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Biomedical subjects

S C Guha

Publications and source records attributed to S C Guha.

11 recordsLinked to original sources
PubMed1997

Scalene muscles and the brachial plexus: anatomical variations and their clinical significance.

Anatomical variations may be clinically significant, but many are inadequately described or quantified. Variations in neck anatomy are important to surgeons performing surgical procedures in this region. Thirty-two female and 19 male adult cadavers were studied. The commonly described anatomical relationship of the brachial plexus (BP) lying between the anterior scalene (AS) and middle scalene (MS) muscles was found in only 60% of instances. Scalenus minimus was present in 46% of instances (bilateral in 14 cadavers). The most common variation was the penetration of the AS by the C5 and/or C6 ventral rami. The C5 and C6 roots may fuse before piercing AS (15% cases, bilateral in 4 cadavers), or the C5 root alone pierce the belly of AS (13% cases, bilateral in 3 cadavers). The roots also may pierce AS independently (6% cases, bilateral in 1 cadaver). In 3%, the C5 root was found to be completely anterior to AS.

Brachial Plexus↗
PubMed1996

Burn resuscitation: crystalloid versus colloid versus hypertonic saline hyperoncotic colloid in sheep.

OBJECTIVES: The present study was undertaken to assess the fluid balance and hemodynamic effects during the first 8 hrs of resuscitation in animals with a large body surface area burn, using lactated Ringer's solution, 6% hetastarch, and hypertonic saline dextran. DESIGN: A prospective, blinded, controlled, terminal study, using anesthetized animals. The initial baseline period was followed by scald injury, and three different treatment regimens were administered from coded bags to achieve a physiologic end point. SETTING: University laboratory. SUBJECTS: Eighteen female sheep (35 to 45 kg) were anesthetized with isoflurane. INTERVENTIONS: Test solutions (10 mL/kg of either lactated Ringer's solution, hetastarch, or hypertonic saline dextran) were infused 30 mins after the scald injury at a rate to restore and maintain the baseline oxygen delivery (DO2) value. MEASUREMENTS AND MAIN RESULTS: Cardiovascular hemodynamics, plasma sodium concentration, plasma colloid osmotic pressure, and fluid balance were measured before and after scalding and resuscitation. After the initial 10-mL/kg test solution dose was given, lactated Ringer's solution was infused to achieve the same end point of baseline DO2 for the remainder of the 8 hrs. The scald caused an initial 30% reduction in cardiac output, a 20% reduction in mean arterial pressure, and 10% to 15% increase in hematocrit. All three test solutions restored and maintained baseline DO2 within 1 hr. However, hetastarch and hypertonic saline dextran reduced the net fluid volume over 8 hrs by 48% and 74%, respectively, compared with lactated Ringer's solution. Edema in the burn wound was not affected by treatment, while hypertonic saline dextran reduced edema in nonburned skin compared with both lactated Ringer's solution and hypertonic saline dextran. Plasma colloid osmotic pressure was significantly higher in the hetastarch and hypertonic saline dextran groups. A continuous decrease in plasma sodium concentrations from baseline values (140 to 145 mmol/L) was measured in the lactated Ringer's solution and hetastarch groups (130 to 133 mmol/L) over 8 hrs. Plasma sodium concentrations in the group receiving hypertonic saline dextran were increased (150 to 155 mmol/L) at 4 hrs, but returned toward baseline by 8 hrs. CONCLUSIONS: Net volume loading can be reduced markedly by initial resuscitation of large body surface area burn injury using a colloid (hetastarch), and can be further reduced by use of hypertonic saline colloid. Hyponatremia was apparent in the isotonic crystalloid- and colloid-treated animals, but not in those animals treated with hypertonic saline colloid.

Animals↗
PubMed1996

Cricothyrotomy: the anatomical basis.

