Perioperative care of diabetic patients:

The key role of pulse wave transit time to predict blood pressure variation during anaesthesia induction

OBJECTIVE

To establish the relationship between pulse wave transit time (PWTT) before anaesthesia induction and blood pressure variability (BPV) during anaesthesia induction.

METHODS

This prospective observational cohort study enrolled consecutive patients that underwent elective surgery. Invasive arterial pressure, electrocardiography, pulse oximetry, heart rate and bispectral index were monitored. PWTT and BPV were measured with special software. Anaesthesia was induced with propofol, sufentanil and rocuronium.

RESULTS

A total of 54 patients were included in this study. There was no correlation between BPV and the dose of propofol, sufentanil and rocuronium during anaesthesia induction. Bivariate linear regression analysis demonstrated that PWTT (r = -0.54), age (r = 0.34) and systolic blood pressure (r = 0.31) significantly correlated with systolic blood pressure variability (SBPV). Only PWTT (r = -0.38) was significantly correlated with diastolic blood pressure variability (DBPV). Patients were stratified into high PWTT and low PWTT groups according to the mean PWTT value (96.8 ± 17.2 ms). Compared with the high PWTT group, the SBPV of the low PWTT group increased significantly by 3.4%. The DBPV of the low PWTT group increased significantly by 2.1% compared with the high PWTT group.

CONCLUSIONS

PWTT, assessed before anaesthesia induction, may be an effective predictor of haemodynamic fluctuations during anaesthesia induction.

Glycemic control in non-diabetic critically ill patients

Hyperglycemia is a common and costly health care problem in hospitalized patients. In hospital hyperglycemia is defined as any glucose value >7.8 mmol/l (140 mg/dl). Hyperglycemia is present in 40% of critically ill patients and in up to 80% of patients after cardiac surgery, with ∼ 80% of ICU patients with hyperglycemia having no history of diabetes prior to admission. The risk of hospital complications relates to the severity of hyperglycemia, with a higher risk observed in patients without a history of diabetes compared to those with known diabetes. Improvement in glycemic control reduces hospital complications and mortality; however, the ideal glycemic target has not been determined. A target glucose level between 7.8 and 10.0 mmol/l (140 and 180 mg/dl) is recommended for the majority of ICU patients. This review aims to present updated recommendations for the inpatient management of hyperglycemia in critically ill patients with and without a history of diabetes.

Spinal anesthesia with 3.75 mg of 0.25% hyperbaric bupivacaine for diabetic foot surgery

BACKGROUND

Spinal anesthesia in the sitting position with low-dose local anesthetics usually provides satisfactory anesthesia for diabetic foot surgery because most operations do not require tourniquet application. This study was designed to investigate the influence of different sitting periods after subarachnoid injection of low dose bupivacaine on the spread of analgesia.

METHODS

In this randomized, controlled clinical trial, 60 patients undergoing diabetic foot surgery under spinal anesthesia without a tourniquet were randomized to three groups. Patients remained sitting for 2 (Group D2, n = 20), 5 (Group D5, n = 20), or 10 (Group D10, n = 20) min after the completion of subarachnoid administration of 3.75 mg of 0.25% hyperbaric bupivacaine solution. They were then placed in the supine position. Analgesia levels were assessed bilaterally using pinpricks. Blood pressure and heart rate were also recorded.

RESULTS

The maximal sensory block level [median (range)] was higher in Group D2 [L3 (L2-L3)] compared with Group D10 [L4 (L3-L4)] (P = 0.002). The highest sensory block levels were T12, T11, and L2 in Group D2, 5 and 10, respectively. There were no hemodynamic differences among the three groups and none of the patients showed hemodynamic instability except for one patient in Group D10.

CONCLUSIONS

Although spinal anesthesia using a minimal dose of 0.25% hyperbaric bupivacaine provides adequate anesthesia for diabetic foot surgery without profound hypotension, regardless of the time spent in the sitting position, maintaining the position for 10 min required to confine the sensory blockade on the lower level.

