Plasma cortisol in open-heart surgery

In view of disagreements about changes in plasma cortisol, during and after open-heart surgery, a group of patients was studied with both unconjugated plasma cortisol, and anaesthetic, surgical and pharmacological factors that could interfere with the response, being analysed.     

Ceftriaxone disposition in open-heart surgery patients.

The effects of cardiopulmonary bypass (CPB) with hypothermia and systemic heparinization on ceftriaxone disposition were evaluated in seven male patients. A bolus dose of drug (14 mg/kg of body weight) was given, and blood and urine specimens were collected before, during, and after CPB for 96 h. Creatinine, albumin, and total and free ceftriaxone concentrations in plasma were measured. The ceftriaxone free fraction (ff) in vitro was estimated by equilibrium dialysis, and the in vivo ff was obtained by the ratio of renal clearance due to filtration to creatinine clearance. Pharmacokinetic parameters were based on concentrations of total drug and free drug. Albumin decreased from 3.10 +/- 0.29 g/dl presurgery to 1.42 +/- 0.17 g/dl and recovered to 2.46 +/- 0.26 g/dl on postoperative day 4. CPB markedly increased the in vitro ff, which was reversed by protamine post-CPB (ff pre-CPB, 0.15 +/- 0.01; during CPB, 0.53 +/- 0.20; post-CPB, 0.16 +/- 0.02). The in vitro ff exceeded the in vivo ff (0.53 +/- 0.20 versus 0.24 +/- 0.07), probably due to continued free fatty acid release caused by heparin during dialysis. Clearances based on free drug decreased, and the renal clearance due to filtration increased (7.6 +/- 2.8 versus 15.0 +/- 4.5 ml/min) while the creatinine clearance decreased (114 +/- 29 versus 72 +/- 28 ml/min) during CPB. Diminished binding owing to low albumin and free fatty acids explain this behavior. Lower binding also increased the volume of distribution (154 +/- 41 ml/kg) and extended the half-life (15 +/- 6 h). In summary, ceftriaxone disposition was significantly altered by CPB, resulting in marked increases in free drug concentrations, half-life, and volume of distribution and in decreased intrinsic clearance.     

Prolonged ventilatory support after open-heart surgery.

OBJECTIVES: To characterize the course of open-heart surgery patients who require prolonged (greater than 72 hrs) mechanical ventilation and to define the role and timing of tracheostomy. DESIGN: Retrospective review. SETTING: Cardiac surgery ICU and surgery wards at a university hospital. PATIENTS: All open-heart surgery patients during an 18-month period from January 1988 to July 1989 (n = 581). From this group, 58 patients (9.9%) required prolonged mechanical ventilation. INTERVENTIONS: Study patients (n = 58) were followed through the course of intubation and/or tracheostomy until they were extubated, left the hospital on ventilation, or died. MEASUREMENTS AND MAIN RESULTS: End-points for mortality and complications were determined. Overall mortality rate was 43% in the patients who required prolonged mechanical ventilation. Twenty-eight percent of the 58 patients died within the first 14 days. Of those patients who survived, 55% required an endotracheal tube only and were extubated in less than 14 days; 45% of the patients required tracheostomy. Of those patients who required tracheostomy, five (26%) were eventually extubated, seven (37%) remained mechanically ventilated, and seven (37%) died. The complication rate for endotracheal tubes was 65%; the complication rate for tracheostomy was 37%. CONCLUSIONS: Open-heart surgery patients requiring prolonged mechanical ventilation are a desperately ill subset of cardiac surgery patients. Those patients who survive are either extubated in less than 14 days or require prolonged mechanical ventilation beyond that point. In our opinion, patients should be given 1 wk to recover and one trial of weaning from the ventilator. If this approach fails, then they should undergo elective tracheostomy.     

Magnesium metabolism in open-heart surgery

The levels of magnesium in serum, urine and erythrocytes were studied in 22 patients undergoing cardiac surgery for valvular prosthesis. Magnesium values were correlated with serum albumin and non-esterified fatty acids (NEFA). Data were collected before anesthesia, 10 min after sternotomy, heparinization and declamping of the aorta and in the 1st postoperative day. A slight decrease in magnesemia was observed before extracorporeal circulation (ECC) and was mainly due to haemodilution. The correlation of magnesium with NEFA was significant only after heparinization. The use of the St Thomas solution as cardioplegia fully corrected the hypomagnesemia previously reported during ECC as well as in the 1st postoperative day. A moderate hypermagnesemia was observed at the end of ECC, but no patient reached dangerous levels of serum magnesium. Urinary losses increased during and after ECC. Red blood cell magnesium showed a slight increase before ECC, followed by a significant reduction at the end of ECC.     

