J. Heinonen

Hydroxyethyl starch as a prime for cardiopulmonary bypass: effects of two different solutions on haemostasis

Hydroxyethyl starch (HES) is efficacious as a volume expander in cardiac surgical patients, but it may impair the haemostatic mechanisms. However, this latter effect may be less conspicuous with low molecular weight (LMW) solutions than with high molecular weight (HMW) solutions. Therefore, LMW– and HMW–HES solutions were evaluated as priming solutions for cardiopulmonary bypass (CPB) with respect to their effect on haemostasis. Forty–five patients undergoing coronary bypass grafting were prospectively randomised to three groups and in a double–blind manner as their CPB prime either 20 ml kg‐1 LMW–HES (Mw 120 000), 20 ml kg‐1 HMW–HES (Mw 400000) or Ringers acetate 2000 ml. The final volume of the prime was completed to 2000 ml with Ringers acetate in the HES groups. Anaesthesia and CPB management were standardised. Plasma levels of von Willebrand factor antigen and factor VIII procoagulant activity were significantly more depressed after CPB in both HES–groups as compared with the crystalloid prime group. In addition, APTT was more prolonged and the maximal amplitude of thromboelastographic tracing was more decreased in the HES–groups. It is concluded that it may be advisable to avoid HES solutions in the CPB prime, especially in patients with an increased risk for bleeding after cardiac operations.

Halothane-induced variability in the neuromuscular transmission of patients with myasthenia gravis

The purpose of the present clinical study was to explore the skeletal muscle mechano (MMG)‐ and electromyographic (EMG) responses during halothane/oxygen/air anaesthesia in patients with myasthenia gravis (MG) compared with patients with normal neuromuscular transmission. The majority of MG‐patients had a significant decremental response of the evoked muscle action potentials to a train‐of‐four (TOF) stimulation during halothane exposure (mean decrease of train‐of‐four ratio was 33% during the highest mean halothane concentration of 1.9 MAC). An excellent correlation was found between MMG‐ and EMG‐measurements (r2=0.878, P<0.001). However, marked individual variations in the neuromuscular response to halothane were seen. Neither preoperative muscle fatigability nor acetylcholine receptor antibodies predicted the decremental muscle responses produced by halothane among MG‐patients. The increased presence of HLA‐B8 among myasthenics with halothane‐suppressed muscle responses after TOF stimulation could be demonstrated (P<0.01).

Attenuation of Circulatory Response to Laryngoscopy and Tracheal Intubation: A Comparison of Two Methods of Topical Anaesthesia

Circulatory responses to laryngoscopy and endotracheal intubation were compared between throe groups of patients, two of which were subjected to a procedure of topical anaesthesia before induction of general anaesthesia. Topical anaesthesia, achieved with either a lidocaine dose aerosol or by gargling with viscous lidocaine, attenuated the magnitude of the pressor response to laryngoscopy and intubation but had no effect on the heart rate response. Lidocaine aerosol had some advantages over viscous lidocaine; these were the significantly smaller haemodynamic response to the local anaesthetic procedure itself and probably shorter duration of the circulatory changes produced by intubation. It is concluded that both of these simple methods are relatively ineffective in preventing haemodynamic changes associated with laryngoscopy and intubation and should probably be combined with another preventive method.

Heparin Rebound: A Comparative Study of Protamine Chloride and Protamine Sulfate in Patients Undergoing Coronary Artery Bypass Surgery

Heparin rebound has been suggested to occur when protamine sulfate, but not protamine chloride, is used to neutralize heparin. This study was undertaken to compare these two protamine salts in 32 patients undergoing coronary artery bypass surgery. Initial heparin and subsequent protamine doses were determined by constructing a heparin-activated coagulation time response curve. Heparin was neutralized either with protamine sulfate or protamine chloride. The total protamine/heparin dose ratio was 0.71 +/- 0.05 for protamine sulfate and 0.77 +/- 0.07 (mg/100 U) for protamine chloride. The initial neutralization effect, the subsequent behavior of the plasma heparin level, and the various coagulation parameters did not differ significantly between the groups. Two hours after neutralization, a small and temporary increase of plasma heparin level was observed in both groups. The postoperative blood losses were comparable in both groups. Thus, protamine chloride was not a clinically superior antidote to heparin than protamine sulfate. The observed heparin rebound levels were low and clinically insignificant in terms of blood loss, but they were associated with slight changes in coagulation monitoring.

