Per-Olof Joachimsson

Early extubation after coronary artery surgery in efficiently rewarmed patients: A postoperative comparison of opioid anesthesia versus inhalational anesthesia and thoracic epidural analgesia

Twenty-eight patients were studied after uncomplicated aortocoronary bypass surgery with hypothermic cardiopulmonary bypass (CPB). In all patients residual hypothermia was effectively treated by the use of extended rewarming during CPB and postoperatively by an external heat source. This treatment almost eliminated postoperative shivering, and it resulted in the lowering of oxygen uptake, carbon dioxide production, and required ventilatory volumes to stable levels where spontaneous breathing could be used safely. The patients were divided into two groups. In group I (n = 12), intraoperative anesthesia was based on an intravenous (IV) opioid (phenoperidine), which caused persistent respiratory depression and made mechanical ventilation necessary for a mean postoperative time period of 10.7 +/- 3.8 hours even with the rewarming. In group II (n = 16), thoracic epidural analgesia and intraoperative general anesthesia with enflurane were used. In this group, postoperative metabolic and ventilatory requirements were stable and low, finger skin temperature was normalized earlier, systemic vascular resistance was lower, and stroke index was higher. Emergence from anesthesia was uneventful and was achieved early postoperatively in Group II. The patients had good pain relief and were mentally alert. Adequate spontaneous breathing was resumed quickly and endotracheal extubation was performed within the first two postoperative hours (1.6 +/- 0.5 hours). No complications or increased morbidity occurred, and no patient needed to be reintubated in Group II.

Thoracic epidural anesthesia does not influence the occurrence of postoperative sustained atrial fibrillation.

BACKGROUND To evaluate whether thoracic epidural anesthesia (TEA) can reduce the incidence of atrial fibrillation (AF) after coronary artery bypass grafting (CABG). METHODS Forty-one patients undergoing CABG were treated with TEA intraoperatively and postoperatively. Another 80 patients served as the control group. The sympathetic and parasympathetic activities were evaluated by analysis of neuropeptides, catecholamines and heart rate variability (HRV), preoperatively and postoperatively. RESULTS Postoperative AF occurred in 31.7% of the TEA-treated patients and in 36.3% of the untreated patients (p = 0.77). TEA significantly suppressed sympathetic activity, as indicated by a less pronounced increase of norepinephrine and epinephrine (p = 0.03, p = 0.02) and a significant decrease of neuropeptide Y (p = 0.01) postoperatively in TEA-treated patients compared to untreated patients. The HRV variable expressing sympathetic activity was significantly lower and the postoperative increase in heart rate was significantly less in the TEA group than in the control group after surgery (p = 0.01, p < 0.001). Among patients developing AF, the maximal number of supraventricular premature beats per minute increased significantly in untreated patients postoperatively but remained unchanged in TEA-treated patients (p = 0.004 versus p = 0.86). CONCLUSIONS TEA has no effect on the incidence of postoperative sustained AF, despite a significant reduction in sympathetic activity.

Postoperative analgesia and sedation following pediatric cardiac surgery using a constant infusion of ketamine

Constant rate infusions of ketamine supplemented with intermittent doses of midazolam were given postoperatively to 10 children in order to provide analgesia and sedation during mechanical ventilation after cardiac surgery as well as during weaning from the ventilator and during spontaneous breathing. The aims of the study were to determine the pharmacokinetics of ketamine and evaluate the suitability of ketamine as an analgesic and sedative in postoperative pediatric cardiac patients. The children were between one week and 30 months old. Five children were given 1 mg/kg/h of ketamine and five children had 2 mg/kg/h. Blood was sampled during infusion and up to 24 hours after infusion for plasma concentrations of ketamine and the main plasma metabolite, norketamine, which were determined by gas chromatography and were compared to the degree of sedation. The children were arousable when ketamine concentrations were below 1.0 to 1.5 micrograms/mL. Plasma ketamine concentrations at steady state were within a narrow range for each infusion regimen and the calculated pharmacokinetic parameters were similar. Mean plasma clearance of ketamine was 0.94 +/- 0.22 L/kg/h. The elimination half-life was 3.1 +/- 1.6 hours, but in some children late samples indicated an even longer elimination half-life. Norketamine did not reach a steady state, but at the end of the infusion, the mean plasma concentration was higher than that of ketamine. The elimination half-life of norketamine was estimated to be 6.0 +/- 1.8 hours. Both ketamine infusion regimens were supplemented with midazolam and provided similarly acceptable analgesia and sedation during mechanical ventilation and during and after weaning from the ventilator.(ABSTRACT TRUNCATED AT 250 WORDS)

Thoracic epidural anesthesia as an adjunct to general anesthesia for cardiac surgery: Effects on ventilation-perfusion relationships