Cricothyrotomy is an important surgical technique. We studied the anatomy of the cricothyroid membrane in 13 adult fresh cadavers preserved at 45 degrees F and examined at 70 degrees F. The working dimensions of the cricothyroid membrane were measured for emergency cricothyrotomy and placement of an airway tube. The vertical measurement ranged from 8-19 mm (mean 13.69 +/- SE 0.96 mm) and the maximal width between the cricothyroid muscles ranged between 9 and 19 mm (mean 12.38 +/- SE 0.91 mm). The distance from the upper limit of the cricothyroid membrane to the vocal cord was 9.78 +/- SE 0.52 mm. Eight subjects (62%) had an artery delineated transversely across the cricothyroid membrane. Two subjects (15%) had sclerosis of the cricothyroid joint. To promote the safe use of cricothyrotomy, the anatomy of the cricothyroid membrane is defined and clinically relevant data are presented.

Cadaver↗
PubMed1993

Attenuated fibroblast sheath around the basement membrane zone in the trachea.

In the connective tissue underlying the epithelium of the airways, there are thin attenuated cells that appear to be fibroblasts. These cells are close to the basal lamina and delineate an area equivalent to the basement membrane zone (BMZ). Using the mean data from transversely and longitudinally sectioned attenuated fibroblasts, we estimate that the diameter of the attenuated fibroblast is approximately 28.0 microns and its thickness 0.55 microns. Serial sections indicate there are pores of various sizes in the attenuated fibroblast. Also, the presence of cell segments less than 5 microns in length suggests there are processes from the edge of the cell which would give it a stellate appearance. These large flat cells form a sheath covering 66 to 70% of the BMZ at an average distance of 1.9 microns from the basal lamina. In addition, they make contact with the basal lamina approximately 7,000 times per mm2 of basal lamina. The majority of the contacts with the basal lamina are beneath basal cells. Cells of the attenuated fibroblast sheath are probably associated with lung morphogenesis, wound healing, and development of the BMZ. Their existence as a sheath demonstrates an anatomical unit associated with fibroblast-epithelial cell interactions in airway epithelium.

Animals↗
PubMed1992

Pulmonary hemodynamics and tissue damage after one lung infusion of Pseudomonas aeruginosa in sheep.

The relative roles of hematogenous mediators and direct bacterial toxicity due to phagocytosis by pulmonary intravascular macrophages were determined by selective bacterial infusion into the left pulmonary artery and comparison of right and left lungs at 24 h. Chronically instrumented sheep received 15-min pulmonary arterial infusions of live Pseudomonas aeruginosa (0.35-2.9 x 10(9), n = 6) or saline (n = 5). The saline group demonstrated stable cardiopulmonary function over time. Left lung blood flow, measured by Doppler flow probe, decreased 15 min into the bacterial infusion, with a concomitant sevenfold increase in left lung pulmonary vascular resistance index. The right lung pulmonary vascular resistance index doubled at 1 h, in association with increased plasma thromboxane B2 levels. An increase in cardiac index and decrease in systemic vascular resistance occurred at 12 h. The wet-to-dry weight ratio of the Pseudomonas-infused left lung was increased compared with that of the sham-infused lung. The tissue count of neutrophils in the lungs was doubled in both sides, but neutrophils on the left were more degranulated. The left lung tissue damage was caused by direct bacterial toxicity, including activation of phagocytic cells. Hematogenous mediators induced pulmonary and systemic hemodynamic changes and right lung neutrophil sequestration, but they did not damage the noninfused lung.

Animals↗
PubMedDate not supplied

Is the CD18 adhesion complex of polymorphonuclear leukocytes involved in smoke-induced lung damage? A morphometric study.

