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Biomedical subjects

R J Byrick

Publications and source records attributed to R J Byrick.

At least 55 records · Page 3Linked to original sources
PubMed1987

Cardiopulmonary function and pulmonary microemboli during arthroplasty using cemented or non-cemented components. The role of intramedullary pressure.

An experimental model was designed to investigate the role of intramedullary pressure on cardiopulmonary function and pulmonary pathology during arthroplasty using cemented and non-cemented components. Twenty-four dogs were divided randomly into three groups: a group that received a non-cemented implant in which low intramedullary pressure was generated, a group that received a cemented implant, and one that received bone wax and an implant; high intramedullary pressures were generated in the latter two groups. Bone wax was used to generate high intramedullary pressures without the use of bone cement. In the group with the non-cemented implant, few pulmonary microemboli and no significant cardiorespiratory changes were found. In the groups that received bone wax and an implant or the cemented implant, there were many pulmonary microemboli and significant cardiorespiratory changes, including decreased arterial oxygen tension, increased pulmonary arterial pressure, and increased intrapulmonary shunt fraction. There was no evidence that methylmethacrylate monomer was responsible for the cardiorespiratory changes in the group with the cemented implant.

Animals↗
PubMed1986

Impact of an intermediate care area on ICU utilization after cardiac surgery.

We compared utilization of a 14-bed respiratory ICU before and after establishing an intermediate care area (ICA) for patients recovering from cardiac surgery. Availability of the four-bed ICA significantly reduced the duration of ICU stay in patients who had undergone aortocoronary bypass or valvular cardiac surgery, and no potentially preventable deaths resulted from early ICU discharge. Use of an ICA should also decrease ICU utilization for other low-risk monitored patients.

Cardiac Surgical Procedures↗
PubMed1986

Influence of mannitol and dopamine on renal function during elective infrarenal aortic clamping in man.

The impact of elective infrarenal aortic clamping on parameters of renal function was evaluated in 27 extracellular fluid volume expanded patients. Significant transient decreases (p less than 0.05) in glomerular filtration rate were observed in all three groups either in the early or late post-clamp release period, despite maintenance of hemodynamic stability. This study documents transient decreases in glomerular filtration rate which occurred following release of the infrarenal aortic cross-clamp. No clinically important benefit from the use of mannitol and dopamine over extracellular fluid volume expansion with saline alone was demonstrated in the prevention of the changes in renal function associated with aortic cross-clamping.

Adult↗
PubMed1985

Relaxation of tracheomotor tone by PEEP: influence of hypocapnia and acidemia.

The effect of PEEP on airway smooth muscle tone is difficult to assess using standard lung resistance and compliance techniques. In this study we isolated the extrathoracic trachea from lower airway pressure by performing a low cervical tracheostomy in dogs. We then measured the pressure (PTE) within a water-filled cuff of an endotracheal tube which was placed in the isolated extra-thoracic tracheal segment above the tracheostomy as a measure of tracheomotor tone. Sudden application of 10 cm H2O PEEP in normocapneic animals (PaCO2 = 5.6 +/- 0.2 kPa) caused an immediate dilation in this extrathoracic tracheal segment (PTE decreased from 5.7 +/- 0.3 kPa to 2.4 +/- 0.4 kPa). This decrease in tracheomotor tone was transient, returning to control level by four minutes in spite of 10 cm H2O PEEP maintained on the lower airway. With zero end-expiratory pressure the respiratory rate was increased from 9 to 19 breaths per minute and PaCO2 reduced to 3.9 +/- 0.2 kPa. No detectable tracheomotor dilation was observed after the application of 10 cm H2O PEEP to the lower airway. When exogenous CO2 was added to the inspired gas mixture at a respiratory rate of 19/min, the PaCO2 increased from 4.2 +/- 0.2 kPa to 6.7 +/- 0.4 kPa and a tracheomotor dilation in response to PEEP was again detectable. Finally, a 0.1 N infusion of HCl was infused into hypocapneic animals (PaCO2 = 3.7 +/- 0.3 kPa; pH = 7.47 +/- 0.02). After 30-70 minutes, pH decreased to 7.26 +/- 0.02 and PaCO2 remained 3.5 +/- 0.3 kPa.(ABSTRACT TRUNCATED AT 250 WORDS)

Acidosis↗
PubMed1985

Tracheomotor response to cardiopulmonary bypass: influence of lung deflation and cardiac distension.