Advantages of glycopyrrolate over atropine during reversal of pancuronium block.

Atropine 0.015 mg kg‐1 and glycopyrrolate 0.0075 mg kg‐1 were compared as antimuscarinic agents during reversal of pancuronium block with neostigmine 0.03 mg kg‐1 in 30 patients anaesthetized with thiopental—N2O‐fentanyl and undergoing minor surgery. The decrease of heart rate was more pronounced in patients who received atropine‐neostigmine. The mean of the lowest heart rate was 44.3 beats min‐1 in the atropine group compared with 54.3 beats min‐1 in the glycopyrrolate group. Five patients treated with atropine‐neostigmine developed a transient nodal rhythm as compared with two of those receiving glycopyrrolate‐neostigmine (non‐significant difference). Recovery from anaesthesia, as assessed by the awakening after the discontinuation of N2O administration, was more rapid in patients given glycopyrrolate. In conclusion, glycopyrrolate seems to have advantages over atropine when used during reversal of pancuronium block with neostigmine.

Hemodynamic effects of α-human atrial natriuretic peptide in healthy volunteers

The hemodynamic effects of synthetic alpha-human atrial natriuretic peptide (alpha-hANP) were evaluated in a double-blind, placebo-controlled study with echocardiography and systolic time intervals in 11 healthy volunteers. During an infusion of alpha-hANP for 30 min, when plasma ANP concentration increased to a peak level of approximately 300 pg/ml, an increase occurred in diuresis (+174%, p less than 0.01 vs. placebo) and natriuresis (+148%, p less than 0.05). Heart rate increased (+10%, p less than 0.05), but the mean arterial pressure remained unchanged. The left ventricular end-diastolic diameter was reduced (-3%, p less than 0.01), as was the left ventricular end-systolic diameter (-11%, p less than 0.001). Total peripheral resistance (-12%, p less than 0.05) and midsystolic circumferential wall stress (-16%, p less than 0.05) decreased, while cardiac output increased (+15%, p less than 0.05), as did fractional shortening (+15%, p less than 0.001). Within 30 min postinfusion, all differences between the ANP and placebo treatments had disappeared. No significant difference between the treatments was observed in preejection period or preejection period/left ventricular ejection time ratio. In conclusion, when administered as a short infusion, alpha-hANP causes peripheral arterial vasodilation and thus, by reducing left ventricular afterload, improves the pump function of the heart. Venous vasodilating effect of alpha-hANP may contribute to the decrease in left ventricular preload, but a diuresis-induced reduction in circulating intravascular volume may also be influenced.

Plasma atrial natriuretic peptide concentrations during induction of anesthesia and acute volume loading in patients undergoing cardiac surgery

Induction of anesthesia with fentanyl for coronary artery bypass grafting decreased (P less than .05) plasma atrial natriuretic peptide (ANP) concentrations from awake values in twelve patients. During a steady state of anesthesia before surgery, isotonic saline solution (10 mL/kg) was infused simultaneously with the elevation of the lower extremities in six patients, while six subjects served as controls receiving no volume loading and having no leg raising. The ANP levels returned to the awake values in the volume-loaded patients, while plasma ANP remained at anesthetized baseline levels in the control subjects (P less than .01 between the groups). Ten minutes after the end of the loading procedure, plasma ANP had begun to decrease again towards the postinduction level in the loaded group, but a significant (P less than .05) difference was still observed between the groups. These changes in ANP levels paralleled those of cardiac filling pressures. In conclusion, the results suggest that the degree of distention of the atria regulates the secretion of atrial natriuretic peptide into the circulation in patients anesthetized with fentanyl.