Neutrophils are the primary vectors that produce lung parenchymal injury after smoke inhalation as a result of their transmigration through endothelial and epithelial gap junctions toward the airway surfaces. LFA-1 (CD11a/CD18) on the neutrophil surface is essential for this transmigration in many tissues. We hypothesized that anti-CD18 antibodies would block such movement and prevent lung damage. Ten sheep received nebulized cotton smoke in our standardized model of inhalation injury. The sham group (n = 2) was insufflated with air only, the second group (n = 4) was insufflated with smoke but received no antibody, and the third group (n = 4) was given monoclonal antibody R15.7 before smoke injury. A similar degree of parenchymal injury and an alveolar epithelial reparative response were measured in both groups receiving injury. Neutrophil counts in the interstitium of both injured groups were also similar. However, in the R15.7 pretreated group, neutrophils remained inside the capillary in far larger numbers (p < 0.05). The CD11/18 adhesion complex may not be necessary for the pulmonary microvascular changes associated with inhalation injury.

Animals↗
PubMedDate not supplied

A comparison of two different 2400 mOsm solutions for resuscitation of major burns.

The reduction of burn edema is a common goal in the resuscitation of patients with thermal injury. Initial infusion of a 2400 mOsm hypertonic 7.5% NaCl 6% dextran (HSD) has been shown to reduce volume needs, but elevated serum sodium levels limit the dose that can be safely used. This study tested the hypothesis that a 2400 mOsm solution of NaCl, amino acids, glucose, and 6% dextran (Isosal-D) would reduce similar volume requirements while maintaining normal plasma sodium levels. Hemodynamics, plasma sodium, fluid balance, and tissue water content were measured after an initial baseline period and during resuscitation of a large scald injury in 21 anesthetized sheep. Resuscitation was begun 30 minutes after the scald with infusion of 10 ml/kg of either lactated Ringer's (LR), Isosal-D, or HSD and was continued with LR to restore and maintain baseline oxygen delivery throughout the 8-hour period. Oxygen delivery, cardiac output, and mean arterial pressure were rapidly reestablished by all three solutions, although a persistent tachycardia was noted with Isosal-D. Net fluid requirements of both HSD (35 +/- 13 ml/kg) and Isosal-D (72 +/- 13 ml/kg) were significantly lower than in the LR group (203 +/- 39 ml/kg). Mean serum sodium increased 11 mEq with HSD to a peak after 4 hours of 152 +/- 5 mEq, whereas with LR sodium fell 7 mEq to 132 +/- 4. Isosal-treated animals had minimal change in serum sodium. HSD significantly decreased tissue water content in colon, liver, pancreas, and nonburned skin compared with LR, whereas Isosal-D reduced edema only in the colon. It is concluded that in this protocol Isosal-D was not as effective as HSD at reducing volume needs and edema and had unexpected chronotropic effects.

Animals↗
PubMedDate not supplied

The role of interstitial starling forces in the pathogenesis of burn edema.

The formation and sustainability of burn edema require substantial change in net microvascular forces. We directly measured interstitial hydrostatic pressure (Pi) and total interstitial absorptive pressure (Pi + IIi), in dermis of anesthetized sheep, before and after a 70% to 85% total body surface area scald and during fluid resuscitation. The most rapid change occurred in Pi in the burn wound, which rapidly decreased from its baseline value of approximately -2 mm Hg to -11 mm Hg in the first 5 minutes, and thereafter increased but remained approximately -4 mm Hg through 4 hours of resuscitation. Pi in nonburned skin slowly increased from its preburn level -2 mm Hg, to become positive +1 mm Hg after 4 hours of resuscitation. The total interstitial absorptive pressure, Pi + IIi, slowly declined similarly from 15 to 16 mm Hg to approximately 10 to 11 mm Hg over 6 hours of resuscitation in both burned and nonburned dermis. Taken together, these data suggest that the rapid formation of burn edema is the result of development of a negative Pi in the burn wound, and its sustainability is the result of a large increase in interstitial compliance. Edema in nonburned skin did not start until after fluid resuscitation was initiated, and then developed as the plasma oncotic pressure declined from 21 to 10 mm Hg.

Animals↗