The pressure within the water-filled cuff of an endotracheal tube (PTE) was used as a measure of tracheal smooth muscle tone in ten patients undergoing cardiopulmonary bypass (CPB). Pulmonary artery pressure (PPA) and left atrial pressure (PLA) were also monitored. Institution of CPB, with acute reduction of pulmonary blood flow and lung deflation, caused no significant change in PTE. Crystalloid cardioplegic administration without left ventricular decompression (VENT) resulted in statistically significant increases of PPA (from 1.33 +/- 0.15 to 1.88 +/- 0.2 kPa) (p less than 0.05) and of PLA (from 1.2 +/- 0.11 to 2.2 +/- 0.31 kPa) (p less than 0.05). Coincident with these changes a statistically significant increase in PTE (from 4.95 +/- 0.21 to 5.24 +/- 0.27 kPa) (p less than 0.05) was detected. This increase in PTE was significantly greater than the small random variations noted in PTE prior to cardioplegic infusion with constant PLA and PPA. Thus, minimal tracheomotor constriction in response to cardioplegia administration occurred. Larger increases in PTE were noted during cardiac compression suggesting that the water-filled cuff could have detected larger increases if they had occurred. These transient changes do not reflect clinically detectable increases in airway resistance at the termination of CPB when lung ventilation is started. Neither of these two physiological stimuli, lung deflation or cardioplegia administration, cause clinically significant increases of large airway tone during CPB.

Airway Resistance↗
PubMed1985

Outcome of respiratory intensive care for the elderly.

We followed 1018 patients admitted consecutively to a multidisciplinary respiratory ICU (RICU), with special attention to patients aged 75 yr and over. The elderly had a higher RICU (11/49) and in-hospital (21/49) mortality than younger patients. The 28 survivors of hospitalization had a lower acute physiology score (APS) than nonsurvivors on admission (16.1 +/- 7.8 vs. 21.8 +/- 8.9, respectively), indicating less severe illness. The quality of long-term survival (12 to 24 months) was assessed using an open-ended questionnaire. Eighteen hospital survivors were alive at the time of follow-up and the quality of life was deemed satisfactory by 10 of 13 patients who were living independently. Only two of 28 survivors had been transferred to nursing home care, and two were in acute care hospitals. We conclude most elderly patients discharged from the RICU consider their lifestyle satisfactory and are not a large drain on community health care resources. Further studies of the screening process which determines RICU admission are necessary, because unimodal criteria such as age and APS after admission were not of prognostic value.

Age Factors↗
PubMed1984

Large airway response to cemented arthroplasty: relationship to hypoxaemia. An experimental study in dogs.

Alteration in airway smooth muscle tone has been implicated in the mechanism of hypoxemia, pulmonary hypertension and changes in dynamic thoracic compliance after total hip arthroplasty (THA). We used the pressure within a water-filled cuff of an endotracheal tube as a continuous measure of changes in tracheomotor tone during THA in mongrel dogs, while intermittently assessing gas exchange abnormalities. In all 16 dogs the instillation of polymethylmethacrylate (PMMA) into the femoral medullary shaft resulted in tracheal dilation. In ten dogs we demonstrated simultaneous hypotension, hypoxemia and increase in shunt fraction (Qs/Qt) after THA. In six dogs the medullary canal was thoroughly lavaged prior to PMMA injection, and no hypoxemia, hypotension or increased Qs/Qt was found in spite of persisting tracheomotor relaxation. We conclude that these well-documented gas-exchange abnormalities are not mediated by changes in large airway tone. Since the hypoxemia was abolished by medullary lavage in our animal model, we suggest that this syndrome is mediated by alterations in lung perfusion and associated small airway constriction and not by changes in large airway smooth muscle tone.