Neuropathy in the upper extremity after open-heart surgery.

Eleven patients with upper-extremity neurological abnormalities underwent open-heart surgery performed through a median sternotomy incision. Seven of the 11 patients were referred in the routine manner to evaluate and treat the neurological problem. The remaining four were part of a consecutively studied group of 11 patients examined prospectively to determine the possible presence of abnormalities. Two of these four patients were asymptomatic. All lesions could be postulated to occur within the brachial plexus, the most common area being the median cord, but lesions were also noted in the posterior and lateral cords and upper trunk. The etiology of the problem appears to be stretching injury of the brachial plexus from retraction of the sternum, which in turn causes retroclavicular displacement of the clavicle. However, it is possible that an ischemic neuropathy could result from intraarterial procedures in some of our patients. The possibility that neurologic deficit may occur in the upper extremity should be considered by physicians who may have the opportunity to evaluate patients who undergo open-heart surgery.     

Studies of temperature balance after open-heart surgery.

An analysis of postoperative records over a two-year period has shown that a mean rise in central body temperature greater than 2 degrees occurs in patients within 12 hours of return from the operating room following open-heart surgery. In some patients the central body temperature may rise to greater than 41 degrees C. despite an adequately warm peripheral temperature, and this is associated with a high mortality rate. An apparatus has been developed which enables the immediate enviroment of the patient to be controlled. A comparison of two groups of patients, in one of which the apparatus was used, demonstrated that it was possible to attenuate significantly the usual postoperative temperature rise seen in the control group. In a third group further cooling was employed: these patients were successfully held at subnormal temperatures. Using multiple temperature probes and heat balance formulas, it was shown that the rise in central body heat was due mainly to elevation of total body heat rather than the result of redistribution of heat from the surface.     

Respiratory changes after open-heart surgery

Breathing pattern was studied non-invasively in 20 coronary artery bypass surgery patients before the operation and post-operatively after weaning from mechanical ventilation. Post-operatively minute ventilation (VE), breathing frequency (Fr) and mean inspiratory flow (VT/TI) increased (28%, 42%, 27%;p<0.01,p<0.001,p<0.01, respectively), while tidal volume (VT) decreased (15%,p<0.025). CO₂ production (VCO₂) and oxygen consumption (VO₂) increased postoperatively (p<0.001 for both), contributing to the increase in ventilatory demand. Reduced variation of VT and Fr (p<0.001,p<0.01, respectively) and number of sighs (p<0.001) were characteristic of the post-operative breathing pattern. Post-operatively an increase in the contribution of rib cage (%RC) to tidal volume in the supine position was observed suggesting reduced motion of the diaphragm. All patients had atelectasis, 17 had pleural fluid and only 6 normal vascularity post-operatively. The shallow breathing in combination with increased ventilatory demand, impaired gas exchange and the surgical trauma of the thorax predispose to postoperative respiratory complications.     

Plasma cortisol monitoring acute myocardial infarction.

A study of the concentration of unconjugated plasma cortisol in nine patients with acute myocardial infarction has been made. The effectiveness of monitoring this factor in assessment of the clinical course and establishing early treatment in this condition is also reported.     

Early postoperative delirium after open-heart cardiac surgery is associated with decreased bispectral EEG and increased cortisol and interleukin-6

Purpose  

It is difficult to substantiate the clinical diagnosis of postoperative delirium with objective parameters in intensive care units (ICU). The purpose of this study was to analyze (1) whether the bilateral bispectral (BIS) index, (2) cortisol as a stress marker, and (3) interleukin-6 as a marker of inflammation were different in delirious patients as compared to nondelirious ones after cardiac surgery.     

Plasma cortisol concentration in newborn infants

Plasma cortisol was measured in cord and neonatal blood. Cortisol concentration in neonates decreased rapidly during the first three days after delivery and thereafter remained at an almost constant level. The more the delivery was stressful, the higher the cortisol in the 1-day-old infant, but the concentration came down to the same level as in the less stressful delivery on the 3rd day of the infants' life. The cortisol level in vaginal delivery after spontaneous labor was not different from that in vaginal delivery after oxytocin induced labor. Cortisol in small-for-date infants or infants with hyperbilirubinemia was lower than in average-for-date infants or infants without hyperbilirubinemia.