OBJECTIVE To determine the effects of thoracic epidural anesthesia (TEA) on ventilation-perfusion (VA/Q) relationships, atelectasis, and oxygenation before and after coronary artery bypass graft surgery (CABG). DESIGN Prospective, controlled, unblinded, randomized trial. SETTING Cardiothoracic clinic at a major university referral center. PARTICIPANTS Twenty-eight patients undergoing elective CABG. INTERVENTIONS Perioperative and postoperative TEA was added to general anesthesia (GA) in 14 patients, and 14 patients receiving GA alone served as controls. MEASUREMENTS AND MAIN RESULTS VA/Q relationships were measured by the multiple inert gas elimination technique, and, 20 hours postoperatively, atelectasis was assessed by computerized tomographic scans. Arterial and mixed venous blood gases and hemodynamic variables were measured by standard techniques. TEA per se caused no change in shunt, VA/Q matching, or oxygenation. Induction of GA in the control group and induction of TEA caused similar reductions in mean arterial pressure. The TEA patients needed less morphine analgesia postoperatively and were extubated earlier. Extubation caused significant improvement in VA/Q matching. On the first postoperative day, a slight reduction in PaCO2 was seen in the TEA group, but no differences in shunt, VA/Q matching, or oxygenation compared with the GA group. Both groups showed extensive bilateral atelectasis. CONCLUSION TEA can reduce respirator time and the need for morphine analgesics after CABG without negative effects on VA/Q matching, oxygenation, or atelectasis formation.

Postoperative ventilatory and circulatory effects of extended rewarming during cardiopulmonary bypass

Postoperative effects of extended rewarming (ECR) after hypothermic cardiopulmonary bypass (CPB) were studied. All (n = 28) patients were rewarmed to a nasopharyngeal temperature exceeding 38° C before terminating CPB. In 12 patients (control group) the rectal temperature (Tre) was 33.8 ± 1.7° C (mean ± sd) at termination of CPB. In sixteen patients (ECR group) rewarming during CPB was continued to a Tre of 36.8 ±0.5°C. Postoperative body temperatures, heat content, shivering, oxygen uptake, CO2 production and haemodynamic variables were measured. ECR reduced the heat gain required to complete core rewarming to 665 ± 260 kJ, compared with 1037 ± 374 kJ in the control group (p < 0.01). The incidence of shivering was reduced (p < 0.05) as well as shivering intensity and duration. In seven non-shivering ECR group patients this coincided with significantly reduced metabolic and ventilatory demands but these improvements were not valid for the group as a whole. The required ventilation temporarily during postoperative rewarming in both groups increased to 250 per cent of the basal need. Extending CPB rewarming (to at least 36°C Tre) was inefficient when used as the sole measure to reduce the untoward effects of residual hypothermia during recovery after cardiac surgery with hypothermic CPB.RésuméEtude des effets postopératoire du réchauffement prolongé (ECR) après une opération faite avec circulation extracorporelle (CEC) et hypothermie. On a réchauffé tous les malades (n = 28) jusqu’à ce que la température du nasopharynx ait dépassé 38° C avant ta fin de la période en CEC. Douze malades (groupe de contrôle) ont eu une température rectale (Tre) de 33.8 ± 1.7° C (moyenne ± sd) à la fin de la période en CEC. Durant le CEC on a réchauffé seize malades (groupe dénommé ECR) jusqu’à ce que leur Tre soit montée à 36.8 ± 0.5° C. Après ľopération on a mesuré les températures en diverses places du corps, la quantité du chaluer, ľhyperactivité musculaire, le degré ďoxygène, la production de CO2 et les différentes phases de ľhaemodynamique. Le procédé par ECR a réduit le besoin de chaleur nécessaire pour le réchauffement central à 665 ± 260 kJ. A comparer aux 1037 ± 374 kJ dans le groupe de contrôle (p < 0.01). La manifestation de ľhyperactivité musculaire a été réduite (p < 0.05) aussi bien que son intensité et sa durée. Chez sept malades du groupe ECR ľabsence ďhyperactivité musculaire a coincïdé avec une réduction significative au point de vue du métabolisme et de la ventilation mais ce genre ďamélioration n’est pas valable pour le groupe pris dans son ensemble. Après ľopération, le débit ventilatoire dans la période de réchauffement a augmenté dans les deux groupes de 250 pour cent au-dessus du niveau de base. Prolonger le réchauffement en CEC jusqu’à atteindre au moins 36° C rectal n’apas été une méthode efficace si on ľemploie seule pour réduire après ľopération les effets indésirables de ľhypothermie pratiquée en CEC.