Airway Resistance↗
PubMed1983

Nitroglycerin relaxes large airways.

This study documents the effect of intravenous nitroglycerin (NTG) on tracheal smooth muscle in 12 patients undergoing coronary artery surgery. The pressure within a water-filled tracheal cuff was monitored continuously, as well as systemic and pulmonary arterial pressures. A significant decrease in cuff pressure after intravenous NTG (4.0 +/- 0.3 micrograms/kg) was detected before cardiopulmonary bypass (CPB). During CPB, with exclusion of the pulmonary arterial circulation, the tracheal cuff response to NTG administered into the oxygenator persisted and was not significantly different from that noted before CPB. Thus, the large airway (tracheal) response to NTG was independent of the pulmonary circulation and probably is mediated by the bronchial circulation. The response during CPB indicated that the tracheal smooth muscle retains tone and can respond to NTG even when the lungs are collapsed with no pulmonary arterial perfusion. These data were obtained from patients with no clinical evidence of reversible airway obstruction and indicate only that NTG relaxed human tracheal smooth muscle in vivo. These data do not demonstrate the efficacy of intravenous NTG in patients with asthma.

Adult↗
PubMed1983

The role of lavage in preventing hemodynamic and blood-gas changes during cemented arthroplasty.

UNLABELLED: An experimental model was designed to investigate the role of meticulous intramedullary lavage in the prevention of the blood-gas and hemodynamic changes that have been documented to occur during cemented arthroplasty. Twenty-one adult mongrel dogs were divided into two groups. One group had the medullary canal thoroughly lavaged prior to insertion of the cement and prosthesis and the other group had no lavage. The results clearly showed that careful lavage can eliminate the significant decreases in arterial PO2 and increases in intrapulmonary shunt fraction and pulmonary artery pressure that were evident in the group that did not have lavage. Femoral medullary reaming was investigated and was shown not to compromise the dogs' cardiopulmonary status. CLINICAL RELEVANCE: During cemented arthroplasty, thorough lavage of a plugged medullary canal prior to insertion of the cement and prosthesis is a highly effective prophylactic measure in the elimination of gas-exchange and hemodynamic complications.

Animals↗
PubMed1982

Management of a malignant hyperthermia patient during cardiopulmonary bypass.

The anaesthetic management of cardiopulmonary bypass (CPB) for a patient with biopsy-proven malignant hyperthermia is reported. Specific changes in the technique used, such as venting the oxygenator before use, monitoring mixed venous PO2 and PCO2, as well as the safety of cold hyperkalaemic cardioplegia are described. Controversial aspects of malignant hyperthermia management such as the safety of calcium and catechol inotropes are discussed in relationship to the successful use of cardio-pulmonary bypass in our patient. We chose to treat left ventricular dysfunction by aggressive vasodilator (nitroglycerine) therapy. We detected no myocardial or respiratory depression secondary to dantrolene therapy either before or after operation.

Anesthesia↗
PubMed1982

Extrathoracic cuff pressure reflects changes of intrathoracic large airway circumference.

The pressure measured in water-filled cuffs of endotracheal tubes has been used to evaluate the effect of drugs and physiologic stimuli on large airway tone. In six mongrel dogs, extrathoracic cuff pressure was monitored while simultaneously monitoring intrathoracic tracheal circumference measured by an implanted mercury strain gauge. The airways of each animal were alternately dilated with intravenous aminophylline (10 mg/kg) and constricted with edrophonium (10 mg). In each animal a significant linear relationship was found between cuff pressure and intrathoracic tracheal circumference. The slopes of these linear relationships were consistent for each animal, but varied between animals. In a second group of 11 dogs, cuff pressure was measured at extrathoracic and intrathoracic tracheal sites, as well as in the left main stem bronchus. Similar directional changes in cuff pressure were found at each site. This suggests that a water-filled system monitoring cuff pressure in the extrathoracic trachea reflects the direction of circumference change in the intrathoracic trachea and major bronchi.

Airway Resistance↗