Hemodynamic responses to desmopressin acetate after CABG: A double-blind trial

Despite controversial results concerning its effectiveness, cardiac surgical patients commonly receive desmopressin acetate (DDAVP) after cardiopulmonary bypass (CPB) in an effort to prevent or control bleeding diathesis. The side effects associated with DDAVP are usually considered benign. However, numerous authors have observed episodes of severe hypotension after DDAVP. As a part of a larger trial of DDAVP in routine first-time coronary artery bypass grafting (CABG), this randomized double-blind study of the hemodynamic effects of DDAVP was performed. Fifteen patients received DDAVP (0.3 microgram/kg over 15 minutes) and another 15 received saline placebo after skin closure. A statistically significant decrease in mean arterial pressure (MAP) was observed at 5 minutes after the beginning of DDAVP administration and the maximum decrease (mean change, -21 +/- 8 mm Hg, P less than 0.001) was reached as the infusion was completed. MAP did not change significantly in the control group. Hypotension after DDAVP was associated with a corresponding decrease in systemic vascular resistance. Postoperative blood loss was not different between the groups. It is concluded that routine administration of DDAVP to CABG patients is inadvisable because hemodynamic side effects are potentially dangerous and therapeutic benefit is highly unlikely.

Increased pulmonary artery diastolicpulmonary wedge pressure gradient after cardiopulmonary bypass

In 29 patients undergoing elective coronary artery bypass grafting, the diastolic pulmonary arterial pressurepulmonary capillary wedge pressure gradient (DPAP-PCWP) and related haemodynamic parameters were determined before and after induction of anaesthesia, immediately after cardiopulmonary bypass (CPB) and one and three hours after CPB. The DPAP-PCWP gradient remained unchanged after induction of anaesthesia but was significantly increased after CPB. A gradient of 5 mmHg or greater was observed in 16 patients after CPB, whereas none of the patients showed such a gradient before CPB. A significant correlation was found between the change in DPAP-PCWP and the change in pulmonary vascular resistance (PVR). It is concluded that DPAP should not be used as a substitute of PCWP in the early postbypass period without frequent confirmation of the presence of the normal small DPAP-PCWP gradient. Since an increase of PVR may impair right ventricular ejection, we recommend the routine measurement of DPAP-PCWP gradient in the postbypass period.RésuméChez 29 patients subissant un pontage aorto-coronarien électif, le gradient entre la pression diastoliqiie de l’artère pulmonaire et la pression capillaire pulmonaire (DPAP-PCWP) ainsi que d’autres paramètres hémodynamiques ont été étudiés avant et après induction d’anesthésie, immédiatement après la circulation extracorporelle (CPB) et une heure et trois heures après la circulation extracorporelte. Le gradient DPAP-PCWP est resté inchangé après l’induction mais était significativement augmenté après circulation extracorporelle. Un gradient de 5 mmHg ou plus a été observé chez 16 patients après CEC alors qu’aucun des patients n’a démontré un tel gradient avant la CEC. Une corrélation significative a été trouvée entre le changement du DPAP-PCWP et le changement de la résistance vasculaire pulmonaire (PVR). On conclut que la DPAP ne doit pas être utilisée comme un substitut à la PCWP dans la période précoce après la CEC sans confirmation fréquente de la présence d’un gradient DPAP-PCWP normalement minime. Etantdonnéque l’augmentation de la résistance vasculaire pulmonaire PVR peut altérer la fraction d’éjection du ventricule droit, on recommande de routine la mesure du gradient DPAP-PCWP en période post-CEC.

Atria1 pressure and hormonal and renal responses to acute cardiac tamponade

The effect of acute cardiac tamponade on atrial pressures, plasma atrial natriuretic factor concentration and renin activity, and renal water and electrolyte excretion was studied in pigs loaded intravenously with hydroxyethyl starch and maintained on a continuous intravenous infusion of isotonic saline solution. Saline solution was infused into the pericardial space in 6 anesthetized pigs until a predetermined decrease of 20% in mean arterial pressure was achieved. Another 6 sham-treated pigs served as controls. Tamponade increased atrial intracavitary pressures but decreased atrial transmural (distending) pressures. These changes in atrial pressures were reversed after release of tamponade. Changes in plasma atrial natriuretic factor concentration correlated positively with changes in atrial transmural pressures. Tamponade increased plasma renin activity and decreased urine flow and renal sodium and potassium excretion, and release of tamponade reversed these changes. Thus, the tamponade-induced reduction in atrial distention is associated with hormonal changes, which may contribute to the reductions in diuresis and natriuresis observed in this connection.