive 32F DLTs. Twelve patients (24%) received an oversized DLT, but none received an undersized DLT. The overall positive predictive value for the male and female patients was 84.4% and 61.1%, respectively. Our study showed that CT scan measurements of the diameter of the left bronchus were especially useful in choosing smaller DLTs. IMPLICATIONS: We used computer tomographic scans to measure the diameter of the left mainstem bronchus, then selected the size of the left-sided double-lumen endobronchial tube (DLT) accordingly. We found that we could predict the sizes of the DLT fairly accurately, especially the smaller DLTs.

Dose response study of lidocaine 1% for spinal anaesthesia for lower limb and perineal surgery.

PURPOSE: To compare the sensory and motor block produced by three different volumes of intrathecal lidocaine 1% and thereby determine the appropriate volume to administer for surgery of the lower limbs and perineum. METHODS: Forty-eight patients scheduled for perineal or lower limb surgery were randomly assigned to receive 4, 6 or 8 ml lidocaine 1% intrathecally. The onset, spread, duration and regression of analgesia and motor block and side effects were evaluated (by a blinded observer whenever possible). RESULTS: The maximum cephalad spread in the 6 ml (T8 +/- 3) and 8 ml (T4 +/- 1.7) groups were higher than the 4 ml group (T12 +/- 2.2, P < 0.01). In the 4 ml group, six patients (33%) did not achieve analgesia to T12 and four (22%) did not have complete motor blockade. Patients given 8 ml had longer duration of block (duration at T12: 104 +/- 23 vs 60 +/- 24, 67 +/- 14 min. P < 0.01: 8 ml vs 4, 6 ml) and slower recovery times (sensory recovery: 188 +/- 27 vs 142 +/- 27, 157 +/- 28 min. P < 0.01; 8 ml vs 4, 6 ml). Two patients (18%) from the 8 ml group and one (5%) from the 6 ml group had transient hypotension. CONCLUSION: Four millilitres intrathecal lidocaine 1% is adequate for perineal surgery but for lower limb procedures, 6 ml is more appropriate as it consistently provides sensory analgesia above L1 dermatome and complete motor block. Eight ml gives an unnecessarily high block with higher incidence of hypotension.

Predicting the size of a double-lumen endobronchial tube based on tracheal diameter.

UNLABELLED: We assessed whether using the tracheal diameter to predict the correct size of the left double-lumen endobronchial tube (DLT) could be used for our generally smaller sized Asian patients. Sixty-six consecutive adult patients under anesthesia for elective surgery requiring the use of a DLT were studied. The size of the left-sided DLT used was based on the width of patients' trachea measured from the preoperative posterior-anterior chest radiograph. The placement of the DLT was standardized and confirmed with fiberoptic bronchoscopy. The correct size of the DLT was the largest size tube inserted into the left bronchus with a small air leak detectable when the endobronchial cuff was deflated but not exceeding the recommended resting volume when inflated for lung isolation. Using this method of choosing our DLT, we found that an oversized DLT was often chosen especially among our female Asian patients. The overall positive predictive values for the male and female patients were 77.3% and 45.5%, respectively. We postulate that this could be due to our criteria for correct DLT size or that our local Asian patients, especially the females, were smaller and shorter. IMPLICATIONS: This study assessed whether the correct double-lumen endobronchial tube size could be predicted from tracheal diameter measurements taken from the chest radiograph. We found that this method of choosing the double-lumen endobronchial tubes was not always reliable.

Hemodilution and whole body oxygen balance during normothermic cardiopulmonary bypass in dogs.

OBJECTIVE: The purpose of this study was to determine the minimum hematocrit value that can support whole body oxygen consumption during normothermic cardiopulmonary bypass. The effect of hemodilution on peripheral resistance, whole body oxygen delivery, and oxygen consumption was determined over a range of hematocrit values. METHODS: Measurements were obtained during 38 degrees C cardiopulmonary bypass with progressive normovolemic hemodilution (hematocrit value 40% to 9%) in nine dogs. Dextran 70 (6%) was used as a diluent. Anesthesia consisted of high-dose fentanyl and midazolam. A mean arterial pressure of 60 mm Hg was maintained throughout cardiopulmonary bypass via increases in pump flow. RESULTS: Progressive hemodilution was associated with a decreasing total peripheral resistance. During normothermic cardiopulmonary bypass with a whole blood prime, the whole body oxygen consumption approximated values previously reported in dogs under nonbypass conditions. Oxygen delivery and whole body oxygen uptake were maintained between a hematocrit value of 39% and 25%. Significant decreases for both were seen when the hematocrit value was reduced to 18% and below. CONCLUSIONS: A hematocrit level greater than 18% was needed to maintain systemic oxygen delivery and consumption during warm cardiopulmonary bypass. The critical hematocrit value may be higher under bypass than nonbypass conditions because the flow increases that are practical during cardiopulmonary bypass do not approximate those seen in response to hemodilution of the intact circulation. Finally, the critical hematocrit value for the body may be higher than that required for the brain during warm cardiopulmonary bypass.

Twenty-five years of national service--changes in height, weight and body mass index.

The height and weight of 18-year-old Singapore National Service enlistees were extracted from computer records spanning 25 years (1967-1991). These were analysed for mean height, weight and body mass index (BMI) which overall show increases of 4.12 cm, 10.13 kg and 2.60 kg/m2 respectively. All ethnic groups (Chinese, Malay, Indian and Others) show a similar rising trend. While mean height appears to have stabilised in recent years, mean weight continues to rise. This is reflected in an increasing mean BMI. The proportion of 18-year-old male recruits with a BMI in the overweight range (> or = 25 kg/m2) increased from 1.37% in 1967 to 12.07% in 1991.