Heating efficacy of external heat supply during and after open-heart surgery with hypothermia

Heat balance after cardiac surgery with hypothermic cardiopulmonary bypass (CPB) was studied in 156 patients. In spite of rewarming during CPB there was residual hypothermia at the end of operation. This heat deficit could not be prevented by intraoperative use of a heating mattress at 38°C and/or heated (39°C) humidified inspired gases. Postoperatively, in four groups of patients, the core and finger skin temperatures were recorded and the mean skin and mean body temperatures and heat balance were calculated. Heating of humidified inspired gases (n = 22) gave little improvement in the time course of the temperatures and heat balance as compared with that in a control group with no external warming postoperatively (n = 49). A thermal ceiling (a low‐temperature radiator suspended above the bed and providing radiant heat (n = 35)) significantly increased the measured temperatures, which were restored to normal earlier than those in the controls. Also, with this radiant heat postoperative shivering was almost abolished. With a combination of radiant heat and heated, humidified gases (n = 50), the postoperative heat balance was improved somewhat further. For patients treated with radiant heat, postoperative rewarming was accomplished in a shorter time and almost without active endogenous muscular thermogenesis, as was evident by the great reduction in postoperative shivering.

Prevention of intraoperative hypothermia during abdominal surgery

Heat balance and core and skin temperatures were studied in 111 patients during abdominal surgery. In minor surgical procedures the effects of heating of inspired humidified gases (n = 23) and of a heating mattress (n = 21) were compared with the conditions in an unwarmed control group (n = 24). These two methods were about equally effective in preserving total body heat, although the major effect of the heating mattress was to conserve heat which had been redistributed to the surface, and such heat could subsequently he lost to the environment. During major abdominal surgery 18 unwarmed control patients were compared with patients (n = 25) provided with a heat supply. The combined measures of heated humidified inspired gases, a heating mattress, insulation by a heat‐reflecting blanket, warming of all infusions and transfusions arid a warm operating room were all needed to balance the great heat losses during the major surgical procedures. With such massive heat supply it was possible to prevent heat loss and a fall in core temperature.

Postoperative ventilatory and circulatory effects of heating after aortocoronary bypass surgery

Twenty‐four patients with stable angina pectoris were studied after aortocoronary bypass surgery with hypothermic cardiopulmonary bypass (CPB). Twelve patients (radiant heat supply group) were rewarmed during CPB to a nasopharyngeal temperature of at least 38°C and a mean rectal temperature of 34.4°C. Postoperatively they received radiant heat supply from a thermal ceiling. In addition, a heating water mattress was used during the end of the operation and heated, humidified inspired gases were administered intra‐ and postoperatively. The other 12 patients (combination heat supply group) had the rewarming during CPB extended until the rectal temperature exceeded 36°C, but otherwise received the same treatment as the radiant heat supply group. The combination of extended rewarming during CPB and postoperative radiant heat supply significantly reduced oxygen uptake, carbon dioxide production and the required ventilation volumes during early recovery as compared with the values in the radiant heat supply group. The reduced metabolic demands were accompanied by lower cardiac index and oxygen delivery, which, however, were sufficient for adequate tissue perfusion as judged by the similarity in oxygen extraction and arterial base excess values in the two groups. The metabolic demands and ventilatory requirements were reduced to a level at which safe early extubation is possible.

Influence of β1-blockade on myocardial substrates early after a coronary operation☆

A high adrenergic strain during reperfusion after ischemia impedes functional recovery. Conversely, adrenergic blockade may be beneficial during reperfusion. This study was undertaken to find out if early postoperative high-dose infusion of the selective beta 1-blocking agent metoprolol tartrate has additional effects on metabolic variables related to myocardial energy supply/demand balance compared with those obtained with a late preoperative oral dose. The study included 21 male patients undergoing coronary bypass grafting. All patients received an oral dose of metoprolol before the operation. After the operation, patients were randomized to a control group or a group receiving intravenous infusion of metoprolol. Myocardial uptake of oxygen and substrates was determined before and during atrial pacing. Metoprolol reduced arterial concentrations of free fatty acids, reduced myocardial uptake of free fatty acids, and enhanced myocardial uptake of lactate. During paced tachycardia, the metoprolol concentration correlated negatively with myocardial uptake of free fatty acids (r = -0.80; p < 0.001) and positively with myocardial uptake of lactate (r = 0.53; p < 0.05). It is concluded that postoperative infusion of metoprolol induces myocardial metabolic changes compatible with an improved energy supply/demand balance.

CONTINUOUS VECTORCARDIOGRAPHY IN CARDIAC SURGERY: NATURAL COURSE OF VECTOR CHANGES AND RELATIONSHIP TO MYOCARDIAL OXYGEN UPTAKE

Continuous vectorcardiography was registered before and during the first 18 hours after cardiac surgery in 53 patients. QRS vector changes (QRS-VD) occurred during the operation, but no further changes were observed postoperatively. The ST vector (ST-VM) increased during the operation, and a further slight increase occurred postoperatively. Perioperative myocardial infarction occurred in three patients. Their ST-VM was higher than the average in patients without myocardial infarction, while QRS-VD did not differ from the average pattern. Twelve other patients were studied in pacemaker-induced moderate tachycardia. QRS-VD increased in proportion to heart-rate changes (rs median = 0.93, p less than 0.01). QRS-VD also correlated with myocardial oxygen uptake (rs median = 0.62, p less than 0.05). The ST-VM responses were not uniform. The data suggest that vectorcardiogram variables can provide information related to myocardial energy metabolism.