Glycemic control and prevention of perioperative infection

PURPOSE OF REVIEW

Hyperglycemia is common during perioperative management of surgical and critically ill patients. There is extensive ongoing study of detrimental effects associated with hyperglycemia, with several remaining unanswered questions. This review discusses recent literature on tight glucose control with insulin therapy and its effects in prevention and management of infection.

RECENT FINDINGS

Hyperglycemia affects multiple pathways of the immune system, resulting in decreased phagocytic and chemotactic functions in neutrophils and monocytes, as well as increased rates of apoptosis of the former and decreased ability of the latter to present antigen. Intensive insulin therapy has been shown to counteract many of these deleterious effects. Clinically, the benefits of tight glucose control have been evaluated in different patient populations with conclusions that remain varied. Hypoglycemia as a complication of tight glucose control continues to be an issue and has led to discontinuation of two large-scale studies. The clinical relevance of hypoglycemic events remains unclear.

SUMMARY

Hyperglycemia impairs the cellular immune system, stimulates inflammatory cytokines, and affects the microcirculation, thus increasing risk for infection and preventing normal wound healing. Additional investigation is needed to define appropriate patient populations and to develop effective treatment strategies for preventing perioperative morbidity.

Perioperative glucose control in the diabetic or nondiabetic patient

Patients with diabetes are more likely to undergo surgery than nondiabetics, and maintaining glycemic control in subjects with diabetes can be challenging during the perioperative period. Surgery in diabetic patients is associated with longer hospital stay, higher health care resource utilization, and greater perioperative mortality. In addition, several observational and interventional studies have indicated that hyperglycemia is associated with adverse clinical outcomes in surgical and critically ill patients. This paper reviews the pathophysiology of hyperglycemia during trauma and surgical stress and will provide practical recommendations for the preoperative, intraoperative, and postoperative care of diabetic patients.

Präoperative Bestimmung der Herzfrequenzvariabilität bei Diabetikern zur Einschätzung des Blutdruckverhaltens während der Anästhesieeinleitung

BACKGROUND

In diabetics severe hyopotension can occur during anaesthesia as a consequence of cardiovascular autonomic neuropathy (CAN). A simple approach to recognize CAN is heart rate variability (HRV) measured at rest. The aim of this study was to determine the relationship between pre-operatively measured HRV and blood pressure stability during induction phase of anaesthesia.

PATIENTS AND METHODS

A total of 35 diabetics undergoing an ophthalmosurgical procedure under general anaesthesia were investigated. HRV was examined one day before surgery by the following parameters: coefficient of variation (CV), root mean squared successive difference (RMSSD), and power spectrum. Anaesthesia was induced with thiopental and fentanyl and maintained with enflurane/N(2)O; tracheal intubation was performed after relaxation with vecuronium. Patients who developed a drop in systolic blood pressure below 90 mmHg during anaesthesia induction were assigned to group H (hypotensive), the other patients to group N (normotensive). The groups were compared regarding HRV and other variables.

RESULTS

Of all patients 13 developed hypotension during anaesthesia induction (group H). The groups were comparable regarding the demographic data. Parameters of HRV, with the exception of spectral power in low frequency (LF) band of power spectrum, were significantly lower in group H. The groups differed mainly in relation to spectral power in the mid-frequency (MF) band of the power spectrum, and especially regarding CV. In patients with normal CV incidence of hypotension after anaesthesia induction was 11%, but in patients with abnormally reduced CV, 65% (p=0.002).

CONCLUSION

The results confirm a significant relationship between HRV pre-operatively measured at rest and blood pressure stability during anaesthesia induction in diabetics. Particularly examination of CV, a simple test feasible within few minutes, may be useful in pre-operative risk stratification of these patients. Application of the time consuming traditional test combination to identify CAN seems to be unnecessary.